Doberman hepatitis (DH) is a rare and chronic inflammatory condition of the liver. The early diagnosis of DH is difficult, and Dobermans may be affected for months or years before the diagnosis. There is no curative treatment and the prognosis is poor if the condition is associated with clinical signs of liver failure. Unraveling the disease etiologyand pathogenesis would enhance the diagnostic approaches, and novel therapies could improve the prognosis for Dobermans. Our studies aimed to identify supporting evidence for the suspected autoimmune background of DH by satisfying more descriptive characteristic risk factors that are described in human autoimmune diseases. We focused on major histocompatibility complex (MHC) class II genes, MHC class II regulatory regions, circulating serum anti-nuclear antibodies (ANA), and possible liver-related autoantigens associated with DH. We identified a homozygous dog leukocyte antigen (DLA) risk haplotype and allele for DH. DLA-DRB1*00601/DQA1*00401/DQB1*01303 haplotype elevated the risk of DH susceptibility close to 15-fold. A homozygous risk DLA-DRB1*00601 allele was found in all DH dogs, while this allele was present in 56.8% of the healthy controls. DLA-DQA1*00901/DQB1*00101 and allele DLA-DRB1*01501 appear to protect against DH development. Overall, the DLA region showed very low variation among DH patients, with only two different haplotype combinations compared with seven in the control group. We defined the level of variation of the regulatory promoters in DH patients and controls with the homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 haplotype. Also, the potential polymorphism in the DLA-DRAp promoter and DLA-DRA exon 2 was examined. The promoter DLA-DRAp and exon 2 were identical to the dog reference sequences in both groups. The promoters DRBp, DQAp, and DQBp were monomorphic, with no explaining variation when comparing DH patients with healthy control Dobermans. DLA-DRB1*00601 allele was associated with DRBp*1, DLADQB1*01303 allele with DQBp*6, and DLA-DQA1*00401 allele with DQAp*2. Our result suggests that promoter variants are not associated as risk modifiers for DH in Dobermans with the risk haplotype, but the whole DLA block is associated with DH. The study revealed ANA in DH patients. ANA were further characterized as antihistone autoantibodies (AHA) that were significantly elevated in DH. Thus, immune tolerance has failed in DH. Our results suggest that elevated AHA in conjunction with high alanine aminotransferase (ALT) in a Doberman with or without clinical signs of hepatitis support the DH diagnosis. A negative serum AHA result does not rule out DH, and AHA is not a suitable biomarker for disease progression. We described two novel liver-related target autoantigens in DH. These could be identified as dehydrogenase enzymes, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and alcohol dehydrogenase (ADH). DH dogs had significantly elevated serum IgG immunoreactivity towards GAPDH and ADH antigens compared with controls, and the disease was associated with both autoantibodies. This provides evidence for an antigen-driven autoimmune process and elucidates the previously unknown DH pathogenesis. This thesis provides new insights into the suspected autoimmune etiology and pathogenesis of DH. We conclude that the study contributes to the development of useful biomarkers that could be used to improve the currently difficult early diagnosis of DH in Dobermans with elevated ALT levels. Our findings support the theory that DH has an autoimmune origin.
|Award date||1 Dec 2017|
|Place of Publication||Helsinki|
|Publication status||Published - 1 Dec 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
Fields of Science
- 413 Veterinary science