A strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 and its application

Abstract

The present invention provides a strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 and its application, belonging to the field of microbial technology. The classification name of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 provided by the present invention is Lactobacillus delbrueckii subsp.Bulgaricus , was deposited in the General Microbiology Center of China Microbiological Culture Collection Committee on March 18, 2024, with the deposit number CGMCC No.30046, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. This strain can significantly enhance the body's immune function, has a certain protective effect on immune organ disease damage caused by cyclophosphamide, and significantly improves the low immunity caused by taking anti-tumor drugs.

Description

Technical Field

[0001] The invention relates to the technical field of microorganisms, and in particular to a strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 and an application thereof. Background Art

[0002] Immune function is a protective physiological function formed by humans and animals in the long-term evolution. As the most important protective system of the body, the immune system is distributed throughout the body and involves a variety of molecules, cells, tissues and organs. It is a highly complex defense mechanism that can resist the invasion of foreign substances and thus maintain the stability of the internal environment. Immunosuppression is a temporary or long-term state of immune dysfunction. Due to the damage of the immune system, the body becomes more sensitive to pathogens. Cyclophosphamide (CTX), as an alkylating anticancer agent, is widely used to treat various cancers. It can interfere with DNA replication, damage mitochondrial membranes and lysosomal membranes, thereby damaging normal tissues, leading to immune deficiency and increased risk of secondary infection. However, long-term treatment with CTX may cause various side effects, such as acute cytotoxicity, immunosuppression and gastrointestinal mucosal barrier damage. To improve this situation, some immunoprotective agents are increasingly being used to reduce the adverse side effects of chemotherapy patients. It has been reported that some antiparasitic drugs also have immunomodulatory activity, such as levamisole hydrochloride. Levamisole hydrochloride is a drug widely used to enhance immunity in various human diseases, including leprosy, rheumatoid arthritis, and adjuvant treatment of colorectal cancer. However, chemical drug intervention is usually accompanied by a certain degree of adverse reactions and side effects. Therefore, probiotic products with auxiliary functions in the treatment or prevention of diseases have emerged.

[0003] Lactobacillus delbrueckii is an important type of lactobacillus in lactic acid bacteria. It contains 6 subspecies, among which the Bulgarian subspecies is the most widely used and studied one. Lactobacillus delbrueckii subsp. bulgaricus ) is isolated from Bulgarian milk. As a probiotic lactic acid bacteria, this strain is widely used in the production of yogurt and fermented dairy products. It can produce a variety of flavor compounds during yogurt fermentation and storage. The fermentation characteristics and applications of Lactobacillus delbrueckii subspecies bulgaricus have become a hot topic of research, attracting the attention of a large number of scholars. At present, the research on Lactobacillus delbrueckii in food production mainly includes fermented dairy products, fermented soy products, fermented meat products and fermented fruit and vegetable juices, and the probiotic mechanism is not yet fully clear. There are also few studies on its immune function regulation in the prevention and adjuvant treatment of diseases. Therefore, it is of great significance to separate and screen Lactobacillus delbrueckii with good probiotic properties from traditional fermented foods and further explore its probiotic function and mechanism of action on the human body. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 and its application. The strain provided by the present invention can significantly enhance the body's immune function and has a certain protective effect on immune organ disease damage caused by cyclophosphamide.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504, wherein the classification of the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 is named Lactobacillus delbrueckii subsp. Bulgaricus , deposited in the General Microbiology Center of China Microorganism Culture Collection on March 18, 2024, with the deposit number CGMCC No.30046, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0007] The present invention also provides a use of the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 described in the above technical solution in the preparation of a product for improving immunity.

[0008] The present invention also provides a use of the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 described in the above technical solution in the preparation of a product for improving the reduced immunity caused by taking anti-tumor drugs.

[0009] In the present invention, the products include but are not limited to food, medicine, and health products.

[0010] The present invention also provides an auxiliary therapeutic drug for an anti-tumor drug, wherein the drug contains Lactobacillus delbrueckii subspecies bulgaricus XJFY201504.

[0011] In the present invention, the anti-tumor drug is preferably cyclophosphamide.

[0012] The present invention also provides an adjuvant treatment drug for cyclophosphamide, wherein the drug contains Lactobacillus delbrueckii subspecies bulgaricus XJFY201504.

[0013] Beneficial technical effect: The present invention provides a strain of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 and its application. The classification of the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 is named Lactobacillus delbrueckii subsp. Bulgaricus, deposited in the General Microbiology Center of China Microbiological Culture Collection Committee on March 18, 2024, with the deposit number CGMCC No.30046, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. This strain can significantly enhance the body's immune function, has a certain protective effect on immune organ disease damage caused by cyclophosphamide, and significantly improves the low immunity caused by taking anti-tumor drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The effect of XJFY201504 on the body weight of mice; different lowercase letters indicate significant differences ( P ﹤0.05), the same below;

[0015] Figure 2 The effect of XJFY201504 on the central immune organs of mice; Figure 2 A is the thymus index, Figure 2 B is the spleen index, Figure 2 C is H&E stained section of spleen and thymus;

[0016] Figure 3 The effect of XJFY201504 on serum cytokines and immunoglobulins in mice; Figure 3 A is serum IL-4, Figure 3 B is serum IL-6, Figure 3 C is serum TNF-α, Figure 3 D is serum IgA;

[0017] Figure 4 is the effect of XJFY201504 on mucin-2 and LPS concentrations in mouse colon; Figure 4 A is the colon mucin-2 concentration, Figure 4 B is the colonic LPS concentration;

[0018] Figure 5 The effect of XJFY201504 on the expression level of genes related to the intestinal barrier and inflammatory pathways in mice; Figure 5 A is ZO-1 Relative mRNA expression, Figure 5 B is claudin-1 Relative mRNA expression, Figure 5 C is JAMA Relative mRNA expression, Figure 5 D is MUPP1 Relative mRNA expression, Figure 5 E is IKKα Relative mRNA expression, Figure 5 F is IKKγ Relative mRNA expression. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the content of the present invention is further explained in conjunction with the following examples, but the content of the present invention is not limited to the following examples. The materials, reagents, etc. used in the examples and test examples of the present invention, unless otherwise specified, can be obtained from commercial channels; the methods used in the examples and test examples of the present invention, unless otherwise specified, are conventional methods.

[0020] Example 1 Isolation and Identification of Lactobacillus delbrueckii subspecies bulgaricus XJFY201504

[0021] 1.1 Experimental Materials

[0022] Naturally fermented yogurt was collected from Kurte Township, Xinjiang Uygur Autonomous Region. 40 mL of yogurt was placed in a sterile centrifuge tube, placed in a food sampling box, and stored in a 4°C refrigerator in the laboratory for later use.

[0023] 1.2 Isolation and identification

[0024] Take 1 mL of yogurt sample and dilute it 10 times with sterile saline to 10 -6 , then take 10 -4 , 10 -5 , 10 -6 100 μL of the bacterial solution of 3 gradients was spread on MRS medium and cultured at 37℃ for 24h~48h, and the colony morphology was observed and recorded. The colonies with different morphologies on the plate were picked and separated by streaking on MRS medium. After culturing at 37℃ for 48h, the single colonies with different morphologies on the plate were picked and separated by streaking on MRS medium plate again. This was repeated 2 to 3 times until pure single colonies with consistent morphology were obtained.

[0025] The purified suspected target strain (numbered XJFY201504) was inoculated into MRS broth and cultured at 37°C for 18h~24h. DNA was extracted using a bacterial genomic DNA extraction kit (item number: K0512, purchased from Thermo Fisher Scientific, USA). The extracted DNA was numbered and stored in a -20°C freezer for later use.

[0026] The extracted DNA was subjected to PCR amplification. The amplification system was: 1 μL of upstream primer 27F (5'-AGA GTT TGA TCCTGGCTC AG-3', SEQ ID NO.1), 1 μL of downstream primer 1495R (5'-CTA CGG CTA CCTTGT TAC GA-3', SEQ ID NO.2), 12.5 μL of 2×Taq plus Buffer, 1 μL of template DNA, and the system was supplemented to 25 μL with sterile dd H2O. Sterile ultrapure water was used to replace template DNA as a negative control. The amplification conditions were: 94°C for 5 min; 94°C for 30 s, 55°C for 30 s, 72°C for 1 min, 29 cycles, and 72°C for 5 min.

[0027] Take 5 μL of amplified product for agarose gel electrophoresis detection, the agarose concentration is 1.5%, the electrophoresis conditions are 110V, 45min. The successfully detected PCR product was sent to Beijing Qingke Biotechnology Co., Ltd. for sequencing, and the sequenced sequence was compared and analyzed using the BLAST (Basic Local Alignment Search Tool) program in NCBI.

[0028] According to the 16S rDNA species analysis, the strain is Lactobacillus delbrueckii subspecies bulgaricus. The strain was deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration on March 18, 2024, with a deposit number of CGMCC No. 30046, and the deposit address is the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing. The nucleotide sequence of the 16S rDNA of the strain is shown in SEQ ID NO. 3.

[0029] SEQ ID NO.3:

[0030]

[0031] Example 2

[0032] 2.1 Materials, instruments and equipment

[0033] As shown in Table 1 and Table 2.

[0034] Table 1 Materials and reagents

[0035] name Manufacturer Cyclophosphamide Shanghai MacLean Biochemical Technology Co., Ltd. Levamisole hydrochloride Shanghai MacLean Biochemical Technology Co., Ltd. Mucin-2 ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. LPS ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. DAO ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. IL-4 ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. IL-6 ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. TNF-α ELISA Kit Shanghai ELISA Biotechnology Co., Ltd. IgA UNCOATED ELISA Thermo Fisher Scientific Inc. Isopropyl alcohol Chongqing Chuandong Chemical (Group) Co., Ltd. Chloroform Chengdu Kelong Chemicals Co., Ltd. TRIzol Reagent Yisheng Biotechnology (Shanghai) Co., Ltd. 5 × gDNA digester Mix Yisheng Biotechnology (Shanghai) Co., Ltd. 4 ×Hifair, ⅢSuperMix plus Yisheng Biotechnology (Shanghai) Co., Ltd. RNase-free HO Yisheng Biotechnology (Shanghai) Co., Ltd.

[0036] Table 2 Instruments and equipment

[0037] name Model / Article No. factory UPG series ultrapure water purifier UPH-Ⅱ-20T Sichuan Youpu Ultrapure Technology Co., Ltd. Fully automatic ELISA analyzer AMR-100 Hangzhou Aosheng Instrument Co., Ltd. Micro-volume spectrophotometer Nano-300 Hangzhou Aosheng Instrument Co., Ltd. Desktop high speed refrigerated centrifuge iCEN-24R Hangzhou Aosheng Instrument Co., Ltd. Gene Amplifier A200 Hangzhou Langji Scientific Instrument Co., Ltd. Real-time fluorescence quantitative PCR instrument SteponePlus Thermo Fisher Scientific (Suzhou) Instrument Co., Ltd. Biological sample homogenizer Bioprep-24 Hangzhou Aosheng Instrument Co., Ltd.

[0038] 2.2 Experimental methods

[0039] 2.2.1 Animal Experiment Design

[0040] Fifty 5-week-old (24±2g) SPF male Kunming mice were purchased from Hunan Slake Jingda Experimental Animal Co., Ltd. (Animal Qualification License No.: SCXK (Xiang) 2019–0004) and housed in a constant temperature and humidity environment with a temperature of 25±2℃ and a humidity of 50±5%. The mice were fed with food and water freely, with light and dark alternation every 12h. After 7 days of adaptive feeding, they were randomly divided into 5 groups, namely: normal group, model group, positive control group, low-concentration XJFY201504 group, and high-concentration XJFY201504 group. The normal group, model group, and positive control group were gavaged with 0.2 mL of sterile saline every day, and the low-concentration XJFY201504 and high-concentration XJFY201504 groups were gavaged with 0.2 mL of low-concentration and high-concentration bacterial suspension (2×10 7 CFU / kg, 2×10 9 CFU / kg). On the 15th, 16th and 17th days of the experiment, except for the normal group, the other four groups were intraperitoneally injected with 80 mg / kg of cyclophosphamide, and the positive control group was gavaged with 0.2 mL of 40 mg / kg levamisole hydrochloride from the 18th to the 21st day. The experimental period was 21 days, and the weight changes of the mice were observed and recorded every other day. On the 22nd day of the experiment, all mice were euthanized and samples were collected.

[0041] 2.2.2 Determination of mouse immune organ index

[0042] The spleen and thymus of the mouse were removed, the tissues around the organs were removed, and the organs were washed with physiological saline and then dried with filter paper. The spleen and thymus were weighed respectively, and the immune organ index was calculated according to the following formula.

[0043]

[0044] 2.2.3 Histopathological observation of mouse spleen and thymus

[0045] Mouse spleen and thymus were fixed in paraformaldehyde tissue fixative. After the tissue samples were fixed and dehydrated, they were embedded in paraffin. The paraffin-embedded blocks were cut into 0.3 μm slices by a microtome, and then routinely dewaxed, hydrated with gradient ethanol, stained with hematoxylin for 2 min, differentiated with 1% hydrochloric acid ethanol for 3s to 5s, blueed with dilute ammonia for 1s to 2s, stained with eosin for 15s, dehydrated, transparent, and sealed with neutral gum. The pathological changes of the spleen and thymus were observed under an upright microscope.

[0046] 2.2.4 Determination of cytokine concentrations in mouse serum and ileum

[0047] The whole blood of mice was collected and allowed to stand at room temperature for 30 minutes, centrifuged at 4°C and 4000 r / min for 15 minutes, and the upper serum was aspirated and stored at −80°C after appropriate aliquoting. Serum and ileum tissue samples were prepared according to the instructions of the enzyme-linked immunosorbent assay (ELISA) kit to measure the concentrations of mouse serum IL-4, IL-6, TNF-α, and IgA, as well as the concentrations of ileum lipopolysaccharides (LPS), mucin-2, and diamine oxidase (DAO).

[0048] 2.2.5 Determination of intestinal barrier-related factor mRNA in mouse ileum

[0049] Weigh an appropriate amount of mouse ileum tissue, add TRIzol for homogenization to extract RNA from the mouse ileum tissue, and then use a spectrophotometer to measure the concentration and purity of the RNA extract, and reverse transcribe the RNA extract into cDNA according to the instructions of the reverse transcription kit. After reverse transcription, prepare the cDNA reaction system in an eight-tube strip, namely 10 μL of Master mix, 1 μL of upstream and downstream primers, 1 μL of template cDNA, and 7 μL of sterile enzyme-free water. After the reaction system is prepared, place it on the StepOnePlus real-time fluorescence quantitative PCR instrument for amplification detection. Amplification conditions: 95°C pre-denaturation for 5 minutes, 95°C denaturation for 10 seconds, 60°C annealing for 30 seconds, and 40 cycles. After the detection, use the internal reference gene Eef2 as the benchmark and use the formula Calculate the relative expression of target gene mRNA. The primer sequences used in this experiment are shown in Table 3.

[0050] Table 3 Primer sequences

[0051]

[0052] 2.2.6 Data processing and statistical analysis

[0053] All data were expressed as mean ± standard deviation (SD) and analyzed using IBM SPSS 23.0 statistical software. One-way analysis of variance (ANOVA) and Duncan's multiple range test were used for comparison between groups. The same lowercase letters in ae indicate no significant difference between the two groups, and different lowercase letters indicate significant difference between the two groups P <0.05.

[0054] 2.3 Results and Analysis

[0055] 2.3.1 Effect on body weight of immunosuppressed mice

[0056] In order to evaluate the growth status of mice throughout the experimental period, the body weight of mice was measured and recorded every two days. Figure 1 As shown in the figure, the weight of mice in each group was similar at the beginning of modeling. During the whole experimental period, the weight of mice in the normal group showed no abnormal fluctuation and gradually increased. Before the injection of immunosuppressant CTX, the weight growth trend of the other four groups was the same as that of the normal group. After the injection of CTX on the 15th day, the weight of mice in the four groups showed a significant downward trend. Compared with the model group, the weight loss trend of mice in the positive control group, the low-concentration XJFY201504 group and the high-concentration XJFY201504 group was improved, and showed significant differences on the 21st day ( P <0.05). Among them, the high-concentration group of XJFY201504 had a significantly better effect on improving the weight loss trend of mice than the low-concentration group, and had a similar effect to the positive control group treated with levamisole hydrochloride.

[0057] The intervention of XJFY201504 can significantly improve the weight loss caused by CTX, indicating that Lactobacillus delbrueckii bulgaricus XJFY201504 has the potential to resist the damage of CTX to the basic signs of mice and maintain and restore the weight indicators of mice.

[0058] 2.3.2 Effects on thymus index, spleen index and immune organ histopathology in immunosuppressed mice

[0059] The thymus and spleen are important central immune organs in humans and animals, and their development and status directly determine the response capacity of the immune system. Figure 2 As shown in A and B, compared with the normal group, the thymus and spleen indexes of the CTX-treated group were reduced. Compared with the model group, the thymus index and spleen index of the immunosuppressed mice were significantly increased after treatment with levamisole hydrochloride and XJFY201504 ( P <0.05, but still lower than the normal group. Among them, the spleen index of the high-concentration group of XJFY201504 had no significant difference with that of the positive control group ( P>0.05). This indicates that both high and low concentrations of XJFY201504 have a significant improvement effect on the decline of immune organ index caused by the immunosuppressant CTX, and the effect of high concentration is significantly higher than that of low concentration.

[0060] H&E stained histopathological sections of spleen and thymus Figure 2 As shown in Figure C, the morphological structure of spleen tissue in the normal group was normal, no tissue necrosis was observed, the central splenic artery was clearly visible, there was a clear boundary between the red pulp and the white pulp, and the white pulp was more in number and stained darker, indicating a large number of lymph nodes. In the model group treated with CTX, the spleen tissue had severe lesions, the central splenic artery disappeared, the white pulp and red pulp had disordered structures, blurred boundaries, unclear edges, light staining, and a decrease in the number of lymphocytes. Compared with the model group, the pathological damage of the spleen tissue structure of mice in the positive control group, the low-concentration group of XJFY201504, and the high-concentration group was alleviated to varying degrees, the white pulp and red pulp structure was relatively complete, the boundaries were relatively clear, the white pulp staining color was deepened, and the central splenic artery of different degrees of clarity and scattered splenic trabeculae were visible. Among them, the pathological damage of spleen in the positive control group and the high-concentration group of XJFY201504 was significantly improved, indicating that levamisole hydrochloride and XJFY201504 can effectively reduce the pathological damage of spleen caused by CTX, and the improvement effect of high-concentration XJFY201504 is better than that of low-concentration. The thymus is the place where T cells differentiate and develop, and has important immunoregulatory functions. In the thymus tissue of the normal group of mice, clear cortical and medullary regions can be seen, the cells in the cortex are dense and stained darker, the cells in the medulla are relatively few and stained lighter, and the thymus structure is tightly arranged, and no tissue pathological damage is observed. However, in the model group treated with CTX, severe pathological damage can be seen in the thymus tissue, the overall structure of the cortex and medulla is chaotic, there is no obvious boundary, the cortical area is significantly reduced and thinned, the medulla area is significantly enlarged, and the staining of the medulla area is significantly lighter, the cells are sparsely arranged, and the number is significantly reduced, indicating that the immunosuppressant CTX can destroy the thymus tissue structure, resulting in a decrease in immune cells. Compared with the model group, the thymic tissue damage in the positive control group treated with levamisole hydrochloride was significantly improved, with a clear boundary between the cortex and medulla, a significant increase in the area of ​​the cortex, a darker staining, and a significant increase in cell density; although the pathological damage of the thymic tissue in the low-concentration XJFY201504 group was alleviated, the boundary between the cortex and medulla was not clear enough, the cell density in the cortex was not high, and the staining was not deep; the thymic tissue lesions in the high-concentration XJFY201504 group were greatly improved, with a clear boundary between the cortex and medulla. The staining of the cortex area was deepened, indicating an increase in cell density, which was similar to that of the positive control group. It can be seen that both levamisole hydrochloride and XJFY201504 can reduce the pathological damage of the thymus in immunosuppressed mice, and the high-concentration XJFY201504 has a better improvement effect on thymic lesions than the low-concentration XJFY201504.

[0061] 2.3.3 Effects on serum cytokine and immunoglobulin concentrations in immunosuppressed mice

[0062] The immunosuppressant CTX can damage immune cells, leading to decreased secretion of serum cytokines and immunoglobulins. Figure 3 As shown in the figure, compared with the normal group, the concentrations of cytokines IL-4, IL-6, TNF-α and immunoglobulin IgA in the serum of mice treated with CTX were significantly reduced ( P <0.05). Compared with the model group, the cytokine and immunoglobulin concentrations in the positive control group, the low-concentration XJFY201504 group, and the high-concentration XJFY201504 group were significantly increased ( P <0.05). The specific results showed that the concentration of the positive control group treated with levamisole hydrochloride was higher than that of the XJFY201504 treatment group. Among them, the high-concentration XJFY201504 group significantly improved the serum cytokine and immunoglobulin concentrations better than the low-concentration XJFY201504 group. It is worth mentioning that the high-concentration XJFY201504 gavage treatment increased the serum concentration of IL-4, which is mainly secreted by activated T cells and mast cells, to a level similar to that of the positive control ( P >0.05).

[0063] 2.3.4 Effect of XJFY201504 on colonic mucin-2 and LPS concentrations in immunosuppressed mice

[0064] The immunosuppressant CTX can increase intestinal barrier permeability and lead to intestinal mucosal damage. Figure 4 As shown in Figure 2, compared with the normal group, the Mucin-2 content in the colon of mice treated with CTX was significantly decreased, while the LPS content was significantly increased ( P <0.05), after treatment with levamisole hydrochloride and XJFY201504, the mucin-2 content in the colon of mice increased significantly, and the LPS content decreased significantly ( P <0.05), among which the high concentration group of XJFY201504 had better effect than the low concentration group. This showed that XJFY201504 had the potential to improve the intestinal mucosal damage caused by CTX.

[0065] 2.3.5 Effect on relative mRNA expression of ileal intestinal barrier-related genes in immunosuppressed mice

[0066] like Figure 5 As shown in the figure, compared with the normal group, the intestinal barrier-related ZO-1, claudin- 1. JAMA and MUPP1 The relative expression level of mRNA was significantly decreased ( P<0.05), indicating that the injection of CTX destroyed the integrity of the intestinal barrier. The intervention of levamisole hydrochloride and XJFY201504 could significantly improve the low expression of intestinal barrier-related genes caused by CTX ( P <0.05). Among them, the effect of high concentration of XJFY201504 was significantly better than that of low concentration. In addition, the intervention of XJFY201504 can also significantly upregulate the κB kinase inhibitor IKKα and IKKβ The expression levels of XJFY201504 were significantly higher than those of XJFY201504 at high concentrations, and the effect of high concentrations was significantly better than that of low concentrations. This indicates that XJFY201504 can play a potential role in maintaining intestinal barrier integrity and reducing intestinal inflammatory response by upregulating the expression levels of tight junction family-related genes and restoring the expression of κB kinase inhibitors.

[0067] 2.4 Conclusion

[0068] In this study, an immunosuppressive mouse model was induced by cyclophosphamide at a dose of 80 mg / kg, and the effect and mechanism of Lactobacillus delbrueckii XJFY201504 on protecting the intestinal barrier and enhancing the immune function in the immunosuppressive mouse model were preliminarily studied. The results showed that the concentration of 1.0×10 7 CFU / kg and 1.0×10 9 CFU / kg of XJFY201504 intragastrically intervened and significantly improved the weight loss trend of immunosuppressed mice, restored the thymus index of the central immune organ and the spleen index of the peripheral immune organ, and had a certain protective effect on the pathological damage of immune organs caused by CTX; at the same time, it promoted the secretion of serum cytokines IL-4, IL-6 and TNF-α, as well as immunoglobulin IgA, reduced the LPS concentration in colon tissue, increased the mucin-2 concentration; and effectively upregulated the intestinal barrier-related factors ( ZO-1, claudin-1, JAMA, MUPP1, IKKα and IKKβ ) mRNA expression level, and high concentration (1.0×10 9 CFU / kg) of XJFY201504 showed a more significant effect. In summary, Lactobacillus delbrueckii bulgaricus XJFY201504 can directly improve the immune function of immunosuppressed mice by protecting and maintaining the normal physiological structure of central immune organs and promoting the secretion of serum cytokines and immunoglobulins; it can also indirectly improve the immune function of mice by reducing the concentration of intestinal endotoxin LPS and increasing the concentration of mucin-2 in the mucus layer, as well as promoting the integrity of the intestinal barrier.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A strain of Lactobacillus delbrueckii subsp. bulgaricus ( Lactobacillus delbrueckii subsp. Bulgaricus )XJFY201504, characterized in that, The Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 was deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration on March 18, 2024, with a deposit number of CGMCC No. 30046, and the deposit address is the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

2. Use of the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 according to claim 1 in the preparation of food or health products for improving the reduced immunity caused by taking cyclophosphamide.

3. A cyclophosphamide adjuvant therapy drug, characterized in that: The medicine comprises the Lactobacillus delbrueckii subspecies bulgaricus XJFY201504 described in claim 1.

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