VARICELLA-ZOSTER VIRUS GENE-63 ENCODES AN IMMEDIATE-EARLY PROTEIN THAT IS ABUNDANTLY EXPRESSED DURING LATENCY

Varicella-zoster virus (VZV) gene 63 encodes a protein with a predicte d molecular mass of 30.5 kDa which has amino acid similarities with th e immediate-early (IE) protein 22 (ICP-22) of herpes simplex virus typ e 1. In order to study the expression of this protein during lytic and latent infection, gene 63 was cloned in frame and downstream from the glutathione-S-transferase gene, expressed as a fusion protein, and pu rified. In VZV-infected Vero cells, antibodies directed against this p rotein detect two polypeptides of 45 and 38 kDa which are localized bo th in the cytoplasm and in the nucleus. Using a sequential combination of transcription and protein synthesis inhibitors (actinomycin D and cycloheximide, respectively), we demonstrated the immediate-early natu re of this protein, which can thus be named IE63. Using a rat model of VZV latency, we showed that IE63 is heavily expressed, essentially in neurons, during latency. IE63 can also be detected in the skin of pat ients showing early herpes zoster symptoms.