Immunological Studies of Rickettsia Complement-fixation Test of Rickettsia orientalis Using the Antigen Treated with Sodium Deoxycholate

Abstract

omplement-fixation tests of R. orientalis were performed by the use of antigens treated 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 of 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 Karp strain.
In the homologous system of the tests, complement-fixing antibodies of mice infected with R. orientalis began to appear on the 15th day after the infection, rose rapidly in a few days, and reached its maximum in 4-6 weeks after the infection and 8 weeks at latest. Subsequently, the titers declined gradually and showed low titers on the 52nd week after the infection in spite of lives of rickettsia in mice. In the heterologous system, of which antigenic structures were different each other, the titers rose somewhat later and disappeared earlier than those in the homologous system.
It was confirmed that the antigen treated with sodium deoxycholate was utilizable in the specific serological diagnosis of scrub typhus, because convalesceut sera from all four patients with the disease showed significant rise of complement-fixing titers against the antigen.