Role of toll-like receptor 4 in eliciting adaptive immune responses against recombinant BCG expressing the C-terminus of merozoite surface protein-1 of Plasmodium falciparum

ABSTRACT

Objective: To determine the role of toll-like receptor 4 (TLR-4) in eliciting cellular and humoral immune responses against recombinant Mycobacterium bovis bacille Calmette-Guérin (rBCG) expressing the C-terminus of merozoite surface protein-1 of Plasmodium falciparum. Methods: Six groups of mice (n=6 per group) were injected with phosphate buffered saline T80, BCG or rBCG intraperitoneally, in the presence or absence of a TLR-4 inhibitor; TAK-242. Enzyme-linked immunosorbent assay was carried out for serum total IgG, IgG1, IgG2a and IgG2b determination. Spleens were also harvested and splenocytes cultured for determination of intracellular cytokines; IL-4 and IFN-γ via enzyme-linked immunosorbent assay. Results: The production of total IgG, and the subclasses IgG1, IgG2a and IgG2b was significantly higher in rBCG-immunised mice than BCG and phosphate buffered saline immunised mice in the absence of TAK-242. A significant rise in total IgG occurred with more booster immunisations. The level of IgG2a was highest, followed by IgG2b, then IgG1. The production of both IL-4 and IFN-γ was also highest in the rBCG immunised groups. These significant rises were inhibited in the presence of TAK-242. Conclusions: We present evidence of the role of TLR-4 in the increased production of total IgG, IgG1, IgG2a and IgG2b, as well as IL-4 and IFN-γ in response to our rBCG construct.