A Human PrM Antibody That Recognizes a Novel Cryptic Epitope on Dengue E Glycoprotein

Annie Hoi Yi Chan,Angeline Pei Chiew Lim,Eng Eong Ooi,Hwee Cheng Tan,Angelia Yee Chow,Nicole J Moreland,Subhash G Vasudevan,Brendon J Hanson,Paul A Macary,Shee Mei Lok

doi:10.1371/journal.pone.0033451

Annie Hoi Yi Chan, Angeline Pei Chiew Lim + Show 8 more

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https://doi.org/10.1371/journal.pone.0033451

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Abstract

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.

Highlights

Dengue virus (DENV) is a flavivirus with four related but antigenically distinct serotypes (DENV1-4)
Binding Specificity and Affinity of D29 Fab-IgG 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 Immunofluorescent Assay (IFA) were performed with all 4 serotypes of DENV grown in C6/36 and Vero cell lines

Summary

Introduction

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]. A successful and safe vaccine candidate must elicit a protective long-lasting immune response to all four serotypes [4,6,7,8]

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