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

Abstract

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.

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

“…The predominance of the IFN-γ response to the different conjugates also indicates that cell mediated immune mechanism may be important in plague infection and these results correlate with similar findings with other studies [56]. During the in vivo protective study four conjugates of V antigen ai, bi, fi and id showed above 90% protection till day 15 and two conjugates of F1 antigen (B1T1 and B2T1) showed in vivo protection during challenge experiments in mice [35,38]. This can be attributed through the generation of relatively high CD4+ cells positive for both IFN-γ and perforin by the above conjugates.…”

“…ai, bi, fi and id also showed high T cell proliferation and Th1 type cytokine profile [39]. The same set of conjugates also showed in vivo protection during challenge experiment [35]. So, in the present study stimulation with the synthetic formulations resulted in release of cytokines that may help in the functions of phagocytic cells as well as promote phagocytosis of intracellular parasite.…”

“…Cytokine release profile of these B-T constructs were shown to be Th1 polarized. Since some of the B-T constructs of F1 and V antigens showed in vivo protection during challenge experiment [35,39] the role of CD4+ T cell in releasing perforin and IFN-γ as a measure of cytolytic activity as a marker of in vivo protection was evaluated in detail. The aim of the current study was to evaluate the cytokine profile and its contribution to immune response by measuring perforin, IFN-γ expressing T cells using prominent B-T constructs of F1 and V antigens of Y. pestis.…”

Recent Advancement in the Development of Vaccines Against Y. pestis - A Potential Agent of Bioterrorism

“…Furthermore, mice immunized intranasally with B-T conjugates of V antigen peptides entrapped in microspheres resulted in high titers of serum and mucosal IgG and IgA upto 120 day postimmunization. Interestingly, some of the conjugates showed enhanced protection in mice challenged with live bacteria (Uppada and Rao, 2009). Gupta et al (2009) demonstrated the cell mediated immune response of some of the best B-T conjugates in different strains of mice.…”

Recent publications in medical microbiology and immunology: a retrospective

“…Of distinct interest, related work has led to progress on vaccine development against buruli ulcer disease [57]. New strategies for antibacterial prophylaxis and vaccination based on the use of bacteriophages [58], of microparticleor nanoemulsion-based vaccines [59,60], or by stimulation of innate immunity [61] have been presented.…”