Restriction endonuclease profiles of orf virus isolates from the British Isles

Outbreak of contagious ecthyma caused by Orf virus (Parapoxvirus ovis) in a vaccinated sheep flock in Uruguay

Orf virus (ORFV) causes contagious ecthyma (CE), a highly transmissible, zoonotic disease of small ruminants. CE most commonly affects lambs and unvaccinated sheep. This work reports epidemiologic, clinicopathologic, and virologic findings in a CE outbreak in a vaccinated sheep flock in Uruguay and failure to detect ORFV in a commercial vaccine.

Genetic diversity of Orf virus isolated from sheep in Uruguay

Orf virus (ORFV) is the etiological agent of contagious ecthyma, a disease widely spread in the world that occasionally causes zoonotic infections. This work is the first molecular characterization of ORFV in Uruguay, where we analyzed twenty-one sheep samples, eighteen of which were recovered from thirteen ORFV outbreaks that occurred during 2004 to 2011 as well as three strains from a national vaccine. Phylogenetic analysis and the derived amino acid sequences from the B2L gene suggest that the Uruguayan virus do not form a unique cluster, with most of them displaying similarities with worldwide ORFV isolates as well as our vaccine strains.

Experimental parapoxvirus infection (contagious ecthyma) in semi-domesticated reindeer (Rangifer tarandus tarandus)

Contagious ecthyma (contagious pustular dermatitis, orf) occurs world-wide in sheep and goats and is caused by orf virus (genus Parapoxvirus, family Poxviridae). Contagious ecthyma outbreaks have been described in semi-domesticated reindeer (Rangifer tarandus tarandus) in Sweden, Finland and Norway, occasionally with high mortality. Fourteen one-year-old reindeer were corralled in mid-April. One week after arrival, two animals received a commercial live orf virus vaccine for sheep (Scabivax(®)) on scarified skin of the medial thigh. Four weeks later, the two vaccinated and six additional animals were inoculated in scarified oral mucosa with parapoxvirus obtained from reindeer with clinical contagious ecthyma. The remaining six reindeer were kept as sentinels, sharing feed and water with the inoculated animals. A small whitish lesion appeared on the inoculation site and the labial skin-mucosa junction of three animals five days post inoculation (p.i.). Twelve days p.i., typical ecthyma lesions were visible on the inoculation site in six of eight animals, including both vaccinees. Four inoculated animals (including both vaccinees) and one sentinel seroconverted 12 days p.i., and five animals (including one sentinel) seroconverted 20 days p.i. No contagious ecthyma-like lesions were detected in the sentinels. All animals were euthanized at 26-29 days p.i. Histological examination of lesions showed proliferative dermatitis with epidermal hyperplasia, hyperkeratosis, intra-epithelial pustules and ulcers. Orf virus DNA was detected in mandibular lymph nodes, tonsils and mucosal lesions of four animals, including one sentinel, which showed that virus transmission took place. The commercial orf virus vaccine may be difficult to administer due to the need for close-cropping and its zoonotic nature, and did not indicate significant protection, although the latter has to be verified with a larger number of animals.

Therapeutic paint of cidofovir/sucralfate gel combination topically administered by spraying for treatment of orf virus infections

The aim of the research was to study a new cidofovir/sucralfate drug product to be used as a spray for treating the mucosal and/or skin lesions. The product, i.e., a water suspension of sucralfate (15% w/w) and cidofovir (1% w/w), combines the potent antiviral activity of the acyclic nucleoside phosphonate cidofovir ((S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine) and the wound healing properties of sucralfate gel (sucrose octasulphate basic aluminum salt). The product was characterized in vitro with respect to compatibility between drug and carrier, spray particle size, spray deposition, drying kinetics, and drug content and release. An interaction between the two active substances was found. The interaction between sucralfate and cidofovir was counteracted by introducing sodium dihydrogen phosphate (16% w/w) in the preparation. The spray formulation containing cidofovir/sucralfate gel painted the skin and dried quickly to a scab, remaining firmly adhered to the lesions. The therapeutic paint was tested in vivo on lambs infected with orf virus by treating the animals with different cidofovir/sucralfate formulations (0.5% or 1% cidofovir + sucralfate 15% + NaH(2)PO(4) 16% w/w) and with sucralfate gel suspension alone as control. The treatment with formulations containing cidofovir and phosphate salt for four consecutive days resulted in a rapid resolution of the lesions, with scabs containing significantly lower amounts of viable virus when compared with untreated lesions and lesions treated with sucralfate suspension alone.

Isolation and Characterization of an Indian Orf Virus from Goats

Isolation and characterization of an orf virus has been described here. The virus was isolated from an outbreak of 'scabby mouth' in goats in Northern India. Viral morphology from the scab biopsy revealed typical ovoid-shaped particles characteristic of Parapoxvirus. Virus was isolated from sonicated scab suspension and characterized by restriction enzyme (RE) analysis and sequencing of full-length GM-CSF- and interleukin-2 inhibitory factor (GIF) gene. RE pattern of the virus did not show close resemblance to most of the orf viruses published earlier. However, it showed high sequence identity and closer phylogenetic relationship with previously published ORFV-SA00 strain, as evident from the nucleotide and deduced amino acid sequence of GIF gene.

Antiviral activity of HPMPC (cidofovir) against orf virus infected lambs

(S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine [corrected] (HPMPC, cidofovir, CDV, Vistide) is an acyclic nucleoside analogue with a potent and selective activity against a broad spectrum of DNA viruses including the poxviruses. In this study we present the results of different treatment regimens in lambs experimentally infected with orf virus with different cidofovir formulations prepared in Beeler basis and Unguentum M. Our results show that choice of excipient, concentration of codofovir [corrected] and treatment regimen were all important to the clinical outcome of the therapy. Whilst one particular regimen appeared to exacerbate the lesion, treatment with 1% (w/v) cidofovir cream, prepared in Beeler basis, for 4 consecutive days did result in milder lesions that resolved in milder lesions that resolved [corrected] more quickly than untreated lesions. Furthermore the scabs of the treated animals contained significantly lower amounts of viable virus meaning there should be less contamination of the environment with virus than would normally occur.

Genomic characterization of a novel poxvirus contributing to the decline of the red squirrel (Sciurus vulgaris) in the UK

The genome of a virulent squirrelpox virus (SQPV) isolate was characterized in order to determine its relationship with other poxviruses. Restriction enzyme analysis suggested a genome length of approximately 158 kb, whilst sequence analysis of the two ends of the genome indicated a G + C composition of approximately 66 %. Two contiguous stretches of 23 and 37 kb at the left-hand and right-hand ends of the genome, respectively, were sequenced allowing the identification of at least 59 genes contained therein. The partial sequence of a further 15 genes was determined by spot sequencing of restriction fragments located across the genome. Phylogenetic analysis of 15 genes conserved in all the recognized genera of the subfamily Chordopoxvirinae confirmed that the SQPV does not group within the family Parapoxvirinae, but instead partitions on its own in a separate clade of the poxviruses. Analysis of serum from British woodland rodents failed to find any evidence of SQPV infection in wood mice or bank voles, but for the first time serum samples from grey squirrels in the USA were found to contain antibody against SQPV.

Activities of acyclic nucleoside phosphonates against Orf virus in human and ovine cell monolayers and organotypic ovine raft cultures

Orf virus, a member of the Parapoxvirus genus, causes a contagious pustular dermatitis in sheep, goats, and humans. Previous studies have demonstrated the activity of (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC; cidofovir; Vistide) against orf virus in cell culture and humans. We have evaluated a broad range of acyclic nucleoside phosphonates (ANPs) against several orf virus strains in primary lamb keratinocytes (PLKs) and human embryonic lung (HEL) monolayers. HPMPC, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6- diaminopurine (HPMPDAP), and (R)-9-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine (HPMPO-DAPy) were three of the most active compounds that were subsequently tested in a virus yield assay with PLK and HEL cells by virus titration and DNA quantification. HPMPC, HPMPDAP, and HPMPO-DAPy were evaluated for their activities against orf virus replication in organotypic epithelial raft cultures from differentiated PLK cells. At the highest concentrations (50 and 20 microg/ml), full protection was provided by the three drugs, while at 5 microg/ml, only HPMPDAP and HPMPC offered partial protection. The activities of the three compounds in the raft culture system were confirmed by quantification of infectious virus and viral DNA. These findings provide a rationale for the use of HPMPC and other ANPs in the treatment of orf (contagious ecthyma) in humans and animals.

Characterization of a North American orf virus isolated from a goat with persistent, proliferative dermatitis

The characterization of an orf virus (OV) isolated from skin lesions of a goat kid with severe, persistent, proliferative dermatitis, and designated orf virus-San Angelo 2000 (OV-SA00) strain, is described. The identity of OV-SA00 was confirmed by a combination of methods, including electron microscopy, amplification of specific fragments of viral DNA by polymerase chain reaction, restriction enzyme analysis of viral DNA and gene sequencing. Restriction endonuclease analyses of viral DNA and the protein profile studied by Western blot revealed differences between OV-SA00 strain and the profiles of other OV strains that have been published. The restriction enzyme profile of OV-SA00 was also different from the orf virus vaccine (OV-V) strain used to vaccinate this kid. Comparison of the nucleotide and deduced amino acid sequences indicated that OV-SA00 is closely related to OV-V strain, the Scottish OV strains orf11 and MRI Scab, and the human OV-CE/Shoe strain and more distant to bovine papular stomatitis virus (BPSV) reference strain and the pseudocowpox virus (PCPV)-MNV/Till strain. These results indicate that OV-SA00 is a strain of OV rather than a different parapoxvirus. Further studies are necessary to determine if the severity of orf-induced lesions in this goat kid was the result of individual host susceptibility factors.

Relatedness and heterogeneity at the near-terminal end of the genome of a parapoxvirus bovis 1 strain (B177) compared with parapoxvirus ovis (Orf virus)

The present study provides for the first time an extended investigation of individual genes located at the near-terminal right end of the genome of parapoxvirus bovis 1, Bovine papular stomatitis virus (BPSV) strain B177 and Orf virus (ORFV). Comparison of the respective DNA sequences of ORFV strain D1701 (9.9 kbp) and BPSV B177 (7.7 kbp) revealed a very similar organization of closely related genes transcribed in a rightward orientation. The most salient findings of this study were: (i) the absence of the ORFV-specific vascular endothelial growth factor (VEGF-E) gene in the BPSV isolate; (ii) the presence of an interleukin-10 (IL-10) orthologue; and (iii) the detection of three new genes encoding ankyrin-repeat-containing polypeptides. These results not only contribute to potential improvements of future molecular differentiation between the parapoxvirus species, but also shed new light on different pathobiologies among parapoxviruses.

Vascular endothelial growth factors encoded by Orf virus show surprising sequence variation but have a conserved, functionally relevant structure

The first report of a vascular endothelial growth factor (VEGF)-like gene in Orf virus included the surprising observation that the genes from two isolates (NZ2 and NZ7) shared only 41.1% amino acid sequence identity. We have examined this sequence disparity by determining the VEGF gene sequence of 21 isolates of Orf virus derived from diverse sources. Most isolates carried NZ2-like VEGF genes but their predicted amino acid sequences varied by up to 30.8% with an average amino acid identity between pairs of NZ2-like sequences of 86.1%. This high rate of sequence variation is more similar to interspecies than intraspecies variability. In contrast, only three isolates carried an NZ7-like VEGF gene and these varied from the NZ7 sequence by no more than a single nucleotide. The VEGF family are ligands for a set of tyrosine kinase receptors. The viral VEGFs are unique among the family in that they recognize VEGF receptor 2 (VEGFR-2) but not VEGFR-1 or VEGFR-3. Comparisons of the viral VEGFs with other family members revealed some correlations between conserved residues and the ability to recognize specific VEGF receptors. Despite the sequence variations, structural predictions for the viral VEGFs were very similar to each other and to the structure determined by X-ray crystallography for human VEGF-A. Structural modelling also revealed that a groove seen in the VEGF-A homodimer and believed to play a role in its binding to VEGFR-1 is blocked in the viral VEGFs. This may contribute to the inability of the viral VEGFs to bind VEGFR-1.

Immunity and counter-immunity during infection with the parapoxvirus orf virus

Orf virus is a DNA parapoxvirus that causes orf, an acute debilitating skin disease of sheep, goats and humans. In sheep, a vigorous immune response involving neutrophils, dermal dendritic cells, T cells, B cells and antibody is generated after infection. CD4(+) T cells, IFN-gamma and to a lesser extent CD8(+) T cells are involved in partial protection against infection. In spite of this, orf virus can repeatedly infect sheep albeit with reduced lesion size and time to resolution compared to primary infection. This is due at least in part to the action of virus immuno-modulator proteins that interfere with host immune and inflammatory responses. These include: an interferon resistance protein; a viral orthologue of mammalian IL-10 (vIL-10) that is an anti-inflammatory cytokine; and a novel inhibitor of the cytokines GM-CSF and IL-2 (GIF). The virus also encodes a virulence protein that is an orthologue of mammalian vascular endothelial growth factor. The study of the immuno-modulator proteins provides an insight into disease pathogenesis and important elements of a host protective response. This information will be used to devise a rational disease control strategy.

Genomic comparison of an avirulent strain of Orf virus with that of a virulent wild type isolate reveals that the Orf virus G2L gene is non-essential for replication

The genomic structure of two strains of orf virus (OV), a field isolate (MRI-Scab) which has never been passaged in cell culture, and a multiple-passage cell culture-adapted strain (Orf-11) were compared. The Orf-11 genome is approximately 8.0 kb longer than that of the MRI-Scab due to a duplication of the right-hand end. The duplicated region has been translocated to the left-hand end of the genome with a loss of sequence from that end. The lost sequence contains three complete genes, namely E2L, E3L and G1L and 80% of a fourth gene, namely G2L. The sequence lost from G2L in Orf-11 has been replaced by a region of unrelated sequence, encoding 98 amino acids. Northern analysis shows that mRNA is expressed from this "new" gene. The two viruses were also compared for in vivo virulence and ability to protect against subsequent OV challenge. In vivo, the field isolate was fully virulent and conferred good protection against challenge, whereas the cell culture-adapted virus produced only mild lesions and reduced protection against challenge.