An immunohistochemical study of histiocytic ulcerative colitis in boxer dogs

Repeat histopathology and culture of colonic biopsy specimens after treatment for Escherichia coli-associated granulomatous colitis in a cat

Case summary

A 7.5-year-old neutered male Oriental Shorthair cat presented with an 8-month history of haematochezia, mucoid diarrhoea, tenesmus and vocalisation after a 4-year history of small bowel diarrhoea. Transabdominal ultrasonography confirmed diffuse colonic wall thickening and extensive ulceration and erythema after colonoscopy. Colonic histopathology confirmed periodic acid-Schiff positive macrophages, consistent with granulomatous colitis; Escherichia coli was cultured from colonic biopsy specimens. Fluorescent in situ hybridisation (FISH) identified intracellular E coli, and an 8-week oral course of marbofloxacin, a hydrolysed protein diet and a 5-day course of fenbendazole yielded a transient partial clinical remission of the colitis signs. A reported resolution in the small bowel signs was also reported. Colonoscopy was repeated 5 months later due to the recurrence of colitis signs. Histopathology was not consistent with granulomatous colitis supporting a complete remission; however, a chronic inflammatory enteropathy was confirmed with moderate lymphoplasmacytic, neutrophilic and eosinophilic colitis without a histiocytic component. E coli was again cultured from colonic biopsies with sensitivity to fluoroquinolones; FISH was positive for intracellular E coli. Clinical signs persisted despite a 2-week course of oral marbofloxacin.

Relevance and novel information

E coli-associated granulomatous colitis is rare in cats. Colonic biopsy specimen culture is important to guide appropriate antibiotic therapy. Repeat histopathology, culture and FISH have not been previously reported after treatment of a cat with E coli-associated granulomatous colitis. Persistent clinical signs after treatment with oral marbofloxacin alongside a confirmed complete histologic remission support the presence of a concurrent chronic inflammatory enteropathy and pathology for the cat's ongoing colitis.

Changes of Enterocyte Morphology and Enterocyte: Goblet Cell Ratios in Dogs with Protein-Losing and Non-Protein-Losing Chronic Enteropathies

This study aimed to assess the morphometry of enterocytes as well as the goblet cell-to-enterocyte ratio in different intestinal segments of dogs with chronic enteropathies (CE). Histopathological intestinal samples from 97 dogs were included in the study (19 healthy juveniles, 21 healthy adults, 24 dogs with protein-losing enteropathy (PLE), and 33 CE dogs without PLE). Healthy adult small intestinal enterocytes showed progressively reduced epithelial cell height in the aboral direction, while juvenile dogs showed progressively increased epithelial cell height in the aboral direction. CE dogs had increased epithelial cell height in the duodenum, while PLE dogs had decreased epithelial cell heights compared to healthy adult dogs. Both the CE and PLE dogs showed decreased enterocyte width in the duodenal segment, and the ileal and colonic enterocytes of CE dogs were narrower than those of healthy adult dogs. CE dogs had a lower goblet cell-to-enterocyte ratio in the colon segment compared to healthy dogs. This study provides valuable morphometric information on enterocytes during canine chronic enteropathies, highlighting significant morphological enterocyte alterations, particularly in the small intestine, as well as a reduced goblet cell-to-enterocyte ratio in the colon of CE cases compared to healthy adult dogs.

Intestinal S100/Calgranulin Expression in Cats with Chronic Inflammatory Enteropathy and Intestinal Lymphoma

Simple Summary

Intestinal diseases in cats are complicated diseases in which intestinal inflammation is difficult to distinguish from lymphoma, which is a neoplasm. In this study, the expression of the proteins S100A8/A9 and S100A12 (also called calgranulins) in the intestine is investigated in both diseases and for potential correlations with microscopically visible changes in the intestine or the clinical severity of the disease. Only small differences were seen between healthy and diseased animals, and there were no differences between cats with intestinal inflammation and lymphoma. However, several correlations of cells staining positive for calgranulins and inflammatory changes at the microscopic level and clinical disease severity were shown. This indicates that calgranulins play a role in both gastrointestinal lymphoma and inflammation and would support the recent theory that these two diseases might not be separate disease entities but instead are related. Further insights into the role of the calgranulins in these feline diseases will lead to a better understanding of the disease pathogenesis and, thus, potentially novel diagnostics and treatment avenues.

Abstract

Diagnosing chronic inflammatory enteropathies (CIE) in cats and differentiation from intestinal lymphoma (IL) using currently available diagnostics is challenging. Intestinally expressed S100/calgranulins, measured in fecal samples, appear to be useful non-invasive biomarkers for canine CIE but have not been evaluated in cats. We hypothesized S100/calgranulins to play a role in the pathogenesis of feline chronic enteropathies (FCE) and to correlate with clinical and/or histologic disease severity. This retrospective case-control study included patient data and gastrointestinal (GI) tissues from 16 cats with CIE, 8 cats with IL, and 16 controls with no clinical signs of GI disease. GI tissue biopsies were immunohistochemically stained using polyclonal α-S100A8/A9 and α-S100A12 antibodies. S100A8/A9⁺ and S100A12⁺ cells were detected in all GI segments, with few significant differences between CIE, IL, and controls and no difference between diseased groups. Segmental inflammatory lesions were moderately to strongly correlated with increased S100/calgranulin-positive cell counts. Clinical disease severity correlated with S100A12⁺ cell counts in cats with IL (ρ = 0.69, p = 0.042) and more severe diarrhea with colonic lamina propria S100A12⁺ cells with CIE (ρ = 0.78, p = 0.021) and duodenal S100A8/A9⁺ cells with IL (ρ = 0.71, p = 0.032). These findings suggest a role of the S100/calgranulins in the pathogenesis of the spectrum of FCE, including CIE and IL.

Elucidating the Role of Innate and Adaptive Immune Responses in the Pathogenesis of Canine Chronic Inflammatory Enteropathy-A Search for Potential Biomarkers

Simple Summary

Canine chronic inflammatory enteropathy (CIE) is a chronic disease affecting the small or large intestine and, in some cases, the stomach of dogs. This gastrointestinal disorder is common and is characterized by recurrent vomiting, diarrhea, and weight loss in affected dogs. The pathogenesis of IBD is not completely understood. Similar to human IBD, potential disease factors include genetics, environmental exposures, and dysregulation of the microbiota and the immune response. Some important components of the innate and adaptive immune response involved in CIE pathogenesis have been described. However, the immunopathogenesis of the disease has not been fully elucidated. In this review, we summarized the literature associated with the different cell types and molecules involved in the immunopathogenesis of CIE, with the aim of advancing the search for biomarkers with possible diagnostic, prognostic, or therapeutic utility.

Abstract

Canine chronic inflammatory enteropathy (CIE) is one of the most common chronic gastrointestinal diseases affecting dogs worldwide. Genetic and environmental factors, as well as intestinal microbiota and dysregulated host immune responses, participate in this multifactorial disease. Despite advances explaining the immunological and molecular mechanisms involved in CIE development, the exact pathogenesis is still unknown. This review compiles the latest reports and advances that describe the main molecular and cellular mechanisms of both the innate and adaptive immune responses involved in canine CIE pathogenesis. Future studies should focus research on the characterization of the immunopathogenesis of canine CIE in order to advance the establishment of biomarkers and molecular targets of diagnostic, prognostic, or therapeutic utility.

Harnessing the Biology of Canine Intestinal Organoids to Heighten Understanding of Inflammatory Bowel Disease Pathogenesis and Accelerate Drug Discovery: A One Health Approach

In a recent issue of the Lancet, the prevalence of Inflammatory Bowel Disease (IBD) was estimated at 7 million worldwide. Overall, the burden of IBD is rising globally, with direct and indirect healthcare costs ranging between $14.6 and $31.6 billion in the U.S. alone in 2014. There is currently no cure for IBD, and up to 40% of patients do not respond to medical therapy. Although the exact determinants of the disease pathophysiology remain unknown, the prevailing hypothesis involves complex interplay among host genetics, the intestinal microenvironment (primarily bacteria and dietary constituents), and the mucosal immune system. Importantly, multiple chronic diseases leading to high morbidity and mortality in modern western societies, including type II diabetes, IBD and colorectal cancer, have epidemiologically been linked to the consumption of high-calorie, low-fiber, high monosaccharide, and high-fat diets (HFD). More specifically, data from our laboratory and others have shown that repeated consumption of HFD triggers dysbiotic changes of the gut microbiome concomitant with a state of chronic intestinal inflammation and increased intestinal permeability. However, progress in our understanding of the effect of dietary interventions on IBD pathogenesis has been hampered by a lack of relevant animal models. Additionally, current in vitro cell culture systems are unable to emulate the in vivo interplay between the gut microbiome and the intestinal epithelium in a realistic and translatable way. There remains, therefore, a critical need to develop translatable in vitro and in vivo models that faithfully recapitulate human gut-specific physiological functions to facilitate detailed mechanistic studies on the impact of dietary interventions on gut homeostasis. While the study of murine models has been pivotal in advancing genetic and cellular discoveries, these animal systems often lack key clinical signs and temporal pathological changes representative of IBD. Specifically, some limitations of the mouse model are associated with the use of genetic knockouts to induce immune deficiency and disease. This is vastly different from the natural course of IBD developing in immunologically competent hosts, as is the case in humans and dogs. Noteworthily, abundant literature suggests that canine and human IBD share common clinical and molecular features, such that preclinical studies in dogs with naturally occurring IBD present an opportunity to further our understanding on disease pathogenesis and streamline the development of new therapeutic strategies. Using a stepwise approach, in vitro mechanistic studies investigating the contribution of dietary interventions to chronic intestinal inflammation and "gut leakiness" could be performed in intestinal organoids and organoid derived monolayers. The biologic potential of organoids stems from the method's ability to harness hard-wired cellular programming such that the complexity of the disease background can be reflected more accurately. Likewise, the effect of therapeutic drug candidates could be evaluated in organoids prior to longitudinal studies in dog and human patients with IBD. In this review, we will discuss the value (and limitations) of intestinal organoids derived from a spontaneous animal disease model of IBD (i.e., the dog), and how it can heighten understanding of the interplay between dietary interventions, the gut microbiota and intestinal inflammation. We will also review how intestinal organoids could be used to streamline the preclinical development of therapeutic drug candidates for IBD patients and their best four-legged friends.

Correlation of cytology to histology in a case of canine granulomatous colitis in a Boxer dog

A 2-year-old castrated male mixed breed dog presented to the North Carolina State Veterinary Teaching Hospital for chronic diarrhea with hematochezia and weight loss. Cytology performed on a rectal scraping revealed macrophages containing magenta, light pink, and variably blue granular inclusions, and phagocytosed material concerning for infectious organisms. Histopathology was consistent with granulomatous colitis and identified intra-histiocytic bacterial organisms, confirmed by fluorescent in situ hybridization (FISH)-tissue culture-confirmed Escherichia coli. Based on these findings, a diagnosis of granulomatous colitis was made. The patient was successfully treated with oral enrofloxacin, and near-complete remission of signs was achieved within 6 weeks. This report describes a case of granulomatous colitis in a mixed breed dog, and is the first published description of the cytologic features of this uncommon disease, offering a valuable cytologic-histologic correlation. In this case, the cytology was helpful in identifying features consistent with granulomatous colitis and prioritizing the differential diagnoses and diagnostic plan.

Upregulation of signal transducer and activator of transcription 3 in dogs with chronic inflammatory enteropathies

Background

In inflammatory bowel disease (IBD) in humans, phosphorylated signal transducer and activator of transcription 3 (pSTAT3) is upregulated in mucosal epithelial cells and correlates with clinical severity.

Hypothesis/Objective

To investigate the expression pattern of pSTAT3 in the mucosa of dogs with chronic inflammatory enteropathy (CIE) and explore correlations between its expression and clinical and histopathological severity scoring.

Animals

Twenty‐eight canine CIE patients grouped into food‐responsive enteropathy (FRE;  9), steroid‐responsive enteropathy (SRE;  10), and protein‐losing enteropathy (PLE;  9). Ten healthy beagle dogs served as controls (CO).

Methods

Retrospective case control study. Immunohistochemistry was used to detect pSTAT3 in canine duodenal mucosa samples.

Results

Compared to CO, SRE (P < .001) and PLE (P < .001) dogs had significantly higher pSTAT3 expression in the villus epithelium. The SRE group had a significantly higher expression in the villus lamina propria (VLP) compared to controls (P = .009). In the crypt epithelium (CE), all CIE dogs had significantly higher pSTAT3 expression (FRE, P = .002; SRE, P = .003; PLE, P < .001) compared to CO. In the lamina propria crypt region (CLP), dogs with FRE (P = .04) and SRE (P = .03) had significantly upregulated pSTAT3 compared to controls. A positive correlation was found between canine chronic enteropathy clinical activity index (CCECAI) scoring and pSTAT3 expression for both epithelial (rho = .541; P < .001) and crypt regions (rho = .32; P = .02).

Conclusions and Clinical Importance

pSTAT3 is upregulated in CIE in dogs, correlates with clinical severity, and may be helpful as a clinical marker in dogs with CIE.

Clinical characteristics and long-term outcome of E. coli-associated granulomatous ileocolitis in dogs: five cases (2010-2014)

OBJECTIVES

To describe the clinical characteristics and long-term outcome of Escherichia coli-associated granulomatous ileocolitis in dogs.

METHODS

Retrospective review of medical records from dogs with periodic acid-Schiff positive (PAS+) granulomatous ileocolitis and mucosally invasive E. coli in the ileum and colon. Initial bacterial colonisation was evaluated using fluorescence in situ hybridization (FISH) in all dogs and corroborated with colonic and/or ileal culture, when performed.

RESULTS

Four boxer dogs and 1 French Bulldog with PAS+ granulomatous ileocolitis (GIC) were evaluated. All dogs had chronic diarrhoea refractory to empirical therapy. Ileocolonoscopy revealed mucosal haemorrhage and ulceration in the ileum (3/4) and colon (5/5). E. coli were visualised as clusters within the ileal and colonic mucosa. Complete (CR, 4/5) or partial (PR, 1/5) clinical response to fluoroquinolones was noted in all dogs within 30 days. CR was sustained in three of four dogs (median disease-free interval 40 months, range 16 to 60). Two dogs relapsed while receiving fluoroquinolones. Repeat biopsy isolated multidrug-resistant, mucosally invasive E. coli in the ileum (1/2) and colon (2/2). Targeted antimicrobial therapy was associated with long-term PR (78 months) in both dogs.

CLINICAL SIGNIFICANCE

Concurrent E. coli-associated granulomatous inflammation in the ileum and colon did not impart a poor clinical outcome or lack of response to the conventional standard of care for granulomatous colitis in dogs that were aggressively diagnosed and treated. Clinical outcome was influenced by antimicrobial resistance, with response dependent upon antimicrobial therapy informed by susceptibility testing.

Chronic Inflammatory Disease in the Pancreas, Kidney and Salivary Glands of English Cocker Spaniels and Dogs of Other Breeds Shows Similar Histological Features to Human IgG4-related Disease

Chronic pancreatitis (CP) is a common disease in the English cocker spaniel (ECS) and is characterized histologically by duct destruction, interlobular fibrosis and dense periductular and perivenous lymphocytic aggregates. These features are also found in human autoimmune pancreatitis type 1, part of a glucocorticoid-responsive, multiorgan syndrome, newly recognized as IgG4-related disease (IgG4-RD). Human IgG4-RD affects one or several organs, often showing a predominance of IgG4⁺ plasma cells histologically, with an IgG4⁺:total IgG⁺ plasma cell ratio of >40%. This study investigated whether ECSs with CP and/or inflammatory disease in several organs show an increase in IgG4⁺ plasma cells within affected tissues. Histological sections of pancreas, liver, kidney, salivary gland and conjunctiva were obtained from ECSs with idiopathic chronic inflammatory disease affecting those tissues. Tissue samples from age-matched dogs of other breeds with similar diseases were also sampled. Control diseased tissue samples, from dogs without a suspected immune-mediated disease, were included. A subset of ECSs and dogs of other breeds presented with disease in more than one organ. Immunohistochemistry was performed with primary reagents detecting total IgG and three of the four canine IgG subclasses (IgG2, IgG3 and IgG4). Normal sections of pancreas and liver showed an absence of labelled plasma cells of any subclass. Normal kidney and salivary gland sections showed the presence of a few labelled plasma cells (<10 plasma cells/high-power field). Fourteen tissue sections from 12 ECSs and seven sections from six dogs of other breeds showed elevated numbers of IgG4⁺ plasma cells and IgG4⁺:IgG⁺ ratios >40%. Individual dogs (ECSs and other breeds) showed marked increases in IgG4⁺ cells. There were no significant differences in the number of IgG4⁺ plasma cells between ECSs and dogs of other breeds for affected pancreas, liver, salivary glands and conjunctiva. Kidney sections had more IgG4⁺ cells, for both ECSs and dogs of other breeds, than did sections from other organs. Dogs of other breeds had significantly more IgG4⁺ plasma cells in affected kidneys than ECSs. In conclusion, several ECSs and dogs of other breeds fulfilled the histological criteria for the diagnosis of IgG4-RD, supporting the existence of a multiorgan immune-mediated disease in ECSs and some dogs of other breeds.

Mucosal expression of S100A12 (calgranulin C) and S100A8/A9 (calprotectin) and correlation with serum and fecal concentrations in dogs with chronic inflammatory enteropathy

S100A12 and S100A8/A9 (calprotectin) are released from activated mononuclear cells and belong to the group of damage associated molecular patterns. Fecal S100A12 and S100A8/A9 concentrations have been suggested as biomarkers of intestinal inflammation in dogs with chronic inflammatory enteropathies (CIE). However, the mucosal cellular infiltrate in dogs with CIE is primarily lymphocytic-plasmacytic. Whether fecal S100A12 and S100A8/A9 levels reflect the number and/or activity of intestinal mucosal mononuclear cells, or whether these proteins are also produced by other cells has not been investigated. Thus, the aim of this study was to evaluate intestinal mucosal S100A12 and S100A8/A9 positivity and a potential relationship with the respective protein concentrations in serum and fecal samples in dogs with CIE. Serum (single sample), fecal samples (from 3 consecutive days), and gastrointestinal tissue biopsies (i.e., stomach, duodenum, ileum, and colon) were evaluated from 21 dogs with CIE. Serum and fecal S100A12 and S100A8/A9 concentrations were measured by analytically validated in-house ELISAs. Tissue biopsies underwent routine histopathology and immunohistochemical evaluation for S100A12 and S100A8/A9 positivity (S100A12⁺ and S100A8/A9⁺, each recorded as positive cells/mm²). S100A12⁺ and S100A8/A9⁺ cells were identified in all segments of the gastrointestinal tract, but were predominantly localized in the lamina propria (LP). Duodenal LP S100A12 positivity correlated statistically significantly with that in the stomach and ileum (ρ = 0.66 and 0.69, both p < 0.01), but was inversely correlated with the severity of macrophage infiltration in the duodenum (ρ=-0.47, p = 0.042). Ileal LP S100A8/A9 positivity correlated positively with the extent of ileal neutrophil and macrophage infiltration (ρ=0.61, p = 0.047). Fecal S100A12 concentrations strongly correlated with the number of S100A12⁺ cells along the entire gastrointestinal tract (ρ = 0.76, p = 0.028), whereas serum S100A12 concentrations were inversely correlated to colonic S100A12⁺ cell counts (ρ=-0.50, p = 0.043). Mucosal S100A8/A9⁺ cell counts were not associated with the corresponding fecal or serum S100A8/A9 concentrations. These results suggest that the intestinal mucosa in dogs with CIE contains an increased number of activated (pro-inflammatory) phagocytes expressing and secreting the S100A12 protein, but the macrophage population seen on routine histopathology is predominantly mature (anti-inflammatory) with a reduced or absent expression of S100A12 and a normal or increased expression of S100A8/A9. However, the distribution of intestinal S100A8/A9 expression requires further study.

Detection of Leishmania spp. Infection by Immunohistochemistry in Archived Biopsy Samples from Dogs with Colitis in an Area Endemic for Leishmaniosis

Previous studies have demonstrated the presence of Leishmania infantum amastigotes in the colonic mucosa of seropositive sick dogs. However, there are no studies that have investigated the presence of L. infantum infection in dogs diagnosed with inflammatory bowel disease (IBD). The aims of this study were: (1) to investigate retrospectively the presence of Leishmania spp. antigen by immunohistochemistry (IHC) in biopsy samples taken from the colon of dogs with IBD in an area endemic for leishmaniosis, and (2) to describe the main histopathological findings in these cases. Clinicopathological data and histopathological results were reviewed from 106 cases of canine colitis. IHC to detect Leishmania spp. antigen had been performed at the time of diagnosis in 13 cases and we performed IHC in 56 more cases. Five of the 69 cases (7.2%) were positive for Leishmania spp. antigen by IHC. Two positive biopsy samples had histiocytic inflammation and three had lymphoplasmacytic inflammation. The number of amastigotes was variable and independent of the type and grade of inflammatory infiltrate. The results suggest that Leishmania spp. infection is associated with chronic colitis in areas endemic for the infection. Therefore, Leishmania IHC should be used routinely as a diagnostic tool when evaluating colonic biopsy samples from dogs in endemic areas, to exclude or confirm an infection by this parasite in dogs with chronic colitis.

Mucosal immunity and gut microbiota in dogs with chronic enteropathy

Chronic enteropathy (CE) in dogs is a chronic and relapsing immunopathology, of unknown etiology, that usually manifests with a plethora of clinical signs reflecting the underlying heterogeneity in its pathogenesis. Alterations of the mucosal immune responses and the gut microbiota composition are thought to play an essential role in CE. Similar to humans, it is hypothesized that the breakdown in mucosal tolerance leads to aberrant and pathological immune responses toward the gut microbiota, that in turn, may contribute to the severity of disease, at least for certain CE subsets. Therefore, in this review, we discuss some of the most relevant and recent insights microbiological and immunological aspects characterizing CE in dogs.

Changes in duodenal CD163-positive cells in dogs with chronic enteropathy after successful treatment

Chronic enteropathy (CE) in dogs is characterized retrospectively per treatment response as food-responsive enteropathy (FRE), antibiotic-responsive enteropathy (ARE), and immunosuppressant-responsive enteropathy (IRE) - the latter most resembling inflammatory bowel disease in people. The aim of this study was to characterize duodenal macrophages (Mϕ) in CE using immunohistochemistry; with calprotectin (CAL) as a marker of early differentiated Mϕ and CD163 expression as a marker for resident Mϕ in the duodenum before and after treatment. Prior to treatment, dogs with FRE and IRE had a lower CD163⁺/CAL⁺ ratio than control dogs (CTRL) in crypts; this increased significantly and normalized compared with CTRL after treatment. Conversely, the CD163⁺/CAL⁺ ratio in dogs with ARE was comparable to that in healthy dogs before and after treatment. In summary, these results suggest that Mϕ play a role in the pathogenesis of CE in FRE and IRE, with a decrease in resident Mϕ and an increase in early differentiated Mϕ, but not in ARE dogs. Mϕ normalize after successful treatment.

Granulomatous colitis: more than a canine disease? A case of Escherichia coli-associated granulomatous colitis in an adult cat

Case summary

This report describes a 4-year-old cat with chronic intermittent haematochezia and faecal incontinence of 7 months’ duration. Investigation revealed severe colonic multifocal mucosal ulcerations and infiltration of the mucosal lamina propria by large numbers of periodic acid–Schiff-positive macrophages. Fluorescence in situ hybridisation analysis of colonic biopsies revealed multifocal clusters of intracellular Escherichia coli. Treatment with fluoroquinolones for 6 weeks led to a complete resolution of clinical signs.

Relevance and novel information

The findings reveal that mucosally invasive E coli can also be associated with granulomatous colitis in cats and indicate the need for diagnostic testing of mucosal samples for E coli and other infectious agents.

Heterogeneity of macrophages in canine histiocytic ulcerative colitis

Histiocytic ulcerative colitis (HUC) is a chronic enteropathy which most notably occurs in Boxer dogs and French bulldogs. The inflamed mucosa is hallmarked by large, foamy, periodic acid–Schiff (PAS)-positive macrophages infiltrating the colonic mucosa. As little is known about their origin and phenotype, an immunohistochemical study was performed using different macrophage markers. Generally, canine colonic macrophages showed high expression of ionised calcium-binding adaptor molecule 1 and MHC class II. In canine HUC, macrophages revealed up-regulation of lysozyme and L1 Ag but decreased CD163 expression compared with controls, suggesting them to be pro-inflammatory cells, whereas the healthy colonic mucosa was characterised by an anti-inflammatory macrophage phenotype. In addition, PAS reaction was used to discriminate macrophage subpopulations. PAS– macrophages displayed higher expression of L1 Ag and CD64, whereas PAS+ cells, which were only present in HUC patients, were characterised by increased expression of lysozyme, inducible nitric oxide synthase and CD204. This indicates PAS+ cells to be mature macrophages contributing to the inflammatory process, which are most likely maintained by differentiation of immature PAS– macrophages continuously recruited from blood monocytes. In summary, macrophage heterogeneity in canine HUC probably illustrates their different maturation states and functions compared with the healthy animals.

Measurement of IL-12 (p40, p35), IL-23p19, and IFN-γ mRNA in duodenal biopsies of cats with inflammatory enteropathy

Background

Dietary hypersensitivity and inflammatory bowel disease (IBD) are important causes of chronic vomiting and diarrhea in cats. IL‐23 has been recently found to be a key factor in the immunopathogenesis of IBD in humans but the involvement in IBD has not been investigated in cats.

Hypothesis/Objectives

Expression of genes encoding Il‐12p35 and p40, IL‐23p19, and IFN‐γ may be up‐regulated in duodenal biopsy specimens taken from cats with histologic evidence of inflammation.

Animals and Methods

Duodenal biopsy specimens were collected from control cats (n = 21) and cats with inflammatory enteropathy (n = 13). Routine histopathology, immunohistochemistry (IHC), and qRT‐PCR were used to assess expression of MHC class II and to measure gene transcripts encoding the p35, p40, and p19 subunits of the IL‐12 family of cytokines and IFN‐γ.

Results

There were significant differences in expression of mRNA encoding IL‐12p35 and IL‐23p19 between healthy cats and cats with inflammatory enteropathy. IL‐12p35 mRNA was lower in the duodenal mucosa of cats with inflammatory enteropathy compared with the mucosa of healthy cats (P = .001). In contrast, IL‐23p19 mRNA expression was higher in duodenal biopsy specimens from cats with inflammatory enteropathy than in those from healthy controls (P = .001). There was no difference in expression of IL‐12p40 and IFN‐γ mRNA (P > .05). The majority of cats with inflammatory enteropathy had histologic evidence of moderate to severe colitis (score 2).

Conclusions and Clinical Importance

The results of this preliminary study suggest that IL‐23 plays a role in the pathogenesis of feline inflammatory enteropathy.

Tumour-associated macrophages are associated with vascular endothelial growth factor expression in canine mammary tumours

Tumour-associated macrophages (TAMs) have been implicated in carcinogenesis including an important role in angiogenesis. In this study, we describe the relationship between TAMs and angiogenesis in canine mammary tumours (CMT). Formalin-fixed paraffin-embedded CMT samples [(n = 128: malignant (n = 97) and benign (n = 31)] were submitted to immunohistochemical staining to detect MAC387, vascular endothelial growth factor VEGF and CD31 expression. A statistical analysis was carried out to assess possible associations with clinicopathological variables and biological markers of tumour angiogenesis. TAMs, detected by MAC387 expression, were significantly associated with malignant CMT (P < 0.001) and VEGF positive tumours (P = 0.002) and also associated with VEGF expression within malignant CMT (P = 0.043). Associations with clinicopathological variables were found between TAMs and the presence of infiltrative growth (P = 0.031), low tubule formation (P = 0.040) and lymph node metastasis (P = 0.016). The results support the hypothesis that TAMs influence angiogenesis in CMT suggesting TAMs may represent a therapeutic target in this disease.

Evaluation of serum cobalamin concentrations in dogs of 164 dog breeds (2006–2010)

Altered serum cobalamin concentrations have been observed in dogs with gastrointestinal disorders such as exocrine pancreatic insufficiency (EPI) or gastrointestinal inflammation. The aims of the current study were 1) to identify breeds with a higher proportion of dogs with a decreased serum cobalamin concentration, 2) to determine whether dogs with such decreased concentrations tend to have serum canine trypsin-like immunoreactivity (cTLI) concentrations diagnostic for EPI, and 3) to compare the number of submissions for serum cobalamin analysis by breed to the American Kennel Club (AKC) breed ranking list of 2009. In this retrospective study, results of 28,675 cobalamin tests were reviewed. Akitas, Chinese Shar-Peis, German Shepherd Dogs, Greyhounds, and Labrador Retrievers had increased proportions of serum cobalamin concentrations below the lower limit of the reference interval (<251 ng/l; all P < 0.0001). Akitas, Chinese Shar-Peis, German Shepherd Dogs, and Border Collies had increased proportions of serum cobalamin concentrations below the detection limit of the assay (<150 ng/l; all P < 0.0001). Akitas, Border Collies, and German Shepherd Dogs with serum cobalamin concentrations <150 ng/l were more likely to have a serum cTLI concentration considered diagnostic for EPI (≤2.5 µg/l; all P ≤ 0.001). The breed with the highest proportion of samples submitted for serum cobalamin analysis in comparison with the AKC ranking list was the Greyhound (odds ratio: 84.6; P < 0.0001). In Akitas and Border Collies, further investigations are warranted to clarify if a potentially breed-specific gastrointestinal disorder is responsible for the increased frequency of decreased serum cobalamin and cTLI concentrations.

Prognostic value of tumour-associated macrophages in canine mammary tumours

Tumour-associated macrophages (TAMs) have already been associated in human breast cancer to a poor prognosis. As a part of a tumoural microenvironment, TAMs have an important contribution influencing neoplastic progression. Hitherto, in canine mammary tumours (CMT) the prognostic value of TAMs has not been reported. In this study, MAC387 immunohistochemical expression was evaluated in 59 CMTs (20 benign and 39 malignant). The TAM value was significantly higher in malignant than benign CMT (P = 0.011). In malignant CMT, TAMs were associated with skin ulceration (P = 0.022), histological type (P = 0.044), nuclear grade (P = 0.031) and tubular differentiation (P = 0.042). The survival analysis revealed a significant association between tumours with higher levels of TAMs and the decrease in overall survival (P = 0.030). TAMs have proven to have a prognostic value. These findings suggest the future possibility of using TAMs as a novel therapeutic target in CMT.

Granulomatous colitis of boxer dogs

Granulomatous colitis (GC) is a rare, breed-specific inflammatory bowel disease of young Boxer dogs. GC has been refractory to treatment and associated with high mortality rates, but culture-independent molecular analysis has transformed therapy and prognosis by uncovering a correlation between GC and Escherichia coli invasion within colonic mucosal macrophages. GC-associated invasive E coli are similar to a newly identified E coli pathotype, "adherent and invasive E coli," that are increasingly associated with Crohn's disease in humans. Successful treatment of GC requires antimicrobials that are effective against E coli and penetrate intracellularly. Enrofloxacin is widely regarded as the antibiotic of choice.

Antimicrobial resistance impacts clinical outcome of granulomatous colitis in boxer dogs

BACKGROUND

Escherichia coli have recently been identified within the colonic mucosa of Boxer dogs with granulomatous colitis (GC). Eradication of invasive E. coli is associated with clinical and histological remission.

OBJECTIVES

To determine antimicrobial susceptibility profiles of E. coli strains from GC and healthy dogs, and the association of antimicrobial resistance with clinical outcome.

ANIMALS

Fourteen Boxer dogs with GC and 17 healthy pet dogs.

METHODS

Prospective study: E. coli was cultured from GC biopsies and rectal mucosal swabs of healthy dogs. Individual strains were selected by phylogroup and overall genotype, determined by triplex- and random amplified polymorphic DNA-polymerase chain reaction respectively. Antimicrobial susceptibility was determined by broth microdilution minimal inhibitory concentration.

RESULTS

Culture yielded 23 E. coli strains from GC (1-3/dog, median 2) and 34 strains from healthy (1-3/dog, median 2). E. coli phylogroups were similar (P=.18) in GC (5A, 7B1, 5B2, 6D) and healthy (2A, 10B1, 15B2, 7D). Resistance to ampicillin, amoxicillin-clavulanate, cefoxitin, tetracycline, trimethoprim-sulfa (TMS), ciprofloxacin, and chloramphenicol was greater (P<.05) in GC (21-64%) than healthy (0-24%). Enrofloxacin resistant E. coli were isolated from 6/14 GC versus 0/17 healthy (P=.004). Of the enrofloxacin resistant cases, 4/6 were also resistant to macrophage-penetrating antimicrobials such as chloramphenicol, rifampicin, and TMS. Enrofloxacin treatment before definitive diagnosis was associated with antimicrobial resistance (P<.01) and poor clinical outcome (P<.01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Antimicrobial resistance is common among GC-associated E. coli and impacts clinical response. Antimicrobial therapy should be guided by mucosal culture and antimicrobial susceptibility testing rather than empirical wisdom.

Histopathological standards for the diagnosis of gastrointestinal inflammation in endoscopic biopsy samples from the dog and cat: a report from the World Small Animal Veterinary Association Gastrointestinal Standardization Group

The characterization of inflammatory change in endoscopic biopsy samples of the gastrointestinal mucosa is an increasingly important component in the diagnosis and management of canine and feline gastrointestinal disease. Interpretation has hitherto been limited by the lack of standard criteria that define morphological and inflammatory features, and the absence of such standardization has made it difficult, if not impossible, to compare results of retrospective or prospective studies. The World Small Animal Veterinary Association (WSAVA) Gastrointestinal Standardization Group was established, in part, to develop endoscopic and microscopical standards in small animal gastroenterology. This monograph presents a standardized pictorial and textual template of the major histopathological changes that occur in inflammatory disease of the canine and feline gastric body, gastric antrum, duodenum and colon. Additionally, a series of standard histopathological reporting forms is proposed, to encourage evaluation of biopsy samples in a systematic fashion. The Standardization Group believes that the international acceptance of these standard templates will advance the study of gastrointestinal disease in individual small companion animals as well as investigations that compare populations of animals.

Adherent and invasive Escherichia coli is associated with granulomatous colitis in boxer dogs

The mucosa-associated microflora is increasingly considered to play a pivotal role in the pathogenesis of inflammatory bowel disease. This study explored the possibility that an abnormal mucosal flora is involved in the etiopathogenesis of granulomatous colitis of Boxer dogs (GCB). Colonic biopsy samples from affected dogs (n = 13) and controls (n = 38) were examined by fluorescent in situ hybridization (FISH) with a eubacterial 16S rRNA probe. Culture, 16S ribosomal DNA sequencing, and histochemistry were used to guide subsequent FISH. GCB-associated Escherichia coli isolates were evaluated for their ability to invade and persist in cultured epithelial cells and macrophages as well as for serotype, phylogenetic group, genome size, overall genotype, and presence of virulence genes. Intramucosal gram-negative coccobacilli were present in 100% of GCB samples but not controls. Invasive bacteria hybridized with FISH probes to E. coli. Three of four GCB-associated E. coli isolates adhered to, invaded, and replicated within cultured epithelial cells. Invasion triggered a "splash"-type response, was decreased by cytochalasin D, genistein, colchicine, and wortmannin, and paralleled the behavior of the Crohn's disease-associated strain E. coli LF 82. GCB E. coli and LF 82 were diverse in serotype and overall genotype but similar in phylogeny (B2 and D), in virulence gene profiles (fyuA, irp1, irp2, chuA, fepC, ibeA, kpsMII, iss), in having a larger genome size than commensal E. coli, and in the presence of novel multilocus sequence types. We conclude that GCB is associated with selective intramucosal colonization by E. coli. E. coli strains associated with GCB and Crohn's disease have an adherent and invasive phenotype and novel multilocus sequence types and resemble E. coli associated with extraintestinal disease in phylogeny and virulence gene profile.

Antigen presenting cells in mucosal sites of veterinary species

The ability of antigen presenting cells, in particular dendritic cells, to integrate a variety of environmental signals, together with their ability to respond appropriately by initiating either tolerance or defensive immune responses make them cells of particular relevance and importance in the mucosal environment. They have been demonstrated in a variety of mucosal tissues in veterinary species and have been characterized to varying degrees, showing that fundamental immunological principles apply throughout all species, but also highlighting some species differences. A major advantage of carrying out immunological research in veterinary species is their size: it is possible to cannulate lymphatic ducts and obtain information about cell migration between different tissues. It is also possible to obtain pure populations of relatively rare cell types such as the plasmacytoid dendritic cells or mucosal dendritic cells ex vivo for the study of immune responses to diseases in their natural host and for other thorough functional studies. Two major myeloid antigen presenting cell (APC) (dendritic cells, DC) cell populations have been described in gut draining lymph and other mucosal sites in ruminants and pigs, characterised by the presence or absence of surface molecules, their enzyme profiles, their ability to phagocytose and their different potential as APC. There is evidence that one of these subsets has migrated from the diffuse mucosal tissue, where it is found as a phagocytic as well as stimulatory APC population, which in turn may be derived from blood macrophages. In addition, the presence and role in viral infection of the IFN-alpha producing plasmacytoid DC in mucosal tissue is discussed, based on studies in pigs.

Chronic inflammatory disorders of the gastrointestinal tract of companion animals

In the inflammatory bowel diseases (IBD) that affect dogs and cats there appears to be dysregulation of normal mucosal immunity, characterised by polyclonal lymphocytic infiltrates which are presumably specific for luminal antigens. There is an absence of a classical polarisation of either T-helper (Th) 1 or Th2 cytokine responses, although increased expression of mRNA for interleukin (IL) 2 and IL-12p40 and a shift towards mucosal immunoglobulin (Ig) G production are consistent findings, whilst variable responses are seen in tumour necrosis factor-alpha (TNF-alpha), IL-1, IL-4, IL-6, and interferon-gamma (IFN-gamma). Increased mucosal permeability and deranged intestinal motility are common sequelae. Despite obvious similarities with Crohn's disease and ulcerative colitis in humans, important differences exist. Of these, the diffuse superficial nature but with no Th1 or Th2 bias, and the prevalence of proximal small intestinal disease are notable. Potential hypotheses for these disparities include specific differences in the types or locations of agonistic gut flora, diffuse abnormalities in microbial-host interactions, a greater importance of diet, or anatomical or cellular differences in mucosal immune responses. Although specific pathogens and genetic susceptibilities may be involved, quantitative or qualitative changes in the normal flora or abnormal responses to a normal flora are more likely to be involved in the immunopathogenesis. Dietary influences include a large source of antigen, promotion of abnormal microbial growth through Maillard compounds within canned diets, and specific macro- and micronutrient deficiencies. Although dependent on a histopathological diagnosis, limitations of biopsies procured endoscopically, lack of histopathological standardisation and difficulty distinguishing inflammation from neoplasia remain significant problems. Clinician-pathologist dialogue, immunohistochemistry, cytokine profiling and lymphocyte clonality assessment may lead to more accurate diagnoses, a deeper understanding of the immunopathogenesis, and ultimately to new therapies or prevention of disease induction.

Successful management of histiocytic ulcerative colitis with enrofloxacin in two Boxer dogs

Two Boxer dogs with histologically confirmed histiocytic ulcerative colitis were treated with enrofloxacin, one as sole therapy and one in conjunction with prednisolone, after failure of standard therapy. Clinical remission occurred rapidly in both dogs after commencement of enrofloxacin and in one case where repeat colonoscopy was performed the endoscopic appearance of the mucosa was normal within 2 weeks. Histological examination of the colonic mucosa in this dog after 7 months showed resolution of the cellular infiltration characteristic of histiocytic ulcerative colitis. Histological improvement following therapy in Boxer dogs with histiocytic ulcerative colitis has not been reported previously.

Animal models of inflammatory bowel disease: an overview

Inflammatory bowel disease (IBD) research has been performed in human in vitro studies and in in vivo studies using appropriate animal models. Such animal models allow both the examination of inflammatory processes (both early and late events) as well as the evaluation of new therapeutic modalities. Since the first description of the immune complex colitis in rabbits in 1961, overall 63 models have been described, most of which within the last decade. These IBD animal models can be divided into 5 different categories: (1) antigen-induced colitis and colitis induced by microbials; (2) other inducible forms of colitis (chemical, immunological, and physical); (3) genetic colitis models (transgenic and knock-out models); (4) adoptive transfer models, and (5) spontaneous colitis models. In spite of the high overall number of models, none of them is the 'perfect' model and therefore numerous aspects need to be considered when choosing one model for a particular study. Importantly, most clinical aspects (e.g. extraintestinal manifestations or fistula) have recently been described in one or the other model allowing further studies with relevance for almost all aspects of IBD. So far, IBD animal models have taught us important lessons, e.g. the requirement of T-helper cells in most models, the need of a particular genetic background, and the role of the flora in the initiation of IBD. It is expected that our understanding of IBD will further increase in a number of additional areas using animal models, e.g. exploring the role of the innate immune system in IBD.

Histiocytic ulcerative colitis in a French bulldog

A 9-month-old French bulldog was referred for signs of chronic large bowel diarrhea. The dog had an increased frequency of defecation, tenesmus and hematochezia. Flexible colonoscopy showed hyperemia, irregularities and ulcerations with multifocal hemorrhages in the mucosa from the descending colon to the proximal rectum. Multiple colonic biopsies were characterized by infiltrations of PAS positive histiocytes in the lamina propria. A diagnosis of histiocytic ulcerative colitis (HUC) was made, and the animal showed only minimal improvement, although it was treated with nutritional and medical therapies. This is the second case of HUC in French bulldog, a breed which has ancestral relations to Boxer dogs.

The distribution of leucocyte subsets in the small intestine of healthy cats

The aim of this study was to investigate the distribution of leucocyte subsets in the small intestine of healthy adult cats (n=16). Immunohistochemical methods were used to identify leucocyte subsets within the mucosa of the duodenum, jejunum and ileum. Computer-aided morphometry was used to enumerate cells within the epithelial compartment, villous lamina propria and lamina propria adjacent to upper and lower crypt. Throughout the small intestine, IgA+ and IgM+ plasma cells were more prominent in the lamina propria adjacent to the lower crypt than in the villus, whereas IgG+ plasma cells were present in equal numbers in the crypt and villous regions. Overall, IgA+ plasma cells predominated and IgM+ plasma cells were higher in number than IgG+ plasma cells at each of the three anatomical locations. By contrast, T cells (CD3+) and T-cell subsets (CD4+ and CD8+) were present in greater numbers in the villous lamina propria than in the lamina adjacent to the crypts. Intraepithelial lymphocytes (IELs) were also characterized phenotypically, the majority being CD8+ T lymphocytes. Lamina propria macrophages and dendritic cells were characterized by expression of L1 and major histocompatibility complex (MHC) class II, and MHC class II expression by enterocytes overlying Peyer's patches, although rare, was also shown. The qualitative and quantitative data from this study provide a basis for comparison with cats with inflammatory enteropathies.