Immunogenicity and protective efficacy of "Mycobacterium w" against Mycobacterium tuberculosis in mice immunized with live versus heat-killed M. w by the aerosol or parenteral route

Abstract

As the disease caused by Mycobacterium tuberculosis continues to be a burden, there is a concerted effort to find new vaccines to combat this problem. One of the important vaccine strategy is whole bacterial vaccines. This approach rely on multiple antigens and built-in-adjuvanticity. Other mycobacterial strains which share cross-reactive antigens with M.tuberculosis have been considered as alternatives to M.bovis for vaccine use. One such strain, M.w had been evaluated for its immunomodulatory properties in leprosy. A vaccine against leprosy based on killed M.w is approved for human use, where it has resulted in clinical improvement, accelerated bacterial clearance and increased immune responses to M.leprae antigens. M.w shares antigens not only with M.leprae but also with M.tuberculosis and initial studies have shown that vaccination with killed M.w induces protection against tuberculosis in BCG responder as well as BCG non-responder strains of mice. Hence, we further studied the protective potential of M.w and the underlying immune responses in mice model of tuberculosis. We analysed the protective efficacy of M.w immunization, both in live or killed form, through parenteral route as well as by aerosol immunization and compared with BCG. Our findings provide evidence that M.w has potential protective efficacy against M.tuberculosis. M.w activates macrophage activity as well as lymphocytes. M.w immunisation both by parenteral route as well as by aerosol immunisation gives higher protection than BCG given by the parenteral route in mouse model of tuberculosis.