Antibody responses are generated to immunodominant ELK/KLE-type motifs on the nonstructural-1 glycoprotein during live dengue virus infections in mice and humans: Implications for diagnosis, pathogenesis, and vaccine design

Antibodies generated to the purified dengue type 2 virus (D-2V) nonstructural-1 (NS1) protein in mice and rabbits were compared with those generated to this protein in congeneic (H-2 class II) mouse strains and humans after D-2V infections. Unlike the profiles observed with the rabbits, similar antibody reaction profiles were generated by mice and humans with severe D-2V disease (dengue hemorrhagic fever [DHF]/dengue shock syndrome [DSS]). Many of these epitopes contained the core acidic-hydrophobic-basic (tri-amino-acid; ELK-type) motifs present in the positive or negative orientations. Antibody responses generated to these ELK/KLE-type motifs and the epitope LX1 on this protein were influenced by class II molecules in mice during D-2V infections; but these antibodies cross-reacted with human fibrinogen and platelets, as implicated in DHF/DSS pathogenesis. The core LX1 epitope ((113)YSWKTWG(119)), identified by the dengue virus complex-specific monoclonal antibody (MAb) 3D1.4, was prepared so that it contained natural I-A(d)-binding and ELK-type motifs. This AFLX1 peptide, which appropriately displayed the ELK-type and LX1 epitopes in solid-phase immunoassays, generated a similar, but lower, immunodominant anti-ELK-motif antibody reaction in I-A(d)-positive mice, as generated in mice and humans during D-2V infections. These antibody responses were much stronger in the high-responding mouse strains and each of the DHF/DSS patients tested and may therefore account for the association of DHF/DSS resistance or susceptibility with particular class II molecules and autoantibodies, antibody-stimulating cytokines (e.g., interleukin-6), and complement product C3a being implicated in DHF/DSS pathogenesis. These results are likely to be important for the design of a safe vaccine against this viral disease and showed the AFLX1 peptide and MAb 3D1.4 to be valuable diagnostic reagents.