Spike protein E2 of chikungunya virus: a plant-based vaccine exhibited potent immunogenicity in BALB/c mice

Over the last two decades, chikungunya virus (CHIKV) infections have surged worldwide, causing significant suffering. CHIKV E2 gene codes for spike protein E2, essential for virus-host interactions and thus serves as a potential vaccine candidate. We expressed a full-length E2 (S27 African prototype) in both E. coli and Nicotiana tabacum , which triggered an immune response in BALB/c mice. First, E2 was computationally analyzed for PTM patterns and prediction of B-cell and T-cell epitopes. Next, molecular docking of epitopes with MHCs (Class I and II) revealed high affinity, confirmed by Molecular Dynamics Simulation. Then, the chemically synthesized E2-6xHis tag was cloned and expressed in both E. coli and N. tabacum under T7 and CaMV promoters, respectively. E2 was cloned into the pUC57 vector ( E. coli ) and expressed using the pET28a(+) vector in BL21(DE3)pLysS cells, followed by cloning into the pCAMBIA1302 vector and transformation into Agrobacterium tumefaciens . RT-PCR and confocal visualization confirmed the formation of E2 transcripts. Recombinant E2 was purified on Ni-NTA columns and visualized as a protein of ∼49 kDa on SDS PAGE. Finally, E2 was injected into BALB/c mice; neutralizing antibodies, including IgG, were detected as positive in the indirect ELISA, with the highest levels observed at 3 days post-infiltration (3 dpi). Western blot also confirmed E2 expression in E coli and tobacco, and induction of E2-specific antibodies in BALB/c mice. This study presents a promising approach to developing a safe and effective vaccine against chikungunya fever in plants.