Structural Determinants of Tissue Tropism and In Vivo Pathogenicity for the Parvovirus Minute Virus of Mice

Received 11 March 2005/Accepted 25 May 2005 Two strains of the parvovirus minute virus of mice (MVM), the immunosuppressive (MVMi) and the prototype (MVMp) strains, display disparate in vitro tropism and in vivo pathogenicity. We report the crystal structures of MVMp virus-like particles (MVMpb) and native wild-type (wt) empty capsids (MVMpe), determined and refined to 3.25 and 3.75 A resolution, respectively, and their comparison to the structure of MVMi, also refined to 3.5 A resolution in this study. A comparison of the MVMpb and MVMpe capsids showed their structures to be the same, providing structural verification that some heterologously expressed parvovirus capsids are indistinguishable from wt capsids produced in host cells. The structures of MVMi and MVMp capsids were almost identical, but local surface conformational differences clustered from symmetry-related capsid proteins at three specific domains: (i) the icosahedral fivefold axis, (ii) the “shoulder” of the protrusion at the icosahedral threefold axis, and (iii) the area surrounding the depression at the icosahedral twofold axis. The latter two domains contain important determinants of MVM in vitro tropism (residues 317 and 321) and forward mutation residues (residues 399, 460, 553, and 558) conferring fibrotropism on MVMi. Furthermore, these structural differences between the MVM strains colocalize with tropism and pathogenicity determinants mapped for other autonomous parvovirus capsids, highlighting the importance of common parvovirus capsid regions in the control of virus-host interactions. Viral tissue tropism and pathogenesis are highly dependent on well-orchestrated and defined interactions that occur between the viral pathogen and its host. The single-stranded Parvoviridae infect a broad range of natural hosts that include invertebrates and mammals, and pathogenic members cause serious disease in the young and immunocompromised adults. However, disparities in tissue tropism and in vivo pathogenicity can be observed between highly homologous strains for several members of the Parvoviridae. The combination of molecular analysis with disease outcomes for a number of strains of the Aleutian mink disease parvovirus (AMDV) (9, 10), canine parvovirus (CPV), and feline panleukopenia virus (FPV) (46, 61, 62), and for porcine parvovirus (PPV) (8, 41), has provided