Method for testing the integrity of virus filtration modules and a filtration apparatus for carrying out the method

Abstract

The disclosure relates to a method for testing the integrity of one or more virus filtration modules and to a filtration apparatus for carrying out the method, by means of which the step of detecting whether an intact virus filtration module is present or not can be carried out in a fully automated manner for the first time. Multiple virus filtration modules can be tested in parallel at the same time, thus resulting in a distinct time saving when testing. The automation of detection allows reliable testing, the test results being reproducible and the risk of damage to the hollow fibers by the testing being reduced to a minimum. The integrity test can be carried out in the very same filtration apparatus in which virus filtration is also performable between the integrity tests using the tested virus filtration modules, without any need for the virus filtration module(s) to be fitted into or removed from a separate test system each time.

Description

[0001] Method for testing the integrity of virus filtration modules and a filtration device for carrying out the method

[0002] BACKGROUND OF THE INVENTION

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method for testing the integrity of virus filtration modules and a filtration device for carrying out the method.

[0005] STATE OF THE ART

[0006] Filters are of great importance for a wide variety of technical applications. For example, so-called sterile filters are used in the aseptic production of pharmaceuticals or medical products to prevent contamination by, for example, germs or particles by separating them out. For years, it has been common practice according to GMP (Good Manufacturing Practice) guidelines and regulations of the EMA (European Medicines Agency) and the FDA (US Food and Drug Administration) to test filters for their integrity before and / or after use (“postuse filter integrity” and “preuse filter integrity”). The integrity test represents a functional test of the filter, which is intended to prove that the filter was or is fully functional and therefore intact, i.e. that it does not allow any unwanted components to pass through. Common integrity tests are destructive or non-destructive.Non-destructive integrity tests are regularly preferred because they are more advantageous for economic reasons.

[0007] Non-destructive integrity tests known in the pharmaceutical sector include the bubble point test, the diffusion test (forward flow test and pressure hold test) and the water flow test. In each case, the manufacturer's guidelines for the filters can be used as a reference to check whether the filters are actually functioning.

[0008] Membrane filters are used in biotechnology, pharmaceuticals, and food technology, for example. The separation process is purely mechanical, using the filter membrane. It does not require heating like conventional separation methods, such as distillation, and therefore represents a gentle separation. Membranes also enable separations that cannot be achieved with conventional thermal separation methods. Furthermore, there is no damage to the components being separated, for example, due to thermal effects.

[0009] Particularly in biopharmaceutical manufacturing processes and in light of the global COVID pandemic, the removal of viruses using filter membranes has gained increasing importance. The presence of viruses, for example in pharmaceuticals and medical devices, poses a significant risk of viral infection to a patient, possibly even with the potential danger of spreading the infection. Virus filters are known to be used for this purpose, which are capable of completely separating and thus removing viruses from a batch.

[0010] Typical virus filters are composite membranes, which can be made of multiple materials. For example, a support structure made of fibers and a fine-pored polymer support layer are combined with an extremely thin, pore-free separation layer. Virus filters are usually virus-retention filters in the form of ultrafilters or microfilters, which have very small and additionally defined pore sizes. Filters are differentiated according to the size of the viruses to be removed. For example, there are known retrovirus filters, where the diameter of a retrovirus is approximately 80 to 100 nm, and parvovirus filters, where parvoviruses have a diameter of approximately 18 to 26 nm.

[0011] Other well-known virus filters are so-called hollow-fiber filters, which consist of a bundle of fine tubes with small pores. These hollow-fiber filters are used for the filtration of liquids and typically have two inlets and two outlets. Virus removal is based on a combination of size exclusion and depth filtration mechanisms, with viruses larger than the average pore size being retained by the hollow fibers. Such hollow-fiber filters are used, for example, for virus removal from pharmaceuticals, such as biopharmaceuticals, and plasma derivatives.

[0012] For a better understanding, the hollow fiber filters and their function are first explained using figures, before the method known from the state of the art for testing the integrity of hollow fiber filters is described:

[0013] Fig. 1 shows a schematically simplified view of a hollow fiber filter module 10 without a housing that usually surrounds the filter module 10, so that the hollow fibers can be seen inside the filter module 10. In detail, a bundle 50 of hollow fibers is shown, which is composed of a plurality of hollow fibers 50.1, 50.2, .... The hollow fibers 50.1, 50.2, .... are hollow in the inner region 35, also referred to as the hollow fiber interior, and are in the form of membrane tubes with small diameters that are arranged essentially parallel to one another. The hollow fibers 50.1 and 50.2 have a lower end 20, to which liquid is supplied (so-called feed, arrow A), and an upper end 30, at which rinsing solution exits the hollow fibers 50.1 and 50.2 only during a rinsing process of the filter module 10 (arrow B), but no liquid exits during filtration. The wall 40 of the hollow fibers 50.1, 50.2, ...each has pores (not shown) so that liquid passes through the wall 40 of each of the hollow fibers 50.1, 50.2, ... (arrow C). The hollow fiber walls therefore act as a filter. The components retained in the inner region 35 or on the inside or lumen of the hollow fibers 50.1, 50.2, ... are also referred to as retentate; the filtered liquid passing through the walls of the hollow fibers 50.1, 50.2, ... is also referred to as filtrate. The hollow fiber filter module 10 therefore has a feed side 55, a retentate side 65 and a filtrate side 75. The feed side 55 leads to the inner side or inner region 35 of each hollow fiber. Between the hollow fibers 50.1, 50.2... there are gaps 38.1, 38.2.

[0014] Fig. 2 shows a schematic enlarged sectional view of a hollow fiber 50.1, which is present in the hollow fiber filter module 10 shown in Fig. 1 as part of the hollow fiber bundle 50. If, for example, a protein solution on the feed side 55 with viruses 100.1, 100.2, ... is introduced as contamination into the interior 35 of the hollow fiber 50.1 - as symbolized by arrow A - the protein solution penetrates the pores (e.g. pore 45) of the membrane wall 40 on the filtrate side 75 to the outside, as symbolized by the arrows C (downward and upward). The pores in the wall 40 of the hollow fiber 50.1 are symbolized in Fig. 2 by the dashed lines. The dense pore structure of the hollow fiber wall 40, for example, is several dozen micrometers thick and represents a kind of winding, three-dimensional network of interconnected cavities and capillary pores. The viruses 100.1, 100.2,...are effectively retained by the net-like pore structure in the hollow fiber wall 40, while the now virus-free protein solution with the proteins migrates outward through the hollow fiber wall 40 and is retained on the filtrate side 75 (arrows C). At arrow B, no liquid escapes during filtration (symbolized by the crossed-out arrow B); liquid only escapes during a rinsing process in the integrity test, as will be explained below.

[0015] The separation of viruses therefore only works if the hollow fiber filter module is fully functional and the hollow fibers are intact and free from damage of any kind. Tests have been developed to determine whether the filter is intact. These are so-called integrity tests, i.e. tests that make it possible to determine whether the hollow fibers present are undamaged and functioning within the desired range. This integrity test of the virus filter function, as well as other integrity tests not described here, are a prerequisite for the release of a filtered product after virus filtration is complete. A further prerequisite for release for virus filtration is a gold particle (GPT) test, also an integrity test for a hollow fiber filter, which serves to confirm the filter quality (pore size distribution) after filtration.The GPT test plays no role here and is not the subject of the present invention, which is why it will not be discussed in more detail here.

[0016] The integrity test of interest determines whether the hollow fibers of the filter module are undamaged. The test of the hollow fiber filter module is performed before use to ensure that the filter module is suitable for use and functions properly. In addition, a further integrity test is performed after use of the filter module, i.e., after virus filtration, to ensure that it was not damaged during filtration, for example, due to overpressure or mechanical stress. The integrity test, as known from the prior art, is essentially performed as follows:

[0017] A hollow fiber filter module 10 typically has two inlets and two outlets. This is illustrated by way of example in Figure 3a. Figure 3a shows a schematically enlarged front view of a virus filtration module in the form of a hollow fiber filter module 10 with connected lines. Two inlets are shown at 55 and 65, as well as two outlets at 75o and 75u. However, for the integrity test, usually only one inlet, for example at 55, and one outlet, for example at 75o, are used, to each of which the lines shown are connected. The outlet at 75o in the filter module 10 may have advantages for procedural reasons, for example due to a short distance to the assigned connection. The further inlet at 65 and the further outlet at 75u are or will be closed. The 2 inputs at 55 and 65 in filter module 10 are completely equivalent, so it does not matter which of the two inputs is selected.This also applies to the outputs, which are both completely equivalent. In Fig. 3a, the inlet at 65°C and the outlet at 75°C could therefore also be selected for the integrity test, and the inlet at 55°C and the outlet at 75°C could be closed. In the integrity test known in the art (see "TAS 33088, Integrity Test Procedure Planova™ 15N, 20N, 35N and 75N Filters, Visual Leakage Test (VLT)", Version 1.1 dated February 25, 2019; the procedure is available for download from the Asahi Kasai website after registration), the hollow fiber filter module 10 to be tested is first placed in a vertical position and filled with liquid under positive pressure. Then, air is injected under pressure into the line on the inlet side at 55°C (feed side) of the filter module 10. For this purpose, the lines on the input side at 55 and the output side at 75o of the filter module 10 are opened for the test setup and the other lines orTheir connections (at 65 and 75°C) are or are already closed. The pressure is kept constant throughout the test. A visual inspection is then performed throughout the test to determine whether a continuous chain of air bubbles is detected in the line on the outlet side at 75°C. If a chain of air bubbles is detected, this indicates that the hollow fiber filter module 10 is damaged and is not functioning as intended.

[0018] The relationships that play a role in carrying out the integrity test on a hollow fiber in a virus filtration module are illustrated in detail below using Figures 3b and 3c for better understanding:

[0019] Fig. 3b shows a schematic and simplified enlarged sectional view of an intact hollow fiber 50.1a. The hollow fiber 50.1a is part of a hollow fiber bundle 50 as illustrated in Fig. 1, which is located with other hollow fibers in a housing (not shown). The hollow fiber filter module was already completely filled with liquid in accordance with the integrity test to be carried out, so that liquid is present throughout the entire filter module - i.e. in the hollow fibers and in the spaces between the hollow fibers - as well as in all lines leading to and from the filter module. In Fig. 3b, there is therefore liquid in the inner region 35 of the hollow fiber 50.1a and also outside the wall 40 of the hollow fiber 50.1a in the space between the hollow fibers. The volume of liquid present is limited by the type and size of the hollow fiber filter module and its housing, as well as the lines present.

[0020] As can be seen from Fig. 3b, air 80 is fed under pressure from the feed side 55 into the inner region 35 or the inner side of the hollow fiber 50.1a (arrow A). In Fig. 3b, the hollow fiber 50.1a shown is intact and shows no damage. In this case, the air 80 introduced from the feed side 55 passes through the hollow fiber 50.1a and only a very small amount of air passes through the membrane. This small amount is also referred to as the "creep amount" and will be explained in more detail later. The air 80 therefore does not leave the interior 35 of the hollow fiber 50.1a because the air 80 cannot pass through the pores in the wall 40 of the hollow fiber 50.1a, but is retained in the interior 35 together with the existing liquid. The pores in the wall 40 of the hollow fiber 50.1a are symbolized by the dashed lines in Fig. 3b. Thus, virtually no supplied air 80 escapes from the hollow fiber 50 on the filtrate side 75 (arrows C).1 a. The hollow fiber 50.1 a of Fig. 3b is therefore an intact hollow fiber 50.1 a, which would also pass the integrity test. Unlike in Fig. 3b, a damaged hollow fiber 50.1 b is shown schematically and simplified in an enlarged sectional view in Fig. 3c. There is damage 90 in the wall 40 of the hollow fiber 50.1 b. The damage 90 shown represents, for example, a crack or other impairment of the pore structure of the hollow fiber wall 40. As a result, the introduced air 80 cannot be retained in the interior 35 of the hollow fiber 50.1 b, but escapes on the filtrate side 75 through the wall 40 of the hollow fiber 50.1 b to the outside. The appearance of a chain of air bubbles in the filtrate would therefore indicate damage to the hollow fiber 50.1 b, which can then no longer be used. If a hollow fiber 50.1 b damaged in this way.If 1 b were used for virus filtration, the potentially present viruses would also no longer be retained inside 35 of the hollow fiber 50.1 b, and would escape through the damage 90 and continue to contaminate the product being cleaned. A reliable separation of viruses would no longer be possible.

[0021] Due to the undesirable escape of air through the hollow fiber wall and the assessment of the presence of a chain of air bubbles through visual inspection, the test is also referred to as a "visual leak test." This test is performed on a virus filter before filtration (pre-visual leak test) and after filtration (post-visual leak test). A visual leak test or integrity test is only considered passed if no continuous chain of air bubbles is detected for a duration of at least 20 seconds over the entire test period.

[0022] The general procedure and test parameters of the integrity test were designed by Asahi Kasai and include the test setup, in which air flows through a hollow fiber module at a defined pressure and potential damage caused by a continuous chain of air bubbles at the outlet of the filter module is detected through a manual and purely visual inspection by one or more employees (see "TAS 33088, Integrity Test Procedure Planova™ 15N, 20N, 35N and 75N Filters, Visual Leakage Test (VLT)", Version 1.1 dated February 25, 2019; the procedure is available for download from the Asahi Kasai website after registration).

[0023] The well-known integrity test, as described above, has a number of serious disadvantages:

[0024] A disadvantage of the known integrity test is that the hollow fiber filter modules used to separate viruses are extremely sensitive and, if handled improperly, are easily damaged, thus impairing their functionality. This is particularly problematic in the test setup for the integrity test, when the hollow fiber filter modules must be repeatedly installed and removed from the test device to test their integrity before and after virus filtration. A further problem arises if unsuitable or incorrect test parameters are selected for the test, which could impair the filter. These are each potential risks for possible damage to the hollow fiber filter modules.If damage is detected after virus filtration, it is always difficult to determine retrospectively whether the damage already existed before filtration, occurred during filtration, or was caused by the integrity test after filtration. However, sterility, especially virus-freeness, is absolutely essential in specific technical areas, such as biopharmaceutical purification processes.

[0025] Another problem is that the visual inspection to determine whether and to what length the air bubbles appear, indicating a possible defect in the hollow fibers, is carried out by production employees. This represents a subjective assessment of the test, whereby the determination and detectability of a chain of air bubbles is not clearly defined and is therefore not subject to clear, measurable acceptance criteria. For example, one observer may see a continuous chain of air bubbles lasting at least 20 seconds, while another observer sees or interprets it differently. The results therefore depend on the respective observer and are not objective. Even if several independent observers carry out the visual inspection, this does not really improve the results, as human error in the setup and execution of the test cannot be ruled out. In fact, this would only tie up more employee capacity for one test.In addition, test results are often not reproducible when repeated. Furthermore, the test procedure and the results cannot be recorded; instead, the number of observers is increased (e.g., double-checking), and the result cannot be adequately documented. The test result is therefore purely subjective and determined visually. Test evaluation is potentially error-prone due to unclear evaluation parameters.

[0026] In addition, the known state-of-the-art methods usually only detect medium and large defects, but not small and tiny defects, such as fine cracks.

[0027] Some suggestions for conducting integrity tests have emerged from the state of the art:

[0028] For example, FR 2 909 904 A1 describes a method for monitoring the integrity of hollow-fiber filter membranes, wherein a static pressure difference is applied between the two compartments of a hollow-fiber membrane, in particular by pressurizing one of the two compartments (external or internal) using a gas that has previously been emptied of the water it contains (emptied compartment). The other compartment remains filled with water (water compartment). The pressure is chosen to be lower than the membrane's bubble pressure but higher than the pressure of the water compartment. By way of example, a pressure difference of 0.5 bar = 50 kPa is given. If a membrane is not intact due to a rupture of the hollow fiber, air flows in the form of bubbles through the broken fiber from the emptied compartment into the water compartment due to the pressure difference on both sides of the membrane.Integrity testing is performed by measuring the dynamic overpressure generated by the air bubbles in the water chamber. Filtration is primarily used for water treatment, with sensitivity depending on the quality of the raw water used. The hollow-fiber membranes used are also intended to be suitable for microfiltration, ultrafiltration, nanofiltration, or reverse osmosis. However, in Figures 1 and 2, an inner diameter in the millimeter range is specified for the inner channels of the hollow fibers. In contrast, viruses have diameters in the nm range, so the focus here is on larger areas. Step-by-step filling of the hollow-fiber membranes is not described, meaning they cannot be completely filled and the reliability of the integrity test cannot be guaranteed. The volume flow of the gas through the hollow-fiber membranes is also not measured, making it impossible to detect even the finest defects.

[0029] JP 2005 013947 A provides a membrane separation device that can be used to identify damaged hollow fibers during a water circulation process. For this purpose, bubbles are mixed into the raw water. When a hollow fiber membrane is damaged, bubbles enter the hollow fiber membrane 4 and flow from an opening 4a at the top into a permeation chamber 14. Additionally, fine powder dispersed in the gas from the defect in the hollow fiber membrane serves to detect the defect in the hollow fiber membrane. The bubbles escaping from the opening 4a are detected using images from a CCD camera 24, thereby determining the position of the damaged hollow fiber membrane. Raw water is processed, so this system cannot be used for virus filtration. Only large defects are detected, since only in these cases does fine powder occur.There is no step-by-step filling of the membrane separation device, so a reliable integrity test cannot be performed. Furthermore, the volume flow of the gas through the membrane separation device is not measured, making it impossible to detect even the smallest defects.

[0030] JP 2006 305452 A relates to a filtration device using a hollow fiber membrane. River water, lake water, groundwater, or seawater are used. Filtration with hollow fiber membranes occurs from the outside in, so that the purified water rises, for example, within the hollow fibers, while the removed suspended materials cannot penetrate the hollow fiber walls. Air bubbles are used to remove suspended matter adhering to the hollow fiber membrane. This means that air bubbles impinge on the suspended matter adhering to the side surface of the hollow fiber membrane while the hollow fiber membrane vibrates. In this way, the suspended substance is peeled off the hollow fiber membrane. To detect a rupture of the hollow fiber membrane, air bubbles are also introduced, so that air from the ruptured part enters the interior of the hollow fiber membrane. The bubbles are visible from the outside through a transparent viewing cap.Furthermore, it is described that the material with a minor tear can either be repaired or discarded and replaced. A filtration system designed for contaminated water is not suitable for virus filtration. There is no gradual filling of the filtration device, so a reliable integrity test cannot be performed. Furthermore, the volume flow of the gas through the filtration device is not measured, so the detection of even the finest defects is not possible. Furthermore, the hollow fibers can be repaired or partially replaced. Repair is not possible with a virus filtration module due to the delicate hollow fibers with tiny openings. It can therefore be assumed that a completely different order of magnitude of the materials to be separated is being targeted here.

[0031] JP 3 557712 B2 and JP H07 136476 A disclose a method for detecting a defect in a hollow fiber membrane module by passing a gas through the module. If a defect exists in the hollow fiber membrane, fine particles, such as dust, are present in the gas passed through the hollow fiber membrane module. A laser beam is used to detect the fine particles in the gas, whereby the laser beam is scattered when the laser beam strikes the fine particles, which can be captured by a CCD camera. According to JP 3 557712 B2, the diameter of the hollow fiber membrane module appears to be 5 mm or less, preferably 1 mm. This probably refers to the hollow fiber membranes themselves. Furthermore, a defect should be repairable. There is no gradual filling of the hollow fiber membrane module with liquid, so a reliable integrity test cannot be performed.Furthermore, the volume flow of the gas through the hollow-fiber membrane module is not measured, making it impossible to detect even the finest defects. Furthermore, the hollow fibers can be repaired. Repair is not possible with a virus filtration module due to the delicate hollow fibers with tiny openings. It can therefore be assumed that a completely different order of magnitude of materials to be separated is being targeted here. Virus filtration cannot be performed with the hollow-fiber membrane module.

[0032] The present invention is therefore based on the object of avoiding the disadvantages of the prior art and providing a testing method for the integrity of virus filtration modules in the form of hollow-fiber filter modules. This method enables a reliable testing procedure whose test results are reproducible, can detect even the smallest defects, and minimizes the risk of damage to the hollow fibers during testing. A device for partially or fully automated integrity tests is also to be provided.

[0033] SUMMARY DESCRIPTION OF THE INVENTION

[0034] The above-described object is therefore achieved according to the invention by a method for testing the integrity of one or more virus filtration modules, comprising the steps: a) installing one or more virus filtration modules in a filtration device, each virus filtration module being in the form of a hollow fiber filter module, each comprising hollow fibers with an inner region and hollow fiber interstices, a feed side, a retentate side, and a filtrate side, and each having a line on the feed side, a line on the retentate side, and a line on the filtrate side; b) filling the virus filtration module(s) and the connected lines with liquid at a constant pressure of at most 98 ± 5 kPa, comprising the steps: b1) filling all lines connected to the virus filtration module(s) with liquid, but without filling the virus filtration module(s);b2) filling the inner region of the hollow fibers of the virus filtration module(s) with liquid, wherein the line on the feed side and the line on the retentate side are opened and the line on the filtrate side is closed, and b3) filling the spaces between the hollow fibers of the virus filtration module(s) with liquid, wherein either the line on the feed side and the line on the filtrate side are opened and the line on the retentate side is closed, or the line on the retentate side and the line on the filtrate side are opened and the line on the feed side is closed; wherein in steps b2) and b3), the liquid is supplied to the virus filtration module(s) from the line on the feed side or from the line on the retentate side;c) stopping the supply of liquid as soon as the virus filtration module(s) and the lines are filled with liquid, maintaining the pressure, and closing all lines; d) supplying air to the virus filtration module(s) with step d1) or d2): d1) opening each of the lines on the feed side and the line on the filtrate side of the virus filtration module(s) and leaving the line on the retentate side closed, maintaining the pressure, in order to supply air at a constant pressure at the same level as the liquid pressure from the line on the feed side into the virus filtration module(s);or d2) opening each of the lines on the retentate side and the line on the filtrate side of the virus filtration module(s) and leaving the line on the feed side closed, while maintaining the pressure, in order to supply air at a constant pressure equal to the liquid pressure from the line on the retentate side into the virus filtration module(s); wherein during step d1) or d2), the volume flow of air through the one or more virus filtration modules is measured; and e) automatically detecting an occurring chain of air bubbles in the line on the filtrate side of the virus filtration module(s);

[0035] The disclosure also relates to a filtration device for carrying out the method according to the invention, comprising one or more virus filtration modules which are in the form of hollow fiber filter modules, each comprising hollow fibers with an inner region and hollow fiber interstices, each having a feed side, a retentate side and a filtrate side;

[0036] Facilities for attaching and securing one or more virus filtration modules; one line on the feed side, one line on the retentate side, and one line on the filtrate side of each virus filtration module, for supplying liquid and / or air at a constant pressure of not more than 98 ± 5 kPa to the virus filtration module(s);

[0037] Opening and closing devices for the respective lines; a connection for supplying liquid at a constant pressure of no more than 98 ± 5 kPa via the lines to the virus filtration module(s); a connection for supplying air at a constant pressure equal to the liquid pressure via the lines to the virus filtration module(s); a detection device for automatically detecting a chain of air bubbles in the line on the filtrate side of the virus filtration module(s) and a measuring device for measuring the volume flow of air through the virus filtration module (in the case of only one virus filtration module) or through the virus filtration modules (in the case of several virus filtration modules present simultaneously).

[0038] The present disclosure thus enables, for the first time, a partially automated or fully automated testing of the integrity of virus filtration modules in the form of a visual leak test method, whereby the combined determination of the occurring air bubble chain and volume flow of the air through each virus filtration module makes it possible to detect even the smallest defects.

[0039] The invention further relates to a method for cultivating prokaryotic or eukaryotic cells in liquid cell culture in a bioreactor to produce a product, in particular protein, and to carry out virus filtration of the resulting product using one or more virus filtration modules, wherein the method for testing the integrity of the one or more virus filtration modules according to the present invention is carried out before and / or after virus filtration, in particular before and after virus filtration.

[0040] The invention also relates to a process for producing a recombinant protein, the process comprising the following steps:

[0041] Step a) Cultivation of prokaryotic or eukaryotic cells expressing a recombinant protein in cell culture in a bioreactor;

[0042] Step b) Harvesting the recombinant protein;

[0043] Step c) Purification of the recombinant protein;

[0044] Step d) removing any viruses that may be present from the resulting recombinant protein in a virus filtration with one or more virus filtration modules, wherein the method for testing the integrity of the one or more virus filtration modules according to the present invention is carried out before and / or after the virus filtration, in particular before and after the virus filtration.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The embodiments of the present invention will be described by way of example with reference to the accompanying figures, which are drawn schematically and not to scale so that no assumptions can be made regarding precise geometric values ​​with respect to the actual size. The figures of the present disclosure are incorporated in and constitute a part of the specification and also illustrate embodiments of the invention without limitation to the specific embodiments described. The drawings, together with the summary and detailed description, serve to explain the principles of the present disclosure. Where possible, like features are designated by like reference numerals throughout the figures. Figures 1 to 9 are schematic representations of exemplary embodiments of the present disclosure. In particular:

[0047] Figure 1 is a schematic, simplified view of the interior of a virus filtration module in the form of a hollow fiber filter module;

[0048] Figure 2 is a schematic, enlarged sectional view of a hollow fiber of the hollow fiber filter module of Figure 1;

[0049] Figure 3a is a schematic, enlarged front view of a virus filtration module in the form of a hollow fiber filter module with connected lines;

[0050] Figure 3b is a schematic enlarged sectional view of an intact hollow fiber of the hollow fiber filter module of Figure 1;

[0051] Figure 3c is a schematic, enlarged sectional view of a non-intact hollow fiber of the hollow fiber filter module of Fig. 1;

[0052] Figure 4 is a schematic, simplified view of a virus filtration module in the form of a hollow fiber filter module with connected lines on the feed side, retentate side and filtrate side according to an embodiment of the method according to the invention;

[0053] Figure 5 is a schematic, simplified view of a virus filtration module in the form of a hollow fiber filter module occupying an intermediate position between vertical and horizontal positions;

[0054] Figure 6a is a schematic, simplified view of an embodiment according to the invention, wherein the relative position of the virus filtration module and the air filter to each other is shown by way of example;

[0055] Figure 6b is a schematic, simplified view of a further embodiment of the invention, wherein the relative position of the virus filtration module and the air filter to each other is shown by way of example;

[0056] Figure 7 shows an exemplary setup for measuring the air bubble chain optically using a scattered light sensor in a simplified form in a partial sectional view;

[0057] Figure 8 is a schematic view of a section of a filtration device according to an embodiment of the present invention, according to which several virus filtration modules can be tested simultaneously using the method according to the invention and

[0058] Figure 9 shows a schematic view of a section of a filtration device according to another embodiment of the present invention, according to which several virus filtration modules can be tested simultaneously using the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0059] DEFINITION OF GENERAL TERMS

[0060] Terms not specifically defined herein should be given the meaning that a person skilled in the art would give them in light of the disclosure and the context.

[0061] The term "integrity" in connection with a filter means determining whether the filter is functioning properly or is impaired. An intact filter therefore fulfills its filtering function as intended. A "filter integrity test" serves to demonstrate that a filter is or was (fully) functional and has functioned and continues to function without disruption, i.e., is / was undamaged and does / did not allow any undesirable components to pass through. The integrity test modified according to the invention is based on the integrity test with a manual test execution according to the manufacturer's instructions for handling and testing in the general Planova virus filter testing procedure ("TAS 33088, Integrity Test Procedure Planova™ 15N, 20N, 35N and 75N Filters, Visual Leakage Test (VLT)", Version 1.1 dated February 25, 2019), but is generally applicable to any type of virus filtration module.

[0062] The term "virus filtration module" represents a filter or filter unit intended and designed to separate viruses from liquids by filtration. In the present disclosure, these are hollow fiber filter modules. The terms "virus filtration module" and "hollow fiber filter module" are used interchangeably in the present disclosure and are understood here as synonyms. The terms "virus filtration module" and "hollow fiber filter module" are abbreviated here to simply filter module or filter. According to the invention, virus filtration modules are used that are only approved for pressures up to 98 ± 5 kPa. Numerous suitable virus filtration modules are commercially available. The virus filtration modules used according to the invention are therefore also used for virus filtration at a maximum pressure of up to 98 ± 5 kPa.According to the invention, virus filtration is therefore carried out, for example, at pressures in the range of 82 to 85 kPa or even 78 to 85 kPa.

[0063] The term “filter module” or “filtration module” is used synonymously with the “virus filtration module”, whereby the term “module” is understood to mean that, depending on the design, the filter unit can also be supplemented by further filter units or modules, which can then be connected together and together assume the filter function as in a modular system.

[0064] A "filtration device" is any type of device that enables filtration with a virus filtration module. For the integrity test to be performed, this includes, for example, supply and discharge lines to the virus filtration module, means for closing and opening the supply and discharge lines, means for providing a liquid to be filtered, means for receiving a filtered liquid, and means for providing air. For virus filtration to be performed after the integrity test, this can additionally include, for example, means for providing a product to be filtered, comprising liquid, and means for receiving a product to be filtered, comprising liquid. The supply and discharge lines to the virus filtration module that are used for the integrity test can advantageously also be used for virus filtration."Hollow fiber filter modules" represent a well-known technology in which hollow fibers with partially permeable walls act as filter membranes, which are combined in the form of fiber bundles to form filter modules. The hollow fibers have an inner region, also referred to as the hollow fiber interior. There are also spaces between the hollow fibers in a hollow fiber filter module.

[0065] The term "filtrate-side line" refers to the line connected to the filtrate side of the virus filtration module. Similarly, "feed-side line" refers to the line connected to the feed side of the virus filtration module. The "retentate-side line" refers to the line connected to the retentate side of the virus filtration module.

[0066] The liquid used for the integrity test comprises or consists of water. For example, water may be present as the main component. For example, water is present in the liquid at a level of at least 90% by weight, or at least 95% by weight, or at least 98% by weight, or at least 99% by weight, or at least 99.5% by weight.

[0067] The term "water" refers to any type of water that can be used. Purified water is used in particular, but in some embodiments, tap water can also be used. The selection of the water type depends on the intended use. Purified water, as defined in the present disclosure, is water that has undergone a purification process, such as distillation, reverse osmosis, carbon filtration, capacitive or electrode ionization, micro- or ultrafiltration, ultraviolet oxidation, or the like, to remove contaminants and make it suitable for use. Combinations of these processes can also be used to obtain water of high purity, e.g., ultrapure water, where its trace contaminants are measured in parts per billion (ppb) or parts per trillion (ppt). For example, distilled, double-distilled, or deionized water can be used.In one embodiment, the water used in the method of the invention is ultrapure water, e.g., Type 1 ultrapure water according to ASTM D1193 or ISO 3696. According to another embodiment, the water used may be sterile water suitable for administration to a subject (human or animal), such as water for injection (WFI).

[0068] The term "process air" refers to compressed air used directly as a process medium in the process. Compressed air can meet certain quality and purity criteria, is generally dry, germ-free, and can even be sterile. According to the invention, outside air taken from the environment is used as process air. This is compressed air, i.e., compressed air, but at a maximum pressure of 98 ± 5 kPa. Atmospheric pressure is 101.3 kPa.

[0069] The term "transparent" refers to materials that allow the majority of light to pass through, with a smaller portion being absorbed and scattered. In contrast, materials with limited light transmission are not transparent and are also referred to as opaque. Transparency is therefore the ability of a material to transmit light waves (transmission). Transparent materials are characterized by high transmittances. The term "transparent" here means that the material used has a high light transmittance, which means that there is a light transmission of at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95% of the light of the wavelength used and for the thickness of the material used. Transparent materials used here are those that can be used under the selected process conditions, i.e.withstand a pressure of up to 98 ± 5 kPa and are not attacked by the liquid used, especially water.

[0070] EMBODIMENTS OF THE INVENTION

[0071] The individual steps of the integrity test of the present disclosure with its different embodiments will be explained in detail below, whereby the method will first be described using an embodiment with a virus filtration module:

[0072] Before performing the method for testing the integrity of a virus filtration module according to steps a) to e), it may be expedient to sterilize the lines, particularly with hot steam sterilization. This is usually performed without a virus filtration module, with a fitting piece being inserted into the filtration device to close the open section instead of the virus filtration module. Sterilization can be performed, for example, at 100°C or more, particularly in the range of 100-130°C. This is useful if virus filtration is to follow the integrity test.

[0073] According to one embodiment of the invention, it is expedient to pressurize the lines after sterilization and before performing step a) to prevent the introduction of contamination after sterilization. This is followed by a pressure reduction, for example, to a pressure P < 10 kPa, in all lines, whereby pressure equalization occurs throughout the entire system. This serves to protect the virus filtration module from damage.

[0074] In step a) of the present method for testing the integrity of a virus filtration module, a virus filtration module is first provided and installed in a filtration device. The filtration device is a device in which the integrity test of the virus filtration module is to be performed. The lines of the virus filtration module are functionally connected to suitable fluid or air connections. The filtration device is also designed, in particular, to enable virus filtration to be performed with the virus filtration module.

[0075] The virus filtration module here represents a hollow fiber filter module that is to be used in a process for removing viruses from a liquid. The hollow fiber filter module comprises hollow fibers with an inner region, also referred to as the hollow fiber interior, and hollow fiber interstices. The virus filtration module in the form of a hollow fiber filter module is not further restricted; any hollow fiber filter module known to those skilled in the art that can be used to remove viruses can be used, provided it is approved for virus filtration at a pressure of up to 98 ± 5 kPa. Examples include the hollow fiber filter modules Planova™ 15N (hollow fiber diameter 15 nm), 20N, 35N, or 75N filters from Asahi Kasai, which are used to remove viruses. Virus filtration modules approved for higher pressures are not used according to the invention.

[0076] The viruses that can be removed with the virus filtration module are also not limited. Almost any type of virus can be removed from liquids using conventional virus filtration modules. This includes, for example, parvoviruses, which are among the smallest viruses found in nature. Larger viruses, such as retroviruses, can also be removed with virus filtration modules.

[0077] The general structure of such virus filtration modules in the form of hollow fiber filter modules has already been explained in detail in Fig. 1. These have a feed side, a retentate side, and a filtrate side, each with connected lines. The material of the lines is not particularly limited, provided this does not adversely affect the performance of the integrity test. Therefore, materials suitable for the process conditions of the integrity test are used, i.e., a pressure of up to 98 ± 5 kPa and the use of liquid, including water, as the liquid medium. For example, plastics or metal, particularly stainless steel, are used.

[0078] Commercially available hollow fiber filter modules typically have two inlets and two outlets: For the two inlets defined by the two ends of the hollow fibers, one end is selected as the supply for the liquid to the hollow fiber filter (the so-called feed side) and one end as the discharge for the liquid from the hollow fiber filter (the so-called retentate side). One of the two inlets is therefore selected as the outlet. Both inlets are completely equivalent, so the selection is only pro forma. The two outlets of the hollow fiber filter modules are analogous to the inlets, which can be flexibly selected. Both outlets are also completely equivalent, so the selection is only pro forma. The choice of inlet and outlet does not change the filtration or the test result. The actual filtration occurs through the wall of the hollow fibers, so the filtrate is obtained through the wall of the hollow fibers (the so-called filtrate side) via two outlets.To carry out the integrity test method according to the disclosure, only one entrance and one exit are required at a time, so that further entrances and further exits are closed during the test.

[0079] The arrangement of the virus filtration module in step a), i.e. the orientation of the hollow fibers during installation of the virus filtration module into a prepared filtration device in which the integrity test is to be carried out, can be completely arbitrary. There is actually no preferred direction. The virus filtration module can, for example, be arranged with the hollow fibers aligned horizontally or vertically, or in an intermediate position between horizontal and vertical directions. According to one embodiment, it can be advantageous if the hollow fibers in the virus filtration module run vertically or in an intermediate position between horizontal and vertical directions. The term “in an intermediate position between horizontal and vertical directions” means that a virus filtration module is not positioned upright, as in Fig.4, but is tilted at any angle, but not yet in a horizontal direction (positioned quasi lying down) (see Fig. 5 for an exemplary intermediate position of a virus filtration module). According to one embodiment, the hollow fibers are particularly parallel to one another during the integrity test. An upright (vertical) position of the virus filtration module, as schematically shown in Fig. 1, was chosen for reasons of simplified representation and better descriptiveness.

[0080] In step b) of the process, the virus filtration module and the connected lines are filled with liquid, including water. For this purpose, a maximum liquid pressure of 98 ± 5 kPa is used. This pressure is within a range that can be readily used with virus filtration modules and does not adversely affect or even damage them. Significantly lower pressures are also possible, such as the following lower limits: 10 ± 0.5 kPa or 20 ± 1 kPa or 30 ± 1.5 kPa or 40 ± 2 kPa or 50 ± 2.5 kPa or 60 ± 3 kPa or 70 ± 3.5 or 80 ± 4.0 or 90 ± 4.5, with the upper limit being 98 ± 5 kPa. The higher the pressure is set, the more easily the chain of air bubbles can be detected. If a fluid pressure within the above range is selected, it will be maintained throughout the integrity test.The integrity test can also be performed at a low pressure of 10 ± 0.5 kPa or 20 ± 1 kPa, since a chain of air bubbles can also be detected in this case. According to one embodiment, the same or a lower pressure as in the integrity test of the invention is selected in a virus filtration performed with the tested virus filtration module(s).

[0081] The filling with liquid takes place in 3 sub-steps, whereby the liquid has a constant pressure of maximum 98 ± 5 kPa, which - as already explained - is chosen to be the same in all 3 sub-steps:

[0082] In step b1), all lines connected to the virus filtration module are filled with liquid, but without filling the virus filtration module.

[0083] In step b2), the inner region or the hollow fiber interior of the hollow fibers of the virus filtration module is filled with liquid, whereby the line on the feed side and the line on the retentate side are opened and the line on the filtrate side is closed.

[0084] In step b3), the spaces between the hollow fibers of the virus filtration module are filled with liquid, whereby either the line on the feed side and the line on the filtrate side are opened and the line on the retentate side is closed, or the line on the retentate side and the line on the filtrate side are opened and the line on the feed side is closed.

[0085] In steps b2) and b3), the liquid can be fed to the virus filtration module from the line on the feed side or from the line on the retentate side. If the virus filtration module has been installed vertically in the filtration device, feeding the liquid from the feed side means that the liquid is fed to the virus filtration module from below. Feeding from the retentate side then means that the liquid is fed to the virus filtration module from above. For practical reasons, it is advantageous if the liquid is fed from the same side in both step b2) and step b3); however, this is not required.

[0086] As already mentioned, the orientation of the virus filtration module is completely arbitrary. The vertical orientation of the hollow fibers, and thus also of the virus filtration module, is only mentioned to better illustrate the processes. The expression "feed from below" or "from above" does not mean that a virus filtration module must always assume an exactly vertical position. Rather, the virus filtration module can also assume any intermediate position that deviates from the vertical orientation and lies between a vertical and a horizontal orientation (see Fig. 5). Even if the virus filtration module is tilted at an angle away from the vertical direction, feeding can occur from below or above.

[0087] Water or a buffer solution is used as the liquid, in particular. There are no particular restrictions on the type of water used. The type and purity of the water can be selected depending on the intended use of the filter module. However, it should be understood that it should not contain any components that could compromise the virus filtration module or the integrity test in any way. Examples of suitable water include distilled, double-distilled, or deionized water, or Type 1 ultrapure water according to ASTM D1193 or ISO 3696, particularly sterile water suitable for administration to humans or animals, such as water for injection (WFI). This depends on the intended use, particularly the liquid product from which the viruses are to be removed.

[0088] According to one embodiment, a buffer solution is used which generally contains 95 to 99.5 wt.% water, such as WFI water (water for injection). In addition to water, the buffer solution contains a component such as acetate / acetic acid and may also contain salts such as NaCl, solvents such as ethanol, and additives such as sugars such as sucrose and one or more amino acids, e.g., histidine. The advantage of such buffer solutions is that they can have better compatibility with a product to be filtered and, for example, increase the stability of a product used. The presence of salts also has the advantage that the electrical conductivity of the liquid can be measured. This is important when WFI water is used as the water, which exhibits virtually no electrical conductivity. The composition of the buffer solution is therefore selected particularly product-specifically.

[0089] The virus filtration module can be filled with liquid according to steps b2) and b3) from the feed side or from the retentate side. If the virus filtration module were in a vertical position, the feed side would be at the bottom, for example, and the retentate side at the top. However, the virus filtration module can assume any position during filling, i.e., during the entire integrity test and, if applicable, also during the virus filtration process. However, it is advisable to maintain a set orientation or position of the virus filtration module(s) throughout the process, as otherwise the virus filtration module(s) would have to be removed from and reinstalled in a system, which is not practical from a process engineering perspective.

[0090] According to one embodiment, the liquid is fed from the feed side, for example, from below, into the inner area and the interstices of the virus filtration module. Feeding the liquid from below can be advantageous, as this is generally simpler from a process engineering perspective. A further advantage of feeding the liquid from below is that any air present in the filter module is flushed upwards out of the filter, so that no more air can remain in the filter. At the same time, this allows for complete venting of the filter module.

[0091] In step b1), the fill level of the lines can be checked to ensure that no air bubbles remain in the outflowing fluid. This can be done visually by an employee or with a sensor.

[0092] In steps b2) and b3), the filling level of the virus filtration module with liquid can be monitored by measuring the pressure before and after the filter module and determining the differential pressure. This can be done, for example, by measuring the pressure in the line that supplies the liquid to the virus filtration module and in the line that discharges the liquid from the virus filtration module and calculating the difference between the two pressures. This can be done in both steps b2) and b3). The lower the differential pressure, the higher the filling level. At a maximum pressure difference of 98±5 kPa, it can be assumed that the virus filtration module is filled according to steps b2) or b3).

[0093] Additionally or alternatively, the amount of liquid supplied can be set in relation to the dead volume of the lines and virus filtration module, whereby the following applies: the amount X of liquid supplied > dead volume. In this case, the virus filtration module would then be filled. The dead volume is all volume fractions of the system under consideration that are to be filled with liquid. The dead volume for step b2) and step b3) can be easily determined by a specialist. The dead volume can be obtained, for example, from the manufacturer's specifications or requested from the manufacturer. For example, a 4m 2 The filter module has a dead volume of 1,900 mL according to the manufacturer's specifications. When testing multiple filter modules, their dead volumes are added together.

[0094] The virus filtration module is completely filled with liquid so that, as far as possible, no empty space remains. In other words, all hollow fiber interiors (step b2)) as well as all spaces (step b3)) between the hollow fibers in the filter module are filled with liquid. Furthermore, the lines connected to the virus filtration module are completely filled with liquid. This is achieved by adding the liquid under pressure, with the pressure adjusted within the specified range.

[0095] Before the liquid enters the virus filtration module according to steps b2) and b3), an inlet filter can be provided in the feed line to filter out possible impurities and contamination from the liquid and prevent them from entering the virus filtration module. This inlet filter can therefore be provided in the line on the feed side and / or in the line on the retentate side. Similarly, it may be advantageous to install an outlet filter in the discharge line at the outlet from the virus filtration module. This also prevents possible impurities and contamination from being present in the liquid and thus impairing subsequent detection.

[0096] As soon as the virus filtration module and the lines are completely filled with liquid, the liquid supply is stopped in step c), but the applied pressure is maintained. For this purpose, all lines are closed, resulting in a closed system that is essentially completely filled with liquid and still maintains the applied pressure of a maximum of 98 ± 5 kPa.

[0097] The virus filtration module(s) and the connected lines are filled with liquid at a constant pressure of no more than 98 ± 5 kPa in three steps. This ensures that the virus filtration module(s) are completely filled with liquid. Tests have shown that filling a virus filtration module in a single step is not possible, as the liquid seeks the path of least resistance and then does not fill all of the empty spaces in the virus filtration module. A reliable integrity test cannot then be carried out. Carrying out the filling process in three steps therefore not only represents a particularly gentle but also controlled procedure. Dividing the filling process into three steps also enables triple control, whereby in each step, it can be checked and verified whether the filling has been completed.This can be precisely determined, for example, based on the amount of liquid supplied in relation to the dead volume (e.g., based on manufacturer's specifications), as already explained. The orientation of the virus filtration module generally plays no role during filling, as the step-by-step filling process is completely independent of the orientation. The virus filtration module can be in a vertical or horizontal position, or tilted at any angle other than vertical or horizontal. If an orientation of a virus filtration module is given as an example, this is only for the purpose of better understanding and a simplified description.

[0098] According to an alternative embodiment, an optional intermediate step can be carried out after step c), in which the existing liquid is completely drained from the inner region of the hollow fibers only. If the virus filtration module is arranged vertically or in an intermediate position between vertical and horizontal in the filtration device, this can be done, for example, by opening the line on the feed side, allowing the liquid to drain downwards. This continues until the inner region of the hollow fibers and the connected line are completely emptied. This can be monitored by ensuring that no more liquid escapes from the outlet of the filtration unit. This can be done by visual inspection or via a sensor.A procedure that omits filling the inner region of the hollow fibers according to step b2) and only fills the interstices according to step b3) is not possible for physical reasons. Therefore, the entire virus filtration module must first be filled before the liquid can be drained from the inner region.

[0099] This optional intermediate step is not always necessary. This intermediate step has the advantage that the internal emptying of the virus filtration module represents a particularly gentle procedure for the subsequent integrity test. If the inner area or the inside of the hollow fibers is filled with pressurized liquid and pressurized air is then added for the integrity test, this could cause the hollow fibers to expand, which could further increase the stress on the filter module and increase the risk of damage.

[0100] Before performing step d), a leak test of the entire system, including the virus filtration module, can be performed to rule out any leaks in the system, e.g., due to an improperly installed seal. This serves to ensure that no air escapes from the system and could thus falsify the subsequent integrity test and its evaluation. However, since according to the invention the (total) volume flow of air through the filtration system and thus through the virus filtration module (if only one virus filtration module is being tested) or through the virus filtration modules (if several virus filtration modules are being tested simultaneously) is measured during the method, a leak test is no longer necessary, since the size of the volume flow immediately indicates any leaks in the system. For the sake of completeness, one possible embodiment of a leak test will nevertheless be described here.

[0101] The leak test is also known as a pressure maintenance test. In this test, air is supplied to the virus filtration module via the retentate side or the feed side. A pressure below 98 ± 5 kPa, the so-called pre-stabilization pressure, is selected, for example, in the range of 60 - 70 kPa. After a stabilization time of at least 180 seconds, the pressure drop in the system is measured.

[0102] In the leak test, the liquid-filled lines on the virus filtration module are opened (e.g., lines 55a and 75a or 65a and 75a in Fig. 4). Another outlet on the filter module is closed (e.g., outlet at 75b in Fig. 4). Unused inlets and outlets of the system are closed (e.g., inlet and outlet for water 70 and air 80 in Fig. 9). Air, for example, process air, is then supplied to the virus filtration module. This can occur either from the retentate side (at 65a in Fig. 4) or from the feed side (at 55a in Fig. 4) of the virus filtration module. If the virus filtration module is installed in a vertical position in the filtration device, as shown in Fig. 4, or in an intermediate position between vertical and horizontal, the air is supplied via the retentate side from above or via the feed side from below. Other orientations are possible.The pressure was built up gradually by means of a controlled pressure increase (e.g. fixed ramp) of the supplied air until a test pressure was reached, which is also referred to as the pre-stabilization pressure. The air pressure in the system can be increased, for example, using a time ramp (kPa / min) starting at 0 kPa to a value, for example, in the range of 60 to 70 kPa. The pre-stabilization pressure is selected to be lower than the pressure used in the integrity test (maximum 98 ± 5 kPa). It may be advisable to allow a stabilization period after the pre-stabilization pressure has been reached so that the air can disperse throughout the system before the leak test is evaluated. The stability period is at least 180 s. The leak test is considered passed if the pressure drop after the stabilization period is < 10 kPa, in particular < 5 kPa. If the pressure drop is < 10 kPa, it must be assumed that there is no leak in the filtration system.If the pressure drop is > 10 kPa, it must be assumed that there is a leak in the system. In this case, the leak in the filtration system is located and eliminated.

[0103] After step c) or after the optional intermediate step described above or after the optional leak test described, air is supplied to the virus filtration module in step d1) or d2). Both process variants result from the air being supplied to the virus filtration module from either one of the two sides. If the virus filtration module is installed with vertically aligned hollow fibers or in an intermediate position between vertical and horizontal, the air is supplied from above or below. If the virus filtration module is installed in a different orientation, the air is supplied either from one side or the other. However, it is difficult to describe the complex relationships involved in distinguishing one side from the other.To simplify the following explanations, the vertical orientation of the virus filtration module is assumed for ease of reference to "bottom" or "top," even though this vertical orientation may not be exact when performing the procedure. The virus filtration module could also be installed in the filtration device in a different orientation.

[0104] Specifically, according to the first method variant, in step d1), the line on the feed side (in the described embodiment, for example, at the lower end of the filter module) and a line on the filtrate side of the filter module (on the wall side of the filter module) are opened, and the line on the retentate side (at the upper end of the filter module) and, if applicable, another line not used for the test on the filtrate side of the filter module (on the wall side of the filter) are each left closed in order to force air into the virus filtration module (in the described embodiment, for example, from below) via the line on the feed side at a constant pressure at the same level as the liquid pressure, i.e., a pressure of at most 98 ± 5 kPa. Opening the lines does not mean that the lines are opened to the outside.Rather, the pressure of a maximum of 98 ± 5 kPa is fully maintained in the virus filtration module and the connected lines. The opening serves only to allow pressurized air to be supplied. Those skilled in the art will know how to supply air at the same pressure to a pressurized system.

[0105] In the alternative, second method variant, in step d2), the line on the retentate side (in the described embodiment, for example, at the upper end of the filter module) and a line on the filtrate side of the filter module (on the wall side of the filter module) are opened, and the line on the feed side (in the described embodiment, for example, at the lower end of the filter module) and, if appropriate, another line not used for the test on the filtrate side of the filter module (on the wall side of the filter) are left closed in order to force air into the virus filtration module (in the described embodiment, for example, from above) via the line on the retentate side at a constant pressure at the same level as the liquid pressure, i.e., a pressure of at most 98 ± 5 kPa. Opening the lines does not mean that the lines are opened to the outside.Rather, the pressure of a maximum of 98 ± 5 kPa is fully maintained in the virus filtration module and the connected lines. The opening serves only to allow pressurized air to be supplied. Those skilled in the art will know how to supply air at the same pressure to a pressurized system.

[0106] The opening and closing of the lines can be achieved using suitable devices, such as shut-off devices. A ball valve, for example, which only has the states "open" and "closed," is suitable for this. Other valves are also possible, such as control valves, which allow continuous control between 0 and 100%, or automatic valves, which only have an open and closed position, or even manually operated valves. Other possibilities are also known to those skilled in the art.

[0107] The selected pressure for the liquid and thus also for the supplied air is within a range that can be easily used in virus filtration modules and does not adversely affect or even damage them.

[0108] It goes without saying that pressure monitoring can also be carried out during the test procedure using pressure measuring and control devices. This is obvious to the expert and is not explicitly described.

[0109] The supplied air is therefore forced from a filter inlet of the virus filtration module through the hollow fibers contained in the module to the filter outlet. In this case, the filter inlet is the side of the filter where the air is introduced. In the first process alternative d1), the filter inlet for the air is therefore the feed side of the filter (lower end of the hollow fibers); in the second process alternative d2), the filter inlet for the air is the retentate side of the filter (e.g., upper end of the hollow fibers). The filter outlet is always the filtrate side, where the air can or cannot escape, depending on whether the filter is intact or not.

[0110] According to one embodiment, if the virus filtration module is installed vertically or in an intermediate position between vertical and horizontal, the second method variant is used in particular, in which the air is supplied from above (upper end or retentate side of the virus filtration module). The second method alternative is advantageous because it has process-related advantages. It has proven more advantageous if air is introduced into the filter module from the highest point thereof. According to one embodiment of the invention, it may be expedient for process-related reasons if, during the explained leak test of the lines and the virus filtration module, the air is supplied into the virus filtration module from the same side, e.g., the retentate side, as in the integrity test (step d1) or d2)).

[0111] The pressurized air is used to determine whether the hollow fibers in the virus filtration module are intact, i.e., whether they are free of damage such as cracks and are therefore fulfilling the desired filtering function. If the virus filtration module is functioning properly, the air remains in the hollow fibers because it cannot penetrate the pores of the hollow fiber wall. It can then penetrate into the closed line at the filter outlet (retentate side or feed side of the filter module, depending on where the air was injected). If the virus filtration module is not functioning properly, the air passes through damage in the hollow fiber wall and thus reaches the filtrate side of the filter module, where a chain of air bubbles can then occur and be detected in the connected line on the filtrate side.

[0112] There are no specific restrictions on the air used. However, it is understood that it should not contain any components that could compromise the virus filtration module or the integrity test in any way. Process air is preferred.

[0113] According to one embodiment, the air used in process steps d1) and d2) is first passed through an air filter before it can enter the virus filtration module. This filter is designed to retain potential impurities and contaminants from the air, preventing them from entering the virus filtration module. It has been determined that the test procedure is not impaired in any way by such an air filter.

[0114] According to one embodiment, the air filter is arranged above the virus filtration module, i.e., the air filter is located completely above the virus filtration module. If an air filter is provided and the virus filtration module is installed in a vertical position (with vertically extending hollow fibers) or in an intermediate position between vertical and horizontal, it is particularly advantageous if the liquid is introduced into the virus filtration module from below (step b) (1st alternative) and the air from above (step d)), since this procedure makes it easier to prevent the air filter from becoming flooded with liquid and thus disrupting its function.

[0115] According to a further embodiment, the air-conducting line leading from the air filter can have a section that encompasses the highest point of the filtration device. This ensures that liquid cannot rise to the air filter and penetrate it. In this case, it does not matter where the air filter is located; it can then also be located below the virus filtration module. This does not have to represent the highest point of the system; rather, it is sufficient if the line leading from the air filter points to the highest point of the device. These embodiments are explained in detail in the figures. Even if the virus filtration module is completely intact, tests have shown a minimal loss of blown-in air after passing through the virus filtration module.This small amount, or creeping flow, can only be detected using an air measuring device; it can be as low as a few ml / min, for example, 3–6 mL / min. This creeping flow of air does not lead to the formation of a chain of air bubbles on the filtrate side of the virus filtration module, which must be present for at least 20 seconds. In contrast, if a virus filtration module is not intact, it has been observed that large amounts of air, for example, in the range of > 150 mL / min, escape on the filtrate side, so that a clear distinction can easily be made between an intact and a non-intact virus filtration module.

[0116] In addition to verifying the criterion of whether a continuous chain of air bubbles occurs, particularly for a duration of at least 20 seconds, another parameter is checked during the integrity test, during step d1) or d2), to determine whether the virus filtration module is intact or defective. This involves measuring the air volume flow through each virus filtration module, particularly the total volume flow through all virus filtration modules. Therefore, in steps d1) and d2), the (total) air volume flow is also measured, which indicates how much volume of a medium (here: air) is transported through a specified cross-section (here: the virus filtration module(s)) per period of time.In particular, step e) is carried out while step d1) or step d2) is still taking place, so that in particular the volume flow of air through the virus filtration module(s) continues to be measured during step e).

[0117] According to one embodiment, the air flow rate through the virus filtration module(s) can also be measured only in step e). This has no adverse impact on the test result and represents a variant of determining the test period that only plays a measurement-related role. The test period therefore begins in step d) and ends after step e), or the test period begins in step e) (while step d) continues) and ends after step e). The test period can therefore begin earlier or later during step d), which—depending on the procedure—can be determined by the air supply and the achievement of the selected pressure.

[0118] To determine whether the virus filtration module is intact or defective, the air flow rate of an intact virus filtration module is compared with that of a defective virus filtration module. It was found that an intact virus filtration module has a volume flow of injected air in the range of approximately 0.8 to 8.0 mL / min per virus filtration module, whereas a defective virus filtration module has a significantly higher volume flow. Therefore, an air flow rate of 8 mL / min per virus filtration module is assumed for an intact virus filtration module. This represents a (maximum) expected value against which a comparison is made in order to rule out diffusion effects. The air flow rate of 8 mL / min per virus filtration module therefore corresponds to the maximum volume flow (Volmax) permitted per virus filtration module.In particular, it is therefore checked whether the maximum permitted air volume flow Volmax is adhered to throughout the entire test period. According to the invention, the air volume flow can be measured individually for each virus filtration module. In particular, however, a total volume flow is measured for all existing virus filtration modules together in a single measuring device. It should be noted in this context that the volume flows, measured as the total volume flow, add up when several virus filtration modules are tested in parallel: If an intact virus filtration module has an air volume flow of approximately 8 mL / min per virus filtration module, seven virus filtration modules that are simultaneously subjected to the described integrity test will have a total air volume flow of a maximum of approximately 56 mL / min.In other words, in step d1) or step d2), a maximum total air flow rate of no more than 56 mL / min is measured when all seven virus filtration modules are intact. The maximum air flow rate is also abbreviated here as Volmax. According to the invention, the measured maximum air flow rate Volmax must therefore not exceed 8 mL / min per virus filtration module.

[0119] An experiment was conducted in which one hollow fiber of the hollow-fiber filter module was intentionally destroyed while the others were left intact. The air flow rate through the hollow-fiber filter module was then measured. This was more than 150 mL / min for the virus filtration module. It can therefore be assumed that a measured air flow rate of more than 150 mL / min indicates a defective virus filtration module. It was found that by measuring the (total) air flow rate, even the smallest defects, such as tiny cracks, in the virus filtration modules can be detected.

[0120] According to one embodiment, the air flow rate can be measured at a position located, for example, before the air is introduced into the hollow fiber filter module (step d1) or d2)). This is because it is a closed system, so the air flow rate could be measured at any point within this closed system.

[0121] According to one embodiment, a certain period of time can be provided between step d) and step e), more precisely while step d) is still being carried out but before step e) is carried out, during which the air can continue to be supplied and distributed further throughout the system. This is the so-called stabilization time, which can be up to 600 seconds. According to another embodiment, this stabilization time can also be omitted.

[0122] Step e), which follows step d), is carried out in such a way that the supply of air according to step d) is continued during step e), i.e. in step e), air continues to be supplied, whereby, if necessary, after a stabilization time of up to 600s, an automatic detection of any chain of air bubbles that may occur in the line on the filtrate side of the virus filtration module is carried out. Step e) is therefore carried out while step d) continues. The detection of a chain of air bubbles occurs in particular in the line at the filter outlet on the filtrate side of the virus filtration module. Thus, a chain of air bubbles that occurs on the filtrate side of the filter module when the filter module is not functioning is automatically detected. The detection of a possible defect in the filter in the form of a chain of air bubbles is carried out, for example, optically.The measurement principle is based on the fact that a light beam passed through a liquid changes in the presence of air. This is similar to the familiar measurement of the turbidity of a liquid, which is caused by small suspended (undissolved) particles or small droplets, which have a different refractive index than the surrounding medium. This difference leads to reflection, absorption, and scattering—i.e., a change in the direction of the incident light. The intensity and spatial distribution of the scattered light depend on the wavelength used and the size of the particles or droplets, or in this case, the presence and size of the air bubbles.

[0123] The presence of air in the liquid is therefore determined by an optical measuring method, followed in particular by an automatic evaluation of the optical measurement. A general distinction is made between two measuring methods: the attenuation of the transmitted light radiation (so-called transmitted light) and the sideways scattering of the light radiation (so-called scattered light). In the present disclosure, scattered light measurement is used in particular. This represents a measuring technique that is already established on the market and is known to those skilled in the art. Scattered light measurement is a very sensitive and reliable optical method that is also known to be used to measure very low turbidities. Scattered light measurement has proven to be a particularly suitable measuring method for the automatic detection of air bubbles in a liquid, comprising water.For automated optical detection, a counting device for the air bubble chain can be used, such as an air bubble counter.

[0124] The wavelength of the measuring radiation is, for example, in the near infrared (NIR), specifically in the range from 730 to 970 nm. However, other wavelengths are also possible, such as a white light lamp (e.g. tungsten lamp) with wavelengths in the range between 400 and 600 nm.

[0125] During the measurement, for example, light in the near infrared range with a wavelength in the range of 730 to 970 nm is emitted by the sensor, passes through the liquid-filled line, and is altered by the air present in the liquid. The light emerging from the line can then be detected, for example, via diodes or photocells, and a measurement signal can be determined from it. The measurement signal or measurement unit here is absorption, so that a specific absorption signal - more precisely, the change in the absorption signal caused by the presence of air - is detected. So-called scattered light sensors, which measure light scattering (lateral scattering), are particularly used for scattered light measurements. A scattered light sensor is usually constructed from a light source and one or more detectors for detecting the light passing through the line.For example, commercially available scattered light sensors, especially known turbidity sensors, can be used. The scattered light sensor is therefore positioned, in particular, at the filter outlet on the filtrate side of the virus filtration module, specifically on the line connected to the filtrate side. According to one embodiment, the scattered light sensor is positioned on a line running from bottom to top, so that the chain of air bubbles in the line can be completely detected as it rises.

[0126] For optical detection, the line on the filtrate side is selected so that it consists of or encompasses a transparent material. Therefore, the line can be constructed entirely of transparent material. Alternatively, the line is constructed of transparent material only at the detection point, allowing optical detection. In other words, the line is transparent at the positions where the light enters and exits the line.

[0127] The entire line at the detection location does not have to be transparent, but only selected sections of the line can be transparent.

[0128] For example, the section can represent a transparent pipe that replaces part of the line, or there can be two opposite transparent windows mounted in or on the line, or the entire line can be selected to be transparent.

[0129] The transparent section can, for example, be a transparent tube with a smaller diameter than the line and replacing part of the line. This allows the line to be split on the filtrate side and attached to the transparent tube on both sides, with the transparent tube being positioned at the detection location, i.e., where the scattered light sensor is located.

[0130] Alternatively, two transparent windows can be provided, either integrated into the duct wall or attached to the duct in the beam path of the measuring light—on the outside or inside of the duct—with one window positioned where the light enters the duct and one where the light exits the duct. It goes without saying that the transparent sections, such as a tube or two windows, are integrated into the duct or attached to it in such a way that the duct remains sealed and remains airtight. Appropriate seals can be used for this purpose. Other options beyond those described are also conceivable for the expert.

[0131] Transparent materials should be suitable for conducting the integrity test and tolerate the process conditions without adverse effects. The process conditions that play a role here are a pressure of up to 98 ± 5 kPa and resistance to the effects of the liquid used, including water. It can also be advantageous if the material can withstand high temperatures of up to 140 °C.

[0132] For example, transparent plastics are used as transparent materials. These include polystyrene (PS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl chloride (PVC), polyphenylene ether (PPO), or polyethylene (PE), or mixtures thereof. Glass can also be used as transparent materials, particularly those that are stable against attack by liquids, including water, and can withstand a pressure of up to 98 ± 5 kPa. According to one embodiment, a glass is used that has a hydrolytic resistance of Class 1 according to ISO 720 or USP 660. These include, for example, borosilicate glasses such as Duran®, Pyrex®, or Fiolax®.

[0133] For example, sapphire, also known as sapphire glass, can also be used. Sapphire, or sapphire glass, is not glass, but rather a highly pure, synthetic sapphire (single crystal) made from molten aluminum oxide (Al2O3). This material is particularly suitable because it is transparent, suitable for the pressures involved, is not attacked by liquids, including water, and can withstand high temperatures, for example, up to 140 °C without any problems.

[0134] Since sapphire is very expensive, according to one embodiment, only part or parts of the line on the filtrate side are selected from sapphire. In particular, two sapphire glass windows are used at the measurement location.

[0135] According to a further embodiment, plastic which is not transparent is used for the line on the filtrate side, wherein two glass windows or two sapphire glass windows are built into the line at the measurement location for the measurement by optical means.

[0136] According to a further embodiment, metal, in particular stainless steel, is used for the line on the filtrate side, wherein two glass windows or two sapphire glass windows are installed in the line at the location of the measurement for the measurement by optical means.

[0137] In this context, it should be emphasized again that only if the virus filtration module has a defect, such as a crack, will a chain of air bubbles appear and be detected on the filtrate side. If no chain of air bubbles escapes from the virus filtration module, this means that there are no large or medium defects. To detect even the smallest defects, the (total) volume flow of air through the virus filtration module(s) is also measured. The (total) volume flow of air must not exceed 8 mL / min per virus filtration module.

[0138] This allows the potentially present chain of air bubbles, which indicates major to moderate damage or a major to moderate defect in the virus filtration module, to be visually detected on the virus filtration module. The fluid therefore serves only as a rinsing fluid and carrier to make the chain of air bubbles in the carrier visible, enabling testing of the virus filtration modules. The integrity test is considered passed if, over the entire test period, no continuous chain of air bubbles is detected for a duration of at least 20 seconds and, at the same time, a (total) air volume flow of no more than 8 mL / min per virus filtration module is measured. The combination of both criteria (air bubble chain and air volume flow measurement) ensures that no defects can be overlooked in the tested virus filtration modules.After conducting the integrity test, it may be appropriate to discard the air and collect it, for example, in a waste collection container. The liquid, for example in the form of a buffer solution, can serve as a medium for subsequent virus filtration of a product.

[0139] According to one embodiment of the invention, the evaluation of the integrity test in step f) is also carried out, in particular, in an automated manner, with the specification for the integrity test according to which a continuous chain of air bubbles for at least 20 s is present or not and an air volume flow of a maximum of 8 mL / min per virus filtration module is measured or not throughout the entire test period. The test period begins at the moment air is supplied according to step d) and the selected test pressure of a maximum of 98 ± 5 kPa is reached and lasts until the end of the test. Since step d) is continued in the form of variants d1) or d2) during the execution of step e), the test period begins while step d) is being performed and lasts during step e). Based on the clearly defined and reproducible acceptance criteria, the test result of the integrity test can then advantageously be evaluated automatically.This can be done, for example, with the help of software. The result of the integrity test therefore serves as a criterion for assessing the approval of the tested virus filtration module for virus filtration. Therefore, the following four cases are distinguished in the integrity test of the invention for a virus filtration module:

[0140] - a chain of air bubbles lasting at least 20 seconds is detected and the air flow rate is above 8 mL / min the virus filtration module is defective;

[0141] - an air bubble chain lasting at least 20 seconds is detected and the air flow rate is 8 mL / min or less the virus filtration module is defective;

[0142] - no air bubble chain is detected and the air flow rate is above 8 mL / min the virus filtration module is defective; or

[0143] - no air bubble chain is detected and the air flow rate is 8 mL / min or less The virus filtration module is intact, there is no defect.

[0144] In this context, it should be noted that the case where a chain of air bubbles is detected for at least 20 seconds and the air flow rate is 8 mL / min or less should not technically occur. This would indicate a medium to large defect (chain of air bubbles for at least 20 seconds), which would not be detected by the flow rate measurement, which detects even the smallest defects. This case is mentioned only to illustrate all (theoretically conceivable) test variants.

[0145] In the case of a non-integral virus filtration module, i.e., if a tested virus filtration module is not intact, i.e., if it fails the integrity test, the introduced air is not retained inside the hollow fibers due to damage to the hollow fibers, such as cracks. If there is major to moderate damage, the air bubbles reach a detection device via the filtrate side, in particular a scattered light sensor, which then detects a corresponding absorption signal for the air bubbles. If an air bubble chain occurs, the measured maximum air volume flow is regularly above 8 mL / min per virus filtration module, usually significantly above 8 mL / min per virus filtration module, for example, over 150 mL / min.

[0146] If there is a small or very small damage, it may be that no air bubble chain occurs, but the volume flow of air per virus filtration module is still above 8 mL / min, so that in this case too the virus filtration module is recognized as not intact.

[0147] In the case of intact virus filtration modules, i.e., if a tested virus filtration module is intact, i.e., if it passes the integrity test, the injected air is retained due to filter wetting and the pore size in the hollow fibers, meaning that no corresponding absorption signal for an air bubble chain is detected by a detection device, in particular a scattered light sensor, on the filtrate side of the filter module. The measured (maximum) air flow rate is a maximum of 8 mL / min per virus filtration module. Both criteria for passing the integrity test are therefore met.

[0148] The integrity test according to the present disclosure therefore ensures that the hollow fibers of the virus filtration module are undamaged. While the detection of the air bubble chain can only detect medium and larger defects, the measurement of the air volume flow through the virus filtration modules makes it possible to detect even the smallest defects in the virus filtration module(s). Compliance with both criteria ensures the integrity of the virus filtration module(s). The module is checked in a first integrity test (pre-visual leak test) before the actual use (of a virus filtration) of the virus filtration module to ensure that the module is suitable for use and functioning. In addition, a second integrity test (post-visual leak test) is carried out after the module has been used, i.e.After virus filtration, to ensure that it has not been damaged during virus filtration, for example, due to overpressure or mechanical stress. It is understood that the first integrity test (pre-visual leak test) and the second integrity test (post-visual leak test) use the same procedure and the same approach.

[0149] The detection of step e) and also the evaluation of step f) are therefore carried out in particular in an automated manner, for example via a process control system (PCS), i.e., a computer system for controlling a process-engineering device, as is known from the prior art. For example, the detection device, such as a scattered light sensor, and a measuring device for the air volume flow are integrated into an internal process control system (PCS) and report within the running test program (steps a) to e) or f)) whether the defined acceptance criteria for passing the integrity test (no continuous chain of air bubbles lasting at least 20 seconds over the entire test period and measurement of the (total) volume flow of air through the virus filtration module(s) of a maximum of 8 mL / min per virus filtration module over the entire test period) were met or not.The use of a DCS system is particularly advantageous because it ensures the data integrity and immutability of the recorded data, and allows access to it at any time. For example, a process control system used is part of a process filtration device in which virus removal is carried out during a filtration process controlled by the DCS. In one and the same filtration device, not only are the two integrity tests – an integrity test of the virus filtration module before virus filtration and an integrity test of the virus filtration module after virus filtration – advantageously performed, but virus removal from a product is also carried out between the integrity tests, without the need to install and remove the virus filtration module from a suitable device for each of the processes.According to this embodiment, the functional testing of the virus filtration module(s) for filtration and the actual virus filtration with the virus filtration module(s) takes place in the same filtration device.

[0150] According to a further embodiment of the invention, the integrity test of a virus filtration module is thus carried out in a filtration device in which a virus filtration is performed between the two integrity tests. This eliminates the need for repeated installation and removal of the virus filtration module in a separate test system, as well as installation and removal in a virus filtration system. The elimination of installation and removal steps has major advantages, as virus filtration modules are very sensitive to damage. For example, improper handling of a filter module, such as even slight shaking, could result in the destruction of the hollow fibers contained therein. According to the invention, the virus filtration module(s) no longer need to be tested separately outside of a virus filtration system, thereby significantly reducing the risk of potential damage or contamination of the modules.The integrity test and virus filtration can therefore be carried out in particular within one and the same filtration device.

[0151] The test method according to the invention for a virus filtration module can therefore be carried out using a partially or even fully automated process, whereby process steps b) to d) and optionally also f) or process steps a) to d) and optionally also f) can each be carried out partially or fully automated. Step e) is always carried out fully automated.

[0152] The test method of the invention represents a validatable method that allows documented proof that the method continuously meets the defined specifications and quality characteristics. Another advantage is that non-modifiable parameters can be used in the test method, which can simplify process control, for example, through the use of a DCS system.

[0153] In particular, steps a) to e) or a) to f) are carried out directly one after the other and in the specified order without any intermediate steps.

[0154] According to the present invention, one, two, three, four, five, six, seven, or even more virus filtration modules can be tested simultaneously. When performing the integrity test according to steps a) to e) or a) to f) with multiple hollow fiber filter modules simultaneously, parallel testing is performed. This significantly reduces the time required per filter module test. If one virus filtration module is tested, it takes approximately 10 to 15 minutes. If 10 virus filtration modules are tested in parallel, it still takes 10 to 15 minutes, whereas individual testing would require 10 times as much time. Only if, when testing multiple virus filtration modules, it is determined that one of them is not intact is an individual test performed. This has the advantage of being a time-saving procedure, since multiple modules can be tested simultaneously to determine whether they are fully functional.

[0155] It is advisable to perform all steps in the same way for all virus filtration modules. For example, if a medium, such as liquid or air, is introduced, it is introduced from the same side for all virus filtration modules. If an optional intermediate step is required, it is performed in parallel for all virus filtration modules; or this intermediate step is omitted for all modules.

[0156] The test period for the integrity test to detect a chain of air bubbles and, during this time, continue to measure the air volume flow is in the range of at least 20 seconds. A period of 20 seconds for the integrity test, for example, is generally considered sufficient by the manufacturers of virus filtration modules. However, longer tests can also be carried out, for example 500 seconds or 400 seconds, or in particular 300 seconds. This only represents the period during which the air is pressed into the filter module and checked to see whether a continuous chain of air bubbles occurs for a duration of at least 20 seconds, while simultaneously measuring the (total) air volume flow. In addition, there is the preparation and follow-up of the test, so that the integrity test for each tested filter module or per batch of filter modules tested in parallel takes approximately 10 to 15 minutes.Due to possible bacterial growth, it is also advisable if the time interval between the integrity test and virus filtration does not exceed 24 hours, in particular less than 24 hours.

[0157] The invention also relates to a filtration device for carrying out the method according to the invention, comprising one, two, three, four, five, six, seven or more virus filtration modules which are in the form of hollow fiber filter modules, each comprising hollow fibers with an inner region and hollow fiber interstices, each having a feed side, a retentate side and a filtrate side;

[0158] Devices for attaching and securing one or more virus filtration modules; one line on the feed side, one line on the retentate side, and one line on the filtrate side of each virus filtration module, for supplying liquid and / or air at a constant pressure of no more than 98 ± 5 kPa to the virus filtration module(s); opening and closing devices for the respective lines; a connection for supplying liquid at a constant pressure of no more than 98 ± 5 kPa via the lines to the virus filtration module(s); a connection for supplying air at a constant pressure at the same level as the liquid pressure via the lines to the virus filtration module(s);a detection device for automatically detecting a chain of air bubbles in the line on the filtrate side of the virus filtration module(s) and a measuring device for measuring the volume flow of air through the virus filtration module(s);

[0159] The explanations of the test method of the invention apply equally to the filtration device.

[0160] The means for attaching and securing a virus filtration module in a filtration device are not further limited and are known to those skilled in the art.

[0161] If multiple virus filtration modules are to be tested simultaneously, it is advantageous if they are aligned parallel to each other. For example, the hollow fibers of each filter module are arranged vertically or in an intermediate position between vertical and horizontal. Other orientations are also possible.

[0162] When testing several virus filtration modules simultaneously, it is advisable for procedural reasons if the liquid is fed into the filter module from the same side (feed side or retentate side) for all virus filtration modules tested simultaneously.

[0163] When testing several virus filtration modules simultaneously, it is also advisable if the air is supplied to the filter module from the same side (feed side or retentate side) via a line assigned to each virus filtration module, since this allows the virus filtration modules to be tested simultaneously, i.e. in parallel, thus saving time.

[0164] When testing multiple virus filtration modules simultaneously, the respective lines on the filtrate side can be combined into a single line, and the detection device can then be located on the combined line. This makes it sufficient to use one detection device for multiple virus filtration modules. This avoids the need for complex measurements with multiple detection devices in each of the lines on the filtrate side.

[0165] For detection, a counting device for the air bubbles in the air bubble chain, such as an air bubble counter, can also be provided. An evaluation unit can also be provided. The detection device and evaluation unit are, in particular, fully automated and are operated, for example, using software.

[0166] According to one embodiment, the filtration device of the invention is part of a virus filtration system.

[0167] According to one embodiment, the filtration device is designed so that one, two, three, four, five, six, seven, or even more virus filtration modules can be subjected to the integrity test simultaneously, then virus filtration can be performed with them, and subsequently the virus filtration module(s) can be subjected to the integrity test once more. In particular, virus filtration is performed at the same or a lower pressure selected in the integrity test.

[0168] The invention further relates to a method for cultivating prokaryotic or eukaryotic cells in liquid cell culture in a bioreactor to produce a product, in particular protein, and to carry out virus filtration of the resulting product using one or more virus filtration modules, wherein the method for testing the integrity of the one or more virus filtration modules according to the present invention is carried out before and / or after virus filtration, in particular before and after virus filtration.

[0169] The invention also relates to a process for producing a recombinant protein, the process comprising the following steps:

[0170] Step a) Cultivation of prokaryotic or eukaryotic cells expressing a recombinant protein in cell culture in a bioreactor;

[0171] Step b) Harvesting the recombinant protein;

[0172] Step c) Purification of the recombinant protein;

[0173] Step d) removing any viruses that may be present from the resulting recombinant protein in a virus filtration with one or more virus filtration modules, wherein the method for testing the integrity of the one or more virus filtration modules according to the present invention is carried out before and / or after the virus filtration, in particular before and after the virus filtration.

[0174] The product subjected to virus filtration according to the invention is not further limited. According to one embodiment, this is a protein. The protein can, for example, be selected from the group consisting of monoclonal antibodies, polyclonal antibodies, monospecific antibodies, multispecific antibodies, single-chain antibodies, or antibody fragments thereof, such as Fv, scFv, Fab, Fab', scFab, F(ab')2, Fab2, Fc and Fc' fragments, immunoglobulin heavy and light chains and their constant, variable, or hypervariable regions, as well as Fv and Fd fragments, diabody, triabody, scFv-Fc, minibody, or single-domain antibodies, or a mixture thereof. The protein can, in particular, be selected from a therapeutic protein used to prevent or treat a disease or disorder.

[0175] The advantages of the present invention are extremely complex:

[0176] The disadvantages of the previously known and used integrity test are eliminated. Thus, the subjective visual air bubble check, performed by at least one person at the end of the integrity test, is replaced by a fully automated detection method. The detection of a chain of air bubbles is advantageously carried out optically, for example, via a scattered light sensor that can be operated automatically. The result in the form of two defined acceptance criteria for the integrity test, according to which the integrity test is passed if no continuous chain of air bubbles is detected for a duration of at least 20 seconds over the entire test period and, in particular, if the air flow per virus filtration module does not exceed 8 mL / min, can be clearly recorded and recorded more reproducibly.This enables the use of software that can perform automatic detection and, if necessary, automatic evaluation of the integrity test.

[0177] The combination of the two criteria for passing the integrity test makes it possible to detect even the smallest defects in the virus filtration module(s).

[0178] Determining the air flow rate even allows for a quantitative evaluation of the number of defective hollow fibers. Recording the air flow rate during the test phase and comparing it with an expected value of 8 mL / min per virus filtration module allows diffusion effects to be ruled out.

[0179] In particular, process steps b) to d) or also process steps a) to d) can be carried out at least partially automatically. Step e) is always carried out fully automatically. The evaluation of step f) is also carried out automatically.

[0180] Automation completely eliminates the risk of human error. The test results obtained are traceable and reproducible at any time thanks to data recording, thus meeting current data integrity requirements.

[0181] Automated test execution with defined parameters, as well as the recording and evaluation of results, no longer requires employees. This includes both the execution of the integrity test and, in particular, can also extend to automated evaluation using suitable software.

[0182] According to the invention, the integrity test of a filter is carried out using a validatable method, allowing the use of non-modifiable parameters. Automation ensures the reliability and reproducibility of the process. In particular, the use of a computer program in the form of a process control system (PCS) allows for simplified and reliable process control.

[0183] Conducting integrity tests on virus filtration modules no longer requires a separate test device into which the filter modules must be installed and removed for each test. Instead, it is now possible for the integrity test of the virus filtration modules to be performed in a filtration device that also performs virus filtration. This eliminates additional installation and removal steps, thus eliminating potential sources of germ contamination and possible damage to the virus filtration modules. The virus filtration modules can advantageously be subjected to the integrity test(s) while installed, within a filtration device in use.

[0184] Manual handling of the virus filtration modules between tests, which carries a high risk of damage, is thus avoided and replaced by automated procedures.

[0185] One, two, three, four, five, six, seven, or even more virus filtration modules can be tested simultaneously and in parallel. This has the advantage of significantly reducing the time required per filter module test. This time-saving approach is of enormous benefit, especially for a large-scale industrial process.

[0186] Only if a defect is detected during the simultaneous testing of several virus filtration modules in the integrity test (first integrity test or pre-visual leak test) is an individual test of the virus filtration modules carried out first, in particular according to steps b) to e) or f). The defective virus filtration module(s) can then simply be replaced, and the process can then be repeated according to steps b) to e) or f) with the replaced or all virus filtration modules. If a defect was already detected during the first integrity test, it may be advisable, after the defect has been rectified by replacing the virus filtration module(s) and successfully performing the first integrity test (pre-visual leak test), to carry out the second integrity test after virus filtration (post-visual leak test) again as an individual test with the virus filtration modules in order to better verify the result.

[0187] When testing multiple virus filtration modules simultaneously, the respective lines on the filtrate side can be conveniently combined into a single line, and the detection device, such as a scattered light sensor, can be arranged on the combined line. This means only one detection device is required for multiple filter modules, significantly reducing the equipment required. This also significantly simplifies and accelerates the detection and evaluation of the test.

[0188] According to one embodiment, the filtration device of the invention is part of a virus filtration system, so that both the integrity tests and the virus filtration can be carried out in one and the same filtration device.

[0189] The present invention thus enables simplified and facilitated integrity testing of virus filtration modules. This is all the more true since the integrity test is regularly carried out twice with each virus filtration module, namely once before and once after use of the filter module. These advantages become even clearer when multiple virus filtration modules are used simultaneously for testing and virus filtration. The disclosure is explained and illustrated in detail below with reference to the accompanying drawings, without limiting the disclosure thereto. Reference is made in detail to various embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same or similar reference numerals and symbols are used throughout the drawings to refer to the same or similar parts.The various elements illustrated in the drawings are representative only and are not necessarily drawn to scale. The drawings are intended to illustrate, by way of example only, embodiments of the disclosure of the invention, and one skilled in the art will readily recognize where the drawings have been simplified to illustrate key aspects of the disclosure.

[0190] Figures 1 to 3c have already been explained in the introduction to the description.

[0191] Fig. 4 shows a schematic sectional view of a virus filtration module used according to the invention in the form of a hollow fiber filter module 10. The hollow fiber filter module 10 has a feed side 55, a retentate side 65 and a filtrate side 75 as well as lines connected thereto, i.e. a line 55a which is connected to the feed side 55 of the hollow fiber filter module 10, a line 65a which is connected to the retentate side 65 of the hollow fiber filter module 10 and a line 75a which is connected to the filtrate side 75 of the hollow fiber filter module 10. The hollow fiber filter module 10 has a bundle 50 of hollow fibers, which include, among other things, the hollow fibers 50.1 and 50.2. As can be seen from Fig. 4, the hollow fibers 50.1, 50.2,... are arranged in the filter module 10 and have such an orientation that the hollow fibers 50.1, 50.2,...extend in the vertical direction from the feed side 55 of the filter module 10 to the retentate side 65 of the filter module 10, wherein the hollow fibers 50.1, 50.2,... are also substantially parallel to one another.

[0192] The vertical position shown in Fig. 4 is shown here only to simplify the explanations. Other orientations are possible, such as an intermediate position between a vertical and a horizontal position. As an example, Figure 5 shows an intermediate position of the virus filtration module 10, which is located between a vertical axis V and a horizontal axis H. The virus filtration module 10 is in an (arbitrary) inclined position that deviates more or less significantly from the vertical direction, so that the alignment of the hollow fibers does not run parallel to the axis V. The virus filtration module 10 is not in a exactly upright or vertical position and is also not in a exactly lying, i.e. horizontal, position with the hollow fibers running parallel to the horizontal axis H.

[0193] There are gaps (not shown) between each of the hollow fibers 50.1, 50.2,... In step a) of the test method according to the invention, the virus filtration module 10 is therefore installed in a filtration device in an upright position with vertically extending hollow fibers 50.1, 50.2..., as shown in Fig. 4. Other orientations of the hollow fibers 50.1, 50.2... are possible.

[0194] A filter module 10 is used that is approved for a maximum pressure of up to 98 ± 5 kPa. Applying a higher pressure could destroy the filter module 10. A filter module that can be used for higher pressures is not used according to the invention. Before performing step a), it may be expedient to sterilize the lines 55a, 65a, and 75a, in particular by hot steam sterilization. This is generally performed without a virus filtration module; instead of the virus filtration module, for example, a fitting piece is inserted into the filtration system to close the open section. A fitting piece is, for example, a line adapter. Sterilization (SIP, sterilization in place) can take place, for example, at 100°C or higher, in particular in the range of 100–130°C.This is useful if the integrity test is followed by virus filtration and a sterile product is to be obtained. Following sterilization, the lines can then be pressurized, for example, to approximately 100 kPa, to prevent the introduction of contamination after sterilization. If overpressure is used, the pressure in all lines is reduced before the integrity test is performed, for example, to a pressure of P < 10 kPa, whereby pressure equalization occurs throughout the entire system. This serves to protect the virus filtration module from damage.

[0195] The lines 55a, 65a, and 75a are each constructed, for example, of plastic or metal, particularly stainless steel. It may be advantageous if all lines of the virus filtration module 10 are selected from the same material; however, this is not always necessary.

[0196] In step b) of the method, the virus filtration module 10 and the connected lines 55a, 65a, and 75a are filled with liquid 70 at a constant pressure of no more than 98 ± 5 kPa in three partial steps. Any additional inlets and outlets of the virus filtration module 10 that are not used for the integrity test are closed. An unused outlet of the virus filtration module 10 is shown in Fig. 4 by line 75b on the filtrate side 75 of the filter module 10, which is closed. This can be done, for example, by a valve, a plug, a corresponding clamp, or in another way.

[0197] First, in step b1), all lines 55a and 65a connected to the virus filtration module are filled with liquid 70, but without the virus filtration module 10. In step b2), the inner region of the hollow fibers 50.1, 50.2... of the virus filtration module 10 is filled with liquid 70. This is done by opening the valve 55v of line 55a on the feed side 55 and the valve 65v of line 65a on the retentate side 65, and closing the valve 75v of line 75a on the filtrate side 75. In step b3), the spaces between the hollow fibers 50.1, 50.2... of the virus filtration module 10 are then filled with liquid 70. In this case, either the line 55a on the feed side 55 and the line 75a on the filtrate side 75 are opened and the line 65a on the retentate side 65 is closed.Alternatively, line 65a on the retentate side 65 and line 75a on the filtrate side 75 will be opened and line 55a on the feed side 55 will be closed.

[0198] The liquid 70 used is not particularly limited; this depends on the intended use and intended purpose of the filter module 10. For example, a liquid comprising water, in particular water as the main component, is used. This can also be a water-containing buffer solution. The purity of the water depends on the respective intended use, in particular on the liquid product-containing composition from which the viruses are subsequently to be removed.

[0199] Filling with liquid 70 in steps b2) and b3) can each take place either from the feed side 55 (in Fig. 4 from below) via line 55a or from the retentate side 65 (in Fig. 4 from above) via line 65a. Filling with liquid 70 from the feed side 55 is particularly advantageous because this is generally simpler in terms of process technology and therefore particularly easy to carry out. A further advantage of supplying the liquid 70 from below is that any air present in the filter module 10 is thereby forced upwards out of the filter, so that no more air can remain in the filter. At the same time, complete venting of the filter module 10 is achieved.

[0200] The expression "feed from below" or "from above" or similar formulations does not mean that a filter module 10 must always assume a precisely vertical position. Rather, the filter module 10 can also assume any intermediate position deviating from the vertical orientation, which lies between a vertical position (hollow fibers parallel to a vertical axis) and a horizontal position (hollow fibers parallel to a horizontal axis) (see Fig. 5). Even with a filter module 10 tilted at an angle away from the vertical direction, feeding can occur from below or above.

[0201] The degree of filling of the virus filtration module 10 in steps b2) and b3) can be determined by measuring the pressure before and after the filter module, in Fig. 4, for example, in lines 55a and 65a for step b2) and in lines 55a and 75a for step b3), and determining the pressure difference in each case. At a maximum pressure difference of 98 ± 5 kPa, it can be assumed that the virus filtration module is filled according to step b2) or b3). Alternatively or additionally, the amount of liquid supplied can be determined and related to the dead volume of the lines 55a, 65a, and 75a and the virus filtration module 10, whereby the amount of liquid > dead volume. The dead volume in Fig. 4 would be the volume of the lines 55a, 65a, 75a and the filter module 10 without liquid. This can be determined in each individual case or asked from the manufacturer.

[0202] Accordingly, in Fig. 4, the hollow fiber filter module 10 is completely filled with liquid 70 so that - as far as physically possible - no empty space remains in the filter module 10. In other words, all inner regions of the hollow fibers (e.g., inner region 35 of the hollow fiber 50.1a in Fig. 3b) as well as all spaces between the hollow fibers 50.1, 50.2, ... (e.g., intermediate regions 38.1, 38.2... in Fig. 3b) are filled with liquid 70. Any air present is displaced by the liquid 70, so that the filter module 10 is also vented. The filter module 10 is thus completely filled with liquid 70. The virus filtration module and all lines are almost completely filled by adding the liquid 70 under pressure; the pressure is selected so that it is a maximum of 98 ± 5 kPa. Lower pressure values ​​are also possible. The higher the pressure is set, the more easily the air bubbles in an air bubble chain can be detected.The three arrows A, B, and C in Fig. 4 indicate the respective flow direction when filling the liquid 70 through the hollow fiber filter module 10 for the process alternative according to the invention, according to which the liquid 70 is fed, for example, from the feed side 55 to the filter module 10 in steps b2) and b3). Other process variants are also possible.

[0203] Filling with liquid 70 is mandatory in the three sub-steps described, since otherwise the filter module 10 cannot be completely filled, as already explained.

[0204] As soon as the hollow fiber filter module 10 and the lines 55a, 65a, and 75a are completely filled with liquid, the supply of liquid 70 is stopped and all lines 55a, 65a, and 75a are closed, maintaining the pressure (step c)). The lines 55a, 65a, and 75a are closed using suitable devices known to those skilled in the art. These are, for example, valves 55v, 65v, and 75v provided in the respective lines. Other opening and closing devices are also possible. This results in a closed system completely filled with liquid 70, which remains under the applied pressure.

[0205] Step c) can be followed by an optional intermediate step in which the inner region of the hollow fibers 50.1, 50.2... of the virus filtration module 10 and the connected line, line 55a in Fig. 4, are completely emptied of liquid 70. This can be a particularly gentle procedure for the virus filtration module 10 and protects the module from damage. This has no adverse effects on the subsequent integrity test.

[0206] After step c) or after the optional intermediate step, but before performing step d), a leak test of the entire system, including the virus filtration module, can be performed to rule out any leaks in the system. This serves to ensure that no air escapes from the system, which could compromise the subsequent integrity test and its evaluation. However, since the air flow rate through the filter module 10 is measured during the integrity test, particularly during steps d1) or d2), a leak test can generally be omitted. It is described here only for the sake of completeness.

[0207] During the leak test, air is forced into the system. In Fig. 4, this can be introduced either from the retentate side 65 or from the feed side 55 of the virus filtration module 10. The air pressure is increased step by step from 0 kPa to 70 kPa, for example. 70 kPa then represents the pre-stabilization pressure. After reaching the pre-stabilization pressure, a stabilization period of at least 180 s is observed, during which the air can disperse throughout the system before the leak test is evaluated. If the pressure drop after the stabilization period is < 10 kPa, the leak test is passed. If the pressure drop is > 10 kPa, there is a leak in the filtration system that must be eliminated. Air is then supplied to the virus filtration module using step d1) or d2).In this case, a choice is made between two process alternatives: either step d1) or step d2) is carried out, depending on the line through which the air is supplied to the virus filtration module 10:

[0208] In the first process variant, in step d1), line 55a on the feed side 55 and line 75a on the filtrate side 75 of the filter module 10 are opened, and line 65a on the retentate side 65 is closed or remains closed. Other lines not used for the test, here line 75b on the filtrate side 75 of the filter module 10, remain closed. The selected pressure of a maximum of 98 ± 5 kPa is maintained throughout the integrity test and thus also during step d1). In step d1), air is fed from line 55a on the feed side 55 into the virus filtration module 10 at a constant pressure at the same level as selected for the liquid pressure. For this purpose, a connection (not shown) is provided on line 55a, for example, to force air into line 55a.The injected air has a pressure that is exactly the same as the pressure selected for the liquid 70. For example, a pressure of 98 ± 5 kPa is set for both the liquid and the air. This has the advantage that the chain of air bubbles, if formed, is particularly easy to detect.

[0209] Alternatively, in the second process variant, in step d2), line 65a on the retentate side 65 and line 75a on the filtrate side 75 of the filter module 10 are opened, and line 55a on the feed side 55 is closed, if this has not already been done. Other lines not used for the test, here line 75b on the filtrate side 75 of the filter module 10, remain closed. The selected pressure of a maximum of 98 ± 5 kPa is maintained throughout the entire integrity test and thus also during step d2). In step d2), air is fed into the virus filtration module 10 from line 65a on the retentate side 65 at a constant pressure at the same level as selected for the liquid pressure. For this purpose, a connection (not shown) is provided on line 65a to force air into line 65a.The injected air has a pressure that is exactly the same as the pressure selected for the liquid 70. For example, a pressure of 98 ± 5 kPa is set for both the liquid and the air. This has the advantage that the chain of air bubbles, if formed, is particularly easy to detect.

[0210] In the process according to the invention, therefore – unlike most prior art systems – there is no pressure difference, but rather the same pressure of a maximum of 98 ± 5 kPa is present everywhere. Surprisingly, a transmembrane pressure is not required. Setting a pressure difference is generally disadvantageous because an exact pressure difference cannot be set precisely; there will always be a fluctuation range (comparable to the speed setting in cruise control). It is suspected that fluid mechanics plays a role in this; adhesion processes are of only minor importance at best. The integrity test can also be carried out at low pressures of 10 ± 0.5 kPa or 20 ± 1 kPa, since tests have shown that a continuous chain of air bubbles can be detected in this case too. In process steps d1) and d2), air is thus pressed into the filter module 10.This air is used to determine whether the hollow fibers in the filter module 10 are intact, i.e., whether they exhibit no damage, such as cracks, and therefore fulfill the desired filtering function. If the filter module is functioning properly, the air is retained inside the hollow fibers 50.1, 50.2... because the air cannot penetrate the hollow fiber wall. The incoming air is therefore forced via the selected filter inlet of the virus filtration module 10 through the contained hollow fibers 50.1, 50.2... to the filter outlet. In this case, the filter inlet is the side of the filter module 10 through which the air is introduced; the filter outlet is the side of the filter module 10 through which the air should actually exit again if the hollow fibers are intact.

[0211] If the air is pressed into the virus filtration module 10 from below via line 55a, the air escapes at line 65a if the virus filtration module 10 is intact. Since a closed system exists, the air is distributed between line 55a, filter module 10 and line 65a. If the air is pressed into the virus filtration module 10 from above via line 65a, the air escapes at line 55a if the virus filtration module 10 is intact. Since a closed system exists, the air is also distributed between line 55a, filter module 10 and line 65a in this case. If a non-functional filter module 10, the air escapes through damages in the hollow fiber wall and thus reaches the filtrate side 75 and thus into line 75a of the filter module 10, where a chain of air bubbles then occurs and can be detected in line 75a. At the same time, the volume flow of the air orThe maximum volume flow (Volmax) of the air through the filter module 10 is measured using a measuring device (not shown). The volume flow of the air must not exceed 8 mL / min for a functioning filter module 10. Therefore, a distinction is made between the following cases when testing filter module 10:

[0212] Volmax is above 8 mL / min + air bubble chain > 20s or

[0213] Volmax is maximum 8 mL / min + air bubble chain > 20s or

[0214] Volmax is over 8 mL / min + air bubble chain < 20s.

[0215] In these three cases, the filter module 10 is not functional and contains a defect.

[0216] Volmax is maximum 8 mL / min + air bubble chain < 20s.

[0217] In this case, the filter module 10 is functional and does not contain any defects.

[0218] In this context, it should be noted that the assumption that the maximum volume is 8 mL / min or less + the air bubble chain is > 20 s cannot occur. This would indicate a medium to large defect (air bubble chain > 20 s), which would not be detected by the volume flow measurement, which detects even the smallest defects. This case is presented only to illustrate all (theoretically conceivable) test variants. This case has no practical significance.

[0219] The second process alternative, according to which the air is injected into the virus filtration module 10 from above via line 65a, has proven particularly advantageous, especially when air is introduced from the highest point of the filter module 10. The air used is not particularly limited. It is understood that it should not contain any components that could impair the virus filtration module 10 or the integrity test in any way. In particular, process air is used.

[0220] According to one embodiment, the air used in process steps d1) or d2) is first passed through an air filter (not shown in Fig. 4, but shown in Figs. 5a and 5b) before it can enter the hollow fiber filter module 10, in order to retain potential contaminants from the air so that they do not contaminate the filter module 10. It has been determined that the test procedure is not impaired by such an air filter.

[0221] 6a and 6b show a simplified schematic view of a virus filtration module in the form of a hollow fiber filter module 10 with connected lines, as well as the relative position of an air filter 85 to the hollow fiber filter module 10. Fig. 6a shows an exemplary embodiment in which the virus filtration module 10 as a whole and its lines 55a, 65a, and 75a are already completely filled with liquid (steps b1), b2), and b3). In the example shown, the liquid 70 was supplied to the filter module 10 from below, i.e., through the valve 55v and via the line 55a. Alternatively, the liquid 70 could also be supplied to the filter module 10 from above, i.e., through the valve 65v and via the line 65a. The valves 55v, 65v, and 75av in Fig. 6a were closed after filling; Valves 75bv and 85v were already closed before filling. This system is therefore self-contained.

[0222] For simplicity, the virus filtration module is always shown in the figures in a vertical position. However, this is not required in practice. The virus filtration module can be installed in any orientation in a filtration device.

[0223] In the example shown, the air is now to be supplied from below via line 55a. For this purpose, valve 85v is opened so that liquid 70 located in line 55a can flow into line 85a. In the example shown, air filter 85 is arranged above filter module 10. The fact that air filter 85 is located entirely above filter module 10 simply prevents liquid 70 from rising from liquid-carrying line 55a via line 85a to air filter 85, potentially impairing its function.

[0224] Alternatively, it would be sufficient if the air-conducting line 85a leading from the air filter had a section that encompassed the highest point of the filtration device. Then, the air filter 85 could be arranged next to or below the virus filtration module 10. This would ensure that liquid 70 cannot rise to the air filter 85 and penetrate it.

[0225] In Fig. 6b, in the example shown, the air is now supplied from above via line 65a. For this purpose, the valve 85v is opened so that liquid 70 located in line 65a can enter line 85a. To prevent this, the air filter 85 is arranged entirely above the filter module 10 in Fig. 6b, so that the liquid 70 from the liquid-carrying line 65a cannot rise via line 85a to the air filter 85 and possibly impair its function. According to a further embodiment, the air-carrying line 85a leading from the air filter could also have a section that encompasses the highest point of the filtration device. In this case, the air filter 85 could also be arranged below the virus filtration module 10. This prevents liquid 70 from rising to the air filter 85 and penetrating it.

[0226] After or during step d) and before step e) is performed, according to one embodiment, a certain period of time can be allowed to elapse during which the air continues to be supplied and can be further distributed throughout the system. This is the so-called stabilization time, which can be up to 600 seconds. However, this can also simply be omitted.

[0227] As shown schematically in Fig. 4, one of the two process alternatives d1) or d2), optionally after a stabilization time of up to 600 s, is followed by step e), i.e., an automatic detection of a chain of air bubbles that may occur on the filtrate side 75 of the filter module 10 in line 75a. Step e) takes place while steps d1) or d2) are still being performed. At the same time, the volume flow of air through the virus filtration module 10 is measured using a measuring device (not shown).

[0228] The detection of a possible defect in the virus filtration module 10 based on the occurrence of a chain of air bubbles is advantageously carried out optically. For example, a scattered light sensor 120 is used, as schematically illustrated in Fig. 4 in the form of two rectangles. The sensor 120 measures the light scattering (lateral scattering) and is generally constructed from a light source and one or more detectors for detecting the light after it has passed through the line 75a and the liquid contained in the line, which may contain a chain of air bubbles. For example, light in the near-infrared range with a wavelength in the range of 730 to 970 nm is emitted by a light source of the sensor 120, passes through the liquid-filled line 75a, and is absorbed by the air bubbles of an air bubble chain present in the liquid.The light emerging from line 75a can be detected again, for example, by a detector such as a photocell, photodiode, or the like, and a measured value can be determined from it. The scattered light sensor 120 therefore measures the changed absorption of the light when a chain of air bubbles occurs.

[0229] At the position where the air bubble chain is detected, in particular at the location of detection or measurement, the line 75a on the filtrate side 75 is at least partially transparent. In Fig. 4, the location of detection or measurement is the part of the line 75a located between the individual components of the scattered light sensor 120 (symbolized by two rectangles). Since the air bubble chain is detected optically in the embodiment shown, at least those sections of the line 75a on the filtrate side 75 that are located in the beam path of the light used are selected to be transparent.

[0230] According to one embodiment, a transparent tube or two transparent sections in the form of two windows are used for the line 75a, each of which is selected in its dimensions so that it does not obstruct the beam path of the incoming and outgoing light in the sensor 120, so that the light can pass through unhindered.

[0231] Transparent materials that could be considered have already been described. The thickness of the transparent material depends on its type and composition. For example, it can be a few millimeters or even a few centimeters thick to withstand the desired pressure.

[0232] If two transparent windows are used, both are made of the same material and both have the same strength (= thickness).

[0233] An exemplary setup for scattered light measurement using a scattered light sensor 120 is illustrated in Fig. 7 in a simplified form in a partial sectional view. It shows a section through line 75a, filled with liquid 70, on the filtrate side 75 of the virus filtration module 10. The liquid 70 is located in line 75a at the selected pressure. A light source 120.1, for example, a tungsten lamp, emits light L of the desired wavelength, which is, for example, in the range from 730 to 970 nm. In the line 75a, at the location of the measurement, ie in the path of the light L to be measured, a transparent section in the form of windows 78.1 and 78.2 is provided on the two opposite sides of the line 75a, so that the light emitted by the light source 120.1 passes through the first window 78.1 into the liquid-filled line 75a and then exits the line 75a again through the second window 78.2.The material of the windows 78.1, 78.2 is made, for example, of borosilicate glass, such as Pyrex®, or of sapphire. The windows 78.1 and 78.2 close the openings 77.1 and 77.2 of the line 75a and simultaneously cover them. Seals 79.1, 79.2, 79.3, and 79.4 are also provided to seal the line 75a.

[0234] If a chain of air bubbles 130 in the liquid 70 of the line 75a now travels through the beam path of the light L, the light L is absorbed and scattered accordingly (light rays L1, L2, and L3), which is detected by the detectors 120.2, 120.3, and 120.4 shown as examples. These are, for example, photodiodes. The precise optics in the beam path of the light L before and after passing through the line 75a, with various lenses and the like, are not shown in Fig. 7 and are known to those skilled in the art. For example, commercially available scattered light sensors, in particular known turbidity sensors, can be used.

[0235] The scattered light sensor 120 is therefore attached to the filter outlet on the filtrate side 75 of the virus filtration module 10 and detects an air bubble chain 130 occurring in the line 75a.

[0236] In addition to checking whether a continuous chain of air bubbles occurs, the volume flow of air through the virus filtration module 10 is measured.

[0237] The result of the integrity test then serves as a criterion for assessing a later release of the virus filtration module 10 for virus filtration. If the virus filtration module 10 is intact, the air flow rate of the virus filtration module 10 does not exceed the limit of 8 mL / min, and the scattered light sensor 120 does not detect a corresponding absorption signal for an air bubble chain on the filtrate side 75 of the filter module 10. If the virus filtration module 10 is not intact, the air flow rate of the filter module 10 exceeds the limit of 8 mL / min, and the scattered light sensor 120 may also detect an absorption signal for an air bubble chain on the filtrate side 75 of the filter module 10.

[0238] The evaluation of the detection, in particular the scattered light measurement and the measurement of the air volume flow, is carried out in step f) in particular also automatically based on the specifications for the integrity test, namely that an air bubble chain is present for at least 20 s or not and that the air volume flow exceeds 8 mL / min per virus filtration module or not. According to one embodiment, the scattered light sensor 120 and the measuring device (not shown) for the air volume flow are integrated into an internal process control system (PCS) (not shown) and report within an ongoing test program whether the defined acceptance criteria for passing the integrity test were met or not.

[0239] For example, the process control system may be part of a process filtration device in which integrity tests and virus removal can be performed with the virus filtration module 10.

[0240] Figures 8 and 9 each illustrate schematic sectional views of a section of a filtration device 100 according to further embodiments of the invention, in each of which both the integrity test and virus filtration can be performed. Furthermore, several virus filtration modules can be tested simultaneously in the filtration device 100 using the method according to the invention.

[0241] In detail, Fig. 8 shows a section of a filtration device 100 in which both the integrity tests with the virus filtration modules and virus filtration can be carried out. Three virus filtration modules are shown, each in the form of hollow fiber filter modules 10.1, 10.2, and 10.3 in the installed state, in which the hollow fibers are oriented such that they run in a vertical direction (step a)). Of course, more than the three virus filtration modules shown as examples can also be provided. This depends on the type and size of the filtration device and the virus filtration to be performed.

[0242] The vertical orientation was chosen for simplification and clarity only. Of course, any other position can be selected, such as any intermediate position between vertical and horizontal orientation (see Fig. 5).

[0243] The virus filtration modules 10.1, 10.2, and 10.3 each have a feed side 55.1, 55.2, and 55.3, a retentate side 65.1, 65.2, and 65.3, and a filtrate side 75.1, 75.2, and 75.3. Each filter module 10.1, 10.2, and 10.3 is connected to lines 55.1a, 55.2a, and 55.3a on the feed side, lines 65.1a, 65.2a, and 65.3a on the retentate side, and lines 75.1a, 75.2a, and 75.3a on the filtrate side. Another line on the filtrate side of each virus filtration module 10.1, 10.2, 10.3 has been omitted for the sake of clarity.

[0244] The material of the pipes is not particularly limited; in Fig. 8 the pipes are made of stainless steel.

[0245] To perform the integrity test, a liquid 70 is used, in the example shown ultrapure water, in particular WFI water (WFI, water for injection), and the virus filtration modules 10.1, 10.2, and 10.3, which are arranged in parallel, and all connected ultrapure water lines have already been filled with liquid 70 (steps b1), b2), and b3). This can be carried out analogously to Fig. 4, but for all three virus filtration modules 10.1, 10.2, and 10.3 and all connected lines simultaneously. According to the invention, the water 70 can be supplied either from below through lines 55.1a, 55.2a, and 55.3a on the feed side or from above through lines 65.1a, 65.2a, and 65.3a on the retentate side. The terms “from above” or “from below” should be understood as broadly as possible and can, for example, also refer to another intermediate position of the virus filtration modules 10.1, 10.2, 10.3, as already explained for a virus filtration module in connection with Fig. 5. In the embodiment shown in Fig. 8, the water 70 is supplied from below through the valve 55v via the lines 55.1a, 55.2a and 55.3a.

[0246] For procedural reasons, it is expedient if the water 70 is supplied from the same side for all virus filtration modules 10.1, 10.2, and 10.3 tested simultaneously, from the bottom for all virus filtration modules in Fig. 8. Alternatively, the water 70 could also be supplied from the top for all virus filtration modules.

[0247] Inlet filters (not shown) can be provided in each of the lines 55.1a, 55.2a, and 55.3a for supplying water 70 to remove possible impurities from the water before it enters the filter module. The water 70 is supplied at a pressure of no more than 98 ± 5 kPa in three partial steps—as already explained—so that all internal areas of the hollow fiber, all spaces between the hollow fibers, and all connected lines on the virus filtration modules 10.1, 10.2, and 10.3 are filled with water 70. The pressure range is selected within a range that does not adversely affect the virus filtration modules 10.1, 10.2, and 10.3.

[0248] As soon as the virus filtration module 10.1, 10.2, and 10.3 and the respective lines 55.1a, 55.2a, and 55.3a; 65.1a, 65.2a, and 65.3a; and 75.1a, 75.2a, and 75.3a are completely filled with water 70, the supply of water 70 is stopped (step c)) and all lines are closed. To do this, the valves on the feed side 55.1v, 55.2v, and 55.3v, the valves on the retentate side 65.1v, 65.2v, and 65.3v, and the valves on the filtrate side 75.1v, 75.2v, and 75.3v are each closed. This creates a closed system completely filled with water 70, which remains under the applied pressure of a maximum of 98 ± 5 kPa. In a subsequent optional intermediate step, the water 70 can be completely drained from the interior of each virus filtration module 10.1, 10.2, and 10.3 and the associated lines 55.1a, 55.2a, and 55.3a. This serves to additionally protect modules 10.1, 10.2, and 10.3 from damage.This intermediate step can also be omitted.

[0249] A leak test (pressure maintenance test) of the lines of the filtration device 100 and the installed virus filtration modules 10.1, 10.2, and 10.3 can then follow. For this purpose, air is forced into the virus filtration modules either from below or from above, and the corresponding liquid-filled lines on each virus filtration module are opened. If air is supplied from above, lines 65.1a and 75.1a on virus filtration module 10.1, as well as the analogous lines on the other two virus filtration modules 10.2 and 10.3, are opened. Alternatively, if air is supplied from below, lines 55.1a and 75.1a on virus filtration module 10.1, as well as the analogous lines on the other two virus filtration modules 10.2 and 10.3, are opened. The system's unused inlets and outlets for water (valve 55v) and air (valve 75v) are closed. Air is then forced into the virus filtration modules either from above or below.In Fig. 8, this would take place from below from the feed side via lines 55.1a, 55.2a and 55.3a into the virus filtration modules 10.1, 10.2 and 10.3 at the same pressure as the water pressure, whereby the air pressure is increased step by step from 0 kPa to a pre-stabilization pressure of, for example, 70 kPa. After an optional stabilization time of, for example, at least 180 s, it is determined whether the pressure drop is < 10 kPa. If this is > 10 kPa, there is a leak in the filtration system that must be eliminated. However, since the air volume flow is also measured during the integrity test, in particular while steps d1) or d2) are still ongoing and step e) is being carried out, the leak test is superfluous and can be omitted. It is explained here for illustrative purposes only.

[0250] In the following step d), air is injected into the virus filtration modules 10.1, 10.2, 10.3; this occurs either from below (step d1)), in each case through the line on the feed side, or from above (step d2)), in each case through the line on the retentate side of each virus filtration module 10.1, 10.2, 10.3. In the embodiment shown in Fig. 8, the air 80 is injected from below according to step d1) of the method according to the invention. If a leak test is to be carried out, it is expedient if the air is then introduced from below, as also occurs in step d).

[0251] Specifically, according to step d1), the lines on the feed side of each virus filtration module and the lines on the filtrate side are opened and the other lines remain closed, maintaining the pressure (as specified in step b)) to supply air at a constant pressure at the same level as the water pressure from the line on the feed side (from below) into the virus filtration module. In Fig. 8, therefore, the lines 55.1 a, 55.2 a and 55.3 a on the feed side 55.1 , 55.2 and 55.2 (respectively at the lower end of the virus filtration module 10.1 , 10.2 , 10.3) and the lines 75.1 a, 75.2 a and 75.3 a on the filtrate side 75.1 , 75.2 and 75.3 of the filter module 10.1 , 10.2 and 10.3 (at the side wall of the filter module 10.1 , 10.2 and 10.3) are each opened and the line 65.1 a, 65.2 a and 65.3 a on the retentate side 65.1 a, 65.2 a and 65.3 a (at the upper end of the filter module 10.1, 10.2 and 10.3) remain closed.Opening the lines does not cause a pressure drop. Rather, the pressure remains constant throughout the entire test procedure at the pressure value used for the test procedure, which was selected from a range of 98 ± 5 kPa or less.

[0252] The lines can be opened and closed using devices known to those skilled in the art. Valves are shown in Fig. 8; other possibilities are conceivable.

[0253] After opening the lines on the feed side and the lines on the filtrate side, air 80 is fed via the valves 85v1 and 85v2 into the lines 55.1a, 55.2a and 55.3a, which are each located on the feed side

[0254] 55.1, 55.2, and 55.2 of the virus filtration modules 10.1, 10.2, and 10.3, at a constant pressure of no more than 98 ± 5 kPa. The air pressure is set to the same level as the previously set water pressure.

[0255] In Fig. 8, according to one embodiment, the air 80 is first passed through an air filter 85 to remove contaminants from the air so that they cannot enter one of the filter modules 10.1, 10.2, and 10.3. The air filter 85 is arranged above the virus filtration modules 10.1, 10.2, and 10.3. Alternatively, the air-conducting line 85a leading from the air filter 85 could have a section that encompasses the highest point of the filtration device, so that no water can rise to the air filter 85, even if the air filter 85 is not arranged above the virus filtration modules 10.1,

[0256] 10.2, 10.3. Other embodiments are also possible. The fact that the air filter 85 or a section of the air-conducting line is located above the filter modules 10.1, 10.2, 10.3 simply prevents water from the water-conducting line 55a from rising to the air filter 85 and potentially impairing its function.

[0257] The provision of an air filter 85 does not affect the process in any way.

[0258] The air 80 used is not particularly limited, in particular process air is used.

[0259] During the execution of step d), the total volume flow of the air is additionally measured with a measuring device (not shown) through the filter modules 10.1, 10.2, 10.3.

[0260] In step e) of the method according to the invention, which is carried out while steps d1) or d2) are still being carried out, an automatic detection of an air bubble chain takes place when it occurs (symbolized by the dashed arrow 80, top left in Figure 7). In addition, the volume flow is measured in steps d1) or d2) and thus also in step e), since step e) is carried out while steps d1) or d2) are continued. The detection of an occurring air bubble chain takes place in Fig. 8 with the aid of a scattered light sensor 120, which measures the absorption. At the same time, the total volume flow in steps d1) or d2) and the simultaneously occurring step e) is recorded, in particular automatically. If the virus filtration modules 10.1, 10.2 and 10.3 are intact, i.e.If the hollow fibers do not exhibit any damage, such as cracks, and therefore fulfill the desired filtering function, the air 80 remains in the hollow fibers because the air 80 cannot penetrate the pores of the hollow fiber wall. A chain of air bubbles is not detected by the scattered light sensor 120 in the conduit 75a on the filtrate side 75.1, 75.2, 75.3, which is combined into one line. The volume flow of the air 80 is a maximum of 8 mL / min per virus filtration module 10.1, 10.2, and 10.3.

[0261] If one or more of the virus filtration modules 10.1, 10.2, and 10.3 are not intact, i.e., if there is damage such as cracks, and therefore the desired filter function is not fulfilled, the air 80 passes through the damage in the hollow fiber wall and thus reaches the filtrate side 75.1, 75.2, and 75.3 of the filter module 10.1, 10.2, and 10.3, where a chain of air bubbles then occurs in the respective line 75.1a, 75.2a, or 75.3a. At the same time, the measured volume flow of the air 80 is above 8 mL / min for at least one of the virus filtration modules 10.1, 10.2, and 10.3. If only very minor damage is present, no air bubble chain is usually detected, but the measured air flow rate 80 is then above 8 mL / min for at least one of the virus filtration modules 10.1, 10.2 and 10.3 and indicates a defect.

[0262] According to the embodiment shown, lines 75.1a, 75.2a, or 75.3a on the filtrate side 75.1, 75.2, 75.3 are combined into a single line 75a, where detection is performed optically, in particular by a scattered light sensor 120. For measuring the (total) air volume flow, only one measuring device (not shown) can be present for all virus filtration modules 10.1, 10.2, and 10.3. This requires only one detection device and only one measuring device for the total air volume flow, which significantly simplifies and accelerates the detection and evaluation of the test. If one or more of the virus filtration modules 10.1, 10.2 and 10.3 are not intact, a continuous chain of air bubbles is then detected in the sensor 120 for a duration of at least 20 seconds and the measured volume flow of the air 80 is above 8 mL / min for at least one of the virus filtration modules 10.1, 10.2 and 10.3.

[0263] According to the illustrated embodiment, the scattered light sensor 120 is arranged here on a part of the line 75a running from bottom to top, so that a chain of air bubbles in the line can be detected particularly well and completely as they rise.

[0264] Even when a virus filtration module 10.1, 10.2, and 10.3 is completely intact, tests have shown a minimal loss of injected air 80 (so-called creep flow) after passing through the filtration module 10.1, 10.2, and 10.3. However, this is irrelevant for the integrity test.

[0265] After passing through the filter modules 10.1, 10.2, and 10.3, the air 80 can be disposed of and collected, for example, in a waste collection container (not shown). In the illustrated embodiment of Fig. 8, two sapphire glass windows 78.1 and 78.2 are installed for optical measurement, which are arranged in the beam path of the sensor 120 in the line 75a.

[0266] It is expedient to provide an additional outlet filter (not shown) at the filter outlet in lines 75.1a, 75.2a and 75.3a on the filtrate side 75.1, 75.2 and 75.3, which removes potential impurities so that the scattered light sensor 120 does not detect absorption signals from undesired components and the measurement is not impaired.

[0267] The detection (step e)) by the scattered light sensor 120, the measurement of the air volume flow, and also the evaluation (step f)) are carried out in particular in a fully automated manner, for example using a computer program in the form of a process control system (DCS) (not shown) into which the scattered light sensor 120 is integrated. In Fig. 8, the process control system is part of a process filtration device in which virus removal can be carried out. In the filtration device shown in the section, the two integrity tests and the virus filtration are therefore carried out: An integrity test (pre-visual leak test) of the virus filtration modules 10.1, 10.2 and 10.3 is carried out before the virus filtration and an integrity test (post-visual leak test) of the virus filtration modules 10.1, 10.2 and 10.3 is carried out after the virus filtration, without it being necessary to install and remove the virus filtration modules 10.1, 10.2 and 10.3 for the tests.The functional testing of the filtration and the actual filtration for virus filtration modules 10.1, 10.2, and 10.3 therefore take place in the filtration device shown. This significantly reduces the risk of potential damage or contamination to the modules.

[0268] The embodiment illustrated in Fig. 8 has the advantage that the time required for each test for each filter module can be significantly reduced. Multiple filter modules can be tested simultaneously, resulting in significant time savings, particularly with an automated test procedure. This can be particularly important for large-scale industrial applications.

[0269] If a defect is detected during simultaneous testing of virus filtration modules 10.1, 10.2, and 10.3, each virus filtration module is tested individually. For this purpose, the process steps are performed only on one virus filtration module, e.g., virus filtration module 10.1, while the lines for the other virus filtration modules, e.g., 10.2 and 10.3, are kept closed. If the defective virus filtration module is identified, it is replaced, and the process according to steps b) to e) is repeated with all virus filtration modules.

[0270] Fig. 9 illustrates a further embodiment of the present invention. Insofar as the same explanations apply as for Fig. 8, a corresponding repetition will be omitted. In particular, as in Fig. 7, the water 70 is supplied from below (from the feed side 55.1, 55.2 and 55.3 of the virus filtration modules 10.1, 10.2 and 10.3). In contrast to Fig. 8, however, in Fig. 9 the air 80 is not supplied from below, but from above (from the retentate side 65.1, 65.2 and 65.3 of the virus filtration modules 10.1, 10.2 and 10.3). The terms “from below” or “from above” are to be interpreted as broadly as possible, as has already been explained in detail. In detail, in the embodiment illustrated in Fig. 9, after carrying out steps a), b), c) and, if appropriate, the optionally carried out intermediate step and a leak test, which are carried out as explained by way of example in Fig. 8, step d2) is carried out.In step d2), for each virus filtration module, the lines on the retentate side and the lines on the filtrate side are opened and the lines on the feed side are closed, maintaining the pressure to supply air at a constant pressure equal to the water pressure from the lines on the retentate side (from above) into the virus filtration module. In detail, in Fig. 9 the lines 65.1 a, 65.2a and 65.3a on the retentate side 65.1 , 65.2 and 65.3 (at the upper end of the virus filtration modules 10.1 , 10.2 and 10.3) and the lines 75.1 a, 75.2a and 75.3a on the filtrate side 75.1 , 75.2 and 75.3 of the respective filter modules 10.1 , 10.2 and 10.3 are opened and the lines 55.1 a, 55.2a and 55.3a on the feed side 55.1 , 55.2 and 55.3 (at the lower end of the filter modules 10.1 ,.

[0271] 10.2 and 10.3) remain closed.

[0272] Opening the lines does not cause a pressure drop. Rather, the pressure remains constant throughout the entire test procedure at the pressure value used for the test procedure, which was selected from a range of 98 ± 5 kPa or less.

[0273] The lines can be opened and closed using devices known to those skilled in the art. Valves are shown in Fig. 9; other options are conceivable.

[0274] After opening the lines on the retentate side and the lines on the filtrate side, air 80 is supplied via valves 85v1 and 85v2 into lines 65.1a, 65.2a, and 65.3a, which are located on the retentate side 65.1, 65.2, and 65.2 of the virus filtration modules 10.1, 10.2, and 10.3, at a constant pressure of no more than 98 ± 5 kPa. The air pressure is set to the same level as the previously set water pressure.

[0275] In Fig. 9, according to an embodiment - as in Fig. 7 - the air 80 is first passed through an air filter 85 to remove impurities from the air so that they do not enter one of the filter modules

[0276] 10.1, 10.2, and 10.3. The air filter 85 is located above the virus filtration modules 10.1, 10.2, and 10.3.

[0277] The volume flow of air 80 through the virus filtration modules 10.1, 10.2 and 10.3 is measured during step d2).

[0278] In step e) of the method according to the invention, an air bubble chain is automatically detected when it occurs (symbolized by the dashed arrow 80, top left in Figure 8). The detection takes place in Figure 9 with the aid of a scattered light sensor 120, which measures the absorption. Further details are explained in Figure 8. Step e) takes place in particular while step d2) continues to be carried out, so that simultaneously with the automatic detection of the air bubble chain, the volume flow of the air 80 is also measured, as already explained in Figure 8. The present disclosure thus provides for the first time a partially or fully automated method or a corresponding filtration device for an integrity test, with which the test can be carried out reliably, reproducibly, and simply.

[0279] The method of the disclosure is further illustrated below by means of examples, without limiting the disclosure thereto.

[0280] Examples of implementation

[0281] The process of the present invention is explained in detail in the examples using various embodiments.

[0282] Example 1 :

[0283] Visual Leak Test (VLT) for a virus filtration module

[0284] 1 . Preparation of the filtration unit and the filter modules: a. First, the required media connections were made on the filtration unit. These included, for example, all hose connections for the required liquid inlets and outlets. This also included the supply of process air and the provision of electricity, e.g. for measuring devices, sensors and the like to operate the filtration unit. The liquids used can be, for example, water or a buffer solution comprising water. The liquid used in Example 1 was an aqueous acetic acid / acetate buffer solution b. All lines and line connections were first subjected to hot steam sterilization at up to 130 °C, since virus filtration was to be carried out following the visual leak test. For this purpose, instead of a virus filtration module, a fitting piece was used to close the open section in the filtration device.The piping system was then pressurized to approximately 100 kPa to prevent the entry of contaminants. Finally, the pressure was reduced to a pressure P < 10 kPa, with pressure equalization occurring throughout the system. At all points in the system that influence the filter module, the pressure after this process was therefore P < 10 kPa. This was done to protect the virus filtration module from damage. c. The filter module was installed in the filtration unit with the hollow fibers running vertically (the retentate side of the filter module was on top, the feed side was on the bottom, as shown in Fig. 3a). The number of filter modules is flexible depending on requirements. In this example 1, a virus filtration module manufactured by Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, was installed.

[0285] 2. Filling the filtration unit including the previously installed filter module: a. First, the lines in the filtration unit were filled without the installed filter module using an internal process control system (PCS) program. To do this, the corresponding valves on the filter module were closed. This prevents possible damage to the modules. The selected pressure was < 98 ± 5 kPa. It was then checked that there were no more air bubbles in the outflowing liquid, as the line system was then completely filled. This can be done visually by an employee or with a sensor. In Example 1, this was done visually. b. The filter module was filled starting with the inner area of ​​the hollow fibers, i.e. the “hollow fiber interior,” being filled from the feed side (from below). In Fig. 1, this corresponds to the supply of liquid starting from A to B. According to Fig.3a, fluid was therefore fed via the inlet at 55 of the filter module to the outlet at 65. The outlets at 75o + 75u were each closed with valves. The goal was to completely fill the "hollow fiber interior." As a parameter to verify complete filling, the differential pressure across the filter module was determined at 98 kPa ± 5 kPa. The differential pressure was determined using two pressure gauges, one before and one after the filter module, with the difference between the two pressures being measured. If the pressure before and after the filter module is approximately the same, the filter module is completely filled. Another parameter was the attainment of the dead volume. The dead volume is considered the volume of the entire piping system, including all filter modules used (here: one filter module). This depends on the specific system, the type, and number of filter modules, and can easily be determined by a specialist in each individual case or requested from the manufacturer.The used 4 m. 2 -Filter module had a dead volume of 1,900 mL according to the manufacturer's specifications. c. The filling of liquid into the filter module, specifically the spaces between the hollow fibers, began from the feed side (from below). In Fig. 1, this corresponds to from A through the filter module to C. According to Fig. 3a, liquid was therefore fed from the inlet at 55 of the filter module to the outlet at 75o of the filter module. The outlet at 65 (and 75u) remained closed. The aim was to fill the entire piping system and the filter module as completely as possible with liquid. The differential pressure across the filter module at 98 kPa ± 5 kPa and the achievement of the dead volume were again used as parameters to check whether the spaces in the filter module were completely filled.

[0286] 3. Optional emptying of the inner area of ​​the filter module:

[0287] For this purpose, the liquid in the inner region of the hollow fibers was removed again. To do this, valve 55v was opened using the PLS program as shown in Fig. 6b, allowing the buffer solution to flow out of the filter module via line 55a until the inner region of the hollow fibers and the connected line 55a were completely emptied. Additionally, as shown in Fig. 6b, the inlet at line 65a was opened, and the filter module was ventilated via path 85a by opening valve 85v via the air filter 85. The parameter used is that no more liquid escapes from the outlet of the filtration unit. This can be done by trained employees through visual inspection or via a sensor using the PLS program. In this example, this was done visually.

[0288] This optional step is not always necessary. This step has the advantage that emptying the inside of the virus filtration module is a particularly gentle procedure for the subsequent visual leak test. Filling the inner area of ​​the hollow fibers with liquid and then subjecting them to gas for the visual leak test could cause the hollow fibers to expand further, further increasing the stress on the filter module.

[0289] 4. Visual Leak Test (VLT): a. Leak test of the filtration system: Before starting the visual leak test, a leak test can be performed on the filtration system and the installed filter module to rule out any leaks in the system, e.g., due to an improperly installed seal. Although this is not necessary due to the measurement of the process air volume flow, it is described here for the sake of completeness and to illustrate the procedure using an example. The leak test was conducted using a PLS program. A PLS program is useful because, in addition to a continuous air bubble chain with the scattered light measurement, the total volume flow of process air through the filtration system can also be reliably measured during the visual leak test.The leak test (also known as pressure hold test) is designed to ensure that no air escapes from the system, which could interfere with the subsequent integrity test and its evaluation.

[0290] According to the PLS program part 1, valves 85.1v, 85.2v, 65.1v, and 75.1v were opened analogously to Fig. 9, but only for one virus filtration module (module 10.1). Valve 55.1v remained closed because the air was to be injected from the retentate side (from above). The unused inlets and outlets at valves 55v and 75v of the system were closed. Another outlet on the filter module, not shown in Fig. 9 (see Fig. 3a: outlet at 75u), was also closed on the filter module. In this example, the process air was therefore supplied to the virus filtration module from the retentate side (from above). A gradual pressure buildup took place by means of a controlled pressure increase (so-called fixed ramp), which was achieved using process air until the test pressure (also referred to as pre-stabilization pressure) was reached. In this example, the pressure in the system was increased from 0 kPa to 70 kPa. The pre-stabilization pressure was thus 70 kPa.A stabilization time of 180 seconds was chosen. The stabilization time was the time during which the process air could disperse throughout the system before the leak test was evaluated. The leak test is considered passed if the pressure drop after the stabilization time is < 10 kPa, especially < 5 kPa.

[0291] After the optional leak test, the PLS program evaluated whether the pressure drop during this period (< 10 kPa) was maintained or not:

[0292] Pressure drop: < 10 kPa:

[0293] If the pressure drop is below the maximum permissible pressure drop, it must be assumed that there is no leak in the filtration system. In this case, the PLS program continues to run according to point 4b.

[0294] Pressure drop > 10 kPa

[0295] If the pressure drop exceeds the maximum permissible pressure drop, it must be assumed that there is a leak in the system. In this case, the PLS program is terminated, the leak in the filtration system is located and eliminated, and the PLS program is restarted at point 4a by repeating the program.

[0296] In Example 1, the pressure drop was < 10 kPa; the filtration system therefore passed the leak test. The visual leak test as per point 4b could be carried out. b. Carrying out the visual leak test: According to the PLS program, Part 2, analogous to Fig. 9, but using only one filtration module (here: module 10.1), the outlet at valve 75v of the filtration system was opened in addition to the already opened valves 85.1v, 85.2v, 65.1v, and 75.1v. The unused inlets and outlets (here: at valve 55v) in the filtration system and valve 55.1v on the filter module were closed. A filter module outlet not shown in Fig. 9 for reasons of clarity (see, for example, the outlet at 75u in Fig. 3a) was also closed. The process air was supplied to the virus filtration module from the retentate side (from above). The existing pressure was further increased with process air (so-called "pressure booster").Continuation of the ramp) until the final test pressure of 98 ± 5 kPa was reached. After a stabilization period, continuous evaluation was carried out during the test period, with the detection of a visible chain of air bubbles and the measurement of the volume flow of process air flowing into the system.

[0297] The parameters for the PLS program part 2 were as follows:

[0298] The stabilization time was 600 seconds: This was the time during which the process air could continue to circulate throughout the system before the evaluation began in the PLS program. The start of the evaluation corresponded to the end of reaching the test pressure.

[0299] The test pressure was 98 ± 5 kPa: this was the pressure at which the filtration system was subjected to process air during the test period.

[0300] The test period was 300 seconds: This was the period during which the test pressure was maintained at a constant level and the continuous monitoring of the presence of process air was detected by the scattered light sensor (see Fig. 7). In addition, the amount of process air, or more precisely, the volume flow of process air flowing into the system, was continuously recorded by the DCS.

[0301] The measured maximum permissible air flow rate (Volmax) can be up to 8 mL / min per filter module: This represents the maximum permissible air flow rate during the test period. It is an expected value for the maximum air flow rate for an intact filter module. Experience has shown that the air flow rate is between 0.8 and 8 mL / min per filter module. It is important to note that when testing multiple filter modules, the flow rates add up. For example, the maximum permissible air flow rate (Volmax) for 7 filter modules = 7 * 8 mL / min < 56 mL / min. If only 1 hollow fiber is defective in the tested filtration module, an air flow rate of >150 mL / min is measured. After the visual leak test, a computer program in the form of a PLS was used to evaluate whether the scattered light detector, in cooperation with the PLS program, produced a continuous chain of air bubbles > 20s during the entire test period.Additionally, it was verified whether the maximum permissible air flow rate (Volmax) was maintained throughout the entire test period. Briefly occurring air bubbles can be ignored as long as they do not occur as a chain of air bubbles lasting > 20 seconds.

[0302] Therefore, the following 3 cases are distinguished when testing 1 virus filtration module:

[0303] Case 4.b.1 :

[0304] Volmax is above 8 mL / min + air bubble chain > 20s or

[0305] Volmax is at most 8 mL / min + air bubble chain > 20s or

[0306] Volmax is over 8 mL / min + air bubble chain < 20s.

[0307] Note: It is assumed that the case where the maximum volume is 8 mL / min or less + air bubble chain > 20 s cannot occur. This would indicate a medium to large defect (air bubble chain > 20 s), which would not be detected by the volume flow measurement, which detects even the smallest defects. However, to be on the safe side, all (theoretically conceivable) variants are always checked during testing. This case has no practical significance.

[0308] Case 4.b.2:

[0309] Volmax is maximum 8 mL / min + air bubble chain < 20s.

[0310] For case 4.b.1, the following applies in all three cases: A defective filter module must be assumed. In this case, the procedure continues with point 5.a.

[0311] For case 4.b.2, the following applies: There is no defect in the filter module. In this case, the procedure continues with point 5.b.

[0312] In Example 1, the tested virus filtration module measured a Volmax of less than 8 mL / min, and no air bubble chain was detected. The tested filter module was not defective. It was possible to proceed directly to point 5.b.

[0313] For the sake of completeness, we will also explain what to do if a filter module is defective:

[0314] 5. Evaluation of the visual leak test: The computer program, in the form of the PLS program, automatically decides how to proceed without any influence from employees. a. Case 4.b.1 (defective filter module(s)) i. Pre-visual leak test (before virus filtration):

[0315] When testing multiple filter modules simultaneously and a defect has been identified, individual testing of the filter modules is performed, repeating steps 2 to 4 above. Individual testing in a setup such as that shown in Fig. 8 or 9 is performed such that the lines on the non-tested filter modules remain permanently closed during the tests. a. The defective filter module(s) are detected and replaced, and steps starting with 1.c. to 4. are repeated either with the replaced filter module only or with all filter modules until all filter modules have passed the visual leak test. b. Now that all filter modules are intact, the product's virus filtration is performed. ii. Post-visual leak test (after virus filtration):

[0316] The filter modules are tested individually again, repeating steps 2 to 4. Individual testing with a setup as shown in Fig. 8 or 9 is performed in such a way that the lines of the untested filter modules remain permanently closed during the tests. a. The result from point 4 is detected and thus verified. b. If the result again confirms a defect in one or more filter modules, proceed as in point i. below. i. Since a defect in one or more filter modules is assumed, it must be assumed that the potentially present viruses were not successfully separated, and the entire virus filtration process step must be repeated. Continue with point 5. a. b. Case 4.b.2 (no defective filter module) i. Pre-visual leak test (before virus filtration):

[0317] There are no defects in the tested filter modules. The pre-visual leak test has been passed. Virus filtration of the product can be performed immediately. ii. Post-visual leak test (after virus filtration):

[0318] The visual leak test continues as described in section 4.b. If no defects are found in the tested filter modules, the post-visual leak test is passed. The subsequent gold particle test (GPT test) can begin immediately. According to the manufacturer, Asahi Kasei, this GPT test is required as an additional test for the product's release for further processing.

[0319] According to the present example 1, the procedure was as per case 4.b.2. The pre-visual leak test was passed. Virus filtration of the product could then proceed immediately. The subsequent post-visual leak test also passed. The gold particle test (GPT test) was then performed and passed. The filtered and now virus-free product could be released. Example 2:

[0320] Visual leak test for a virus filtration module

[0321] A virus filtration module from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, was provided. The procedure was as in Example 1, except that in steps 2.b and 2.c, the liquid was fed into the filtration module from the retentate side (from above).

[0322] A leak test was not necessary because the air flow rate was monitored throughout the entire test period. In the visual leak test, a Volmax of less than 8 mL / min was measured for the tested virus filtration module, and no air bubble chain was detected. The tested filter module was not defective. It was possible to proceed directly to point 5.b. The pre-visual leak test was therefore passed. Virus filtration of the product could be started immediately. The subsequent post-visual leak test was also passed. The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product could be released.

[0323] Example 3:

[0324] Visual leak test for a virus filtration module

[0325] A virus filtration module from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, was provided. The procedure was as in Example 1, except that the process air was supplied to the virus filtration module from the feed side (from below) in step 4.b.

[0326] A leak test was not necessary because the air flow rate was monitored throughout the entire test period. In the visual leak test, a Volmax of less than 8 mL / min was measured for the tested virus filtration module, and no air bubble chain was detected. The tested filter module was not defective. It was possible to proceed directly to point 5.b. The pre-visual leak test was therefore passed. Virus filtration of the product could be started immediately. The subsequent post-visual leak test was also passed. The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product could be released.

[0327] Examples 4 to 6:

[0328] Visual leak test for a virus filtration module

[0329] Examples 1 to 3 were each repeated using a virus filtration module from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, but the optional step 3 (emptying the inner compartment of the virus filtration module) was omitted. An aqueous acetic acid / acetate buffer was used as the buffer solution.

[0330] In all examples 4 to 6, the leak test was omitted because the air flow rate was monitored throughout the entire test period. In the visual leak test, a Volmax of less than 8 mL / min was measured for each virus filtration module tested, and no air bubble chain was detected. The tested filter modules were free of defects. It was possible to proceed directly to point 5.b. The pre-visual leak test was therefore passed. Virus filtration of the product could be carried out immediately. The subsequent post-visual leak test also passed. The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product could be released.

[0331] Example 7:

[0332] Visual leak test for three virus filtration modules

[0333] Three virus filtration modules from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, were provided for simultaneous testing. The procedure was analogous to Example 1.

[0334] The leak test was successful. A defect was detected in the visual leak test: the maximum flow rate was > 150 mL / min, and an air bubble chain lasting > 20 seconds was observed. At least one of the tested filter modules was defective. Since an air bubble chain lasting > 20 seconds was observed, a medium to large defect could be assumed.

[0335] The procedure was as in case 4.b.1, and a pre-visual leak test (before virus filtration) was performed individually on each of the three filter modules. The defect was detected in the third filter module and replaced. Steps 2 through 4 were then repeated and performed simultaneously on all three filter modules. The filter modules passed the pre-visual leak test. The product could be filtered.

[0336] For definitive verification, a post-visual leak test (after virus filtration) was used to individually test the filter modules again, repeating steps 2 to 4. The post-test confirmed the results.

[0337] The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product was released.

[0338] Example 8:

[0339] Visual leak test for seven virus filtration modules

[0340] Seven virus filtration modules from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, were provided for simultaneous testing. The procedure was as in Example 1, but omitting the optional step 3 and the leak test.

[0341] In the visual leak test, a maximum volume of less than 56 mL / min was measured for the virus filtration modules tested (7 x 8 mL / min), and no air bubbles were detected. The seven filter modules tested simultaneously were free of defects. The process could proceed directly to point 5.b. The pre-visual leak test was therefore passed. Virus filtration of the product could be carried out immediately. The subsequent post-visual leak test also passed. The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product could be released. Example 9:

[0342] Visual leak test for seven virus filtration modules

[0343] Seven virus filtration modules from Asahi Kasei Medical CO., LTD., model PLANOVA 20N4, were provided for simultaneous testing. The procedure was as in Example 3, i.e., the process air in point 4.b. was supplied to the virus filtration module from the feed side (from below).

[0344] In the visual leak test, a maximum volume of less than 56 mL / min was measured for the tested virus filtration modules, and no air bubble chain was detected. The tested filter modules were free of defects. The process could proceed directly to point 5.b. The pre-visual leak test was therefore passed. Virus filtration of the product could be carried out immediately. The subsequent post-visual leak test also passed. The gold particle test (GPT test) was then successfully performed. The filtered and now virus-free product could be released.

[0345] LIST OF REFERENCE SYMBOLS:

[0346] 10, 10.1, 10.2, 10.3 virus filtration module, hollow fiber filter module

[0347] 20 lower end of a hollow fiber

[0348] 30 upper end of a hollow fiber

[0349] 35 inner region of a hollow fiber

[0350] 38.1 , 38.2 Spaces between hollow fibers

[0351] 40 Wall of a hollow fiber

[0352] 45 pores

[0353] 50 bundles of hollow fibers

[0354] 50.1. 50.2, 50.1a, 50.1b hollow fibers

[0355] 55, 55.1 , 55.2, 55.3 feed page

[0356] 65, 65.1 , 65.2, 65.3 Retentate side

[0357] 75, 75o, 75u, 75.1 , 75.2,

[0358] 75.3 Filtrate side

[0359] 78.1 , 78.2 transparent windows

[0360] 55a, 55.1a, 55.2a, 55.3a line on the feed side

[0361] 65a, 65.1 a, 65.2a, 65.3a Line on the retentate side

[0362] 70 liquid, water

[0363] 75a, 75b, 75.1a, 75.2a, 75.3a Line on the filtrate side

[0364] 55v, 55.1v, 55.2v, 55.3v, 55v valves in the line on the feed side

[0365] 65v, 65.1v, 65.2v, 65.3v valves in the line on the retentate side

[0366] 75v, 75.1v, 75.2v, 75.3v,

[0367] 75av, 75bv valves in the line on the filtrate side

[0368] 77.1 , 77.2 Openings

[0369] 78.1 , 78.2 windows

[0370] 79.1, 79.2, 79.3, 79.4 Seals

[0371] 80 air

[0372] 75v, 85.1v, 85.2v valves in air-carrying lines

[0373] 85 Air filter 90 Damage

[0374] 100 Filtration device for performing the integrity test and virus filtration

[0375] 110.1 , 110.2 Viruses 120 Scattered light sensor

[0376] 120.1 Light source

[0377] 120.2, 120.3, 120.4 detectors

[0378] 130 air bubble chain

[0379] L Light L1 , L2, L3 light rays

[0380] H horizontal axis

[0381] V vertical axis

[0382] The invention includes aspects disclosed in the following sentences:

[0383] SENTENCES

[0384] 1. A method for testing the integrity of a virus filtration module (10, 10.1, 10.2, 10.3), comprising the steps of: a) installing a virus filtration module (10, 10.1, 10.2, 10.3) in a filtration device (100), wherein the virus filtration module (10, 10.1, 10.2, 10.3) is in the form of a hollow fiber filter module comprising hollow fibers (50.1, 50.2, 50.1a, 50.1b) with an inner region (35) and hollow fiber spaces (38.1, 38.2), which has a feed side (55, 55.1, 55.2, 55.3), a retentate side (65, 65.1, 65.2, 65.3) and a Filtrate side (75, 75.1, 75.2, 75.3) and one line each (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3), one line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1,

[0385] 65.2, 65.3) and a line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3); b) filling the virus filtration module (10, 10.1, 10.2, 10.3) and the connected lines with liquid (70), a constant pressure of at most 98 ± 5 kPa with the steps: b1) filling all lines connected to the virus filtration module (10, 10.1, 10.2, 10.3) with liquid (70), but without filling the virus filtration module (10, 10.1, 10.2, 10.3); b2) filling the inner region (35) of the hollow fibers (50.1, 50.2, 50.1a, 50.1b) of the virus filtration module (10, 10.1, 10.2, 10.3) with liquid (70), wherein the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) are opened and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) is closed and b3) filling the gaps (38.1, 38.2) the hollow fibers (50.1, 50.2, 50.1a, 50.1b) of the virus filtration module (10, 10.1, 10.2, 10.3) with liquid (70), wherein either the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) are opened and the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) is closed or the line (65a, 65.1 a, 65.2a, 65.3a) on the retentate side (65, 65.1 ,.

[0386] 65.2, 65.3) and the line (75a, 75.1 a, 75.2a, 75.3a) on the filtrate side (75, 75.1 , 75.2, 75.3) are opened and the line (55a, 55.1 a, 55.2a, 55.3a) on the feed side (55, 55.1 ,

[0387] 55.2, 55.3) are closed; wherein in steps b2) and b3) the liquid (70) is supplied to the virus filtration module (10, 10.1, 10.2, 10.3) from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) or from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3); c) stopping the supply of liquid (70) as soon as the virus filtration module (10, 10.1, 10.2, 10.3) and the lines are filled with liquid (70) while maintaining the pressure, and closing all lines; d) Supplying air (80) to the virus filtration module (10, 10.1, 10.2, 10.3) with step d1) or d2): d1) Opening the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) of the virus filtration module (10, 10.1, 10.2, 10.3) and leaving the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1 , 65.2, 65.3), wherein the pressure is maintained in order to supply air (80) at a constant pressure at the same level as the liquid pressure from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) into the virus filtration module (10, 10.1, 10.2, 10.3); or d2) opening the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2.

[0388] 65.3) and the line (75a, 75.1 a, 75.2a, 75.3a) on the filtrate side (75, 75.1 , 75.2,

[0389] 75.3) of the virus filtration module (10, 10.1, 10.2, 10.3) and leaving the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) closed, the pressure being maintained to supply air (80) at a constant pressure at the same level as the liquid pressure from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) into the virus filtration module (10, 10.1, 10.2, 10.3); and e) automatically detecting air bubbles (130) occurring in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) of the virus filtration module (10, 10.1, 10.2, 10.3).

[0390] 2. Method according to sentence 1, characterized in that the automatic detection of occurring air bubbles (130) in step e) is carried out optically, in particular a scattered light sensor (120) is used, wherein the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for optical detection is selected such that it consists of or comprises transparent material.

[0391] 3. Method according to sentence 1, characterized in that after carrying out step c) from the inner region (35) of the hollow fibers (50.1, 50.2, 50.1a, 50.1b) and the connected line (55a, 55.1a, 55.2a, 55.3a) the existing liquid (70) is completely emptied. 4. Method according to one of sentences 1 to 3, characterized in that in a step e) following step f) an evaluation, in particular an automatic evaluation, of step e) is carried out, wherein the test is assessed as passed if during the test no continuous chain of air bubbles is detected over a period of at least 20 seconds in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3).

[0392] 5. Method according to one of the preceding sentences 1 to 4, characterized in that the liquid (70) according to step b2) and b3) is supplied to the virus filtration module (10, 10.1, 10.2, 10.3) from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the air (80) according to step d2) is supplied to the virus filtration module (10, 10.1, 10.2, 10.3) from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3).

[0393] 6. Method according to one of the preceding sentences 1 to 5, characterized in that in steps b2) and b3) the filling level of the virus filtration module (10, 10.1, 10.2, 10.3) is monitored by:

[0394] Measuring the pressure before and after the virus filtration module (10, 10.1, 10.2, 10.3) and determining the differential pressure and / or

[0395] Determining the supplied amount of liquid (70) in relation to the dead volume of the filtration device (100), including the virus filtration module (10, 10.1, 10.2, 10.3), whereby: the supplied amount of liquid (70) > dead volume.

[0396] 7. Method according to one of the preceding sentences 1 to 6, characterized in that steps b) to e) and optionally f) are carried out with the support of a process control system, wherein the process control system is selected in particular such that it can also support the implementation of virus filtration.

[0397] 8. Method according to one of the preceding sentences 1 to 7, characterized in that the method for testing the integrity of a virus filtration module (10, 10.1, 10.2, 10.3) according to steps a) to e) and optionally f) is carried out twice and between the two methods a virus filtration is carried out with the tested virus filtration module (10, 10.1, 10.2, 10.3).

[0398] 9. Method according to one of the preceding sentences 1 to 8, characterized in that two, three, four, five, six, seven or more virus filtration modules (10, 10.1, 10.2, 10.3) are tested simultaneously in the method according to steps a) to e) and optionally f).

[0399] 10. The method according to one of the preceding sentences 1 to 9, characterized in that one, two, three or more of the following method steps are carried out: the liquid (70) is selected from water or a buffer solution comprising water; the water of the liquid (70) is selected from distilled water, bidistilled or deionized water, ultrapure water or sterile water, in particular water for injection purposes; the virus filtration module (10, 10.1, 10.2, 10.3) is arranged during the method such that the hollow fibers (50.1, 50.2, 50.1a, 50.1b) run in a horizontal direction or in a vertical direction, in particular in a vertical direction; before the liquid (70) enters the virus filtration module (10, 10.1, 10.2, 10.3) in steps b1) and b2) the liquid (70) is passed through an inlet filter to filter out possible impurities and contamination from the liquid (70); after the liquid (70) has exited the virus filtration module (10, 10.1, 10.2, 10.3) in steps b2) and b3) the liquid (70) is passed through an outlet filter; the air (80) is selected from process air; the air (80) is passed through an air filter (85) before entering the virus filtration module (10, 10.1, 10.2, 10.3); after step d) and before step e), a stabilization time of up to 600 s is waited for, during which the air (80) is further distributed; a counting device for the air bubbles is used; transparent sections in the form of windows (78.1, 78.2) are provided in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for detection by optical means;.

[0400] Windows (78.1, 78.2) made of transparent plastic, selected from polystyrene (PS), polymethyl methacrylate (PMMA) or polycarbonate (PC), polyvinyl chloride (PVC), polyphenylene ether (PPO) or polyethylene (PE) or mixtures thereof; or selected from glass of hydrolytic class 1 or sapphire glass; in the case of detection by optical means, the detection device (120) is arranged on a line (75a) running from bottom to top, so that the air bubbles (130) to be detected can rise in the line (75a); during step d 1 ) or d 2 ) the volume flow of the air (80) is measured; an air-conducting line (85a) leading from the air filter (85) is provided with a section which has the highest point of the filtration device (100) so that no liquid (70) can rise to the air filter (85); when testing several virus filtration modules (10.1, 10.2, 10.3) these are aligned parallel to each other with the hollow fibers (50.1, 50.2, 50.1a, 50.1b) running vertically; when testing several virus filtration modules (10.1, 10.2, 10.3) simultaneously, the liquid (70) is supplied via a line (55.1a, 55.2a, 55.3a or 65.1a, 65.2a, 65.3a) assigned to each virus filtration module (10.1, 10.2, 10.3) and from the same side for all virus filtration modules (10.1, 10.2, 10.3) to be tested; when testing several virus filtration modules (10.1, 10.2, 10.3) simultaneously, the air (80) is supplied via a line (55.1a, 55.2a, 55.3a or 65.1a, 65.2a, 65.3a) assigned to each virus filtration module (10.1, 10.2, 10.3) and from the same side for all virus filtration modules (10.1, 10.2, 10.3) to be tested; when testing several virus filtration modules (10.1, 10.2, 10.3) simultaneously, the respective lines (75.1a, 75.2a, 75.3a) on the filtrate side (75.1, 75.2, 75.3) are brought together to form a line (75a), and the detection device (120) is arranged on the brought together line (75a); before carrying out steps a) to e), the lines are sterilized, in particular by hot steam sterilization; after sterilizing the lines and before carrying out step a), the lines are placed under an overpressure of approximately 100 kPa and then the pressure is reduced to a pressure P < 10 kPa in all lines; before carrying out step d), a leak test is carried out on the filtration system (100) and the installed virus filtration module(s) (10.1, 10.2, 10.3); and / or the filtration device is designed such that virus filtration can be carried out with it.

[0401] 11. Method according to one of the preceding sentences 1 to 10, characterized in that if a defect is detected in the integrity test during simultaneous testing of several virus filtration modules (10.1, 10.2, 10.3), an individual test of the virus filtration modules (10.1, 10.2, 10.3) is carried out according to steps b) to e) and optionally f), the defective virus filtration module(s) (10.1, 10.2, 10.3) is / are replaced and the method according to steps b) to e) and optionally f) is / are repeated with the replaced virus filtration module(s) or with all virus filtration modules (10.1, 10.2, 10.3).

[0402] 12. Filtration device (100) for carrying out the method according to one of sentences 1 to 11, comprising one, two, three, four, five, six, seven or more virus filtration modules (10, 10.1, 10.2, 10.3) which are in the form of hollow fiber filter modules, each comprising hollow fibers (50.1, 50.2, 50.1a, 50.1b) with an inner region (35) and hollow fiber interspaces (38.1, 38.2), each having a feed side (55, 55.1, 55.2, 55.3), a retentate side (65, 65.1, 65.2, 65.3) and a filtrate side (75, 75.1,

[0403] 75.2, 75.3);

[0404] Devices for attaching and securing one or more virus filtration modules (10, 10.1, 10.2, 10.3); one line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3), one line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) and one line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) of each virus filtration module (10, 10.1,

[0405] 10.2, 10.3) for supplying liquid (70) and / or air (80) at a constant pressure of not more than 98 ± 5 kPa to the virus filtration module(s) (10, 10.1, 10.2, 10.3);

[0406] Opening and closing devices (55v, 55.1v, 55.2v, 55.3v, 65v, 65.1v, 65.2v, 65.3v, 75v, 75.1v, 75.2v, 75.3v, 75av, 75bv, 85v, 85.1v, 85.2v) for the respective lines; a connection for supplying liquid (70) at a constant pressure of no more than 98 ± 5 kPa with the lines to the virus filtration module(s) (10, 10.1, 10.2, 10.3); a connection for supplying air (80) of a constant pressure at the same level as the liquid pressure with the lines to the virus filtration module(s) (10, 10.1, 10.2, 10.3); and a detection device (120) for automatically detecting air bubbles (130) in the line (75a) on the filtrate side (75, 75.1, 75.2, 75.3) of the virus filtration module(s) (10, 10.1, 10.2, 10.3).

[0407] 13. Filtration device (100) according to sentence 12, characterized in that the detection device represents a scattered light sensor (120), wherein the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for optical detection is selected such that it consists of or comprises transparent material.

[0408] 14. Filtration device (100) according to sentence 12 or 13, characterized in that it has one, two, three, four or more of the following features: transparent sections in the form of windows (78.1, 78.2) in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) are provided for detection by optical means; transparent sections in the form of windows (78.1, 78.2) made of transparent plastic, selected from polystyrene (PS), polymethyl methacrylate (PMMA) or polycarbonate (PC), polyvinyl chloride (PVC), polyphenylene ether (PPO) or polyethylene (PE) or mixtures thereof; or selected from glass of hydrolytic class 1 or sapphire glass are provided; the virus filtration module (10, 10.1, 10.2, 10.3) is arranged in the filtration device such that the hollow fibers in the virus filtration module (10, 10.1, 10.2, 10.3) run in a horizontal direction or in a vertical direction, in particular in a vertical direction; the opening and closing devices for the lines are selected from valves; in the case of optical detection, the detection device (120) is arranged on a line (75a) running from bottom to top, so that the air bubbles (130) can rise in the line (75a); a measuring device is provided for measuring the volume flow of the air (80) through the virus filtration module (10, 10.1, 10.2, 10.3); an air-conducting line (85a) leading from the air filter (85) has a section which represents the highest point of the filtration device (100), so that no liquid (70) can rise to the air filter (85); if several virus filtration modules (10.1, 10.2, 10.3) are present in the filtration device (100) at the same time, these are each connected to one another in parallel with the hollow fibers (50.1, 50.2, 50.1a, 50.1 b) are aligned in a vertical direction; and / or if several virus filtration modules (10.1, 10.2, 10.3) are simultaneously arranged in the filtration device.

[0409] (100) are present, the respective lines (75.1 a, 75.2a, 75.3a) on the filtrate side (75.1, 75.2, 75.3) are combined to form a line (75a), and the detection device (120) is arranged on the combined line (75a).

[0410] 15. Filtration device (100) according to one of sentences 12 to 14, characterized in that the filtration device (100) for carrying out the method for testing the integrity of a virus filtration module (10, 10.1, 10.2, 10.3) according to one of sentences 1 to 12 is designed such that virus filtration can be carried out therein with the virus filtration module(s) (10, 10.1, 10.2, 10.3) being tested.

[0411] 16. A method for cultivating prokaryotic or eukaryotic cells in liquid cell culture in a bioreactor to produce a product, in particular a protein, and carrying out virus filtration of the resulting product using one or more virus filtration modules (10, 10.1, 10.2, 10.3), wherein the method for testing the integrity of the one or more virus filtration modules (10, 10.1, 10.2, 10.3) according to one of the preceding sentences 1 to 11 is carried out before and / or after virus filtration.

[0412] 17. A process for producing a recombinant protein, the process comprising the following steps:

[0413] Step a) Cultivation of prokaryotic or eukaryotic cells expressing a recombinant protein in cell culture in a bioreactor;

[0414] Step b) Harvesting the recombinant protein;

[0415] Step c) Purification of the recombinant protein;

[0416] Step d) removing viruses from the obtained recombinant protein in a virus filtration with one or more virus filtration modules (10, 10.1, 10.2, 10.3), wherein the method for testing the integrity of the one or more virus filtration modules (10, 10.1, 10.2, 10.3) according to one of the preceding sentences 1 to 11 is carried out before and / or after the virus filtration.

Claims

PATENT CLAIMS 1. A method for testing the integrity of one or more virus filtration modules (10, 10.1, 10.2, 10.3), comprising the steps of: a) installing one or more virus filtration modules (10, 10.1, 10.2, 10.3) in a filtration device (100), wherein each virus filtration module (10, 10.1, 10.2, 10.3) is in the form of a hollow fiber filter module, each comprising hollow fibers (50.1, 50.2, 50.1a, 50.1b) with an inner region (35) and hollow fiber spaces (38.1, 38.2), a feed side (55, 55.1, 55.2, 55.3), a retentate side (65, 65.1, 65.2, 65.3) and a filtrate side (75, 75.1, 75.2, 75.3) and one line each (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3), one line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) and one line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3); b) filling the virus filtration module(s) (10, 10.1, 10.2, 10.3) and the connected lines with liquid (70), a constant pressure of not more than 98 ± 5 kPa with the steps: b1) filling all lines connected to the virus filtration module(s) (10, 10.1, 10.2, 10.3) with liquid (70), but without filling the virus filtration module(s) (10, 10.1, 10.2, 10.3); b2) filling the inner region (35) of the hollow fibers (50.1, 50.2, 50.1a, 50.1b) of the virus filtration module(s) (10, 10.1, 10.2, 10.3) with liquid (70), wherein the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) are opened and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) is closed and b3) filling the spaces (38.1, 38.2) of the hollow fibers (50.1, 50.2, 50.1a, 50.1b) of the virus filtration module(s) (10, 10.1, 10.2, 10.3) with liquid (70), wherein either the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) are opened and the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) is closed or the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) is opened and the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) is closed; wherein in steps b2) and b3) the liquid (70) is supplied to the virus filtration module(s) (10, 10.1, 10.2, 10.3) from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) or from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3);. c) stopping the supply of liquid (70) as soon as the virus filtration module(s) (10, 10.1, 10.2, 10.3) and the lines are filled with liquid (70), maintaining the pressure, and closing all lines; d) supplying air (80) to the virus filtration module(s) (10, 10.1, 10.2, 10.3) with step d1) or d2): d1) opening the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1 , 75.2, 75.3) of the virus filtration module(s) (10, 10.1, 10.2, 10.3) and leaving the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3), wherein the pressure is maintained in order to supply air (80) with a constant pressure at the same level as the liquid pressure from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) into the virus filtration module(s) (10, 10.1, 10.2, 10.3); or d2) opening each of the lines (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) and the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1 , 75.2, 75.3) of the virus filtration module(s) (10, 10.1, 10.2, 10.3) and leaving the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3), wherein the pressure is maintained in order to supply air (80) at a constant pressure at the same level as the liquid pressure from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) into the virus filtration module(s) (10, 10.1, 10.2, 10.3); wherein during step d1) or d2) the volume flow of the air (80) through the one or more virus filtration modules (10, 10.1, 10.2, 10.3) is measured; and e) automatically detecting an occurring chain of air bubbles (130) in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) of the virus filtration module(s) (10, 10.1, 10.2, 10.3).

2. Method according to claim 1, characterized in that the automatic detection of an occurring air bubble chain (130) in step e) is carried out optically, in particular a scattered light sensor (120) is used, wherein the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for optical detection is selected such that it consists of or comprises transparent material.

3. Method according to claim 1, characterized in that after carrying out step c) the liquid (70) present is completely emptied from the inner region (35) of the hollow fibers (50.1, 50.2, 50.1a, 50.1b) and the connected line (55a, 55.1a, 55.2a, 55.3a).

4. Method according to one of the preceding claims 1 to 3, characterized in that the volume flow of the air (80) through the one or more virus filtration modules (10, 10.1, 10.2, 10.3) is measured only during step e).

5. Method according to one of claims 1 to 4, characterized in that in a step e) following step f) an evaluation, in particular an automatic evaluation, of the integrity test is carried out, wherein the test is assessed as passed if during the test no continuous chain of air bubbles is detected for a duration of at least 20 seconds in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3), wherein in particular a counting device for the air bubbles of the air bubble chain (130) is used, and at the same time a volume flow of the air (80) through the virus filtration modules (10, 10.1, 10.2, 10.3) of at most 8 mL / min per virus filtration module (10, 10.1, 10.2, 10.3) is measured.

6. Method according to one of the preceding claims 1 to 5, characterized in that the liquid (70) according to step b2) and b3) is supplied to the virus filtration module or modules (10, 10.1, 10.2, 10.3) from the line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3) and the air (80) according to step d2) is supplied to the virus filtration module or modules (10, 10.1, 10.2, 10.3) from the line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3).

7. Method according to one of the preceding claims 1 to 6, characterized in that in steps b2) and b3) the degree of filling of the virus filtration module(s) (10, 10.1, 10.2, 10.3) is monitored by: Measuring the pressure before and after each virus filtration module (10, 10.1, 10.2, 10.3) and determining the differential pressure and / or Determining the supplied amount of liquid (70) in relation to the dead volume of the filtration device (100), including each virus filtration module (10, 10.1, 10.2, 10.3), whereby: the supplied amount of liquid (70) > dead volume.

8. Method according to one of the preceding claims 1 to 7, characterized in that steps b) to e) and optionally f) are carried out with the support of a computer program in the form of a process control system, wherein the process control system is selected in particular so that it can also support the implementation of virus filtration.

9. Method according to one of the preceding claims 1 to 8, characterized in that the method for testing the integrity of a virus filtration module (10, 10.1, 10.2, 10.3) according to steps a) to e) and optionally f) is carried out twice and between the two methods a virus filtration is carried out with the virus filtration module(s) tested (10, 10.1, 10.2, 10.3).

10. Method according to one of the preceding claims 1 to 9, characterized in that the liquid (70) is selected from distilled water, bidistilled or deionized water, ultrapure water or sterile water, in particular water for injection purposes or a buffer solution comprising water, and / or the air (80) is selected from process air.

11. Method according to one of the preceding claims 1 to 10, characterized in that before the liquid (70) enters each virus filtration module (10, 10.1, 10.2, 10.3) in steps b1) and b2), the liquid (70) is passed through an inlet filter in order to filter out possible impurities and contaminations from the liquid (70) and / or after the liquid (70) exits each virus filtration module (10, 10.1, 10.2, 10.3) in steps b2) and b3), the liquid (70) is passed through an outlet filter and / or the air (80) is passed through an air filter (85) before entering each virus filtration module (10, 10.1, 10.2, 10.3).

12. Method according to one of the preceding claims 1 to 11, characterized in that during step d) and before step e) a stabilization time of up to 600 s is waited for, in which the air (80) is further distributed.

13. Method according to one of the preceding claims 1 to 12, characterized in that transparent sections in the form of windows (78.1, 78.2) are provided in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for detection by optical means, wherein the windows (78.1, 78.2) are made of transparent plastic, in particular selected from polystyrene (PS), polymethyl methacrylate (PMMA) or polycarbonate (PC), polyvinyl chloride (PVC), polyphenylene ether (PPO) or polyethylene (PE) or mixtures thereof; or selected from glass of hydrolytic class 1 or sapphire glass.

14. Method according to one of the preceding claims 1 to 13, characterized in that in the case of detection by optical means, the detection device (120) is arranged on a line (75a) running from bottom to top, so that the chain of air bubbles (130) to be detected can rise in the line (75a).

15. Method according to one of the preceding claims 1 to 14, characterized in that an air-conducting line (85a) leading from the air filter (85) is provided with a section which has the highest point of the filtration device (100) so that no liquid (70) can rise to the air filter (85).

16. Method according to one of the preceding claims 1 to 15, characterized in that when testing a virus filtration module (10, 10.1, 10.2, 10.3), it is arranged such that the hollow fibers (50.1, 50.2, 50.1a, 50.1b) run in a horizontal direction or in a vertical direction or in an intermediate position between the horizontal and vertical directions, and when testing several virus filtration modules (10.1, 10.2, 10.3) simultaneously, they are arranged such that the hollow fibers (50.1, 50.2, 50.1a, 50.1b) are each aligned parallel to one another, in particular run in a vertical direction or in an intermediate position between the horizontal and vertical directions.

17. Method according to one of the preceding claims 1 to 16, characterized in that when several virus filtration modules (10.1, 10.2, 10.3) are tested simultaneously, the liquid (70) and / or the air (80) is supplied via a line (55.1a, 55.2a, 55.3a or 65.1a, 65.2a, 65.3a) assigned to each virus filtration module (10.1, 10.2, 10.3) and from the same side for all virus filtration modules (10.1, 10.2, 10.3) to be tested.

18. Method according to one of the preceding claims 1 to 17, characterized in that when several virus filtration modules (10.1, 10.2, 10.3) are tested simultaneously, the respective lines (75.1a, 75.2a, 75.3a) on the filtrate side (75.1, 75.2, 75.3) are combined to form one line (75a), and the detection device (120) is arranged on the combined line (75a).

19. Method according to one of the preceding claims 1 to 18, characterized in that before carrying out step a) a sterilization, in particular hot steam sterilization, of the lines is carried out and in particular after a sterilization of the lines and / or before carrying out step a) the lines are placed under excess pressure of approximately 100 kPa and then a pressure reduction to a pressure P < 10 kPa is carried out in all lines.

20. Method according to one of the preceding claims 1 to 19, characterized in that before carrying out step d), a leak test is carried out on the filtration system (100) and the installed virus filtration module(s) (10.1, 10.2, 10.3).

21. Method according to one of the preceding claims 1 to 20, characterized in that the filtration device is designed such that a virus filtration can be carried out therewith, wherein the virus filtration is carried out at the same or a lower pressure selected in claim 1.

22. Method according to one of the preceding claims 1 to 21, characterized in that if a defect is detected in the integrity test during simultaneous testing of several virus filtration modules (10.1, 10.2, 10.3), an individual testing of the virus filtration modules (10.1, 10.2, 10.3) is carried out according to steps b) to e) and optionally f), the defective virus filtration module(s) (10.1, 10.2, 10.3) are replaced and the method according to steps b) to e) and optionally f) is repeated with the replaced or with all virus filtration modules (10.1, 10.2, 10.3).

23. Filtration device (100) for carrying out the method according to one of claims 1 to 22, comprising one or more virus filtration modules (10, 10.1, 10.2, 10.3) which are in the form of hollow fiber filter modules, each comprising hollow fibers (50.1, 50.2, 50.1a, 50.1b) with an inner region (35) and hollow fiber spaces (38.1, 38.2), each having a feed side (55, 55.1, 55.2, 55.3), a retentate side (65, 65.1, 65.2, 65.3) and a filtrate side (75, 75.1, 75.2, 75.3); Means for attaching and securing one or more virus filtration modules (10, 10.1, 10.2, 10.3); one line (55a, 55.1a, 55.2a, 55.3a) on the feed side (55, 55.1, 55.2, 55.3), one line (65a, 65.1a, 65.2a, 65.3a) on the retentate side (65, 65.1, 65.2, 65.3) and one line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) of each virus filtration module (10, 10.1, 10.2, 10.3) for supplying liquid (70) and / or air (80) at a constant pressure of at most 98 ± 5 kPa to the virus filtration modules (10, 10.1, 10.2, 10.3); Opening and closing devices (55v, 55.1v, 55.2v, 55.3v, 65v, 65.1v, 65.2v, 65.3v, 75v, 75.1v, 75.2v, 75.3v, 75av, 75bv, 85v, 85.1v, 85.2v) for the respective lines; a connection for supplying liquid (70) at a constant pressure of not more than 98 ± 5 kPa to the lines leading to the virus filtration module(s) (10, 10.1, 10.2, 10.3); a connection for supplying air (80) at a constant pressure equal to the liquid pressure to the lines leading to the virus filtration module(s) (10, 10.1, 10.2, 10.3); a detection device (120) for automatically detecting an air bubble chain (130) in the line (75a) on the filtrate side (75, 75.1, 75.2, 75.3) of the virus filtration module(s) (10, 10.1, 10.2, 10.3) and a measuring device for measuring the volume flow of air (80) through the virus filtration module(s) (10, 10.1, 10.2, 10.3).

24. Filtration device (100) according to claim 23, characterized in that the detection device represents a scattered light sensor (120), wherein the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for optical detection is selected such that it consists of or comprises transparent material.

25. Filtration device (100) according to claim 23 or 24, characterized in that transparent sections in the form of windows (78.1, 78.2) are provided in the line (75a, 75.1a, 75.2a, 75.3a) on the filtrate side (75, 75.1, 75.2, 75.3) for detection by optical means, wherein the windows (78.1, 78.2) are made of transparent plastic, in particular selected from polystyrene (PS), polymethyl methacrylate (PMMA) or polycarbonate (PC), polyvinyl chloride (PVC), polyphenylene ether (PPO) or polyethylene (PE) or mixtures thereof; or selected from glass of hydrolytic class 1 or sapphire glass.

26. Filtration device (100) according to one of the preceding claims 23 to 25, characterized in that, in the case of detection by optical means, the detection device (120) is arranged on a line (75a) running from bottom to top, so that the air bubble chain (130) can rise in the line (75a), and / or an air-conducting line (85a) leading from the air filter (85) has a section which represents the highest point of the filtration device (100), so that no liquid (70) can rise to the air filter (85), and / or the respective lines (75.1a, 75.2a, 75.3a) on the filtrate side (75.1, 75.2, 75.3) are combined to form a line (75a), and the detection device (120) is arranged on the combined line (75a). is arranged.

27. Filtration device (100) according to one of the preceding claims 23 to 26, characterized in that if several virus filtration modules (10.1, 10.2, 10.3) are present in the filtration device (100) at the same time, these are arranged such that the hollow fibers (50.1, 50.2, 50.1a, 50.1b) of the virus filtration modules (10.1, 10.2, 10.3) are each aligned parallel to one another, in particular run in the vertical direction or are aligned in an intermediate position between the horizontal and vertical directions.

28. Filtration device (100) according to one of the preceding claims 23 to 27, characterized in that the filtration device (100) for carrying out the method for testing the integrity of a virus filtration module (10, 10.1, 10.2, 10.3) according to one of claims 1 to 22 is designed such that virus filtration can be carried out therein with the virus filtration module(s) (10, 10.1, 10.2, 10.3) being tested.

29. A method for cultivating prokaryotic or eukaryotic cells in liquid cell culture in a bioreactor to produce a product, in particular protein, and carrying out a virus filtration of the product obtained with one or more virus filtration modules (10, 10.1, 10.2, 10.3), wherein the method for testing the integrity of the one or more Virus filtration modules (10, 10.1, 10.2, 10.3) according to one of the preceding claims 1 to 22 are carried out before and / or after the virus filtration.

30. A process for producing a recombinant protein, the process comprising the following steps: Step a) Cultivation of prokaryotic or eukaryotic cells expressing a recombinant protein in cell culture in a bioreactor; Step b) Harvesting the recombinant protein; Step c) Purification of the recombinant protein; Step d) removing viruses from the obtained recombinant protein in a virus filtration with one or more virus filtration modules (10, 10.1, 10.2, 10.3), wherein the method for testing the integrity of the one or more virus filtration modules (10, 10.1, 10.2, 10.3) according to one of the preceding claims 1 to 22 is carried out before and / or after the virus filtration.

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