Katayama strain was isolated as the causative agent from a patient with spotted fever group rickettsiosis by using nude mice in Anan-city, Tokushima, Japan, in October, 1987. The nude mice infected with the isolate showed weakness and splenomegaly and died in two or three weeks after the infection. The majority of infected normal mice recovered and acquired immunity. The Katayama strain was propagated well in BSC-1 cells and L cells. The fluorescent antibody-stained rickettsial particles were seen as diplobacillaly and diplococcal forms growing in both the cytoplasm and the nucleus of infected cells.
The indirect fluorescent antibody test using Katayama strain, R. sibirica 246 strain and Thai tick typhus TT-118 strain as antigens revealed that the specific antibodies against these antigens appeared and increased in the blood of the patient during the course of disease. And the antibody titers to the Katayama antigen were the highest of these three antigens. Agglutinin for Proteus OX-2 also appeared in the blood of the patient.
The cross-immunofluorescent antibody test using Katayama, 246 and TT-118 strains as antigens and immune mouse sera against the three strains as antisera revealed that these strains showed cross-reaction and have a common antigen. Furthermore, it became obvious that the Katayama strain has the strain-specific antigen (s) different from the 246 strain and the TT-118 strain by using Anti-Katayama monoclonal antibodies which were produced by cell fusion techniques.