Monoclonal Antibodies which Define Common Epitopes on the Dengue Type-2 Virus Nonstructural-1 (NS1) and Envelope (E) Glycoproteins can Weakly Neutralise these Viruses and Identify Virulent Strains: Implications for Pathogenesis and Vaccines

Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT; Grupo de Investigaciones en Enfermedades Tropicales, Departamento de Ciencias Basicas Medicas, Universidad del Norte, Km5 Antigua via Puerto Colombia, Barranquilla, Colombia

^* To whom correspondence should be addressed. Email: afalconar{at}uninorte.edu.co.

	Abstract

The abilities of monoclonal antibodies (MAbs), which defined sequential epitopes on the dengue virus nonstructural-1 (NS1) glycoproteins, to cross-react with epitopes on the dengue virus envelope (E) glycoproteins were investigated. In this study, some of these MAbs cross-reacted with the dengue type-2 virus (DENV-2) E glycoprotein, and with synthetic peptides representing x-ray crystallographically-confirmed surface-exposed regions on this glycoprotein. MAb 1G5.3 cross-reacted with the flavivirus-conserved 101-WGNGCGLFG-109 fusion sequence, the 273-SSGNL-277 DENV-2 hinge-region sequence and the 156-GKHGKEIKIT-165 sequence of virulent DENV-2 strains. MAb 1G5.4-A1-C3 cross-reacted with the 67-NTTTESRCPT-76 and 156-GKHGKEIKIT-165 sequences of virulent DENV-2 strains, the 338-EIMDLDNRHV-347 sequence from a highly virulent DENV-2 (M2) strain, and two epitopes on a virulent DENV-3 strain (288-KMDKLELKG-296 and 323-RVEYRGEDAP-332), which all contained its target ELK/KLE-type motifs (underlined). These MAbs showed reduced cross-reactions with the corresponding sequences from weakly pathogenic strains of all four DENV serotypes, and had either no (MAb 1G5.4-A1-C3) or weak (MAb 1G5.3) neutralising activity against them. MAb 1G5.3 more strongly neutralised DENV-2 strains with higher pathogenic capacities, while MAb 1G5.4-A1-C3 showed increasing neutralising titers against the virulent DENV-3 strain, and the moderately virulent and the highly virulent (M2) DENV-2 strains. These cross-reactions with the E glycoprotein accord with the observation that MAb 1G5.3 caused a dramatic and lethal antibody-enhanced replication (AER) of a DEN-2V in vivo. Together with in vivo AER studies of these DENV strains using MAb 1G5.4-A1-C3, these results may account for the increased pathogenic capacities of such strains, which is likely to have important implications for pathogenesis and vaccines.