First identified more than 20 years ago at UCLA, defensins are peptides naturally produced by the immune system to ward off viruses. However, it was unclear how defensins worked. Now UCLA and NIH scientists have discovered that a specific defensin called retrocyclin-2 (RC2) binds to carbohydrate-containing proteins in cell membranes. This mechanism erects molecular barricades that block attacking viruses from entering and infecting the cell. RC2 stops the virus in its tracks, preventing it from replicating and spreading throughout the body.

The NIH/UCLA team used human and animal cell lines to demonstrate RC2's protection against the influenza virus. The team's earlier studies suggest that RC2 offers great promise as the lead compound for new antiviral drugs to fight off HIV and herpes, as well. Unlike antibodies, however, defensins are not pathogen specific. In addition to blocking viruses, RC2 also kills several bacteria that are highly resistant to conventional antibiotics.