Moreover, position 300 and adjacent residues at 299 and 301 in VP2 were separately involved in adapting CPV-2 binding to the canine transferrin receptor; a change in CPV-2VP2 residue 299 (Gly ⟶ Glu) caused the virus to lose its binding ability to canine TfR and 299-Glu severely restricts infection of CPV-2 in dog cells [23–25]. The gene discussed is TFRC; the disease is infection.