THE EFFECT OF NEUTRALIZING MONOCLONAL-ANTIBODIES AN EARLY EVENTS IN RIFT-VALLEY FEVER VIRUS INFECTIVITY

Monoclonal antibodies (mAb) were used to examine possible stages at wh ich antibody-mediated neutralization of Rift Valley fever virus occurs , and to assess whether binding of antibody is dependent on viral prot ein structure in order that antibody recognition take place. Analysis of the structural properties of the antigenic determinants revealed th at the neutralizing sites are highly conformation-dependent. None of t he mAb prevented virus binding, suggesting that the epitopes they defi ne are spatially separate from the site(s) responsible for virus attac hment to the cellular receptor. The finding that many of the mAb also did not inhibit virus entry into the cell demonstrated that neutraliza tion of RVFV infectivity by immune antibodies is not dependent on bloc king at the early stages in the viral life cycle.