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Dixon S, Karrow NA, Borkowski E, Suarez-Vega A, Menzies PI, Kennedy D, Peregrine AS, Mallard BA, Cánovas Á. Identifying hepatic genes regulating the ovine response to gastrointestinal nematodes using RNA-Sequencing. Front Genet 2023; 14:1111426. [PMID: 36873933 PMCID: PMC9981634 DOI: 10.3389/fgene.2023.1111426] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 01/17/2023] [Indexed: 02/19/2023] Open
Abstract
Gastrointestinal nematode (GIN) infections are considered the most important disease of grazing sheep and due to increasing anthelmintic resistance, chemical control alone is inadequate. Resistance to Gastrointestinal nematode infection is a heritable trait, and through natural selection many sheep breeds have higher resistance. Studying the transcriptome from GIN-exposed and GIN-unexposed sheep using RNA-Sequencing technology can provide measurements of transcript levels associated with the host response to Gastrointestinal nematode infection, and these transcripts may harbor genetic markers that can be used in selective breeding programs to enhance disease resistance. The objective of this study was to compare liver transcriptomes of sheep naturally exposed to Gastrointestinal nematode s, with either high or low parasite burdens, to GIN-unexposed control sheep in order to identify key regulator genes and biological processes associated with Gastrointestinal nematode infection. Differential gene expression analysis revealed no significant differentially expressed genes (DEG) between sheep with a high or low parasite burden (p-value ≤0.01; False Discovery Rate (FDR) ≤ 0.05; and Fold-Change (FC) of > ±2). However, when compared to the control group, low parasite burden sheep showed 146 differentially expressed genes (64 upregulated and 82 downregulated in the low parasite burden group relative to the control), and high parasite burden sheep showed 159 differentially expressed genes (57 upregulated and 102 downregulated in the low parasite burden group relative to the control) (p-value ≤0.01; FDR ≤0.05; and FC of > ±2). Among these two lists of significant differentially expressed genes, 86 differentially expressed genes (34 upregulated, 52 downregulated in the parasited group relative to the control) were found in common between the two parasite burden groups compared to the control (GIN-unexposed sheep). Functional analysis of these significant 86 differentially expressed genes found upregulated genes involved in immune response and downregulated genes involved in lipid metabolism. Results of this study offer insight into the liver transcriptome during natural Gastrointestinal nematode exposure that helps provide a better understanding of the key regulator genes involved in Gastrointestinal nematode infection in sheep.
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Affiliation(s)
- Samantha Dixon
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Niel A Karrow
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Emma Borkowski
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Aroa Suarez-Vega
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - Paula I Menzies
- Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Delma Kennedy
- Ontario Ministry of Agriculture, Food and Rural Affairs, Guelph, ON, Canada
| | - Andrew S Peregrine
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Bonnie A Mallard
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Ángela Cánovas
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
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P SS, Chennuru S, Krovvidi S, Chitichoti J. Status of tick-borne haemoprotozoan infection in south Indian sheep in association with variation in Ovar-DRB1 gene. Small Rumin Res 2022. [DOI: 10.1016/j.smallrumres.2022.106817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Stear A, Ali AOA, Brujeni GN, Buitkamp J, Donskow-Łysoniewska K, Fairlie-Clarke K, Groth D, Isa NMM, Stear MJ. Identification of the amino acids in the Major Histocompatibility Complex class II region of Scottish Blackface sheep that are associated with resistance to nematode infection. Int J Parasitol 2019; 49:797-804. [PMID: 31306661 DOI: 10.1016/j.ijpara.2019.05.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 05/01/2019] [Accepted: 05/09/2019] [Indexed: 01/25/2023]
Abstract
Lambs with the Major Histocompatibility Complex DRB1*1101 allele have been shown to produce fewer nematode eggs following natural and deliberate infection. These sheep also possess fewer adult Teladorsagia circumcincta than sheep with alternative alleles at the DRB1 locus. However, it is unclear if this allele is responsible for the reduced egg counts or merely acts as a marker for a linked gene. This study defined the MHC haplotypes in a population of naturally infected Scottish Blackface sheep by PCR amplification and sequencing, and examined the associations between MHC haplotypes and faecal egg counts by generalised linear mixed modelling. The DRB1*1101 allele occurred predominately on one haplotype and a comparison of haplotypes indicated that the causal mutation or mutations occurred in or around this locus. Additional comparisons with another resistant haplotype indicated that mutations in or around the DQB2*GU191460 allele were also responsible for resistance to nematode infections. Further analyses identified six amino acid substitutions in the antigen binding site of DRB1*1101 that were significantly associated with reductions in the numbers of adult T. circumcincta.
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Affiliation(s)
- Abigail Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow, Scotland G61 1QH, UK
| | - Alsagher O A Ali
- Animal Medicine Department, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt
| | - Gholamreza Nikbakht Brujeni
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
| | - Johannes Buitkamp
- Bavarian State Research Center for Agriculture, Institute of Animal Breeding, 85586 Grub, Germany
| | - Katarzyna Donskow-Łysoniewska
- Laboratory of Parasitology, General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Kozielska 4, 01-163 Warsaw, Poland; Department of Parasitology, Institute of Zoology, Faculty of Biology, University of Warsaw, ul. Miecznikowa, 02-096 Warsaw, Poland
| | - Karen Fairlie-Clarke
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow, Scotland G61 1QH, UK
| | - David Groth
- School of Pharmacy and Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
| | - N Mahiza Md Isa
- Faculty of Veterinary Medicine, Universiti Putra Malaysia, UPM, 43400 Serdang, Selangor Darul Ehsan, Malaysia
| | - Michael J Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow, Scotland G61 1QH, UK; Department of Animal, Plant and Soil Science, Agribio, La Trobe University, Bundoora, VIC 3086, Australia.
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Stefan T, Matthews L, Prada JM, Mair C, Reeve R, Stear MJ. Divergent Allele Advantage Provides a Quantitative Model for Maintaining Alleles with a Wide Range of Intrinsic Merits. Genetics 2019; 212:553-564. [PMID: 30952668 PMCID: PMC6553829 DOI: 10.1534/genetics.119.302022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 03/30/2019] [Indexed: 01/28/2023] Open
Abstract
The Major Histocompatibility Complex (MHC) is the most genetically diverse region of the genome in most vertebrates. Some form of balancing selection is necessary to account for the extreme diversity, but the precise mechanism of balancing selection is unknown. Due to the way MHC molecules determine immune recognition, overdominance (also referred to as heterozygote advantage) has been suggested as the main driving force behind this unrivalled diversity. However, both theoretical results and simulation models have shown that overdominance in its classical form cannot maintain large numbers of alleles unless all alleles confer unrealistically similar levels of fitness. There is increasing evidence that heterozygotes containing genetically divergent alleles allow for broader antigen presentation to immune cells, providing a selective mechanism for MHC polymorphism. By framing competing models of overdominance within a general framework, we show that a model based on Divergent Allele Advantage (DAA) provides a superior mechanism for maintaining alleles with a wide range of intrinsic merits, as intrinsically less-fit MHC alleles that are more divergent can survive under DAA. Specifically, our results demonstrate that a quantitative mechanism built from the DAA hypothesis is able to maintain polymorphism in the MHC. Applying such a model to both livestock breeding and conservation could provide a better way of identifying superior heterozygotes, and quantifying the advantages of genetic diversity at the MHC.
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Affiliation(s)
- Thorsten Stefan
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
- Institute of Applied Mathematics and Statistics, University of Hohenheim, 70593 Stuttgart, Germany
| | - Louise Matthews
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
| | - Joaquin M Prada
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
| | - Colette Mair
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
| | - Richard Reeve
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
| | - Michael J Stear
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom
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Ali AOA, Murphy L, Stear A, Fairlie-Clarke K, Nikbakht Brujeni G, Donskow-Łysoniewska K, Groth D, Buitkamp J, Stear MJ. Association of MHC class II haplotypes with reduced faecal nematode egg count and IgA activity in British Texel sheep. Parasite Immunol 2019; 41:e12626. [PMID: 30901091 DOI: 10.1111/pim.12626] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/21/2019] [Accepted: 03/15/2019] [Indexed: 12/18/2022]
Abstract
Nematode infection is one of the principal diseases suffered by sheep and the class II region of the MHC has been repeatedly associated with differences in susceptibility and resistance to infection. The aim of this study was to examine the association of MHC class II haplotypes in a flock of Texel sheep with faecal egg counts and antibody responsiveness. Two haplotypes carried the DRB1*11:01 allele which has previously been associated with reduced egg counts in Scottish Blackface and Suffolk sheep. One of the two haplotypes was associated with reduced egg counts in the Texel breed, and both haplotypes were associated with reduced IgA activity against an extract from fourth-stage larvae. The reduced IgA activity is probably a consequence of reduced numbers of fourth-stage larvae in sheep carrying the resistance allele. The association of specific MHC alleles with reduced egg counts, reduced worm numbers and decreased IgA activity provides a mechanism for the density-dependent regulation of parasite growth and fecundity.
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Affiliation(s)
- Alsagher O A Ali
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Scotland, UK
| | - Lisa Murphy
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Scotland, UK
| | - Abigail Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Scotland, UK
| | - Karen Fairlie-Clarke
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Scotland, UK
| | | | | | - David Groth
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, Perth, Western Australia, Australia
| | - Johannes Buitkamp
- Institute of Animal Breeding, Bavarian State Research Center for Agriculture, Grub, Germany
| | - Michael J Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Scotland, UK.,Department of Animal, Plant and Soil Science, Agribio, La Trobe University, Bundoora, Victoria, Australia
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The genetic architecture of the MHC class II region in British Texel sheep. Immunogenetics 2016; 69:157-163. [PMID: 27921144 PMCID: PMC5316411 DOI: 10.1007/s00251-016-0962-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 11/02/2016] [Indexed: 12/02/2022]
Abstract
Understanding the structure of the major histocompatibility complex, especially the number and frequency of alleles, loci and haplotypes, is crucial for efficient investigation of the way in which the MHC influences susceptibility to disease. Nematode infection is one of the most important diseases suffered by sheep, and the class II region has been repeatedly associated with differences in susceptibility and resistance to infection. Texel sheep are widely used in many different countries and are relatively resistant to infection. This study determined the number and frequency of MHC class II genes in a small flock of Texel sheep. There were 18 alleles at DRB1, 9 alleles at DQA1, 13 alleles at DQB1, 8 alleles at DQA2 and 16 alleles at DQB2. Several haplotypes had no detectable gene products at DQA1, DQB1 or DQB2, and these were defined as null alleles. Despite the large numbers of alleles, there were only 21 distinct haplotypes in the population. The relatively small number of observed haplotypes will simplify finding disease associations because common haplotypes provide more statistical power but complicate the discrimination of causative mutations from linked marker loci.
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Prada Jiménez de Cisneros J, Stear MJ, Mair C, Singleton D, Stefan T, Stear A, Marion G, Matthews L. An explicit immunogenetic model of gastrointestinal nematode infection in sheep. J R Soc Interface 2015; 11:rsif.2014.0416. [PMID: 25121649 PMCID: PMC4233724 DOI: 10.1098/rsif.2014.0416] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Gastrointestinal nematodes are a global cause of disease and death in humans, wildlife and livestock. Livestock infection has historically been controlled with anthelmintic drugs, but the development of resistance means that alternative controls are needed. The most promising alternatives are vaccination, nutritional supplementation and selective breeding, all of which act by enhancing the immune response. Currently, control planning is hampered by reliance on the faecal egg count (FEC), which suffers from low accuracy and a nonlinear and indirect relationship with infection intensity and host immune responses. We address this gap by using extensive parasitological, immunological and genetic data on the sheep–Teladorsagia circumcincta interaction to create an immunologically explicit model of infection dynamics in a sheep flock that links host genetic variation with variation in the two key immune responses to predict the observed parasitological measures. Using our model, we show that the immune responses are highly heritable and by comparing selective breeding based on low FECs versus high plasma IgA responses, we show that the immune markers are a much improved measure of host resistance. In summary, we have created a model of host–parasite infections that explicitly captures the development of the adaptive immune response and show that by integrating genetic, immunological and parasitological understanding we can identify new immune-based markers for diagnosis and control.
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Affiliation(s)
- Joaquín Prada Jiménez de Cisneros
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow G61 1QH, UK
| | - Michael J Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow G61 1QH, UK
| | - Colette Mair
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow G61 1QH, UK
| | - Darran Singleton
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK
| | - Thorsten Stefan
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow G61 1QH, UK
| | - Abigail Stear
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK
| | - Glenn Marion
- Biomathematics and Statistics Scotland, The King's Building, Edinburgh EH9 3JZ, UK
| | - Louise Matthews
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Garscube Campus, Bearsden Road, Glasgow G61 1QH, UK Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow G61 1QH, UK
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Larruskain A, Esparza-Baquer A, Minguijón E, Juste RA, Jugo BM. SNPs in candidate genesMX dynamin-like GTPaseandchemokine (C-C motif) receptor-5are associated with ovine pulmonary adenocarcinoma progression in Latxa sheep. Anim Genet 2015; 46:666-75. [DOI: 10.1111/age.12351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2015] [Indexed: 11/30/2022]
Affiliation(s)
- A. Larruskain
- Genetics, Physical Anthropology and Animal Physiology Department; Faculty of Science and Technology; University of the Basque Country (UPV/EHU); 48080 Bilbao Bizkaia Spain
| | - A. Esparza-Baquer
- Genetics, Physical Anthropology and Animal Physiology Department; Faculty of Science and Technology; University of the Basque Country (UPV/EHU); 48080 Bilbao Bizkaia Spain
| | - E. Minguijón
- Animal Health Department; NEIKER-Tecnalia; 48160 Derio Bizkaia Spain
| | - R. A. Juste
- Animal Health Department; NEIKER-Tecnalia; 48160 Derio Bizkaia Spain
| | - B. M. Jugo
- Genetics, Physical Anthropology and Animal Physiology Department; Faculty of Science and Technology; University of the Basque Country (UPV/EHU); 48080 Bilbao Bizkaia Spain
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Mucha S, Bunger L, Conington J. Genome-wide association study of footrot in Texel sheep. Genet Sel Evol 2015; 47:35. [PMID: 25926335 PMCID: PMC4415250 DOI: 10.1186/s12711-015-0119-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 04/03/2015] [Indexed: 11/10/2022] Open
Abstract
Background This is the first study based on a genome-wide association approach that investigates the links between ovine footrot scores and molecular polymorphisms in Texel sheep using the ovine 50 K SNP array (42 883 SNPs (single nucleotide polymorphisms) after quality control). Our aim was to identify molecular predictors of footrot resistance. Methods This study used data from animals selected from a footrot-phenotyped Texel sheep population of 2229 sheep with an average of 1.60 scoring records per animal. From these, a subset of 336 animals with extreme trait values for footrot was selected for genotyping based on their phenotypic records. De-regressed estimated breeding values (EBV) for footrot were used as pseudo-phenotypes in the genome-wide association analysis. Results Seven SNPs were significant on a chromosome-wise level but the association analysis did not reveal any genome-wise significant SNPs associated with footrot. Based on the current state of knowledge of the ovine genome, it is difficult to clearly link the function of the genes that contain these significant SNPs with a potential role in resistance/susceptibility to footrot. Linkage disequilibrium (LD) was analysed as one of the factors that influence the power of detecting QTL (quantitative trait loci). A mean LD of 0.20 (r2 at a distance of 50 kb between two SNPs) in the population analysed was estimated. LD declined from 0.15 to 0.07 and to 0.04 at distances between two SNPs of 100, 1000 and 2000 kb, respectively. Conclusions Based on a relatively small number of genotyped animals, this study is a first step to search for genomic regions that are involved in resistance to footrot using the ovine 50 K SNP array. Seven SNPs were found to be significant on a chromosome-wise level. No major genome-wise significant QTL were identified.
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Affiliation(s)
- Sebastian Mucha
- Animal and Veterinary Sciences, Scotland's Rural College, Easter Bush, Midlothian, EH25 9RG, , Scotland, UK.
| | - Lutz Bunger
- Animal and Veterinary Sciences, Scotland's Rural College, Easter Bush, Midlothian, EH25 9RG, , Scotland, UK.
| | - Joanne Conington
- Animal and Veterinary Sciences, Scotland's Rural College, Easter Bush, Midlothian, EH25 9RG, , Scotland, UK.
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Allelic polymorphism in the second exon of Ovar-DRB1 in fat-tailed sheep. Vet J 2012; 192:547-9. [DOI: 10.1016/j.tvjl.2011.08.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 04/04/2011] [Accepted: 08/22/2011] [Indexed: 11/20/2022]
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Lee CY, Qin J, Munyard KA, Siva Subramaniam N, Wetherall JD, Stear MJ, Groth DM. Conserved haplotype blocks within the sheep MHC and low SNP heterozygosity in the Class IIa subregion. Anim Genet 2011; 43:429-37. [PMID: 22497756 DOI: 10.1111/j.1365-2052.2011.02268.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This report describes single-nucleotide polymorphisms (SNPs) in the sheep major histocompatibility complex (MHC) class II and class III regions and provides insights into the internal structure of this important genomic complex. MHC haplotypes were deduced from sheep family trios based on genotypes from 20 novel SNPs representative of the class II region and 10 previously described SNPs spanning the class III region. All 30 SNPs exhibited Hardy-Weinberg proportions in the sheep population studied. Recombination within an extended sire haplotype was observed within the class II region for 4 of 20 sheep chromosomes, thereby supporting the presence of separated IIa and IIb subregions similar to those present in cattle. SNP heterozygosity varied across the class II and III regions. One segment of the class IIa subregion manifested very low heterozygosity for several SNPs spanning approximately 120 Kbp. This feature corresponds to a subregion within the human MHC class II region previously described as a 'SNP desert' because of its paucity of SNPs. Linkage disequilibrium (LD) was reduced at the junction separating the putative class IIb and IIa subregions and also between the class IIa and the class III subregions. The latter observation is consistent with either an unmapped physical separation at this location or more likely a boundary characterized by more frequent recombination between two conserved subregions, each manifesting high within-block LD. These results identify internal blocks of loci in the sheep MHC, within which recombination is relatively rare.
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Affiliation(s)
- C Y Lee
- Western Australian Biomedical Research Institute, School of Biomedical Sciences, Curtin University, Perth, Australia
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Small ruminant resistance against gastrointestinal nematodes: a case of Haemonchus contortus. Parasitol Res 2011; 109:1483-500. [PMID: 21842390 DOI: 10.1007/s00436-011-2576-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 07/27/2011] [Indexed: 01/07/2023]
Abstract
Gastrointestinal nematode (GIN) infections are a common constraint to small ruminant industry throughout the world, and among those, haemonchosis has its own significance. Control of GIN primarily relies on the use of anthelmintics, but this approach has become less reliable due to the development of resistance in GINs against commonly used anthelmintics and an increased consumer demand for environmentally friendly animal products. These issues have stimulated investigations to find alternative sustainable control strategies, which are less reliant on anthelmintic input. One of such strategies is breeding of small ruminants for their resistance to the GINs. The susceptibility and resistance of animals to GIN infections varies within and between breeds. Various parasitological, biochemical and immunological parameters are employed to evaluate natural resistance status of animals both in natural pasture and artificial infections. The immune mechanisms responsible for resistance are not completely understood, but it has a significant effect in inherited resistance. Relatively resistant or tolerant animals show better local and generalised immune response as compared to susceptible. Immune response against GINs is influenced by many physiological factors. Determination of specific genes linked with host resistance will provide a valuable approach to find out the molecular mechanism of host resistance to GINs. Resistance has been reported to reduce pasture contamination, which in turn reduces re-infection and thus the requirement of the frequent anthelmintic treatments. The efficiency of control can be increased through objective and accurate identification of genetically tolerant individuals by natural and artificial infections with GINs. Complete resistance is the ultimate solution, but this has generally been ignored as a commercial reality. This paper reviews the published reports on natural resistance in small ruminants and discusses the prospects of developing small ruminants, which could be resistant to GINs.
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The influence of MHC and immunoglobulins a and e on host resistance to gastrointestinal nematodes in sheep. J Parasitol Res 2011; 2011:101848. [PMID: 21584228 PMCID: PMC3092517 DOI: 10.1155/2011/101848] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 02/17/2011] [Accepted: 02/18/2011] [Indexed: 11/18/2022] Open
Abstract
Gastrointestinal nematode parasites in farmed animals are of particular importance due to their effects on production. In Australia, it is estimated that the direct and indirect effects of parasite infestation cost the animal production industries hundreds of millions of dollars each year. The main factors considered by immunologists when studying gastrointestinal nematode infections are the effects the host's response has on the parasite, which immunological components are responsible for these effects, genetic factors involved in controlling immunological responses, and the interactions between these forming an interconnecting multilevel relationship. In this paper, we describe the roles of immunoglobulins, in particular IgA and IgE, and the major histocompatibility complex in resistance to gastrointestinal parasites in sheep. We also draw evidence from other animal models to support the involvement of these immune components. Finally, we examine how IgA and IgE exert their influence and how methods may be developed to manage susceptible animals.
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Larruskain A, Minguijón E, García-Etxebarria K, Moreno B, Arostegui I, Juste RA, Jugo BM. MHC class II DRB1 gene polymorphism in the pathogenesis of Maedi–Visna and pulmonary adenocarcinoma viral diseases in sheep. Immunogenetics 2010; 62:75-83. [DOI: 10.1007/s00251-009-0419-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 12/07/2009] [Indexed: 11/29/2022]
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Stear MJ, Boag B, Cattadori I, Murphy L. Genetic variation in resistance to mixed, predominantly Teladorsagia circumcincta nematode infections of sheep: from heritabilities to gene identification. Parasite Immunol 2009; 31:274-82. [PMID: 19388948 DOI: 10.1111/j.1365-3024.2009.01105.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In cool temperate areas, such as Scotland, sheep are infected by a variety of nematodes but the dominant nematode is Teladorsagia circumcincta. Resistant animals have one or more of the following features: fewer adult nematodes, more inhibited larvae, shorter adult nematodes and decreased production of nematode eggs. In lambs at the end of the first grazing season, the heritability of adult worm length is very strong, whereas the heritability of egg production is moderate. The heritability of worm number is low while there is no detectable genetic variation in the number of inhibited larvae. The major mechanisms underlying resistance to T. circumcincta appear to be the IgA mediated suppression of worm growth and the mast cell mediated regulation of worm number. Mast cell responses are slow to develop, possibly because they are responsible for protein loss and reduced growth of the host. Two genes have been repeatedly associated with resistance to T. Circumcincta: the MHC class II DRB1 locus on chromosome 20 and the interferon-gamma locus on chromosome 3. Although the causative mutations are still unknown both genes are plausible candidates.
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Affiliation(s)
- M J Stear
- Institute of Comparative Medicine, University of Glasgow, Glasgow, UK.
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Genetic analyses of polymorphisms on ovine chromosomes 5 and 20 and their effect on resistance to internal parasites. Small Rumin Res 2009. [DOI: 10.1016/j.smallrumres.2009.03.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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