Polymorphisms in the CTLA4 promoter sequence are associated with canine hypoadrenocorticism.

BACKGROUND: Canine hypoadrenocorticism is an immune-mediated endocrinopathy that shares both clinical and pathophysiological similarities with Addison's disease in humans. Several dog breeds are overrepresented in the disease population, suggesting that a genetic component is involved, although this is likely to be polygenic. Previous research has implicated CTLA4 as a potential susceptibility gene. CTLA4 is an important regulator of T cell function and polymorphisms/mutations in CTLA4 have been associated with a number of autoimmune phenotypes in both humans and rodent models of autoimmunity. The aim of the current study was to undertake a case:control association study of CTLA4 promotor polymorphisms in three dog breeds, cocker spaniels, springer spaniels and West Highland white terriers (WHWT). RESULTS: Polymorphisms in the CTLA4 promoter were determined by PCR and sequence-based typing. There were significant associations with three promoter haplotypes in cocker spaniels (p = 0.003). A series of SNPs were also associated with hypoadrenocorticism in cocker spaniels and springer spaniels, including polymorphisms in predicted NFAT and SP1 transcription factor binding sites. CONCLUSIONS: This study provides further evidence that CTLA4 promotor polymorphisms are associated with this complex genetic disease and supports an immune mediated aetiopathogenesis of canine hypoadrenocorticism.

Development and optimization of a hybridization technique to type the classical class I and class II B genes of the chicken MHC.

The classical class I and class II molecules of the major histocompatibility complex (MHC) play crucial roles in immune responses to infectious pathogens and vaccines as well as being important for autoimmunity, allergy, cancer and reproduction. These classical MHC genes are the most polymorphic known, with roughly 10,000 alleles in humans. In chickens, the MHC (also known as the BF-BL region) determines decisive resistance and susceptibility to infectious pathogens, but relatively few MHC alleles and haplotypes have been described in any detail. We describe a typing protocol for classical chicken class I (BF) and class II B (BLB) genes based on a hybridization method called reference strand-mediated conformational analysis (RSCA). We optimize the various steps, validate the analysis using well-characterized chicken MHC haplotypes, apply the system to type some experimental lines and discover a new chicken class I allele. This work establishes a basis for typing the MHC genes of chickens worldwide and provides an opportunity to correlate with microsatellite and with single nucleotide polymorphism (SNP) typing for approaches involving imputation.

DLA class II risk haplotypes for autoimmune diseases in the bearded collie offer insight to autoimmunity signatures across dog breeds.

BACKGROUND: Primary hypoadrenocorticism (Addison's disease, AD) and symmetrical lupoid onychodystrophy (SLO) are two clinical conditions with an autoimmune etiology that occur in multiple dog breeds. In man, autoimmunity is associated with polymorphisms in immune-related genes that result in a reduced threshold for, or defective regulation of, T cell activation. The major histocompatibility complex (MHC) class II genes encode molecules that participate in these functions, and polymorphisms within these genes have been associated with autoimmune conditions in dogs and humans. Bearded collies have a relatively high prevalence of autoimmune diseases, particularly AD and SLO. Our study assessed the relationship between particular MHC (dog leukocyte antigen, DLA) class II haplotypes and the two autoimmune diseases most common in this breed. Moreover, five unrelated breeds at increased risk for AD were studied for comparative purposes and analyzed in the context of extant literature. RESULTS: A single DLA class II three-locus haplotype, determined by sequence-based typing, was associated with increased risk for AD (DLA-DRB1*009:01/DQA1*001:01/DQB1*008:02) in bearded collies. Comparative analysis with the five additional breeds showed limited allele sharing, with DQA1*001:01 and DQB1*002:01 being the only alleles observed in all breeds. A distinct three-locus risk haplotype (DLA-DRB1*001:01/DQA1*001:01/DQB1*002:01) was associated with AD in the West Highland white terrier and Leonberger. Two different risk haplotypes were associated with increased risk for SLO in the bearded collie (DLA-DRB1*018:01/DQA1*001:01/DQB1*002:01 and DLA-DRB1*018:01/DQA1*001:01/ DQB1*008:02). CONCLUSION: Two-locus DQ haplotypes composed of DLA-DQA1*001:01 in association with DLA-DQB1*002:01 or DLA-DQB1*008:02 make up the four risk haplotypes identified in the present study and are also found in other risk haplotypes previously associated with diabetes mellitus and hypothyroidism across different dog breeds. Our findings build upon previously published data to suggest that this two-locus (DQ) model serves as a good indicator for susceptibility to multiple organ-specific autoimmune diseases in the canine population. However, it is also clear that additional loci are necessary for actual disease expression. Investigation of affected and unaffected dogs carrying these predisposing DQ haplotype signatures may allow for the identification of those additional genetic components that determine autoimmune disease expression and organ specificity.

Comparative MHC nomenclature: report from the ISAG/IUIS-VIC committee 2018.

Significant progress has been made over the last decade in defining major histocompatibility complex (MHC) diversity at the nucleotide, allele, haplotype, diplotype, and population levels in many non-human species. Much of this progress has been driven by the increased availability and reduced costs associated with nucleotide sequencing technologies. This report provides an update on the activities of the comparative MHC nomenclature committee which is a standing committee of both the International Society for Animal Genetics (ISAG) and the International Union of Immunological Societies (IUIS) where it operates under the umbrella of the Veterinary Immunology Committee (VIC). A previous report from this committee in 2006 defined the role of the committee in providing guidance in the development of a standardized nomenclature for genes and alleles at MHC loci in non-human species. It described the establishment of the Immuno Polymorphism Database, IPD-MHC, which continues to provide public access to high quality MHC sequence data across a range of species. In this report, guidelines for the continued development of a universal MHC nomenclature framework are described, summarizing the continued development of each species section within the IPD-MHC project.

Genetic diversity and population structure of African village dogs based on microsatellite and immunity-related molecular markers.

The village and street dogs represent a unique model of canine populations. In the absence of selective breeding and veterinary care, they are subject mostly to natural selection. Their analyses contribute to understanding general mechanisms governing the genetic diversity, evolution and adaptation. In this study, we analyzed the genetic diversity and population structure of African village dogs living in villages in three different geographical areas in Northern Kenya. Data obtained for neutral microsatellite molecular markers were compared with those computed for potentially non-neutral markers of candidate immunity-related genes. The neutral genetic diversity was similar to other comparable village dog populations studied so far. The overall genetic diversity in microsatellites was higher than the diversity of European pure breeds, but it was similar to the range of diversity observed in a group composed of many European breeds, indicating that the African population has maintained a large proportion of the genetic diversity of the canine species as a whole. Microsatellite marker diversity indicated that the entire population is subdivided into three genetically distinct, although closely related subpopulations. This genetical partitioning corresponded to their geographical separation and the observed gene flow well correlated with the communication patterns among the three localities. In contrast to neutral microsatellites, the genetic diversity in immunity-related candidate SNP markers was similar across all three subpopulations and to the European group. It seems that the genetic structure of this particular population of Kenyan village dogs is mostly determined by geographical and anthropogenic factors influencing the gene flow between various subpopulations rather than by biological factors, such as genetic contribution of original migrating populations and/or the pathogen-mediated selection. On the other hand, the study of oldest surviving dogs suggested a biological mechanism, i.e. a possible advantage of the overal heterozygosity marked by the the microsatellite loci analyzed.

No evidence of prenatal diversifying selection at locus or supertype levels in the dog MHC class II loci.

BACKGROUND: Despite decades of studying, the mechanisms maintaining high diversity in the genes of the Major Histocompatibility Complex (MHC) are still puzzling scientists. In addition to pathogen recognition and other functions, MHC molecules may act prenatally in mate choice and in maternal-foetal interactions. These interactions are potential selective mechanisms that increase genetic diversity in the MHC. During pregnancy, immune response has a dual role: the foetus represents foreign tissue compared to mother, but histo-incompatibility is required for successful pregnancy. We have studied the prenatal selection in MHC class II loci (DLA-DQA1, DLA-DQB1 and DLA-DRB1) in domestic dogs by comparing the observed and expected offspring genotype proportions in 110 dog families. Several potential selection targets were addressed, including the peptide-binding site, the MHC locus, three-locus haplotype and supertype levels. For the supertype analysis, the first canine supertype classification was created based on in silico analysis of peptide-binding amino-acid polymorphism. RESULTS: In most loci and levels, no deviation from the expected genotype frequencies was observed. However, one peptide-binding site in DLA-DRB1 had an excess of heterozygotes among the offspring. In addition, if the father shared a DLA-DRB1 allele with the mother, that allele was inherited by the offspring more frequently than expected, suggesting the selective advantage of a histo-compatible foetus, in contrast to our expectations. CONCLUSIONS: We conclude that there is some evidence of post-copulatory selection at nucleotide site level in the MHC loci of pet dogs. But due to no indication of selection at locus, three-locus, or supertype levels, we estimated that the prenatal selection coefficient is less than 0.3 in domestic dogs and very likely other factors are more important in maintaining the genetic diversity in MHC loci.

Single nucleotide polymorphisms in major histocompatibility class II haplotypes are associated with potential resistance to inflammatory bowel disease in German shepherd dogs.

German shepherd dogs (GSD) in the UK are at increased risk of developing the Inflammatory Bowel Disaese (IBD). IBD is believed to be a multifactorial immune mediated disease affecting genetically predisposed dogs. The aim of the current study was to investigate whether susceptibility to IBD in GSD is associated with the major histocompatibility complex (MHC) class II locus (Dog Leukocyte Antigen, DLA). Sequence-based genotyping of the three polymorphic DLA genes DLA-DRB1, -DQA1 and -DQB1 was performed in 56 GSDs affected by IBD and in 50 breed-matched controls without any history of gastrointestinal signs. The haplotype DLA-DRB1*015:02-DQA1*006:01-DQB1*023:01 was found to be present only in the control population and was associated with a reduced risk of IBD (P<0.001). In contrast, the haplotype DLA-DRB1*015:01-DQA1*006:01-DQB1*003:01 was associated with IBD (Odds ratio [OR]=1.93, confidence interval [CI]=1.02-3.67, P=0.05). This study has identified an association between DLA-type and canine IBD, supporting the immunogenetic aetiology and immunopathogenesis of this disease.

MYD88 and functionally related genes are associated with multiple infections in a model population of Kenyan village dogs.

The purpose of this study was to seek associations between immunity-related molecular markers and endemic infections in a model population of African village dogs from Northern Kenya with no veterinary care and no selective breeding. A population of village dogs from Northern Kenya composed of three sub-populations from three different areas (84, 50 and 55 dogs) was studied. Canine distemper virus (CDV), Hepatozoon canis, Microfilariae (Acantocheilonema dracunculoides, Acantocheilonema reconditum) and Neospora caninum were the pathogens studied. The presence of antibodies (CDV, Neospora), light microscopy (Hepatozoon) and diagnostic PCR (Microfilariae) were the methods used for diagnosing infection. Genes involved in innate immune mechanisms, NOS3, IL6, TLR1, TLR2, TLR4, TLR7, TLR9, LY96, MYD88, and three major histocompatibility genes class II genes were selected as candidates. Single nucleotide polymorphism (SNP) markers were detected by Sanger sequencing, next generation sequencing and PCR-RFLP. The Fisher´s exact test for additive and non-additive models was used for association analyses. Three SNPs within the MYD88 gene and one TLR4 SNP marker were associated with more than one infection. Combined genotypes and further markers identified by next generation sequencing confirmed associations observed for individual genes. The genes associated with infection and their combinations in specific genotypes match well our knowledge on their biological role and on the role of the relevant biological pathways, respectively. Associations with multiple infections observed between the MYD88 and TLR4 genes suggest their involvement in the mechanisms of anti-infectious defenses in dogs.

Evaluation of a DLA-79 allele associated with multiple immune-mediated diseases in dogs.

Immune-mediated diseases are common and life-threatening disorders in dogs. Many canine immune-mediated diseases have strong breed predispositions and are believed to be inherited. However, the genetic mutations that cause these diseases are mostly unknown. As many immune-mediated diseases in humans share polymorphisms among a common set of genes, we conducted a candidate gene study of 15 of these genes across four immune-mediated diseases (immune-mediated hemolytic anemia, immune-mediated thrombocytopenia, immune-mediated polyarthritis (IMPA), and atopic dermatitis) in 195 affected and 206 unaffected dogs to assess whether causative or predictive polymorphisms might exist in similar genes in dogs. We demonstrate a strong association (Fisher's exact p = 0.0004 for allelic association, p = 0.0035 for genotypic association) between two polymorphic positions (10 bp apart) in exon 2 of one allele in DLA-79, DLA-79*001:02, and multiple immune-mediated diseases. The frequency of this allele was significantly higher in dogs with immune-mediated disease than in control dogs (0.21 vs. 0.12) and ranged from 0.28 in dogs with IMPA to 0.15 in dogs with atopic dermatitis. This allele has two non-synonymous substitutions (compared with the reference allele, DLA-79*001:01), resulting in F33L and N37D amino acid changes. These mutations occur in the peptide-binding pocket of the protein, and based upon our computational modeling studies, are likely to affect critical interactions with the peptide N-terminus. Further studies are warranted to confirm these findings more broadly and to determine the specific mechanism by which the identified variants alter canine immune system function.

Breed differences in development of anti-insulin antibodies in diabetic dogs and investigation of the role of dog leukocyte antigen (DLA) genes.

Administration of insulin for treatment of diabetes mellitus in dogs can stimulate an immune response, with a proportion of animals developing anti-insulin antibodies (AIA). For an IgG antibody response to occur, this would require B cell presentation of insulin peptides by major histocompatibility complex (MHC) class II molecules, encoded by dog leukocyte antigen (DLA) genes, in order to receive T-cell help for class switching. DLA genes are highly polymorphic in the dog population and vary from breed to breed. The aim of the present study was to evaluate AIA reactivity in diabetic dogs of different breeds and to investigate whether DLA genes influence AIA status. Indirect ELISA was used to determine serological reactivity to insulin in diabetic dogs, treated with either a porcine or bovine insulin preparation. DLA haplotypes for diabetic dogs were determined by sequence-based typing of DLA-DRB1, -DQA1 and -DQB1 loci. Significantly greater insulin reactivity was seen in treated diabetic dogs (n=942) compared with non-diabetic dogs (n=100). Relatively few newly diagnosed diabetic dogs (3/109) were found to be AIA positive, although this provides evidence that insulin autoantibodies might be involved in the pathogenesis of the disease in some cases. Of the diabetic dogs treated with a bovine insulin preparation, 52.3% (182/348) were AIA positive, compared with 12.6% (75/594) of dogs treated with a porcine insulin preparation, suggesting that bovine insulin is more immunogenic. Breeds such as dachshund, Cairn terrier, miniature schnauzer and Tibetan terrier were more likely to develop AIA, whereas cocker spaniels were less likely to develop AIA, compared with crossbreed dogs. In diabetic dogs, DLA haplotype DRB1*0015--DQA1*006--DQB1*023 was associated with being AIA positive, whereas the haplotype DLA-DRB1*006--DQA1*005--DQB1*007 showed an association with being AIA negative. These research findings suggest that DLA genes influence AIA responses in treated diabetic dogs.

A Multi-Breed Genome-Wide Association Analysis for Canine Hypothyroidism Identifies a Shared Major Risk Locus on CFA12.

Hypothyroidism is a complex clinical condition found in both humans and dogs, thought to be caused by a combination of genetic and environmental factors. In this study we present a multi-breed analysis of predisposing genetic risk factors for hypothyroidism in dogs using three high-risk breeds--the Gordon Setter, Hovawart and the Rhodesian Ridgeback. Using a genome-wide association approach and meta-analysis, we identified a major hypothyroidism risk locus shared by these breeds on chromosome 12 (p = 2.1x10(-11)). Further characterisation of the candidate region revealed a shared ~167 kb risk haplotype (4,915,018-5,081,823 bp), tagged by two SNPs in almost complete linkage disequilibrium. This breed-shared risk haplotype includes three genes (LHFPL5, SRPK1 and SLC26A8) and does not extend to the dog leukocyte antigen (DLA) class II gene cluster located in the vicinity. These three genes have not been identified as candidate genes for hypothyroid disease previously, but have functions that could potentially contribute to the development of the disease. Our results implicate the potential involvement of novel genes and pathways for the development of canine hypothyroidism, raising new possibilities for screening, breeding programmes and treatments in dogs. This study may also contribute to our understanding of the genetic etiology of human hypothyroid disease, which is one of the most common endocrine disorders in humans.

Clinical features of idiopathic inflammatory polymyopathy in the Hungarian Vizsla.

BACKGROUND: A retrospective study of the clinicopathological features of presumed and confirmed cases of idiopathic inflammatory polymyopathy in the Hungarian Vizsla dog and guidelines for breeding. RESULTS: 369 medical records were reviewed (1992-2013) and 77 Hungarian Vizslas were identified with a case history consistent with idiopathic inflammatory polymyopathy. Inclusion criteria were: group 1 (confirmed diagnosis); histopathology and clinical findings compatible with an inflammatory polymyopathy and group 2 (probable diagnosis); clinical findings compatible with a polymyopathy including dysphagia, sialorrhea, temporal muscle atrophy, elevated serum creatine kinase (CK) activity, and sufficient clinical history to suggest that other neuromuscular disorders could be ruled out. Some group 2 dogs had muscle biopsy, which suggested muscle disease but did not reveal an inflammatory process. The mean age of onset was 2.4 years; male dogs were slightly overrepresented. Common presenting signs were dysphagia, sialorrhea, masticatory muscle atrophy, and regurgitation. Common muscle histopathological findings included degenerative and regenerative changes, with multifocal mononuclear cell infiltration with lymphoplasmacytic myositis of variable severity. A positive response to immunosuppressive treatment supported an immune-mediated aetiology. The mean age at death and survival time were 6.4 and 3.9 years, respectively. Recurrence of clinical signs and aspiration pneumonia were common reasons for euthanasia. CONCLUSIONS: Diagnosis of Vizsla idiopathic inflammatory polymyopathy can be challenging due to lack of specific tests, however the presence of dysphagia, regurgitation and masticatory muscle atrophy in this breed with negative serological tests for masticatory muscle myositis and myasthenia gravis, along with muscle biopsies suggesting an inflammatory process, support the diagnosis. However, there is an urgent need for a more specific diagnostic test. The average of inbreeding coefficient (CoI) of 16.3% suggests an increased expression of a Dog Leukocyte Antigen Class II haplotype, leading to an increased disease risk. The prognosis remains guarded, as treatment can only manage the disease. Recurrence of clinical signs and perceived poor quality of life are the most common reasons for humane euthanasia.

Restricted dog leucocyte antigen (DLA) class II haplotypes and genotypes in Beagles.

Beagles are commonly used in vaccine trials as part of the regulatory approval process. Genetic restriction within this breed and the impact this might have on vaccine responses are rarely considered. This study was designed to characterise diversity of dog leucocyte antigen (DLA) class II genes in a breeding colony of laboratory Beagles, whose offspring are used in vaccine studies. DLA haplotypes were determined by PCR and sequence-based typing from genomic DNA extracted from blood. Breeding colony Beagles had significantly different DLA haplotype frequencies in comparison with pet Beagles and both groups showed limited DLA diversity. Restricted DLA class II genetic variability within Beagles might result in selective antigen presentation and vaccine responses that are not necessarily representative of those seen in other dog breeds.

Genetics of canine anal furunculosis in the German shepherd dog.

Canine anal furunculosis (AF) is characterised by ulceration and fistulation of perianal tissue and is a disease that particularly affects German shepherd dogs (GSDs). There are some similarities between AF and perianal Crohn's disease (CD) in man. An immune-mediated aetiopathogenesis for AF has been suggested due to tissue pathology, a major histocompatibility complex (MHC) association and clinical response to ciclosporin. Genome-wide association studies (GWAS) can be conducted in dogs with fewer markers and individuals than would be required in a human study. A discovery GWAS was performed on 21 affected and 25 control GSDs from the UK. No SNPs reached genome-wide significance levels at this stage. However, 127 nominally associated SNPs were genotyped in further 76 cases and 191 controls from the UK and Finland. Sequencing of these regions was undertaken to discover novel genetic variation. Association testing of these variants in the UK and Finnish cohorts revealed nine significantly associated SNPs, six of which cause non-synonymous changes in protein sequence. The ADAMTS16 and CTNND2 gene regions were most significantly associated with disease. Members of the butyrophilin protein family, important in intestinal inflammatory regulation, were also associated with disease, but their independence from the MHC region remains to be established. The CTNND2 gene region is also interesting as this locus was implicated in human ulcerative colitis and CD, albeit at a different candidate gene: DAP. We suggest that this represents a common association between inflammatory bowel disease-related conditions in both species and believe that future studies will strengthen this link.

Searching for "monogenic diabetes" in dogs using a candidate gene approach.

BACKGROUND: Canine diabetes is a common endocrine disorder with an estimated breed-related prevalence ranging from 0.005% to 1.5% in pet dogs. Increased prevalence in some breeds suggests that diabetes in dogs is influenced by genetic factors and similarities between canine and human diabetes phenotypes suggest that the same genes might be associated with disease susceptibility in both species. Between 1-5% of human diabetes cases result from mutations in a single gene, including maturity onset diabetes of the adult (MODY) and neonatal diabetes mellitus (NDM). It is not clear whether monogenic forms of diabetes exist within some dog breeds. Identification of forms of canine monogenic diabetes could help to resolve the heterogeneity of the condition and lead to development of breed-specific genetic tests for diabetes susceptibility. RESULTS: Seventeen dog breeds were screened for single nucleotide polymorphisms (SNPs) in eighteen genes that have been associated with human MODY/NDM. Six SNP associations were found from five genes, with one gene (ZFP57) being associated in two different breeds. CONCLUSIONS: Some of the genes that have been associated with susceptibility to MODY and NDM in humans appear to also be associated with canine diabetes, although the limited number of associations identified in this study indicates canine diabetes is a heterogeneous condition and is most likely to be a polygenic trait in most dog breeds.

A candidate gene analysis of canine hypoadrenocorticism in 3 dog breeds.

Canine hypoadrenocorticism is believed to be an immune-related condition. It is rare in the overall dog population but shows a breed-related predisposition with Standard poodles and Portuguese water dogs having a greater prevalence of the condition. It shares many similarities with human primary adrenal insufficiency and is believed to be a naturally occurring, spontaneous model for the human condition. Short haplotype blocks and low levels of linkage disequilibrium in the human genome mean that the identification of genetic contributors to the condition requires large sample numbers. Pedigree dogs have high linkage disequilibrium and long haplotypes within a breed, increasing the potential of identifying novel genes that contribute to canine genetic disease. We investigated 222 SNPs from 42 genes that have been associated or may be implicated in human Addison's disease. We conducted case-control analyses in 3 pedigree dog breeds (Labrador retriever: affected n = 30, unaffected = 76; Cocker Spaniel: affected n = 19, unaffected = 53; Springer spaniel: affected n = 26, unaffected = 46) and identified 8 associated alleles in genes COL4A4, OSBPL9, CTLA4, PTPN22, and STXBP5 in 3 pedigree breeds. Association with immune response genes PTPN22 and CTLA4 in certain breeds suggests an underlying immunopathogenesis of the disease. These results suggest that canine hypoadrenocorticism could be a useful model for studying comparative genetics relevant to human Addison's disease.

Alleles of the major histocompatibility complex play a role in the pathogenesis of pancreatic acinar atrophy in dogs.

Exocrine pancreatic insufficiency (EPI) is a disease wherein pancreatic acinar cells fail to synthesize and secrete sufficient amounts of digestive enzymes for normal digestion of food. EPI affects many dog breeds, with a dramatically higher prevalence in the German shepherd dog (GSD) population. In this breed and perhaps others, EPI most often results from degeneration of the acinar cells of the pancreas, a hereditary disorder termed pancreatic acinar atrophy (PAA). Evidence of lymphocytic infiltration indicates that PAA is an autoimmune disease, but the genetic etiology remains unclear. Data from global gene expression and single nucleotide polymorphism profiles in the GSD suggest the involvement of the major histocompatibility complex [MHC; dog leukocyte antigen (DLA)]. To determine if alleles of the MHC influence development of EPI, genotyping of polymorphic class I (DLA-88) and II loci (DLA-DRB1, DLA-DQA1, and DLA-DQB1) was carried out for 70 affected and 63 control GSDs, and four-locus haplotypes were determined. One haplotype containing a novel allele of DLA-88 is very highly associated with EPI (OR > 17; P = 0.000125), while two haplotypes were found to confer protection from EPI (P = 0.00087 and 0.0115). Described herein is the genotyping of MHC class I and II loci in a GSD cohort, establishment of four-locus haplotypes, and association of alleles/haplotypes with EPI.

Association of an MHC class II haplotype with increased risk of polymyositis in Hungarian Vizsla dogs.

A breed-specific polymyositis is frequently observed in the Hungarian Vizsla. Beneficial clinical response to immunosuppressive therapies has been demonstrated which points to an immune-mediated aetiology. Canine inflammatory myopathies share clinical and histological similarities with the human immune-mediated myopathies. As MHC class II associations have been reported in the human conditions we investigated whether an MHC class II association was present in the canine myopathy seen in this breed. 212 Hungarian Vizsla pedigree dogs were stratified both on disease status and degree of relatedness to an affected dog. This generated a group of 29 cases and 183 "graded" controls: 93 unaffected dogs with a first degree affected relative, 44 unaffected dogs with a second degree affected relative, and 46 unaffected dogs with no known affected relatives. Eleven DLA class II haplotypes were identified, of which, DLA-DRB1*02001/DQA1*00401/DQB1*01303, was at significantly raised frequency in cases compared to controls (OR = 1.92, p = 0.032). When only control dogs with no family history of the disease were compared to cases, the association was further strengthened (OR = 4.08, p = 0.00011). Additionally, a single copy of the risk haplotype was sufficient to increase disease risk, with the risk substantially increasing for homozygotes. There was a trend of increasing frequency of this haplotype with degree of relatedness, indicating low disease penetrance. These findings support the hypothesis of an immune-mediated aetiology for this canine myopathy and give credibility to potentially using the Hungarian Vizsla as a genetic model for comparative studies with human myositis.

MHC class II association study in eight breeds of dog with hypoadrenocorticism.

Canine hypoadrenocorticism is an endocrine disorder characterised by inadequate secretion of steroid hormones from the adrenal glands. Pathology results from immune-mediated destruction of the adrenal cortex, which is similar to that seen in the human Addison's disease. Both the canine and human diseases have similar clinical presentation, with the diagnosis based on performing a dynamic adrenocorticotropic hormone stimulation test. MHC class II has previously been associated with the human and canine diseases. In the current study, we conducted an MHC class II association study in eight breeds of dog with diagnoses of hypoadrenocorticism. We demonstrated significant differences in dog leukocyte antigen (DLA) haplotype frequencies in six of these breeds: Cocker spaniel, Springer spaniel, Labrador, West Highland white terrier (WHWT), Bearded collie, and Standard poodle. In the Springer spaniel, the DLA-DRB1*015:01--DQA1*006:01--DQB1*023:01 haplotype was significantly associated with disease risk (p = 0.014, odds ratio (OR) = 5.14) and showed a similar trend in the Cocker spaniel. This haplotype is related to one associated with hypoadrenocorticism in the Nova Scotia duck tolling retriever. Similar haplotypes shared between breeds were demonstrated, with DLA-DRB1*001:01--DQA1*001:01--DQB1*002:01 more prevalent in both affected Labrador (p = 0.0002, OR = 3.06) and WHWT (p = 0.01, OR = 2.11). Other haplotypes that have not previously been associated with the disease were identified. The inter-breed differences in DLA haplotypes associated with susceptibility to canine hypoadrenocorticism could represent divergent aetiologies. This could have implications for clinical diagnosis and future comparative studies. Alternatively, it may suggest that the gene of interest is closely linked to the MHC.