2.2. Propagation of VZVeGFP-ORF23 in ARPE19 cells

The human retinal pigment epithelial cell line ARPE19 (ATCC, CRL-2302) was used for the propagation of the VZV^eGFP-ORF23 strain, as previously described (25, 28). In this pOka-derived recombinant VZV strain, the minor capsid protein ORF23 is fused with the enhanced green fluorescent protein (eGFP). Following VZV^eGFP-ORF23 propagation in ARPE19 cells, infected cells were harvested and cryopreserved in 900µL cARPE19 medium [90% DMEM/F12 (Gibco, 11320-074) + 10% FBS (Gibco, 10270-106)] + 100µL DMSO (Sigma, D2650) at a concentration of 1.0 x 10⁶ cells per vial. After thawing, VZV^eGFP-ORF23 titres in plaque-forming units (PFU) were determined using an infectious foci assay in ARPE19 cells, according to previously described procedures (25, 28, 29).