| The fusion of human immunodeficiency virus type 1 (HIV-1) to host cells is a dynamic process governed by the interaction between viral glycoproteins and major receptor, CD4, and co-receptor on the cell surface. How these receptors organize at the virion-cell interface to promote a fusion site is not well understood. Using single-molecule force spectroscopy, we map the tensile strengths, lifetimes, and energy barriers of individual intermolecular bonds between HIV-1 gp120 and its receptors CD4 and CCR5 or CXCR4. Initially examining this interaction using soluble gp120, we move to more physiologically consistent whole viral particles. For both soluble gp120 and virion associated gp120, at short times of contact between cell and virion the gp120-CD4 bond is shorter and less stable than the gp120-CCR5 bond. However using whole viral particles we observe that within 0.3 s, individual gp120-CD4 bonds undergo rapid destabilization. This destabilization is significantly enhanced by the co-receptor CCR5 and altered by fusion inhibitors. These measurements highlight the instability and low tensile strength of gp120-receptor bonds, uncover a synergistic role for CCR5 in the progression of the gp120-CD4 bond and suggest the formation of a cell-virus adhesion interface.;We also expand the use of single-molecule force spectroscopy to analyze the adhesive and micromechanical properties of several patient derived viral clones to determine as yet unmeasured properties of gp120-CCR5/CXCR4 coreceptor adhesion. These measurements emphasize the variability of the gp120-CD4 bond compared to either gp120-coreceptor bond. In addition, we measure a significant difference between gp120-CCR5 and gp120-CXCR4 bonds. A previously suggested correlation between gp120-receptor adhesion and infection was not observed and draws attention to the viral response to adhesion and its significance in determining viral infection efficacy.;We use the results obtained by single-molecule force spectroscty in a stochastic computational model to demonstrate that viral protein orientation and properties of the plasma membrane will spontaneously organize the receptors bound between the virion and cell. Specifically, we examine how properties of the system such as membrane rigidity, receptor concentration and protein diffusivity will affect the bond organization to gain a greater mechanistic understanding of the viral adhesion process. |
