Characterization of Novel Hepatitis B Virus PreS/S-Gene Mutations in a Patient with Occult Hepatitis B Virus Infection

Objective The impact of hepatitis B virus (HBV) preS/S-gene mutations on occult HBV infection (OBI) is not fully understood. This study characterized multiple novel HBV preS/S-gene mutants obtained from an OBI patient. Methods PreS/S-gene mutants were analyzed by clonal sequencing. Viral replication and expression were analyzed by transfecting HBV genomic recombinants into HepG2 cells. Results Twenty-one preS/S-gene mutants were cloned from four sequential serum samples, including 13 mutants that were not previously documented: (1) sI/T126V+sG145R; (2) preS1 nt 3014-3198 deletion; (3) preS1 nt 3046-3177 deletion; (4) preS1 nt 3046-3177 deletion+s115-116 "INGTST" insertion; (5) preS1 nt 3046-3177 deletion+s115-116 "INGTST" insertion+sG145R; (6) preS1 nt 3115-3123 deletion+sQ129N; (7) preS1 nt 3115-3123 deletion+s126-127 "RPCMNCTI" insertion; (8) s115-116 "INGTST" insertion; (9) s115-116 "INGTST" insertion+sG145R; (10) s126-127 "RPCMNCTI" insertion; (11) preS1 nt 2848-2862 deletion+preS2 initiation codon M -> I; (12) s122-123 "KSTGLCK" insertion+sQ129N; and (13) preS2 initiation codon M -> I+s131-133TSM -> NST. The proportion of preS1 nt 3046-3177 deletion and preS2 initiation codon M -> I+s131-133TSM -> NST mutants increased in the viral pool with prolonged disease. The 13 novel OBI-related mutants showed a 51.2-99.9% decrease in HBsAg levels compared with that of the wild type. Additional N-glycosylation-associated mutations, sQ129N and s131-133TSM -> NST, but not s126-127 "RPCMNCTI," greatly attenuated anti-HBs binding to HBsAg. Compared with the wild type, replication and surface antigen promoter II activity of the preS1 nt 3046-3177 deletion mutant decreased by 43.3% and 97.0%, respectively. Conclusion PreS/S-gene mutations may play coordinated roles in the presentation of OBI and might be associated with disease progression. This has implications for HBV diagnosis and vaccine improvement.