Examination of the in vivo immune response elicited by Chlamydia psittaci in chickens

Intranasal immunization with inactivated chlamydial elementary bodies formulated in VCG-chitosan nanoparticles induces robust immunity against intranasal Chlamydia psittaci challenge

“…Our previous studies in mice using C. trachomatis confirm that vaccine regimens, which afford protection against challenge also stimulate CD4 + T cells that secrete high levels of the Th1 type cytokine, IFN-γ 35 , 48 . However, other studies indicate that CD8 + T cells may play a more crucial role than CD4 + T cells in protection against C. psittaci 17 . We also noted that lung lavage fluids of chickens immunized with EB alone secreted significantly higher levels of the anti-inflammatory cytokine, IL-10 compared to EB in combination with either VCG or CpG, irrespective of route of vaccine delivery.…”

“…We observed a significant increase in MOMP-specific antibody titers following both IN and IM immunization when compared to the controls, indicating the ability of inactivated EB in combination with either VCG or CpG to elicit substantial humoral immune responses following both mucosal and systemic delivery. While the role of CD4+ and CD8 + T cell-dependent mechanisms in protection against Chlamydia has been established 17 , 71 , the relative contribution of antibody in the resolution of a primary chlamydial infection is still unfolding. Thus, although there was no difference in the course of a primary genital chlamydial infection in B‐cell‐deficient and control mice, the former suffered more intense disease upon reinfection than the control mice 72 .…”

“…Early studies revealed that unlike CD4 + T cells, elimination of CD8 + T cells does not compromise protection against a C. trachomatis genital infection 16 . On the hand, while in vivo depletion of CD8 + T cells in mice abrogated protection against C. psittaci infection , depletion of CD4 + T cells did not affect protection 17 indicating that CD8 + T cells may play a more crucial role than CD4 + T cells in protection against C. psittaci. Although both T-cell-mediated and humoral immune responses are known to be elicited following chlamydial infection, a number of studies have demonstrated that the presence of antibodies during natural or experimental infection does not correlate with protection.…”