Abstract

Mycobacterium tuberculosis (MTB), the etiological factor of tuberculosis (TB), is among the most successful of intracellular pathogen that regulates the host immune response. Cellular immune responses perform a pivotal function in host defence against MTB. Thus, it is vital to understand the antigens which drive immune protection, especially Th1-type cellular immunity. The role of 3-hydroxyacyl-l-thioester dehydratase (HtdY, Rv3389c) of MTB in immunological protection was observed in dendritic cell (DC) activation and T cell immunity herein. Recombinant HtdY was applied for inducing maturation and activation of DCs obtained from murine bone marrow. TLR4 and TLR2 knockout mice and pharmacological inhibitors were used to investigate the mechanism by which HtdY activates DCs. MLR assay was performed to characterize HtdY activity with respect to DC activation and T cell polarization. The alteration of cytokines secretion by human PBMCs elicited by HtdY was observed. We found that HtdY prompted DC maturation and activation through augmenting the expression of surface molecule CD80, CD86 and MHC II, and the release of pro-inflammatory cytokines including IL-1β, IL-6, IL-12 and TNF-α from DCs. HtdY-drived DC activation involved TLR4 activation and mitogen-activated protein kinases (MAPKs) signaling pathway. DCs treated with HtdY induced naïve CD4+ T cells to produce IFN-γ. Human PBMCs had higher TNF-α and lower IL-10 response to HtdY in active TB group than that in control group (p<0.01). Our results indicated that HtdY possesses potential to drive Th1-type cellular immunity by TLR4- mediated activation of DCs.

Keywords: Mycobacterium tuberculosis; HtdY; DC maturation; TLR4; Th1 polarization; IL-10