Acquired immunity to human non-A, non-B hepatitis: cross-challenge of chimpanzees with three infectious human sera.

Chimpanzees that had recovered from non-A, non-B hepatitis transmitted by inoculation of serum from each of three chronically infected humans were challenged by inoculation with a second of the three infectious sera to determine whether recovery from infection caused by one serum afforded protection against later infection by another. None of the challenge inoculations caused recognizable non-A, non-B hepatitis in any of the chimpanzees, a finding suggesting that either one agent or several agents sharing a common or similar antigen were responsible for the original non-A, non-B hepatitis in fections in these chimpanzees. Although circumstantial evidence in the literature suggests the existence of more than one agent of non-A, non-B hepatitis, the fact that the three inocula were obtained from humans residing in different geographic areas of the eastern United States suggests that one agent or a group of related agents may be the cause of many cases of non-A, non-B hepatitis in the United States.