Viruslike particles in a plasma fraction (fibrinogen) and in the circulation of apparently healthy blood donors capable of inducing non-A/non-B hepatitis in humans and chimpanzees.

Two patients who had received a fibrinogen preparation contracted hepatitis of non-A/non-B etiology 3 and 8 wk after the injection. A chimpanzee inoculated with the same preparation developed hepatitis 11 wk later, with an increase in SGPT and a liver pathology compatible with acute viral hepatitis. His preacute serum containing the presumptive etiologic agent induced hepatitis in another chimpanzee. Electron microscopic observation of the liver of these chimpanzees biopsied during preacute and acute stages revealed peculiar tubular structures composed of two unit membranes with electron-opaque material in between. Using the serum obtained from infected chimpanzees at convalescence as an antibody reagent, viruslike particles were identified in the fibrinogen preparation by immune electron microscopy. When the serum of 100 apparently healthy blood donors with SGPT value of 80 Karmen units/ml or higher was tested for viruslike particles, eight were found to be positive. Furthermore, one of these sera, when a 5-ml amount was injected into each of two chimpanzees, induced hepatitis with viruslike particles in the circulation and characteristic tubular changes in the liver. On the basis of the results obtained, the viruslike particles in the fibrinogen preparation, as well as in the circulation of apparently healthy donors, were capable of inducing hepatitis of non-A/non-B category with a liver pathology characterized by tubular structures. The detection of non-A/non-B viral particles, especially when refined to routine laboratory tests, may open the way for the specific diagnosis, exclusion of contaminated blood from transfusion, and eventual prophylaxis by vaccination.