title: Human immunodeficiency virus type 1 Nef protein mediates neural cell death: a neurotoxic role for IP-10.
abstract: HIV-1 Nef is expressed in astrocytes, but a contribution to neuropathogenesis and the development of HIV-associated dementia (HAD) remains uncertain. To determine the neuropathogenic actions of the HIV-1 Nef protein, the brain-derived (YU-2) and blood-derived (NL4-3) Nef proteins were expressed in neural cells using an alphavirus vector, which resulted in astrocyte death (P < 0.001). Supernatants from Nef-expressing astrocytes also caused neuronal death, suggesting the release of neurotoxic molecules by astrocytes. Analysis of pro-inflammatory gene induction in astrocytes expressing Nef revealed increased IP-10 mRNA expression (4000-fold) that was Nef sequence dependent. Recombinant IP-10 caused selective cell death in neurons (P < 0.001) but not astrocytes, and the cytotoxicity of supernatant from astrocytes expressing Nef YU-2 was blocked by an antibody directed against the chemokine receptor CXCR3 (P < 0.001). SCID/NOD mice implanted with a Nef YU-2-expressing vector displayed abnormal motor behavior (P < 0.05), neuroinflammation, and neuronal loss relative to controls. Analysis of mRNA levels in brains from patients with HAD also revealed increased expression of IP-10 (P < 0.05), which was confirmed by immunoreactivity detected principally in astrocytes. Phylogenetic and protein structure analyses of Nef sequences derived from HIV/AIDS patients with and without HAD suggested viral evolution toward a neurotropic Nef protein. These results indicate that HIV-1 Nef contributes to neuropathogenesis by directly causing astrocyte death together with indirect neuronal death through the cytotoxic actions of IP-10 on neurons. Furthermore, Nef molecular diversity was evident in brain tissue among patients with neurological disease and which may influence IP-10 production by astrocytes.
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary AB, Canada.
authors.forename: Guido
authors.initials: G
authors.lastname: van Marle
authors.forename: Scot
authors.initials: S
authors.lastname: Henry
authors.forename: Tiona
authors.initials: T
authors.lastname: Todoruk
authors.forename: Andrea
authors.initials: A
authors.lastname: Sullivan
authors.forename: Claudia
authors.initials: C
authors.lastname: Silva
authors.forename: Sean B
authors.initials: SB
authors.lastname: Rourke
authors.forename: Janet
authors.initials: J
authors.lastname: Holden
authors.forename: Justin C
authors.initials: JC
authors.lastname: McArthur
authors.forename: M John
authors.initials: MJ
authors.lastname: Gill
authors.forename: Christopher
authors.initials: C
authors.lastname: Power
mesh_terms: D015526:AIDS Dementia Complex / Q000378:metabolism / Q000503:physiopathology; D000818:Animals; D030801:Animals, Genetically Modified; D001253:Astrocytes / Q000378:metabolism / Q000821:virology; D016923:Cell Death; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000235:genetics; D054357:Chemokine CXCL10; D019743:Chemokines, CXC / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology*; D015693:Gene Products, nef / Q000096:biosynthesis / Q000235:genetics*; D005822:Genetic Vectors; D015497:HIV-1 / Q000235:genetics / Q000472:pathogenicity; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis / Q000235:genetics; D053583:Interleukin-1beta; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009498:Neurotoxins / Q000494:pharmacology; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D054311:nef Gene Products, Human Immunodeficiency Virus
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D054357:Chemokine CXCL10; D019743:Chemokines, CXC; D015693:Gene Products, nef; D007375:Interleukin-1; D053583:Interleukin-1beta; D009498:Neurotoxins; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; C052994:interleukin-1beta (163-171)