Chlamydia trachomatis serology: Protein 2 compared with that of other antigens diagnostic value of outer membrane

Different immunoassays using recombinant antigens or synthetic peptides wer e evaluated for the serodiagnosis of Chlamydia trachomatis infections. Anti gens used included cysteine-rich outer membrane protein 2 (OMP2), heat shoc k protein 60, the polypeptide encoded by open reading frame 3 of the plasmi d (pgp3), synthetic peptides derived from species-specific epitopes in vari able domain IV of the major OMP (MOMP) (Labsystems, Helsinki, Finland), and a fragment of the total lipopolysaccharide (Medac, Hamburg, Germany). Beca use cross-reactions between chlamydial species have been reported, Chlamydi a pneumoniae-specific antibodies were also determined by immunoassays (Labs ystems). Responses obtained with serum samples from patients with well-defi ned diseases (i.e., urethral or endocervical samples from which C. trachoma tis DNA was amplified) were compared to those obtained with samples from he althy blood donors. The best sensitivity (79%) associated with the best spe cificity (82%) was obtained when immunoglobulin G (IgG) responses to both M OMP and pgp3 were considered. The highest sensitivity (89%) was obtained wi th anti-OMP2 IgG, but the lowest specificity (57%) was obtained with this a ntibody, due to probable cross-reactivity with C. pneumoniae OMP2.