CROSS-REACTIVITY OF RICKETTSIA-JAPONICA AND RICKETTSIA-TYPHI DEMONSTRATED BY IMMUNOFLUORESCENCE AND WESTERN IMMUNOBLOTTING

Cross-reactivity between Rickettsia japonica and R. typhi was observed by immunofluorescence tests using sera from patients with Oriental sp otted fever (OSF), from whom the causative agent was isolated and iden tified as R, japonica, Western immunoblotting with these sera revealed that only the 120-kilodalton surface polypeptide, i,e,, rickettsial o uter membrane protein (rOmp) B, has a common antigenicity with the 105 -kilodalton surface polypeptide of R. typhi, In some cases, antibodies specifically reactive with R. typhi were detected in acute-phase sera followed by a significant rise ire titers, possibly because of an ana mnestic response to a previous infection with an R. typhi-like agent; the sera retained reactivity to R. typhi even after absorption by a ho mologous strain, A lipopolysaccharide (LPS)-like antigen of R. typhi w as found to be reactive with some sera of OSF patients, The ladder ban ds on Western immunoblot of rickettsial organisms were confirmed to be polysaccharide in nature, which was demonstrated by comparing them wi th the pattern of silver-stained gel of proteinase K-treated rickettsi al specimens after sodium dodecyl sulfate-polyacrylamide gel electroph oresis.