Acta Veterinaria et Zootechnica Sinica ›› 2020, Vol. 51 ›› Issue (9): 2238-2249.doi: 10.11843/j.issn.0366-6964.2020.09.021

• PREVENTIVE VETERINARY MEDICINE • Previous Articles     Next Articles

Analysis of Immune Response Induced by Recombinant Lactobacillus reuteri Expressing Cap Protein of Porcine Circovirus Type 2 in Mice

WANG Shubo1, XU Yigang1,2, CHEN Qiuyan1, MEI Zhuyuan1, CUI Wen1,2, JIANG Yanping1,2, ZHOU Han1,2, WANG Li1,2, QIAO Xinyuan1,2, LI Yijing1,2, TANG Lijie1,2*   

  1. 1. College of Veterinary Medicines, Northeast Agricultural University, Harbin 150030, China;
    2. Northeast Scientific Inspection Observation Station, Key Laboratory of Animal Pathogen Biology of Ministry of Agriculture, Harbin 150030, China
  • Received:2020-03-06 Online:2020-09-25 Published:2020-09-25

Abstract: The purpose of this study was to construct a recombinant Lactobacillus reuteri (L. reuteri) expressing the cap protein of porcine circovirus type 2 (PCV2) and evaluate its effect on immune response in mice. The cap protein gene of PCV2b strain isolated and stored in the laboratory was amplified by PCR. A recombinant strain pPG-T7 g10-PPT-cap / L. reuteri expressing the cap protein was constructed using L. reuteri of pig origin as the host strain and explored the immune effect of BALB/c mice with recombinant bacteria orogastrically. Indirect ELISA was used to determine the level of antigen-specific IgG antibodies in the serum of mice after immunization, the levels of antigen-specific sIgA antibodies in stool, nasal wash, reproductive tract wash, and intestinal mucus, and the levels of various cytokines in mouse serum; MTT method was used to detect mouse spleen lymphocyte proliferation levels; flow cytometry (FCM) was used to detect the levels of CD4+ T cells and CD8+ T cells in mouse spleen lymphocytes; fluorescence quantitative PCR was used to detect the viral load of organs in challenged mice after immunization. The results showed that the serum levels of IgG antibodies in the mice of the oral immune recombinant strain group (OIG) were significantly higher than those in the control group (P<0.01); the levels of sIgA antibodies in the stool, nasal wash, reproductive tract wash, and intestinal mucus of the mice in OIG were significantly higher than those in the control group (P<0.01); Compared with the control group, the levels of cytokines in the serum of OIG were as follows: The levels of IFN-γ, IL-2, IL-4, IL-12 increased, the levels of IL-10 decreased, and the levels of IFN-α did not change significantly; Incubation of PCV2 and mouse spleen lymphocytes in vitro showed that the proliferation stimulating index of spleen lymphocytes in OIG was significantly higher than that of the control group (P<0.01); FCM results showed that CD4+ T cells and CD8+ T cells were higher than those of the control group; the results of fluorescent quantitative PCR showed that compared with the control group, the viral load in the OIG was significantly lower than that of the control group. In summary, the recombinant L. reuteri expressing the PCV2 cap protein were successfully constructed, and the constructed recombinant L. reuteri can stimulate mice to produce humoral and cellular immune responses after oragastrical immunization, and can exert a certain immune protection effect.

Key words: porcine circovirus, cap protein, recombinant Lactobacillus reuteri, immune response

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