Augmented hepatic interferon gamma expression and T-cell influx characterize acute hepatitis progressing to recovery and residual lifelong virus persistence in experimental adult woodchuck hepatitis virus infection

Woodchucks infected with woodchuck hepatitis virus (WHV) have profiles of l iver disease and age-dependent rates of progression to chronic hepatitis (C H) comparable with those seen in human hepatitis B. The mechanism of recove ry from acute hepadnaviral infection or its evolution to chronicity remains unknown, although the liver immune responses are expected to play an impor tant role. To determine the dynamics of intrahepatic cytokine expression an d T-cell involvement, and to assess their value in predicting the outcome o f acute hepatitis (AH) in the adult onset of WHV infection, we evaluated li ver transcription of interferon gamma (IFN-gamma); tumor necrosis factor a (TNF-alpha); interleukins (IL)-2, -4, and -6; and the T-cell influx in rela tion to disease histologic severity and virus load in serial liver biopsies collected during the life span of experimentally infected woodchucks. Our results show that recovery from viral AH in adulthood is preceded by a sign ificantly greater hepatic expression of IFN-gamma and CD3, an increased TNF -alpha transcription, lower hepatic WHV load, and a greater degree of liver inflammation than those in acute infection with CH outcome. Furthermore, w e have learned that the elevated IFN-gamma, TNF-alpha, and CD3 expression i n the liver endures for years not only in CH, but also, although to a lesse r extent, in apparently completely resolved infection. This is consistent w ith our previous findings that residual WHV replication and remnant liver i nflammation continue for life after recovery from AH. This study indicates that antiviral cytokines, in particular IFN-gamma, may play a central role in the long-term control of occult hepadnavirus persistence in the liver.