Toll-like receptor-mediated innate immune responses by recognition of the recombinant dormancy-associated Mycobacterium tuberculosis proteins Rv2659c and Rv1738

Abstract

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) poses a major threat to the global public health. Importantly, latent tuberculosis infection (LTBI) still impedes the elimination of TB incidence since it has a substantial risk to develop active disease. A multi-stage subunit vaccine comprising active and latency antigens of Mtb has been raised as the promising vaccine to trigger immune protection against all stages of TB. Therefore, the discovery of new antigens that could trigger broad immune response is essential. While current development of TB vaccine mainly focuses on protective immunity mediated by adaptive immune response, the knowledge on triggering the innate immune response by antigens is still limited. We showed that recombinant dormancy-associated Mtb proteins Rv2659c and Rv1738 were recognized by human innate immune recognition molecules, Toll-like receptors (TLRs) 2 and 4 by using HEK-Blue™ hTLR2/hTLR4 systems. We further demonstrated that these two proteins activated phosphorylated NF-κB p65 (Ser536) in the human CD14+ blood cells. We also investigated that these two proteins significantly induced level of pro- and anti-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10 and TNF-α) which were mediated through TLR2 and TLR4 pathways in human peripheral blood mononuclear cells (hPBMCs). These findings suggest that proteins Rv2659c and Rv1738 stimulated innate immune response targeting TLR2 and TLR4 to produce inflammatory cytokines, and their benefits would be valuable for the development of an effective prophylactic tuberculosis vaccine.

Peptide microarray-based identification of dormancy-associated Mycobacterium tuberculosis antigens inducing immune responses among latent tuberculosis infection individuals in Thailand

“…To validate the result from the screening phase, we selected Rv2659c and Rv1738 for evaluation of immunoreactivity in a larger study group. Selection of the dormancy-associated antigens was based on the first rank in the antibody-profile screening (Rv2659c), and their ability to trigger innate immune response (Rv2659c and Rv1738) 20 . ESAT-6, the active phase antigen, was also included in the study.…”

“…To validate these findings, the immunological characteristics of recombinant proteins Rv2659c and Rv1738 were further evaluated in a larger study group. Proteins were selected based on their being first rank in the antibody-profile screening (Rv2659c) and their ability to trigger innate immune responses (Rv2659c and Rv1738) 20 . The presence of circulating IgG against selected dormancy antigens was determined in both LTBI and ATB subjects by indirect ELISA, eliciting the consistent results to the peptide array data.…”

Bioinformatics analysis and immunogenicity assessment of the novel multi-stage DNA vaccine W541 against Mycobacterium tuberculosis

“…TLR4 forms homodimers to recognize pathogen-associated molecular patterns such as lipopolysaccharides (LPS), lipoteichoic acid (LTA), dsRNA, etc. After TLR4 activation, it can initiate innate immune responses and regulate the migration, maturation, and function of antigen-presenting cells while facilitating adaptive immune responses (75,76).M.tbdormancy-related proteins Rv2659c and Rv1738 can mediate the production of inflammatory cytokines through the TLR4 pathways (77). Furthermore, the activated TLR4 can limit the survival of M.tb by inducing cellular autophagy (78).…”

Antigen identification strategies and preclinical evaluation models for advancing tuberculosis vaccine development

“…The use of HspX as a TLR agonist in adjuvant-based tumor immunotherapy has been reported 89 . Recent studies showed that dormancy-associated M. tuberculosis antigens such as Rv2627c, Rv2628, and Rv2659c induce innate and adaptive immune responses through TLR activation 90 , 91 . The adjuvant-like properties of these antigens could be harnessed for the rational design of multi-epitope subunit vaccines.…”