FIG 3.

Epitopes and IgG avidities of eluted GR Abs after secondary immunization, compared with total serum IgG avidity after primary and secondary immunization. (A and B) Day 42 serum from vaccinee ID 20 after secondary DENV2 immunization was depleted with WNV antigen; GR anti-E Abs were eluted from an NC membrane as described in Materials and Methods and subjected to epitope mapping by DB assay (A) and capture ELISA using WT and mutant VLPs containing key FL mutations (B) (21). (C to E) Avidity indices of eluted GR anti-E Abs and total serum were determined as described in Materials and Methods. Vaccinees were subgrouped by sequence of immunization, including DENV4 → DENV1 (ID1, ID4, ID5, and ID6 [D]), DENV2 → DENV1 (ID11 and ID12 [E]), and DENV4 → DENV2 (ID16, ID19, and ID20 [F]). A pooled DENV-immune human serum was used to verify that comparable amounts of DENV were loaded in the virion ELISA (C). Data are means and standard deviations of duplicates from one of two experiments (A to C) or means and standard deviations of duplicates from two experiments for all individuals within each subgroup (D to E). The P values were determined by a two-tailed Mann-Whitney test.