[Antigenic types of Rickettsia tsutsugamushi isolated from patients with tsutsugamushi fever and their distribution in Miyazaki Prefecture]

Abstract

Rickettsia tsutsugamushi (Rt) isolated from patients with tsutsugamushi fever were examined for their antigenicity. This was done by indirect immunofluorescence (IIF) with guinea pig antisera against three standard strains (Karp, Kato and Gilliam) and two local strains (Kawasaki and Kuroki) isolated in 1981, and with mouse monoclonal antibodies against the three standard strains. In the meantime, antibodies in sera from 317 out of 442 patients registered during 1985 to 1988 were titrated by IIF with those five Rt strains. 1) Local isolates, Kawasaki and Kuroki strains, reacted most effectively with the homologous antiserum, respectively, showing four fold lower IIF titers against the heterologous antisera. 2) Kawasaki strain reacted with none of the monoclonal antibodies, whereas Kuroki strain showed a slight reaction with anti-Karp and anti-Kato, but not anti-Gilliam, monoclonal antibodies. 3) Seventeen out of 27 strains isolated in 1985 resembled the Kawasaki strain in their reaction patterns with the antisera and monoclonal antibodies, and the other 10 strains showed reactivity similar to the Kuroki strain. 4) Sera of 233 (74%) out of 317 patients showed the highest antibody titers against the Kawasaki strain and 69 (22%) of 317 against the Kuroki strain. It is thus evident that Kawasaki and Kuroki strains are antigenically different from the standard strains, and Kawasaki and Kuroki strains also differ from each other. It is suggested that two antigenic types (Kawasaki and Kuroki) of Rt were distributed in Miyazaki Prefecture, Rt of the Kawasaki type slightly dominates Rt of the Kuroki type, and recent tsutsugamushi fever has been caused by either one or the other type of Rt.