Objectives Population-based Chlamydia trachomatis seroepidemiological studies help to identify trends in chlamydia infection. However, an improved understanding of the antibody response to infection is required when using serology to estimate cumulative incidence. Thus, the objectives of this longitudinal, retrospective, biobank-based study were to assess the appearance and persistence of C. trachomatis major outer membrane protein (MOMP)-specific serum IgG antibodies after infection and to evaluate the role of antibodies in providing protective immunity against recurrent infection.
Methods Data of notified C. trachomatis infections in Finland were obtained from the National Infectious Diseases Register. Serum samples were acquired from the Finnish Maternity Cohort. 411 women with single chlamydia infection and 62 women with recurrent infections, and for whom suitable paired serum samples were available, were included in the study. Antibody appearance, persistence after infection and the impact of recurrent infections were evaluated. IgG antibodies specific for MOMP were measured from serum using an ELISA method.
Results Anti-C. trachomatis MOMP-specific IgG antibodies were detected in 65.5% (269/411) of women within 3 months of notification of infection. In the absence of recurrent infection, seroprevalence declined to 34.5% (142/411) 3–10 years after the initial infection. The serum antibody levels at baseline correlated positively with seroprevalence at follow-up. Reinfection boosted the humoral immune response by increasing seroprevalence and the serum antibody levels. Seroprevalence within 3 months after first notification of infection was 65.5% (19/29) in women who were later diagnosed with recurrent infection, comparable with women with single notification of infection (65.5%, 269/411).
Conclusions Approximately one-third of women with single notification of chlamydia infection remain seropositive 3–10 years after the initial infection. The concentration of antibodies remained stable during the follow-up. Recurrent infection boosted the humoral immune response, but reinfection occurred despite the presence of pre-existing antibodies.
- chlamydia trachomatis
- epidemiology (general)
- chlamydia infection
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Handling editor Nigel Field
Contributors H-MS devised the project. H-MS and HÖ designed the study. HÖ performed case selection and data analysis. HÖ, H-MS, PJ-K, TR and AT were involved in the interpretation of findings. HÖ wrote the first draft of the manuscript, and all authors commented and contributed to subsequent revisions and approved the final version.
Funding This work was supported by a research grant from the Helsinki University Hospital (grant number TYH2016255).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study was approved by the National Institute for Health and Welfare (reg no THL/503/6.02.00/2016) and by the ethics committee of the Hospital District of Helsinki and Uusimaa (reg no 18/13/03/03/2016).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available.
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