SERIAL ANALYSIS OF HEPATITIS-B VIRUS CORE NUCLEOTIDE-SEQUENCE OF PATIENTS WITH ACUTE EXACERBATION DURING CHRONIC INFECTION

Recent studies suggest that hepatitis B virus (HBV) core region could be an immunological target and that amino acid (aa) substitutions are mostly restricted to a small segment located in the middle of the core region. We sequenced the middle portion of HBV core gene during the c ourse of acute exacerbation of chronic hepatitis B, and compared aa va riations between the region including ideal HLA-A2 binding motifs and the nonbinding region. Five HBeAg+ chronic hepatitis patients with sub type adr (three with HLA-A2 and two without HLA-A2) were selected and using polymerase chain reaction (PCR) and cloning system, the central part of core region (nt 2063 to 2365, 303 bp) was sequenced in sera fr om each patient at three time points; before, at the peak of, and afte r exacerbation of hepatitis. The second set of sera showed higher aa s ubstitution rates in five and in three out of five patients compared w ith those of the first and third sera, respectively. No significant di fference was found in the aa substitution rates for the region with id eal HLA-A2 binding motifs between patients with and without HLA-A2. In asymptomatic HBV carriers with persistently normal aminotransferase v alues, alterations of the aa sequence were not observed within the sam e time frame. The results suggest that aa substitutions often occur at some particular positions in the middle of HBV core region during acu te exacerbation of the disease under possible host immune pressures. F urthermore, unidentified epitopes appear to exist in the central part of HBV core region and HLA-unrestricted lymphocytes may play a role in the immune response of chronic HBV carriers. (C) 1996 Wiley-Liss, Inc .