Antibody-dependent enhancement (ADE) of dengue virus: Identification of the key amino acid that is vital in DENV vaccine research

Background: The antibody-dependent enhancement (ADE) of dengue virus (DENV) has critically restricted vaccine development. Prior research suggested pr4 as the probable ADE epitope of DENV. Methods: Chimeric DENV was constructed by replacing the DENV pr4 gene with the corresponding Japanese encephalitis virus (JEV) gene to determine whether it can reduce ADE activities. An alanine scanning method and bioinformatics analysis were utilized to identify the amino acid of pr4 that was crucial as an ADE epitope. Results: Chimeric virus reduced ADE and virulence. The amino acids at the following locations on the mutant peptides showed significantly reduced binding ability to prM antibody: pr4.5 (position 5 - leucine), pr4.6 (position 6 - leucine), pr4.7 (position 7 - phenyalanine) and pr4.16 (position 16 - cysteine). The four amino acids had formed a pocket-like structure, which could increase the possibility of binding to an antibody. Conclusions: ADE activities could be reduced by replacing the DENV pr4 gene with the corresponding JEV gene. Leucine at position 5, leucine at position 6, phenyalanine at position 7 and cysteine at position 16 were the key amino acid sites in the ADE response of DENV. The occurrence of ADE can potentially be reduced by the replacement of key amino acids, hence highlighting its possible contribution to dengue vaccine design, paving a way for future vaccine research.