Adsorption and Infectivity of Human Immunodeficiency Virus Type 1 Are Modified by the Fluidity of the Plasma Membrane for Multiple‐Site Binding

Abstract

Based on the assumption that fluidity of the plasma membrane and viral envelope is necessary for recruiting additional receptors and ligands to the initial attachment site for “multiple‐site binding,” we determined the effect of increased temperature on viral infectivity. Infection of human immunodeficiency virus type 1 (HIV‐1) and a pseudotyped luciferase‐expressing chimeric virus using MAGI and GHOST/CXCR4 cells showed that in 1 hr of viral adsorption the extent of virus infection and the amount of tightly adsorbed viruses depended on temperature; and that membrane fluidity increased according to increased temperature. Augmented infection was observed as post‐attachment enhancement (PAE) when cells were washed and incubated at 40 C for 1 hr after viral adsorption. PAE was completely inhibited by 1 μM of anti‐CXCR4 peptide T140, and addition of T140 at 20 min resulted in a gradual loss of inhibition of PAE, indicating the need for a 30 to 40 min timelag to ensure tight multiple‐site binding. These data suggest that the accumulation of gp120 and receptor complex (multiple‐site binding) was needed to complete the infection. Treatments of cells with 0.05% Tween 20 or 2 μg/ml of anti‐HLA‐II antibody resulted in increases or decreases, respectively, of attached viruses and the infectivity. As well, Tween 20 and anti‐HLA‐II antibody enhanced and suppressed the fluidity of the plasma membrane, respectively. Amounts of adsorbed viruses and degrees of viral infectivity correlated with the intensity of fluidity of the plasma membrane, probably due to the formation of multiple‐site binding.

Complexation with chondroitin sulfate C and Polybrene rapidly purifies retrovirus from inhibitors of transduction and substantially enhances gene transfer

“…Interestingly, NIH 3T3 cells express about 10 5 amphotropic receptors per cell (Battini et al, 1996). Since retroviruses must bind to multiple receptors at the same time in order to transduce a cell (Bachrach et al, 2000;Harada et al, 2004), it is likely that only a fraction of the receptors would need to be blocked or otherwise inactivated in order to render a cell resistant to infection. These approximate calculations suggest that it is possible the plateau we observed in the dose response curve of polymer purified virus was due to saturation of the cellular receptors.…”

High Temperature Condition Enhances Retrovirus Infection to Cell

“…Recent report insisted that the enhancement of HIV-1 infection under high temperature condition was due to the increment of multiple-site binding of virus ligands and cellular receptors. 13) However, almost no up-regulation of VSV infection to cell (Fig. 1) said that multiple-site binding is not the main reason for enhanced infection of HIV-1 at 40°C.…”

“…2). One of recent paper 13) showed slightly enhanced adsorption by high temperature condition. The previous observation might be obtained by the result of trypsin treatment of cell before the cell lysis, which measured already fused virus amount, only.…”

Heterogeneity of Envelope Molecules Shown by Different Sensitivities to Anti‐V3 Neutralizing Antibody and CXCR4 Antagonist Regulates the Formation of Multiple‐Site Binding of HIV‐1

“…The V3 domain of gp120 is thought to be the primary determinant of coreceptor (CXCR4 or CCR5) usage (6) together with the V1/V2 contribution (7,9,19), and a single amino acid change in V3 could switch the viral coreceptor usage (3,14,28,33). Anti-V3 neutralization is proposed to operate mainly by high-occupancy of V3 (16) and/or by steric alteration of the envelope (1,10,11,15). Viruses with many fgp120 would need more anti-V3 antibodies to be highly occupied and neutralized than those with few fgp120.…”