Heterologous Prime Boost Regimes with N-terminal Peptides of Ag85B Induces Better Protection than Ag85B and BCG in Murine Model of Tuberculosis

Abstract

Limited experimental evidences are available on the use of peptides as vaccines to boost BCG induced immunity for protection against tuberculosis. The present study therefore evaluated protective efficacy of booster dose of N-terminal peptides of Ag85B, using prime boost approaches in murine model of tuberculosis. Using earlier established subcutaneous murine model of TB in our laboratory, we compared the protective vaccination efficacy of peptides of Ag85B with that of booster dose of whole Ag85B and BCG by evaluating both antibody and cell-mediated immune response. Groups of mice primed by BCG and boosted with Ag85B peptides showed limited pulmonary bacillary burden and reduced lung pathology after challenge with virulent dose of Mycobacterium tuberculosis in mice. Significant levels (p < 0.001) of BCG specific antibodies (anti-BCG, anti-PPD) and T cell-specific cytokines were observed in Ag85B peptides boosted mice compared to Ag85B and BCG. Ag85B and BCG boosted mice however showed significant protection compared to single BCG dose and unvaccinated control groups. Our result suggests that prime boost strategy using N-terminal peptides of Ag85B may improve immunogenicity of BCG against TB. Such peptides may be attractive candidates for boosting waning BCG induced immune response in near future. However study demands further work including improvisation in experimental designs to justify the results.