VZV ORF18 (UniProtKB – Q6QCN7) encodes a small subunit of the viral ribonucleotide reductase, which together with the large subunit, encoded by the VZV ORF19, forms the ribonucleotide reductase holoenzyme complex (RNR) (Curr. Top. Microbiol. Immunol. 342, 1–14 (2010)). RNR acts as a key enzyme that catalyzes the reductive synthesis of deoxyribonucleotides from corresponding ribonucleotides, thus providing precursors for viral DNA replication in non-dividing cells, as well as enabling reactivation of the virus in latently infected cells. VZV ORF18 is an orthologue of HSV1 protein UL40. Kinetics of VZV ORF8 protein expression during lytic infection in vitro was assessed using western blot and our anti-VZV18 antibody VZ 18C.16 and ORF18 were detected between 8 and 10 hpi, typical for proteins involved in viral DNA replication at an early (E) phase of viral infection. Our anti-VZV18 antibody VZ 18C.16 works in ELISA (on immunogen) and each LOT is validated for Western blot of VZV infected cell lysates, where it recognizes a protein of ~36 kDa, which corresponds well to the predicted protein size (described in J Virol. 2013 Jun;87(12):6943-54.).