FIG. 2.

Neutralizing activities of rabbit sera. Neutralization was measured as either reductions in p24 Gag antigen synthesis in peripheral blood mononuclear cells (A) (18) or reductions in Tat-responsive luciferase reporter gene expression in 5.25.EGFP.Luc.M7 cells (B) (17). The actual percent reductions of p24 Gag antigen at rabbit serum dilutions of 1:4 or 1:12 were used for panel A. Any reduction of p24 less than 50% is indicated by <. Neutralization titers are the dilution at which relative luminescence units (RLU) were reduced by 50% compared to virus control wells after subtraction of background RLU (B). Sera collected before the start of immunization (Pre-immune), 2 weeks after the last DNA immunization (DNA prime), or 2 weeks after one or more protein immunizations (as indicated) were used in both types of neutralization studies. The starting serum dilution was 1:20 for assay against SF162 and 1:10 for assay against JR-FL. NAb, neutralizing antibody.