Noninvasive Monitoring of Humoral Immune Responses in Men With Acute Chlamydia trachomatis Urethral Infection Using First-Catch Urine.

We investigated the relationship between Chlamydia trachomatis load and anti-chlamydial antibody using first-catch urine from 108 men with nongonococcal urethritis. Men who reported prior chlamydia had elevated anti-chlamydial IgA and lower loads, but load and antibody were not correlated. Load positively correlated with anti-chlamydial IgA only in men who did not self-report prior chlamydia and with anti-chlamydial IgG regardless of infection history. Overall, we document genotype-specific differences in C. trachomatis load, clarify that partial immunity associated with repeat infections is not antibody mediated, and demonstrate a method to monitor humoral immune responses to C. trachomatis in men using noninvasively collected urine.