An autophagy-inducing and TLR-2 activating BCG vaccine induces a robust protection against tuberculosis in mice

Mycobacterium bovis BCG is widely used as a vaccine against tuberculosis due to M. tuberculosis (Mtb), which kills millions of people each year. BCG variably protects children, but not adults against tuberculosis. BCG evades phagosome maturation, autophagy, and reduces MHC-II expression of antigen-presenting cells (APCs) affecting T-cell activation. To bypass these defects, an autophagy-inducing, TLR-2 activating C5 peptide from Mtb-derived CFP-10 protein was overexpressed in BCG in combination with Ag85B. Recombinant BCG(85C5) induced a robust MHC-II-dependent antigen presentation to CD4 T cells in vitro, and elicited stronger T(H)1 cytokines (IL-12, IL-1β, and TNFα) from APCs of C57Bl/6 mice increasing phosphorylation of p38MAPK and ERK. BCG(85C5) also enhanced MHC-II surface expression of MΦs by inhibiting MARCH1 ubiquitin ligase that degrades MHC-II. BCG(85C5) infected APCs from MyD88 or TLR-2 knockout mice showed decreased antigen presentation. Furthermore, BCG(85C5) induced LC3-dependent autophagy in macrophages increasing antigen presentation. Consistent with in vitro effects, BCG(85C5) markedly expanded both effector and central memory T cells in C57Bl/6 mice protecting them against both primary aerosol infection with Mtb and reinfection, but was less effective among TLR-2 knockout mice. Thus, BCG(85C5) induces stronger and longer lasting immunity, and is better than BCG against tuberculosis of mice.