ABSTRACT
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.
Subject(s)
Antibody-Dependent Enhancement , Dengue Virus/genetics , Dengue Virus/immunology , Dengue/immunology , Viral Envelope Proteins/genetics , Viral Envelope Proteins/immunology , Viral Vaccines/immunology , Amino Acids/chemistry , Animals , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Cell Line , Chimera/genetics , Chimera/immunology , Dengue/virology , Encephalitis Virus, Japanese/genetics , Encephalitis Virus, Japanese/immunology , Humans , K562 Cells , Models, Molecular , Mutation , Protein Structure, Tertiary , Vaccine DevelopmentABSTRACT
Severe dengue is more likely found during secondary heterologous dengue virus (DENV) infection or primary infection of infants born to dengue-immune mothers and led to the hypothesis of antibody-dependent enhancement (ADE). It has been reported that pre-membrane (prM)-reactive antibodies do not efficiently neutralize DENV infection but instead potently promote ADE infection. Meanwhile, these enhancing anti-prM antibodies mainly react with the precursor (pr) peptide. To evaluate the effect of pr gene substitution on neutralization and ADE of DENV infection, a novel chimeric dengue virus (JEVpr/DENV2) was rationally constructed by replacing the DENV pr gene with Japanese encephalitis virus (JEV) pr gene, based on the full-length infectious complementary DNA (cDNA) clone of DENV2 ZS01/01. We found that chimeric JEVpr/DENV2 showed reduced virulence and good immunogenicity. In addition, anti-JEVpr/DENV2 sera showed broad cross-reactivity and efficient neutralizing activity with all four DENV serotypes and immature DENV2 (ImDENV2). Most importantly, compared with anti-DENV2 sera, anti-JEVpr/DENV2 sera showed significantly reduced enhancing activity of DENV infection in K562 cells. These results suggest that the ADE activities could be reduced by replacing the DENV pr gene with JEV pr gene. These findings may help us better understand the pathogenesis of DENV infection and provide a reference for the development of a vaccine against DENV.