Characterization of canine parvovirus (CPV) interactions with 3201 T cells: involvement of GPI-anchored protein(s) in binding and infection.

Binding of canine parvovirus (CPV) to the susceptible feline T cell line 3201 was quantitated by fluorescence-activated cell sorter (FACS) analysis. CPV bound to the cells in a dose-dependent manner, while no binding to the non-permissive MSB-1 avian lymphoma cell line was detected. Binding could be competitively inhibited by addition of excess unlabeled empty capsids, or by pre-incubation of virus with a CPV-specific monoclonal antibody. To characterize the biochemical nature of this binding, live cells were treated with a variety of enzymes prior to use in the binding assay. Treatment with neuraminidase removed a significant proportion of the wild-type virus binding activity, while both proteinase K and phosphatidylinositol-specific phospholipase C (PI-PLC) prevented binding of a non-hemagglutinating (non-HA), non-sialic acid binding mutant to 3201 cells. This suggests that CPV binds to sialic acid expressed on host cells as well as erythrocyte membranes, and that it also binds a protein moiety which is glycosylphosphatidylinositol (GPI)-anchored. The role of these components in CPV infection was also examined by pretreating cells with neuraminidase or PI-PLC prior to inoculating them with either wild-type CPV or the non-hemagglutinating mutant. Neuraminidase treatment had no effect on the ability of CPV to infect the cells, while infectivity was severely compromised by pretreating the cells with either proteinase K or PI-PLC. GPI-anchored proteins on 3201 cells were further characterized by Triton X-114 extraction and reactivity to anti-CRD after PI-PLC treatment.