Enhancement of DENV2 infection was observed for all antibodies, with the exception of the non-DENV specific antibody. All the DENV-specific antibodies caused an approximately 20-fold increase in infection compared with IgG control (Fig 7B) . As D29 Fab-IgG is non-neutralizing, it was capable of enhancing infection of prM-containing virus in the preparation for the entire range of concentrations tested.