TKT and infection: To examine if removal of the fusion regulatory elements of both the gBcyt and gHcyt further exacerbated syncytia formation during infection, a BAC with amino acids 834-841 of gH deleted and the Y881 in the gBcyt ITIM substituted with phenylalanine was constructed using a pOka BAC that expressed ORF36, the thymidine kinase, tagged with EGFP at the C-terminus (pOka-TK-GFP).