As before, the number of gfp-positive cells after infection with the ORF4−Tet+ mutant was significantly reduced when compared to the infection with parental virus while expression of ORF4 of KSHV rescued the phenotype of the MHV-68 ORF4 deletion mutant ORF4−Tet+ (Fig. 7). This evidence concerns the gene CTTNBP2 and infection.