Fluorescent Antibody Methods in the Differentiation of Murine and Epidemic Typhus Sera; Specificity Changes Resulting from Previous Immunization

Summary A method is described for the staining of typhus rickettsiae with fluorescent antibody. Convalescent human or guinea pig sera are used in an indirect or in a complement staining procedure. Fluorescent antibody procedures are readily adapted to antibody absorption (or inhibition) techniques, and advantage is taken of this fact to differentiate murine from epidemic typhus sera. A group of sera from human beings and guinea pigs convalescent from murine or epidemic typhus fever gave results with the expected specificity, but three of 14 presumed murine typhus sera from humans had indeterminate specificity or specificity directed toward epidemic typhus rickettsiae. Two instances were observed of laboratory personnel who received epidemic typhus vaccine and subsequently were accidentally infected with murine typhus rickettsiae. In both cases the antibody formed during infection had specificity directed toward epidemic rickettsiae. Guinea pigs were given epidemic or murine typhus vaccines and then infected with murine or epidemic typhus rickettsiae. As a result of infection the homologously challenged animals formed antibody characteristic of the infecting rickettsia, but many of those receiving heterologous challenge formed antibody characteristic of the vaccine.