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J Virol, May 1998, p. 4022-4031, Vol. 72, No. 5
Departments of Macromolecular
Structure1 and
Molecular and Cell
Biology,2 Centro Nacional de
Biotecnología (CSIC), Campus Universidad Autónoma, 28049 Madrid, Spain
Received 11 November 1997/Accepted 3 February 1998
The intracellular assembly of the transmissible gastroenteritis
coronavirus (TGEV) was studied in infected swine testis (ST) cells at
different postinfection times by using ultrathin sections of
conventionally embedded infected cells, freeze-substitution, and
methods for detecting viral proteins and RNA at the electron microscopy
level. This ultrastructural analysis was focused on the identification
of the different viral components that assemble in infected cells, in
particular the spherical, potentially icosahedral internal core, a new
structural element of the extracellular infectious coronavirus recently
characterized by our group. Typical budding profiles and two types of
virion-related particles were detected in TGEV-infected cells. While
large virions with an electron-dense internal periphery and a clear
central area are abundant at perinuclear regions, smaller viral
particles, with the characteristic morphology of extracellular virions
(exhibiting compact internal cores with polygonal contours) accumulate
inside secretory vesicles that reach the plasma membrane. The two types
of virions coexist in the Golgi complex of infected ST cells. In
nocodazole-treated infected cells, the two types of virions coexist in
altered Golgi stacks, while the large secretory vesicles filled with
virions found in normal infections are not detected in this case.
Treatment of infected cells with the Golgi complex-disrupting agent
brefeldin A induced the accumulation of large virions in the cisternae
that form by fusion of different membranous compartments. These data, together with the distribution of both types of virions in different cellular compartments, strongly suggest that the large virions are the
precursors of the small viral particles and that their transport
through a functional Golgi complex is necessary for viral maturation.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Two Types of Virus-Related Particles Are Found
during Transmissible Gastroenteritis Virus Morphogenesis
*
Corresponding author. Mailing address: Department of
Macromolecular Structure, Centro Nacional de Biotecnología
(CSIC), Campus Universidad Autónoma, Cantoblanco, 28049 Madrid,
Spain. Phone: 341-5854509. Fax: 341-5854506. E-mail:
jlcarrascosa{at}cnb.uam.es.
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