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 classifi ed in to 4 immunologically distinct groups on the basis of cross-prote ction experiments in a mouse model. To identify the molecular basis of their immunological divergence 4 representative strains were investig ated by cellular, molecular and immunological techniques. An identical pattern was obtained by AluI digestion of the amplified major outer m embrane 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 mon oclonal antibodies (mAbs) raised against abortion strains failed to re act with inclusions of the 2 strains. All 6 mAbs reacted with the chla mydial outer membrane complex (COMC). Two of these mAbs, one against t he MOMP and one against an antigen at 90 kDa, did not react with immmu noblots of LLG and POS. The data provide direct demonstration of the e xistence of strain variation in the field and classify strains LLG and POS as a distinct C. psittaci serotype 1-subtype. The antigenic diver sity among abortion strains should be taken into consideration when de signing a subunit vaccine.