VZV ORF21 encodes a 115 kDa protein that is essential for viral replication in cell culture and is also expressed during, but is not required for establishment of latency in dorsal root and cranial nerve ganglia. During infection, VZV ORF21 protein localizes to both nuclei and cytoplasm of infected cells and, together with proteins encoded by VZV ORFs 20, 21, 23, 33, 40 and 41, forms the icosahedral nucleocapsid core of VZV virions. In addition, protease treatment and detergent solubilization experiments of VZV virions suggest that VZV ORF21 encoded protein is not associated with tegument of VZV particles. Our anti-VZV ORF21 antibody VZ 21.3.05 works in ELISA (on immunogen) and IF (on VZV infected cells), and each LOT is validated for Western blot (of VZV infected cell lysates), where it specifically recognizes a protein species of ~116 kDa, which corresponds well to the predicted size of ~115 kDa protein encoded by the VZV ORF 21 (described in J Virol. 2013 Jun;87(12):6943-54.).