Immunoglobulin-Based Investigation of Spontaneous Resolution of Chlamydia trachomatis Infection

Abstract

Chlamydia trachomatis elementary body enzyme-linked immunosorbent assay (ELISA) was used to investigate serum anti-CT immunoglobulin G1 (IgG1; long-lived response) and immunoglobulin G3 (IgG3; short-lived response indicating more recent infection) from treatment (enrollment) and 6-month follow-up visits in 77 women previously classified as having spontaneous resolution of chlamydia. Of these women, 71.4% were IgG1+IgG3+, consistent with more recent chlamydia resolution. 15.6% were IgG3- at both visits, suggesting absence of recent chlamydia. Using elementary body ELISA, we demonstrated approximately 1 in 6 women classified as having spontaneous resolution of chlamydia might have been exposed to C. trachomatis but not infected. Further, we classified their possible infection stage.

Keywords: IgG1; IgG3; antibody; chlamydia; clearance; elementary body enzyme-linked immunosorbent assay (EB ELISA); immunoglobulin; resolution.

Figure 1.

Effect of timing/duration of Chlamydia trachomatis (CT) infection on the change in the magnitude of anti-CT immunoglobulin G1 (IgG1) and immunoglobulin G3 (IgG3) responses between treatment and follow-up visits. Line graph depicting the changes in the median optical density of 405 nm (OD₄₀₅) of anti-CT IgG1 and IgG3 responses detected by CT elementary body (EB) enzyme-linked immunosorbent assay (ELISA) from a CT treatment visit (Tx) to a follow-up visit (FU) (on average approximately 6 months after treatment). Closed and open circles represent median OD₄₀₅ value for IgG1 and IgG3 responses, respectively. The different infection timing/duration categories that were defined based upon seropositivity of IgG1 and IgG3 at Tx and FU visits are indicated on the x-axis. Dashed and dotted lines indicate the EB ELISA OD₄₀₅ cutoff for IgG1 (0.35) and IgG3 (0.1), respectively. In the recent infection group, the magnitude of the IgG3 response significantly declined between the Tx and FU visits (median OD₄₀₅ = 1.012 vs 0.876; P = .01); however, there was no significant change in the IgG1 response (median OD₄₀₅ = 4.000 vs 3.872; P = .44). In the remote infection group, there was no significant change in the magnitude of the IgG1 or IgG3 response between Tx and FU visits (IgG1: median OD₄₀₅ = 0.798 vs 0.936, P = .74; IgG3: median OD₄₀₅ = 0.053 vs 0.063, P = .73). The magnitude of the IgG1 and IgG3 responses were significantly higher at both the Tx and FU visits for the recent infection group versus the remote infection group (all P values < .001). Due to the small sample size in the acute, primary, and no infection groups (n < 5 in each group), statistical analyses were only performed for the recent and remote infection groups. Abbreviations: FU, follow-up visit; IgG1, immunoglobulin G1; IgG3, immunoglobulin G3; OD₄₀₅, optical density of 405 nm; Tx, treatment visit.