Non-tuberculous Mycobacteria can Cause Disseminated Mycobacteriosis in Cats.

Mycobacteriosis caused by non-tuberculous mycobacteria (NTM) is a rising concern in human medicine both in immunocompromised and immunocompetent patients. In cats, mycobacteriosis caused by NTM is considered mostly to be a focal or dermal infection, with disseminated disease mostly caused by Mycobacterium avium. We describe three cases of disseminated mycobacteriosis in cats, caused by Mycobacterium malmoense, Mycobacterium branderi/shimoidei and M. avium, with no identified underlying immunosuppression. In all cases, extracellular mycobacteria were seen in the pulmonary epithelium, intestinal lumen and glomerular tufts, which could affect the shedding of the organism. The present study highlights the importance of mycobacteriosis as a differential even in immunocompetent animals. Considering the close relationship of owners and pets and the potential presence of free mycobacteria in secretions, cats should be considered as a possible environmental reservoir for mycobacteria.

Identification of Glyceraldehyde-3-Phosphate and Alcohol Dehydrogenases as Autoantigens in Doberman Hepatitis.

An autoimmune background is suspected for Doberman hepatitis (DH). It is based on the finding of mononuclear cell infiltrates in the liver, strong female bias, association to the homozygous risk factor dog leucocyte antigen (DLA) allele DRB1*00601 and aberrant major histocompatibility complex (MHC) class II expression on hepatocytes that correlates with the degree of inflammation in the liver. The aim of this study was to search for autoantibodies against liver-related antigens associated with DH. Twenty-five Dobermans with subclinical DH (SDH), 13 that clinically manifest DH (CDH) and 17 healthy controls were studied. Immunoblotting analysis detected specific antibodies in the DH sera. By mass spectrometry the targets were identified as liver-related enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and alcohol dehydrogenase (ADH). Using ELISA, anti-GAPDH IgG was detected in 36% (9/25) of SDH dogs and 69.2% (9/13) of the CDH dogs compared to healthy controls (0/17) (P < 0.0005). Anti-ADH IgG was detected in 72% (18/25) of SDH dogs and 76.9% (10/13) of CDH dogs and only in one (1/17) control (P < 0.0005). The finding of novel autoantigens, GAPDH and ADH strengthen the hypothesis that DH is an autoimmune disease of the liver. These findings suggest that DH could be diagnosed by screening for autoantibodies against the defined antigens.

Antihistone Autoantibodies in Dobermans With Hepatitis.

BACKGROUND: Immune system involvement is suggested as an underlying cause for Doberman hepatitis (DH) based on female predisposition, lymphocyte infiltration, abnormal hepatocyte expression of major histocompatibility complex class II antigens, and homozygosity for dog leukocyte antigen DRB1*00601. OBJECTIVE: To measure serum antinuclear antibodies (ANA) and serum antihistone antibodies (AHA) in Dobermans with hepatitis. To determine whether increased serum ANA or serum AHA could be used to support the diagnosis of Doberman hepatitis (DH). ANIMALS: Privately owned 25 subclinically and 13 clinically affected DH Dobermans and 17 healthy control Dobermans. METHODS: Case-control study. Indirect immunofluorescence (IIF) microscopy and line blot tests were employed for the ANA pilot studies and an enzyme-linked immunosorbent assay (ELISA) assay for detection of IgG AHA. RESULTS: Indirect immunofluorescence revealed ANA-positive cases, and line blot showed AHA reactivity. In ELISA, importantly increased concentrations of AHA were found in 92% (23/25) of dogs in the subclinical stage and 84.6% (11 of 13) of dogs in the clinical stage of DH compared with no control dogs (0/17) (P < 0.0005). The mean AHA absorbance values of the blood samples obtained from the 25 subclinical DH dogs (1.36 ± 0.60, mean ± SD) and the 13 clinically affected dogs (1.46 ± 0.49) were significantly higher than in 17 control dogs (0.51 ± 0.18; P < 0.0001). CONCLUSIONS AND CLINICAL IMPORTANCE: As the presence of AHA indicates autoimmune activity, our results favor an autoimmune background as one cause for DH. Antihistone antibody could represent a novel means for screening Dobermans with increased serum alanine transaminase concentrations and suspicion of DH.

Evaluation of DLA promoters in Doberman hepatitis.

Doberman hepatitis (DH) is associated with homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 indicating a role for the immune system in the development of the disease. The dog leucocyte antigen (DLA) class II expression is controlled at the transcriptional level with proximal promoters. Differential expression of DLA class II molecules of antigen-presenting cells is reported to affect susceptibility to or protection from different immune-mediated diseases. The aim of this study was to evaluate, whether the variation in promoter areas of homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 Dobermans could explain why some dogs become afflicted with DH and others do not. Our findings suggest that promoter variants are not associated as risk modifiers in homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 Dobermans, but additional factors are needed. Nevertheless, our study indicates that the whole DLA block is associated to the disease.

Association of Doberman hepatitis to canine major histocompatibility complex II.

Doberman hepatitis (DH) is a chronic and progressive inflammatory liver disease that mainly affects female dogs. The high incidence of chronic hepatitis in Dobermans is suggestive of a genetic predisposition. DH is characterized by mononuclear cell infiltration and copper accumulation in the liver and major histocompatibility complex (MHC) class II antigen expression in the hepatocytes. In dogs, the MHC is referred to as the dog leukocyte antigen (DLA) system. In this study, the potential role of DLA genes in DH was investigated by sequence-based typing in the exon 2 of DLA-DRB1, -DQA1 and -DQB1. The case group comprised 37 Dobermans with subclinical or clinical DH. The control group consisted of 37 healthy Dobermans, with normal liver enzyme values and without immunosuppressive medication. The control dogs were over 10 years old to include dogs with the lowest genetic risk of DH. Our results indicate that Dobermans with homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 [odds ratio (OR) = 14.9, confidence limit (CL) = 3.1-71.7, P < 0.00005], especially with homozygosity for DLA-DRB1*00601 (P < 0.0005), are susceptible to DH. The DQ heterodimer DLA-DQA1*00901/DQB1*00101 and the allele DLA-DRB1*01501 appear to confer protection against DH (P < 0.001). Allele and haplotype frequencies were compared using chi-squared statistics. The disease shows a complex pattern of inheritance, but the observed DLA class II association with DH suggests a role for the immune system in the development of the disease.

Upregulation of major histocompatibility complex class II antigens in hepatocytes in Doberman hepatitis.

Major histocompatibility complex (MHC) class II antigen expression in hepatocytes and its correlation with mononuclear cell infiltration into the liver were studied using immunohistochemical techniques in 38 Dobermans with Doberman hepatitis (DH). Liver biopsy samples were obtained from 18 dogs at the subclinical stage. Autopsy samples were taken from 6 DH dogs euthanized for a reason other than DH, from 14 dogs euthanized because of advanced liver failure and from 6 control Dobermans. Upon examination of the control liver samples, no expression of MHC class II antigens was detected in hepatocytes. By contrast, in 15 of the 18 DH biopsies (83%) and in all 20 DH autopsy liver samples, hepatocytes expressed MHC class II molecules. MHC class II expression was either cytoplasmic or membranous and occurred in conjunction with lymphocyte infiltration. A correlation between the inflammatory reaction and the expression of MHC class II in hepatocytes suggests that the aberrant expression of MHC class II in hepatocytes is induced by cytokines. Hepatocytes presenting a putative MHC class II molecule-associated autoantigen could thus become the target of an immune attack mediated by CD4+ T cells. In addition, corticosteroid treatment was observed to significantly decrease MHC class II expression in DH hepatocytes. Inappropriate MHC class II expression in hepatocytes and mononuclear cell infiltration are suggesting an autoimmune nature for chronic hepatitis in Dobermans.

Lesions of subclinical doberman hepatitis.

This investigation describes histologic lesions in the livers of 18 Doberman Pinschers suffering from subclinical doberman hepatitis (DH). The dogs' ages ranged from 2.5 to 7 years; 15 were females and 3 were males. At the time of liver biopsy, the dogs had no clinical signs of liver disease, although serum alanine aminotransferase (ALT) values had been elevated in two samples in successive months. In the histologic examination, all biopsies revealed parenchymal and portal mononuclear inflammation. In the parenchyma, the inflammation was diffuse, with multifocal clusters of inflammatory cells. The periportal reaction was usually mild to moderate. Bridging necrosis (3/18) and bile duct proliferation (2/18) were rare. Excessive copper was detected by rubeinic acid stain in every specimen. Postmortem liver samples were obtained from nine dogs 3.5-65 months after the initial biopsy specimen; five of these dogs had been euthanatized for reasons other than DH, and liver specimens revealed piecemeal necrosis (5/5), bridging necrosis (3/5), and bile duct proliferation (2/5). Four of them had been euthanatized because of DH. Liver lesions of these dogs were typical for chronic active hepatitis, with bridging and piecemeal necrosis (4/4), portal expansion (4/4), bile duct proliferation (4/4), and fibrosis (4/4). A scoring system was used to evaluate changes numerically from biopsy to postmortem samples. Lesions in all dogs had progressed. The most important histologic changes were expansion of portal areas (P = 0.008), increased periportal and bridging necrosis (P = 0.008), increased fibrosis (P = 0.016), and proliferation of the bile ducts (P = 0.063).

Subclinical versus clinical hepatitis in the dobermann: evaluation of changes in blood parameters.

Concentrations of the enzymes alanine aminotransferase (ALT) and alkaline phosphatase (AP) were determined in blood samples from 626 randomly selected clinically healthy dobermann. ALT levels greater than three times the normal upper value were detected in 55 dogs. These dogs were selected for further investigation; the owners of 23 of the dogs allowed a liver biopsy to be performed. Histopathological examination revealed various degrees of hepatitis and excessive amounts of copper in 21 of the dogs. These cases, referred to as subclinical dobermann hepatitis (DH), were selected for a follow-up investigation in which the clinical signs and serum parameters (ALT, AP and bilirubin) were studied for a period of three to 48 months. Serum parameters of those with subclinical DH were compared with blood samples collected from 22 dogs with clinical DH. Individual dogs showed great variation in the levels of ALT and AP between consecutive serum samples. These enzyme levels never, however, fell to the normal range. During the subclinical stage no statistically significant (P > 0.05) change occurred in the concentrations of ALT or AP. When dogs with subclinical DH were compared with dogs with clinical DH, there was no statistically significant (P > 0.05) difference in ALT levels, whereas AP concentrations were significantly (P < 0.001) higher among clinically affected dogs. Elevated levels of bilirubin were detected almost exclusively in dogs with clinical DH. After the onset of clinical signs there was a decrease in the ALT levels and an increase in AP concentrations as the disease progressed, but the changes were not statistically significant (P > 0.05).