Cell-mediated immune response to epitopic MAP (multiple antigen peptide) construct of LcrV antigen of Yersinia pestis in murine model.

Yersinia pestis is the causative agent of plague. Cellular immunity seems to play an important role in defense against this disease. The subunit vaccine based on V (Lcr V) antigen has been proved to be immunogenic in animals and in humans. The multiple antigen peptide (MAP), incorporating all the relevant B and T cell epitopes is highly immunogenic in mice through intranasal route of immunization in PLGA particles containing CpG-ODN as an immunoadjuvant inducing humoral and mucosal immune response. In the present study, cell-mediated immune response using same MAP was studied in murine model. Primary and memory T cell responses were studied in outbred and inbred mice immunized intranasally with MAP in the presence of two immunoadjuvants (Murabutide and CpG-ODN). All the three compartments (Spleen, Lamina propria and Peyer's patches) of the lymphoid system showed increased lymphoproliferative response. Highest lymphoproliferative response was observed especially with CpG-ODN. Cytokine profile in the culture supernatant showed highest Th(1) and Th(17) levels. FACS analysis showed expansion of both CD4(+) and CD8(+) T cells producing gamma-interferon, perforin and granzyme-B with major contribution from CD4(+) T cells.

Humoral immune responses and protective efficacy of sequential B- and T-cell epitopes of V antigen of Yersinia pestis by intranasal immunization in microparticles.

Capsular F1 and secretory V antigen are the putative vaccine candidates for plague, caused by Yersinia pestis. Contemplating this, we studied the immunogenicity and protective efficacy of collinearly synthesized B- and T-cell epitopes (B-T constructs) of V antigen entrapped in poly (DL-lactide-co-glycolide) microparticles immunized intranasally using single dose immunization schedule in outbred, H-2(b) and H-2(d) mice. High antibody levels were observed in terms of IgG, IgA and SIgA peak titers in sera and mucosal washes to different B-T constructs. The constructs ai, bi and fi especially showed high peak antibody titers ranging from 51,200 to 204,000, which were maintained till day 120 post immunization. IgG/IgA Specific activity in sera and washes correlated well with the peak antibody titers. Moreover, all the B-T constructs showed mixed IgG1 and IgG2a/2b response, variable immunoreactivity as well as memory response with V antigen. B-T constructs, viz ai, ak, bi, fi, di and ik showed comparatively high isotype levels. These constructs showed high immunoreactivity, and good recall response with V antigen. Finally, in vivo protective study in BALB/c mice demonstrated the protective efficacy of three B-T constructs (ai, bi and fi) against lethal doses of Yersinia pestis till day 20 post challenge, while construct 'id' showed partial protection.