Induction of Cross-Serovar Protection against Genital Chlamydial Infection by a Targeted Multisubunit Vaccination Approach

Abstract

An important consideration for antichlamydial vaccine development is the induction of cross-serovar protection, since multiple serovars (D to L) of Chlamydia trachomatis cause genital infections. We have shown previously that vaccination with C. trachomatis-derived recombinant chlamydial protease-like activity factor (rCPAF) induced significant earlier resolution of Chlamydia muridarum infection and reduced oviduct pathology. However, the vaccinated mice continued to shed chlamydiae for up to 2 weeks after challenge. In this study, C. trachomatis serovar D recombinant proteins, such as recombinant major outer membrane protein (rMOMP), recombinant inclusion membrane protein A (rIncA), and rCPAF were administered intranasally, individually or in combinations, with murine interleukin-12 (IL-12) as an adjuvant, and cross-species immunity against intravaginal C. muridarum infection was examined. Immunization with rCPAF plus IL-12 (rCPAF؉IL-12), compared to immunization with rIncA؉IL-12 or rMOMP؉IL-12, induced the greatest antigen-specific gamma interferon production from purified CD4 ؉ T cells and concurrently enhanced serum antibody production. All (100%) the animals vaccinated with rCPAF؉IL-12 alone or in any combination completely resolved the infection by day 18 after challenge compared to animals vaccinated with rIncA؉IL-12 (50%), rMOMP؉IL-12 (33%), or phosphate-buffered saline (mock vaccinated; 0%). Moreover, oviduct pathology in mice vaccinated by any regimen that included rCPAF, but not rMOMP؉IL-12 or rIncA؉IL-12 alone, was markedly reduced compared to mock-immunized animals. The addition of rMOMP and/or rIncA did not significantly enhance the rCPAF؉IL-12-induced effect on bacterial clearance or oviduct pathology. These results suggest a greater conservation of protective linear antigenic epitopes within CPAF than MOMP or IncA across the examined serovars and the need to identify other highly conserved antigens for use with rCPAF in a multisubunit recombinant vaccine.

Mice Deficient in MyD88 Develop a Th2-Dominant Response and Severe Pathology in the Upper Genital Tract following Chlamydia muridarum Infection

“…Each tissue sample was homogenized in 400 ml SPG, followed by a brief sonication on ice. The released organisms from either the swab or tissue homogenate samples were immediately titrated on HeLa cell monolayers in duplicates as described previously (42). Briefly, serially diluted samples were inoculated onto HeLa cell monolayers grown on coverslips in 24-well plates.…”

“…The H&E-stained sections were assessed by a certified pathologist (I-T.Y.) blinded to mouse treatment and scored for severity of inflammation and pathologies based on the modified schemes established previously (10,42,43). The uterine horns and fallopian tubes were scored separately.…”

Manipulation of Host Vesicular Trafficking and Membrane Fusion During Chlamydia Infection

“…It is intriguing that some inclusion proteins appear to be highly immunogenic in humans, hinting at possible targets for future vaccine development 6 [Li et al, 2007]. This observation makes studying the biochemical properties of inclusion proteins all the more important.…”

“…6 It may seem counterintuitive that bacterial proteins expressed only within live infected host cells could have therapeutic abilities since those antibodies would most likely not bind the extracellular EB form of the organism. Recent data using mice, however, show that a vaccine consisting of recombinant CtrIncA plus murine interleukin-12 administered prior to genital challenge by C. trachomatis confers resistance to the pathogen beyond background levels (Li et al 2007). This vaccine resulted in a robust humoral response correlating with reduced sequelae associated with genital infection.…”

REVIEW ARTICLE: Chlamydia trachomatis, a Hidden Epidemic: Effects on Female Reproduction and Options for Treatment

“…81 The vaccine candidate currently at the forefront of current chlamydial vaccine research is chlamydial protease-like activity factor (CPAF) and is possibly the candidate closest to human clinical trials. CPAF has been extensively studied in the murine model of genital infection [82][83][84][85][86][87] and has proven, with the use of adjuvants such as IL-12 and CpG-ODN, 82,85 to be able to reduce the level of Chlamydia shed from the genital tract and prevent the development of pathology, thereby preserving reproductive health. 82,[84][85][86]88 Due to CPAF being highly conserved between chlamydial species 89 and the fact that transgenic mice expressing human leukocyte antigen-DR4 molecules, rather than mouse major histocompatibility complex class II molecules, are able to mount robust protective immune responses, 87 this suggests CPAF could be a good candidate for an efficacious vaccine, especially when used in combination with other protective antigens.…”