Antibody binding is a dominant determinant of the efficiency of human immunodeficiency virus type 1 neutralization

Primary and laboratory-adapted variants of human immunodeficiency virus type 1 (HIV-1) exhibit a wide range of sensitivities to neutralization by antibodies directed against the viral envelope glycoproteins. An antibody directed against an artificial FLAG epitope inserted into the envelope glycoproteins of three HIV-1 isolates with vastly different neutralization sensitivities inhibited all three viruses equivalently. Thus, naturally occurring HIV-1 isolates that are neutralization resistant are not necessarily more impervious to the inhibitory consequences of bound antibody. Moreover, the binding affinity of the anti-FLAG antibody correlated with neutralizing potency, underscoring the dominant impact on neutralization of antibody binding to the envelope glycoproteins.