Limits of the microimmunofluorescence test and advantages of immunoblotting in the diagnosis of chlamydiosis

The Western blot (immunoblot) patterns of 56 serum specimens, all examined previously by the microimmunofluorescence (MIF) test for species-specific Chlamydia antibodies, were analyzed. Predominant specific-antibody activity was directed to the 170-, 155-, 145-, 120-, 115-, 100-, 57-, and 38-kDa proteins of Chlamydia trachomatis and to the 175-, 130-, 110-, 98-, and 30-kDa proteins of Chlamydia pneumoniae. All of these antigens appeared to be species specific The reactivity with 90-, 80-, 75-, 62- or 60-, and 55-kDa proteins and the major outer membrane protein appeared to be genus specific Fourteen serum samples which had identical titers of immunoglobulin G as determined by the MIF test were investigated by Western blotting. We found that nine serum samples had anti-C. trachomatis protein profiles and two had anti-C. pneumoniae protein profiles. The double seropositivity observed by MIP corresponded with cross-reactivity to genus-specific antibodies. As for the three remaining serum specimens, we observed identical protein profiles for C. trachomatis and C. pneumoniae, confirming the double seropositivity experienced with the MIF test. Western blotting can differentiate between specific reactions and interfering noise from other, partly cross-reacting chlamydial species.