Abstract
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.
Highlights
Chlamydia trachomatis (Ct) infection, if untreated in women, can result in pelvic inflammatory disease, a condition leading to significant reproductive morbidity [1,2,3]
We examined Pgp3 antibody associations in participants of the New Zealand Dunedin Multidisciplinary Health and Development Study (DMHDS), a birth cohort study in which detailed information on sexual behaviour and health have been collected at regular intervals from age 18–38 years [19]
We show Ct infection was both common and usually undetected in women in this New Zealand cohort born in 1972 and 1973, with almost a third of women by this age having been infected by age 38, and demonstrate a strong and consistent correlation of Pgp3 seropositivity with self-reported Ct, multiple sexual partners and age of first intercourse
Summary
Chlamydia trachomatis (Ct) infection, if untreated in women, can result in pelvic inflammatory disease, a condition leading to significant reproductive morbidity [1,2,3]. Opportunistic or screening programmes have been recommended or implemented in several countries to reduce prevalence and, subsequently, incidence and reproductive sequelae [4, 5], but their effectiveness has never been confirmed by randomised controlled trials. We previously produced an indirect lgG Enzyme Linked Immunosorbent Assay (ELISA) to detect antibody to Ct-specific Pgp protein [9]. To maximise detection rates of past infection, we have developed a Pgp double-antigen sandwich ELISA, as has been done for other infections, including HIV-1, Hepatitis B and Hepatitis E [15,16,17]. Double-antigen assays require that each protein-specific antibody recognises the specific epitope of the antigen bound to an ELISA plate, as well as binding the same epitope on labelled Pgp, allowing detection of lower antibody titres [18]
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