Identification of the sialic acid structures recognized by minute virus of mice and the role of binding affinity in virulence adaptation

Sialic acid binding is required for infectious cell surface receptor recognition by parvovirus minute virus of mice (MVM). We have utilized a glycan array consisting of similar to 180 different carbohydrate structures to identify the specific sialosides recognized by the prototype (MVMp) and immunosuppressive (MVMi) strains of MVM plus three virulent mutants of MVMp, MVMp-I362S, MVMp-K368R, and MVMp-I362S/K368R. All of the MVM capsids specifically bound to three structures with a terminal sialic acid-linked alpha 2-3 to a common Gal beta 1-4GlcNAc motif: Neu5Ac alpha 2-3Gal beta 1-4GlcNAc beta 1-4Gal beta 1-4GlcNAc (3 ' SiaLN-LN), Neu5Ac alpha 2-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc (3 ' SiaLN-LN-LN), and Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4(Fuc alpha 1-3)-GlcNAc(sLe(x)-Le(x)-Le(x)). In addition, MVMi also recognized four multisialylated glycans with terminal alpha 2-8 linkages: Neu5Ac alpha 2-8Neu5Ac alpha 2-8Neu5Ac alpha((Sia)(3)), Neu5Ac alpha 2-8Neu5Ac alpha 2-3Gal beta 1-4Glc(GD3), Neu5Ac alpha 2-8Neu5Ac alpha 2-8Neu5Ac alpha 2-3Gal beta 1-4Glc(GT3), and Neu5Ac alpha 2-8Neu5Ac alpha 2-3(GalNAc alpha 1-4)Gal beta 1-4Glc(GD2). Interestingly, the virulent MVMp-K368R mutant also recognized GT3. Analysis of the relative binding affinities using a surface plasmon resonance biospecific interaction (BIAcore) assay showed the wild-type MVMp and MVMi capsids binding with higher affinity to selected glycans compared with the virulent MVMp mutants. The reduced affinity of the virulent MVMp mutants are consistent with previous in vitro cell binding assays that had shown weaker binding to permissive cells compared with wild-type MVMp. This study identifies the sialic acid structures recognized by MVM. It also provides rationale for the tropism of MVM for malignant transformed cells that contain sLe(x) motifs and the neurotropism of MVMi, which is likely mediated via interactions with multisialylated glycans known to be tumor cell markers. Finally, the observations further implicate a decreased binding affinity for sialic acid in the in vivo adaptation of MVMp to a virulent phenotype.