Association between lymphocyte antigen receptor gene rearrangements and histopathological evaluation in canine chronic enteropathy

Genome-wide DNA methylation analysis in canine gastrointestinal lymphoma

DNA methylation is the covalent modification of methyl groups to DNA mostly at CpG dinucleotides and one of the most studied epigenetic mechanisms that leads to gene expression variability without affecting the DNA sequence. Genome-wide analysis of DNA methylation identified the signatures that could define subtypes of human lymphoma patients. The objective of this study was to conduct the genome-wide analysis of DNA methylation in dogs with gastrointestinal lymphoma (GIL). Genomic DNA was extracted from endoscopic biopsies from 10 dogs with GIL. We performed Digital Restriction Enzyme Assay of DNA Methylation (DREAM) for genome-wide DNA methylation analysis that could provide highly quantitative information on DNA methylation levels of CpG sites across the dog genome. We successfully obtained data of quantitative DNA methylation level for 148,601–162,364 CpG sites per GIL sample. Next, we analyzed 83,132 CpG sites to dissect the differences in DNA methylation between GIL and normal peripheral blood mononuclear cells (PBMCs). We found 383–3,054 CpG sites that were hypermethylated in GIL cases compared to PBMCs. Interestingly, 773 CpG sites including promoter regions of 61 genes were identified to be commonly hypermethylated in more than half of the cases, suggesting conserved DNA methylation patterns that are abnormal in GIL. This study revealed that there was a large number of hypermethylated sites that are common in most of canine GIL. These abnormal DNA methylation could be involved in tumorigenesis of the canine GIL.

Clinical characteristics of dogs with food-responsive protein-losing enteropathy

Background

In dogs with protein‐losing enteropathy (PLE), data on the clinical characteristics of food‐responsive PLE (FR‐PLE) remain scarce.

Objective

To determine the clinical characteristics of FR‐PLE in dogs responsive to ultralow‐fat diet (ULFD) management.

Animals

Thirty‐three dogs diagnosed with PLE based on standard diagnostic criteria.

Methods

Retrospective review of medical records. Clinical findings were compared between dogs with FR‐PLE (FR‐PLE group) and those with immunosuppressant‐responsive PLE (IR‐PLE) or nonresponsive PLE (NR‐PLE) (IR/NR‐PLE group). The area under the curve (AUC) of a receiver operating characteristic curve was used to evaluate the ability of factors to differentiate the FR‐PLE and IR/NR‐PLE groups. Survival time was compared between the FR‐PLE and IR/NR‐PLE groups.

Results

Twenty‐three dogs responded to ULFD management and were diagnosed with FR‐PLE. The canine chronic enteropathy clinical activity index (CCECAI) was significantly lower in the FR‐PLE group than in the IR/NR‐PLE group (P < .001). The AUC of CCECAI for differentiating the FR‐PLE group was 0.935 (95% confidence interval [CI], 0.845‐1.000) with an optimal cutoff value of 8 (sensitivity, 0.826; specificity, 0.889). Survival times were significantly longer in the FR‐PLE group (median, not reached) than in the IR/NR‐PLE group (median, 432 days; P < .001).

Conclusions and Clinical Importance

Dogs that respond to ULFD management and are diagnosed with FR‐PLE are expected to have a favorable prognosis. Clinical scores, specifically the CCECAI, could be useful for differentiating FR‐PLE from IR‐PLE or NR‐PLE.

Clonality testing as complementary tool in the assessment of different patient groups with canine chronic enteropathy

Differentiation between canine chronic enteropathy (CCE) and intestinal lymphoma is a diagnostic challenge as histopathology might fail to yield unequivocal results. Detection of clonal rearrangements of the T-cell-receptor gamma (TCRG) chain and IG heavy chain (IGH) V-J genes offer a useful solution. In this retrospective study, histopathology samples of 35 CCE patients and 7 healthy Beagle dogs underwent clonality testing. Patients suffered either from inflammatory bowel disease (IBD), food responsive diarrhea (FRD) or protein loosing enteropathy secondary to IBD (PLE/IBD). Healthy Beagles served as controls (CO). Canine IBD activity index (CIBDAI) and histopathological WSAVA-grading differed significantly (p<0.001) between groups. CIBDAI improved significantly after appropriate therapy (p < 0.0001). Intestinal biopsies of all CO showed polyclonal patterns for B- and T-cell primers. All samples from CCE patients showed polyclonal patterns for the B-cell primers. Targeting TCRG, 4 patients showed a monoclonal or oligoclonal pattern of the lymphocytic infiltrates in the duodenum and/or colon. Clinical improvement was observed in all dogs. Although a small cell lymphoma cannot be excluded in view of the short follow up duration, a false positive result, in the sense of a canonical rearrangement or unspecific amplification due to a antigenic stimulation in a non-neoplastic inflammatory process is possible.

Duodenal expression of antimicrobial peptides in dogs with idiopathic inflammatory bowel disease and intestinal lymphoma

Although antimicrobial peptides (AMPs) play an integral role in the regulation of intestinal microbiota and homeostasis, their expression in canine gastrointestinal diseases, including idiopathic inflammatory bowel disease (IBD) and intestinal lymphoma, remains unknown. The objective of this study was to investigate the intestinal expression of AMPs in dogs with IBD or intestinal lymphoma. IBD was diagnosed in 44 dogs, small cell intestinal lymphoma in 25 dogs, and large cell intestinal lymphoma in 19 dogs. Twenty healthy beagles were used as normal controls. Duodenal mRNA expression of six representative AMPs - lactoferrin, lysozyme, cathelicidin, secretory leukocyte peptidase inhibitor (SLPI), bactericidal/permeability increasing protein (BPI), and canine beta defensin (CBD103) - was quantified by real-time reverse transcription polymerase chain reaction. The relative expression of BPI, lactoferrin, and SLPI was significantly higher in dogs with IBD and intestinal lymphomas than in healthy controls. Interestingly, the expression patterns of AMPs differed between dogs with IBD and those with intestinal lymphomas, especially small cell lymphoma. Increased expression of BPI differentiated IBD from dogs with small cell intestinal lymphoma, with a sensitivity of 93.2%, a specificity of 100%, and an area under the curve of 0.955. These results suggest that the expression patterns of AMP aid in the diagnosis of canine IBD and intestinal lymphoma, although it remains uncertain whether the altered AMP expression is the cause or effect of mucosal inflammation.

A case of hemophagocytic syndrome progressing into large granular lymphoma in a dog

A 12-year-old castrated male mixed breed dog was presented with anorexia, lethargy, intermittent vomiting, diarrhea, and weight loss. Clinicopathologic and imaging abnormalities included pancytopenia, icterus, and splenomegaly with multiple minute hypoechogenic nodules. Bone marrow (BM) smears revealed 2.5% hemophagocytic macrophages. In addition, an increased number of small to intermediate lymphocytes (16.3%) and plasma cells (3.2%) were recognized in the BM smears. More than 80% of the lymphocytes contained multiple small intracytoplasmic magenta granules. Histopathologic findings of the spleen revealed hemophagocytosis. Large granular lymphocytes (LGLs) were not found on the liver cytology or splenic histopathology at this time. PCR for antigen receptor rearrangement (PARR) analysis showed a clonal reaction in the T-cell receptor ɤ (TCRɤ) gene in the BM sample. The dog was diagnosed with hemophagocytic syndrome (HPS). The dog was maintained in good condition with immunosuppressive therapy. However, the dog developed hepatic LGL lymphoma 7 months later. At this time, PARR analysis showed a clonal TCRɤ gene rearrangement in the hepatic LGL lymphoma samples. The BM and liver sample clonal rearrangements showed 100% homology, indicating that the small to intermediate granular lymphocytes in the BM at the HPS stage had progressed to hepatic LGL lymphoma. To our knowledge, this is the first report of canine secondary HPS caused by the occurrence of a BM LGL lymphoma clone that progressed to hepatic LGL lymphoma.

Immunohistochemical Profiling of Canine Intestinal T-Cell Lymphomas

Human enteropathy-associated T-cell lymphoma (EATL) is classified into 2 distinct subgroups based on their phenotypes (type I and type II). Canine intestinal T-cell lymphoma can be morphologically classified into large and small cell lymphomas (LCL and SCL, respectively). Their association with human EATL or immunohistochemical and biological features has not been well characterized. In this study, the immunohistochemical profiles of 17 cases of LCL and 33 cases of SCL were evaluated with markers used for human EATL classification. Morphologically, LCL was characterized by sheet-like proliferation of large to moderately sized neoplastic lymphocytes, with scant clear cytoplasm and pleomorphic, irregularly shaped nuclei containing distinctive nucleoli and scattered chromatin. In contrast, SCL was characterized by the proliferation of monomorphic small neoplastic lymphocytes, accompanied by infiltration of nonneoplastic plasma cells. Interestingly, 8 cases demonstrated mixed LCL and SCL morphologies. Granular cytoplasmic expression of granzyme B was observed in most LCL and SCL cases. Membranous expression of CD56 was demonstrated in only 2 of 17 LCL and 0 of 33 SCL cases. Coexpression of CD20 by neoplastic T cells was observed in more SCL cases (16/33; 48%) than LCL cases (1/17; 6%). The CD56-positive cells in 2 cases were negative for CD20. Although canine LCL shares common features with human EATL type I, canine SCL cells and human EATL type II differ in their immunophenotype. Canine intestinal T-cell lymphoma had a homogeneous immunophenotype regardless of cell morphology. The findings of this study may indicate large cell transformation of SCL rather than 2 distinct entities.

Fecal microbiome in dogs with inflammatory bowel disease and intestinal lymphoma

Although alteration of commensal microbiota is associated with chronic gastrointestinal (GI) diseases such as inflammatory bowel disease (IBD) in dogs, the microbiota composition in intestinal lymphoma, an important differential diagnosis of canine IBD, has not been investigated. The objective of this study was to compare the fecal microbiota in dogs with IBD, dogs with intestinal lymphoma, and healthy dogs. Eight dogs with IBD, eight dogs with intestinal lymphoma, and fifteen healthy dogs were included in the study. Fecal samples were analyzed by 16S rRNA gene next-generation sequencing. Rarefaction analysis failed to reveal any difference in bacterial diversity among healthy dogs and diseased dogs. Based on PCoA plots of unweighted UniFrac distances, the bacterial composition in dogs with intestinal lymphoma was different from those observed in dogs with IBD and healthy dogs. When compared with healthy dogs, intestinal lymphoma subjects showed significant increases in organisms belonging to the Eubacteriaceae family. The proportion of the family Paraprevotellaceae and the genus Porphyromonas was significantly higher in dogs with IBD compared to healthy dogs. These observations suggest that dysbiosis is associated with intestinal lymphoma as well as IBD in dogs.

Significance of clonal rearrangements of lymphocyte antigen receptor genes on the prognosis of chronic enteropathy in 22 Shiba dogs

Shiba dogs are predisposed to chronic enteropathy (CE) and have poorer prognosis than other dog breeds. The objective of this study was to investigate the significance of polymerase chain reaction for antigen receptor rearrangement (PARR) results on clinical findings and prognosis of Shiba dogs with CE. We retrospectively collected data on 22 Shiba dogs diagnosed as having CE. Fifty-nine percent of the dogs had clonality-positive results on PARR analysis. Furthermore, on histopathology, epitheliotropic behavior of small lymphocytes of the intestinal mucosa was observed significantly more frequently in dogs with clonal rearrangement of antigen receptor genes (P=0.027). The median overall survival time of clonality-positive dogs was 48 days (range, 4–239 days), compared to 271 days (range, 45–1,316+ days) in clonality-negative dogs. The median overall survival time of epitheliotropism-positive dogs was 76 days (range, 30–349 days) compared to 239 days (range, 4–1,316+ days) for epitheliotropism-negative dogs. Statistical analysis revealed that the clonality-positive result was associated with significantly shorter survival time (P=0.036). In contrast, presence or absence of epitheliotropism had no statistically significant effect on survival time (P=0.223). These cases might appropriately be diagnosed as small T-cell intestinal lymphoma; there are some common clinical and pathogenic features with human enteropathy-associated T-cell lymphoma type 2. The pathogenesis and poor prognosis for Shiba dogs with CE seem to be associated with this type of lymphoma, although further investigation is warranted.

Endoscopic Cytology for the Diagnosis of Chronic Enteritis and Intestinal Lymphoma in Dogs

Although cytology is a rapid diagnostic procedure in dogs, the cytologic criteria of endoscopic biopsies for chronic enteritis and intestinal lymphoma are not well defined. An immediate diagnosis using cytology would benefit patients by enabling prompt initiation of therapy. The objective of this study was to investigate the correlation between the results of endoscopic cytology and histopathology. In this study, 167 dogs with clinical signs of chronic gastrointestinal disease were included. On the basis of histopathology, the following diagnoses were determined: lymphocytic-plasmacytic enteritis in 93 dogs; eosinophilic enteritis in 5 dogs; small cell intestinal lymphoma in 45 dogs; and large cell intestinal lymphoma in 24 dogs. Two clinical pathologists retrospectively evaluated the endoscopic cytology of squash-smear preparations. The cytologic diagnoses of inflammation, small cell lymphoma, and large cell lymphoma were based on the severity of lymphocyte infiltration, the size of infiltrated lymphocytes, and eosinophil/mast cell infiltration. The clinical severity score was significantly increased along with the degree of lymphocyte infiltration evaluated by cytology. The cytologic diagnosis was in complete agreement with the histopathologic diagnosis in 136 of 167 (81.4%) cases. For the differentiation between enteritis and lymphoma, endoscopic cytology had a sensitivity of 98.6%, a specificity of 73.5%, a positive predictive value of 72.3%, and a negative predictive value of 98.6%. The log-rank test and Cox regression analysis showed that the results of cytology predicted the prognosis. These results suggest that endoscopic cytology is a useful technique to aid diagnosis of intestinal inflammation and lymphoma in dogs.

IgA Antibodies Against Gliadin and Tissue Transglutaminase in Dogs With Chronic Enteritis and Intestinal T-Cell Lymphoma

Molecular clonality analysis of T-cell receptor (TCR) genes for diagnosing T-cell lymphoma is widely used in veterinary medicine. However, differentiating chronic enteritis (CE) from intestinal lymphoma is challenging because of the incompatibility between histopathologic and clonality analysis results. On the basis of findings that canine intestinal T-cell lymphoma and celiac disease share some common features, we conducted serologic examinations in combination with histopathologic and T-cell receptor clonality analyses in 48 dogs diagnosed with either CE or intestinal lymphoma. Immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies against gliadin and tissue transglutaminase (tTG) were quantitatively measured using ELISA. The conditions were classified according to the histopathologic diagnosis, clonality analysis, and combined histopathologic/clonality analysis. Histopathologic analysis showed that dogs with intestinal lymphoma were likely to have high levels of serum IgA antibodies against gliadin and tTG, and serum IgG antibodies against tTG. No correlation between the diagnosed groups and control group was observed in the results of the clonality analysis and histopathologic/clonality analysis. It is interesting that dogs with intestinal lymphoma had a higher serum IgA titer against gliadin and tTG than did dogs with CE. These results suggest an association between repetitive inflammatory stimulation by gliadin peptides and subsequent intestinal lymphoma in dogs.