Immunogenicity and Therapeutic Effects of Latency-Associated Genes in a Mycobacterium Tuberculosis Reactivation Mouse Model

In this study, the Mycobacterium tuberculosis (MTB) latency-associated antigens Rv2660c, Rv1733c, Rv1813c, Rv2628, Rv2029c, and Rv2659c were compared regarding their immunogenicity and potential therapeutic effects in an MTB reactivation mouse model. Normal mice or MTB reactivation mice were immunized intramuscularly three times at 2-week intervals with saline, plasmid vector pVAX1, Mycobacterium vaccae vaccine (a commercial inactivated vaccine), rv1813c DNA, rv2628 DNA, rv2029c DNA, rv2659c DNA, rv1733c DNA, or rv2660c DNA. The normal mice immunized with rv2628 DNA or rv2659c DNA had low numbers of Th1 cells and a lower ratio of Th1:Th2 immune cells in whole blood (p < 0.05). Compared to the saline group, Tc1 cells in the rv2029c DNA group and Tc1:Tc2 cell ratio in the rv1813c DNA, rv2628 DNA, and rv2029c DNA groups were significantly decreased (p < 0.05). The proportion of Foxp3+CD4+ T cells in the rv2628 DNA and rv2659c DNA groups and the proportion of CD4+CD25+ T cells in the rv2029c DNA group were significantly increased (p < 0.05). The level of anti-Rv1813c-immunoglobulin G (IgG) in the rv1813c DNA group was significantly increased (p < 0.01). The levels of specific IgG, IgG1, and IgG2a in the rv2628 DNA, rv2029c DNA, and rv2659c DNA groups were significantly increased (p < 0.05). Lung colony-forming units in M. vaccae and the six DNA groups decreased to different degrees in the MTB reactivation mouse model, but only the lung colony-forming units in the rv2628 DNA group (4.38 ± 0.70 log10) significantly decreased compared to the vector group (5.90 ± 0.42 log10; p < 0.05). The MTB rv1813c DNA, rv2628 DNA, rv2029c DNA, and rv2659c DNA could elicit a strong humoral immune response and a higher proportion of CD4+CD25+or CD4+Foxp3+ T cells but could not increase the proportions of Th1 and Tc1 cells. These results suggest that latency-associated DNA vaccines, especially rv2628 DNA, had some therapeutic effect on the endogenous resurgence mouse tuberculosis model.