Cholesterol Depletion of Human Immunodeficiency Virus Type 1 and Simian Immunodeficiency Virus with β-Cyclodextrin Inactivates and Permeabilizes the Virions: Evidence for Virion-Associated Lipid Rafts

Abstract

Recent evidence suggests that human immunodeficiency virus type 1 (HIV-1) particles assemble and bud selectively through areas in the plasma membrane of cells that are highly enriched with glycosylphosphatidylinositol-anchored proteins and cholesterol, called lipid rafts. Since cholesterol is required to maintain lipid raft structure and function, we proposed that virion-associated cholesterol removal with the compound 2-hydroxy-propyl-␤-cyclodextrin (␤-CD) might be disruptive to HIV-1 and simian immunodeficiency virus (SIV). We examined the effect of ␤-CD on the structure and infectivity of cell-free virions. We found that ␤-CD inactivated HIV-1 and SIV in a dose-dependent manner and permeabilized the viral membranes, resulting in the loss of mature Gag proteins (capsid, matrix, nucleocapsid, p1, and p6) without loss of the envelope glycoproteins. SIV also lost reverse transcriptase (RT), integrase (IN), and viral RNA. IN appeared to be only slightly diminished in HIV-1, and viral RNA, RT, matrix, and nucleocapsid proteins were retained in HIV-1 but to a much lesser degree. Host proteins located internally in the virus (actin, moesin, and ezrin) and membraneassociated host proteins (major histocompatibility complex classes I and II) remained associated with the treated virions. Electron microscopy revealed that under conditions that permeabilized the viruses, holes were present in the viral membranes and the viral core structure was perturbed. These data provide evidence that an intact viral membrane is required to maintain mature virion core integrity. Since the viruses were not fixed before ␤-CD treatment and intact virion particles were recovered, the data suggest that virions may possess a protein scaffold that can maintain overall structure despite disruptions in membrane integrity.

HIV turns plasmacytoid dendritic cells (pDC) into TRAIL-expressing killer pDC and down-regulates HIV coreceptors by Toll-like receptor 7-induced IFN-α

“…In addition, the effect of Imiq on these parameters was abrogated by A151. Finally, we demonstrated that removal of viral RNA from HIV-1 particles with ␤-CD resulted in complete loss of the ability of these RNA-depleted HIV-1 particles to induce TRAIL expression by pDC (25). These results demonstrate that TLR7 is the only TLR that is required for HIV-induced transformation of pDC into IKpDC.…”

“…We depleted ssRNA from HIV-1 particles by treatment with 80 mM ␤-cyclodextrin (HIV ␤CD ), a chemical modification that induces a hole in the virion capsid, liberating ssRNA but retaining capsid proteins as previously shown (25). These RNA-free particles were used for the culture of pDC (SI Fig.…”

Copatching and Lipid Raft Association of Different Viral Glycoproteins Expressed on the Surfaces of Pseudorabies Virus-Infected Cells

“…Further, the viral glycoprotein distribution in the HSV virion envelope has been shown to be nonrandom, which has been hypothesized to be caused by association of viral glycoproteins with lipid rafts (17). In addition, we have found that, like for human immunodeficiency virus (15,27), cholesterol in the PRV envelope is required for infectivity, since depletion of cholesterol from PRV preparations by using 10 mM MCD completely abolished PRV's ability to successfully infect susceptible cells (data not shown). Therefore, it will be interesting to dissect the exact role of lipid rafts during alphaherpesvirus particle formation.…”

Lipidomics of host–pathogen interactions

“…Phosphatidylcholine accounts to 75% of total phospholipid [85] GP Viral envelopes are enriched in sphingomyelin [8,86] SP Envelope cholesterol is critical for structure and infectivity [87][88][89] ST 2 Phosphatidylserine stimulates entry of enveloped viruses [90,91] Mannose receptor binds to the ManLAM mannose caps of mycobacteria and mediates phagocytosis [92] GPI anchored proteins (host [35,36] and parasite [37] …”