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The pre-S2-coding region in the hepatitis B virus surface antigen M (P31; pre-S2 + S) protein gene was modified to identify a polymerized-albumin receptor (PAR) domain by deleting restriction fragments or performing site-directed mutagenesis. The modified M protein genes (M-P31x; x = d, e, f, h and i) were cloned into the yeast generalized-expression vector pGLD 906-1 and expressed in Saccharomyces cerevisiae under the control of yeast glyceraldehyde-3-phosphate dehydrogenase gene promoter. The PAR activities of these gene products suggested that the PAR domain is located in the hydrophilic and highly conserved domain in the pre-S2 region (around Leu12 approximately Tyr21). Antibodies specific for a pre-S2 peptide (Phe8 approximately Pro34, subtype adr), which covers the PAR domain, were purified from sera of rabbits immunized with yeast-derived M protein particles having a natural PAR domain. Immune electron microscopy showed that the purified antibodies could aggregate HBV particles. Therefore, it was speculated that the PAR domain overlapped with the dominant virus-neutralizing and virus-protecting epitopes.

To investigate mechanisms of hepatocyte injury, lymphocytes from 41 children with chronic liver disease were incubated with autologous liver cells in a microcytotoxicity assay. Cytotoxicity was significantly increased in 18 of 25 patients with chronic hepatitis B virus (HBV) infection, in five of nine with "autoimmune" chronic active hepatitis (CAH), and in only one of seven with histologically inactive liver disorders. There was a good correlation between cytotoxicity and biochemical and histologic markers of disease activity in children with autoimmune CAH, whereas in HBsAg-positive disease a positive correlation was found only with serum alanine aminotransferase (SGPT). Children with autoimmune CAH receiving steroid treatment had normal cytotoxicity, whereas increased values were found in two of three HBsAg-positive patients receiving prednisolone. Fractionation studies revealed that non-T cells were cytotoxic in both autoimmune and HBcAg-positive chronic liver disease. T cell cytotoxicity was exclusively found in children with chronic HBV infection, particularly with HBc antigenemia. Blocking experiments showed that T-lymphocytes from HBsAg-positive children reacted with HBV core antigen on the hepatocyte surface. Non-T cells were directed against hepatocyte membrane antigens in both HBsAg-positive and HbsAg-negative children. These results suggest that different immune mechanisms of liver damage are involved in autoimmune and HBsAg-positive chronic liver disease.

A commercial radioimmunoassay was adapted to detect serum Dane particle-associated HBeAg in patients whose sera contained homologous antibody. HBeAg was released from Dane particles with guanidine HCl. Dane particles were separated from anti-HBe by gel-filtration (Sepharose 4B) and ultracentrifugation of the eluate. Dane particle-HBeAg was tested in 45 HBsAg carriers with anti-HBe and was present in 8 (18%) carriers, all of whom had chronic liver disease. By contrast, HBeAg was not found in 10 carriers with normal liver histology. Serum or liver HBcAg was found in 6 of 8 patients with Dane particle-HBeAg. None of the carriers without Dane particle-HBeAg had other markers of hepatitis B virion synthesis. We conclude that Dane particle-HBeAg provides a sensitive index of active hepatitis B virus replication, a guide to the presence of chronic hepatitis in HBsAg carriers with anti-HBe, and a noninvasive method to follow infection in these patients.

BALB/c mice receiving antiidiotype antibodies before the injection of hepatitis B surface antigen (HBsAg) generated an enhanced anti-HBs response. Mice given antiidiotype antibodies in a soluble form induced predominantly IgM anti-HBs, whereas alum-precipitated antiidiotype produced primarily IgG anti-HBs. Injection of antiidiotype antibodies alone induced anti-HBs that inhibited a common interspecies anti-HBs idiotype-antiidiotype reaction and recognized the group-specific determinant of HBsAg. These data support the view that antiidiotype antibodies may modulate the immune response to an infectious viral agent.