Substitutions of rtL228 and/or L229 are involved in the regulation of replication and HBsAg secretion in hepatitis B virus, and do not affect susceptibility to nucleos(t)ide analogs

Nucleos(t)ide analogs (NAs) are widely used in the treatment of hepatitis B virus (HBV) and human immunodeficiency virus (HIV). The mutation L210W of HIV-1 reverse transcriptase (RT) is one of the six principal mutations which confer in vivo resistance to zidovudine. Due to the similar 3D-structure and high conservation between HIV-RT and HBV-RT, the present study aimed to clarify whether corresponding mutations in HBV may decrease its susceptibility to relevant NAs. Mutations including rtL228C/W, rtL229W and rtL228W/L229W were introduced into a HBV replication competent plasmid by fusion polymerase chain reaction. Replication capacity, HBs/e antigen (Ag) levels and susceptibility to NAs were subsequently analyzed in vitro. Single or combination mutations of rtL228 and rtL229 impaired HBV replication. Decreased HBsAg secretion in the supernatant and production in the cell lysate wasobserved with single rtL229W or in combination with rtL228W, while there was no significant difference between wild-type and mutant HBV with regard to the level of HBeAg in the supernatant and susceptibility to commonly-used NAs. Substitution mutations of rtL228 and/or L229 in HBV did not alter the susceptibility of the virus to NAs, although replication and HBsAg secretion were affected.