Herpes Simplex Virus Vectors for the Nervous System

Herpes simplex virus type 1 (HSV1) has a number of properties which could potentially be exploited in the development of vectors for the delivery of genes to the nervous system. These include a natural tropism for neurons, a large viral genome allowing the insertion of multiple exogenous genes, and the ability to establish asymptomatic life-long latent infections. Despite these inherent advantages, the development of HSV vectors successfully exploiting all these properties has been problematical. This has mainly been due to either vector toxicity or an inability to maintain transgene expression in the long term. Recent progress towards overcoming these problems and several applications of the technology are discussed.