Purification of complement-fixing antigens of Rickettsia sennetsu by ether treatment

Soluble and particulate complement-fixing antigens of Rickettsia sennetsu were prepared from spleen suspensions of mice infected with the rickettsia and treated with cyclophosphamide. The medium used during purification of antigens, a solution consisting of equal volumes of phosphate-glutamate-sucrose buffer and veronal-buffered saline, was suitable for obtaining antigens with high titers and no anti-complementary activity. By heat treatment, it was demonstrated that the soluble antigen was heat labile and the particulate antigen was heat stable. The soluble antigen was precipitated by 80% saturation with ammonium sulfate. Cross-complement fixation tests using both soluble and particulate antigens revealed that there was no antigenic difference among strains of R. Sennetsu. On the other hand, no cross-activity was observed between R. sennetsu and R. orientalis.