The emergence of envelope and precore/core variants of hepatitis B virus: the potential role of antibody selection.

The appearance of replication-competent variants of hepatitis B virus (HBV) with mutations in the envelope and precore/core proteins emphasizes that these proteins are the focus of immune selection pressure in the human host. The sequence and speed of application of the multiple selection pressures (humoral and possibly cellular) determine the virologic and clinical outcome. When these variant viruses are passed to a new host, in the absence of the immune selection pressures or modified immune pressures which resulted in their selection, a clinical picture different from that seen in the original host may emerge.