To isolate hMAbs specific for DENV from donor 033, positive B cell cultures were cloned by limiting dilution and 16 clones were isolated and expanded. All the hybridomas produced IgG1 with the single exception DV20.10, which was IgG3 (Table S2 ). To identify antibodies that bound to structural viral antigens, the hMAbs were tested for binding to purified DENV3 particles in ELISA. Fourteen out of 16 hMAbs bound to DENV3 virus. Of the 14 hMAbs that bound to DENV3 particles, 13 cross-reacted with all four dengue serotypes dengue complex reactiveand one antibody (hMAb DV51.3) bound to serotypes 1 and 3, but not 2 and 4 (dengue sub complex reactive) (Table S2 ). Dengue virions were solubilized and subjected to Western blot analysis to identify the viral structural proteins recognized by hMAbs. Ten of the 14 hMAbs bound to prM and only a single hMAb (DV64.3) bound to E protein (Figure 1 ). Three hMAbs did not bind to viral antigens by Western blot, although they reacted with DENV3 virion. The 16 hMAbs were also tested for binding to rE protein in ELISA. Only hMAb DV64.31, which had also recognized E protein by Western Blot, bound to rE protein from all 4 DENV serotypes (Table S2) .