Engineered dengue virus NS1 mRNA-lipid nanoparticle induces therapeutic IgG production that lacks autoantibody activity and neutralizes NS1 entry in liver cells.

Dengue virus remains a significant public health concern in tropical and subtropical regions, with vaccine development facing considerable challenges. A major obstacle is antibody-dependent enhancement (ADE), which limits the clinical translation of vaccine candidates utilizing structural proteins as antigens. To circumvent this issue, we designed mRNA-based vaccine candidates targeting the non-structural protein NS1. Given the propensity of NS1's C-terminal region to induce autoantibodies, we focused on N-terminal half of the protein. One antigen comprised a truncated NS1 (amino acids 1-270), while the second was chimeric featuring truncated Dengue NS1 at the N-terminus and the C-terminal region (amino acids 271-352) of Japanese encephalitis virus (JEV) NS1. Additionally, a lysine-to-arginine substitution at position 116 (Lys116Arg) was introduced to mitigate the risk of endothelial cell autoantibody formation. All mRNAs successfully expressed their respective antigens in Huh7 cells, with both full-length NS1 and chimeric NS1 being secreted, whereas the truncated NS1 remained intracellular. mRNAs were encapsulated in lipid nanoparticles (LNPs) and administered to Balb/C mice. The native and the chimeric antigens elicited immune responses, with IgG profiling indicating a predominant IgG2a response and displayed reduction in viral load in virus challenge studies. Notably, sera from mice immunized with chimeric NS1 did not cross-react with endothelial cells, unlike sera from those immunized with full-length NS1 and neutralized the entry of NS1 in liver cells efficiently. These findings suggest that the chimeric NS1 antigen is both immunogenic and less likely to trigger autoantibody-mediated adverse effects, highlighting its potential as a safer therapeutic dengue vaccine.