Non-invasive monitoring of humoral immune responses in men with acute Chlamydia trachomatis urethral infection using first-catch urine

Abstract We investigated the relationship between Chlamydia trachomatis (CT) load and anti-chlamydial antibody using first-catch urine from 108 men with nongonococcal urethritis. Men who reported prior CT 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 CT and with anti-chlamydial IgG regardless of infection history. Overall, we document genotype-specific differences in CT load, clarify that partial immunity associated with repeat infections is not antibody-mediated, and demonstrate a method to monitor humoral immune responses to CT in men using non-invasively collected urine.