Recombinant Rv0222 protein from Mycobacterium tuberculosis regulates host Th9 differentiation function in vitro

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (Mtb), which is increasing year by year and brings great harm to human beings. Genomic analysis showed that compared with Mtb, some regions of differences (RD) were missing in the BCG genome, and Rv0222 was located in the RD4 region of Mtb. In our study, the recombinant Rv0222(rRv0222) protein was successfully constructed with pET32a as the expression vector. After stimulating mouse spleen cells with different concentrations of rRv0222, the cell proliferation rate was detected by CCK8 method. We found that the cell proliferation activity decreased with the increase of the concentration of rRv0222. The concentration of Th9-related cytokines was determined by ELISA, and it was found that the levels of IL-4, IL-9, IL-10 and TGF-β1 were increased. The expression of IL-9 and TGF-β1 mRNA was detected by RT-qPCR method, and it was found that the mRNA expression was increased. The proportion of Th9-related T cells was detected by flow cytometry. The results showed that the proportion of CD3⁺CD4⁺T cells in spleen lymphocytes decreased, and the proportion of CD4⁺IL-4⁺T and CD4⁺IL-9⁺T cells increased. Our study showed that the rRv0222 can up-regulate Th9 cell-related factors, inhibit cell proliferation, and regulate host immune cells, which provides a theoretical basis for elucidating the regulation of host immune response by Mtb, it may serve as both a vaccine candidate and a potential therapeutic target for TB.