Concanamycin A counteracts HIV-1 Nef to enhance immune clearance of infected primary cells by cytotoxic T lymphocytes

Abstract

Nef is an HIV-encoded accessory protein that enhances pathogenicity by down-regulating major histocompatibility class I (MHC-I) expression to evade killing by cytotoxic T lymphocytes (CTLs). A potent Nef inhibitor that restores MHC-I is needed to promote immune-mediated clearance of HIV-infected cells. We discovered that the plecomacrolide family of natural products restored MHC-I to the surface of Nef-expressing primary cells with variable potency. Concanamycin A (CMA) counteracted Nef at subnanomolar concentrations that did not interfere with lysosomal acidification or degradation and were nontoxic in primary cell cultures. CMA specifically reversed Nef-mediated down-regulation of MHC-I, but not CD4, and cells treated with CMA showed reduced formation of the Nef:MHC-I:AP-1 complex required for MHC-I down-regulation. CMA restored expression of diverse allotypes of MHC-I in Nef-expressing cells and inhibited Nef alleles from divergent clades of HIV and simian immunodeficiency virus, including from primary patient isolates. Lastly, we found that restoration of MHC-I in HIV-infected cells was accompanied by enhanced CTL-mediated clearance of infected cells comparable to genetic deletion of Nef. Thus, we propose CMA as a lead compound for therapeutic inhibition of Nef to enhance immune-mediated clearance of HIV-infected cells.

The HIV-1 proviral landscape reveals that Nef contributes to HIV-1 persistence in effector memory CD4+ T cells

“…In agreement with earlier studies, our findings suggest that targeting Nef can be an attractive strategy to reduce HIV-1 persistence during therapy by improving CTL responses. Recent promising studies have investigated the effects of Nef blockade on reducing HIV-1 infection and enhancing CD8+ T-cell clearance (71,(73)(74)(75)(76)(77)(78).…”

Structure–Activity Relationships of Natural and Semisynthetic Plecomacrolides Suggest Distinct Pathways for HIV-1 Immune Evasion and Vacuolar ATPase-Dependent Lysosomal Acidification

“…8 The fourth class of inhibitors includes plecomacrolides, which selectively block Nef-dependent disruption of MHC-I antigen presentation, restoring CTL killing of HIV-infected T cells. 6 In our hands, nanomolar concentrations of concanamycin A (CMA, 1) are sufficient to near-fully restore MHC-I surface expression in HIV-1-infected CD4 + T cells compared to a control lacking Nef. In comparison, hydroxypyrazole B9, which was structurally confirmed by NMR, did not alter MHC-I HLA-A2 levels in HIV-infected primary T cells across a range of concentrations up to more than 10 μM.…”

“…5 A small molecule that inhibits Nefmediated disruption of MHC-I antigen presentation could promote the "kill" step of the shock and kill strategy by restoring MHC-I surface expression and facilitating CTL-mediated elimination of cellular reservoirs. 6 Designing an effective HIV-1 Nef inhibitor to achieve a potential cure has challenged researchers for decades. Nef is a multifunctional protein that disrupts signal transduction pathways and intracellular protein trafficking.…”

Discovery and Biosynthesis of the Cytotoxic Polyene Terpenomycin in Human Pathogenic Nocardia

“…Many molecules in this family have bioactivities that are important in human and veterinary medicine, and key exemplars of this molecular family are the bafilomycins, 16-membered macrolactones with a hemiacetal side chain, and two conjugated diene units . The bafilomycins are inhibitors of vacuolar H + -ATPase and have a wide range of bioactivities, including antibacterial, antifungal, immunosuppressive, antitumor, or antiparasitic activity, and have been shown to enhance the clearance of HIV-infected T-cells. , Another closely related group of molecules that share similar bioactivities are the concanamycins, a group of 18-membered macrolactones . Collectively, bafilomycin and concanamycin-like compounds are referred to as plecomacrolides, from the Greek “pleco” (folded) in reference to their unusually folded side chain .…”