Comment on “Inhibition of Hepatitis B Virus Replication by APOBEC3G”

was recently identified as a natural resistance gene that restricts efficient propagation of human immunodeficiency virus and other ret-roviruses. The enzyme induces massive cyt-idine to uridine (C3U) deamination of sin-gle-stranded retroviral DNA, resulting in DNA degradation or lethal guanine to ade-nine (G3A) hypermutation (1). Hepadnavi-ruses, including hepatitis B virus (HBV), replicate by reverse transcription of a pre-genomic RNA intermediate inside nucleocap-sids, placing them into the family of retroele-ments (2). These observations, along with an earlier report describing G3A hypermuta-tions in natural HBV variants (3), raise th