Journal of Virology, February 2000, p. 1919-1930, Vol. 74, No. 4
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853
Received 11 May 1999/Accepted 18 November 1999
Canine parvovirus (CPV) is a small, nonenveloped virus that is a
host range variant of a virus which infected cats and changes in the
capsid protein control the ability of the virus to infect canine cells.
We used a variety of approaches to define the early stages of cell
entry by CPV. Electron microscopy showed that virus particles
concentrated within clathrin-coated pits and vesicles early in the
uptake process and that the infecting particles were rapidly removed
from the cell surface. Overexpression of a dominant interfering mutant
of dynamin in the cells altered the trafficking of capsid-containing
vesicles. There was a 40% decrease in the number of CPV-infected cells
in mutant dynamin-expressing cells, as well as a ~40% decrease in
the number of cells in S phase of the cell cycle, which is required for
virus replication. However, there was also up to 10-fold more binding
of CPV to the surface of mutant dynamin-expressing cells than there was
to uninduced cells, suggesting an increased receptor retention on the
cell surface. In contrast, there was little difference in virus
binding, virus infection rate, or cell cycle distribution between
induced and uninduced cells expressing wild-type dynamin. CPV particles colocalized with transferrin in perinuclear endosomes but not with
fluorescein isothiocyanate-dextran, a marker for fluid-phase endocytosis. Cells treated with nanomolar concentrations of bafilomycin A1 were largely resistant to infection when the drug was added either
30 min before or 90 min after inoculation, suggesting that there was a
lag between virus entering the cell by clathrin-mediated endocytosis
and escape of the virus from the endosome. High concentrations of CPV
particles did not permeabilize canine A72 or mink lung cells to
-sarcin, but canine adenovirus type 1 particles permeabilized both
cell lines. These data suggest that the CPV entry and infection pathway
is complex and involves multiple vesicular components.
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