Characteristics of amino acid substitutions within the “a” determinant region of hepatitis B virus in chronically infected patients with coexisting HBsAg and anti-HBs

In a search for monoclonal antibodies (MAbs) that can bind hepatitis B virus surface antigen (HBsAg) with amino acid substitutions in the immune dominant ‘a’ region (escape mutants) we investigated the epitope recognition site of the human MAb 4-7B. Pepscan analysis and experiments with alanine substitution as well as substitutions known from nature pointed to residues 178–186 in the small S protein with the amino acid sequence PFVQWFVGL (key amino acids in bold) as the minimal epitope. Single amino acid substitutions at positions 122(R/K)(d/y), 134(Y/F), 145(G/R), 148(T/A) and 160(K/R)(w/r), representing ‘a’ region variants in recombinant HBsAg COS-I cells, did not influence binding of MAb 4-7B. Synthetic peptides (residues 175–189) including the 4-7B epitope sequence were able to evoke an anti-HBs response in rabbits. According to established polypeptide models, the 4-7B epitope region is located in the lipid layer of 20 nm HBsAg particles. The present results, however, suggest that residues 178–186 are exposed on the surface of the 20 nm particle. This may change our view of the structure of HBsAg.

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Dynamics of Hepatitis B Virus Resistance to Lamivudine

Journal of Virology ◽

10.1128/jvi.80.2.643-653.2006 ◽

2006 ◽

Vol 80 (2) ◽

pp. 643-653 ◽

Cited By ~ 69

Author(s):

Coralie Pallier ◽

Laurent Castéra ◽

Alexandre Soulier ◽

Christophe Hézode ◽

Patrice Nordmann ◽

...

Keyword(s):

Amino Acid ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Individual Treatment ◽

Amino Acid Substitutions ◽

Treatment Optimization ◽

Lamivudine Resistance ◽

Resistant Variant ◽

B Virus

ABSTRACT Lamivudine was the first approved inhibitor of hepatitis B virus (HBV) reverse transcriptase (RT). Lamivudine resistance develops in 53% to 76% of patients after 3 years of treatment. We extensively characterized the dynamics of HBV quasispecies variant populations in four HBV-infected patients who developed lamivudine resistance. Virological breakthrough was preceded by 2 to 4 months by the emergence of quasispecies variants bearing amino acid substitutions at RT position 204, i.e., within the YMDD catalytic motif (rtM204V/I). Three patients had a gradual switch from a YMDD variant population at baseline to a 100% lamivudine-resistant variant population, whereas the remaining patient had a fluctuating pattern of resistance variant dynamics. Careful analysis of amino acid substitutions located outside domain C of HBV RT, including those known to partially restore replication capacities in vitro, showed that the in vivo replication of HBV variants is driven by multiple forces, including intrinsic replicative advantages conferred by mutations accumulating outside domain C and the changing environment in which these variants replicate. Our findings also suggest that individual treatment optimization will require sensitive methods capable of detecting the emergence of viral resistance before the relevant variants acquire optimal replicative capacities.

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