The herpes simplex virus is a human neurotropic virus.  This is mostly examined for gene transfer in the nervous system.  The wild type HSV-1 virus is able to infect neurons and evade the host immune response, but may still become reactivated and produce a lytic cycle of viral replication.  Therefore, it is typical to use mutant strains of HSV-1 that are deficient in their ability to replicate.  Though the latent virus is not transcriptionally apparent, it does possess neuron specific promoters that can continue to function normally. Antibodies to HSV-1 are common in humans, however complications due to herpes infection are somewhat rare.  Caution for rare cases of encephalitis must be taken and this provides some rationale to using HSV-2 as a viral vector as it generally has tropism for neuronal cells innervating the urogenital area of the body and could then spare the host of severe pathology in the brain.