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 IgG 1,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.