Jefferson researchers identify new mechanism of blocking HIV-1 from entering cells

Researchers at from the Kimmel Cancer Center at Jefferson have found a novel mechanism by which drugs block HIV-1 from entering host cells. Cellular invasion by HIV-1 requires the concerted action of two proteins on the viral surface: gp120 and gp41. The function of gp41 is to get the viral contents into the interior of the host cells. This requires the association of two distinct regions of gp41 called N-HR and C-HR. Anti-HIV-1 agents known as fusion inhibitors target the N-HR or C-HR and disrupt their association, which prevents the virus from entering into the host cell. When the inhibitors bind to the gp41 C-HR, the protein rapidly deactivates before inhibitors have time to dissociate. But when the inhibitors bind to the gp41 N-HR, deactivation takes a very long time, and many inhibitors can readily unbind. To potently inhibit HIV-1 entry, a C-HR targeting fusion inhibitor can have a relatively low affinity, but an N-HR targeting fusion inhibitor must bind extremely tightly.