PURIFICATION AND CHARACTERIZATION OF A NATURALLY PROCESSED HEPATITIS-B VIRUS PEPTIDE RECOGNIZED BY CD8(-LYMPHOCYTES() CYTOTOXIC T)

In vitro studies in patients with hepatitis B virus (HBV) infection ha ve suggested that hepatocytolysis induced by CD8i cytotoxic T lymphocy tes (CTLs) is the most important effector pathway in eliminating infec ted cells. The recognition is implicated in the endogenously processed HBV antigens in the context of HLA class I molecules presented on the liver cell membrane. However, the naturally occurring HBV peptide ant igens have not yet been demonstrated. We report here that a naturally processed peptide antigen P2 was isolated from HLA class I molecules o f HBV-infected liver cell membrane. The P2 peptide exhibited the activ ity of sensitizing target cells for lysis by CD8(+) CTLs. The P2 seque nce (YVNVNMGLK) purified from liver tissue was in concordance with tha t encoded by the viral genome for the HBV nucleocapsid antigen or HBcA g 88-96. P2 peptide could also be isolated from the EBV-transformed B cells that were transfected by HBcAg-expressing vector. The P2 epitope , sharing the HLA-A11 binding motifs, was recognized by HLA-All-restri cted CD8(+) CTLs. The data provided direct evidence that, in hepatitis B patients, antigenic peptides of HBV were processed by hepatocytes, presented with the class I MHC molecules, and recognized by CD8(+) CTL s.