Chlamydial serology: Comparative diagnostic value of immunoblotting, microimmunofluorescence test, and immunoassays using different recombinant proteins as antigens

To improve the reliability of the serodiagnosis of Chlamydia trachomatis in fections, an immunoblot analysis, a microimmunofluorescence titration, and different immunoassays using synthetic peptides derived front species-speci fic epitopes in variable domain IV of the major outer membrane protein or r ecombinant antigens (heat shock protein 70 [hsp70], hsp60, hsp10, polypepti de encoded by open reading frame 3 of the plasmid [pgp3], macrophage infect ivity potentiator, and a fragment of the total lipopolysaccharide) were eva luated, Because cross-reactions between chlamydial species have been report ed, the microimmunofluorescence tests were also performed with Chlamydia pn eumoniae and Chlamydia psittaci used as antigens, and C, pneumoniae-specifi c antibodies were also determined by immunoassays, Since the presence of an timicrobial antibodies must be interpreted in light of their prevalence in the general population, responses obtained with serum samples from patients with well-defined infection (i.e., with positive urethral or endocervical C, trachomatis DNA amplification) were compared to those obtained with samp les from healthy blood donors, The best sensitivity (86%) with a specificit y of 81% was obtained for immunoblotting results, when the number of indivi duals with greater than or equal to 10 immunoglobulin G (Igc) and/or greate r than or equal to2 IgM responses to the different C, trachomatis antigens was considered. A 13-kDa antigen was recognized by most of the samples (86% for IgG) front patients with acute urogenital infection but rarely (3%) by those from healthy blood donors (P < 0.0001), The sensitivity and specific ity results obtained for serum antibodies to peptides or recombinant antige ns were slightly lower than those results obtained for the number of respon ses to whole C, trachomatis antigens, which were 76 and 77%, respectively, when IgG responses to both recombinant hsp60 and pgp3 were considered.