Rickettsial Diseases: Scrub Typhus and Trench Fever.

This study is directed towards the isolation of rickettsial antigens and detection of antibodies. Stock supplies of Gilliam, Kato and Karp strains of Rickettsia tsutsugamushi were propagated in embryonated chick eggs and used for infecting cultured cells. Infected McCoy cell extracts containing soluble antigen as well as infected yolk sacs were inoculated into guinea pigs to produce antisera. However the yield of antibody was low and only detectable by fluorescent antibody techniques. More recently progress was made in growing R. tsutsugamushi in BHK 21 cells as a monolayer or in suspension cultures. An enzyme immunoassay test to detect antibodies to Rochalimeae quintana in sera from patients with trench fever was evaluated with soluble antigens. This test detected antibodies in sera from known cases that were negative to other serological tests. However, there is an antigen that cross reacts with other rickettsia which appears to be a lipopolysaccharide antigen. This lipopolysaccharide seems to be related serologically to scrub typhus antigen. Infected cells as well as isolated samples used in the studies were fixed and examined by electron microscopy to monitor the structure of the organism and the host cell as well as some of the isolated and purified samples.