HIV-1 Proviral Integration Is Blocked by Agonists to the VpPAC2 Neuroendocrine Receptor.

Abstract

VPAC1 is a 7-transmembrane G-protein-coupled neuroendocrine receptor previously shown to transduce a facilitation signal for HIV-1 infection (Branch DR, et al., AIDS. 2002; 16:309–319). VPAC2, a related receptor, has been reported to have opposing function when compared to VPAC1 (Xia M, et al., J Immunol. 1996; 157:1132–1138; Tsutsumi M, et al., Diabetes. 2002; 51:1453–1460). We therefore examined whether stimulation of VPAC2, in contrast to VPAC1, may act to inhibit HIV-1 infection. Using three different and specific agonists of VPAC2, helodermin, RO 25-1553, and R3P55, daily treatment with low concentrations (10−9M) resulted in ~75% to 95% inhibition of either X4 or R5 HIV-1 productive infection in cell lines or primary peripheral blood mononuclear cells. The agonists VIP, PACAP, and secretin, that stimulate the two other VPAC receptor family members VPAC1 and PAC1, did not inhibit HIV-1 infection. Also, Hut78 cells, that lack VPAC2 and are infected by HIV-1, show no effect of VPAC2 agonists on HIV-1 infection. However, Hut78 cells transfected with human VPAC2 cDNA to overexpress this receptor become resistant to HIV-1 infection when treated with VPAC2 agonists.VPAC2-mediated inhibition of productive HIV-1 infection was not due to effects on CD4 or chemokine co-receptor expression, cell growth, or apoptosis. Treatment with VPAC2 agonists also did not inhibit HIV-1 entry into the host cell. However, compared to untreated or cells treated with VPAC1-specific agonists, VPAC2 stimulation profoundly inhibits HIV-1 proviral DNA integration into the host genome. The block in integration was found to be due to the ability of agonists to VPAC2 to inhibit formation of 2-LTR circles, required for HIV-1 integration within the nucleus. We conclude that VPAC2-specific agonists are strongly inhibitory for productive HIV-1 infection. Furthermore, this inhibition is mediated by suppression of 2-LTR circle formation preventing proviral integration. Agonists of VPAC2 appear to be excellent candidates for future development as possible drugs for the amelioration of treatments aimed at the prevention of HIV/AIDS.