Design and evaluation of a multi-epitope vaccine for COVID-19: an in silico approach

Corona virus disease-19 (COVID-19) is an evolving global disease which has burst into 2019. SARS-CoV-2 infects human cells through recognition of and binding to angiotensin converting enzyme-2 (ACE2) through the spike (S) glycoprotein. Spike is an immunogenic protein that can elicit immune responses. Multi-epitope vaccines are novel and efficient class of vaccines which are designed by linking the B and T cells. These epitopes stimulate both humoral and cellular immunity.

Based on bioinformatics online tools, appropriate epitopes of S protein were selected, linked together via suitable linkers, a TLR4 binding adjuvant was added, and a multi-epitope construct was constructed. The 3D model of the construct was predicted, refined, and validated. The antigenicity, allergenicity, solubility, and physico-chemical properties of vaccine were checked. The B cell conformational epitopes and IFN-γ inducing parts were detected. The adjuvant and TLR4 binding were evaluated by docking and protein-protein complex stability was assessed by elastic-mode analysis. The coding sequence of the vaccine construct was optimized and sub-cloned in expression vector through an in silico approach. Finally, the structure, energy, and stability of vaccine coding mRNA were evaluated.

Ten continuous B cell epitopes, 9 T helper epitopes, and 8 CTL epitopes were chosen. The results showed that multi-epitope vaccine is a stable and soluble protein which can stimulate humoral and cellular immunity. Besides, the vaccine could stimulate immunity without inducing allergenicity in human body.

Finally, the vaccine can bind the TLR4 appropriately and can be expressed by a recombinant vector. The designed multi-epitope vaccine against COVID-19 could be considered as a suitable candidate for experimental studies.