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

Abstract

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.

Vaccine adjuvant activity of a TLR4-activating synthetic glycolipid by promoting autophagy

“…The gating strategies are presented in Supplementary Fig. 5A-D. in mice 22,23 . Therefore, small molecules selectively triggering TLRs-mediated autophagy presumably increase immunogenicity and can potentially be developed as mycobacterial vaccines and adjuvants.…”

“…Furthermore, TLR signal-stimulating particles can trigger LAP as a host defense mechanism 27 . Stimulation of TLR2 and TLR4 can enhance autophagy in APCs and promote immunogenicity of BCG vaccines against tuberculosis 22,23 . Overall, therapeutic intervention that modulates autophagy through TLR4 may serve as an effective strategy for vaccine or adjuvant development.…”

Mycobacterium smegmatis Bacteria Expressing Mycobacterium tuberculosis-Specific Rv1954A Induce Macrophage Activation and Modulate the Immune Response

“…In order to eradicate TB by 2035, as envisaged under the Sustainable Development Goals of UNO and the WHO End TB Strategy, major focus of research includes areas such as discovering new drugs, repurposing drugs, discovering new vaccines, and administering vaccines through different routes to enhance its efficacy (Khan et al, 2019 ; Kumar et al, 2019 ; Darrah et al, 2020 ; Sheikh et al, 2020 ). Our earlier intensive comparative computational analysis revealed proteins that are specific to M. tb pathogen and absent in all other mycobacterial species (Rahman et al, 2014 ).…”

Preclinical Progress of Subunit and Live Attenuated Mycobacterium tuberculosis Vaccines: A Review following the First in Human Efficacy Trial

“…There are two main methods that research groups have used to increase BCG immunogenicity: improve antigen presentation via abolishing its ability to hide in the macrophage phagosome or increase the expression of immunogenic proteins. To overcome the limitations with improper phagosome maturation and MHC class II (MHC-II) expression evasion of BCG, a group from Texas generated an autophagy-inducing and toll-like receptor 2 (TLR-2) activating rBCG vaccine by overexpressing Ag85B and the C5 peptide from CFP-10 (BCG 85C5 ) [34]. Mice subcutaneously vaccinated with BCG 85C5 had reduced bacterial loads compared to BCG 30 days after initial challenge (lung p = 0.01; spleen p = 0.01) and 30 days after re-challenge (lung p < 0.05; spleen not significant [n.s.])…”