[en] Varicella-zoster virus (VZV) latency in human dorsal root ganglia is characterized by the transcription of large regions of its genome and by the expression of large amounts of some polypeptides, which are also expressed during lytic cycles. The immediate early 63 protein (IE63) is a virion component expressed very early in cutaneous lesions and the first viral protein detected during latency. Immune response against IE63 has been evaluated among naturally immune adults with a history of chickenpox: Specific antibodies were detected in serum, and most subjects who had a T cell proliferation with unfractionated VZV antigens had T cell recognition of purified IE63. The cytotoxic T cell (CTL) response to IE63 was equivalent to CTL recognition of IE62, the major tegument component of VZV, whose immunogenicity has been previously described. T cell recognition of IE63 and other VZV proteins is one of the likely mechanisms involved in controlling VZV reactivation from latency.