-Foot-and-mouth disease virus (FMDV) was the first animal virus identified. Since then, FMDV has become a model system in animal virology and a considerable amount of information on its structure, biology and vaccinology has been obtained. However, the disease that this virus produces (FMD) still constitutes one of the main animal health concerns. In this review, we have attempted to summarise the state of the knowledge in different basic and applied areas of FMDV research, with emphasis on those aspects relevant to the control of the disease. FMDV / structure / immunity / vaccine / variability / diagnosisRésumé -Le virus de la fièvre aphteuse : un virus connu de longue date, qui demeure une menace. Le virus de la fièvre aphteuse a été le premier virus animal identifié. Depuis lors, il est devenu un système modèle en virologie animale, et une quantité importante d'informations sur sa structure, sa biologie et sa vaccinologie a été obtenue. Cependant la maladie provoquée par ce virus constitue encore une inquiétude majeure en santé animale. Dans cette revue, nous avons tenté de résumer l'état des connaissances dans différents domaines de recherche, à la fois fondamentaux et appliqués, sur le virus de la fièvre aphteuse, en mettant l'accent sur les aspects relatifs au contrôle de la maladie. virus de la fièvre aphteuse / immunité / vaccin / variabilité / diagnostic

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.i.), showing a perinuclear distribution. At 2-2.5 h p.i., 2B, 2C, 3B and 3C were detected, mostly exhibiting a punctuated, scattered pattern, while 3A and 3D(pol) appeared concentrated at one side of the nucleus. This distribution was exhibited by all the NSPs from 3 h p.i., being 2C and, to a lesser extent, precursors 2BC and 3ABBB, the only proteins detected by Western blotting at that infection time. From 4 h p.i., all mature NSPs as well as precursors 2BC, 3ABBB, 3ABB, 3AB and 3CD(pol) were detected by this technique. In spite of their similar immunofluorescence patterns, 2C and 3A co-localized partially by confocal microscopy at 3.5 h p.i., and 3A, but not 2C, co-localized with the ER marker calreticulin, suggesting differences in the distribution of these proteins and/or their precursors as infection proceeded. Transient expression of 2C and 3AB resulted in punctuated fluorescence patterns similar to those found in early infected cells, while 3A showed a more diffuse distribution. A shift towards a fibrous pattern was noticed for 3ABB, while a major change was observed in cells expressing 3ABBB, which displayed a perinuclear fibrous distribution. Interestingly, when co-expressed with 3D(pol), the pattern observed for 3ABBB fluorescence was altered, resembling that exhibited by cells transfected with 3AB. Transient expression of 3D(pol) showed a homogeneous cell distribution that included, as determined by confocal microscopy, the nucleus. This was confirmed by the detection of 3D(pol) in nuclear fractions of transfected cells. 3D(pol) and its precursor 3CD(pol) were also detected in nuclear fractions of infected cells, suggesting that these proteins can directly interact with the nucleus during FMDV infection.

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. These results suggest that assembly of capsid proteins is associated to the replication complex. Confocal microscopy showed a decreased fluorescence to ER markers (calreticulin and protein disulfide isomerase), and disorganization of cis-Golgi gp74 and trans-Golgi caveolin-1 markers in SVDV- and FMDV-, but not in vesicular stomatitis virus (VSV)-infected cells. Electron microscopy of SVDV-infected cells at an early stage of infection revealed fragmented ER cisternae with expanded lumen and accumulation of large Golgi vesicles, suggesting alterations of vesicle traffic through Golgi compartments. At this early stage, FMDV induced different patterns of ER fragmentation and Golgi alterations. At later stages of SVDV cytopathology, cells showed a completely vacuolated cytoplasm containing vesicles of different sizes. Cell treatment with brefeldin A, which disrupts the Golgi complex, reduced SVDV (approximately 5 log) and VSV (approximately 4 log) titers, but did not affect FMDV growth. Thus, three viruses, which share target tissues and clinical signs in natural hosts, induce different intracellular effects in cultured cells.