Method for inducing an immune response

Abstract

The present invention relates to methods for inducing an immune response in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. In one example, an immunogenic composition is administered via the oral route to a pig, wherein the immunogenic composition comprises a recombinant virus capsid protein capable of forming a virus-like particle. This allows to simply induce an immune response in the pigs, while simultaneously reducing the propensity for adverse reactions, eliminating the risk of injection site reactions, avoiding pain, and putting less stress on the animals.

Description

[0001]23-0041-ff Boehringer Ingelheim Vetmedica GmbH Method for inducing an immune response BACKGROUND OF THE INVENTION TECHNICAL FIELD The present invention relates to methods for inducing an immune response in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. In one example, an immunogenic composition is administered via the oral route to a pig, wherein the immunogenic composition comprises a recombinant virus capsid protein capable of forming a virus-like particle. This allows to simply induce an immune response in the pigs, while simultaneously reducing the propensity for adverse reactions, eliminating the risk of injection site reactions, avoiding pain, and putting less stress on the animals. BACKGROUND INFORMATION Viral infection remains an important health problem in animals with adverse economic consequences. For example, there are a number of viral pathogens that cause disease in economically important livestock animals such as pigs. Viruses infecting pigs include, for example, porcine circovirus type 2 and porcine parvovirus. Porcine circovirus type 2 (PCV2) is a small (17-22 nm in diameter), icosahedral, non-enveloped DNA virus, which contains a single-stranded circular genome. PCV2 shares approximately 80% sequence identity with porcine circovirus type 1 (PCV1). However, in contrast with PCV1, which is generally non-virulent, swine infected with PCV2 exhibit a syndrome commonly referred to as Post-weaning Multisystemic Wasting Syndrome (PMWS). PMWS is clinically characterized by wasting, paleness of the skin, unthriftiness, respiratory distress, diarrhea, icterus, and jaundice. In some affected swine, a combination of all symptoms will be apparent while other swine will only have one or two of these symptoms. During necropsy, microscopic and macroscopic lesions also appear on multiple tissues and organs, with lymphoid organs being the most common site for lesions. A strong correlation has been observed between the amount of PCV2 nucleic acid or antigen and the severity of microscopic lymphoid lesions. Mortality rates for swine infected with PCV2 can approach 80%. In addition to PMWS, PCV2 has been associated with several other infections including pseudorabies, porcine reproductive and respiratory syndrome (PRRS), Glasser’s disease, streptococcal meningitis, salmonellosis, postweaning colibacillosis, dietetic hepatosis, and suppurative bronchopneumonia. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Several vaccines are available to reduce the impact of PCV2 infections in pigs. U.S. Patent No.6,703,023 (US 6,703,023 B1) provides a DNA based vaccine for the prophylaxis of pigs against PMWS, wherein this and the following publications referred to herein are incorporated by reference in their entirety. In WO2003049703 production of a live chimeric vaccine is described, comprising the non-pathogenic PCV1 virus in which, however, the ORF2 protein is replaced by the ORF2 protein of the pathogenic PCV2. WO199918214 and WO199929717 have provided several PCV2 strains and procedures for the preparation of a killed PVC2 vaccine. Preparation of subunit vaccines have also been described in WO199918214 and WO199929717. An effective ORF2 based subunit vaccine has been reported in WO2006072065. Further ORF2 based subunit vaccines are described also in WO200728823 or WO2015051099. Porcine parvovirus (PPV) is an autonomous replicating virus of the Parvovirinae subfamily of the genus Protoparvovirus within the family Parvoviridae containing a single stranded DNA molecule of about 5100 nucleotides. Only the minus strand of the DNA is packaged into virions. The genome of the virus encodes three capsid proteins (VP1, VP2, VP3) and one non- structural protein (NS1). The capsid of parvovirus is about 22-25 nanometers in diameter and is comprised of VP1 and VP2 subunits. These proteins are derived from alternatively spliced versions of the same RNA molecule and thus overlap in sequence. Further, porcine parvovirus exhibits a high level of sequence similarity to feline panleukopenia virus, canine parvoviruses PPV infection is a common cause of reproductive failure in breeding pigs throughout the world. Serological studies show that porcine parvovirus is widespread in all swine producing regions of the world with up to 80 % of animals showing seroconversion. Currently available PPV vaccines are produced, on the either hand, by growing native virus on primary cells of porcine origin or in established cell lines and, after this, infectious virus is isolated and inactivated with chemical agents to end up with a whole cell killed virus vaccine. On the other hand, an effective VP2 based subunit vaccine, and its production, has been reported in WO2018083154 or WO2018083156. Vaccination of pigs with conventional vaccines against viruses, such as PCV2 and PPV, which is usually done by injection, may result in injection site reactions, increases the propensity for adverse reactions and is frequently a risk factor for adverse reactions. Additionally, such vaccination is linked with pain and stress for the animals. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Thus, administration routes for non-replicating virus antigens are desired which can be simply practiced and which mount to an immune response against virus in the pigs, while simultaneously result in less propensity for adverse reactions, do not have the risk of injection site reactions, avoid pain, and put less stress on the animals. DESCRIPTION OF THE INVENTION The solution to the above technical problems is achieved by the description and the embodiments characterized in the claims. Thus, the invention in its different aspects is implemented according to the claims. The invention is based on the surprising finding that orally administering an immunogenic composition which comprises a recombinant PCV2 ORF2 protein to pigs resulted in their immunization against PCV2. In a first aspect, the invention thus relates to a method for - inducing an immune response in a subject, or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen, and wherein said method is also termed “the method of the present invention” hereinafter. In one aspect, the method of the present invention is a method for inducing an immune response in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. In another aspect, the method of the present invention is a method for reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non- replicating virus antigen. In a further preferred aspect, the method of the present invention preferably is a method for - inducing an immune response in a subject, and 23-0041-ff Boehringer Ingelheim Vetmedica GmbH - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. Said immunogenic composition, which is also termed “the immunogenic composition according to the present invention” hereinafter, is preferably free of replicating virus antigen. Said non-replicating virus antigen, which is also termed “the non-replicating virus antigen according to the present invention” hereinafter, preferably comprises or is a recombinant protein. Said recombinant protein, which is also termed “the recombinant protein according to the present invention” hereinafter, is preferably capable of forming a virus-like particle. As used herein, the term “virus-like particle” refers to a structure resembling a virus particle but which is non-pathogenic, non-replicative, and non-infectious as it lacks all or part of the viral genome. Preferably, the recombinant protein according to the present invention is a recombinant baculovirus expressed protein. The term “recombinant”, as used herein, is in particular understood to be equivalent to “recombinantly expressed”. Thus, for instance “recombinant virus protein” is equivalent to “recombinantly expressed virus protein”. The non-replicating virus antigen according to the present invention is preferably a recombinant virus protein, in particular recombinant baculovirus expressed virus protein. The term "recombinant virus protein" or “recombinantly expressed virus protein”, respectively, as used herein, in particular refers to a virus protein which is produced by recombinant DNA techniques, wherein generally DNA encoding the expressed protein is inserted into a suitable expression vector which is in turn used to transform or, in the case of a virus vector, to infect a host cell to produce the heterologous protein. Thus, the term "recombinant virus protein" or “recombinantly expressed virus protein”, respectively, as used herein, particularly refers to a protein molecule that is expressed from a recombinant DNA molecule. "Recombinant DNA molecule" as used herein refers to a DNA molecule that is comprised of segments of DNA joined together by means of molecular biological techniques. Suitable systems for production 23-0041-ff Boehringer Ingelheim Vetmedica GmbH of recombinant proteins include but are not limited to insect cells (e.g., baculovirus), prokaryotic systems (e.g., Escherichia coli), fungi (e.g., Myceliophthora thermophile, Aspergillus oryzae, Ustilago maydis), yeast (e.g., Saccharomyces cerevisiae, Pichia pastoris), mammalian cells (e.g., Chinese hamster ovary, HEK293), plants (e.g., safflower), algae, avian cells, amphibian cells, fish cells, and cell-free systems (e.g., rabbit reticulocyte lysate). According to a particularly preferred aspect, the immunogenic composition according to the present invention is free of an adjuvant. According to a particular preferred aspect, the immunogenic composition according to the present invention consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers. According to further preferred aspect the immunogenic composition according to the present invention consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one immunogenic substance different from said virus antigen. According to another aspect, the immunogenic composition according to the present invention consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one adjuvant. According to still another aspect, the immunogenic composition according to the present invention consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one adjuvant; and 23-0041-ff Boehringer Ingelheim Vetmedica GmbH at least one immunogenic substance different from said virus antigen. Preferably, the immunogenic composition according to the present invention additionally contains a gel composition, which is also termed “the gel composition according to the present invention” hereinafter. The immune response, as mentioned herein, is preferably a protective immune response. Preferably, the herein mentioned immune response is an immune response against a virus, wherein said virus is a virus, which is of the species having a genome encoding - the non-replicating virus antigen, or - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen. Preferably, said virus is PCV2. Preferably, said immune response is an immune response against PCV2. Thus, the method according to the present invention is preferably a method for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating PCV2 antigen. As used herein, the term “virus antigen” means a substance derived from a virus or a component thereof or both of them, the substance being capable of inducing an immune response. For instance, the term “PCV2 antigen” in particular means a substance derived from a PCV2 or a component thereof or both of them, the substance being capable of inducing an immune response. The term "non-replicating virus antigen” in particular relates to molecules derived from a virus, such as proteins, carbohydrates, lipids or nucleic acids, or are complex combinations thereof, more or less pure. When prepared from a virus, non-replicating antigen can refer to an intact but killed (i.e. non-replicative) virus, or can be a part thereof such as an extract, fraction, homogenate, or sonicate. Also, a non-replicating virus antigen can be a nucleic acid based, or 23-0041-ff Boehringer Ingelheim Vetmedica GmbH recombinant product, such as an expression vector or an expressed protein, or the product of an in vitro expression system. All these are well-known in the art. Most preferably, the non-replicating virus antigen according to the present invention is a recombinant virus protein. The term “virus protein” encompasses any protein that is derived from a virus. Specific examples include a virus capsid protein, a virus coat protein, a virus envelope protein, and a virus core protein. As used herein, the term “antigenic determinant” is in particular understood to refer to that portion of an antigen that is specifically recognized by either B- or T-lymphocytes. B- lymphocytes respond to foreign antigenic determinants via antibody production, whereas T- lymphocytes are the mediator of cellular immunity. Thus, antigenic determinants or epitopes are those parts of an antigen that are recognized by antibodies, or in the context of a Major Histocompatibility Complex (MHC), by T-cell receptors. An antigenic determinant contains one or more epitopes. Preferably, the herein mentioned antigenic determinant is a protein capable of forming a virus- like particle. Preferably, the non-replicating virus antigen according to the present invention is a virus-like particle. Said virus-like particle, which is hereinafter also termed “the virus-like particle according to the present invention”, preferably comprises a recombinant protein (being also termed, as mentioned above, “the recombinant protein according to the present invention”). Preferably, the recombinant protein according to the present invention is a recombinant virus capsid protein. More preferably, the recombinant protein according to the present invention is a recombinant circovirus capsid protein. In still another aspect, the non-replicating virus antigen according to the present invention is a recombinant porcine circovirus (PCV) capsid protein. In particular, the non-replicating virus antigen according to the present invention is a recombinant porcine circovirus type 2 (PCV2) ORF2 protein, wherein said PCV2 ORF2 protein preferably comprises or consists of an amino acid sequence having at least 90%, preferably 23-0041-ff Boehringer Ingelheim Vetmedica GmbH at least 95%, more preferably at least 98%, still more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1. According to another preferred aspect, the non-replicating virus antigen according to the present invention is selected from the group consisting of recombinant PCV2 subtype a (PCV2a) ORF2 protein, recombinant PCV2 subtype b (PCV2b) ORF2 protein, recombinant PCV2 subtype c (PCV2c) ORF2 protein, recombinant PCV2 subtype d (PCV2d) ORF2 protein, recombinant PCV2 subtype e (PCV2e) ORF2 protein, recombinant PCV2 subtype f (PCV2f) ORF2 protein, recombinant PCV2 subtype g (PCV2g) ORF2 protein and recombinant PCV2 subtype h (PCV2h) ORF2 protein. The terms “PCV2a”, “PCV2b”, “PCV2c”, “PCV2d”, “PCV2e”, “PCV2f”, “PCV2g”, “PCV2h”, as used herein, in particular relate to the established PCV2 genotype classification which is described in: Franzo G & Segalés J. PLos One 13(12):e0208585 (2018) and Link EK et al. Virol J.18(1):70 (2021). According to one specific aspect, the non-replicating virus antigen according to the present invention is a recombinant PCV2 genotype a (PCV2a) ORF2 protein. Preferably, the herein mentioned recombinant PCV2a ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1. According to another specific aspect, the non-replicating virus antigen according to the present invention is a recombinant PCV2 genotype d (PCV2d) ORF2 protein. Preferably, the herein mentioned PCV2d ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:2. According to another preferred aspect, the non-replicating virus antigen according to the present invention is a recombinant parvovirus capsid protein. In one aspect, the non-replicating virus antigen according to the present invention is a recombinant porcine parvovirus (PPV) capsid protein, in particular a PPV viral protein 2 (VP2). Preferably, the herein mentioned recombinant PPV VP2 comprises or consists of an amino acid sequence having at least 90%, preferably at least 95%, more preferably at least 98%, still 23-0041-ff Boehringer Ingelheim Vetmedica GmbH more preferably at least 99% or in particular 100% sequence identity with a sequence selected from the group consisting of SEQ ID NO:3. Regarding the term “at least 90%”, as mentioned in the context of the present invention, it is understood that said term preferably relates to “at least 91%”, more preferably to “at least 92%”, still more preferably to “at least 93%” or in particular to “at least 94%”. Regarding the term “at least 95%” as mentioned in the context of the present invention, it is understood that said term preferably relates to “at least 96%”, more preferably to “at least 97%”, still more preferably to “at least 98%” or in particular to “at least 99%”. Regarding the term “at least 99%” as mentioned in the context of the present invention, it is understood that said term preferably relates to “at least 99.2%”, more preferably to “at least 99.4%”, still more preferably to “at least 99.6%” or in particular to “at least 99.8%”. More particular, the term “at least 99% sequence identity” refers to 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9% sequence identity. The term “having 100% sequence identity”, as used herein, is understood to be equivalent to the term “being identical”. As used herein, it is in particular understood that the term “sequence identity with the sequence of SEQ ID NO:X” is equivalent to the term “sequence identity with the sequence of SEQ ID NO:X over the length of SEQ ID NO:X” or to the term “sequence identity with the sequence of SEQ ID NO:X over the whole length of SEQ ID NO:X”, respectively. In this context, “X” is any integer selected from 1 to 3 so that “SEQ ID NO:X” represents any of the SEQ ID NOs mentioned herein. The term "immunogenic composition" refers to a composition that comprises at least one antigen, which elicits an immune response in the host to which the immunogenic composition is administered. Such immune response can be a cellular and / or antibody-mediated immune response to the immunogenic composition according to the invention. The host is also described as "subject". Preferably, any of the hosts or subjects described or mentioned herein is an animal. The term "animal", as used herein, in particular relates to a mammal, preferably to swine, more preferably to a pig, most preferably to a piglet or a sow. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Usually, an "immune response" includes but is not limited to one or more of the following effects: the production or activation of antibodies, B cells, helper T cells, suppressor T cells, and / or cytotoxic T cells and / or gamma-delta T cells, directed specifically to an antigen or antigens included in the immunogenic composition according to the present invention. Preferably, the host will display either a protective immune response or a therapeutic response. A "protective immune response" will be demonstrated by either a reduction or lack of one or more clinical signs normally displayed by an infected host, a quicker recovery time and / or a lowered duration of infectivity or lowered pathogen titer in the tissues or body fluids or excretions of the infected host. For instance, in order to asses a protective immune response against PCV2, PCV2 specific T cell immunity can be evaluated, following the protocol of Koinig HC et al. Vet Res.46:20 (2015). As it is known, and described therein, multi-functional T cells, which simultaneously produce IFN-γ, interleukin-2 (IL-2) and TNF-α, are strongly correlated with protection, and the appearance of IFN-γ / TNF-α co-producing T cells after PCV2 vaccination correlated with prevention of viremia after PCV2 vaccination. Furthermore, a strong correlation is observed between the amount of PCV2 nucleic acid and the severity of PCV2 systemic disease (PCV2-SD) histopathological lesions (Segales J. Virus Res.164(1-2):10-19 (2012). The “pathogen” or “particular pathogen”, as mentioned herein, in particular relates to the virus from which the non-replicating virus antigen is derived. For example, the pathogen, as mentioned herein, is a PCV2 or a PPV. In case where the host displays a protective immune response such that resistance to new infection will be enhanced and / or the clinical severity of the disease reduced, the immunogenic composition is described as a "vaccine". An "antigen" as described herein refers to, but is not limited to, components which elicit an immune response in a host to an immunogenic composition or vaccine of interest comprising such antigen or an immunologically active component thereof. In particular, the term “antigen” as used herein refers to a protein or protein domain, which, if administered to a host, can elicit an immune response in the host. The "inducing of an immune response", “induce an immune response”, or “elicit an immune response”, respectively, generally involves the administration of an effective amount of the immunogenic composition according to the present invention to a subject or herd of subjects in need of or that could benefit from the treatment / prophylaxis caused thereby. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH The term "treatment and / or prophylaxis" refers to the lessening of the incidence of the particular pathogen infection in a herd or the reduction in the severity of one or more clinical signs caused by or associated with the particular pathogen infection. Thus, the term "treatment and / or prophylaxis" also refers to the reduction of the number of animals in a herd that become infected with the particular pathogen (= lessening of the incidence of the particular pathogen infection) or to the reduction of the severity of one or more clinical signs normally associated with or caused by an infection with the pathogen in a group of animals which animals have received an effective amount of the immunogenic composition as provided herein in comparison to a group of animals which animals have not received such immunogenic composition. The term "treatment" refers to the administration of the effective amount of the immunogenic composition once the subject or at least some animals of the herd is / are already infected with such pathogen and wherein such animals already show some clinical signs caused by or associated with such pathogen infection. The term "prophylaxis" refers to the administration to a subject prior to any infection of such subject with a pathogen or at least where such animal or all of the animals in a group of animals do not show one or more clinical signs caused by or associated with the infection by such pathogen. The term "an effective amount" as used herein means, but is not limited to an amount of virus antigen, in particular of the proteins or virus-like particles of the present disclosure, that induces or is able to induce an immune response in a subject. Such effective amount is able to lessen the incidence of the particular pathogen infection in a herd or to reduce the severity of one or more clinical signs of the particular pathogen infection. Preferably, one or more clinical signs are lessened in incidence or severity by at least 10%, more preferably by at least 20%, still more preferably by at least 30%, even more preferably by at least 40%, still more preferably by at least 50%, even more preferably by at least 60%, still more preferably by at least 70%, even more preferably by at least 80%, still more preferably by at least 90%, and most preferably by at least 95% in comparison to subjects that are not treated but subsequently infected by the particular pathogen. Thus, the method of the present invention in particular comprises orally administering an immunogenic composition comprising an effective amount of a non- replicating virus antigen to a subject. The term "clinical signs" as used herein refers to signs of infection of a subject from the particular pathogen. The clinical signs of infection depend on the pathogen selected. Examples 23-0041-ff Boehringer Ingelheim Vetmedica GmbH for such clinical signs, caused by a PCV2 infection, include but are not limited to wasting or weight loss, pallor of the skin, respiratory distress, diarrhea, and occasionally, icterus. Reducing the incidence of or reducing the severity of one or more clinical signs caused by or being associated with the particular pathogen infection in a subject can be reached by the oral administration of one or more doses of the immunogenic composition according to the present invention to a subject. In one aspect, the immunogenic composition comprises at least 10 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 15 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 30 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 50 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 100 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 150 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 200 µg of the non-replicating virus antigen per dose of the immunogenic composition. In one aspect, the immunogenic composition comprises at least 250 µg of the non-replicating virus antigen per dose of the immunogenic composition. In another aspect, the immunogenic composition according to the present invention comprises 10 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 15 to 800 µg of the non-replicating virus antigen per dose. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH In another aspect, the immunogenic composition according to the present invention comprises 30 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 50 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 100 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 150 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 200 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 250 to 800 µg of the non-replicating virus antigen per dose. In another aspect, the immunogenic composition according to the present invention comprises 300 to 800 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 800 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 700 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 600 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 500 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 400 µg of the non-replicating virus antigen per dose. In a further aspect, the immunogenic composition according to the present invention comprises up to 300 µg of the non-replicating virus antigen per dose. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH It is understood that the wording “the immunogenic composition comprises […] of the non- replicating virus antigen per dose of the immunogenic composition” or “the immunogenic composition comprises […] of the non-replicating virus antigen per dose”, respectively, is in particular equivalent to the wording “per dose of the immunogenic composition the antigenic composition comprises […] of the non-replicating virus antigen” or to the wording “the immunogenic composition is formulated to allow administration of […] of the non-replicating virus antigen per dose”, respectively. The term “per dose” or “per dose of the immunogenic composition”, respectively, as used herein, in particular means “per dose of the immunogenic composition which is to be administered to a subject”, in order to achieve a desired effect, namely to induce an immune response, in the subject, and wherein said subject is in particular a pig. Preferably, in particular when administered by oral drench, one dose of the immunogenic composition has a volume of about 1 mL. The gel composition according to the present invention is in particular a gel composition suitable for oral and / or mucosal administration. The term "gel composition", as used herein, refers to a suitable liquid, semi-solid or solid material, which includes an amount of one or more gelling agents effective for gelling the composition. According to another aspect a further preferred aspect, the gel composition according to the present invention comprises water. In particular, said gel composition is a hydrogel composition. Gel compositions according to the present invention, which can be used in the preparation of the immunogenic composition according to the present invention, are readily available. In one example, the commercially available Underline® gel concentrate (Animal Science Products, Nacogdoches, TX (USA)) is used as the gel composition included in the immunogenic composition according to the present invention, but other gel compositions are suitable as well. According to a further preferred aspect, the immunogenic composition according to the present invention is liquid. In one aspect, the immunogenic composition according to the present invention is viscous. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH In another aspect, the immunogenic composition according to the present invention has a viscosity of at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800 cPs (mPa·s) or higher. In one aspect, the immunogenic composition according to the present invention has a viscosity of at least 150 mPa·s (at least 150 cP). In another aspect, the immunogenic composition according to the present invention has a viscosity of at least 100 mPa·s (at least 100 cP). In one aspect, the immunogenic composition according to the present invention has a viscosity of at least 50 mPa·s or at least 50 cP. In another aspect, the immunogenic composition according to the present invention has a viscosity between 50 cP (50 mPa·s) and 150 cP (150 mPa·s). In yet another aspect, the immunogenic composition according to the present invention has a viscosity between 50 cP (50 mPa·s) and 350 cP (350 mPa·s). In one aspect, the immunogenic composition according to the present invention has a viscosity of at least 25 mPa·s or at least 25 cP. In another aspect, the immunogenic composition according to the present invention has a viscosity between 25 cP (25 mPa·s) and 150 cP (150 mPa·s). In yet another aspect, the immunogenic composition according to the present invention has a viscosity between 25 cP (25 mPa·s) and 350 cP (350 mPa·s). The measurement unit of viscosity is Pa·s (pascal second) or mPa·s (millipascal second). The conventional measurement unit is cP (centipoise). A centipoise is one millipascal-second (1 cP = 10-3Pa⋅s = 1 mPa⋅s). According to another aspect, the immunogenic composition according to the present invention is solid. The term "solid" in this context in particular relates to a gel having some resilience or dimensional stability, in contrast to "semi-solid" gels which are smearable and do not have such dimensional stability. The gel composition according to the present invention preferably comprises one or more flavoring agents. It is understood that, as used herein, the wording “comprises or consists of one or more flavoring agents” is in particular encompassed by the wording “comprises a flavoring agent”. The term "flavoring agent" as used herein refers to one or more compounds or mixtures that improve the palatability and / or taste in animals, preferably in pigs. In particular, the flavoring 23-0041-ff Boehringer Ingelheim Vetmedica GmbH agent is, or the one or more flavoring agents are, respectively, capable of attracting pigs. Flavoring agents are well known to the person skilled in the art. Flavoring agents include but are not limited to nutritive and non-nutritive sweeteners, flavor additives, by-products and alternative ingredients. By way of example suitable flavorants include but are not limited to sucrose, glucose, sodium saccharin, sodium cyclamate, xylitol, perillartien, sucralose, D- tryptophan, aspartame, dihydrochalcones and the like, artificial fruit flavoring (e.g., strawberry flavoring), plasma protein (e.g., spray-dried plasma protein), cheese and cheese-like flavorings, dried milk, chocolate and chocolate by-products. Preferably, the one or more flavoring agents comprise or consists of a flavoring agent giving the immunogenic composition according to the present invention a particular taste and / or a flavoring agent giving the immunogenic composition according to the present invention a particular smell. In particular, the one or more flavoring agents comprise or consist of a flavoring agent capable to be tasted by a pig, such as a sweetener, and / or a flavoring agent capable to be smelled by a pig. In particular, the one or more flavoring agents comprise or consists of a sweetener, and a flavor additive capable to be to be smelled by pigs. The sweetener, as mentioned herein, is preferably selected from the group of sucrose, glucose, sodium saccharin, sodium cyclamate, xylitol, perillartine, sucralose, D-tryptophan, aspartame, dihydrochalcones. The flavor additive, as mentioned herein, is preferably selected from the group consisting of artificial fruit flavoring (e.g., strawberry flavoring), and cheese and cheese-like flavorings. Most preferably, the gel composition according to the present invention comprises a sweetener and an artificial fruit flavoring The at least one flavoring agent is preferably incorporated in the immunogenic composition according to the present invention at a concentration of 0.1% to 0.5% by weight. In one aspect, the gel composition according to the present invention further comprises one or more colorants. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH The term "colorant" also may be used in the compositions of the described invention to provide visual cues to the piglets and / or visual verification to animal caretakers that the composition is present, uniformly applied and appropriately adherent. Preferably, the gel composition according to the present invention further comprises one or more colorants capable of attracting pigs. Colorants are well known to the person skilled in the art and include pigments or dyes or a combination thereof. Suitable colorants include, but are not limited to FD&C colorants such as FD&C Blue No.1, FD&C Blue No.2, FD&C Green No.3, Orange B, Citrus Red No.2, FD&C Red No.2, FD&C Red No.3, FD&C Red No.40, FD&C Yellow No.5 and FD&C Yellow No.6. FD&C Blue No. 1 is the dye named Brilliant blue FCF, which is also denoted by E number E133. FD&C Blue No.2 is the dye named indigotine which is also denoted by E number E132. FD&C Green No.3 is the dye Fast Green FCF, which is also denoted by E number E143. FD&C Red No.2 is the dye Amaranth which is also denoted by E number E123, FD&C Red No.3 is the dye erythrosine, which is also denoted by E number E127, FD&C Red No.40 is the dye Allura Red AC, which is also denoted by E number E129. FD&C Yellow No.5 is the dye Tartrazine, which is also denoted by E number E102, FD&C Yellow No.6 is the dye Sunset yellow FCF, which is also denoted by E number 110. The gel composition according to the present invention preferably comprises at least one colorant selected from the group consisting of Brilliant blue FCF, indigotine, Fast Green FCF, Amaranth, erythrosine, Allura Red AC, Tartrazine, Sunset yellow FCF. Preferably, the gel composition according to the present invention comprises the colorants Brilliant blue FCF and Tartrazine. Thus, the at least one colorant, as mentioned herein, is preferably a mixture of Brilliant blue FCF and Tartrazine. Thus, in a preferred aspect, the gel composition according to the present invention has a green color. According to another preferred aspect, the gel composition according to the present invention comprises water and / or an adhesion enhancing agent and / or a pH adjusting agent and / or a stabilizer. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH In one aspect, the at least one adhesion enhancing agent is a hydrophilic polymer or copolymer that is linear or branched, crosslinked, is not biodegradable, or is selected from the group consisting of maltodextrins, hemicellulose extract, hemicellulose, xanthan, guar, pectins, gums, guar derivatives, chitosan, dextran, carrageenans, starch, polyethylene glycol, albumin, cellulose ethers, hyaluronic acid, carboxymethylhydroxyethylcellulose, hydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), carboxy methyl cellulose (CMC), gelatins, vinyl acetates, polyvinyl pyrrolidone, polyvinyl pyrrolidone- vinyl acetate copolymers, polyvinyl alcohols, polyphosphoesters, N-(2-hydroxypropyl) methacryl amide (HPMA) copolymers, polyacrylic acids, polyacrylamides, polyoxazolines, divinyl ether-maleic anhydride, polyphosphazenes, including derivatives and substitutions and salts of any of the foregoing, and combinations thereof. In one aspect, the at least one adhesion enhancing agent is one or more adhesion enhancing agents based on starch and / or hemicellulose. In another aspect, the at least one adhesion enhancing agent(s) is or are maltodextrins and / or hemicellulose extract. In one aspect, the gel composition according to the present invention comprises maltodextrin. In one aspect, the gel composition according to the present invention comprises hemicellulose extract. Preferably, the herein mentioned hemicellulose extract comprises xanthan. In some aspects, in the immunogenic composition according to the present invention the at least one adhesion enhancing agent is in a final concentration (w / v) of about 0.1%, 0.2%, 03%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, or 49%, or any ranges therebetween including, for example, from about 0.5% to 15% w / v, from about 0.5% to 10% w / v, from about 0.5% to 5% w / v, from about 0.5% to 2% w / v. In one aspect, in the immunogenic composition according to the present invention the adhesion enhancing agent is in a final concentration (w / v) of about 0.5% to 15% w / v. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH According to a further preferred aspect, the gel composition according to the present invention comprises one or more pharmaceutically acceptable carriers, in particular selected from the group consisting of stabilizers, pH adjusting compositions, alcohols, glycols, glycerols, and glycerines, lanolin and derivatives thereof, fatty acids and derivatives thereof, fatty alcohols and derivatives thereof, and fatty esters and derivatives thereof, or combinations thereof. Preferably, the one or more pharmaceutically acceptable carriers are selected from the group consisting of propylene glycol (PG), propylene glycol monolaurate (PGML), propylene glycol capryiate, polyethylene glycol monolaurate (PEGML), glycerol monolaurate (GML), methyl formamide (DMF), allantoin, urazole, N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), decylmethylsulfoxide, lecithin, polyoxylglycerides, the 1-substituted azacycloheptan- 2-ones, particularly 1-n-dodecylcyclazacycloheptan-2-one, alcohols, and oils safe for porcine consumption such as vegetable oils. In particular, the gel composition according to the present invention comprises a stabilizer, and wherein the stabilizer is preferably propylene glycol. A "pH adjusting agent" is typically added to bring the pH of the composition to the desired value. Desirable pH values are between about 6 to about 8. The immunogenic compositions of the present invention therefore may be formulated to have a pH value that ranges between about 6 and about 8, or about 6.5 and about 7.5. Suitable pH adjusting agents include, but are not limited to, one or more adipic acids, glycines, citric acids, calcium hydroxides, magnesium aluminometasilicates, disodium phosphate, sodium phosphate, potassium phosphate, potassium chloride, sodium citrate, calcium lactate, sodium succinate, sodium glutamate, sodium bicarbonate, and potassium bicarbonate, and combinations thereof. As used herein, "stabilizer" is an agent that helps stabilize the active agent in the immunogenic composition according to the present invention. The stabilizer includes but is not limited to reducing agents. Stabilizers that may be used include sodium thiosulfate, sodium metabisulfite, sodium bisulfite, sodium sulfite, sulphur dioxide, ammonium bisulfite, and ammonium thiosulfate. Sodium thiosulfate is preferred as it possess a high neutralization ability and is considered safe and not corrosive. The term "stabilizer" also encompasses chelating agents. Chelating agents are optionally added to the gel composition according to the present invention to enhance the preservative or preservative system. Preferred chelating agents are mild agents, such as, for example, ethylenediaminetetraacetic acid (EDTA), EDTA derivatives, or any combination thereof. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Suitable stabilizers or preservatives for use in the immunogenic compositions of the present invention include, without limitation, one or more alkanols, disodium EDTA (ethylenediamine tetraacetate), EDTA salts, EDTA fatty acid conjugates, isothiazolinone, parabens such as methylparaben and propylparaben, propylene glycols, sorbates, urea derivatives such as diazolindinyl urea, or any combinations thereof. In some aspects of the invention, in the immunogenic composition according to the present invention the at least one pharmaceutically acceptable carrier is in a final concentration (v / v) of about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, or 49%, or any ranges therebetween including, for example, about 5% to about 10%, about 10% to about 15%, about 12% to about 13%, about 15% to about 20%, about 20% to about 25%, about 25% to about 30%, about 30% to about 35%, about 35% to about 40%, about 40% to about 45%, and about 45% to about 50%. In one aspect of the present invention the gel composition according to the present invention comprises water, an adhesion enhancing agent and a stabilizer. In one aspect, the gel composition according to the present invention comprises water, an adhesion enhancing agent and a stabilizer and a pH adjusting agent. In one aspect, the gel composition according to the present invention comprises water, maltodextrins, hemicellulose extract, and propylene glycol. In another aspect, the gel composition according to the present invention comprises water, maltodextrins, cellulose, a gum and a stabilizer, preferably the stabilizer is propylene glycol. In one aspect, the gel composition according to the present invention comprises water, maltodextrins, hemicellulose extract, propylene glycol and artificial coloring. According to a particularly preferred aspect, the gel composition according to the present invention comprises or consists of: - water, - maltodextrins, - propylene glycol, 23-0041-ff Boehringer Ingelheim Vetmedica GmbH - hemicellulose extract, - one or more colorants, and - one or more flavoring agents. According to another preferred aspect, the immunogenic composition according to the present invention comprises or contains one or more veterinary-acceptable carriers. In one aspect of the present invention the one or more veterinary-acceptable carriers is a diluent. “Diluent” can include water, saline, dextrose, ethanol, glycerol, and the like. Isotonic agents can include sodium chloride, dextrose, mannitol, sorbitol, and lactose, among others. Stabilizers include albumin and alkali salts of ethylenediaminetetraacetic acid, among others. In one aspect of the present invention the one or more veterinary-acceptable carriers is a physiologic buffer. In one aspect of the present invention the one or more veterinary-acceptable carriers is phosphate buffered saline. Preferably, the one or more veterinary-acceptable carriers are selected from the group consisting of solvents, dispersion media, coatings, stabilizing agents, diluents, preservatives, antibacterial and antifungal agents, isotonic agents, adsorption delaying agents, and combinations thereof. Preferably, the immunogenic composition according to the present invention further comprises sucrose gelatin stabilizer. Preferably, the immunogenic composition can further include one or more other immunomodulatory agents such as, e.g. interleukins, interferons, or other cytokines. According to another aspect, the immunogenic composition according to the present invention comprises or contains an adjuvant. It is understood, in the context of the present invention, that the person skilled in the art will preferably choose an adjuvant suitable for oral administration. Thus, the immunogenic composition according to the present invention preferably comprises or contains an adjuvant suitable for oral administration. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH According to a further aspect, the immunogenic composition according to the present invention comprises or contains at least one immunogenic substance different from the non-replicating virus antigen according to the present invention. In one aspect, the non-replicating virus antigen according to the present invention is a recombinant PCV2a ORF2 protein and said at least one immunogenic substance different from said virus antigen is a recombinant PCV2d ORF2 protein, and wherein preferably said PCV2a ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1, and said PCV2d ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:2. According to a particular preferred aspect, the immunogenic composition according to the present invention comprises said PCV2a ORF2 protein and said PCV2d ORF2 protein in a molar ratio of about 1:1. With reference to the clauses disclosed further below, in some embodiments, the present invention provides the method according to any one of clauses 20 to 26, and 31 to 58, wherein said method is a method for reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject. According to a preferred aspect, the herein mentioned immune response is a protective immune response, in particular a protective immune response against a virus, which virus is of the species having a genome encoding - the non-replicating virus antigen, or - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen. The present invention also provides a method for - inducing an immune response in a subject, and / or 23-0041-ff Boehringer Ingelheim Vetmedica GmbH - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising an effective amount of a non-replicating virus antigen. Preferably, a “virus infection”, as mentioned herein, is an infection with a virus, which virus is of the species having a genome encoding - the non-replicating virus antigen according to the present invention, or - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen according to the present invention. In one aspect, the immunogenic composition according to the present invention is administered by oral drench to the subject. The invention further provides methods for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the methods comprise the steps of: - adding an immunogenic composition comprising non-replicating virus antigen into the liquid food or drinking water of the subject, and - allowing the subject to self-administer the immunogenic composition. Most preferably, in this context of the present invention, the immunogenic composition according to the present invention is added into the drinking water of the subject. The term “self-administering” or “self-administer”, as used herein, in particular means that the subject drinks the liquid food or drinking water, and thereby orally consumes the immunogenic composition according to the present invention. Thus, the term “self-administer”, as used herein, is in particular equivalent to “orally self- administer”. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH In some embodiments, the invention also provides methods for - inducing an immune response against PCV2 in a subject, or - reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the methods comprise the steps of: - adding an immunogenic composition comprising non-replicating PCV2 antigen into the liquid food or drinking water of the subject, and - allowing the subject to self-administer the immunogenic composition, and wherein, with reference to the clauses disclosed further below, said non-replicating PCV2 antigen is preferably a recombinant protein as specified in any one of clauses 20 to 26, and 31. All of the above-mentioned methods for inducing an immune response in a subject and / or for reducing one or more clinical signs, viral load and / or viremia caused by virus infection in a subject will also be termed “the methods according to the present invention” hereinafter. According to one aspect the methods according to the present invention consist of orally administering only one dose of said immunogenic composition to said subject or, respectively, said immunogenic composition is added only once into the liquid food or drinking water of the subject. According to another preferred aspect, in the methods according to the present invention the subject is not pre-vaccinated with a vaccine against a virus, which virus is of the species having a genome encoding the antigenic determinant of said virus antigen. In some embodiments of the present invention, the subject is a PCV2 vaccination naïve subject. In one aspect, in the methods according to the present invention - said immune response, or - said reducing or reduction of one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject 23-0041-ff Boehringer Ingelheim Vetmedica GmbH is obtained by the administration of the immunogenic composition. In another aspect, in the methods according to the present invention - said immune response, or - said reducing or reduction of one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject is obtained without a further administration of a vaccine against a virus to the subject, which virus is of the species having a genome encoding the antigenic determinant of the virus antigen included in said immunogenic composition. In one preferred aspect of the methods according to the present invention, the subject is preferably an animal, in particular a pig. In a further preferred aspect of the methods according to the present invention, the subject is a piglet or a sow. The invention further provides a liquid antigen concentrate for dilution in drinking water or in liquid food, wherein 1 mL of said concentrate comprises about 100 to 800 µg of non-replicating virus antigen, in particular of any of the non-replicating virus antigens described herein in the context of the present invention. Preferably, said concentrate, which is also termed the “liquid antigen concentrate according to the present invention” hereinafter, allows to simply establish a defined volume of drinking water or liquid food containing a desired concentration of the non-replicating virus antigen depending on the self-administering subject and its environment. For example, pigs generally drink 8 to 12 % of their body weight per day, depending on the environmental temperature. Thus, the volume of drinking water consumed over a certain time per pig may be calculated (e.g. on the basis of pre-measured drinking water intake during a certain time period of the previous day around the time of planned vaccination), and an appropriate volume of drinking water containing sufficient antigen can be provided in order to ensure that pigs self-administer at least the desired dose of the antigen within a given time. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 150 to 800 µg of the non-replicating virus antigen. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 200 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 250 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 300 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 400 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 500 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 600 to 800 µg of the non-replicating virus antigen. In one aspect, 1 mL of the liquid antigen concentrate according to the present invention comprises about 700 to 800 µg of the non-replicating virus antigen. The term “liquid”, as used herein, has the ordinary meaning in the art and in particular relates to a respective state of matter at room temperature (25°C) and atmospheric pressure (760 mmHg). The invention further provides a method for enabling the self-immunization against a virus by a subject, comprising the step of diluting a liquid antigen concentrate comprising non- replicating virus antigen, in particular non-replicating virus antigen according to the present invention, in the drinking water of the subject, and wherein said concentrate is in particular a liquid antigen concentrate according to the present invention. The invention also provides a container containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen, in particular non-replicating virus antigen according to the present invention, has been added, and wherein said container is also termed the “container of the present invention” hereinafter. In particular the container according to the present ivnention is a container containing drinking water to which a liquid antigen concentrate according to the present invention has been added. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Said container can be any container used for providing drinking water to a subject. Preferably, said container is selected from the group consisting of a bowl, a vessel and a barrel and / or said container is located in the housing environment of a subject to be vaccinated. The invention also relates to a kit for immunization of a subject, comprising - a liquid antigen concentrate comprising non-replicating virus antigen, in particular non- replicating virus antigen according to the present invention; and - instructions to dilute said liquid antigen concentrate in drinking water or in liquid food to be consumed by the subject. Preferably, said liquid antigen concentrate is a liquid antigen concentrate according to the present invention. With reference to the clauses disclosed further below, said subject, as mentioned herein in the context of said method for enabling the self-immunization against a virus, said kit for immunization, and said container containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added, is preferably a subject as specified in any one of clauses 97 to 99. Most preferably, the herein-mentioned subject is a piglet. EXAMPLES The following examples are only intended to illustrate the present disclosure. They shall not limit the scope of the claims in any way. EXAMPLE 1 Results of Oral PCV2 Vaccination Study Objective: To investigate if Porcine Circovirus type 2 (PCV2) virus like particle (VLP) is immunogenic when given orally, thus being an oral vaccine to prevent against PCV2 disease in swine. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Methods: To investigate the immunogenicity of Porcine Circovirus type 2, virus like particle, oral vaccine for swine, an experiment was conducted with two treatment groups. SPF pigs, being around six weeks of age at study day 0, were randomly assigned to treatment group 1) Non-Vaccinated Control and 2) Oral VLP Vaccine group. These groups were comprised of 7 and 10 pigs, respectively. Pigs in each treatment group were split into two pens. On study day 0, pigs in the Oral VLP Vaccine group received, via oral drench, a 1 mL, 300 µg / mL dose of Porcine Circovirus, type 2d, killed baculovirus vector expressed virus like particle, i.e. recombinant baculovirus expressed PCV2d ORF2 protein (SEQ ID NO:2 (corresponds to SEQ ID NO:1 of WO2015051099)). The PCV2d ORF2 protein had been produced as described in WO2015051099 (Examples 1 to 3), and was then further subjected to a downstream processing as set out in WO 2019191005 (Example 1, without mixing with a carbomer solution (adjuvant)). This vaccine did not contain adjuvant. At study day 0, prior to vaccination, at study day 14 and study day 23 each pig had individual blood drawn for serum collection and antibody measurement. At 23 days post vaccination, all pigs had blood drawn for peripheral blood mononuclear cell (PBMC) extraction to evaluate PCV2 specific T cell immunity, following the protocol of Koinig HC et al. Vet Res. 46:20 (2015). The quantification of IgM in serum was performed with the INGEZIM Circovirus IgG / IgM ELISA kit. At study day 22 oral fluids were also collected to evaluate anti-PCV2 IgA, IgG and IgM antibodies. Quantification of IgG in serum, along with IgA, IgM and IgG in oral fluids was performed following the methods described in Prickett et al. Transbound Emerg Dis.58(2):121-7 (2011). The antigen used for the Prickett et al. (2011) assay was the same PCV2d antigen used to immunize pigs. All blood samples were also submitted to test for PCV2 viremia by PCR. Results: PCV2 viremia was not detected in any pig. The oral vaccine was well tolerated, and no adverse events were observed. Antibody results revealed that the Oral VLP Vaccine led to an increase in anti-PCV2 IgM antibody levels, an effect not observed in the Non-Vaccinated Control group (Figure 1). While both groups had similar IgM antibody levels on study day 0 prior to vaccination, antibody levels in the Oral VLP Vaccine group were significantly higher than the Non-Vaccinated Control group at 14 (p= 0.01) and 23 days post vaccination (p=0.03) (Figure 1). In addition to IgM, a significant increase of anti-PCV2 IgG serum antibody level was also 23-0041-ff Boehringer Ingelheim Vetmedica GmbH observed with oral vaccination. At 23 days post vaccination, the Oral VLP Vaccine group had an average S / P value of 0.665 while the Non-Vaccinated Control group had around a tenfold less antibody concentration with an average S / P value of 0.066 (p=0.034) (Figure 2). To further evaluate immune response, specific anti-PCV2 antibodies were measured in oral fluids following vaccination. This analysis revealed much higher quantities of anti-PCV2 antibodies of the classes of IgA, IgG and IgM of pigs in the Oral VLP Vaccine group (Figure 3). The unexpected observation of a substantive increase of IgA is indicative of a strong mucosal immune response induced by the orally administered PCV2 subunit vaccine. Also, the observation of IgG was surprising, as it could not be expected that an orally applied PCV2 subunit vaccine could lead to a significant serological response. Analysis of cellular immunity revealed that the pigs in the Oral VLP vaccine group developed PCV2 antigen specific T cells while pigs in the Non-Vaccinated Control group did not. At 23 days post vaccination, the Oral VLP vaccine group had PCV2 antigen specific interferon gamma and tumor necrosis factor producing CD4+ T cells, while the Non-Vaccinated Control group did not (Figure 4). Conclusion: These results demonstrate that the oral administration of Porcine Circovirus, type 2, virus like particle was immunogenic in pigs, inducing both cellular and humoral immune response, thus being a method and vaccine to prevent disease caused by PCV2 in pigs. EXAMPLE 2 Results of PCV2 VLP Gel Administration Study Objective: To investigate if Porcine Circovirus type 2 (P aCV2) virus like particle (VLP) is immunogenic when administered to pigs by a gel, thus being an oral and mucosal vaccine to prevent against PCV2 associatedadiseasae in swine.aa Methods: To investigate the immunogenicity of Porcine Circovirus type 2, virus like particle, administered by gel for swine, an experiment was conducted with two treatment groups. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH SPF pigs being, on study day 0, about 6 weeks of age were randomly assigned to treatment group 1) Non-Vaccinated Control and 2) Gel VLP Vaccine group. These groups were comprised of 7 and 10 pigs, respectively. On study day 0, pigs in the Gel VLP Vaccine group were provided an immunogenic composition of the present invention such that for each pig, 100 mL of finally prepared Gel VLP vaccine containing a total of 300 µg of recombinant baculovirus expressed PCV2d ORF2 protein (SEQ ID NO:2 (corresponds to SEQ ID NO:1 of WO2015051099)), said virus antigen herein being also termed “Porcine Circovirus, type 2d, killed baculovirus vector expressed virus like particle” or “PCV2 VLP”, respectively, was made available. The PCV2d ORF2 protein had been produced as described in WO2015051099 (Examples 1 to 3), and was then further subjected to a downstream processing as set out in WO 2019191005 (Example 1, without mixing with a carbomer solution (adjuvant)). The finally prepared Gel VLP Vaccine was manufactured by mixing commercially available Underline® gel concentrate (Animal Science Products, Nacogdoches, TX (USA)) - which has the ingredients: water, maltodextrins, propylene glycol, hemicellulose extract, artificial color, natural and artificial flavor - according to the manufacturer´s specifications with PCV2 VLP in the following ratios: 1 part Underline® gel concentrate was mixed with 2 parts of cold PCV2 VLP liquid. The Gel VLP Vaccine was placed into the housing of the pigs by adding a total of 500 mL thereof (comprising 1,500 µg PCV2 VLP) per pen containing five pigs. This composition was added to two bowls (gruel feeders) per pen to allow for the pigs to consume the gel vaccine mixture on their own. This vaccine did not contain adjuvant. At 23 days post vaccination, all pigs had blood drawn for peripheral blood mononuclear cell (PBMC) extraction to evaluate PCV2 specific T cell immunity, following the protocol of Koinig HC et al. Vet Res.46:20 (2015). All blood samples were also submitted to test for PCV2 viremia by PCR. Results: PCV2 viremia was not detected in any pig. The pigs immediately were attracted to the gel VLP mixture and consumed it entirely. This allowed for the immunization of pigs against PCV2 without needing to individually handle each pig, drastically reducing the labor and time needed to immunize the animals. This vaccine composition was well tolerated, and no adverse events were observed. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Analysis of cellular immunity revealed that the pigs in the Gel VLP Vaccine group developed PCV2 antigen specific T cells while pigs in the Non-Vaccinated Control group did not. At 23 days post vaccination, the Oral VLP vaccine group had PCV2 antigen specific interferon gamma and tumor necrosis factor producing CD4+T cells, while the Non-Vaccinated Control group did not (Figure 5). Conclusion: Porcine Circovirus, type 2, virus like particle when combined with a semi-solid, liquid, gel formulation for consumption was immunogenic to pigs, thus being a method and vaccine to prevent disease caused by PCV2 in pigs. EXAMPLE 3 Results of Oral PCV2 Vaccine Efficacy Evaluation Objective: The objective of this study was to evaluate the efficacy of orally administered Porcine Circovirus type 2 (PCV2) virus like particle (VLP) containing PCV type 2a and PCV type 2d VLPs against a PCV2d challenge in swine. Methods: To investigate the efficacy of Porcine Circovirus type 2, virus like particle, oral vaccine for swine, an experiment was conducted with four treatment groups. These treatment groups consisted of a placebo group as well as groups receiving different concentrations of PCV2 VLP. Caesarian Derived, Colostrum Deprived Colostrum deprived (CDCD) pigs, being around three weeks of age at study day 0, were randomly assigned to treatment groups: T01 Placebo, non-vaccinated and challenged; T02 Oral 1x, vaccinated and challenged; T03 Oral 5x vaccinated and challenged; T04 Oral 10x vaccinated and challenged. Each group was comprised of 25 pigs. Pigs in each treatment group were mixed among pens. On study day 0, pigs in the Oral vaccinated groups received, via oral drench, a 1 mL dose of different concentrations of antigen. Treatment T02 Oral 1x, received 15µg PCV type 2a and 15µg PCV type 2d VLP; Treatment T03 Oral 5x received 75 µg PCV type 2a and 75 µg PCV type 2d VLP and Treatment T04 Oral 10x received 150 µg PCV type 2a and 150 µg PCV type 2d VLP. These antigens were (i) 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Porcine Circovirus, type 2d, killed baculovirus vector expressed virus like particle, i.e. recombinant baculovirus expressed PCV2d ORF2 protein (SEQ ID NO:2 (corresponds to SEQ ID NO:1 of WO2015051099)), which had been produced as described above in Example 1, and (ii) Porcine Circovirus, type 2a, killed baculovirus vector expressed virus like particle, i.e. recombinant baculovirus expressed PCV2a ORF2 protein (SEQ ID NO:1 (corresponds to SEQ ID NO:1 of WO 2019191005)), which had been produced as described in Example 1 of WO 2019191005 (under “Production of PCV2 ORF2 protein – Upstream processing”), and was then further subjected to a downstream processing as set out in WO 2019191005 (Example 1, without mixing with a carbomer solution (adjuvant)). The placebo group received saline solution with the same route and volume as the oral vaccinated groups on study day 0. Animals were challenged on study day 28. Challenge consisted of 1.0 mL intramuscular (IM) administration in the left neck and 1.0 mL of the same material intranasally (IN) into one nostril using a sterile syringe. This challenge targeted a dose of 5.0 log10TCID50Porcine Circovirus type 2d / 2 mL per pig. Blood was collected prior to vaccination (study day -2), prior to challenge (study day 27) as well as weekly post challenge on study days 35, 42 and 49. The study ended on day 49, twenty-one days post challenge. PCV2 viremia was quantified in serum of the collected blood samples by PCR. Results: Prior to challenge, PCV2 viremia was not detected in any pig (Figure 6). The T01 Placebo group developed PCV2 viremia after challenge which peaked at study day 49 with an average of 7.48 log10 PCV2 genomic copies per mL. The oral administration of PCV2 VLP had a clear protective effect in reducing the consequences of PCV2 infection as evidenced by a significant reduction of viremia. This reduction of viremia occurred in all three orally vaccinated treatment groups which were administered different concentrations of PCV2 VLP antigen (Figure 6). At study day 49, the T02 Oral 1x group led to a 1.676 log10PCV2 genomic copies / mL reduction of viremia compared to the T01 Placebo group (Figure 6). The effect of PCV2 VLP antigen concentration was also observed, as groups which were administered higher antigen concentrations had lower levels of viremia. This further highlights the immunogenic and protective effect of orally administered PCV2 VLP antigen. On both study day 42 and 49, there was a significant difference among PCV2 levels in serum of T02 Oral 1x and T04 Oral 10x groups. These differences were of 2.390 log10and 1.951 log10PCV2 genomic copies per mL, respectively. The T03 Oral 5x group had average viremia levels that were intermediary to those of the T02 Oral 1x and T04 Oral 10x treatment groups at all three time points post challenge (Figure 6). The T04 Oral 10x group had the lowest levels of viremia. A lower level of PCV2 23-0041-ff Boehringer Ingelheim Vetmedica GmbH viremia was found between the T04 Oral 10x and the T01 Placebo group at all time points following challenge (Figure 6). The difference in PCV2 viremia levels among both treatments was of 1.435 log10, 3.432 log10 and 3.627 log10 PCV2 genomic copies / mL at study days 35, 42 and 49, respectively. Conclusion: These results demonstrate that the oral administration of Porcine Circovirus, type 2, virus like particle mitigated infection and thus was protective against infection, thus being a method and vaccine to prevent disease caused by PCV2 in pigs. LIST OF FIGURES: Figure 1 (“Fig.1”): Average S / P value of PCV2 specific IgM in Negative Control and Oral VLP Vaccine groups at 0, 14 and 23 days post vaccination. dpv = days post vaccination different letters indicate statistical significance within each time point (p<0.05). Within the pairs of bars shown in the chart, the left bar is designated “Non-vaccinated Control” and the right bar is designated “Oral VLP vaccine”. Figure 2 (“Fig.2”). Average S / P value of PCV2 specific IgG in Negative Control and Oral VLP Vaccine groups at 0 days post vaccination and 14 days post vaccination. dpv = days post vaccination. different letters indicate statistical significance within each time point (p<0.05). Within the pairs of bars shown in the chart, the left bar is designated “Non-vaccinated Control” and the right bar is designated “Oral VLP vaccine". Figure 3 (“Fig.3”): Average S / P value of PCV2 specific IgA, IgG and IgM in Negative Control and Oral VLP Vaccine groups at 22 days post vaccination quantified in oral fluids. Within the pairs of bars shown in the chart, the left bar is designated “Non-vaccinated Control” and the right bar is designated “Oral VLP vaccine". Figure 4 (“Fig.4”): Percentage of interferon gamma (IFNg) and tumor necrosis factor alpha (TNFa) positive PCV2 antigen specific CD4+ T cells measured in blood of pigs at 23 days post vaccination. 23-0041-ff Boehringer Ingelheim Vetmedica GmbH Figure 5 (“Fig.5”): Percentage of interferon gamma (IFNg) and tumor necrosis factor alpha (TNFa) positive PCV2 antigen specific CD4+T cells measured in blood of pigs at 23 days post vaccination. Figure 6 (“Fig.6”): Average PCV2 genomic copies of PCV2 in serum from different treatment groups and different timepoints. Sequences included in the sequence listing: SEQ ID NO:1 SEQ ID NO:1 corresponds to the sequence of a PCV2a ORF2 protein (being 233 amino acid residues in length). SEQ ID NO:1 has the amino acid sequence (in the one letter code for amino acid residues, from N- to C-terminus, including an N-terminal methionine residue (M) at amino acid position 1): MTYPRRRYRRRRHRPRSHLGQILRRRPWLVHPRHRYRWRRKNGIFNTRLSRTFGYTVKAT TVTTPSWAVDMMRFNIDDFVPPGGGTNKISIPFEYYRIRKVKVEFWPCSPITQGDRGVGS TAVILDDNFVTKATALTYDPYVNYSSRHTIPQPFSYHSRYFTPKPVLDSTIDYFQPNNKR NQLWLRLQTSRNVDHVGLGTAFENSKYDQDYNIRVTMYVQFREFNLKDPPLEP SEQ ID NO:2 SEQ ID NO:2 corresponds to the sequence of a PCV2d ORF2 protein (being 234 amino acid residues in length). SEQ ID NO:2 has the amino acid sequence (in the one letter code for amino acid residues, from N- to C-terminus, including an N-terminal methionine residue (M) at amino acid position 1): MTYPRRRFRRRRHRPRSHLGQILRRRPWLVHPRHRYRWRRKNGIFNTRLSRTIGYTVKKT TVTTPSWNVDMMRFNINDFLPPGGGSNPLTVPFEYYRIRKVKVEFWPCSPITQGDRGVGS TAVILDDNFVTKANALTYDPYVNYSSRHTITQPFSYHSRYFTPKPVLDRTIDYFQPNNKR NQLWLRLQTTGNVDHVGLGTAFENSIYDQDYNIRITMYVQFREFNLKDPPLNPK SEQ ID NO:3 SEQ ID NO:3 corresponds to the sequence of a PPV VP2 (being 579 amino acid residues in length). SEQ ID NO:3 has the amino acid sequence (in the one letter code for amino acid residues, from N- to C-terminus, including an N-terminal methionine residue (M) at amino acid position 1): 23-0041-ff Boehringer Ingelheim Vetmedica GmbH MSENVEQHNPINAGTELSATGNESIGGGGGGGGRGSIGVGVSTGSFNNQTEFQYLGEGLV RITAHASRLIHLNMPEHETYKRIHVLNSESGVAGQMVQDDAHTQMVTPWSLIDANAWGVW FNPADWQLISNNMTEINLVSFEQEIFNVVLKTITESATSPPTKIYNNDLTASLMVALDTN NTLPYTPAAPRSETLGFYPWLPTKPTQYRYYLSCTRNLNPPTYTGQSEQITDSIQTGLHS DIMFYTIENAVPIHLLRTGDEFSTGIYHFDTKPLKLTHSWQTNRSLGLPPKLLTEPTTEG DQHPGTLPAANTRKGYHQTINNSYTEATAIRPAQVGYNTPYMNFEYSNGGPFLTPIVPTA DTQYNDDEPNGAIRFTMGYQHGQLTTSSQELERYTFNPQSKCGRAPKQQFNQQSPLNLQN TNNGTLLPSDPIGGKTNMHFMNTLNTYGPLTALNNTAPVFPNGQIWDKELDTDLKPRLHV TAPFVCKNNPPGQLFVKIAPNLTDDFNADSPQQPRIITYSNFWWKGTLTFTAKMRSSNMW NPIQQHTTTAENIGNYIPTNIGGIKMFPEYSQLIPRKLY The following clauses are also disclosed herein. Thus, the present disclosure further includes aspects as featured by the following clauses: 1. A method for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. 2. The method according to clause 1, wherein said method is a method for - inducing an immune response in a subject, and - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen. 3. The method according to clause 1 or 2, wherein said immune response is an immune response against a virus. 4. The method according to any one of clauses 1 to 3, wherein said immune response is a protective immune response. -0041-ff Boehringer Ingelheim Vetmedica GmbH 5. The method according to clause 3 or 4, wherein said virus is a virus, which is of the species having a genome encoding - the non-replicating virus antigen, or - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen. 6. The method according to clause 5, wherein said antigenic determinant is a protein capable of forming a virus-like particle. 7. The method according to any one of clauses 1 to 6, wherein the immunogenic composition is free of replicating virus antigen. 8. The method according to any one of clauses 1 to 7, wherein the immunogenic composition consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers. 9. The method according to any one of clauses 1 to 7, wherein the immunogenic composition consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one adjuvant. 10. The method according to any one of clauses 1 to 7, wherein the immunogenic composition consists of a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one immunogenic substance different from said virus antigen. 11. The method according to any one of clauses 1 to 7, wherein the immunogenic composition consists of -0041-ff Boehringer Ingelheim Vetmedica GmbH a non-replicating virus antigen; and one or more veterinary-acceptable carriers; and at least one adjuvant; and at least one immunogenic substance different from said virus antigen. 12. The method according to any one of clauses 1 to 11, wherein the immunogenic composition additionally contains a gel composition. 13. The method according to any one of clauses 1 to 12, wherein the non-replicating virus antigen comprises or is a recombinant protein. 14. The method according to clause 13, wherein the recombinant protein is capable of forming a virus-like particle. 15. The method according to any one of clauses 1 to 14, wherein the non-replicating virus antigen is a virus-like particle. 16. The method according to any one of clauses 1 to 15, wherein the non-replicating virus antigen is a virus-like particle comprising a recombinant protein. 17. The method according to any one of clauses 13 to 16, wherein the recombinant protein is a recombinant virus capsid protein. 18. The method according to any one of clauses 13 to 17, wherein the recombinant protein is a recombinant circovirus capsid protein. 19. The method according to any one of clauses 13 to 18, wherein the recombinant protein is a recombinant porcine circovirus (PCV) capsid protein. 20. The method according to any one of clauses 13 to 19, wherein the recombinant protein is a recombinant porcine circovirus type 2 (PCV2) ORF2 protein. 21. The immunogenic composition according to clause 20, wherein said PCV2 ORF2 protein comprises or consists of an amino acid sequence having at least 90%, preferably at least 95%, more preferably at least 98%, still more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1 or SEQ ID NO:2. -0041-ff Boehringer Ingelheim Vetmedica GmbH 22. The method according to any one of clauses 13 to 21, wherein the recombinant protein is selected from the group consisting of recombinant PCV2 subtype a (PCV2a) ORF2 protein, recombinant PCV2 subtype b (PCV2b) ORF2 protein, recombinant PCV2 subtype c (PCV2c) ORF2 protein, recombinant PCV2 subtype d (PCV2d) ORF2 protein, recombinant PCV2 subtype e (PCV2e) ORF2 protein, recombinant PCV2 subtype f (PCV2f) ORF2 protein, recombinant PCV2 subtype g (PCV2g) ORF2 protein and recombinant PCV2 subtype h (PCV2h) ORF2 protein. 23. The method according to any one of clauses 13 to 22, wherein the recombinant protein is a recombinant PCV2 subtype a (PCV2a) ORF2 protein. 24. The method according to clauses 22 or 23, wherein said PCV2a ORF2 protein comprises or consists of an amino acid sequence having at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1. 25. The method according to any one of clauses 13 to 22, wherein the recombinant protein is a recombinant PCV2 subtype d (PCV2d) ORF2 protein. 26. The method according to clause 22 or 25, wherein said PCV2d ORF2 protein comprises or consists of an amino acid sequence having at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:2. 27. The method according to any one of clauses 13 to 17, wherein the recombinant protein is a recombinant parvovirus capsid protein. 28. The method according to any one of clauses 13 to 17, and 27, wherein the recombinant protein is a recombinant porcine parvovirus (PPV) capsid protein. 29. The method according to any one of clauses 13 to 17, 27 and 28, wherein the recombinant PPV is a recombinant PPV viral protein 2 (VP2). 30. The method according to clause 29, wherein said PPV VP2 comprises or consists of an amino acid sequence having at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:3. -0041-ff Boehringer Ingelheim Vetmedica GmbH 31. The method according to any one of clauses 13 to 30, wherein said recombinant protein is a recombinant baculovirus expressed protein. 32. The method according to any one of clauses 1 to 31, wherein the immunogenic composition comprises at least 10 µg of the non-replicating virus antigen per dose, or wherein the immunogenic composition comprises at least 15 µg of the non- replicating virus antigen per dose. 33. The method according to any one of clauses 1 to 32, wherein the immunogenic composition comprises at least 30 µg of the non-replicating virus antigen per dose, or wherein the immunogenic composition comprises at least 50 µg of the non- replicating virus antigen per dose. 34. The method according to any one of clauses 1 to 33, wherein the immunogenic composition comprises at least 100 µg of the non-replicating virus antigen per dose. 35. The method according to any one of clauses 1 to 34, wherein the immunogenic composition comprises at least 150 µg of the non-replicating virus antigen per dose. 36. The method according to any one of clauses 1 to 35, wherein the immunogenic composition comprises at least 200 µg of the non-replicating virus antigen per dose. 37. The method according to any one of clauses 1 to 36, wherein the immunogenic composition comprises at least 250 µg of the non-replicating virus antigen per dose. 38. The method according to any one of clauses 1 to 37, wherein one dose of the immunogenic composition has a volume of about 1 mL. 39. The method according to any one of clauses 1 to 38, wherein said immunogenic composition comprises or contains one or more veterinary-acceptable carriers. 40. The method according to any one of clauses 1 to 39, wherein said one or more veterinary acceptable carriers are selected from the group consisting of solvents, -0041-ff Boehringer Ingelheim Vetmedica GmbH dispersion media, coatings, stabilizing agents, diluents, preservatives, antibacterial and antifungal agents, isotonic agents, adsorption delaying agents. 41. The method according to any one of clauses 1 to 7, 9, and 11 to 40, wherein the immunogenic composition comprises or contains at least one adjuvant. 42. The method composition according to any one of clauses 1 to 7, and 10 to 41, wherein the immunogenic composition comprises or contains at least one immunogenic substance different from said non-replicating virus antigen. 43. The method according to any one of clauses 1 to 7, 10 to 26, and 31 to 42, wherein said non-replicating virus antigen is a recombinant PCV2a ORF2 protein, and wherein the at least one immunogenic substance different from said virus antigen is a recombinant PCV2d ORF2 protein. 44. The method according to clause 43, wherein said PCV2a ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1, and wherein said PCV2d ORF2 protein comprises or consists of an amino acid sequence having at least at least 95%, preferably at least 98%, more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:2. 45. The method according to any one of clauses 12 to 44, wherein the gel composition is a gel composition suitable for oral administration. 46. The method according to any one of clauses 12 to 45, wherein said gel composition comprises water. 47. The method according to any one of clauses 12 to 46, wherein said gel composition is a hydrogel composition. 48. The method according to any one of clauses 12 to 47, wherein said gel composition comprises one or more flavoring agents. 49. The method according to any one of clauses 12 to 48, wherein the one or more flavoring agents are selected from the group consisting of sucrose, glucose, -0041-ff Boehringer Ingelheim Vetmedica GmbH sodium saccharin, sodium cyclamate, xylitol, perillartien, sucralose, D-tryptophan, aspartame, dihydrochalcones, artificial fruit flavoring (e.g., strawberry flavoring), plasma protein (e.g., spray-dried plasma protein), cheese and cheese-like flavorings, dried milk, chocolate and chocolate by-products. 50. The method according to any one of clauses 12 to 49, wherein the one or more flavoring agents are capable of attracting pigs. 51. The method according to any one of clauses 12 to 50, wherein said gel composition comprises one or more colorants, in particular one or more colorants capable of attracting pigs. 52. The method according to any one of clauses 12 to 51, wherein the one or more colorants are, selected from the group consisting of FD&C Blue No.1, FD&C Blue No.2, FD&C Green No.3, Orange B, Citrus FD&C Red No.2, FD&C Red No.2, FD&C Red No.3, FD&C Red No.40, FD&C Yellow No.5 and FD&C Yellow No.6. 53. The method according to any one of clauses 12 to 52, wherein said gel composition comprises maltodextrin. 54. The method according to any one of clauses 12 to 53, wherein said gel composition comprises hemicellulose extract. 55. The method according to any one of clauses 12 to 54, wherein said gel composition comprises propylene glycol. 56. The method according to any one of clauses 12 to 55, wherein said gel composition comprises or consists of: - water, - maltodextrins, - propylene glycol, - hemicellulose extract, - one or more colorants, and - one or more flavoring agents. -0041-ff Boehringer Ingelheim Vetmedica GmbH 57. The method according to any one of clauses 3 to 26, and 31 to 56, wherein said virus is PCV2. 58. The method according to any one of clauses 20 to 26, and 31 to 57, wherein the immune response is an immune response against PCV2. 59. The method according to any one of clauses 20 to 26, and 31 to 58, wherein said method is a method for reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject. 60. The method according to any one of clauses 1 to 59, wherein the immunogenic composition is administered by oral drench to the subject. 61. A method for inducing an immune response in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating virus antigen into the liquid food or drinking water of the subject, and allowing the subject to self-administer the immunogenic composition . 62. The method according to clause 61, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 63. The method according to clause 61 or 62, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 16 and / or wherein said non-replicating virus antigen comprises a recombinant protein as specified in any one of clauses 17 to 31. 64. The method according to any one of clauses 61 to 63, wherein said immune response is a protective immune response. 65. The method according to any one of clauses 61 to 63, wherein said immune response is an immune response against a virus. 66. The method according to clause 65, wherein said immune response against a virus is an immune response against a virus, which virus is of the species having a genome encoding - the non-replicating virus antigen, or -0041-ff Boehringer Ingelheim Vetmedica GmbH - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen. 67. A method for inducing an immune response against PCV2 in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating PCV2 antigen into the liquid food or drinking water of the subject, and allowing the subject to self-administer the immunogenic composition. 68. The method according to clause 67, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 69. The method according to clause 67 or 68, wherein said non-replicating PCV2 antigen is a recombinant protein as specified in any one of clauses 20 to 26, and 31. 70. A method for reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating virus antigen into the liquid food or drinking water of the subject, and allowing the subject to self-administer the immunogenic composition. 71. The method according to clause 70, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 72. The method according to clause 70 or 71, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 16 and / or wherein said non-replicating virus antigen comprises a recombinant protein as specified in any one of clauses 17 to 31. 73. The method according to any one of clauses 65 to 69, wherein said immune response is a protective immune response, in particular a protective immune response against a virus, which virus is of the species having a genome encoding - the non-replicating virus antigen, or -0041-ff Boehringer Ingelheim Vetmedica GmbH - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen. 74. A method for reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating PCV2 antigen into the liquid food or drinking water of the subject, and allowing the subject to self-administer the immunogenic composition. 75. The method according to clause 74, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 76. The method according to clause 74 or 75, wherein said non-replicating PCV2 antigen is a recombinant protein as specified in any one of clauses 20 to 26, and 31. 77. An immunogenic composition comprising non-replicating virus antigen for use in a method for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject. 78. The immunogenic composition for use according to clause 77, wherein said method is a method as specified in any one of clauses 1 to 6, and 57 to 60. 79. The immunogenic composition for use according to clause 77 or 78, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 80. The immunogenic composition for use according to any one of clauses 77 to 79, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 16 and / or wherein said non-replicating virus -0041-ff Boehringer Ingelheim Vetmedica GmbH antigen comprises a recombinant protein as specified in any one of clauses 17 to 31. 81. An immunogenic composition comprising non-replicating PCV2 antigen for use in a method for - inducing an immune response against PCV2 in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject. 82. The immunogenic composition for use according to clause 81, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 83. The immunogenic composition for use according to clause 81 or 82, wherein said non-replicating PCV2 antigen is a recombinant protein as specified in any one of clauses 20 to 26, and 31. 84. Use of an immunogenic composition comprising non-replicating virus antigen in the preparation of a medicament for use in a method for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject. 85. The use according to clause 84, wherein said method is a method as specified in any one of clauses 1 to 6, and 57 to 60. 86. The use according to clause 84 or 85, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 56. -0041-ff Boehringer Ingelheim Vetmedica GmbH 87. The use according to any one of clauses 84 to 86, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 30. 88. Use of an immunogenic composition comprising non-replicating PCV2 antigen in the preparation of a medicament for use in a method for - inducing an immune response against PCV2 in a subject, or - reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject. 89. Use according to clause 88, wherein said immunogenic composition is an immunogenic composition as specified in any one of clauses 7 to 12, and 32 to 56. 90. Use according to clause 88 or 89, wherein said non-replicating PCV2 antigen is a recombinant protein as specified in any one of clauses 20 to 26, and 31. 91. The method according to any one of clauses 1 to 68, the immunogenic composition according to any one of clauses 77 to 83, or the use according to any one of clauses 84 to 90, wherein the method consists of orally administering only one dose of said immunogenic composition to said subject. 92. The method according to any one of clauses 69 to 76, wherein said immunogenic composition is added only once into the liquid food or drinking water of the subject. 93. The method according to any one of clauses 1 to 76, 91 and 92, the immunogenic composition according to any one of clauses 77 to 83, and 91, or the use according to any one of clauses 84 to 91, wherein the subject is not pre-vaccinated with a vaccine against a virus, which virus is of the species having a genome encoding the antigenic determinant of said non-replicating virus antigen. 94. The method according to any one of clauses 1 to 76, and 91 to 93, the immunogenic composition according to any one of clauses 77 to 83, 91 and 93, or the use according to any one of clauses 84 to 91, and 93, wherein the subject is a PCV2 vaccination naïve subject. -0041-ff Boehringer Ingelheim Vetmedica GmbH 95. The method according to any one of clauses 1 to 76, and 91 to 94, the immunogenic composition according to any one of clauses 77 to 83, 91, 93, and 94, or the use according to any one of clauses 84 to 91, 93, and 94, wherein - said immune response, or - said reduction of one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject is obtained by said administration of said immunogenic composition. 96. The method according to any one of clauses 1 to 68, and 91 to 95, the immunogenic composition according to any one of clauses 77 to 83, 91, and 93 to 95, or the use according to any one of clauses 84 to 91, and 93 to 95, wherein - said immune response, or - the reduction of one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject is obtained without a further administration of a vaccine against a virus to the subject, which virus is of the species having a genome encoding the antigenic determinant of the non-replicating virus antigen included in said immunogenic composition. 97. The method according to any one of clauses 1 to 76, and 91 to 96, the immunogenic composition according to any one of clauses 77 to 83, 91, and 93 to 95, or the use according to any one of clauses 84 to 91, and 93 to 96, wherein the subject is an animal. 98. The immunogenic composition according to clause 97, the method according to clause 97, or the use according to clause 97, wherein the subject is a pig. 99. The immunogenic composition according to clause 97 or 98, the method according to clause 97 or 98, or the use according to clause 97 or 98, wherein the subject is a piglet or a sow. 100. The method according to any one of clauses 1 to 76, and 91 to 99, the immunogenic composition according to any one of clauses 77 to 83, 91, and 93 to -0041-ff Boehringer Ingelheim Vetmedica GmbH 99, or the use according to any one of clauses 84 to 91, and 93 to 99, wherein the immunogenic composition comprises 10 to 800 µg of said non-replicating virus antigen per dose. 101. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 15 to 800 µg of said non-replicating virus antigen per dose. 102. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 30 to 800 µg of said non-replicating virus antigen per dose. 103. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 50 to 800 µg of said non-replicating virus antigen per dose. 104. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 100 to 800 µg of said non-replicating virus antigen per dose. 105. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 150 to 800 µg of said non-replicating virus antigen per dose. 106. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 200 to 800 µg of said non-replicating virus antigen per dose. 107. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic composition comprises 250 to 800 µg of said non-replicating virus antigen per dose. 108. The method according to clause 100, the immunogenic composition according to clause 100, or the use according to clause 100, wherein the immunogenic -0041-ff Boehringer Ingelheim Vetmedica GmbH composition comprises 300 to 800 µg of said non-replicating virus antigen per dose. 109. The method according to any one of clauses 1 to 76, and 91 to 108, the immunogenic composition according to any one of clauses 77 to 83, 91, and 93 to 108, or the use according to any one of clauses 84 to 91, and 93 to 108,wherein the immunogenic composition comprises up to 800 µg of said non-replicating virus antigen per dose. 110. The method according to clause 109, the immunogenic composition according to clause 109, or the use according to clause 109, wherein the immunogenic composition comprises up to 700 µg of said non-replicating virus antigen per dose. 111. The method according to clause 109, the immunogenic composition according to clause 109, or the use according to clause 109, wherein the immunogenic composition comprises up to 600 µg of said non-replicating virus antigen per dose. 112. The method according to clause 109, the immunogenic composition according to clause 109, or the use according to clause 109, wherein the immunogenic composition comprises up to 500 µg of said non-replicating virus antigen per dose. 113. The method according to clause 109, the immunogenic composition according to clause 109, or the use according to clause 109, wherein the immunogenic composition comprises up to 400 µg of said non-replicating virus antigen per dose. 114. The method according to clause 109, the immunogenic composition according to clause 109, or the use according to clause 109, wherein the immunogenic composition comprises up to 300 µg of said non-replicating virus antigen per dose. 115. A liquid antigen concentrate for dilution in drinking water or in liquid food, wherein 1 mL of said concentrate comprises about 100 to 800 µg of non-replicating virus antigen. 116. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 150 to 800 µg of non-replicating virus antigen. 117. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 200 to 800 µg of non-replicating virus antigen. -0041-ff Boehringer Ingelheim Vetmedica GmbH 118. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 250 to 800 µg of non-replicating virus antigen. 119. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 300 to 800 µg of non-replicating virus antigen. 120. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 400 to 800 µg of non-replicating virus antigen. 121. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 500 to 800 µg of non-replicating virus antigen. 122. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 600 to 800 µg of non-replicating virus antigen. 123. The liquid antigen concentrate according to clause 115, wherein 1 mL of said concentrate comprises about 700 to 800 µg of non-replicating virus antigen. 124. The antigen concentrate according to any one of clauses 115 to 123,, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 30, and / or wherein said non-replicating virus antigen is baculovirus expressed. 125. Method for enabling the self-immunization against a virus by a subject, comprising the step of diluting a liquid antigen concentrate comprising non-replicating virus antigen in the drinking water of the subject. 126. Container containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added. 127. The container according to clause 126, wherein said container is selected from the group consisting of bowl, vessel and barrel. 128. The container according to clause 126 or 127, wherein said container is located in the housing environment of a subject to be vaccinated. 129. Kit for immunization of a subject, comprising - a liquid antigen concentrate comprising non-replicating virus antigen; and -0041-ff Boehringer Ingelheim Vetmedica GmbH - instructions to dilute said liquid antigen concentrate in drinking water or in liquid food to be consumed by the subject. 130. The method according to clause 125, the container according to any one of clauses 126 to 128, or the kit according to clause 129, wherein said non-replicating virus antigen is a non-replicating virus antigen as specified in any one of clauses 13 to 30, and / or wherein said non-replicating virus antigen is baculovirus expressed. 131. The method according to clause 125 or 130, the container according to any one of clauses 126 to 128, and 130, or the kit according to clause 129 or 130, wherein said liquid antigen concentrate is the liquid antigen concentrate according to any one of clauses 115 to 124. 132. The method according to any one of clauses 125, 130, and 131, the container of clause 128, 130 and 131, or the kit according to any one of clauses 129 to 131, wherein said subject is a subject as specified in any one of clauses 97 to 99.

Claims

23-0041-ff Boehringer Ingelheim Vetmedica GmbH CLAIMS:

1. A method for - inducing an immune response in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, the method comprising administering orally to the subject an immunogenic composition comprising non-replicating virus antigen.

2. A method for inducing an immune response against PCV2 in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating PCV2 antigen into the drinking water of the subject or liquid food of the subject, and allowing the subject to self-administer the immunogenic composition.

3. A method for reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the method comprising the steps of: adding an immunogenic composition comprising non-replicating virus antigen into the drinking water of the subject or the liquid food of the subject, and allowing the subject to self-administer the immunogenic composition.

4. A method for reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the method comprises the steps of: adding an immunogenic composition comprising non-replicating PCV2 antigen into the drinking water of the subject or the liquid food of the subject, and allowing the subject to self-administer the immunogenic composition.

5. An immunogenic composition comprising non-replicating virus antigen for use in a method for - inducing an immune response in a subject, and / or-0041-ff Boehringer Ingelheim Vetmedica GmbH - reducing one or more clinical signs, viral load and / or viremia caused by a virus infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject.

6. An immunogenic composition comprising non-replicating PCV2 antigen for use in a method for - inducing an immune response against PCV2 in a subject, and / or - reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject, wherein the method comprises orally administering said immunogenic composition to said subject, 7. The method according to claim 1, or the immunogenic composition for use according to claim 5, wherein said immune response is an immune response against a virus, wherein said virus is preferably a virus, which is of the species having a genome encoding - the non-replicating virus antigen, or - the amino acid sequence of the antigenic determinant of the non-replicating virus antigen.

8. The method according to any one of claims 1, 3, and 7, or the immunogenic composition for use according to claim 5 or 7, wherein said virus is PCV2; and / or wherein the immune response is an immune response against PCV2; and / or wherein said method is a method for reducing one or more clinical signs, viral load and / or viremia caused by a PCV2 infection in a subject.

9. The method according to claim 1 or 3, or the immunogenic composition for use according to claim 5, wherein said virus infection is an infection with a virus, which virus is of the species having a genome encoding-0041-ff Boehringer Ingelheim Vetmedica GmbH - said non-replicating virus antigen, or - the amino acid sequence of the antigenic determinant of said non-replicating virus antigen.

10. The method of any one of claims 7 to 9, or the immunogenic composition for use according to any one of claims 7 to 9, wherein said antigenic determinant is a protein capable of forming a virus-like particle.

11. The method according to any one of claims 1 to 4, and 7 to 10, or the immunogenic composition for use according to any one of claims 5 to 10, wherein the immunogenic composition is free of replicating virus antigen.

12. The method according to any one of claims 1 to 4, and 7 to 11, or the immunogenic composition for use according to any one of claims 5 to 11, wherein the immunogenic composition consists of - said non-replicating virus antigen; and - one or more veterinary-acceptable carriers, or wherein the immunogenic composition consists of - said non-replicating virus antigen; and - one or more veterinary-acceptable carriers; - and optionally at least one adjuvant and / or optionally at least one immunogenic substance different from said virus antigen.

13. The method according to any one of claims 1 to 4, and 7 to 12, or the immunogenic composition for use according to any one of claims 5 to 12, wherein the immunogenic composition additionally contains a gel composition, in particular a hydrogel composition, and wherein optionally the gel composition comprises one or more flavoring agents, and wherein the one or more flavoring agents are preferably capable of attracting pigs,-0041-ff Boehringer Ingelheim Vetmedica GmbH and / or wherein the one or more flavoring agents are preferably selected from the group consisting of sucrose, glucose, sodium saccharin, sodium cyclamate, xylitol, perillartien, sucralose, D-tryptophan, aspartame, dihydrochalcones, artificial fruit flavoring (e.g., strawberry flavoring), plasma protein (e.g., spray-dried plasma protein), cheese and cheese-like flavorings, dried milk, chocolate and chocolate by-products.

14. The method according to any one of claims 1 to 4, and 7 to 13, or the immunogenic composition for use according to any one of claims 5 to 13, wherein said non- replicating virus antigen comprises or is a recombinant protein, and wherein the recombinant protein is preferably capable of forming a virus-like particle.

15. The method according to any one of claims 1 to 4, and 7 to 14, or the immunogenic composition for use according to any one of claims 5 to 14 wherein said non- replicating virus antigen is - a virus-like particle, in particular a virus-like particle comprising a recombinant protein.

16. The method according to claim 14 or 15, or the immunogenic composition for use according to claim 14 or 15, wherein the recombinant protein is - a recombinant virus capsid protein, and / or - a recombinant circovirus capsid protein or a recombinant parvovirus capsid protein, and / or - a recombinant porcine circovirus (PCV) capsid protein or a recombinant porcine parvovirus (PPV) capsid protein, and / or - a recombinant porcine circovirus type 2 (PCV2) ORF2 protein, wherein said PCV2 ORF2 protein comprises or consists of an amino acid sequence having at least 90%, preferably at least 95%, more preferably at least 98%, still more preferably at least 99% or in particular 100% sequence identity with the sequence of SEQ ID NO:1 or SEQ ID NO:2;-0041-ff Boehringer Ingelheim Vetmedica GmbH and / or wherein said recombinant protein is a recombinant baculovirus expressed protein.

17. The method according to any one of claims 1 to 4, and 7 to 16, or the immunogenic composition for use according to any one of claims 5 to 16, wherein the immunogenic composition comprises at least 10 µg of the non-replicating virus antigen per dose, or at least 15 µg of the non-replicating virus antigen per dose, or at least 30 µg of the non-replicating virus antigen per dose, or at least 50 µg of the non-replicating virus antigen per dose, or at least 100 µg of the non-replicating virus antigen per dose, or at least 150 µg of the non-replicating virus antigen per dose, or at least 200 µg of the non-replicating virus antigen per dose, or at least 250 µg of the non-replicating virus antigen per dose.

18. The method according to any one of claims 12 to 17, or the immunogenic composition for use according to any one of claims 12 to 17, wherein said one or more veterinary-acceptable carriers are selected from the group consisting of solvents, dispersion media, coatings, stabilizing agents, diluents, preservatives, antibacterial and antifungal agents, isotonic agents, adsorption delaying agents.

19. The method according to any one of claims 1, 2, and 7 to 18, or the immunogenic composition for use according to aby one of claims 5 to 18, wherein said immune response is a protective immune response.

20. The method according to any one of claims 1, and 7 to 19, or the immunogenic composition for use according to any one of claims 5 to 19, wherein the immunogenic composition is administered by oral drench to the subject..

21. The method according to any one of claims 1 to 4, and 7 to 20, or the immunogenic composition for use according to any one of claims 5 to 20,-0041-ff Boehringer Ingelheim Vetmedica GmbH wherein the subject is an animal, or wherein the subject is a pig, or wherein the subject is a piglet or a sow.

22. The method according to any one of claims 1 to 4, and 7 to 21, or the immunogenic composition for use according to any one of claims 5 to 21, wherein the immunogenic composition comprises 10 to 800 µg of the non-replicating virus antigen per dose.

23. The method according to any one of claims 1 to 4, and 7 to 22, or the immunogenic composition for use according to any one of claims 5 to 22, wherein the immunogenic composition comprises up to 800 µg of the non-replicating virus antigen per dose.

24. A liquid antigen concentrate for dilution in drinking water or in liquid food, wherein 1 mL of said concentrate comprises about 100 to 800 µg of non-replicating virus antigen, preferably about 300 to 800 µg of non-replicating virus antigen.

25. A method for enabling the self-immunization against a virus by a subject, comprising the step of diluting a liquid antigen concentrate comprising non- replicating virus antigen in the drinking water of the subject.

26. Container containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added.

27. The container according to claim 26, wherein said container is selected from the group consisting of - a bowl containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added, - a vessel containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added, and - a barrel containing drinking water to which a liquid antigen concentrate comprising non-replicating virus antigen has been added;-0041-ff Boehringer Ingelheim Vetmedica GmbH and / or wherein said container is located in the housing environment of a subject to be immunized.

28. Kit for immunization of a subject, comprising - a liquid antigen concentrate comprising non-replicating virus antigen; and - instructions to dilute said liquid antigen concentrate in drinking water or liquid food to be consumed by the subject.

29. The liquid antigen concentrate for dilution in drinking water of claim 24, the method according to claim 25, the container according to claim 26 or 27, or the kit according to claim 28, wherein said non-replicating virus antigen is a non- replicating virus antigen as specified in claim 14 or 15, and / or wherein said non- replicating virus antigen comprises a recombinant protein as specified in claim 16.

30. The method according to claim 25 or 29, the container according to any one of claims 26, 27, and 29, or the kit according to claim 28 or 29, wherein said liquid antigen concentrate comprising non-replicating virus antigen is the liquid antigen concentrate of claim 24 or 29.

31. The method according to any one of claims 25, 29, and 30, the container according to any one of claims 27, 29, and 30, or the kit according to any one of claims 28 to 30, wherein the subject is an animal, or wherein the subject is a pig, or wherein the subject is a piglet or a sow.

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