HSV2 Neutralizing Antibodies and gD-Specific Binding Antibodies

Sera underwent heat inactivation and were assayed for HSV2 neutralizing activity by a plaque-reduction assay in Vero cells, using HSV2 strain 333 [13]. Results are reported as the fold dilution of serum that inhibited 50% of plaque formation (IC₅₀) and were calculated by nonlinear regression. A positive neutralizing antibody response was defined as a ≥4-fold increase in titer from baseline to 30 days after the third dose. The HSV gD–specific antibody titer was measured in light units (LU), using a luciferase immunoprecipitation assay [14].