The design of recombinant HSV-1 vectors for delivery of transgenes to the central nervous system is undergoing constant development. Problems associated with the construction and use of such vectors include the requirement for detection of recombinant versus nonrecombinant virus in vitro and also the identification of transduced cells in vivo. This could be overcome by the insertion of reporter genes such as lacZ or green fluorescent protein (GFP) under a separate promoter to the transgene to be expressed. In this case, however, reporter gene expression does not necessarily confirm transgene expression as a separate RNA must be produced. This study reports the use of an encephalomyocarditis virus internal ribosome entry site (IRES) to enable the translation of two reporter genes from a single mRNA transcript driven by the same promoter within a disabled HSV vector, and discusses the potential advantages of this approach.
