Immune response in chlamydial conjunctivitis among neonates and adults with special reference to tear IgA

Tear and serum samples from 128 neonates and 122 adults with conjunctivitis were examined for antibodies to Chlamydia trachomatis with a micro-immunofluorescence (MIF) technique and the results compared to antigen detection by culture, enzyme immunoassay (EIA) (Chlamydiazyme, Abbott) and direct immunofluorescence (IF) (MicroTrak, Syva and Chlamyset, Orion) tests. From the 52 culture-positive adults, chlamydial IgA (titre greater than or equal to 1:8) antibodies were detected in 81% of the tear and in 62% of the serum samples, while 88% had such serum IgG antibodies (titre greater than or equal to 1:32). The persistence of chlamydial IgA in tears and sera was related to the duration of symptoms of conjunctivitis and the antibody titres declined after institution of antibiotic treatment. In the adults, the sensitivity of the MIF tear IgA antibody test (81%) was higher than that of the EIA (71%) and the IF (MicroTrak 71% and Chlamyset 62%) tests. The specificity for the MIF test was 79%, while it was 100% for the EIA and the two IF tests. Of the 67 chlamydia-infected neonates, 36% had chlamydial tear IgA antibodies, while such antibodies were only found in 15% of the sera. No neonates with chlamydia-negative conjunctivitis had chlamydial IgA antibodies. The MIF test may be used as a diagnostic method complementary to culture, EIA and IF tests in the diagnosis of chlamydial conjunctivitis in adults, but is not applicable in neonates.