ABSTRACT
Tuberculosis (TB) causes more than 1.5 million deaths each year, remaining a significant global health problem. Mycobacterium smegmatis (M. smegmatis) and Mycobacterium tuberculosis (M. tuberculosis) share features, which support the use of the former use in new generation TB vaccine development. In a previous study, the specific humoral and cellular immunogenicity of a recombinant M. smegmatis strain expressing epitopes from M. tuberculosis Ag85B protein (rMs064), was demonstrated in mice. In the current study, the immunomodulatory capacity of rMs064 was determined in a J774A.1 murine macrophage cell line. To determine the immunomodulatory effect of rMs064 in J774A.1 macrophages, the expression of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) was evaluated. The expression of activation surface markers (MHC-II, CD40, CD80 and CD86) and the production of cytokines (IL-1ß, TNF-α, IL-12p70 and IL-6) was also determined in rMs064 infected J774A.1 macrophages. Our findings showed the ability of rMs064 to induce substantial increases in macrophage activation markers expression; MHC class II and CD40, compared with M. smegmatis transformed with the empty vector (rMs012) and uninfected cells. rMs064 induced significant increases in IL-12p70 compared to uninfected cells. The expression of iNOS and CD86, and the production of IL-1ß, and TNF-α were increased in rMs064 and rMs012, compared to uninfected cells. rMs064 demonstrated its immunomodulatory ability by stimulating the innate immune response, which supports its further evaluation as a TB vaccine candidate.
ABSTRACT
OBJECTIVE/BACKGROUND: The search for new vaccines more efficacious than bacille Calmette-Guérin for tuberculosis prevention is of paramount importance for the control of the disease. The expression of Mycobacterium tuberculosis antigens in Mycobacterium smegmatis is one of the current strategies for the development of new-generation vaccines against tuberculosis. The objective of this study was to evaluate the immunogenicity in mice of M. smegmatis expressing epitopes from Ag85B antigen. METHODS: M. smegmatis expressing three T cell epitopes from M. tuberculosis Ag85B (P21, P26, and P53) was constructed (rMs064). rMs064 was used to immunize BALB/C mice for immunogenicity evaluation. The present study investigates the capacity of rMs064 to induce specific cellular and humoral immune responses against the expressed epitopes. Cytokine production upon stimulation with Ag85B peptides and specific total immunoglobulin G and immunoglobulin G subclasses were determined. RESULTS: The results showed a significant production of interleukin-12 and interleukin-23 when splenocytes were stimulated with P21, P26, and P53 peptides, and interferon-γ after stimulation with P21 in animals immunized with rMs064 compared with controls. The total immunoglobulin G and its subclasses showed significant increases against the Ag85B epitopes in the sera of rMs064-immunized mice compared with the control groups. CONCLUSION: The results of this study support the future evaluation of rMs064 as a vaccine candidate against tuberculosis in challenge experiments.
