VZV ORF4 encodes an IE4 protein that acts as transactivator of several immediate early, early and late VZV genes. Dimerization of IE4 is required for its transactivation function. During the initial phase of viral infection, it mainly localizes in the nucleus, whereas later in infection it localizes in the cytoplasm. IE4 is a phosphoprotein of approximately 50kDa and together with IE62 and IE63 constitutes a viral tegument. IE4 is an essential factor for viral replication and for the establishment of a latent infection. Our anti VZV ORF4 antibody VZ 4.05 works in ELISA (on immunogen), in IF (on VZV infected cells) and each LOT is validated for Western blot on VZV infected cell lysates where it gives a pattern as described in J Virol. 2013 Jun;87(12):6943-54.