Evaluation of CD4+/CD8 + T-cell expression and IFN-γ, perforin secretion for B-T constructs of F1 and v antigens of Yersinia pestis

Yersinia pestis is a facultative bacterium that can survive and proliferate inside host macrophages and cause bubonic, pneumonic and systemic infection. Understanding the immune response generated by epitopes recognized by CD4 + and CD8 + T cells is important for the development of safe and effective vaccines designed to promote protective cellular immunity. Apart from humoral response, CD4 + T cells have shown to have a major role in combating the pneumonic form of the disease. In the present study, the secretion of IFN-γ and IL-4 by splenocytes, stimulated by different constructs of B and T cell epitopes of F1 and V antigens, was measured by ELISpot assay. We also measured perforin and IFN-γ expression as a function of cell mediated immunity by flow cytometry. Three B-T constructs of F1 and seven B-T constructs of V antigens produced a high number of IFN-γ secreting cells as compared to native antigen and a low number of IL-4 secreting cells. B-T conjugates of F1 and V antigens showed significantly high (p < 0.001) percentage of CD4 + IFN-γ ⁺ cells as compared to CD8 + IFN-γ ⁺ cells. Thus, the study highlights the importance of Th1 cytokine and existence of high proportion of CD4 + T cells probably contributing protection in the host. This study proposes a new perspective for the development of vaccination strategies for Y. pestis that trigger T cell immune response.