Assessing the contribution of the herpes simplex virus DNA polymerase to spontaneous mutations.

Background: The thymidine kinase (tk) mutagenesis assay is often utilized to determine the frequency of herpes simplex virus (HSV) replication-mediated mutations. Using this assay, clinical and laboratory HSV-2 isolates were shown to have a 10- to 80-fold higher frequency of spontaneous mutations compared to HSV-1.

Methods: A panel of HSV-1 and HSV-2, along with polymerase-recombinant viruses expressing type 2 polymerase (Pol) within a type 1 genome, were evaluated using the tk and non-HSV DNA mutagenesis assays to measure HSV replication-dependent errors and determine whether the higher mutation frequency of HSV-2 is a distinct property of type 2 polymerases.

Comparison of methods for identifying resistant herpes simplex virus and measuring antiviral susceptibility.

Background: A number of in vitro assays are used to determine susceptibility of HSV to antiviral agents, but results from these in vitro assays do not necessarily correlate with treatment outcome.

Objectives: A method with improved capability for identifying an isolate as acyclovir (ACV) or penciclovir (PCV) resistant when resistance is borderline could greatly improve the management of HSV disease.

Study Design: A comparative evaluation of four in vitro assays, plaque reduction (PRA), DNA hybridization, plating efficiency (PEA) and plaque autoradiography (PAR) was performed to accurately identify and measure resistance of a TK-altered clinical HSV isolate (HSV-1 N4) from a patient who was non-responsive to ACV treatment.