Enzyme-linked immunosorbent assay for chlamydial antibodies

An enzyme-linked immunosorbent assay (ELISA) detected chlamydial antibodies in human sera. The assay antigen produced in cell cultures infected with Chlamydia psittaci was Formalin-fixed to microplates. Single convalescent-phase sera positive for chlamydial antibodies by a complement-fixation test were positive at even higher dilutions by ELISA. Paired sera with diagnostic rises in complement-fixing antibody showed seroconversion by ELISA also. Control sera from persons with no history of chlamydial infection were negative by both tests. Sera from patients with psittacosis or lymphogranuloma venereum were ELISA positive, indicating that the assay with the antigen used in this study is genus specific rather than species specific.