Cell density-dependent expression of viral antigens during persistence of foot-and-mouth disease virus in cell culture.

Immunofluorescence analyses of FMDV persistently infected BHK-21 cells showed that in cultures from early stages of the persistence (passage 15) only about 10% of cells displayed viral antigens, while at late stages (passage 100) no FMDV antigen-positive cells were found. Positive cells at passage 15 displayed a number of structural alterations that did not differ from those observed in lytically infected cells. In these monolayers, and remarkably, clusters of cells that exceeded confluence were associated with an enhancement of cells positive for FMDV antigens, suggesting cell density-dependent expression of viral antigens.

A single amino acid substitution in the capsid of foot-and-mouth disease virus can increase acid lability and confer resistance to acid-dependent uncoating inhibition.

The acid-dependent disassembly of foot-and-mouth disease virus (FMDV) is required for viral RNA release from endosomes to initiate replication. Although the FMDV capsid disassembles at acid pH, mutants escaping inhibition by NH(4)Cl of endosomal acidification were found to constitute about 10% of the viruses recovered from BHK-21 cells infected with FMDV C-S8c1. For three of these mutants, the degree of NH(4)Cl resistance correlated with the sensitivity of the virion to acid-induced inactivation of its infectivity.

Internalization of swine vesicular disease virus into cultured cells: a comparative study with foot-and-mouth disease virus.

We performed a comparative analysis of the internalization mechanisms used by three viruses causing important vesicular diseases in animals. Swine vesicular disease virus (SVDV) internalization was inhibited by treatments that affected clathrin-mediated endocytosis and required traffic through an endosomal compartment. SVDV particles were found in clathrin-coated pits by electron microscopy and colocalized with markers of early endosomes by confocal microscopy.

Susceptibility to viral infection is enhanced by stable expression of 3A or 3AB proteins from foot-and-mouth disease virus.

The foot-and-mouth disease virus (FMDV) 3A protein is involved in virulence and host range. A distinguishing feature of FMDV 3B among picornaviruses is that three non-identical copies are encoded in the viral RNA and required for optimal replication in cell culture. Here, we have studied the involvement of the 3AB region on viral infection using constitutive and transient expression systems.

Subcellular distribution of swine vesicular disease virus proteins and alterations induced in infected cells: a comparative study with foot-and-mouth disease virus and vesicular stomatitis virus.

The intracellular distribution of swine vesicular disease virus (SVDV) proteins and the induced reorganization of endomembranes in IBRS-2 cells were analyzed. Fluorescence to new SVDV capsids appeared first upon infection, concentrated in perinuclear circular structures and colocalized to dsRNA. As in foot-and-mouth disease virus (FMDV)-infected cells, a vesicular pattern was predominantly found in later stages of SVDV capsid morphogenesis that colocalized with those of non-structural proteins 2C, 2BC and 3A.

Productive entry of type C foot-and-mouth disease virus into susceptible cultured cells requires clathrin and is dependent on the presence of plasma membrane cholesterol.

We have characterized the entry leading to productive infection of a type C FMDV in two cell lines widely used for virus growth, BHK-21 and IBRS-2. Inhibition of clathrin-mediated endocytosis by sucrose treatment decreased both cell entry and virus multiplication. Evidence of a direct requirement of clathrin for productive viral entry was obtained using BHK21-tTA/anti-CHC cells, which showed a significant reduction of viral entry and infection when the synthesis and functionality of clathrin heavy chain was inhibited (Tet- cells).

Differential distribution of non-structural proteins of foot-and-mouth disease virus in BHK-21 cells.

Differences in the kinetics of expression and cell distribution among FMDV non-structural proteins (NSPs) have been observed in BHK-21-infected cells. 3D(pol) was the first protein detected by immunofluorescence (1.5 h p.

Hepatocyte growth factor and its receptor are required for malaria infection.

Plasmodium, the causative agent of malaria, must first infect hepatocytes to initiate a mammalian infection. Sporozoites migrate through several hepatocytes, by breaching their plasma membranes, before infection is finally established in one of them. Here we show that wounding of hepatocytes by sporozoite migration induces the secretion of hepatocyte growth factor (HGF), which renders hepatocytes susceptible to infection.