FIG 5.

Inhibition of erythrocyte binding to rDBPII expressed on COS-7 cells. Purified total serum IgG from the different prime-boost groups was tested for inhibition of DBPII-erythrocyte binding against a panel of COS-7 cell-expressed DBPII alleles by endpoint dilution. A monolayer of transfected COS-7 cells expressing rDBPII from five different alleles was incubated with the purified serum IgG at different concentrations prior to the addition of human erythrocytes. Binding was scored by counting rosettes in 30 microscopic fields at a magnification of ×200. Percent binding inhibition was determined relative to that of the purified IgG from preimmune sera used as a control. (A) Charts show nonlinear regression curves for the inhibitory activities of the different antibodies against each DBPII allele. Each antibody concentration was tested in triplicate for two independent experiments. (B) Quantitative analysis of anti-DBPII binding inhibition. Bars represent the IC₅₀s of each antibody against individual alleles. (C) Multiple comparisons of anti-DBPII binding-inhibitory responses. The overall inhibitory responses of serum anti-DBPII IgG from each group against all five COS-7-expressed alleles were compared by Bonferroni multiple-comparison adjustment. Bars represent the mean IC₅₀s of each antibody against all the natural alleles. Antibodies were classified into two inhibitory groups (a and b), with a statistically significant difference in inhibitory responses between the groups. Error bars represent standard deviations.