Abstract
Infectious bursal disease virus (IBDV) poses a significant threat to the poultry industry. Viral protein 2 (VP2), the major structural protein of IBDV, has been subjected to frequent mutations that have imparted tremendous genetic diversity to the virus. To determine how amino acid mutations may affect the virulence of IBDV, we built a structural model of VP2 of a very virulent strain of IBDV identified in China, vvIBDV Gx, and performed a molecular dynamics simulation of the interaction between virulence sites. The study showed that the amino acid substitutions that distinguish vvIBDV from attenuated IBDV (H253Q and T284A) favor a hydrophobic and flexible conformation of β-barrel loops in VP2, which could promote interactions between the virus and potential IBDV-specific receptors. Population sequence analysis revealed that the IBDV strains prevalent in East Asia show a significant signal of positive selection at virulence sites 253 and 284. In addition, a signal of co-evolution between sites 253 and 284 was identified. These results suggest that changes in the virulence of IBDV may result from both the interaction and the co-evolution of multiple amino acid substitutions at virulence sites.
Highlights
Infectious bursal disease virus (IBDV) is an avian virus that infects the bursa of Fabricius in young chickens
Several viral infection studies have shown that the hypervariable region of Viral protein 2 (VP2) is involved in virulence changes and that the amino acid residues at positions 253 and 284 of VP2 are the main determinants of the virulence and cell tropism of IBDV [14,15]
We built a pseudo-atomic structural model of VP2 from vvIBDV Gx, a very virulent strain of IBDV identified in China, and characterized the interaction of two virulence sites, Q253 and A284, by molecular dynamics simulation to reveal the molecular basis of IBDV virulence
Summary
Infectious bursal disease virus (IBDV) is an avian virus that infects the bursa of Fabricius in young chickens. Several viral infection studies have shown that the hypervariable region of VP2 is involved in virulence changes and that the amino acid residues at positions 253 and 284 of VP2 are the main determinants of the virulence and cell tropism of IBDV [14,15]. Recent virulence and immunology studies have shown that the amino acid residue at position 253 is critical to the alteration of virulence of IBDV, while the residues at positions 279 and 284 are not directly related to viral virulence but are involved in cell adaptability and replication efficiency [19,20]. We performed a population sequence analysis of the hypervariable region of VP2 to analyze the positive selection and co-evolution of virulence sites during the genetic diversification of IBDV These results could shed new light on the molecular mechanisms of IBDV virulence and evolution
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