Competitive Inhibition of RANTES-ELISA with V3 loop and hbs-wt peptides. An ELISA format similar to that in Figure 5 was used to measure RANTES binding to heparin and compare the ability of various peptides to compete with this binding. A fixed concentration of 5 nM RANTES was mixed with various concentrations of competitors before addition to BSA-heparin coated plates. RANTES was then detected by an anti-RANTES mAb, a biotinylated secondary antibody and streptavidin conjugated to horseradish peroxidase. Percentage inhibition of binding was determined by dividing the absorbance at each peptide concentration by the absorbance at 0 nM of the peptide.