Some characteristics of a secreted chlamydial antigen recognized by IgG from C. trachomatis patient sera.

Chlamydia trachomatis serovars release a glycolipid antigen (GLXA) into the culture supernatant during the infective cycle. This antigen is recognized by IgG isolated from humans with a natural chlamydial infection; GLXA may be a major antigenic determinant of chlamydia. It can be immunopurified by molecular shift or affinity chromatography. Silver staining of SDS-PAGE gels demonstrates a pattern of bands that is essentially the same for preparations isolated by either method. GLXA can also be extracted from mature elementary bodies (EB). These preparations show the same pattern of silver staining bands, and the major bands are immunoreactive as shown by Western blot analysis. Isoelectric focusing studies demonstrate that purified GLXA has an acidic pI.