The best characterized CCR5 allelic variant contains a CCR5∆32 in the coding region of the second extracellular loop, creating a severely truncated molecule that prevents CCR5 expression, thereby disrupting viral entry [37] and making CCR5∆32 homozygous individuals resistant to infection with CCR5-tropic strains of HIV [37, 50–52]. Here, CCR5 is linked to infection.