The agents of non-A, non-B viral hepatitis.

Recent studies have provided physicochemical and electron microscopic evidence for the existence of two distinct agents of posttransfusion non-A, non-B (NANB) hepatitis. One of these agents is chloroform-resistant and is not associated with the formation of unique ultrastructural structures in infected liver. The other agent is CHCl3-sensitive, induces the formation of characteristic hepatocyte cytoplasmic tubules, and interferes with concurrent HAV or HBV infection in experimentally inoculated chimpanzees. The tubuleforming agent (TFA) has also been shown to pass through an 80 nm capillary pore membrane filter, suggesting that it is a small enveloped (or lipid-containing) virus. The TFA can also be recovered from low titer (less than or equal to 10(5) infectious doses/ml) chronic-phase chimpanzee plasma by use of a multi-step purification procedure that assumes the agent is a small enveloped RNA virus with an approximate buoyant density of 1.24 g/cm3 and a sedimentation coefficient of 200-280 S. The apparent lack of nucleic acid homology between the NANB-TFA and HBV further suggests that the NANB-TFA is either Togavirus-like or belongs to another or as yet undefined class of RNA or DNA virus.