Comparison of two 3ABC enzyme-linked immunosorbent assays for diagnosis of multiple-serotype foot-and-mouth disease in a cattle population in an area of endemicity.

The development of a serological test for foot-and-mouth disease virus (FMDV) which is quick and easy to use, which can identify all seven serotypes, and which can differentiate vaccinated from convalescing or potential virus carriers would be a major advance in the epidemiological toolkit for FMDV. The nonstructural polyprotein 3ABC has recently been proposed as such an antigen, and a number of diagnostic tests are being developed. This paper evaluates the performance of two FMDV tests for antibodies to nonstructural proteins in an unvaccinated cattle population from a region of Cameroon with endemic multiple-serotype FMD. The CHEKIT-FMD-3ABC bo-ov (CHEKIT) enzyme-linked immunosorbent assay (ELISA) (Bommeli Diagnostics/Intervet) is a commercially available test that was compared with a competitive 3ABC ELISA (C-ELISA) developed in Denmark. The tests were compared with the virus neutralization test as the "gold standard." Diagnostic sensitivity and specificity were examined over a range of test cutoffs by using receiver operating characteristic curves, which allowed comparison of the overall performance of each test. The results indicated that the CHEKIT ELISA kit was 23% sensitive and 98% specific and the Danish C-ELISA was 71% sensitive and 90% specific at the recommended cutoff. These results have important implications if the tests are to be used to screen herds or individual cattle in surveillance programs, at border crossings for import-export clearance, or following emergency vaccination in an outbreak situation.

The localization of persistent foot and mouth disease virus in the epithelial cells of the soft palate and pharynx.

After contact with foot and mouth disease virus (FMDV), cattle may become persistently infected, regardless of their pre-existing immune status or whether they develop clinical disease. The cellular sites of FMDV persistence have not previously been determined. The use of in-situ hybridization in combination with tyramide signal amplification (TSA) provided the first direct evidence that FMDV RNA is localized within the epithelial cells of the soft palate and pharynx during persistent infection, indicating that these cells remain persistently infected after contact with FMDV.

Swine vesicular disease: an overview.

Swine vesicular disease (SVD) is a notifiable viral disease of pigs included on the Office International des Epizooties List A. The first outbreak of the disease was recognized in Italy in 1966. Subsequently, the disease has been reported in many European and Asian countries. The causative agent of the disease is SVD virus which is currently classified as a porcine variant of human coxsackievirus B5 and a member of the genus enterovirus in the family picornaviridae. From a clinical point of view, SVD is relatively unimportant, rarely causing deaths and usually only a minor setback to finishing schedules. However, the clinical signs which it produces are indistinguishable from those caused by foot-and-mouth disease, and its presence prevents international trade in pigs and pig products. This article reviews recent findings on all aspects of the virus and the disease which it causes.

Nucleotide sequence of the structural protein-encoding region of foot-and-mouth disease virus A22-India.

Nucleotide sequence of the structural protein-encoding region of foot-and-mouth disease virus (FMDV) A22-India 17/77 was determined using non-radioisotopic technique. Comparison of nucleotide and deduced amino acid sequence with A22-Iraq 24/64 revealed 175 synonymous (silent) and 42 non-synonymous nucleotide changes resulting in 34 amino acid substitutions along the capsid proteins (VP1-VP4). Out of the 4 structural proteins VP4 is highly conserved. The highly variable and immunodominant protein VP1 showed 47% of the total amino acid substitutions. VP2 and VP3 contain 38.2% and 14.7% of the amino acid substitutions, respectively. The VP1-based phylogenetic analysis of 18 different type A viruses including A22-India 17/77 divided them in to two broad genetic groups (Asian and European/South American), and each group is further subdivided in to two separate genotypes. A22-India 17/77, A22-Iraq 24/64 and A22-Azerbaijan/65 formed one genotype and the 4 Chinese strains formed a separate genotype in the Asian group of viruses. In the European/South American group, A-Argentina/87 represents one genotype and the remaining 10 strains formed the second genotype in this group.

Genetic heterogeneity of Indian field isolates of foot-and-mouth disease virus serotype O as revealed by partial sequencing of 1D gene.

The sequence of 165 nucleotides at the 3' end of the 1D gene, determined from RT PCR amplified cDNA fragments, of 25 type O strains isolated from different parts/regions of India during 1987 1995 and the vaccine strain (R2/75) currently in use in India were subjected to phylogenetic analysis. One isolate from the neighbouring country Nepal was also included in the study. The virus/ field strains showed high degree of genetic heterogeneity among themselves with % divergence in nucleotide sequence ranging from 1.2 to 19.4%. The Indian strains were much away (13.3 20.6%) from the exotic type O strains of O1BFS, O1K, and O1Campos. The type O strains analyzed were classified into three genotypes basing on level of divergence observed in nucleotide sequence. The type O vaccine virus (R2/75) was > 71% divergent (7.3-15.2%) from the field strains which revealed significant ( > 5%) genetic heterogeneity between the two. The phylogenetic analysis identified three distinct lineages, viz., (i) lineage 1 represented by the exotic strains, (ii) lineage 2 represented by 25 of the field strains which clustered into seven subgroups/sublines (2a-2g), and (iii) lineage 3 represented by a unique field isolate which shared the branching/origin with the vaccine strain. The lineage 2 which comprised of 25 of the 26 type O field strains analyzed, was placed almost at equidistance from the lineages 1 and 3 in the phylogenetic tree. The vaccine strain was closer to the viruses in lineage 2. Though there was no specific distribution pattern of sequences in different geographical regions of India, the viruses/ sequences in subgroup 2f appeared to be restricted to the southern states. Comparison of deduced amino acid sequence in the immunodominant regions 133-160 and 200-208 of the 1D gene product (VP1) showed that the two viruses in lineage 3 had unique amino acid residues at the positions 138 (D), 139 (G), 144 (I), and 158 (A) compared to rest of the strains including the exotic ones. Comparison of amino acid residues at critical positions 144, 148, 149, 151, 153, 154, and 208 revealed similarity between the type O strains analyzed. The virus strains showed variation (V/L/I) at position 144. One field strain showed replacement from Q149-->E and another from P208-->L. Thus, the study revealed that the type O FMD virus populations circulating in India and causing disease outbreaks are genetically much heterogeneous but related at the immunodominant region of VP1 polypeptide, and there are more than one genetically distinct virus populations in almost every region of the country which is possible due to unrestricted animal movement in the country. The involvement of vaccine virus in disease outbreaks was ruled out as the field strains (excluding the one in lineage 3) were phylogenetically distinct from it.

Molecular analysis of foot-and-mouth disease type O viruses isolated in Saudi Arabia between 1983 and 1995.

Partial nucleotide sequence of the capsid polypeptide coding gene 1D (VP1) was determined for 68 serotype O foot-and-mouth disease viruses isolated between 1983 and 1995 from outbreaks occurring in Saudi Arabia. The sequences were compared with previously published sequences: 14 viruses of Middle Eastern origin (isolated between 1987 and 1991); and with four vaccine virus strain sequences, three originating from the Middle East (O1/Turkey/Manisa/69, O1/Sharquia/Egypt/72 and O1/Israel/2/85) and one from Europe (O1/BFS 1860/UK/67). The virus isolates from Saudi Arabia and the Middle East vaccine virus strains formed a related genetic group distinct from the European O1 virus. Within this large group 12 distinct genetic sublineages were observed.

Use of a recombinant antigen in an indirect ELISA for detecting bovine antibody to capripoxvirus.

The gene coding for the capripoxvirus structural protein P32 was cloned, expressed in Escherichia coli as a fusion protein with glutathione-S-transferase, and purified on glutathione Sepharose. An indirect enzyme linked immunosorbent assay (ELISA) using this antigen was developed to screen bovine sera for antibodies to capripoxvirus. Sequential serum samples from experimentally infected animals tested by ELISA and by virus neutralisation test (VNT) showed that the ELISA was more sensitive and detected antibodies to capripoxvirus earlier post-infection than the VNT.

Recombinant capripoxvirus expressing the hemagglutinin protein gene of rinderpest virus: protection of cattle against rinderpest and lumpy skin disease viruses.

A cDNA clone containing the complete coding sequence of the hemagglutinin (H) protein gene of the RBOK vaccine strain of rinderpest virus, under the control of the vaccinia late promoter p11, was inserted by homologous recombination into the thymidine kinase gene of the KS-1 strain of capripoxvirus. The recombinant virus produced authentic H protein as judged by its electrophoretic mobility, transport to the cell surface of infected lamb testis cells, and reactivity with monoclonal antibodies specific for the H protein of rinderpest virus. The recombinant virus induced significant levels of rinderpest virus neutralizing antibodies in vaccinated cattle and protected them from clinical rinderpest after challenge with a lethal dose of a highly virulent heterologous strain of the virus. Protection was achieved using vaccine doses lower than those used with a similar recombinant expressing the fusion protein gene of rinderpest. The parental KS-1 virus is widely used as a vaccine against capripox viruses and so the rinderpest recombinant acts as a dual vaccine to protect cattle against both rinderpest and lumpy skin disease.

Protection of cattle against rinderpest and lumpy skin disease with a recombinant capripoxvirus expressing the fusion protein gene of rinderpest virus.

Cattle were protected against challenge with rinderpest and lumpy skin disease viruses by vaccination with a recombinant capripoxvirus containing the fusion protein (F) gene of rinderpest virus. The minimum protective immunising doses for rinderpest and lumpy skin disease were 5.5 x 10(4) plaque forming units (pfu) and 1.5 x 10(3) pfu, respectively.

Single capripoxvirus recombinant vaccine for the protection of cattle against rinderpest and lumpy skin disease.

A recombinant capripoxvirus has been constructed containing a full-length cDNA of the fusion protein gene of rinderpest virus. The gene was inserted in the thymidine kinase gene of the capripox genome under the control of the vaccinia virus major late promoter p11 together with the Escherichia coli gpt gene in the opposite orientation under the control of the vaccinia early/late promoter p7.5. A vaccine prepared from this recombinant virus protected cattle against clinical rinderpest after a lethal challenge with a virulent virus isolate. In addition, the vaccine protected the cattle against lumpy skin disease.

Serological and biochemical analysis of some recent type A foot-and-mouth disease virus isolates from the Middle East.

In 1986 and 1987 foot-and-mouth disease virus (FMDV) serotype A was isolated from outbreaks of disease in Saudi Arabia and Iran. Selected virus isolates were antigenically distinct from the prototype A22 virus strain (A22/Iraq/64), but were serologically related to each other. However, polyacrylamide gel electrophoresis showed that whilst the respective Saudi Arabian structural polypeptides were homogeneous, those from an Iran isolate were distinct. Direct sequencing of part of the P-1D (VP1) gene demonstrated considerable difference in nucleotide homology between the two groups of viruses; the Saudi Arabian viruses were closely related to each other but only distantly related to both the A22 prototype virus strain and the Iranian virus isolate. The latter viruses were only slightly more closely related to each other. Thus there appeared to be at least two distinct FMDV type A variants co-circulating in the Middle East, both of which differed considerably from the classical A22 subtype.

Studies on the major common precipitating antigen of capripoxvirus.

The proteins of sheep pox, goat pox, sheep and goat pox and lumpy skin disease (Neethling) viruses were labelled with [35S]methionine. The major structural polypeptides of these viruses co-migrated on polyacrylamide gels, demonstrating the very close biochemical relationship between them. Using the agar gel immunodiffusion (AGID) test with radiolabelled antigen preparations, a major common precipitating antigen was identified. This co-migrated on polyacrylamide gels with one of the major structural polypeptides [mol. wt. 67000 (67K)]. The use of [35S]methionine-labelled antigen preparations considerably improved the sensitivity of the AGID test as a diagnostic test for capripoxvirus antibody detection.

Clinical and antigenic relationship between isolates of sheep and goat pox viruses.

Isolates of sheep pox and goat pox from Nigeria, Sudan, Kenya, Yemen Arab Republic, Turkey, Pakistan and India were inoculated into British breeds of sheep and goats. Although the isolates displayed a host preference the gross clinical pathology of the disease produced by the different isolates was indistinguishable. The Yemen, Nigeria and India isolates could not be distinguished using homologous and heterologous antisera in neutralisation tests. Animals that had recovered from infection with one isolate were resistant to challenge with any of the other isolates and a single vaccine for use against sheep pox and goat pox is described. The classification of the malignant pox diseases of sheep and goats is discussed.