LIPID-COMPOSITION AND FLUIDITY OF THE HUMAN-IMMUNODEFICIENCY-VIRUS ENVELOPE AND HOST-CELL PLASMA-MEMBRANES

Previous studies have indicated that human immunodeficiency virus (HIV ) is enclosed with a lipid envelope similar in composition to cell pla sma membranes and to other viruses. Further, the fluidity, as measured by spin resonance spectroscopy, is low and the viral envelope is amon g the most highly ordered membranes analyzed. However, the relationshi p between viral envelope lipids and those of the host cell is not know n. Here we demonstrate that the phospholipids within the envelopes of HIV-1RF and HIV-2-L are similar to each other but significantly differ ent from their respective host cell surface membranes. Further, we dem onstrate that the cholesterol-to-phospholipid molar ratio of the viral envelope is approximately 2.5 times that of the host cell surface mem branes. Consistent with the elevated cholesterol-to-phospholipid molar ratio, the viral envelopes of HIV-1RF and HIV-2-L were shown to be 7. 5% and 10.5% more ordered than the plasma membranes of their respectiv e host cells. These data demonstrate that HIV-1 and HIV-2-L select spe cific lipid domains within the surface membrane of their host cells th rough which to emerge during viral maturation.