THE ROLE OF ANTIBODY CONCENTRATION AND AVIDITY IN ANTIVIRAL PROTECTION

Neutralizing antibodies are necessary and sufficient for protection ag ainst infection with vesicular stomatitis virus(VSV). The in vitro neu tralization capacities and in vivo protective capacities of a panel of immunoglobulin G monoclonal antibodies to the glycoprotein of VSV wer e evaluated. In vitro, neutralizing activity correlated with avidity a nd with neutralization rate constant, a measure of on-rate. However, i n vivo, protection was independent of immunoglobulin subclass, avidity , neutralization rate constant, and in vitro neutralizing activity; ab ove a minimal avidity threshold, protection depended simply on a minim um serum concentration. These two biologically defined thresholds of a ntibody specificity offer hope for the development of adoptive therapy with neutralizing antibodies.