Plasmids encoding foot-and-mouth disease virus VP1 epitopes elicited immune responses in mice and swine and protected swine against viral infection.
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VP1 is a capsid protein of foot-and-mouth disease virus (FMDV) and contains epitopes of the virus. Plasmids encoding two VP1 epitopes (amino acid residues 141-160 and 200-213) and a host-self immunoglobulin molecule were constructed to produce a new type of FMD DNA vaccine. Two plasmids, namely, pCEIM and pCEIS, containing mouse immunoglobulin (IgG) or swine IgG were subjected to immunogenicity testing in mice and swine, respectively. In mice administrated pCEIM in the abdomen using a genegun, both FMDV-specific T-cell proliferation and neutralizing antibodies were detected. In swine immunized with pCEIS at the back of the ear, immune responses were achieved after the second administration. Swine showed a T-cell proliferative response with a stimulation index (SI) of up to 8.1 and a neutralizing antibody response that was able to protect suckling mice from 10(2) LD(50) (lethal dose 50) FMDV challenge. To compare the immunogenicity of the DNA-based vaccine candidate, versus the protein-based vaccine candidates, a second group of swine was immunized with the protein F1-scIgG, which was encoded by the plasmid pCEIS. Injection with F1-scIgG elicited a T-cell proliferative response of SI < 1.7 and a neutralizing antibody response that protected suckling mice from up to 10(5) LD(50) FMDV challenge. In the challenge test, three of three swine immunized with pCEIS were fully protected from FMDV challenge. (+info)
The ability of integrin alpha(v)beta(3) To function as a receptor for foot-and-mouth disease virus is not dependent on the presence of complete subunit cytoplasmic domains.
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The integrin alpha(v)beta(3) has been shown to function as one of the integrin receptors on cultured cells for foot-and-mouth disease virus (FMDV), and high-efficiency utilization of the bovine homolog of this integrin is dependent on the cysteine-rich repeat region of the bovine beta(3) subunit. In this study we have examined the role of the cytoplasmic domains of the alpha(v) and beta(3) subunits in FMDV infection. We have found that truncations or extensions of these domains of either subunit, including deletions removing almost all of the cytoplasmic domains, had little or no effect on the ability of the integrin to function as a receptor for FMDV. The lysosomotropic agent monensin inhibited viral replication in cells transfected with either intact or cytoplasmic domain-truncated alpha(v)beta(3). In addition, viral replication in transfected cells was inhibited by an alpha(v)beta(3) function-blocking antibody but not by function-blocking antibodies to three other RGD-directed integrins, suggesting that these integrins are not involved in the infectious process. These results indicate that alterations to the cytoplasmic domains of either subunit, which lead to the inability of the integrin receptor to function normally, do not abolish the ability of the integrin to bind and internalize this viral ligand. (+info)
Deletion or substitution of the aphthovirus 3' NCR abrogates infectivity and virus replication.
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The 3' noncoding region (NCR) of the genomic picornaviral RNA is believed to contain major cis-acting signals required for negative-strand RNA synthesis. The 3' NCR of foot-and-mouth disease virus (FMDV) was studied in the context of a full-length infectious clone in which the genetic element was deleted or exchanged for the equivalent region of a distantly related swine picornavirus, swine vesicular disease virus (SVDV). Deletion of the 3' NCR, while maintaining the intact poly(A) tail as well as its replacement for the SVDV counterpart, abrogated virus replication in susceptible cells as determined by infectivity and Northern blot assays. Nevertheless, the presence of the SVDV sequence allowed the synthesis of low amounts of chimeric viral RNA at extended times post-transfection as compared to RNAs harbouring the 3' NCR deletion. The failure to recover viable viruses or revertants after several passages on susceptible cells suggests that the presence of specific sequences contained within the FMDV 3' NCR is essential to complete a full replication cycle and that FMDV and SVDV 3' NCRs are not functionally interchangeable. (+info)
Evidence for positive selection in foot-and-mouth disease virus capsid genes from field isolates.
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The nature of selection on capsid genes of foot-and-mouth disease virus (FMDV) was characterized by examining the ratio of nonsynonymous to synonymous substitutions in 11 data sets of sequences obtained from six different serotypes of FMDV. Using a method of analysis that assigns each codon position to one of a number of estimated values of nonsynonymous to synonymous ratio, significant evidence of positive selection was identified in 5 data sets, operating at 1-7% of codon positions. Evidence of positive selection was identified in complete capsid sequences of serotypes A and C and in VP1 sequences of serotypes SAT 1 and 2. Sequences of serotype SAT-2 recovered from a persistently infected African buffalo also revealed evidence for positive selection. Locations of codons under positive selection coincide closely with those of antigenic sites previously identified with the use of monoclonal antibody escape mutants. The vast majority of codons are under mild to strong purifying selection. However, these results suggest that arising antigenic variants benefit from a selective advantage in their interaction with the immune system, either during the course of an infection or in transmission to individuals with previous exposure to antigen. Analysis of amino acid usage at sites under positive selection indicates that this selective advantage can be conferred by amino acid substitutions that share physicochemically similar properties. (+info)
Evidence for positive selection in the capsid protein-coding region of the foot-and-mouth disease virus (FMDV) subjected to experimental passage regimens.
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We present sequence data from two genomic regions of foot-and-mouth disease virus (FMDV) subjected to several experimental passage regimens. Maximum-likelihood estimates of the nonsynonymous-to-synonymous rate ratio parameter (d(N)/d(S)) suggested the action of positive selection on some antigenic sites of the FMDV capsid during some experimental passages. These antigenic sites showed an accumulation of convergent amino acid replacements during massive serial cytolytic passages and also in persistent infections of FMDV in cell culture. This accumulation was most significant at the antigenic site A (the G-H loop of capsid VP1), which includes an Arg-Gly-Asp (RGD) cellular recognition motif. Our analyses also identified a subregion of VP3, part of the fivefold axis of FMDV particles, that also appeared to be subjected to positive selection of amino acid replacements. From these results, we can conclude that under the restrictive conditions imposed either by the presence of the monoclonal antibodies, by the persistent infections, or by the competition processes established between different variants of the viral population, amino acid replacement in some capsid-coding regions can be positively selected toward an increase of those mutants with a higher capability to infect the cell. (+info)
Emergence in Asia of foot-and-mouth disease viruses with altered host range: characterization of alterations in the 3A protein.
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In 1997, an epizootic in Taiwan, Province of China, was caused by a type O foot-and-mouth disease virus which infected pigs but not cattle. The virus had an altered 3A protein, which harbored a 10-amino-acid deletion and a series of substitutions. Here we show that this deletion is present in the earliest type O virus examined from the region (from 1970), whereas substitutions surrounding the deletion accumulated over the last 29 years. Analyses of the growth of these viruses in bovine cells suggest that changes in the genome in addition to the deletion, per se, are responsible for the porcinophilic properties of current Asian viruses in this lineage. (+info)
Foot-and-mouth disease type O viruses exhibit genetically and geographically distinct evolutionary lineages (topotypes).
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Serotype O is the most prevalent of the seven serotypes of foot-and-mouth disease (FMD) virus and occurs in many parts of the world. The UPGMA method was used to construct a phylogenetic tree based on nucleotide sequences at the 3' end of the VP1 gene from 105 FMD type O viruses obtained from samples submitted to the OIE/FAO World Reference Laboratory for FMD. This analysis identified eight major genotypes when a value of 15% nucleotide difference was used as a cut-off. The validity of these groupings was tested on the complete VP1 gene sequences of 23 of these viruses by bootstrap resampling and construction of a neighbour-joining tree. These eight genetic lineages fell within geographical boundaries and we have used the term topotype to describe them. Using a large sequence database, the distribution of viruses belonging to each of the eight topotypes has been determined. These phylogenetically based epidemiological studies have also been used to identify viruses that have transgressed their normal ecological niches. Despite the high rate of mutation during replication of the FMD virus genome, the topotypes appear to represent evolutionary cul-de-sacs. (+info)
A novel protein-RNA binding assay: functional interactions of the foot-and-mouth disease virus internal ribosome entry site with cellular proteins.
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Translation initiation on foot-and-mouth disease virus (FMDV) RNA occurs by a cap-independent mechanism directed by a highly structured element (approximately 435 nt) termed an internal ribosome entry site (IRES). A functional assay to identify proteins that bind to the FMDV IRES and are necessary for FMDV IRES-mediated translation initiation has been developed. In vitro-transcribed polyadenylated RNAs corresponding to the whole or part of the FMDV IRES were immobilized on oligo-dT Dynabeads and used to deplete rabbit reticulocyte lysate (RRL) of IRES-binding proteins. Translation initiation factors eIF4G, eIF4A, and eIF4B bound to the 3' domain of the FMDV IRES. Depletion of eIF4G from RRL by this region of the FMDV IRES correlated with the loss of translational capacity of the RRL for capped, uncapped, and FMDV IRES-dependent mRNAs. However, this depleted RRL still supported hepatitis C virus IRES-directed translation. Poly (rC) binding protein-2 bound to the central domain of the FMDV IRES, but depletion of RRL with this IRES domain had no effect on FMDV IRES-directed translation initiation. (+info)