Biomedical subjects

David M Haig

Publications and source records attributed to David M Haig.

7 recordsLinked to original sources

PubMed2007

Complete sequence and analysis of the ovine herpesvirus 2 genome.

Ovine herpesvirus 2 (OvHV-2) is endemic in sheep populations worldwide and causes malignant catarrhal fever (MCF), a lymphoproliferative disease, in cattle, bison and deer. OvHV-2 has been placed in the gammaherpesvirus subfamily and is related closely to Alcelaphine herpesvirus 1 (AlHV-1). Here, the cloning, sequencing and analysis of the complete OvHV-2 genome derived from a lymphoblastoid cell line from an affected cow (BJ1035) are reported. The unique portion of the genome consists of 130,930 bp, with a mean G+C content of 52 mol%. The unique DNA is flanked by multiple copies of terminal repeat elements 4205 bp in length, with a mean G+C content of 72 mol%. Analysis revealed 73 open reading frames (ORFs), the majority (62) of which showed homology to other gammaherpesvirus genes. A further subset of nine ORFs is shared with only the related AlHV-1. Three ORFs are entirely unique to OvHV-2, including a spliced homologue of cellular interleukin-10 that retains the exon structure of the cellular gene. The sequence of OvHV-2 is a critical first step in the study of the pathogenesis and treatment of MCF.

Animals↗

PubMed2006

Differential transcription of ovine herpesvirus 2 genes in lymphocytes from reservoir and susceptible species.

Ovine herpesvirus 2 (OvHV-2) is a lymphotropic gammaherpesvirus that asymptomatically infects most sheep, but causes malignant catarrhal fever in cattle, bison, pigs and deer. There is no permissive cell culture system but OvHV-2-infected T lymphocytes can be cultured from diseased animals. We showed that the OvHV-2 genome was in a circular conformation in sheep peripheral blood mononuclear cells and that the latency-associated ORF73 was transcribed, while expression of the productive cycle genes ORF9 (DNA polymerase) and ORF50 (R-transactivator) was barely detectable, suggestive of latency. Doxorubicin treatment of these cells induced the appearance of linear viral DNA and transcription of productive cycle genes along with several viral unique genes. In contrast, cultured T cells from diseased cattle and rabbits contained a mixture of circular and linear genome configurations indicative of a mixture of latently- and productively-infected cells. Most of the OvHV-2 unique genes were transcribed in these cells but ORF50 expression was only seen after doxorubicin treatment indicating a 'leaky' latent pattern of gene expression. 5-azacytidine treatment increased the proportion of circular DNA and inhibited the expression of most of the OvHV-2 unique genes except Ov2.5 (vIL-10) and Ov4.5 (Bcl-2 homologue) in the cattle cell line. These studies provide key insights into the differences in OvHV-2 gene expression in cells from reservoir and susceptible species and, for the first time, an in vitro system for studying the latent and productive phases of the OvHV-2 virus life cycle.

Animals↗

PubMed2006

Orf virus infection and host immunity.

PURPOSE OF REVIEW: A summary of recent advances in our knowledge of the biology of orf virus is presented to illustrate the interaction of a zoonotic pathogen with host skin. This is providing novel and interesting data on the viral mechanism of skin infection and the host response. RECENT FINDINGS: The full genome sequences of two parapoxviruses (orf virus and bovine papular stomatitis virus) have recently been published, defining the parapoxvirus genus at the molecular genetic level. This, along with more detailed characterization of viral immuno-modulatory proteins, is providing an insight into the acquisition of host genes and the mechanism of pathogenesis. A new chemokine-binding protein has been discovered with unique features. Structure-function analysis of the viral granulocyte/macrophage colony-stimulating factor inhibitory factor has revealed a similarity to type 1 cytokine receptors. The viral vascular endothelial growth factor-E stimulates angiogenesis in the skin without the side effects seen with cellular vascular endothelial growth factor-A, and may have therapeutic potential. Finally, orf virus is proving useful both as an immuno-modulator and as a vector for the expression of foreign antigens in non-permissive species. SUMMARY: Orf virus infection provokes a vigorous skin immune response. However, the virus has acquired a range of immuno-modulatory/pathogenesis-related genes that function to limit (at least transiently) the effectiveness of host immunity. With the advent of the orf virus genome sequence, the study of this dynamic process will provide important insights into virus pathogenesis and the host skin immune response to infection.

Animals↗

PubMed2005

A novel subgroup of rhadinoviruses in ruminants.

In the course of investigating the malignant catarrhal fever (MCF) subgroup of rhadinoviruses, seven novel rhadinoviruses were identified in a variety of ruminants, including domestic sheep, bighorn sheep, bison, black-tailed deer, mule deer, fallow deer, elk and addax. Based on the DNA polymerase gene sequences, these newly recognized viruses clustered into a second distinct subgroup in ruminants with three members identified previously in cattle, goats and oryx. Phylogenetic analysis revealed that the currently known ruminant rhadinoviruses appear to comprise three distinct genetic lineages: (i) the MCF subgroup, defined by sequence identity and the presence of the 15A antigenic epitope; (ii) a second distinct subgroup, devoid of the 15A epitope, which contains the previously reported bovine lymphotropic herpesvirus and related viruses; and (iii) a third distinct subgroup represented by Bovine herpesvirus 4. Comparison of phylogenetic trees between the rhadinoviruses and their corresponding hosts further supports the gammaherpesvirus and host co-evolution theory.

Animals↗

PubMed2002

Orf virus immuno-modulation and the host immune response.

Orf virus encodes a range of immuno-modulatory genes that interfere with host anti-virus immune and inflammatory effector mechanisms. The function of these reflects the pathogenesis of orf. The orf virus interferon resistance protein (OVIFNR) and virus IL-10 (vIL-10) inhibit interferon production and activity. In addition the vIL-10 suppresses inflammatory cytokine production by activated macrophages and keratinocytes. The virus GM-CSF inhibitory factor (GIF) is a novel virus protein that binds to and inhibits the biological activity of GM-CSF and IL-2. Together, these immuno-modulators target key effector mechanisms of host anti-virus immunity to allow time for virus replication in epidermal cells.

Animals↗

PubMed2002

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.

Adjuvants, Immunologic↗

PubMed2002

A comparison of the anti-inflammatory and immuno-stimulatory activities of orf virus and ovine interleukin-10.

Orf virus causes pustular skin lesions (orf) in sheep, goats and humans. The virus encodes an interleukin-10 (orfvIL-10) that is identical in amino acid composition to ovine IL-10 (ovIL-10) over the C terminal two-thirds of the polypeptide, but not in the N terminal third. The immuno-suppressive and immuno-stimulatory activities of orfvIL-10 and ovIL-10 were compared. Both orfvIL-10 and ovIL-10 inhibited TNF-alpha and IL-8 cytokine production from stimulated ovine macrophages and keratinocytes and IFN-gamma and GM-CSF production from peripheral blood lymphocytes. OrfvIL-10 and ovIL-10 co-stimulated both ovine and murine mast cell proliferation in conjunction with IL-3 (ovine) or IL-4 (murine). Isoleucine at position 87 (Ile(87)) of the mature human IL-10 (huIL-10) has been reported as essential for the immuno-stimulatory activity of huIL-10. In spite of the differences in amino acids within the N-terminal third of orfvIL-10 compared with ovIL-10 and substitution of Ile(87) with Ala(87) in ovIL-10, these variants of ovIL-10 and orfvIL-10 all co-stimulated mast cell proliferation and inhibited macrophage IL-8 production. As ovIL-10 and orfvIL-10 have a similar structure to huIL-10 and conserved receptor-binding residues, it was concluded that Ile(87) is not essential for IL-10 immuno-stimulatory activity. Finally, ovine keratinocytes do not express ovIL-10. This might explain why orf virus has evolved a viral IL-10.

Amino Acid Sequence↗