Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

We have analyzed the binding of soluble CD4 (sCD4) to human immunodeficiency virus type 1 (HIV-1) virions (isolates IIIB and RF) at 4 and 37 degrees C by using a combination of gel exclusion chromatography and enzyme-linked immunosorbent assay detection systems. The sCD4 binding curve at 37 degrees C indicates that the affinity of the interaction of sCD4 with gp120 on the virion surface is indistinguishable from the affinity of sCD4 for the equivalent concentration of soluble gp120. At 4 degrees C, however, the affinity of sCD4 for virion-bound gp120 but not for soluble gp120 is reduced by about 20-fold. Binding of sCD4 (greater than 0.2 microgram/ml) to virions at 37 degrees C but not 4 degrees C induces the rapid dissociation of a major proportion of gp120 from gp41 on the virion surface. This dissociation requires occupancy by sCD4 of multiple (probably two) binding sites on a gp120-gp41 oligomer. At 37 degrees C there are two components to the neutralizing action of sCD4 on HIV-1; reversible, competitive inhibition at low sCD4 concentrations (less than 0.2 microgram/ml) and essentially irreversible inhibition due to gp120 loss at higher sCD4 concentrations. At 4 degrees C, sCD4 neutralizes HIV infectivity by competitive inhibition alone. These findings may have implications for the HIV-CD4+ cell binding and fusion reactions and the mechanism by which sCD4 blocks infectivity.

Type

Journal article

Journal

J Virol

Publication Date

03/1991

Volume

65

Pages

1133 - 1140

Keywords

CD4 Antigens, Cell Line, Enzyme-Linked Immunosorbent Assay, HIV Envelope Protein gp120, HIV-1, Humans, Kinetics, Neutralization Tests, Protein Binding, Recombinant Proteins, Virion