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Short hairpin RNA targeted to the highly conserved 2B nonstructural protein coding region inhibits replication of multiple serotypes of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) is one of the most contagious agents of animals. Recent disease outbreaks in FMD-free countries have prompted the development of new control strategies that could improve the levels of protection against this virus. We have delivered a plasmid expressing a short hairpin RNA (shRNA) directed against a highly conserved sequence in the 2B nonstructural protein coding region of FMDV RNA to porcine cells. After virus infection, these cells showed a significant reduction in the synthesis of viral RNA and proteins, as well as a decrease in virus yield when compared to control cells. The antiviral effect was sequence specific and not attributable to induction of the interferon pathway. Since FMDV is an antigenically variable virus, we examined the effectiveness of this strategy against multiple serotypes and found that expressed 2B shRNA resulted in efficient silencing of at least 4 FMDV serotypes. Thus, RNA interference may be a potential alternative control strategy to limit the spread of this highly contagious virus in livestock.

Animals↗

Effects of potassium and chloride on ribosome association with the RNA of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) and other picornaviruses initiate translation of their polyprotein cap-independently at an internal site of the positive-strand viral RNA. This process is mediated by the internal ribosome entry site (IRES), a highly structured cis-acting RNA element that binds translation initiation factors and ribosomal subunits. During their life cycle, picornaviruses induce proliferation of membrane structures involved in viral replication and an increase in membrane permeability probably facilitating virus progeny release. Here, I analyze the efficiency of association of the ribosomal subunits with the FMDV IRES RNA at elevated salt concentrations. Potassium stimulates FMDV translation, whereas sodium chloride concentrations up to 150 mM neither stimulate nor interfere with FMDV translation. Even high potassium concentrations allow binding of the viral RNA to ribosomes. Chloride stimulates binding of ribosomes to the viral RNA at the stage of 48S initiation complex formation and FMDV translation at concentrations up to 150 mM. Only at elevated concentrations, binding of ribosomal subunits and translation are inhibited by chloride. However, FMDV start site selection is not influenced by potassium salts. These results indicate that the association of the viral RNA with ribosomal subunits is well adapted to high salt conditions that are induced during picornavirus infection.

Animals↗

The influence of diabetes and lower limb arterial disease on cutaneous foot perfusion.

OBJECTIVE: Peripheral arterial occlusive disease and peripheral neuropathy are major risk factors in diabetic foot disease. We evaluated the relative influences of noncritical lower limb arterial disease and peripheral neuropathy on cutaneous foot perfusion in diabetes. METHOD: Toe-brachial pressure indices, transcutaneous oxygen, and carbon dioxide tensions at foot and chest sites were measured in individuals with diabetes, with or without detectable peripheral neuropathy and with or without significant arterial disease on color duplex imaging. Subjects without diabetes, with and without arterial disease, were used as controls. RESULTS: A total of 130 limbs were studied during an 8-month period. Toe-brachial pressure indices reflected the presence of arterial disease in all groups. Foot transcutaneous oxygen values were reduced in diabetes and correlated with chest transcutaneous oxygen values. Low foot transcutaneous oxygen with elevated transcutaneous carbon dioxide values were only demonstrated in individuals with diabetes, arterial disease, and peripheral neuropathy. Toe-brachial pressure indices demonstrated a positive correlation with foot transcutaneous oxygen values, but values >1.2 demonstrated a negative correlation. CONCLUSIONS: We demonstrated two influences on cutaneous foot perfusion in diabetes: (1) a global microcirculatory dysfunction, reflected in low chest and foot transcutaneous oxygen values, and (2) macrovascular disease as indicated by reduced toe-brachial pressure indices and foot transcutaneous oxygen values. Further, the results demonstrated that in diabetic individuals without critical limb ischemia, impaired foot perfusion secondary to arterial disease is amplified significantly by coexisting microcirculatory disease.

Aged↗

[An epidemic of hand, foot and mouth disease].

Five patients with hand-, foot- and mouth disease, caused by infection with Coxsackievirus type A16, are described in an epidemic outbreak of this disease. Hand-, foot- and mouth disease, is characterized by a most distinctive enanthem-exanthemcomplex. In 65% of the cases a vesiculopapular exanthem is noted. Most cases are described in epidemic outbreaks. Although the vast majority of occurrences of the disease have been due to Coxsackie A16 viral infections, occasionally Coxsackie A5, A10 and enterovirus 71, seldom Coxsackievirus B1 or B3, have been etiologically incriminated. In this article attention is paid to the clinical characteristics, the epidemiology and the differential diagnostic aspects of hand-, foot- and mouth disease.

Child, Preschool↗

[Healing of skin lesions in diabetic foot syndrome during hospitalization].

Wound healing during the diabetic foot disease is indicated to in-patient treatment in case of non-healing wound, in case of serious infection and/or critical ischemia and in case of necessity of surgical treatment. Diabetic foot disease is the main reason for in-patient treatment of people with diabetes, which our experience confirms. Chronic wound is characterised by non-healing for at least 4 weeks. Ischemia and recurrent trauma caused by incomplete off-loading, prolong inflammation and infection are the main reasons for difficult healing of chronic wound. Infection is also leading cause for prolonged hospitalisation of patients with diabetic foot disease. Local decrease of grow factors and increase of tissue protease are characteristics of chronic wound. The process of wound healing is characterized by a cascade of interrelated events involving infection and inflammatory factors. The results of these investigations led to the moist wound healing concept and use of growth factors and bioengineered skin substitutes. We have good experience with the use of xenotransplant skin substitues in the treatment of diabetic foot. Off loading techniques including total contact casting, local therapy by debridement and skin substitutes had the best evidence based efficacy. We are introducing new method of the treatment of diabetic foot--VAC--vacuum assisted closure. The fundamental principle in the therapy during in-patient period, is comprehensive approach; the omitting of any of the principle of the therapy--e.g. the off-loading of the ulcers, the infection and ischemia control, may contribute to its failure.

Diabetic Foot↗

Antigenically profound amino acid substitutions occur during large population passages of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) with amino acid substitutions next to the highly conserved R-G-D motif were isolated following large population passages of the virus (N. Sevilla and E. Domingo, 1996, J. Virol., in press). Reactivity with a panel of monoclonal antibodies which recognize different epitopes within site A was abolished or highly diminished in the mutants. This provides direct evidence of a drastic antigenic change occurring in the absence of selection by antibodies. Molecular modeling studies predict only minor alterations in the conformation of the G-H loop of VP1 and the R-G-D motif in these mutants. None of these variants became dominant in many serial infections involving smaller FMDV population numbers. In addition to documenting profound antigenic variation without immune selection, the results suggest that the repertoire of antigenic variants evolving in viral quasispecies may be greatly influenced by the population size of the virus.

Amino Acids↗

Crystallization and preliminary X-ray diffraction analysis of foot-and-mouth disease virus.

Foot-and-mouth disease virus has been crystallized with the objectives of (1) determining the composition and conformation of the major immunogenic site(s) and (2) comparing its structure with those of the related polio, rhino and Mengo viruses, representing the other three genera of the picornaviruses. Most of the work has been done with virus strain O1BFS 1860, which crystallized as small rhombic dodecahedra of maximum dimension 0.3 mm. Virus recovered from crystals was infectious, and was indistinguishable from native virus both in protein composition and buoyant density. The stability of the crystals in the X-ray beam was comparable with that of other picornavirus crystals and they diffracted to a resolution of better than 2.3 A. Initial analysis of the X-ray diffraction data shows the virus to be positioned on a point of 23 symmetry in a close-packed array so that examples of all the icosahedral symmetry elements, except the 5-fold axes, are expressed crystallographically. The cell dimensions are a = b = c = 345 A, alpha = beta = gamma = 90 degrees, with a space group of I23. The diameter of the virus particle is 300 A. Despite the small size of the crystals, diffraction data have been collected to a reasonable resolution using a synchrotron source. Phasing of the diffraction data will be attempted using the methods of molecular replacement.

Aphthovirus↗

Crystallization and preliminary X-ray analysis of three serotypes of foot-and-mouth disease virus.

Foot-and-mouth disease viruses from serotypes O, A and C have been crystallized. The particular strains studied include O1K, A10(61), A22 Iraq 24/64, A24 Cruzeiro and C-S8c1. In addition, crystals have been grown of G67, a monoclonal antibody neutralization escape mutant derived from O1K, and of virus R100, recovered after the establishment of a persistent infection in baby hamster kidney cells with C-S8c1. Empty particles, capsids which lack the RNA genome, have also been crystallized for subtypes A22 Iraq 24/64 and A10(61). In almost all cases, crystals suitable for high resolution structure determination were obtained from (NH4)2SO4 or mixtures of polyethylene glycol and NH4Cl.

Aphthovirus↗

The nucleotide sequence at the 5' end of foot and mouth disease virus RNA.

Foot and mouth disease virus RNA has been treated with RNase H in the presence of oligo (dG) specifically to digest the poly(C) tract which lies near the 5' end of the molecule (10). The short (S) fragment containing the 5' end of the RNA was separated from the remainder of the RNA (L fragment) by gel electrophoresis. RNA ligase mediated labelling of the 3' end of S fragment showed that the RNase H digestion gave rise to molecules that differed only in the number of cytidylic acid residues remaining at their 3' ends and did not leave the unique 3' end necessary for fast sequence analysis. As the 5' end of S fragment prepared form virus RNA is blocked by VPg, S fragment was prepared from virus specific messenger RNA which does not contain this protein. This RNA was labelled at the 5' end using polynucleotide kinase and the sequence of 70 nucleotides at the 5' end determined by partial enzyme digestion sequencing on polyacrylamide gels. Some of this sequence was confirmed from an analysis of the oligonucleotides derived by RNase T1 digestion of S fragment. The sequence obtained indicates that there is a stable hairpin loop at the 5' terminus of the RNA before an initiation codon 33 nucleotides from the 5' end. In addition, the RNase T1 analysis suggests that there are short repeated sequences in S fragment and that an eleven nucleotide inverted complementary repeat of a sequence near the 3' end of the RNA is present at the junction of S fragment and the poly(C) tract.

Aphthovirus↗

Host cell selection of antigenic variants of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) A22 Iraq 24/64 adapted to grow in BHK monolayer cells induced antibodies which neutralized many isolates belonging to the A serotype. Plaque-purified virus isolated from this stock also induced broadly reactive antibodies, showing that this property is not due to the combined response to a mixture of variants in the original stock virus. However, viruses obtained by passage in suspension BHK cells of either the monolayer cell-adapted virus or a virus cloned from this stock resulted in the selection of virus which induced antibodies with highly specific neutralizing activity. In addition to their antigenic properties the monolayer and suspension cell-adapted viruses could be distinguished by plaque morphology, tendency to aggregate and ability to attach to BHK cells. Monoclonal antibodies (MAbs) induced with the plaque-purified monolayer-adapted virus had neutralizing activity almost as broad as polyclonal serum, showing that this property can be represented by a single epitope on the virus. These neutralizing MAbs recognize a trypsin-sensitive epitope on the virus. Surprisingly, sequence analysis of the structural protein-coding regions of the genomic RNAs of monolayer and suspension cell-adapted viruses showed no amino acid differences in VP1, the protein known to contain the major neutralization epitope in FMDV and to be the only protein susceptible to cleavage by trypsin in the virus particle. Although three coding differences were found in the capsid protein these were all located in VP2.

Amino Acid Sequence↗

A porcine CD8+ T cell clone with heterotypic specificity for foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV)-specific T cell lines and clones have been obtained from a swine lymphocyte antigen (SLA) inbred miniature pig vaccinated with chemically inactivated virus. One of the clones obtained, CE3, showed a specific and heterotypic proliferation against infectious but not inactivated FMDV in the presence of syngeneic peripheral blood mononuclear cells (PBMC). Adherent cells from PBMC were sufficient to support specific activation of the clone and the proliferation was abolished when the contact between CE3 and adherent cells was prevented. Phenotypic characterization of CE3 cells revealed expression of CD2, CD25 (interleukin-2 receptor), SLA class I and SLA class II. Furthermore, the cells were highly CD8 positive but showed low expression of CD4. The expression of T cell receptor (TCR) alpha and beta genes confirmed their T cell nature. Consistent with the CD8 phenotype, the proliferative response of CE3 was inhibited with MAbs to SLA class I and CD8. Altogether, these results indicate that CE3 is a porcine SLA class I-restricted CD8+ T cell clone, that recognizes a heterotypic FMDV antigen.

Animals↗

In vitro morphogenesis of foot-and-mouth disease virus.

Foot-and-mouth disease virion RNA is translated efficiently and completely in a rabbit reticulocyte lysate cell-free system. Treatment of cell-free lysates with monospecific serum prepared against the individual viral structural proteins or with monoclonal antibodies prepared against the inactivated virus or against a viral structural protein precipitated all of the structural proteins, suggesting that structural protein complexes were formed in vitro. Sucrose gradient analysis of the cell-free lysate indicated that complexes sedimenting at 5, 14, 60 to 70, and ca. 110S were assembled in vitro. Structural proteins VP0, VP1, and VP3 were the major polypeptides found in these complexes. The material sedimenting at 110S, i.e., containing VP0, VP1, and VP3, was precipitated by a 140S-specific monoclonal antibody but not by a 12S subunit-specific monoclonal antibody, suggesting that this capsid structure contained at least one epitope present on the intact virus.

Animals↗

A second protease of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) genes are expressed as a polyprotein which is rapidly processed into the four primary cleavage products L, P1, P2, and P3. In secondary cleavage reactions, these are further processed into the mature proteins. The FMDV L protein is located at the N terminus of the polyprotein and is the first gene product released from the nascent polyprotein. For analysis of its biological function, the L gene was mutated by site-directed mutagenesis of cloned cDNA. In vitro translation of in vitro transcripts of these DNAs and expression studies in Escherichia coli showed that the L mutants affect the processing of the viral polyprotein. The mutants isolated were partially or totally defective in processing the polyprotein at the L/P1 junction. These mutants could, however, be processed in the presence of the wild-type L protein. Furthermore, an antiserum directed against the L protein inhibited processing at the L/P1 cleavage site, so that the release of the L protein from the polyprotein was blocked. These data reveal that the L gene product represents a viral protease which catalyzes its own release from the nascent polyprotein.

Animals↗

Re-assessing the likelihood of airborne spread of foot-and-mouth disease at the start of the 1967-1968 UK foot-and-mouth disease epidemic.

The likelihood of airborne spread of foot-and-mouth disease at the start of the 1967-1968 epidemic is re-assessed in the light of current understanding of airborne disease spread. The findings strongly confirm those made at the time that airborne virus was the most likely cause of the rapid early development of the disease out to 60 km from the source. This conclusion is reached following a detailed epidemiological, meteorological and modelling study using original records and current modelling techniques. The role played by 'lee waves' as the mechanism for the spread is investigated. It is thought that they played little part in influencing the development of the epidemic. A number of lessons learned from the work are drawn, identifying the need for further research on the quantity and characteristics of airborne virus. The results are also used to illustrate what advice would have been available to disease controllers if the outbreak had occurred in 2004.

Air Microbiology↗