Residue 301-dependent epitope mapping reveals the molecular basis for GPV/MDPV serotype discrimination by neutralizing monoclonal antibody D1.

Waterfowl parvoviruses (goose parvovirus, GPV; Muscovy duck parvovirus, MDPV; Muscovy duck-origin goose parvovirus, MDGPV; short beak and dwarfism syndrome virus, SBDSV) are significant pathogens in waterfowl. The monoclonal antibody D1 specifically recognizes GPV-serotype parvoviruses (including GPV, SBDSV, and MDGPV) but cannot bind MDPV. Thus, Western blot and indirect immunofluorescence assays confirmed that D1 recognizes a conformational epitope, and residue 301 is critical for its discriminatory binding. Subsequent integrative approaches-combining AlphaFold 3-predicted structural modeling, molecular dynamics simulations, immunofluorescence, and transmission electron microscopy-revealed that VP3 residues 65 and 296 also contribute to the D1 epitope. Position 301 is a conserved divergent site (Asn in GPV, MDGPV, and SBDSV versus Lys in MDPV). Therefore, steric hindrance from lysine (K301) likely explains the inability of D1 to recognize MDPV. These findings elucidate the D1-VP3 binding mode, advancing our understanding of immune recognition mechanisms in waterfowl parvoviruses.