The CCR5 gene encodes a chemokine receptor (a long name for a protein that sits in the walls of our cells).When the body has been invaded by a pathogen such as a cold virus, CCR5 plays an important role in fighting that virus.Smart viruses such as HIV-1, however, hijack the CCR5 protein and use it to sneak into CD4+ T cells & macrophages.
In some populations the CCR5 gene has experienced a mutation that deleted 32 basepairs in the gene sequence.The mutation prevents the expression of the protein on the cell surface.As a result, people with this mutation show some degree of protection from certain viruses.In fact, homozygosity of the CCR5-D32 allele (meaning BOTH copies of the gene are mutated) leads to “nearly complete resistance to HIV-1 infection.”People with only 1 copy are as much as 70% resistant! Surprisingly, homozygotes do not show any other problems as a result of the mutation.