Molecular dynamics study on the stability of foot-and-mouth disease virus particle in salt solution

The poor thermostability of the Foot-and-mouth disease virus (FMDV) vaccines is a huge challenge since it requires cold chain transportation and thus significantly increases the cost. To study the theoretical basis for the enhanced stability of FMDV vaccines with the addition of bivalent metal cations in solution, in this work, molecular dynamics simulations were performed between two adjacent protein subassemblies of FMDV capsid under three different solvent environments, including salt-free aqueous solution, CaCl2 solution and CuCl2 solution. Besides analysis of the adsorption properties of Ca2+ and Cu2+ ions, umbrella sampling method was used to calculate the potential of mean force between the protein subassemblies. Moreover, molecular mechanics/Poisson–Boltzmann surface area method was used to calculate the change of free energies with the addition of metal cations. The results suggest that the system in bivalent metal cationic solutions, especially CuCl2 solution, exhibited stronger interactions between protein subassemblies, mainly through manipulation of the electrostatic interactions raised from polar residues on protein molecules, and thus result in better stabilities of the FMDV capsid structure. With this work, we hope to shed some light on the molecular mechanism of the structure manipulation of the virus capsid structure through regulation of the micro-environments.