Detecting Hepatitis B Surface Antigen Mutants
Hepatitis B viral mutants can emerge in patients as a result of selection pressure from either immune response or treatment options. Mutations that occur within the immunodominant epitopes of hepatitis B surface antigen (HBsAg) allow mutant virus to propagate in the presence of a neutralizing immune response, while wild-type virus is reduced to undetectable levels. HBsAg mutants present as false-negative results in some immunoassays. An understanding of immunoassay reactivity with HBsAg mutants is key to establishing an appropriate testing algorithm for hepatitis B virus detection programs.

Over the past decade, the importance of hepatitis B virus (HBV) mutants has made a transition from an academic phenomenon of unknown prevalence to a factor for consideration during disease diagnosis. HBV infection has a major effect on world health care: more than one third of the world's population has been infected at some point; ≈ 350 million people are currently infected. This immense worldwide reservoir of infection serves as the basis for the generation of HBV mutants because of the unique molecular biology of this virus. Since the late l980s, we have seen the emergence of mutants across the entire HBV genome as the virus responds to selective pressures, such as vaccination and antiviral therapy. Viral adaptation through mutation will continue as new treatment options are employed and current treatment options are expanded into areas of endemic infection. HBV mutant surveillance and understanding of HBV mutant impact on disease diagnosis will pose a challenge to global health care for the foreseeable future. Thus, diagnosticians and the healthcare industry need to increase their awareness of HBV mutants and how these mutants may alter current diagnostic and treatment algorithms. This article addresses recent information concerning the emergence of hepatitis B surface antigen (HBsAg) mutants, their impact on viral antigen presentation, latest prevalence data, and discussion of the issues associated with detection of mutants in healthcare settings.