Cloning and expression of a cDNA encoding ovine granulocyte-macrophage colony-stimulating factor

Genetic Variability of 3'-Proximal Region of Genomes of Orf Viruses Isolated From Sheep and Wild Japanese Serows (Capricornis crispus) in Japan

Orf virus is a prototype species of the genus Parapoxvirus, subfamily Chordopoxvirinae, family Poxviridae. Japanese orf viruses, infecting sheep and wild Japanese serows (Capricornis crispus), have been considered to be genetically closely related based on the sequence identities of the open reading frames (ORFs) 11, 20, and 132 in their genomes. However, since the genome size of orf viruses is about 140 kbp long, genetic variation among Japanese orf viruses remains unclear. In this study, we analyzed the sequences of ORFs 117, 119, 125, and 127 located in the 3′-proximal region of the viral genome using two strains from sheep and three strains from Japanese serows isolated from 1970 to 2007, and compared them with the corresponding sequences of reference orf viruses from other countries. Sequence analysis revealed that ORFs 125 and 127, which encode the inhibitor of apoptosis and viral interleukin (IL)-10, respectively, were highly conserved among the five Japanese orf viruses. However, high genetic variability with deletions or duplications was observed in ORFs 117 and 119, which encode granulocyte macrophage colony-stimulating factor and IL-2 inhibition factor (GIF), and inducer of cell apoptosis, respectively, in one strain from sheep and two strains from Japanese serows. Our results suggest that genetic variability exists in Japanese orf viruses even in the same host species. This is the first report of genetic variability of orf viruses in Japan.

Co-delivery of plasmid-encoded cytokines modulates the immune response to a DNA vaccine delivered by in vivo electroporation

In this study, in vivo electroporation of a DNA vaccine adjuvanted with plasmids encoding different cytokines was investigated in large animals. Sheep were injected intramuscularly with a DNA vaccine encoding an antigen of Haemonchus contortus (pNPA) and plasmids encoding different cytokines followed by in vivo electroporation. Plasmids (pCI) carrying the genes of different cytokines including ovine IL-4(pCI-IL4), IL-10(pCI-IL10), GM-CSF(pCI-GMCSF), and MCP-1alpha(pCI-MCP1alpha), and pCI-IL4+pCI-GMCSF were co-delivered with pNPA. The results showed that co-delivery of pCI-GMCSF or pCI-IL4+pCI-GMCSF significantly enhanced both antibody responses and T cell proliferation responses to the antigen after two DNA immunisations compared to co-delivery of pCI. In contrast, antibody responses of the sheep that received pCI-IL10 were decreased significantly. Other cytokine expressing plasmids did not significantly alter the measured immune responses. Furthermore, co-delivery of pCI-GMCSF increased IgG2 response more than IgG1 responses, suggesting a Th1 bias. However, the increase in IgG2 over IgG1 was less apparent when co-delivery of pCI-IL4 with pCI-GMCSF. Interestingly, the co-delivery of pCI-IL4 alone did not increase the IgG1 titre, suggesting that both pCI-GMCSF and pCI-IL4 are required for optimal IgG1 production. Thus, co-delivery of plasmid-encoded cytokine genes with in vivo electroporation has the ability to effectively modulate immune responses to a DNA vaccine in a large animal.

Monocyte-derived dendritic cells from horses differ from dendritic cells of humans and mice

Dendritic cells (DC) are the initiators of immune responses and are present in most tissues in vivo. To generate myeloid DC from monocytes (MoDC) in vitro the necessary cytokines are granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Using degenerated primers delineated from other species and rapid amplification of cDNA ends reverse transcription-polymerase chain reaction (RACE RT-PCR), the cDNA of equine (eq.) GM-CSF was cloned and found to have a point deletion at the 3'-end of eq.GM-CSF, resulting in a 24-nucleotide extended open reading frame not described in any species thus far. For differentiating eq.MoDC, monocytes were stimulated with eq.GM-CSF and eq.IL-4. The eq.MoDC was analysed by both light and electron microscopy and by flow cytometry and mixed lymphocyte reaction. The eq.MoDC obtained had the typical morphology and function of DC, including the ability to stimulate allogeneic T cells in a mixed lymphocyte reaction. In contrast to the human system, however, monocytes had to be differentiated for 6-7 days before immature DC were obtained. Our data also indicate that lipopolysaccharide or poly(I:C) alone are not sufficient to confer the full phenotypic transition into mature DC. Thus our study contributes to understanding the heterogeneity of immunity and adds important information on the equine immune system, which is clearly distinct from those of mice or man.

Effect of inclusion of serum and granulocyte-macrophage colony stimulating factor on secretion of interferon-tau during the in vitro culture of ovine embryos

In each of three experiments, in vitro-matured and -fertilised zygotes were cultured to Day 7 post insemination in synthetic oviductal fluid (SOF). In Experiment 1, zygotes were cultured in groups in either SOF plus albumin (SOFA) or serum (SOFS) and then blastocysts were cultured individually for a further 24 h without a change of media. In Experiment 2, zygotes were cultured in groups using a 2 x 2 factorial design in SOFA or SOFS, with or without recombinant ovine granulocyte-macrophage colony stimulating factor (GM-CSF; 5 ng mL(-1)). Blastocysts were then cultured individually using a split-plot design in SOFA or SOFS with or without GM-CSF. In Experiment 3, zygotes were cultured in SOFA in which GM-CSF was absent (A) or present (P) during Days 1-3, Days 3-5 or Days 5-7 of IVC in six combinations as follows: AAA, AAP, APP, PPP, PPA and PAA. Serum or GM-CSF increased secretion of interferon (IFN)-tau in Experiments 1 and 2 both between Days 5 and 7 of group culture and during individual culture. Secretion of IFN-tau during individual culture was determined by the medium in which embryos were group cultured and the effects of GM-CSF and serum were not additive. In Experiment 3, the presence of GM-CSF between Days 1 and 3 of culture was responsible for stimulation of secretion of IFN-tau between Days 5 and 7; IFN-tau secretion was detected as early as Day 3 post insemination.

Molecular cloning and characterization of markers and cytokines for equid myeloid cells

The myeloid cell system comprises of monocytes, macrophages (MPhi), dendritic cells (DC), Kupffer cells, osteoclasts or microglia and is also known as the mononuclear phagocytic system (MPS). Essential cytokines to differentiate or activate these cells include GM-CSF or IL-4. Important markers for characterization include CD1, CD14, CD68, CD163 and CD206. All these markers, however, were not cloned or further characterized in equids by use of monoclonal antibodies earlier. To overcome this problem with the present study, two approaches were used. First, we cloned equine cytokines and markers, and second we analyzed cross-reactivity of human homologues or anti-human monoclonal antibodies. For cloning of equine cytokines and markers, we used degenerate primers delineated from other species, or equine-specific primers based on previous information in Genbank. Flow cytometry was used to determine the expression of markers on myeloid cells. Cross-reactivity could be shown for anti-human CD14, CD163 and mannose receptor (CD206) mAbs. Surface markers such as CD1 and CD68 that distinguish MPhi and DC were cloned and sequenced. According to blast homology, equine CD1a and CD1b could be identified and distinguished. With the resulting information, dendritic cells and macrophages of horses may be characterized.

Glycosylation, disulfide bond formation, and the presence of a WSXWS-like motif in the orf virus GIF protein are critical for maintaining the integrity of Binding to ovine granulocyte-macrophage colony-stimulating factor and interleukin-2

Orf virus (ORFV), the type species of the family Parapoxviridae, encodes a protein (GIF) that binds and inhibits the ovine cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2 (IL-2). There is no obvious sequence homology between the ORFV protein and any known mammalian GM-CSF- or IL-2-binding proteins. We demonstrate here that many of the biochemical properties of mammalian GM-CSF receptors that are required for efficient binding of GM-CSF are also critical to the GIF protein for binding to ovine GM-CSF (ovGM-CSF). Site-directed mutagenesis of the GIF protein demonstrated, first, the importance of disulfide bonds, and second, that a sequence motif (WDPWV), related to the WSXWS motif of the type 1 cytokine receptor superfamily, was necessary for biological activity. Finally, glycosylation of the GIF protein was also critical for binding to GM-CSF.

Generation and characterization of ovine dendritic cells derived from peripheral blood monocytes

Dendritic cells (DCs) are professional antigen-presenting cells with a highly immunostimulatory function and the capacity to activate naïve T cells. In recent years the rapid progress in mouse and human DC research can be mainly attributed to the generation of DCs from precursor cells in vitro, although a lack of reagents has hampered DC research in many large animal models. Here we describe the generation and characterization of ovine monocyte-derived DCs in vitro. In addition to the characteristic morphology and non-adherence of DCs, peripheral blood mononuclear cell monocytes cultured with ovine granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) expressed CD11c and major histocompatibility complex (MHC) class II, but did not express CD14. High levels of endocytosis and an ability to stimulate antigen-specific proliferation of CD4 T lymphocytes were also demonstrated.

Regulation of endometrial granulocyte macrophage-colony stimulating factor (GM-CSF) in the ewe

Granulocyte macrophage-colony stimulating factor (GM-CSF) increases ovine interferon-tau (oIFNtau) secretion by ovine conceptuses, but endometrial production of GM-CSF has not been characterized. Endometrial GM-CSF expression was evaluated in ovariectomized ewes implanted with estradiol-17beta (E(2)) and/or progesterone (P(4)) for 14 days, in day 14 cyclic and day 14 pregnant ewes. Relative levels of endometrial GM-CSF mRNA were 3-fold higher in E(2)- and E(2)/P(4)-treated ewes than that of control or P(4)-treated ovariectomized ewes. Levels of endometrial GM-CSF mRNA for cyclic ewes were similar to E(2)- and E(2)/P(4)-treated ewes, but amounts of GM-CSF mRNA in pregnant ewes were 2-fold higher. GM-CSF concentrations in endometrial culture media, determined by GM-CSF bioassay, for cyclic and E(2)/P(4)-treated ovariectomized ewes were 3-fold higher than those of control, E(2)- and P(4)-treated ovariectomized ewes; however, amounts of GM-CSF in pregnant ewes were 2-fold higher. Immunoreactive GM-CSF, examined by western blot, was detected in the culture medium from E(2)/P(4)-treated ovariectomized, cyclic and pregnant ewes. Luminal and glandular epithelia and stromal regions were determined to be sites of GM-CSF expression by immunohistochemistry and in situ hybridization techniques. Data indicate that combined E(2) and P(4) treatment of ovariectomized ewes is sufficient to restore GM-CSF expression to the level found in cyclic ewes; however, GM-CSF mRNA and protein in pregnant ewes is 2-fold greater than in ovariectomized or cyclic ewes. These data suggest that the conceptus, in addition to steroids, may play a role in the regulation of endometrial production of GM-CSF.

Modulating immune responses with dendritic cells: an attainable goal in veterinary medicine?

Dendritic cells (DCs) are antigen presenting cells that potently modulate immune responses with varying outcomes depending on the DC sub-population involved. To understand how DC sub-types arise, it is necessary to determine which factors influence their differentiation. At least three major sub-populations of DCs have been described in mice: CD4+/CD8- "myeloid" DCs, CD4-/CD8+ "lymphoid" DCs and Langerhans cell-derived DCs. Whilst somewhat comparable populations have been described in man, in most other species very little is known. The identification of cytokines which stimulate proliferation of DC precursors, and the observation that the cytokine environment influences the phenotype and the function of the DCs that subsequently develop, has provided a useful tool for evaluating these rare cells. We describe the influence of cytokines on the phenotype of DCs generated in the rat. Using bone marrow cells as the source of precursors we generated "myeloid-type" DCs from the adherent population using granulocyte-macrophage colony stimulating factor (GM-CSF), IL-4 and Flt-3L or "lymphoid-type" DCs from the non-adherent population using cytokines which included IL-7, IL-3, SCF and TNFalpha. In order to facilitate similar approaches to the study of equine DCs we have identified the nucleotide sequence encoding GM-CSF from the m-RNA of equine PBMC stimulated with Concanavalin A, amplified the cDNA by PCR and cloned it in eukaryotic and prokaryotic expression vectors. We report on the structure and function of this molecule.

The immune response to a DNA vaccine can be modulated by co-delivery of cytokine genes using a DNA prime-protein boost strategy

A large-scale DNA vaccination trial was performed in sheep to investigate whether co-delivery of the cytokine genes IL-4, IL-5, IL-15, GM-CSF or IFN-gamma could modulate the immune response generated to an antigen, in a DNA prime-recombinant protein boost regime. Vaccination with the recombinant EG95 protein has been shown to induce protection in sheep from Echinococcus granulosus infection, the causative agent of hydatid disease. Here we demonstrate that vaccination with DNA encoding EG95 effectively primed the humoral response, as judged by high IgG anti-EG95 titres detected one-week after a boost with the recombinant protein. However, by two weeks after protein-boost the titres in the control group had reached levels similar to the groups primed with EG95 DNA. Priming with two doses of DNA vaccine followed by boosting with recombinant protein induced a predominantly IgG1 response. In contrast, priming and boosting with the protein vaccine generated a strong IgG2 response. Co-delivery of the EG95 DNA vaccine with DNA encoding GM-CSF enhanced the antibody titre to EG95 while co-delivery of IFN-gamma or IL-4 encoding DNA appeared to reduce the ability of the DNA vaccine to prime an IgG antibody response. This study has demonstrated the efficacy of the co-delivery of cytokines to modulate immune responses generated in a DNA prime-protein boost 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.

Cloning of a cDNA encoding ovine keratinocyte growth factor

A cDNA encoding the ovine keratinocyte growth factor (KGF) has been cloned. A 622-bp cDNA, containing the entire protein coding region, was amplified from an ovine adenocarcinoma fibroblast cell line. The cDNA was found to share 95% nucleotide identity with dog KGF, 94% identity with human KGF, 90% identity with mouse KGF and 88% identity with rat KGF. The predicted ovine amino-acid sequence shares 98.5, 98, 96 and 94% identity, respectively, with the corresponding dog, human, mouse and rat proteins. The KGF gene is present as a single copy in the ovine genome.

Eosinophil-specific biological activity of recombinant ovine interleukin-5

Recombinant ovine interleukin-5 (rovIL-5) expressed from Chinese hamster ovary (CHO) cells was tested for cell-specific bioreactivity, in vitro, in a soft agar clonogenic assay and in an enzyme-based microassay for eosinophil potentiating activity (EPA). In soft agar assays, colony and cluster formation from sheep bone marrow cells (SBMC) incubated with rovIL-5 was significantly enhanced compared with SBMC incubated with control supernatants from mock-transfected CHO cells. Colony analysis at 14 days demonstrated that for three separate rovIL-5 preparations 45%, 61% and 66% of colonies were eosinophilic, as were 55%-71% of clusters. In contrast, no eosinophil colonies were detected in parallel control cultures. RovIL-5 was also shown to possess potent and dose-responsive EPA, on the basis of eosinophil peroxidase (EPO) and arylsulphatase (EAS) assay in 7 day SBMC cultures. This activity was inhibited in a dose-responsive manner by TRFK-5, a rat anti-murine IL-5 monoclonal antibody (MAb) previously shown to have cross-reactivity in the ovine EPA assay. The results demonstrate that rovIL-5 exhibited eosinophil-specific properties similar to those of IL-5 derived from other mammalian species.

Early immunopathological events in experimental ovine paratuberculosis

An experimental oral infection of neonatal (< 2 weeks old) lambs with a cervine isolate of Mycobacterium avium subspecies paratuberculosis (M.a. paratuberculosis), the causal agent of ruminant paratuberculosis (Johne's disease) was used to investigate bacteriological, histopathological and immunological changes during the early (up to 8 weeks) post-infection phase. In vitro culture for mycobacteria was positive in one faecal and three mesenteric lymph node (MLN) samples from the eight infected lambs. All mycobacterial isolates from MLN were identified as M.a. paratuberculosis by polymerase chain reaction (PCR). Small-to-medium sized focal granulomata were observed in jejunal (JPP) and ileal Peyer's patches (IPP) from four of the eight infected lambs. Compared with controls, JPP from all infected lambs had significantly (p < 0.05) higher proportions of CD8+ and CD2+ lymphocytes, and there were significantly (p < 0.05) fewer cells expressing B lymphocyte-associated markers in IPP and MLN. The T/B cell ratio was significantly (p < 0.05) increased in both JPP and MLN from infected lambs. The expression of a range of genes for cytokines was examined using specific reverse transcriptase PCR (RT-PCR) amplification of messenger RNA (mRNA) template isolated from MLN, JPP and IPP from both groups of animals. Densitometric analyses indicated that, in infected animals, MLN expressed significantly (p < 0.05) more mRNA for TNF-alpha: JPP had significantly increased (p < 0.05) mRNA for GM-CSF and significantly decreased (p < 0.05) mRNA for IL-4 and IFN-gamma. Infected lambs had significantly (p < 0.05) decreased titres of both circulating IgG and gut mycobacteria-associated IgG antibody. Infection was not associated with any consistent changes in lymphocyte reactivity to specific mycobacterial antigens, IFN-gamma release into supernatants from in vitro intestinal lymphocyte cultures or gut IgA antibody levels.

Differential levels of mRNAs for cytokines, the interleukin-2 receptor and class II DR/DQ genes in ovine interstitial pneumonia induced by maedi visna virus infection

The relative levels of selected cytokine, interleukin-2 receptor, class II DR and DQ RNAs, and maedi visna virus (MVV) RNA were measured by reverse-transcriptase polymerase chain reaction (RT-PCR) in the lungs of sheep with natural maedi visna virus infection (n = 8) and a group of age/sex/breed-matched MVV seronegative sheep (n = 4). These animals were divided into two groups, irrespective of serostatus, according to the severity of lymphocytic interstitial pneumonia. The severity of lung lesions was determined by clinical sign, lung weight, and lesion sore in the lungs measured by three pathologic parameters. Sheep with lung lesions showed hyperelevated levels of granulocyte-macrophage colony-stimulating factor upregulated gamma-interferon, interleukin 2 receptor, and interleukins 1 beta, 4, and 10 mRNAs. Class II mRNAs were found not to be elevated in the lungs of sheep with lung lesions. Tumor necrosis factor alpha and transforming growth factor beta 1 mRNA levels were similar in all sheep lungs studied. We discuss the major roles played by granulocyte-macrophage colony-stimulating factor and type 2 cytokines in the pathogenesis of this disease and the possible stimulation of the production of these cytokines by viral surface glycoproteins.

Factors controlling haemopoiesis in ovine long-term bone marrow cultures

We describe an adaptation of the Dexter technique for obtaining ovine long-term bone marrow cultures able to sustain haemopoiesis in vitro for long periods. Two inocula of bone marrow cells collected at three-five weeks interval, in IMDM supplemented with fetal calf serum (10%), horse serum (10%) and hydrocortisone (5 x 10(-7) M), gave rise to the growth of an adherent cell layer which supported, in most cases, active haemopoiesis for up to 15 weeks. The cell layer was composed of macrophages, fibroblasts and adipocytes. Haemopoietic cells formed large foci of "cobblestone" areas. Haemopoietic progenitors were also released into the supernatant medium and were detectable by clonogenic assay. Granulocytes and monocyte-macrophages differentiated in the cultures in constant proportion until week five, when the monocytic lineage superseded the myelocytic one. These cultures, between weeks five and twelve, produced colony forming cells in a constant pattern, indicating the presence and self renewing of early haemopoietic progenitor cells.

Refined crystal structure and mutagenesis of human granulocyte-macrophage colony-stimulating factor

The crystal structure of recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) has been refined against data extending to a resolution of approximately 2.4 A along a* and approximately 1.9 A along b* and c*. Anisotropic scale factors of B11 = -20.8 A2, B22 = 7.4 A2, B33 = 13.3 A2 corrected for the more rapid fall of diffraction in the a* direction. The anisotropy correlates with the weak crystal packing interactions along the a axis. In addition to apolar side chains in the protein core, there are 10 buried hydrogen bonding residues. Those residues involved in intramolecular hydrogen bonding to main chain atoms are better conserved than those hydrogen bonding to other side chain atoms; 24 solvation sites are observed at equivalent positions in the two molecules in the asymmetric unit, and the strongest among these are located in clefts between secondary structural elements. No buried water sites are seen. Two surface clusters of hydrophobic side chains are located near the expected receptor binding regions. Mutagenesis of 11 residues on the helix A/helix C face confirms the importance of Glu-21 and shows that Gly-75 and Gln-86, located on helix C, each cause a greater than fourfold drop in activity. Glu-21 and Gly-75, but not Gln-86, are structurally equivalent to residues involved in the growth hormone binding to its receptor.

Development of a sandwich ELISA for ovine granulocyte/macrophage colony-stimulating factor

Recombinant ovine granulocyte/macrophage colony-stimulating factor (rOv GM-CSF) has been expressed in Chinese hamster ovary cells. A stable, cloned line of these cells has been established which secretes high levels (40 mu g ml(-1)) of rOv GM-CSF. Three murine monoclonal antibodies (mAbs) were produced which reacted with rOv GM-CSF on Western blots. These mAbs also neutralised the activity of both recombinant and native Ov GM-CSF in a bone marrow haemopoietic progenitor cell assay. Two of the mAbs, which recognise mutually exclusive epitopes, were selected for the development of a sandwich enzyme-linked immunosorbent assay (ELISA) to measure GM-CSF in biological samples of ovine origin.

Increased intestinal TNF-alpha, IL-1 beta and IL-6 expression in ovine paratuberculosis

Mycobacterium avium subspecies paratuberculosis is an intracellular parasite of intestinal macrophages and causes a chronic granulomatous enteritis in sheep and other ruminants (paratuberculosis or Johne's disease). Macrophages can be produced a variety of immunoregulatory cytokines that may influence mycobacterial killing and produce disordered inflammation within the gut. In this study, messenger RNA (mRNA) was extracted from intestinal tissue from control and multibacillary diseased sheep and profiles for the cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, transforming growth factor-beta1 (TGF-beta1) and granulocyte-macrophage colony stimulating factor (GM-CSF) were semi-quantified using reverse transcriptase polymerase chain reactions (RT-PCR). Infected intestinal tissues had significantly increased mRNA for TNF-alpha, IL-1beta and IL-6 but TGF-beta1 and GM-CSF mRNA levels were significantly different from controls. Supernatants from in vitro intestinal cultures were assayed for TNF-alpha activity using the PK(15)-1512 cytotoxicity bioassay and levels were significantly raised in diseased samples. TNF-alpha was not detected in any serum samples. Further analysis on intestinal tissues from sheep with the different, paucibacillary, form of the disease showed significant elevation of TNF-alpha mRNA but not other cytokines tested. Increased pro-inflammatory cytokine expression in the intestine coincident with a failed or misdirected immune response may contribute to the pathogenesis of paratuberculosis and the persistence of a chronic inflammatory state.

Production and characterisation of ovine GM-CSF expressed in mammalian and bacterial cells

A cDNA encoding ovine granulocyte-macrophage colony-stimulating factor (GM-CSF) was isolated and two forms of recombinant ovine GM-CSF were produced. A glycosylated form was produced in mammalian cells infected with a recombinant vaccinia virus encoding ovine GM-CSF. Recombinant ovine GM-CSF was also produced in Escherichia coli and purified by affinity chromatography. Both forms of the protein were detected by ovine GM-CSF-specific monoclonal antibodies, and exhibited activity on ovine bone marrow haemopoetic progenitor cells.

The survival and growth of ovine afferent lymph dendritic cells in culture depends on tumour necrosis factor-alpha and is enhanced by granulocyte-macrophage colony-stimulating factor but inhibited by interferon-gamma

An in vitro culture system is described which allows an analysis of the signals responsible for the survival, growth and functional maturation of afferent lymph dendritic cells (ALDC), a subpopulation of migrating dermal dendritic cells involved in antigen carriage and presentation to T-cells. Purified ALDC survived and grew for up to 30 days in lymph node conditioned medium and survived 14 days in recombinant ovine (rov) TNF-alpha whereas none were detected after 24 h in rov GM-CSF, rov IFN-gamma or rh M-CSF. However, when rov GM-CSF was added to cultures along with rov TNF-alpha, increased numbers of ALDC compared with input numbers (growth) were recorded on Days 14 and 21. In contrast, when 50-200 units ml-1 of rov IFN-gamma were added to cultures of ALDC along with TNF-alpha or rov TNF-alpha plus rov GM-CSF, cell survival and growth was inhibited. Antibody blocking studies confirmed the cytokine specificity of these effects. ALDC cultured in rov TNF-alpha or rov TNF-alpha plus rov GM-CSF retained MHC Class-II and ov CD-1 antigen expression and accessory function for autologous ov CD-4 T-cell proliferation, although at reduced levels compared with freshly isolated cells. Neither fresh nor cultured ALDC expressed coagulation factor XIIIa.

Cross-reactivity amongst recombinant haematopoietic cytokines from different species for sheep bone-marrow eosinophils

The potentiating effects of a variety of recombinant cytokines on the survival or proliferation (or both) of sheep bone marrow eosinophils in vitro were assessed by means of cell-specific enzyme microassays for eosinophil peroxidase (EPO) and eosinophil arylsulphatase (EAS). In this system recombinant human and mouse interleukin 5 (rhIL5 and rmIL5, respectively) had potent eosinophil potentiating activity (EPA) that was reciprocally inhibited by polyclonal anti-rhIL5 and anti-rmIL5 antibodies and by a specific monoclonal anti-rmIL5 (TRFK5). Recombinant ovine granulocyte-macrophage colony-stimulating factor (rovGM-CSF) and interleukin 3 (rovIL3) also had marked EPA for sheep cells, and the activity of the former was blocked by a mouse monoclonal anti-rovGM-CSF. The equivalent human and murine recombinant GM-CSFs and IL3s had no detectable effect on sheep eosinophils, nor did antibodies against them influence the EPA of any of the ovine cytokines. The evidence presented provides further support to the concept that the structure, biological reactivity and cell specificity of IL5 is highly conserved in mammals, whereas other eosinopoietins such as IL3 and GM-CSF are more species-specific.

The in-vitro detection and quantitation of ovine bone marrow precursors of multipotential colony-forming cells

The in-vitro detection and quantitation of ovine bone-marrow precursors of multipotential colony-forming cells (pre-multi CFC) is described. After 5 and 10 days in liquid culture containing medium conditioned by long term bone marrow stromal cell layers (SCM) along with lymph node-conditioned medium (LNCM) or recombinant ovine interleukin-3 (rov IL-3), increased numbers of multi CFC developed from bone marrow precursors as detected by subsequent soft agar clonogenic assay of mixed phenotype colonies. From a variety of cytokines and conditioned media (CM) tested that included recombinant ovine granulocyte-macrophage colony-stimulating factor (rov GM-CSF) and recombinant human macrophage colony-stimulating factor (rhu M-CSF), the combination of SCM plus LNCM or rov IL-3 supported the maximum numbers of multi-CFC in liquid culture. The development of multi CFC from precursors was demonstrated in bone marrow cells treated with a dose of mafosfamide that inactivated > 98% of clonogenic CFC. Quantitative limit dilution analysis of 10 bone marrow samples revealed an average of one pre-multi CFC per 34147 unfractionated cells (range 1:14230-81433). Pre-multi CFC were enriched 38-fold (average) in the 2.0% of bone marrow cells remaining after depletion of lymphocytes and myeloid/erythroid cells expressing the antigen recognized by monoclonal antibody 175. The quantitative assay also revealed preliminary evidence that the pre-multi CFC may consist of subpopulations differing in their sensitivity to mafosfamide.

Cloning of a cDNA encoding ovine interleukin-3

A cDNA encoding the ovine hematopoietic growth factor interleukin-3 (IL-3), has been cloned. A 560-bp cDNA, containing the entire protein coding region, was amplified from activated mesenteric lymph node cells. The cDNA was found to share 58% nucleotide identity with hIL-3 and 48% identity with mIL-3. The predicted ovine amino-acid sequence shares 36 and 30% identity, respectively, with the corresponding human and murine proteins.

Cloning and sequencing of an ovine granulocyte colony-stimulating factor cDNA

A cDNA encoding an ovine (ov) granulocyte colony-stimulating factor (G-CSF) was cloned by polymerase chain reaction, using primers based on the 5' and 3' nucleotide (nt) sequence of the bovine (bov) G-CSF cDNA. RNA was isolated from IFN-gamma and LPS-stimulated alveolar macrophages. The isolated ovG-CSF cDNA is 522 bp in length and does not include coding sequence for a secretory signal peptide. The nt sequence is 95% identical to the bovG-CSF nt sequence, and includes conservation of 5 cysteine residues. The deduced amino acid (aa) sequence of the mature ovG-CSF protein shares 96%, 82% and 68% homology with the bov, human and murine mature G-CSF proteins, respectively. The estimated molecular weight of the 174 aa G-CSF protein is 18.8 kilodaltons.

Current research on ovine cytokines

Cytokines are key mediators of the immune system, dictating the quality of the host response to infection. The importance of such immune mediators to the development of immune and inflammatory responses has emerged from work in mouse and man, however it has now become necessary to produce the equivalent (and novel) cytokines in ruminants. Over the past three years recombinant DNA techniques have allowed the cloning of numerous ovine cytokines. These include interleukins -1, -2 and -3 (IL-1, -2 and -3), interferon-gamma (IFN-gamma), ovine trophoblast protein (oTP-1), tumour necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF). The predicted amino-acid sequences of these ovine proteins show varying degrees of similarity with the equivalent human proteins thus explaining why some of the cytokines are not biologically cross-reactive between species. Recombinant ovine proteins have been produced for IFN-gamma, oTP-1, IL-1, IL-3 and GM-CSF. Their biological activities are very similar to those of their human counterparts. Although it is too early to tell whether the recombinant ovine proteins will be of use in the treatment or prophylaxis of infectious disease, work in cattle and pigs has indicated the potential usefulness of cytokines in this role.

Use of enzyme microassay to detect eosinophil potentiating activity of cytokines in sheep

Microplate assays for eosinophil peroxidase (EPO) and arylsulphatase (EAS) have been established as indices of eosinophil survival/proliferation in sheep bone marrow cell (SBMC) cultures. Cell specificity was confirmed using density-fractionated and differentially depleted SBMC populations. Several recombinant cytokines including interleukins 3 (IL-3) and 5 (IL-5), and granulocyte macrophage-colony stimulating factor (GM-CSF), but not macrophage-CSF (M-CSF), had demonstrable eosinophil-potentiating activity on the basis of enhanced EPO and EAS activities in treated, compared with untreated, SBMC cultures. Effects of IL-5 were abrogated in the presence of a specific monoclonal anti-IL-5 antibody. The results indicate that measurement of EPO and EAS in cultured SBMC offers a simple and effective method for detecting eosinophil potentiating activity in the ovine.