Mining envelope domain III of Dengue virus for recombinant tetravalent DNA vaccine candidate from Nepalese samples

Abstract

Dengue is caused by a single stranded positive sense RNA flavivirus, Dengue virus (DENV), which is transmitted predominantly by female mosquito vectors Aedes aegypti, Aedes albopictus. It leads to disease in human from mild dengue fever (DF) to a life threatening, severe Dengue Hemorrhagic Fever (DHF) or Dengue Shock Syndrome (DSS). All dengue viruses (serotypes 1-4) can infect human. Once infected the patients develops immunity against all serotype for limited time period. Risk of secondary infection increases as immunity against other serotype decreases. There is higher risk of development of severe dengue during secondary infection due to Antibody Dependent Enhancement (ADE). ADE results in enhanced virus entry and greater virus replication which lead to severe dengue. It also one of the hurdles in the vaccine development and acceptance. Early diagnosis can help patients to get necessary treatment in time and effective preventive measures should be taken to reduce the dengue cases and mortality due to dengue fever. So there is an urgent need for a dengue vaccine that induces long-lasting, simultaneous protection to all four serotypes of dengue while avoiding the immune enhancement of viral infection. For the dengue vaccine development the Envelope region of dengue virus has been widely studied. Envelope region contains three domains, among Domains I, II and III of envelope region, Domain III remain choice of interest due to its reduced risk of Antibody Dependent Enhancement (ADE) in dengue infection. Envelope Domain III (EDIII) of the dengue envelope protein has been implicated in receptor binding, and is also the target of specific neutralizing antibodies thus EDIII has emerged as a promising region for a vaccine candidate. Considering EDIII as candidate instead of whole envelope might address the solution to existing problems of dengue vaccine in use and it might eliminate the risk of ADE. In the present study, we aim to identify all four serotypes and amplify serotype specific EDIII region. Further we aim to fuse EDIII region of different dengue virus serotypes and construct recombinant bivalent construct and tetravalent construct. Then we aim to recombine the construct into a mammalian expression vector to make a single recombinant tetravalent ED III dengue vaccine construct for its subsequent use as a novel vaccine candidate because it is exposed to the surface and thus becomes the primary target for antibody-mediated neutralization. Keywords: Dengue, Envelope Domain III, Antibody Dependent Enhancement, Recombinant DNA, Vaccine