Investigating the Classification of Spontaneous Resolution of Chlamydia Trachomatis Infection Using an Immunoglobulin-Based Molecular Approach

Background: We previously found that about 20% of women with a positive Chlamydia trachomatis (CT) screening test (NAAT) had spontaneously cleared their infection (a “resolver”) by the time they returned for treatment (median 2 weeks). Since NAAT relies on detection of nucleic acids, it might fail to differentiate between a CT infected versus exposed individual. In this study, we are utilizing CT elementary body (EB) ELISA to classify resolvers based on IgG1 (G1) and IgG3 (G3) detection in the serum.

Methods: In an ongoing study, women returning for treatment of a positive cervical CT NAAT are enrolled and NAAT is repeated at the treatment (baseline) and 6-month follow up visits.  Women with negative NAAT at baseline are classified as resolvers. For this study, resolvers’ sera is being tested by EB ELISA to detect G1, a long-lived antibody, and G3, a more short-lived antibody that begins to decline within a 6-month period suggesting more recent infection.

Results: To date, we have performed EB ELISA on 66 resolvers. 47(71.2%) were G1+/ G3+ at both visits indicating a recent infection. 12 (18%) were G3- at both visits, suggesting  they were exposed to CT but not recently infected: 9/12 were G1+  at baseline suggesting they had a more remote infection and 3/12 were G1-  at both visits, suggesting they never had a CT infection. 2 (3%) were G1- at baseline but became G1+ at follow up, suggesting a primary infection. 3 (4.5%) were G1+/G3- at baseline but they seroconverted G3 at follow up suggesting acute infection.

Conclusions: Using both NAAT and EB ELISA, we demonstrated up to one out of six women classified as having resolved CT infection may have never been infected but merely exposed. Also, using G1 and G3 detection, we were able to define various stages of infection.