Identification of Equine Lactadherin-derived Peptides That Inhibit Rotavirus Infection via Integrin Receptor Competition

Background: Human milk lactadherin protects breastfed infants against symptomatic rotavirus infections. Results: A 20-aa peptide (namely pDGE-RGD) derived from equine lactahderin inhibits human rotavirus infectivity. Conclusion: pDGE-RGD interacts specifically with 21 integrin, thus hindering the rotavirus-cell attachment process. Significance: The discovery of the pDGE-RGD peptide may prove useful in the development of inhibitors of receptor recognition by rotavirus or other integrin-using viruses. Human rotavirus is the leading cause of severe gastroenteritis in infants and children under the age of 5 years in both developed and developing countries. Human lactadherin, a milk fat globule membrane glycoprotein, inhibits human rotavirus infection in vitro, whereas bovine lactadherin is not active. Moreover, it protects breastfed infants against symptomatic rotavirus infections. To explore the potential antiviral activity of lactadherin sourced by equines, we undertook a proteomic analysis of milk fat globule membrane proteins from donkey milk and elucidated its amino acid sequence. Alignment of the human, bovine, and donkey lactadherin sequences revealed the presence of an Asp-Gly-Glu (DGE) (21) integrin-binding motif in the N-terminal domain of donkey sequence only. Because integrin (21) plays a critical role during early steps of rotavirus host cell adhesion, we tested a minilibrary of donkey lactadherin-derived peptides containing DGE sequence for anti-rotavirus activity. A 20-amino acid peptide containing both DGE and RGD motifs (named pDGE-RGD) showed the greatest activity, and its mechanism of antiviral action was characterized; pDGE-RGD binds to integrin (21) by means of the DGE motif and inhibits rotavirus attachment to the cell surface. These findings suggest the potential anti-rotavirus activity of equine lactadherin and support the feasibility of developing an anti-rotavirus peptide that acts by hindering virus-receptor binding.