Caution on CCR5

Companies have been working for years on blocking CC chemokine receptor 5 (CCR5) because it is a portal used by HIV to enter cells, with the most advanced compound in Phase III trials. But the endogenous function of CCR5 in macrophages was not known. A report on CCR5 and its endogenous ligand, CC chemokine ligand 5 (CCL5), in last week's Nature Medicine had good news and bad news for researchers.

The good news is that CCL5 binding to CCR5 appears to protect macrophages from succumbing to flu and cold virus infections, allowing them to reduce the impact of infection by clearing pathogens and debris left by cells that have died from the infection. The bad news is that blocking this effect could make HIV patients more vulnerable to such infections...