Novel and frequent mutations of hepatitis B virus coincide with a major histocompatibility complex class I-restricted T-cell epitope of the surface antigen

Abstract

We examined the full-length hepatitis B virus (HBV) envelope (surface antigen or HBV small surface antigen [HBsAg]) sequences of 12 different liver samples from 10 different hepatoma-containing chronic carriers. Surprisingly, novel and frequent mutations occurred predominantly at amino acids 40 and 47 of HBsAg, in addition to within a known protective B-cell epitope (so-called group a determinant of HBsAg 124-148). Approximately 58% of chronic carriers contain mutations at the group a determinant. The mutation frequency at the hotspot codons 40 and 47 is approximately 83%, 1 order of magnitude higher than at the known polymorphic sites of subtype-specific determinants at codons 122 and 160, which is approximately 4%. This new mutational domain is found to coincide with a major histocompatibility complex class I-restricted T-cell epitope. The potential biological significance of this novel mutation in the immunopathogenesis of HBV chronic carriers is discussed.

Characterization of the reactivity pattern of murine monoclonal antibodies against wild-type hepatitis B surface antigen to g145r and other naturally occurring “a” loop escape mutations

“…A DNA fragment of 900 bp corresponding to middle HBsAg, subtype ayw3, was used for the construction of several point-mutated DNA sequences with primer site-directed mutagenesis ( Table 1). We obtained single and double point-mutated HBsAg proteins with the following aa replacements (Table 1): R122K, A128V, Q129R, G130N, M133T, Q129R and M133T, Y134F, S136Y, K141W, D144H, G145R, G145A, Q129R and G145A, Q129R and G145R, T148A, S154E, K160R (5,10,12,(15)(16)(17)22,23,25,26,30,31,(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46); EMBL Data Library accession nos. S41870 and S36654).…”

“…3 This highly conformational structure consists of two loops held by disulfide bridges (cysteines 124-137 and 138-147 or 149) projecting from the viral surface. [3][4][5][6][7] Immunoreactivity depends on spatial arrangements of distinct peptide regions and has been analyzed by competitive binding assays and with synthetic peptides. 8 Antibodies to the ''a'' determinant are thought to confer protection against the major HBV subtypes (adr, adw, ayr, ayw) and are pivotal for HBV clearance, whereas subtypespecific antibodies were not found to be neutralizing.…”

“…14 They facilitate viral persis-tence and compromise anti-HBs-mediated immunoprotection. Nucleotide point mutations causing various amino acid replacements within the ''a'' loop have been identified in chronic carriers and among fully vaccinated subjects, 5,[15][16][17][18][19][20][21][22] and during prophylaxis of recurrent HBV infection with high-dose HBIg in liver-transplant recipients. [23][24][25][26][27] An increase of breakthrough HBV infections during HBIg therapy associated with increased use of recombinant versus plasma-derived antigen to generate HBIg was reported recently.…”

Quasispecies and its impact on viral hepatitis

“…The analyses suggest selection of immune-escape HBV variants during some chronic HBV infections, and constitute an example of biologically relevant coexistence of phenotypic variants in the same host individuals (Table 1). Chronically infected patients often include substitutions at CTL epitopes of HBV (Tai et al, 1997).…”

The population genomics of hepatitis B virus

“…It is current practice to use genotypes as proxies for the genetic make-up of different strains. Several studies using such an approach have suggested that HBV genotypes influence the outcome of the infection or of drug therapies but their results are partially conflicting (Tai et al 1997;Torre & Naoumov 1998;Tsubota et al 1998;Mayerat et al 1999;Ding et al 2002;Kidd-Ljunggren et al 2002;Liu et al 2002;Jazayeri et al 2004;Schaefer 2005). Cryptic population structure within genotypes may explain the difficulty of the genotype classification to capture the true population structure of HBV, which would lead to such discrepancies.…”