Herpes simplex virus drug resistance-HSV thymidine kinase mutants

The widespread use of nucleoside analog antivirals to treat patients infected with herpes simplex virus (HSV) is indicted by the statement in a recent publication that, “More than 2.3 million kg of these drugs have been prescribed…in >30 countries” (1). Many clinical trials have demonstrated the effectiveness of these antivirals. However, clinical studies have also reported the detection of drugresistant viral mutants, particularly important in the care of immunosuppressed patients. Laboratory studies have indicated the mechanisms of viral resistance. The development of drug-resistant mutants of HSV has raised the issue of the potential pathogenicity of these mutants, and also mechanisms of HSV infection whereby such mutants may arise.