In vitro production of infectious woodchuck hepatitis virus by lipopolysaccharide-stimulated peripheral blood lymphocytes.

Peripheral blood lymphocytes (PBLs) from a wild-caught woodchuck (WC192) chronically infected with woodchuck hepatitis virus (WHV) carried low levels of nonreplicating WHV genomes. In a previous study, these WHV genomes were induced to replicate and intact WHV particles were released when these PBLs were cultured in the presence of the generalized mitogen, lipopolysaccharide (LPS). To determine whether the culture-derived WHV particles were infectious, adult woodchucks were inoculated with cell-free culture medium from either LPS-stimulated or unstimulated WC192 PBLs. None of three animals inoculated with medium from the unstimulated PBL cultures developed positive WHV serologic markers or elevated liver enzyme levels during a 42-w observation period. In contrast, all three animals that received medium from the LPS-stimulated cultures displayed serologic markers of acute WHV infections 8-10 w after inoculation at up to a 100-fold dilution of the original culture medium. One of the three infected animals developed an acute hepatitis coincident with the appearance of the WHV markers. These results demonstrate that the WHV particles released from LPS-stimulated WC192 PBLs in culture are mature, infectious virions that also cause liver disease. Thus the LPS-induced replication of WHV in these cell cultures represents a transition from a latent to productive viral infection.