Following isolation from the human non-immune Fab-phage library by panning against the 4 serotypes of DENV sequentially (Fig. S1 ), D29 Fab-IgG was converted into full length human IgG1 (Materials and Methods S1). To ensure the antibody was specific for DENV viral proteins, ELISA and IFA were performed with all 4 serotypes of DENV grown in C6/36 and Vero cell lines. D29 Fab-IgG reacted with infected cells from DENV1-4 without crossreaction to the non-infected cell controls, indicating that the determinant for D29 Fab binding is indeed viral and not host (Fig. 1A , B, C).