Cross‐Reactivity of Rickettsia japonica and Rickettsia typhi Demonstrated by Immunofluorescence and Western Immunoblotting

Abstract

Cross-reactivity between Rickettsia japonica and R. typhi was observed by immunofluorescence tests using sera from patients with Oriental spotted fever (OSF), from whom the causative agent was isolated and identified as R. japonica. Western immunoblotting with these sera revealed that only the 120-kilodalton surface polypeptide, i.e., rickettsial outer 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 in titers, possibly because of an anamnestic response to a previous infection with an R. typhi-like agent; the sera retained reactivity to R. typhi even after absorption by a homologous strain. A lipopolysaccharide (LPS)-like antigen of R. typhi was found to be reactive with some sera of OSF patients. The ladder bands on Western immunoblot of rickettsial organisms were confirmed to be polysaccharide in nature, which was demonstrated by comparing them with the pattern of silver-stained gel of proteinase K-treated rickettsial specimens after sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Murine Typhus from Vietnam, Imported into Japan

“…As expected from the group-specific nature of rickettsial LPS, no reaction was demonstrated to LPS of SFG rickettsiae, R. japonica and R. conorii , although weak reactivity, mainly to the major outer member protein of SFG rickettiae, rOmpB, and molecules of smaller sizes was shown ( 6 , 7 ). As described previously, rOmpB has cross-reactive antigenicity between TG and SFG rickettsiae ( 6 ). Compared with the trace reaction to rOmpB of SFG rickettsiae, an extremely high level of reaction was demonstrated to rOmpB of TG rickettsiae.…”

“…To demonstrate more detailed antigenic reactivity, Western immunoblotting was performed with serum on day 14 ( 6 ). The serum reacted similarly to the ladderlike lipopolysaccharide (LPS) of R. typhi and R. prowazekii .…”

Demonstration of a Heat‐Stable 120‐Kilodalton Protein of Rickettsia japonica as a Spotted Fever Group‐Common Antigen

“…Gilmore et al (7) proposed the designation of rOmp A and rOmp B for major rickettsial outer membrane proteins. It was shown that the rOmp B or heat-modifiable 120-kDa polypeptides of R. rickettsii and R. japonica share common epitope(s) with the 105-kDa polypeptide of typhus group (TG) rickettsiae (7,25). Furthermore, the recombinant rOmp B was immunologically cross-reactive with TG rickettsiae (7,8).…”

Spotted Fever Group and Typhus Group Rickettsioses in Humans, South Korea

“…Sera from patients with SFG rickettsiosis have been reported to react with TG rickettsiae by using serologic analysis methods ( 15 ). The serum specimens from patients with TG rickettsiosis were also demonstrated to contain cross-reactive antibodies against SFG rickettsiae ( 15 , 16 ). In a previous study, approximately one third of specimens seropositive for antibodies against SFG rickettsiae had antibodies against TG rickettsiae (unpub.…”