CCR5 receptor is expressed on most immune cells, neurons, and glial cells, and engages many chemokines including CCL3 (MIP-1α), CCL4 (MIP-1β), and CCL5 (RANTES); the expressions of these and other chemokines are all increased in Ccr5−/− mice in both infection models, hinting at an intricate compensatory mechanism. This evidence concerns the gene CCL5 and infection.