The seroepidemiology of Chlamydia Trachomatis in 13-15-year-olds in England

Abstract

Urogenital infection with Chlamydia trachomatis is the most commonly diagnosed sexually transmitted infection in the developed world. No systematic investigation of the seroprevalence of C. trachomatis in the under 16s population in England has been conducted. This is despite evidence of chlamydial diagnoses and increasingly earlier sexual debut. As the National Chlamydia Screening Programme only recruits patients aged 15-24-years-old for chlamydial screening, seroprevalence data will provide insight into the need for screening younger patients. However, accurate measurement and therefore understanding the seroprevalence of urogenital C. trachomatis infections requires a rigorously optimised and validated ELISA. Previous ELISAs based on the C. trachomatis plasmid-encoded protein, PGP3, have been described but lack standardisation and critical controls or use a less commonly derived PGP3 as the capture antigen. The aim of this study was to develop a sensitive and specific indirect ELISA based on recombinant PGP3 derived from a urogenital strain of C. trachomatis, serovar E (pSW2), using a rigorous validation protocol. The next aim was then to apply this ELISA to detect anti-PGP3 antibodies in a significant number of patient sera collected from patients under 16-years-old from England to determine the seroprevalence of C. trachomatis in this population.
To evaluate the ELISA, serum samples were collected from 166 male and female genitourinary medicine clinic patients diagnosed as positive or negative for urogenital C. trachomatis infection by nucleic acid amplification testing. Overall sensitivity and specificity compared to nucleic acid amplification testing was 68.18% and 98.0%, respectively. Sensitivities for female and male samples were 71.93% and 64.15%, respectively. Comparison of samples from these patients diagnosed positive for C. trachomatis by nucleic acid amplification testing and patients diagnosed negative by nucleic acid amplification testing revealed statistical significance (p = <0.0001). This ELISA was further validated by demonstrating that sera from mice urogenitally infected with C. trachomatis produce measureable responses to recombinant PGP3. In contrast to previous reports, it has also been shown that human antibody recognition of PGP3 is not solely dependent on its homotrimeric conformation.
To determine the seroprevalence of C. trachomatis in the under 16s population in England, 2119 serum samples received from the Seroepidemiology Unit were assayed. Overall seroprevalence in 13-, 14- and 15-year-olds from all combined serum sources was 6.87%, 6.70% and 10.47%, respectively. The seroprevalence of antibodies to PGP3 in serum samples collected from male and female 13-, 14- and 15-year-olds not sourced from GUM clinics was 4.66%, 4.37% and 10.78%, respectively. The overall seroprevalence of antibodies in samples collected from 13-, 14- and 15-year-olds sourced from an unknown or unrecorded source was 7.10%, 6.26% and 6.75%, respectively. Finally, the seroprevalence of antibodies in samples collected from 13-, 14- and 15-year-olds sourced from GUM clinics was 18.52%, 18.18% and 24.32%, respectively.
In conclusion, for the first time, the seroprevalence rate of anti-PGP3 antibodies within serum samples collected from 13-15-year-old children in England has been determined using a validated sensitive and specific ELISA based on recombinant PGP3 derived from C. trachomatis, serovar E (pSW2). The results from this study suggest that the seroprevalence rate of antibodies in 15-year-olds is similar to the seroprevalence rate in 17-18-year-olds reported in a previous study and therefore the standards of chlamydial screening currently applied to 16-24-year-olds should also be applied to 15-year-olds

More information

Identifiers

ORCID for Ian Clarke: orcid.org/0000-0002-4938-1620

Catalogue record

Export record