Seroepidemiology of Chlamydia trachomatis Infection in the General Population of Northern China: The Jidong Community Cohort Study

Abstract

A longitudinal serological study to investigate the seropositive frequency, incidence, and antibody dynamics of Chlamydia trachomatis infection in the general population of China is urgently needed in order to optimize the strategies for surveillance and precise prevention of C. trachomatis infection. This longitudinal study enrolled 744 subjects aged 18-65 years from Jidong Community of Northern China from 2014 to 2018. Seropositive frequency, incidence, and reinfection of C. trachomatis were determined by detecting antibody against C. trachomatis Pgp3 using "in-house" luciferase immunosorbent assay (LISA). The dynamic of anti-Pgp3 antibody was analyzed using the Generalized Estimating Equation (GEE) model. The overall Pgp3 seropositive frequency among the 18-65-year-old population was 28.1% (95% CI 24.9-31.5), and significantly increased from 12.0% in those aged 18-29 years to 48.6% in the 60-65 years old. The seropositive frequency was slightly higher in women than in men (31.3% vs. 25.4%) without statistical significance. The C. trachomatis incidence and reinfection rate were 11 and 14 per 1,000 person-years, respectively, and showed no significant difference with respect to age, gender, ethnicity, marital status, and education levels. Furthermore, anti-Pgp3 antibody remained detectable in 93.3% (195/209) of the seropositive subjects during the 5 years of follow-up. The overall decay rate for anti-Pgp3 antibody for CT-infected persons was -0.123 Log2 RLU/year, which was dramatically slower than in CT new infection (-3.34 Log2 RLU/year) or reinfection (-1.1 Log2 RLU/year). In conclusion, at least one quarter of the people aged 18-65 years have been infected with C. trachomatis over their lifetime while all age groups are susceptible to C. trachomatis infection in the community of Northern China. Therefore, comprehensive prevention strategies are urgently needed.

Keywords: Chlamydia trachomatis; anti-Pgp3 antibody; antibody decay; general population; incidence; seropositive frequency.

FIGURE 1

Flowchart of participant enrollment.

FIGURE 2

Detection of anti-C. trachomatis Pgp3 antibody from 2014 to 2018. The subjects included in the longitudinal cohort study were followed up and tested for anti-Pgp3 antibody annually. The purple circle indicates the number of anti-Pgp3 antibody positive subjects, while the blue circle represents the number of anti-Pgp3 antibody negative subjects.

FIGURE 3

Frequency of anti-Pgp3 antibody by age groups in total population (purple), men (blue) or women (brown), China, 2014. Anti-Pgp3 antibody was tested in 744 participants including 405 men and 339 women in 2014. Seropositive frequency of C. trachomatis infection was represented by anti-Pgp3 IgG antibody positive rate. Solid lines indicate the frequency for whole population (purple), men (blue) or women (brown), respectively. Dash lines indicate the 95% “exact” Clopper–Pearson confidence interval of the seropositive frequency.

FIGURE 4

Dynamics of anti-Pgp3 antibody in C. trachomatis new infection (A) and reinfection (B). Dynamics of anti-Pgp3 antibody was analyzed in 17 newly CT-infected subjects and 10 CT reinfected subjects. Purple lines indicate the subjects who were seropositive for anti-Pgp3 during the follow-up, whereas blue lines indicate those with seroreversion. Black line represents the dynamics of antibody change estimated by GEE model analysis in which the solid lines mean the trend of antibody change is statistically significant while dash lines mean no statistically significant. In addition, dot lines indicate the cutoff value of anti-Pgp3 IgG antibody (Log2 RLU = 4.1). Slopes were estimated by GEE models.