Sequence analysis and epitope location. A Amino acid sequence alignment of the E5′HVR region of 10 representative FCV strains. The sequences corresponding to the epitopes spanning aa 431-435 (PAGDY) and aa 445-451 (ITTANQY) in Urbana strain are indicated. B to D Physical location of the epitopes. PAGDY epitope is depicted in blue, ITTANQY epitope is depicted in red. B Ribbon representation of the VP1 protein structure. C and D Structural model of the VP1 protein dimer (side and top views, respectively).