CCR5 and HIV infectious disease: In CD4+ cells, this mutation inhibits CCR5 protein expression on the cell surface, thereby preventing HIV envelope fusion.9 Moreover, the presence of the mutant delta32 protein in the endoplasmic reticulum inhibits transport of the wild-type CCR5 protein to the cell surface via a trans-dominant mechanism.10 Because most strains of HIV use CCR5 to enter host cells, the deletion of both copies of the CCR5 gene (not one copy) protects against HIV infection.11,12 Thus, Nana would still be susceptible to HIV infection.