Comparison of enzymatically active and denatured recombinant chlamydial protease like activity factor as protective immunogens against genital chlamydial challenge

• Main Author: Chaganty, Bharat Kumar Reddy
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2009
• Subjects: Cellular biology; Microbiology
• ISBN: 1109297327; 9781109297324

We have shown previously the efficacy of intranasal vaccination with recombinant chlamydial protease-like activity factor (rCPAF) plus interleukin-12 in the induction of enhanced genital chlamydial clearance and reduction of upper genital tract pathology. The protective immunity was mediated by IFN-γ producing CD4+ T cells, and did not require antibody, suggesting the predominant contribution of linear antigenic epitopes in this process. Moreover, CPAF is a protease that can degrade several host proteins, and may not be suitable for administration into humans in the proteolytically active form. Therefore, in this study, we compared the protective efficacy of proteolytically active and inactive (heat-denatured) rCPAF against primary genital C. muridarum challenge. Purified rCPAF was able to degrade human keratin 8 in a cell-free degradation assay before, but not after, heating at 95°C for 5 min, suggesting the generation of proteolytically active and inactive rCPAF. Active, but not inactive, rCPAF immunization induced high levels of anti-active CPAF total antibody, IgG1, IgG2a, and IgG2b. Both active and inactive rCPAF immunization induced robust splenic IFN-γ production upon stimulation with rCPAF or native CPAF produced during an active chlamydial infection of HeLa cells. Vaccination with active and inactive rCPAF induced enhanced vaginal chlamydial clearance as early as day 6 after challenge, and every time-point thereafter, compared to mock-vaccinated animals. Moreover, active and inactive rCPAF vaccinated animals completely cleared the infection by day 18, compared to mock-vaccinated mice that cleared by day 30 after challenge. Importantly, only 33% of active and inactive rCPAF-vaccinated mice displayed hydrosalpinx compared to 83% of mock-vaccinated animals. The degree of microscopic oviduct pathology also was significantly reduced in active and inactive rCPAF-vaccinated mice compared to mock-vaccinated animals. Collectively, these results demonstrate that rCPAF conformation is not a constraint for induction of robust protective anti-chlamydial immunity, and further suggest that rCPAF is a safe, effective, and stable anti-chlamydial vaccine candidate.