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Topic:Molecular biology

Molecular biology in horses involves the study of molecular processes and genetic mechanisms that underpin equine physiology and health. This field encompasses the analysis of DNA, RNA, proteins, and other biomolecules to understand gene expression, genetic variation, and cellular functions in horses. Techniques such as genomic sequencing, gene expression profiling, and molecular diagnostics are employed to explore topics like hereditary diseases, performance traits, and immune responses in equines. This page assembles peer-reviewed research studies and scholarly articles that investigate the molecular biology of horses, focusing on genetic research, molecular techniques, and their applications in equine science.
Evaluation of FOXC2 as a candidate gene for chronic progressive lymphedema in draft horses.
Veterinary journal (London, England : 1997)    August 1, 2006   Volume 174, Issue 2 397-399 doi: 10.1016/j.tvjl.2006.05.023
Young AE, Bower LP, Affolter VK, De Cock HE, Ferraro GL, Bannasch DL.Chronic progressive lymphedema (CPL) is a debilitating condition identified in Clydesdales, Shires and Belgian draft horses and results in progressive swelling of the lower legs associated with the development of thick skin folds, ulcerations, fibrosis and marked hyperkeratosis. The result is severe discomfort and recurrent secondary infection, often requiring euthanasia. Due to the delayed onset, many horses are bred prior to diagnosis. CPL has only been documented in three related draft horse breeds, suggesting a genetic cause. Determining the molecular basis would enable owners to test hors...
Ferritin-catalyzed consumption of hydrogen peroxide by amine buffers causes the variable Fe2+ to O2 stoichiometry of iron deposition in horse spleen ferritin.
Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry    July 29, 2006   Volume 11, Issue 8 1075-1086 doi: 10.1007/s00775-006-0141-6
Zhang B, Wilson PE, Watt GD.Ferritin catalyzes the oxidation of Fe2+ by O2 to form a reconstituted Fe3+ oxy-hydroxide mineral core, but extensive studies have shown that the Fe2+ to O2 stoichiometry changes with experimental conditions. At Fe2+ to horse spleen ferritin (HoSF) ratios greater than 200, an upper limit of Fe2+ to O2 of 4 is typically measured, indicating O2 is reduced to 2H2O. In contrast, a lower limit of Fe2+ to O2 of approximately 2 is measured at low Fe2+ to HoSF ratios, implicating H2O2 as a product of Fe2+ deposition. Stoichiometric amounts of H2O2 have not been measured, and H2O2 is proposed to react ...
[PCR-RFLP analysis of the mtDNA Cytb gene in three different horse breeds].
Yi chuan = Hereditas    July 28, 2006   Volume 28, Issue 8 933-938 
Li JL, Shi YF, Bu RQ, Mang L.Restriction endonucleases, namely BamH I, Taq I, Hae III, Rsa I and Hinc II, were used to analyze the polymorphism of partial mtDNA Cytb gene sequences from 256 horses 6 types (Thoroughbred, Sanhe, Wuzhumuqin, Xinihe, Wushen and Pony) including the imported breed, cultivated breed and local breed. The products of endonuclease digestion were run on 8% non-denaturing polyacrylamide gel electrophoresis and detected by silver staining. Results indicated BamH I and Taq I polymorphism. In all 7 restriction patterns were defected that could be sorted into 3 haplotypes, of which haplotypes I and III w...
Development of the Lipizzan horse breed.
Reproduction in domestic animals = Zuchthygiene    July 28, 2006   Volume 41, Issue 4 280-285 doi: 10.1111/j.1439-0531.2006.00726.x
Dovc P, Kavar T, Sölkner H, Achmann R.The development and a brief history of the Lipizzan horse breed are reviewed. The contribution of several breeds, some of them already extinct, to the development of the Lipizzan horse, gives it a special status representing an important gene pool. This well-documented breed is a part of the common European natural and cultural heritage. Breeding practices establishing stallion and mare family lines as well as availability of pedigrees are described. Molecular analysis of mitochondrial DNA (mtDNA) and microsatellite data allowed us to analyse the structure of the Lipizzan population, to estima...
Derivation, maintenance, and induction of the differentiation in vitro of equine embryonic stem cells.
Methods in molecular biology (Clifton, N.J.)    July 19, 2006   Volume 329 59-79 doi: 10.1385/1-59745-037-5:59
Saito S, Sawai K, Minamihashi A, Ugai H, Murata T, Yokoyama KK.We describe here the isolation and maintenance of pluripotent embryonic stem (ES) cells from equine blastocysts that have been frozen and thawed. Equine ES cells appear to maintain a normal diploid karyotype in culture. These cells express markers that are characteristic of mouse ES cells, namely, alkaline phosphatase, stage-specific-embryonic antigen 1, STAT3, and Oct4. We also describe protocols for the induction of differentiation in vitro to neural precursor cells in the presence of basic fibroblast growth factor (bFGF), epidermal growth factor, and platelet-derived growth factor and to he...
Cloning and pharmacological characterization of the equine adenosine A2A receptor: a potential therapeutic target for the treatment of equine endotoxemia.
Journal of veterinary pharmacology and therapeutics    July 19, 2006   Volume 29, Issue 4 243-253 doi: 10.1111/j.1365-2885.2006.00746.x
Brandon CI, Vandenplas M, Dookwah H, Linden J, Murray TF.The aim of the current study was to clone the equine adenosine A(2A) receptor gene and to establish a heterologous expression system to ascertain its pharmacologic profile via radioligand binding and functional assays. An eA(2A)-R expression construct was generated by ligation of the eA(2A) cDNA into the pcDNA3.1 expression vector, and stably transfected into human embryonic kidney cells (HEK). Binding assays identified those clones expressing the eA(2A)-R, and equilibrium saturation isotherm experiments were utilized to determine dissociation constants (K(D)), and receptor densities (B(max)) ...
Molecular cloning and gonadotropin-dependent regulation of equine prostaglandin F2alpha receptor in ovarian follicles during the ovulatory process in vivo.
Prostaglandins & other lipid mediators    July 7, 2006   Volume 80, Issue 1-2 81-92 doi: 10.1016/j.prostaglandins.2006.05.020
Sayasith K, Bouchard N, Doré M, Sirois J.The progressive rise in gonadotropins prior to ovulation triggers a marked increase in intrafollicular levels of prostaglandin F(2alpha)(PGF(2alpha)), which is known to interact with PGF(2alpha) receptor (FP). Little is known about the regulation of FP during ovulation. This study was undertaken to characterize the equine FP and its gonadotropin-dependent regulation in preovulatory follicles prior to ovulation. The full-length equine FP encodes a 366-amino acid protein that is 82-93% homologous to other species. Using semi-quantitative RT-PCR/Southern blot, we showed that FP mRNA expression wa...
Temporal relationship between proliferating and apoptotic hormone-producing and endothelial cells in the equine corpus luteum.
Reproduction (Cambridge, England)    July 4, 2006   Volume 132, Issue 1 111-118 doi: 10.1530/rep.1.01051
Aguilar J, Fraser HM, Wilson H, Clutton E, Shaw DJ, Watson ED.The temporal relationship between endothelial cell death, vascular regression and the death of hormone-producing cells in the mare has not been established. To determine the dynamics of cell proliferation and death throughout the luteal phase, corpora lutea were studied at the early, mid- and late luteal phase, and after treatment with cloprostenol in the mid-luteal phase to induce premature luteolysis. Changes in cell proliferation and apoptosis were investigated utilising specific markers (phosphorylated histone-3 and activated caspase-3 respectively). Histone-3 positive cells were most abun...
Getting a grip on strangles: recent progress towards improved diagnostics and vaccines.
Veterinary journal (London, England : 1997)    July 3, 2006   Volume 173, Issue 3 492-501 doi: 10.1016/j.tvjl.2006.05.011
Waller AS, Jolley KA.'Strangles', caused by infection with the bacterium Streptococcus equi, remains one of the most commonly diagnosed and important infectious diseases of horses world-wide. This review discusses the diagnosis and pathogenesis of strangles with particular attention to the significance of persistent infections in disease transmission and the rapid progress now being made towards the development of effective preventative vaccines. It is now possible combine recent sequence data from the N-terminal region of the SeM protein and reassign the SeM alleles using the on-line database http://pubmlst.org/s...
von Willebrand factor A1 domain can adequately substitute for A3 domain in recruitment of flowing platelets to collagen.
Journal of thrombosis and haemostasis : JTH    June 29, 2006   Volume 4, Issue 10 2151-2161 doi: 10.1111/j.1538-7836.2006.02111.x
Bonnefoy A, Romijn RA, Vandervoort PA, VAN Rompaey I, Vermylen J, Hoylaerts MF.Binding of von Willebrand factor (VWF) to platelet GPIbalpha and to collagen is attributed to VWF A1 and A3 domains, respectively. Objective: Using VWF, VWF lacking A1 (DeltaA1-VWF) or A3 (DeltaA3-VWF) and VWF with defective A3 (H1786A-VWF), in combination with recombinant A1 (residues 1262-1492) or A3 (residues 1671-1878), fused to glutathione-S-transferase (GST-A1 and GST-A3), we have re-investigated the role of A1 in platelet recruitment to surfaces of collagen. Results: In flow, measurable binding of DeltaA3-VWF occurred to horse tendon, but also to human type III collagen. GST-A1 and GST-...
Miscibility of binary monolayers at the air-water interface and interaction of protein with immobilized monolayers by surface plasmon resonance technique.
Langmuir : the ACS journal of surfaces and colloids    June 28, 2006   Volume 22, Issue 14 6195-6202 doi: 10.1021/la0605642
Wang Y, Du X.The miscibility and stability of the binary monolayers of zwitterionic dipalmitoylphosphatidylcholine (DPPC) and cationic dioctadecyldimethylammonium bromide (DOMA) at the air-water interface and the interaction of ferritin with the immobilized monolayers have been studied in detail using surface pressure-area isotherms and surface plasmon resonance technique, respectively. The surface pressure-area isotherms indicated that the binary monolayers of DPPC and DOMA at the air-water interface were miscible and more stable than the monolayers of the two individual components. The surface plasmon re...
Equine insect bite hypersensitivity: immunoblot analysis of IgE and IgG subclass responses to Culicoides nubeculosus salivary gland extract.
Veterinary immunology and immunopathology    June 23, 2006   Volume 113, Issue 1-2 99-112 doi: 10.1016/j.vetimm.2006.04.009
Hellberg W, Wilson AD, Mellor P, Doherr MG, Torsteinsdottir S, Zurbriggen A, Jungi T, Marti E.Insect bite hypersensitivity (IBH) is an allergic dermatitis of horses caused by IgE-mediated reactions to bites of Culicoides and sometimes Simulium spp. The allergens causing IBH are probably salivary gland proteins from these insects, but they have not yet been identified. The aim of our study was to identify the number and molecular weight of salivary gland extract (SGE) proteins derived from Culicoides nubeculosus which are able to bind IgE antibodies (ab) from the sera of IBH-affected horses. Additionally, we sought to investigate the IgG subclass (IgGa, IgGb and IgGT) reactivity to thes...
Molecular cross-sectional survey of gastric habronemosis in horses.
Veterinary parasitology    June 23, 2006   Volume 141, Issue 3-4 285-290 doi: 10.1016/j.vetpar.2006.05.021
Traversa D, Iorio R, Capelli G, Paoletti B, Bartolini R, Otranto D, Giangaspero A.Gastric habronemosis of horses caused by Habronema microstoma and Habronema muscae (Nematoda, Spirurida) is characterized by catarrhal gastritis, diarrhoea, progressive weight loss and ulcers. Despite its importance in the equine industry and in clinical practice, knowledge of the epidemiology of this infection is still incomplete as diagnosis in live animals is challenging. A two-step semi-nested PCR assay using ribosomal DNA (rDNA) markers has recently been used for the molecular diagnosis in vivo of gastric habronemosis based on the detection of H. microstoma and/or H. muscae DNA in equine ...
Age-related expression of molecular regulators of hypertrophy and maturation in articular cartilage.
Journal of orthopaedic research : official publication of the Orthopaedic Research Society    June 22, 2006   Volume 24, Issue 8 1773-1781 doi: 10.1002/jor.20227
Semevolos SA, Nixon AJ, Fortier LA, Strassheim ML, Haupt J.The purpose of this study was to determine changes in the expression of regulatory molecules in normal equine articular cartilage throughout development up to 18 months of age. The hypothesis was that expression of these regulatory molecules would decrease from birth to postpubescence. Cartilage was harvested from normal femoropatellar or scapulohumeral joints from 34 fresh horse cadavers. Horses were placed in four age groups [prenatal (n = 5); prepubertal, 0-6 months (n = 11); pubertal, 7-14 months (n = 13); and postpubertal, 15-18 months (n = 5)]. Indian hedgehog (Ihh), Gli1, Gli3, Patched1...
Equine peripheral blood-derived progenitors in comparison to bone marrow-derived mesenchymal stem cells.
Stem cells (Dayton, Ohio)    June 14, 2006   Volume 24, Issue 6 1613-1619 doi: 10.1634/stemcells.2005-0264
Koerner J, Nesic D, Romero JD, Brehm W, Mainil-Varlet P, Grogan SP.Fibroblast-like cells isolated from peripheral blood of human, canine, guinea pig, and rat have been demonstrated to possess the capacity to differentiate into several mesenchymal lineages. The aim of this work was to investigate the possibility of isolating pluripotent precursor cells from equine peripheral blood and compare them with equine bone marrow-derived mesenchymal stem cells. Human mesenchymal stem cells (MSCs) were used as a control for cell multipotency assessment. Venous blood (n = 33) and bone marrow (n = 5) were obtained from adult horses. Mononuclear cells were obtained by Fico...
A comparative kinetic analysis of the reactivity of plant, horse, and human respiratory cytochrome c towards cytochrome c oxidase.
Biochemical and biophysical research communications    June 12, 2006   Volume 346, Issue 3 1108-1113 doi: 10.1016/j.bbrc.2006.06.022
Rodríguez-Roldán V, García-Heredia JM, Navarro JA, Hervás M, De la Cerda B, Molina-Heredia FP, De la Rosa MA.Two synthetic genes coding for human and Arabidopsis cytochrome c, respectively, have been designed and constructed, and the recombinant proteins have been over-expressed in Escherichia coli cells. Thus a comparative analysis of the two heme proteins, including horse cytochrome c as a reference, has been performed. In addition to their physico-chemical properties, the redox behavior of the three proteins has been analyzed by following the kinetics of both their reduction by flavin semiquinones (lumiflavin, riboflavin, and FMN) and oxidation by cytochrome c oxidase. The resulting data indicate ...
Extraction and detection of mRNA from horsehair.
The Journal of veterinary medical science    June 8, 2006   Volume 68, Issue 5 503-506 doi: 10.1292/jvms.68.503
Sato T, Sato G, Shoji Y, Itou T, Sakai T.After RNA extraction from horsehair shafts and roots, the mRNAs of beta-actin, muscle-type phosphofructokinase, and transforming growth factor-beta1 were detected by reverse transcription polymerase chain reaction assay. Low amounts of RNA were present in the horsehair. These specific mRNA transcripts were readily detected when more than three hair roots were used. However, detection of the mRNA transcripts was difficult in the hair shaft. These findings indicate that the small amounts of residual RNA in horsehair roots can be utilized as samples for molecular biological analysis.
A new approach for the diagnosis of myiasis of animals: the example of horse nasal myiasis.
Veterinary parasitology    June 8, 2006   Volume 141, Issue 1-2 186-190 doi: 10.1016/j.vetpar.2006.04.031
Traversa D, Otranto D.The myiasis caused by larvae of Rhinoestrus purpureus and Rhinoestrus usbekistanicus (Diptera, Oestridae) are of importance in the horse medicine since it causes severe respiratory diseases. Therefore an accurate diagnosis of rhinoestrosis is central to its epidemiology and control. This paper describes concisely a molecular diagnostic tool that overcomes the current inherent diagnostic constraints and, therefore, is of importance to understand the actual incidence and epidemiology of this myiasis in live horses.
Thrombospondin-4 and cartilage oligomeric matrix protein form heterooligomers in equine tendon.
Connective tissue research    June 7, 2006   Volume 47, Issue 2 85-91 doi: 10.1080/03008200600584124
Södersten F, Ekman S, Schmitz M, Paulsson M, Zaucke F.Injuries of the equine superficial digital flexor tendon are common in racing horses. Knowledge of the tendon matrix composition is crucial to understand physiological and pathological processes in the tendon. The aim of this study was to analyze TSP-4 expressed in equine tendon. Equine tendons were extracted with 10 mM EDTA-containing buffer and TSP-4 purified with ion-exchange chromatography followed by heparin affinity chromatography. The purified TSP-4 was analyzed by one- and two-dimensional SDS-PAGE, immunoblotting, and MALDI-TOF mass spectrometry. Purified TSP-4 gave bands reacting with...
Assessment of the catabolic effects of interleukin-1beta on proteoglycan metabolism in equine cartilage cocultured with synoviocytes.
American journal of veterinary research    June 3, 2006   Volume 67, Issue 6 957-962 doi: 10.2460/ajvr.67.6.957
Gregg AJ, Fortier LA, Mohammed HO, Mayr KG, Miller BJ, Haupt JL.To evaluate the effects of interleukin (IL)-1beta on proteoglycan metabolism in equine cartilage explants when cultured in the presence of synoviocytes. Methods: Samples of cartilage and synovium collected from the femoropatellar joints of three 2- to 3-year-old horses. Methods: 3 experimental groups were established: cartilage explants only, synoviocytes only, and cartilage explants-synoviocytes in coculture. In each group, samples were cultured with or without IL-1beta (10 ng/mL) for 96 hours. Glycosaminoglycan (GAG) content of cartilage and medium samples was measured by use of a spectropho...
Expression of molecular markers in blood of neonatal foals with sepsis.
American journal of veterinary research    June 3, 2006   Volume 67, Issue 6 1045-1049 doi: 10.2460/ajvr.67.6.1045
Pusterla N, Magdesian KG, Mapes S, Leutenegger CM.To determine gene expression of selected molecular markers (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, IL-8, IL-10, procalcitonin [PCT], and transforming growth factor [TGF]-beta) in the blood of healthy and sick foals. Methods: 28 sick foals without sepsis, 21 foals with sepsis, and 21 healthy foals. Methods: Total RNA was extracted from blood samples and converted into complementary DNA (cDNA). Gene expression was measured for the molecular markers by use of real-time PCR assay, and final quantitation was performed with the comparative threshold cycle method. Results: S...
Chromosomal assignments for the equine AMPK family genes.
Animal genetics    June 1, 2006   Volume 37, Issue 3 293-294 doi: 10.1111/j.1365-2052.2006.01431.x
Dranchak PK, Ekenstedt KJ, Valberg SJ, Chowdhary BP, Raudsepp T, Mickelson JR.No abstract available
Horse microsatellites and their amenability to comparative equid genetics.
Animal genetics    June 1, 2006   Volume 37, Issue 3 258-261 doi: 10.1111/j.1365-2052.2006.01422.x
Moodley Y, Baumgarten I, Harley EH.We investigated the applicability of microsatellite primers, designed in horses, for use in plains and mountain zebras. Fifteen of the 20 tested horse-isolated primer pairs reliably amplified polymorphic loci in two wild equid species. We used this information to assess whether levels of genetic variation and repeat size differed in species from which microsatellites were isolated and in closely related target species. Target equid species exhibited similar levels of genetic variation to the horse, the species from which primers were originally isolated. We show that ascertainment bias results...
Intermediate amyloid oligomers of lysozyme: Is their cytotoxicity a particular case or general rule for amyloid?
Biochemistry. Biokhimiia    May 31, 2006   Volume 71, Issue 5 505-512 doi: 10.1134/s0006297906050063
Malisauskas M, Darinskas A, Zamotin VV, Gharibyan A, Kostanyan IA, Morozova-Roche LA.In the current study we investigated the molecular mechanisms of cytotoxicity of amyloid oligomers of horse milk lysozyme. We have shown that lysozyme forms soluble amyloid oligomers and protofibrils during incubation at pH 2.0 and 4.5 and 57 degrees C. These structures bind the amyloid-specific dyes thioflavin T and Congo Red, and their morphology and size were analyzed by atomic force microscopy. Monomeric lysozyme and its fibrils did not affect the viability of three cell types used in our experiments including primary murine neurons and fibroblasts, as well as neuroblastoma cell line IMR-3...
Human chorionic gonadotropin-dependent induction of an equine aldo-keto reductase (AKR1C23) with 20alpha-hydroxysteroid dehydrogenase activity during follicular luteinization in vivo.
Journal of molecular endocrinology    May 25, 2006   Volume 36, Issue 3 449-461 doi: 10.1677/jme.1.01987
Brown KA, Boerboom D, Bouchard N, Doré M, Lussier JG, Sirois J.Aldo-keto reductases (AKRs) are multifunctional enzymes capable of acting on a wide variety of substrates, including sex steroids. AKRs having 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activity can reduce progesterone to 20alpha-hydroxy-4-pregnen-3-one (20alpha-DHP), a metabolite with lower affinity for the progesterone receptor. The objective of this study was to investigate the regulation of equine AKR1C23 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The equine AKR1C23 cDNA was cloned and shown to encode a 322 amino acid protein that is conserved (71-81...
Comparative mapping of oculocutaneous albinism type II (OCA2), transient receptor potential cation channel, subfamily M member 1 (TRPM1) and two equine microsatellites, ASB08 and 1CA43, among four equid species by fluorescence in situ hybridization.
Cytogenetic and genome research    May 24, 2006   Volume 114, Issue 1 93A doi: 10.1159/000091935
Bellone R, Lear T, Adelson DL, Bailey E.No abstract available
Determination of the phosphorylation level and deamidation susceptibility of equine beta-casein.
Proteomics    May 13, 2006   Volume 6, Issue 12 3707-3717 doi: 10.1002/pmic.200500728
Girardet JM, Miclo L, Florent S, Mollé D, Gaillard JL.beta-Casein was isolated from Haflinger mare's milk by RP-HPLC, and displayed microheterogeneity by urea-electrophoresis and 2-DE probably due to a variable degree of phosphorylation. To investigate the degree of phosphorylation, the primary structure of equine beta-casein was determined by tryptic hydrolysis and MS of peptides released and by MS of the protein treated by alkaline phosphatase. The molecular mass found for the apo-form of Haflinger mare's beta-casein (25 514 +/- 3 Da) was close to the theoretical mass of the reported sequence (GenBank AAG43954) modified by insertion of a region...
Isolation and identification of Taylorella asinigenitalis from the genital tract of a stallion, first case of a natural infection.
Veterinary microbiology    May 7, 2006   Volume 116, Issue 4 294-300 doi: 10.1016/j.vetmic.2006.04.027
Båverud V, Nyström C, Johansson KE.Contagious equine metritis (CEM), caused by Taylorella equigenitalis, is a widely known highly contagious genital equine disease that is transmitted venereally. A new bacterium, Taylorella asinigenitalis resembling T. equigenitalis was recently isolated from three American donkey jacks, at routine testing for CEM. The purpose of this study was to identify and characterize a strain of Taylorella sp. from the genital tract of a stallion. Swab samples for culture of T. equigenitalis were taken from urethral fossa, urethra and penile sheath of a 3-year-old stallion of the Ardennes breed when it wa...
Selection of a set of reliable reference genes for quantitative real-time PCR in normal equine skin and in equine sarcoids.
BMC biotechnology    April 27, 2006   Volume 6 24 doi: 10.1186/1472-6750-6-24
Bogaert L, Van Poucke M, De Baere C, Peelman L, Gasthuys F, Martens A.Real-time quantitative PCR can be a very powerful and accurate technique to examine gene transcription patterns in different biological conditions. One of the critical steps in comparing transcription profiles is accurate normalisation. In most of the studies published on real-time PCR in horses, normalisation occurred against only one reference gene, usually GAPDH or ACTB, without validation of its expression stability. This might result in unreliable conclusions, because it has been demonstrated that the expression levels of so called "housekeeping genes" may vary considerably in different t...
Extended phylogeny of equine arteritis virus: division into new subgroups.
Journal of veterinary medicine. B, Infectious diseases and veterinary public health    April 22, 2006   Volume 53, Issue 2 55-58 doi: 10.1111/j.1439-0450.2006.00916.x
Mittelholzer C, Stadejek T, Johansson I, Baule C, Ciabatti I, Hannant D, Paton D, Autorino GL, Nowotny N, Belák S.To determine a conclusive phylogeny, equine arteritis viruses from Italy, Austria, Hungary, Sweden, South Africa and other parts of the world were analysed by reverse-transcription polymerase chain reaction amplification and direct sequencing. The nucleotide sequences corresponding to the variable part of the large glycoprotein GP5, specified by open reading frame 5, were compared and added to a previously published phylogenetic tree in which a clear division between 'European' and 'American' type viruses had been established. Adding the sequences determined in this study and new sequences ret...