HIV-1 infection of a CD4-negative primary cell type: The oligodendrocyte

Oligodendrocyte Injury and Pathogenesis of HIV-1-Associated Neurocognitive Disorders

Oligodendrocytes wrap neuronal axons to form myelin, an insulating sheath which is essential for nervous impulse conduction along axons. Axonal myelination is highly regulated by neuronal and astrocytic signals and the maintenance of myelin sheaths is a very complex process. Oligodendrocyte damage can cause axonal demyelination and neuronal injury, leading to neurological disorders. Demyelination in the cerebrum may produce cognitive impairment in a variety of neurological disorders, including human immunodeficiency virus type one (HIV-1)-associated neurocognitive disorders (HAND). Although the combined antiretroviral therapy has markedly reduced the incidence of HIV-1-associated dementia, a severe form of HAND, milder forms of HAND remain prevalent even when the peripheral viral load is well controlled. HAND manifests as a subcortical dementia with damage in the brain white matter (e.g., corpus callosum), which consists of myelinated axonal fibers. How HIV-1 brain infection causes myelin injury and resultant white matter damage is an interesting area of current HIV research. In this review, we tentatively address recent progress on oligodendrocyte dysregulation and HAND pathogenesis.

Sulfatide inhibits HIV-1 entry into CD4-/CXCR4+ cells

Sulfatide (3'sulfogalactosylceramide) is the natural sulfated derivative of galactosylceramide (GalCer), a glycosphingolipid receptor allowing HIV-1 infection of CD4-negative cells from neural and intestinal tissues. The incorporation of exogenous sulfatide into the plasma membrane of HT-29 (a CD4-/GalCer+/CXCR4+ human intestinal cell line) or RD (CD4-/GalCer-/ CXCR4+ human rhabdomyosarcoma) resulted in a dose-dependent inhibition of HIV-1 infection. Experiments with luciferase reporter viruses pseudotyped with HIV-1 or amphotropic murine leukemia virus envelopes demonstrated that sulfatide acts at the level of viral entry. Paradoxically, the transfer of sulfatide in the plasma membrane of various CD4- cells resulted in increased binding of HIV-1. Surface pressure measurements were conducted to study the interaction of gp120 with glycosphingolipid monolayers. The data showed that gp120 could penetrate into a monomolecular film of GalCer, confirming the role of this glycosphingolipid as a functional receptor for HIV-1. In contrast, the insertion of gp120 into a monolayer of sulfatide was very limited. Moreover, the incorporation of sulfatide in a monomolecular film of GalCer specifically inhibited the penetration of gp120. In conclusion, these data show that sulfatide mediates gp120 binding but, in marked contrast with GalCer, is not able to initiate the fusion event.