Biosafety of gene therapy vectors derived from herpes simplex virus type 1

The majority of humans have been infected with Herpes Simplex Virus Type 1 (HSV-1) and harbor its viral DNA in the latent form within neurons for lifetime. This, combined with the absence of serious adverse effects due to HSV-1 derived vectors in clinical trials so far, highlight the potential to use this virus to develop neuronal gene transfer vectors which are transparent to the host, allowing the effects of the transgene to act without interference from the transfer system eg., for functional genomics in basic neuroscience or gene therapy of neurological disorders. On the other hand, other HSV-1 derived vectors which also have a promising perspective in the clinic, are designed to have enhanced cytotoxicity in certain cell types, as in the case of oncolytic vectors. Understanding virus-host interactions is fundamental not only to the success of these gene therapy vectors but also with respect to identifying and minimizing biohazards associated with their use. In this review we discuss characteristics of HSV-1 and gene therapy vectors derived from this virus which are useful to consider in the context of biosafety risk assessment and risk management.