Characterization of the incorporation of woodchuck hepatitis virus surface antigen into hepatocyte plasma membrane in woodchuck hepatitis and in the virus-induced hepatocellular carcinoma

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Abstract
Interaction between woodchuck hepatitis virus surface antigen and proteins of hepatocyte plasma membranes were examined in the course of woodchuck hepatitis virus infection. Membranes purified from animals with histologically confirmed acute hepatitis, active or persistent chronic hepatitis and the virus-related hepatocellular carcinoma were evaluated for the virus surface antigen contents, treated with agents eluting plasma membrane-bound antigen to test the extent of the antigen-membrane associations and incubated with purified, particulate woodchuck hepatitis virus surface antigen to determine membrane potential for the antigen adsorption. Hepatocyte plasma membranes originating from woodchucks chronically infected with the virus showed the highest quantities of the incorporated virus surface antigen among membranes studied, the behavior of bound antigen as an integral and a peripheral membrane protein and the resistance to bind an exogenous antigen. Similar properties were expressed by plasma membranes prepared from hepatocytes of nontumor parenchyma displaying chronic active hepatitis of a woodchuck hepatitis virus carrier with hepatoma. Furthermore, plasma membranes originating from animals with active or persistent chronic hepatitis demonstrated identical properties, implicating that histologic activity of the chronic liver inflammatory process is not dependent on the quantity of the virus surface antigen insertion into the membrane. In contrast, hepatocyte plasma membranes from animals with acute hepatitis showed significantly lower antigen quantities, presence of the antigen specificity exclusively behaving as an integral membrane protein and noticeable ability to bind an exogenous surface antigen of the virus. Comparable, but not identical, features were observed for hepatocyte membranes purified from nodules of hepatocellular carcinoma, suggesting that neoplastic transformation of infected hepatocytes is associated with loss of the membrane-bound antigen and with simultaneous, partial recovery of the membrane potential for the antigen binding. Comparative analysis of the properties on the woodchuck hepatitis virus surface antigen incorporation into hepatocyte plasma membranes in studied cases indicated that sustained infection with woodchuck hepatitis virus leads to an increase in the quantity of the membrane-incorporated antigen and to the appearance of the virus surface antigen specificity behaving as a peripheral membrane protein. In conclusion, this study demonstrated that the extent and the character of the antigen interaction with hepatocyte plasma membranes undergoes significant variations in the natural course of hepadna viral infection in woodchucks and that histologically distinct forms of the virus-induced liver disease express specific properties on the association.