A nonhuman primate model of Rickettsia prowazekii infection

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Ricketisia prowazekii is the causative agent of epidemic typhus, a vector (louse)-borne disease characterized by a sudden onset of febrile symptoms with significant pathologic sequelae. In addition to causing epidemic disease in poor and unhygienic environments, R. prowazekii has also been identified as possessing the characteristics of a biological weapon. There presently is no vaccine available for protection against epidemic typhus, although development of new products is currently underway. A fully characterized primate model of disease is needed to determine immune response, safety, and protective efficacy of vaccine products developed to protect against R. prowazekii infection. The goal of this project is to develop a robust nonhuman model of disease for epidemic typhus in order to accelerate testing of newly developed vaccine products. The specific hypothesis is that use of the Rhesus macaque (Macaca mulatta) of Chinese origin will provide an optimal test system for an infection model of epidemic typhus. We base this hypothesis upon the observations from limited past studies that detailed 1) a clear doseresponse relationship in prior model development efforts with the Breinl strain using Rhesus macaques when directly compared to experimental infection with avirulent strains, and 2) typical pathology in the form of disseminated vasculitis including typhus nodules in the central nervous system that emulated the human clinical syndrome. Based on these observations, the experimental focus of this proposal is on the model development of epidemic typhus in the Rhesus macaque. Specific aims include: 1.) Reestablish a nonhuman primate model for intravenous R. prowazekii infection. This will reestablish the model in the context of immune and pathologic response for future nonhuman primate studies involving R. prowazekii infection. 2.) Develop an aerosol challenge model R. prowazekii challenge. Rickettsia prowazekii, in addition to causing epidemic disease, is considered a biological threat agent because of its low dose, aerosol infectivity and history of weaponization. The aerosol disease model will provide an optimal system for testing of products developed expressly for protective efficacy against potential mucosal challenge with R. prowazekii.