Complement-Fixation Tests of Rickettsia orientalis with Sodium Deoxycholate Treated Antigen

Abstract

Complement-fixation tests of Rickettsia orientalis were performed by using antigens purified with sodium deoxycholate. Cross complement-fixation tests between antigens of the Gilliam, Ohzeki, Karp and Kato strains and immune mouse sera of these four strains and of the Kaneko strain revealed difference in antigenic structure among the Gilliam, Karp and Kato strains. The Ohzeki strain was identical with the Gilliam strain and the Kaneko strain was identical with the Karp strain. In the homologous system, complement-fixing antibodies of mice infected with R. orientalis began to appear on the 15th day after infection and rose rapidly in a few days, and reached maximum in 4-6 weeks after infection and 8 weeks at latest. Subsequently, the titers declined gradually and showed low titers on the 52nd week in spite of survival of rickettsia in mice. In the heterologous system among which antigenic structures were different, the titers rose somewhat later and declined earlier than those of the homologous system. It was confirmed that the antigen treated with sodium deoxycholate was utilizable in the specific serological diagnosis of scrub typhus, because convalescent sera from all ten patients with the disease showed significant rise of complement-fixing titers against the antigen.