Inactivation of an agent of human non-A, non-B hepatitis by formalin.

Samples of serum (0.1 ml each) containing an agent of human non-A, non-B hepatitis of documented infectivity were incubated with formalin in a concentration of 1:1,000 at 37 C for 96 hr. Three colony-born infant chimpanzees were then inoculated with this formalin-treated serum; one received a single intravenous inoculation, and two received two subcutaneous inoculations one month apart. A fourth uninoculated chimpanzee served as a control. None developed recognizable non-A, non-B hepatitis during seven months of observation, as judged by normal aminotransferase levels in weekly serum samples, normal liver histology in liver biopsy specimens, and the absence of non-A, non-B hepatitis-associated antigen and antibody in their sera. All four chimpanzees were subsequently shown to be susceptible to non-A, non-B hepatitis when challenged with 0.1 ml of the untreated infectious serum 31 weeks after the initial inoculations.