Seroprevalence of antibodies against Chlamydia trachomatis inclusion membrane proteins B and C in infected symptomatic women

Background: Proteins in the inclusion membrane of Chlamydia trachomatis (CT) have been anticipated to play pivotal roles in the molecular and cellular interactions between the pathogen and host. However, there is lack of data on host immunity with respect to antibody responses against chlamydial inclusion proteins. Methodology: We used full-length fusion proteins for CT inclusion membrane proteins B and C (IncB and IncC respectively), two early-infection phase proteins, to study their role in antibody generation during human infection. Results: Three hundred and fifty-five women (aged 22-36 years) attending the Gynaecology outpatient department, Safdarjang Hospital, New Delhi, India were enrolled in this hospital ethical committee approved study. Out of these, 108 were diagnosed to be cervical CT-positive. Of these 108 patients, 67 (62.03%) showed ELISA positivity for IncB IgG, and 64 (59.25%) for IncC IgG. There was a positive correlation between antibody titres against IncB and IncC and with antibodies against CT major outer membrane protein (MOMP) in CT-positive sera. Our data also showed a positive association between antibody titres against IncB and IncC in patients with cervicitis and pelvic inflammatory disease (PID). Significantly high antibody titres were detected in cervicitis cases compared with PID. There were significantly higher levels of serum cytokines (TNF-alpha, IFN-gamma. and IL-12) in Inc-positive cervicitis cases than in PID cases. In addition, our study also showed higher IncB and IncC IgG(2) titres in comparison to respective IgG(1), IgG(3) and IgG(4) titres in CT-positive sera. Conclusion: Our data suggested that antibodies against CT IncB and IncC were prevalent in CT-positive women diagnosed with cervicitis or PID.