HBsAg Variants: Common Escape Issues

Mutations have been described in all of the four open reading frames of the hepatitis B virus (HBV), however, from a clinical perspective the surface escape mutant is the most troublesome. Hepatitis B surface antigen (HBsAg) variants may impair diagnosis, or allow the virus to escape vaccine-induced immunity or passive immunoglobulin therapy. HBV mutants with amino acid substitutions, within the common “a” determinant of HBsAg have been identified, and as a result, the HBsAg cannot be detected in some assays (diagnostic-escape). In these situations, the HBsAg mutants may arise in patients with a HBV infection, but they have been diagnosed as HBsAg negative. This review deals with the latest results on the performance of HBsAg assays, as well as the reactivity of native and or recombinant mutants of HBsAg.