GLV-1h153 construct. a. GLV-1h153 was derived from GLV-1h68 by replacing the gus A expression cassette at the A56R locus with the hNIS expression cassette through in vivo homologous recombination. Both viruses contain RUC-GFP and lacZ expression cassettes at the F14.5L and J2R loci, respectively. PE, PE/L, P11, and P7.5 are VACV synthetic early, synthetic early/late, 11K, and 7.5K promoters, respectively. TFR is human transferrin receptor inserted in the reverse orientation with respect to the promoter PE/L.b. Confirmation of GFP, LacZ, and lack of gus A marker gene expression in GLV-1h153 infected CV-1 cells. While the gus A gene cassette is expressed in cells infected with parent virus GLV-1h68, this has been replaced by the hNIS gene cassette in GLV-1h153, leading to loss of gus A expression.