Immunohistochemical diagnosis of typhus rickettsioses using an anti-lipopolysaccharide monoclonal antibody.

A monoclonal antibody directed against an epitope on the lipopolysaccharide of typhus-group rickettsiae was developed for the purpose of detecting this heat-stable, proteinase-resistant antigen in formalin-fixed, paraffin-embedded tissues. Rickettsia prowazekii organisms were identified in endothelium and macrophages in sections of the brains of three Egyptian men who died of epidemic louse-borne typhus in Cairo during World War II and in the brain from a recent case of typhus fever acquired in Burundi. R. typhi organisms were identified in endothelial cells from a fatal case of murine typhus and in experimentally infected mice. This approach is applicable not only to the study of archival tissues and experimental animal models but also could be used to establish a timely diagnosis of typhus-group rickettsiosis by immunohistochemical examination of cutaneous biopsies of rash lesions during the acute stage of illness.