Further development and testing in larger numbers of specimens is therefore necessary to access the potential use of pwLAMP as a simple and rapid point of care diagnostic test for BU. A Human PrM Antibody That Recognizes a Novel Cryptic Epitope on Dengue E Glycoprotein Dengue virus (DENV) is a major mosquito-borne pathogen infecting up to 100 million people each year; so far no effective treatment or vaccines are available. Recently, highly cross-reactive and infection-enhancing pre-membrane (prM)-specific antibodies were found to dominate the anti-DENV immune response in humans, raising concern over vaccine candidates that contain native dengue prM sequences. In this study, we have isolated a broadly cross-reactive prM-specific antibody, D29, during a screen with a non-immunized human Fab-phage library against the four serotypes of DENV. The antibody is capable of restoring the infectivity of virtually non-infectious immature DENV (imDENV) in FcγR-bearing K562 cells. Remarkably, D29 also cross-reacted with a cryptic epitope on the envelope (E) protein located to the DI/DII junction as evidenced by site-directed mutagenesis. This cryptic epitope, while inaccessible to antibody binding in a native virus particle, may become exposed if E is not properly folded. These findings suggest that generation of anti-prM antibodies that enhance DENV infection may not be completely avoided even with immunization strategies employing E protein alone or subunits of E proteins. Dengue virus (DENV) is a flavivirus with four related but antigenically distinct serotypes (DENV1-4). It infects approximately 50-100 million people each year, of which 500,000 people exhibit the life-threatening form of severe dengue -dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) [1] . The current lack of treatment or licensed vaccine means dengue poses a serious public health threat [2] . Infection by one serotype of DENV confers lifelong immunity against the homologous serotype, but only limited crossprotection to the remaining three serotypes [3, 4] . The presence of cross-reactive, non-neutralizing antibodies generated during a primary infection has been suggested to enhance the pathogenicity of subsequent infections via the process of antibody-dependent enhancement (ADE) [5] . A successful and safe vaccine candidate must therefore elicit a protective long-lasting immune response to all four serotypes [4, [6] [7] [8] .