DEMONSTRATION OF ANTIGENIC AND GENOTYPIC VARIATION IN ORIENTIA-TSUTSUGAMUSHI WHICH WERE ISOLATED IN JAPAN, AND THEIR CLASSIFICATION INTO TYPE AND SUBTYPE

A total of 40 strains of Orientia tsutsugamushi (34 isolates from pati ents and trombiculid mites in Japan, and 6 prototype strains of antige nic variants) were examined for classification based on the reactiviti es with type-specific monoclonal antibodies in indirect immunofluoresc ence tests, and on the restriction fragment length polymorphism of a p olymerase chain reaction (PCR)-amplified 56-kilodalton type-specific a ntigenic protein gene. By these methods, several antigenic and genotyp ic variants were found among the strains, and these variants were clas sified into types and further into subtypes. These results suggest tha t there are many variants in O. tsutsugamushi, and the methods used he re seem to be useful for the systematic classification of the numerous variants. A strain which may be a new type distinguishable from those identified previously was also found in this study, Furthermore, vari ety in the degree of pathogenicity in mice related to type and/or subt ype classification were observed.