Schematic of the gene content of engineered viruses. All engineered viruses were generated from a cDNA of the A2 strain of HRSV. Viruses RSΔSH, RSΔG, and RSΔF are missing the ORFs of the SH, G, and F genes, respectively, which have been substituted with that of GFP. Virus RSΔSH,G,F has the ORFs encoding each of the three HSRV glycoproteins replaced with those of reporter genes GFP, CAT, and GUS, respectively.