Immunofluorescence Detection of δ Opioid Receptors (DOR) on Human Peripheral Blood CD4+ T Cells and DOR-Dependent Suppression of HIV-1 Expression

The delta opioid receptors (DORs) modulate T cell proliferation, IL-2 production, chemotaxis, and intracellular signaling. Moreover, in DOR-transfected Jurkat cells, delta opioids have been shown to suppress HIV-1 p24 Ag expression. These observations led us to characterize the expression of DORs by human peripheral blood T cells and to determine whether a specific DOR agonist, benzamide,4-([2,5-dimethyl-4-(2-propenyl)-1-piperazinyl](3-methoxyphenyl)methyl]-N,-,(2S[1(S*),2alpha,5beta])-(9Cl) (SNC-80), can suppress p24 Ag expression by HIV-1-infected CD4+ T cells obtained from normal donors. By immunofluorescence flow cytometry, PHA stimulated the expression of DOR from 1.94 +/- 0.70 (mean +/- SEM) to 20.70 +/- 1.88% of the PBMC population by 48 h (p < 0.0001). DOR expression was approximately 40% of both the PHA-stimulated CD4+ and CD8+ T cell subsets, and virtually all DORs were found on these subsets. To determine whether activated DORs suppress HIV-1 expression, PBMC were prestimulated with PHA, and then CD4+ T cells were purified, pretreated with SNC-80, and infected with HIV-1. In a concentration-dependent manner, SNC-80 inhibited production of p24 Ag. SNC-80 10(-10) M maximally suppressed (approximately 50%) both lymphocytotropic (HIV-1 MN) and monocytotropic (SF162) strains; higher concentrations were less effective. Naltrindole, a selective DOR antagonist, abolished the inhibitory effects of SNC-80. Kinetic studies indicated that 24-h pre- or postincubation with SNC-80, relative to infection with HIV-1, eliminated its suppressive effects. Thus, stimulating the DORs expressed by activated CD4+ T cells significantly suppressed the expression of HIV-1. These findings suggest that opioid immunomodulation directed at host T cells may be adjunctive to standard antiviral approaches to HIV-1 infection.