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.