HIV drug binding to CCR5 co-receptor, illustration. The human immunodeficiency virus (HIV) binds to a co-receptor known as chemokine receptor 5 (CCR5). This receptor is a target for drugs designed to prevent the entry of human immunodeficiency virus 1 (HIV-1) into human host cells. Here, one such drug named maraviroc (red) is binding to the receptor at lower centre. The drug is also shown at upper left, in spacefilled form (red) and with its structural formula (top left).