Chlamydia trachomatis (Ct) serological studies in populations could help monitor changes in lifetime cumulative risk of infection. We developed a double-antigen sandwich ELISA based on the Ct-specific Pgp3 antigen, then tested blind stored sera from over 800 participants in a New Zealand birth cohort from Dunedin at ages 26, 32 and 38. The double-antigen sandwich ELISA was more sensitive than our previously characterised indirect Pgp3 ELISA. Pgp3 antibody was detected more often in women compared to men and correlated with increasing numbers of sexual partners, self-reported Ct, and younger age at sexual debut in both women and men. At age 26, 24.1% (99/411) of women were Pgp3 seropositive, as were 79.5% (35/44) of those reporting Ct infection; Pgp3 antibody persisted to age 38 in 96.5% (83/86). In men at age 26, the figures were 10.7% (47/442) and 25.0% (6/24), respectively, with high (83.9%) antibody persistence to age 38. At age 38, among those Pgp3 seropositive, 63.3% of women and 83.1 % of men had not reported Ct infection. Thus, Ct-specific Pgp3 antibody was detected in most women reporting Ct infection and correlated with risk of infection in those who did not, with most infections remaining undetected. As this antibody persisted for at least twelve years in 96% of these women, serology could be used to evaluate Ct prevention programmes among women.
Bibliographical noteFunding Information:
This work was supported by The Health Research Council of New Zealand. 09/086, www.hrc. govt.nz/ (NPD); NIHR Health Protection Research Unit in Evaluation of Interventions at the University of Bristol, www.nihr.ac.uk/funding/health-protectionresearch-units.htm, HPRU-2012-10026 (PH and DK); Health Protection Agency (now Public Health England) funded the testing of stored sera (GW and SV). The funders played no part in the design, conduct, analysis or reporting of this study, nor in the decision to submit the manuscript for publication. We wish to thank the DMHDS members and their families for their long-term involvement, the current study director, Professor Richie Poulton, past director Dr Phil Silva, and all staff involved in data collection and other aspects of the study.