Diversity among abortion strains of Chlamydia psittaci demonstrated by inclusion morphology, polypeptide profiles and monoclonal antibodies.

Twenty eight C. psittaci abortion strains had been previously classified in to 4 immunologically distinct groups on the basis of cross-protection experiments in a mouse model. To identify the molecular basis of their immunological divergence 4 representative strains were investigated by cellular, molecular and immunological techniques. An identical pattern was obtained by Alul digestion of the amplified major outer membrane protein gene (MOMP) by the polymerase chain reaction (PCR) of the 4 strains. However, inclusion morphology and polypeptide profiles clearly distinguished one strain, named LLG, and its homologous strain POS from the other prototypes by the presence of a unique protein at 26.5 kDa and the absence of a polypeptide at 23 kDa. Six out of 10 monoclonal antibodies (mAbs) raised against abortion strains failed to react with inclusions of the 2 strains. All 6 mAbs reacted with the chlamydial outer membrane complex (COMC). Two of these mAbs, one against the MOMP and one against an antigen at 90 kDa, did not react with immunoblots of LLG and POS. The data provide direct demonstration of the existence of strain variation in the field and classify strains LLG and POS as a distinct C. psittaci serotype 1-subtype. The antigenic diversity among abortion strains should be taken into consideration when designing a subunit vaccine.

Unusual prevalence of the rare serovar Da of Chlamydia trachomatis in Greece detected by monoclonal antibodies.

Twenty-seven monoclonal antibodies (mAb), eight with subclass-specificities and nineteen reacting with one or two C. trachomatis serovars, were developed and used to immunotype twenty-six clinical isolates from Greek patients with chlamydial infections. Twelve samples, first classified as serovar D, were identified as the recently established serovar Da on the basis of their negative reaction with mAb JG9, an mAb previously shown to distinguish between D and Da, and a new mAb 114D9 with similar specificity. The 12 Da strains represent the highest prevalence of the rare serovar Da that has been reported worldwide. Further characterization of mAbs JG9 and 114D9 revealed a unique cross-reactivity of the D-specific JG9 with the mouse biovar MoPn. Epitope mapping studies on overlapping synthetic peptides of the fourth variable domain of the MOMP of serovar D and Da localized the epitopes of JG9 and 114D9 and a D/Da specific mAb 113D5 within this domain. The results were consistent with the specificity of these mAbs observed with whole microorganisms and indicated their usefulness as epidemiologic markers.