7.1.3.2 Herpes Simplex Virus HSV

This virus infects the nervous system. It is transmitted through direct contact and replicates in the skin or mucosal membrane before infecting the nervous cells. It shows both lytic and latent function. The lytic cycle, induces cell death after viral replication. The latent function keeps the virus in the host cell for a long time. (Wolf, J1994, Glorioso et al 1995)

The following must be taken into consideration for an efficient HSV vector that are suitable for gene therapy

1. The vector must be non-toxic for nerve cells as well as for cell lines

2. The desired gene must be expressed in sufficient level, during the latency condition of the vector.

A number of HSV vectors have been developed.  They are constructed by deleting at least one of the essential early regulatory genes, making the virus less cytotoxic and still latent (Glorioso et al 1995)