Characterization of Immune Responses to Yersinia pestis (Indian Isolate) Infection in Mouse Model

Abstract

Yersinia pestis, causative agent of plague, is one of the deadliest pathogens around globe. Innate immune response is first line of host defense against pathogens. Here, we have investigated innate and adaptive immune response in plague infected mice, gene expression levels of TLR1-9 and CD14, MyD88, NF-A„¸B, TNF-α, MAPKp38, IL-1β were studied in peritoneal macrophages of plague infected mice in a time dependent manner (0 h, 24 h, 48 h, 72 h, 96 h and 120 h of post infection) by qRT-PCR. We also evaluated the immune response to Yersinia outer proteins (Yops) in Y. pestis infected mice. Selected genes (11 numbers) of Y. pestis encoding virulent factors viz, YpkA, YopH, YopM, V antigen, Pla, YopN, YopJ, YopE, YopK, F1 and pH6 antigen were amplified by PCR, cloned and expressed in Escherichia coli . To study the IgG and its isotypes level, ELISA and immunoblotting were performed using purified recombinant antigens. The major antigens recognized by murine plague infected sera were V antigen, YopH, YopM, YopE, F1 but very weak immunoreaction was observed in case of Pla. We observed a significant difference in IgG isotypes (IgG1, IgG2a, IgG2b and IgG3) to V antigen and F1, whereas in case of YopH and YopE (IgG1 and IgG2b) only. We also observed significant increase in the expression of CD14 at 48 h post infection, TLR4 and MyD88 at 72 h post infection in Y. pestis infected mouse peritoneal macrophages. Our findings suggest that both innate and humoral immune responses are crucial for protection.