Hepatitis B virus escape mutants induced by antiviral therapy.

The hepatitis B virus (HBV) polymerase and envelope genes overlap in such a way that resistance mutations to antiviral agents in the reverse transcriptase gene may affect the antigenicity of the HBV surface antigen. Mutant viruses may escape serological diagnosis using specific anti-HBV surface antigen antibodies, causing occult forms of chronic hepatitis B. Moreover, these HBV strains may evade vaccine protection, representing a public health challenge. Thus, the circulation of HBVs encoding envelope mutations selected by antiviral agents requires close monitoring.