Second, transmission of HIV-1 strains that use C-C chemokine receptor 5 (CCR5) as the entry coreceptor is highly favored [5], [6], [7], [8], [9], [10], consistent with the observation that individuals with deletion mutations in the coding region of CCR5 are highly resistant to HIV-1 infection [11], [12], [13]. This evidence concerns the gene CCR5 and HIV-1 infection.