Diagnostic Antigens for Epidemic Typhus, Murine Typhus and Rocky Mountain Spotted Fever

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Abstract
Summary: Epidemic typhus and murine typhus vaccines prepared from infected yolk-sacs by ether-extraction process give nonspecific reactions in complement-fixation tests with Wassermann-positive human syphilitic sera if the technic of fixation for 18 hours at icebox temperature is used. Purified and concentrated soluble antigens were prepared from epidemic typhus, murine typhus and Rocky Mountain spotted fever vaccines by further treating the ether-extracted preparations with benzene followed by precipitation with sodium sulfate. The purified soluble antigens gave little or no reaction with human syphilitic sera using complement-fixation at icebox temperature. Complement-fixation tests with the purified and concentrated soluble antigens clearly differentiate cases of epidemic and murine typhus from Rocky Mountain spotted fever and will often, but not always, distinguish between epidemic and murine typhus cases.