HLA-A31- and HLA-Aw68-restricted cytotoxic T cell responses to a single hepatitis B virus nucleocapsid epitope during acute viral hepatitis.

Abstract

SummaryWe have recently developed the technology to identify and characterize the human histocompatibility leukocyte antigen (HLA) class I-restricted, CD8 + cytotoxic T lymphocyte (CTL) response to hepatitis B virus (HBV)-encoded antigens in patients with acute viral hepatitis. CTL are expanded in vitro by stimulation with HBV-derived synthetic peptides and selected by restimulation with a panel of HLA-matched stable transfectants that express the corresponding HBV protein. We have recently reported the existence of an HLA-A2-restricted, CD8 + CTL response to an epitope located between residues 18 and 27 of the HBV nucleocapsid core antigen (HBcAg). We now report the discovery of a CTL epitope located between HBcAg residues 141 and 151 that completely overlaps a critical domain in the viral nucleocapsid protein that is essential for its nuclear localization and genome packaging functions as well as processing of the precore protein. The CTL response to this epitope is dually restricted by the HLA-A31 and HLA-Aw68 alleles, which, unexpectedly, appear to use a common binding motif based on the results of alanine substitution and competition analysis, and the binding properties of these two alleles predicted from their known primary sequence, and from the three-dimensional structure of HLA-Aw68. We have also demonstrated that the HBV-specific CTL response to this epitope is polyclonal during acute viral hepatitis, since these two restriction elements can present the HBcAg 141-151 epitope to independent CTL clones derived from a single patient; and that the CTL response is multispecific, since HLA-A2-restricted and HLA-Aw68-restricted CTL responses to HBcAg 18-27 and HBcAg 141-151, respectively, have been identified to coexist in another patient. The foregoing argue against the emergence of CTL escape mutants as a significant problem during HBV infection, especially at this locus, where mutations might be incompatible with viral replication. Finally, our data suggest an association between the HBV-specific CTL response and viral clearance, and they have implications for the design of immunotherapeutic strategies to terminate HBV infection in chronically infected patients.T he hepatitis B virus (HBV) 1 is a small hepatotropic enveloped virus with a double-stranded DNA genome (1) that causes acute and chronic necroinflammatory liver disease and hepatocellular carcinoma (2). The mechanisms responsible for viral clearance and liver cell injury in HBV infection are not well understood. Based on precedent in other viral 1 Abbreviations used in this paper: HBcAg, hepatitis B core antigen; HBV, hepatitis B virus. systems, and a limited analysis of the intrahepatic (3-5) and PBL (6) response to HBV-encoded antigens, it appears that HBV-specific helper and CTL responses may play an important pathogenetic role in this disease. Since the viral nucleocapsid protein is an important target of the CTL response to other viruses (7-11), we have begun to examine the HLA class I-restricted CTL response to the hepatitis B nucleocapsid c...

Altered antigenicity of 'a' determinant variants of hepatitis B virus.

“…The protection offered by immunity elicited by HBV vaccine, which is usually polyclonal in nature, may not be totally lost or severely affected in vivo by the substitution of only one amino acid. However, some individuals are known to have a more narrowly focused host immune response than others (Chisari & Ferrari, 1995 ;Missale et al, 1993 ;Penna et al, 1992). In these individuals, any loss of the limited responsive repertoire of the viral epitopes could accentuate the ability of the variant virus to evade the host immunity.…”

Viruses, Immunity, and Cancer: Lessons from Hepatitis B

“…This type of CTL response is unusual, however, during HBV infection, when the CTL response is typically vigorous and multispecific during acute hepatitis and weak or undetectable during chronic hepatitis. 42,65,66,72 Accordingly, mutational inactivation of CTL epitopes is extremely uncommon during chronic HBV infection. 73 Nonetheless, strong, narrowly focused CTL responses do occur occasionally in these patients, 20 and in this setting viral escape mutations can occur.…”

Purification and characterization of a naturally processed hepatitis B virus peptide recognized by CD8+ cytotoxic T lymphocytes.

“…There is considerable evidence suggesting that HBV is not directly cytopathic (3), and that the hepatitis is caused by immune responses against virus-infected hepatocytes (4). In vitro studies have shown that hepatitis B surface antigen (HBsAg)-and hepatitis B core antigen (HBcAg)-expressing transfectants can serve as targets for MHC class I-restricted cytotoxic T lymphocytes (CTLs) that are generated from both acute and chronic hepatitis B patients (5)(6)(7)(8)(9)(10)(11)(12). In addition, expression of HBcAg in the cytoplasm and on the membrane of liver cells is positively correlated with the hepatitis activity (13,14).…”