Chlamydia trachomatis Pgp3 Antibody Persists and Correlates with Self-Reported Infection and Behavioural Risks in a Blinded Cohort Study

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.

Chlamydia trachomatis Incidence Using Self-Reports and Serology by Gender, Age Period, and Sexual Behavior in a Birth Cohort

“…Sera collected at the age 26, 32 and 38 assessments were tested for antibodies to Pgp3 using a double-antigen sandwich ELISA, as previously reported. 7 When the assay was assessed in individuals with confirmed infection recruited at various times since treatment from UK genitourinary medicine clinics, the assay was 82.9% (95% confidence interval [CI] 77.0-88.8%) sensitive in women and 54.4% (64.5-78.6%) sensitive in men. 6,7,11 Using a reference standard of sera from micro-immunofluorescence assay negative children aged 2-13 years, the Pgp3 assay was 97.8% specific.…”

“…7 When the assay was assessed in individuals with confirmed infection recruited at various times since treatment from UK genitourinary medicine clinics, the assay was 82.9% (95% confidence interval [CI] 77.0-88.8%) sensitive in women and 54.4% (64.5-78.6%) sensitive in men. 6,7,11 Using a reference standard of sera from micro-immunofluorescence assay negative children aged 2-13 years, the Pgp3 assay was 97.8% specific. 7,11 The Pgp3 antibody response has also been shown to persist in 83.8% in men and 96.5% in women at least 12 years after seroconversion.…”

“…6,7,11 Using a reference standard of sera from micro-immunofluorescence assay negative children aged 2-13 years, the Pgp3 assay was 97.8% specific. 7,11 The Pgp3 antibody response has also been shown to persist in 83.8% in men and 96.5% in women at least 12 years after seroconversion. 7 Participants were considered to have evidence of chlamydia if they self-reported a diagnosis and/or had positive serology.…”

“…7,11 The Pgp3 antibody response has also been shown to persist in 83.8% in men and 96.5% in women at least 12 years after seroconversion. 7 Participants were considered to have evidence of chlamydia if they self-reported a diagnosis and/or had positive serology.…”

“…5,6 However, we have shown that a recently developed double-antigen sandwich enzyme-linked immunosorbent assay (ELISA) to detect antibodies to Pgp3, a C. trachomatis-specific antigen, is more sensitive than current major outer membrane protein (MOMP) assays. 7 We have previously examined all sexually transmitted infection (STI) incidence in the Dunedin Multidisciplinary Health and Development Study (DMHDS) birth cohort. 8,9 Based on self-reports of all STIs up to 32 years of age, we showed the period up to age 21 is the time of highest infection rate for women, and for men from age 21-26 years.…”