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

BCG is widely used as a vaccine against tuberculosis due to (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 induced a robust MHC-II-dependent antigen presentation to CD4 T cells in vitro, and elicited stronger T1 cytokines (IL-12, IL-1β, and TNFα) from APCs of C57Bl/6 mice increasing phosphorylation of p38MAPK and ERK. BCG also enhanced MHC-II surface expression of MΦs by inhibiting MARCH1 ubiquitin ligase that degrades MHC-II. BCG infected APCs from MyD88 or TLR-2 knockout mice showed decreased antigen presentation. Furthermore, BCG induced LC3-dependent autophagy in macrophages increasing antigen presentation. Consistent with in vitro effects, BCG 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 induces stronger and longer lasting immunity, and is better than BCG against tuberculosis of mice.