Research Projects

Antibody-dependent enhancement (ADE) is the major safety concern for developing vaccines against Dengue virus (DENV) due to the complexity of genetically similar four serotypes (DENV 1-4) (1). ADE is a phenomenon by which cross-reactive (CR) antibodies raised during primary infection against one serotype of DENV can enhance, instead of protect, subsequent secondary heterologous serotype infection (2). The CR antibodies form a complex with heterologous serotypes, enabling their entry into Fc-gamma receptor-bearing monocytes and macrophages, leading to more severe hemorrhagic (DHF) and shock syndrome (DSS). During the last decade, it has become evident that the ADE-prone CR antibodies majorly target epitopes on DENV envelope (E) and Pre-membrane (PrM) proteins. Recent studies have demonstrated that DENV live attenuated vaccines (LAVs) have an inherent risk of ADE as they primarily elicit antibodies against PrM and fusion loop (FL) epitopes of E Proteins (3). This raises the question, as >50% of the Indian population is immune to dengue, how preexisting immunity will LAVs influence the vaccine outcome? Thus, this scenario necessitates rethinking current dengue vaccine design approaches. In this context, our group recently reported the development of a multi-subunit DENV DNA vaccine that was generated by coming in tandem E-protein domain III (ED III) of DENV 1-4 and DENV-2 non-structural gene 1 (NS1) as these proteins are the major target of serotype-specific highly neutralizing antibodies and can generate robust T cell responses, respectively [PCT/IB2022/062891]. We reported that vaccination of mice with this construct induced pan-serotype neutralizing antibodies and antigen-specific T-cell responses. Assaying of intracellular IFN-γ staining, immunoglobulin IgG2(a/c)/IgG1 ratios suggest a strong Th1-dominant immune response. Moreover, the passive transfer of immune serum-protected AG129 mice was challenged with a virulent, non-mouse-adapted DENV-2 strain (4). Further, the DENV-DNA vaccine optimization study was conducted to improve the immunogenicity of DNA vaccines by using adjuvanted nano plasmids and encapsulating them with lipid nanoparticles (LNPs). Immunization of nanoDNA-LNP in mice robustly increased antigen-specific IgG titers twofold, even without electrophoration (unpublished data). The proposed study primarily investigates the ADE competence of the DENV nanoDNA-LNP vaccine using in-house established mouse models. Further, we characterize the functional role of vaccine-induced cellular immunity in disease protection or pathogenesis against DENV and other related flaviviruses. Finally, we examine various immune signatures in vaccinated mice blood and lymph nodes to identify protective immune biomarkers.