Neurovirulence of varicella and the live attenuated varicella vaccine virus.

Varicella-zoster virus (VZV) is a neurotropic herpesvirus, which can cause a variety of complications during varicella infections. These range from meningoencephalitis to polyneuritis to retinitis. After primary VZV infection, VZV enters the dorsal root ganglia in a latent state. Reactivation from latency leads to zoster. The velocity of VZV is 13 cm per day, as the virus travels from ganglion to skin. The live attenuated varicella vaccine virus is markedly less neurovirulent than the wild-type virus. Nevertheless, a few cases of herpes zoster due to the vaccine virus have been documented. Usually, herpes zoster occurs in the same arm as the vaccination, often 3 or more years after vaccination. Thus, herpes zoster in a vaccinee often represents a reactivation of vaccine virus that was carried to the cervical dorsal root ganglia from a site of local replication in the arm. Finally, the role of autophagy during VZV infection is discussed. Autophagosome formation is a prominent feature in the skin vesicles during both varicella and herpes zoster. Therefore, autophagy is one of the innate immune mechanisms associated with VZV infection in humans.