Update on immununosuppressive therapies for dogs and cats

Retrospective evaluation of leflunomide as an adjunctive therapy in dogs with non-associative immune-mediated thrombocytopenia: 20 cases (2008-2021)

OBJECTIVE

To describe leflunomide as an adjunctive therapy in the treatment of non-associative immune-mediated thrombocytopenia.

MATERIALS AND METHODS

A retrospective study of dogs with a diagnosis of non-associative immune-mediated thrombocytopenia treated with leflunomide March 2008 to September 2021 was conducted. Data collected included signalment, clinical signs, physical examination findings and diagnostic testing performed. Medications administered, duration of hospital stay, time to platelet concentration >150×109/L and adverse events during leflunomide therapy were recorded. Relapses within a year of diagnosis were reported.

RESULTS

A total of 20 client-owned dogs met inclusion criteria. Nineteen of 20 dogs (95%) achieved a platelet concentration >150×109/L with leflunomide and prednisone combination therapy and four dogs (21.1%) relapsed during treatment or shortly after treatment. Adverse effects included diarrhoea (n=5), mild lymphopenia (n=9) and mild intermittent anaemia (n=1). A single dog developed hepatotoxicity presumed to be secondary to leflunomide therapy that resolved after drug discontinuation. One dog was treated for aspiration pneumonia during treatment. Two dogs were euthanased while receiving leflunomide.

CLINICAL SIGNIFICANCE

Length of hospitalisation, time to platelet recovery, treatment response and relapse rate were comparable with alternative treatment protocols. Most adverse effects did not require leflunomide dose adjustment; however, two dogs died while undergoing leflunomide treatment and there is compelling evidence that one of these dogs experienced fatal infection secondary to immune-suppression. Hepatotoxicity remains a known complication of leflunomide treatment and serial biochemistry testing is recommended.

Clinical and pathological findings in five dogs with nodular histiocytic iritis in the United Kingdom: A case series

PURPOSE

The aim of this study was to describe the clinical presentation, histopathology, management, and outcome of nodular histiocytic iritis, an intraocular variant of nodular granulomatous episcleritis (NGE).

METHODS

A retrospective review of the medical records of five dogs with intraocular NGE-type inflammation as diagnosed by histopathology.

RESULTS

Four Border Collies and one crossbreed dog, aged 1.5-3.4 years (mean age 2.38 years). The clinical presentation was an extensive, raised, pale iris lesion of variable location. All cases were unilateral. The physical examination was normal. Complete blood count/serum biochemistry (n = 1) and thoracic radiography (n = 1) were normal. Ocular ultrasound (n = 2) was normal apart from increased iris thickness. Enucleation (n = 4) or excisional biopsy (iridectomy, n = 1) was performed because of suspected neoplasia. Following enucleation, the remaining, contralateral eye did not develop additional lesions (9 days-3.7 years follow-up). There was no recurrence following sector iridectomy with 5 months topical 1% prednisolone acetate (3.9 years follow-up). The histopathologic findings in all five cases indicated a focal histiocytic and lymphoplasmacytic anterior uveitis (iritis), similar to that seen in cases of NGE.

CONCLUSION

Nodular histiocytic iritis presents as unilateral iris thickening in isolation and young Collies appear to be predisposed. The histopathological findings are similar to NGE. Although the clinical presentation resembles intraocular neoplasia, an inflammatory process should be considered, which may be amenable to medical management. Definitive diagnosis may be obtained by iris sampling.

Novel Management of Masticatory Myositis in Three Dogs with a Selective Janus Kinase (JAK-1) Inhibitor

Masticatory myositis (MM) is an inflammatory myopathy reported in dogs and is characterized by inflammation of the masticatory muscles (temporalis, masseter, and pterygoid muscles). Immunosuppressive therapy is the current recommended treatment for MM and may involve glucocorticoids, cyclosporine, azathioprine, mycophenolate mofetil, leflunomide, or a combination of these treatments that are slowly tapered to the lowest effective dose. However, side effects from multimodal medical therapy and complications associated with MM relapses have been reported. The purpose of this case series was to report oclacitinib as a treatment alternative to traditional medical management of MM. The intent of this alternative is to manage side effects from glucocorticoid use. Oclacitinib (1mg/kg per os q12h) was used solely for treatment of MM in three dogs. The dogs were followed up to >6 months after oclacitinib administration. An increase in oral range of motion, as determined by gape angle, was noted in all three dogs. However, a corresponding drop in antibody titers (2M fiber) did not occur. All dogs showed improvement in overall clinical management of MM, side effects from glucocorticoids, and clinical signs related to chronic prednisone use. Larger controlled trials with consistent measurements (interincisal distance, gape angle) and 2M fiber antibody titers are indicated to further assess validation of oclacitinib treatment of MM. The clinical outcome of all dogs was considered successful.

Leflunomide for the Treatment of Immune-Mediated Uveitis in a Dog

A 5 yr old castrated male bichon frise presented with chronic bilateral uveitis that had previously been controlled with systemic steroid administration for 6 mo, resulting in weight gain, polyuria, and polydipsia. To control the uveitis without systemic side effects, oral cyclosporine was started after discontinuing oral steroid, but discontinued one month later because of severe vomiting. Leflunomide (2 mg/kg q 12 hr) was initiated, and the uveitis symptoms resolved after 2 mo. The dose was tapered according to the remission of clinical signs, with no relapse during the following 13 mo. Leflunomide therapy was then discontinued due to vomiting caused by severe gastroenteritis and pancreatitis, and topical prednisolone monotherapy was continued . At 8 mo after discontinuation of leflunomide, bilateral uveitis recurred, and leflunomide therapy was resumed. However, the patient lost vision due to the progression of clinical signs at 33 mo after commencing leflunomide, and evisceration of the glaucomatous right eye was performed at 43 mo. Histopathologic examination revealed lymphocyte and plasma cell infiltration and melanin-laden macrophages in the uveal tissue, and the patient was diagnosed with immune-mediated uveitis. This case indicated that oral leflunomide may be a viable treatment option for canine idiopathic immune-mediated uveitis.

Generalised pustular onychopathy of unknown aetiology in a domestic cat

Claw diseases are rare in cats and often associated with cutaneous lesions in other regions of the body. This case report describes an atypical manifestation of a generalised onychopathy of unknown origin in a domestic short hair cat.

Description and outcome of dogs with primary immune-mediated polyarthritis: 73 cases (2012-2017)

OBJECTIVES

To provide a description of primary idiopathic immune-mediated polyarthritis, including long-term outcome and relapse rates, for dogs starting treatment with corticosteroids alone or corticosteroids with a second immunosuppressant.

MATERIALS AND METHODS

Medical records were reviewed between January 2012 and December 2017 to identify dogs diagnosed with primary immune-mediated polyarthritis. Data including signalment, clinicopathological findings, type and duration of treatment, relapse and outcome were recorded.

RESULTS

Seventy-three dogs were included. Fifty-four dogs were started on corticosteroid monotherapy (an additional immunosuppressant was introduced later in 27/54 dogs) and 19 dogs were treated with multi-modal immunosuppression from the outset. Ninety-five percent (69/73) of dogs responded favourably to therapy although death was attributed to immune-mediated polyarthritis in 19% (14/73) of dogs. Relapse of clinical signs was reported in 53% (39/73) dogs (31/39 while on treatment), with multiple relapses observed in 17 dogs. Complete cure (permanent withdrawal of immunosuppressive medication) was achieved in 46 dogs (63%). Overall, 81% of dogs had a well-managed disease for an extended timeframe (≥1131 days). Fourteen of 19 (74%) dogs that started treatment with multi-modal immunosuppression and 32 of 54 (59%) started on corticosteroids alone achieved a complete cure.

CLINICAL SIGNIFICANCE

This study provides extended follow-up information for a large cohort of dogs with primary immune-mediated polyarthritis. Immunosuppressive therapy was discontinued in the majority of dogs but disease-associated mortality remains high.

Prednisolone prescribing practices for dogs in Australia

Although prednisolone is a routinely prescribed medication in dogs, there is a lack of information regarding prednisolone prescribing practices by veterinarians. This study aims to describe characteristics of dogs receiving prednisolone, disease processes treated, doses prescribed as well as to identify factors influencing the dose rate in Australia. The VetCompass Australia database was queried to identify dogs prescribed prednisolone between 1 July 2016 to 31 July 2018 (inclusive). A random sample of 2,000 dogs from this population were selected. Dog demographic data, prednisolone dose and indication for prescription were collated. Indicated dose for the condition treated was compared to prescribed dose. Multivariable linear regression was used to identify patient-level characteristics associated with prescribed prednisolone dose. A large and small breed dog cohort, treated for the same disease process, were compared for differences in dosing. Median age of dogs was 73 (range 2 to 247) months and median body weight was 17 (range 1.56 to 90) kg. Median prescribed prednisolone dose was 0.8 mg/kg/day, with most dogs receiving an anti-inflammatory dose (0.3-1 mg/kg/day, 58%). Prednisolone prescriptions were predominantly for diseases of the integument (n = 1645, 82%) followed by unknown indication and respiratory disease. A total of 152 dogs (8%) were prescribed immunosuppressive doses of prednisolone for conditions where an anti-inflammatory dose would be recommended. Increases in bodyweight were associated with lower doses on mg/kg scale but higher doses on a mg/m2 scale (p < 0.001). Overall, prednisolone was primarily used as an anti-inflammatory in this population, with some inappropriate use of immunosuppressive doses. Increasing bodyweight was associated with a small reduction in dose in mg/kg, suggesting that clinicians are adjusting prednisolone dose rates based on dog bodyweight.

Chronic Intestinal Disorders in Humans and Pets: Current Management and the Potential of Nutraceutical Antioxidants as Alternatives

Simple Summary

Chronic disorders of the intestinal tract (CID) are characterized by signs of inflammation of the intestine for a period of at least three weeks. Both humans and pets can be affected by these disorders. Different therapeutic approaches can be selected to treat patients and the use of natural products has been increased in the last decade, since oxidative stress plays a key role in the progression of the chronic intestinal disorders. In this review, the antioxidant proprieties of several natural products with potential for treatment of CID in human and veterinary medicine are highlighted. Unfortunately, few clinical trials report the use of these products for treating CID in humans and none in animals.

Abstract

Chronic intestinal disorders (CID) are characterized by persistent, or recurrent gastrointestinal (GI) signs present for at least three weeks. In human medicine, inflammatory bowel disease (IBD) is a group of chronic GI diseases and includes Crohn’s disease (CD) and ulcerative colitis (UC). On the other hand, the general term chronic enteropathies (CE) is preferred in veterinary medicine. Different therapeutic approaches to these diseases are used in both humans and pets. This review is focused on the use of traditional therapies and nutraceuticals with specific antioxidant properties, for the treatment of CID in humans and animal patients. There is strong evidence of the antioxidant properties of the nutraceuticals included in this review, but few studies report their use for treating CID in humans and none in animals. Despite this fact, the majority of the nutraceuticals described in the present article could be considered as promising alternatives for the regular treatment of CID in human and veterinary medicine.

Nonpharmacological Treatment Strategies for the Management of Canine Chronic Inflammatory Enteropathy—A Narrative Review

Chronic inflammatory enteropathy (CIE) refers to a heterogeneous group of idiopathic diseases of the dog characterised by persistent gastrointestinal (GI) clinical signs. If conventional dietary treatment alone would be unsuccessful, management of CIE is traditionally attained by the use of pharmaceuticals, such as antibiotics and immunosuppressive drugs. While being rather effective, however, these drugs are endowed with side effects, which may impact negatively on the animal’s quality of life. Therefore, novel, safe and effective therapies for CIE are highly sought after. As gut microbiota imbalances are often associated with GI disorders, a compelling rationale exists for the use of nonpharmacological methods of microbial manipulation in CIE, such as faecal microbiota transplantation and administration of pre-, pro-, syn- and postbiotics. In addition to providing direct health benefits to the host via a gentle modulation of the intestinal microbiota composition and function, these treatments may also possess immunomodulatory and epithelial barrier-enhancing actions. Likewise, intestinal barrier integrity, along with mucosal inflammation, are deemed to be two chief therapeutic targets of mesenchymal stem cells and selected vegetable-derived bioactive compounds. Although pioneering studies have revealed encouraging findings regarding the use of novel treatment agents in CIE, a larger body of research is needed to address fully their mode of action, efficacy and safety.

Immunomodulatory and immunosuppressive drug protocols in the treatment of canine primary immune thrombocytopenia, a scoping review

Primary immune thrombocytopenia (ITP) is a cause of severe thrombocytopenia in dogs. Immunosuppressive corticosteroid drugs are frequently used in the management of ITP, but treatment failure may occur. Immunomodulatory and non-corticosteroid immunosuppressive drugs might improve outcomes from therapy either alone or in combination with corticosteroids. The objectives of this scoping review were (1) to evaluate the current evidence relating to immunomodulatory and immunosuppressive drug protocols in the treatment of canine ITP, and (2) to answer the clinical question, whether or not therapy with immunomodulatory or non-corticosteroid immunosuppressive drugs alone or in combination with corticosteroids could improve outcome, compared to therapy with corticosteroids alone. A literature search was performed in the electronic databases of Agricola, CAB Abstracts, Embase, Medline and Web of Science for publications in November 2019 and again February 1, 2021. Selection criteria were relatively strict and included peer-reviewed research papers reporting outcome measures from immunomodulatory and immunosuppressive drug protocols in the treatment of canine ITP with a pre-therapeutic mean or median platelet count < 50,000/µL as a strict criterion for inclusion. Studies were evaluated if they had an appropriate diagnostic work up to exclude underlying conditions. Outcome measures and adverse events were compared between drug protocols both within studies and between studies. The search identified 456 studies, with six studies being eligible for inclusion. The studies were mostly case series while two were randomized controlled trials. Level of evidence varied with an overall uncertain subject enrollment, small groups, inadequate description and variable use of drug protocols or outcome measures. For outcomes such as platelet recovery time and duration of hospitalization, an improvement was observed using adjunctive therapy (human intravenous immunoglobulin) compared to therapy with corticosteroids alone. For outcomes of complete platelet recovery time, survival (6-month), mortality and relapse, no improvement was observed using adjunctive drugs compared to corticosteroids alone. Specifically, therapy with mycophenolate mofetil alone and adjunctive azathioprine were associated with more severe adverse events compared to other drug protocols. Evidence relating to immunomodulatory and immunosuppressive drug protocols in the treatment of canine ITP was of variable quality. Future larger case-controlled trials are required for determination of optimal treatment protocols in canine ITP.

Methylprednisolone Induces Extracellular Trap Formation and Enhances Bactericidal Effect of Canine Neutrophils

Methylprednisolone is a glucocorticoid and can negatively influence immune defense mechanisms. During bacterial infections in the dog, neutrophils infiltrate infected tissue and mediate antimicrobial effects with different mechanisms such as phagocytosis and neutrophil extracellular trap (NET) formation. Here, we investigated the influence of methylprednisolone on canine NET formation and neutrophil killing efficiency of Gram positive and Gram negative bacteria. Therefore, canine blood derived neutrophils were treated with different concentrations of methylprednisolone over time. The survival factor of Staphylococcus pseudintermedius, Streptococcus canis or Escherichia coli was determined in presence of stimulated neutrophils. Additionally, free DNA and nucleosomes as NET marker were analyzed in supernatants and neutrophils were assessed for NET formation by immunofluorescence microscopy. Methylprednisolone concentrations of 62.5 and 625 µg/mL enhanced the neutrophil killing of Gram positive bacteria, whereas no significant influence was detected for the Gram negative Escherichia coli. Interestingly, higher amounts of free DNA were detected under methylprednisolone stimulation in a concentration dependency and in the presence of Streptococcus canis and Escherichia coli. The nucleosome release by neutrophils is induced by bacterial infection and differs depending on the concentration of methylprednisolone. Furthermore, immunofluorescence microscopy analysis identified methylprednisolone at a concentration of 62.5 µg/mL as a NET inducer. In summary, methylprednisolone enhances NET-formation and time-dependent and concentration-dependent the bactericidal effect of canine neutrophils on Gram positive bacteria.

Dexamethasone Can Be Safely and Effectively Used for Treatment of Masticatory Muscle Myositis in Dogs

Dexamethasone is the glucocorticoid of choice in many human inflammatory and immune-mediated conditions, given its reported effectiveness and limited side effect profile. In veterinary medicine, the glucocorticoid of choice is prednisone, however the safety of longer-term use of dexamethasone has not previously been studied. The aim of this study was to evaluate the safety, effectiveness and side effects of dexamethasone use as the glucocorticoid treatment for masticatory muscle myositis in dogs - an immune-mediated inflammatory condition. 93% of dogs showed a clinical improvement within two weeks of treatment, and 100% by ten weeks. 35% of dogs showed adverse reactions, however these were all mild and resolved with tapering of the dexamethasone dose. In conclusion, dexamethasone can be safely and effectively used for the treatment of masticatory muscle myositis in dogs, and should be considered for use in these cases, either alone or alongside additional immunosuppressive medications. Side effects are mild and resolve with tapering of the dexamethasone dose.

Evaluating the use of cytosine arabinoside for treatment for recurrent canine steroid-responsive meningitis-arteritis

Background

Relapses in steroid-responsive meningitis-arteritis (SRMA) are frequently observed but specific treatment protocols to address this problem are sparsely reported. Standard treatment includes prolonged administration of glucocorticoids as monotherapy or in combination with immunosuppressive drugs. The aim of this study was to assess the safety and efficacy of cytosine arabinoside (CA) in combination with glucocorticoids for treatment of SRMA relapses in 12 dogs on a retrospective basis.

Methods

Dogs with recurrent episodes of SRMA and treated with a combination of CA and prednisolone were included. Information about clinical course, treatment response and adverse events was collected from medical records. Ethical approval was not required for this study.

Results

Ten dogs (10/12) responded well to the treatment with clinical signs being completely controlled. One dog is in clinical remission, but still under treatment. One dog (8%) showed further relapse. Mean treatment period was 51 weeks. Adverse events of variable severity (grade 1–4/5) were documented in all dogs during treatment according to the veterinary cooperative oncology group grading. Three dogs developed severe adverse events. Laboratory findings showed marked changes up to grade 4. Diarrhoea and anaemia were the most often observed adverse events (6), followed by dermatitis (4), alopecia (3) and pneumonia (3). Including blood chemistry changes (13), 50 adverse events were found in total.

Conclusion

Treatment with CA and glucocorticoids resulted in clinical remission in 10/12 dogs, but a high incidence of adverse events occurred requiring additional measures. All adverse events could be managed successfully in all cases.

Prospective evaluation of a change in dietary therapy in dogs with steroid-resistant protein-losing enteropathy

OBJECTIVE

To describe the clinical effect of dietary alteration as a sole change to therapy in dogs with steroid-resistant protein-losing enteropathy.

MATERIALS AND METHODS

Prospective study. Eligible enrolled dogs received dietary alteration as sole change to their therapeutic plan. Canine Chronic Enteropathy Clinical Activity Index and serum albumin were monitored for the 3-month study period. Long-term follow-up data were also available for some of the study participants.

RESULTS

Fifteen dogs were eligible for enrollment over the study period. Twelve were enrolled, 10 remained in the study at 30 days, nine completed the 3-month study period. Following dietary alteration, eight of 10 dogs achieved complete remission, one dog achieved partial remission and one dog had no response. Seven of eight dogs achieving complete remission have remained in remission up to 4 years following study. In dogs with complete remission, median Canine Chronic Enteropathy Clinical Activity Index score was 11.5 and 4, and median serum albumin concentration was 15 g/L and 26 g/L at 0 and 14-28 days, respectively.

CLINICAL SIGNIFICANCE

Dogs with protein-losing enteropathy with previous lack of response to a combination of dietary therapies, glucocorticoids and immunosuppressive medications can achieve remission following a dietary change. Improvement is likely to be seen within 14 to 30 days. A change in dietary approach may be an alternative to further immunosuppression or anti-inflammatory strategies in some dogs with difficult to treat protein-losing enteropathy.

Successful treatment and long-term follow up of idiopathic immune-mediated polyarthritis with mycophenolate mofetil in a cat

Case summary

A 7-year-old neutered male Norwegian Forest Cat was presented with decreased appetite and activity, weight loss, fever, neutrophilia and hyperglobulinaemia. A physical examination showed painful stifle joints and enlarged popliteal lymph nodes. Blood examination showed neutrophilia, hyperglobulinaemia and increased serum amyloid A. Urinalysis, thoracic and abdominal radiographs, and abdominal ultrasonography were unremarkable. Synovial fluid from the knee joints had diminished viscosity and revealed neutrophilic inflammation on the smear. There was no evidence of infection in a microbiological culture of the synovial fluid. A diagnosis of idiopathic immune-mediated polyarthritis (IMPA) was made. Prednisolone was initiated at 2 mg/kg q24h PO and tapered with additional immunosuppressants (leflunomide, ciclosporin A and methotrexate); however, prednisolone could not be discontinued. Informed consent was obtained from the owner and mycophenolate mofetil (MMF) at a dosage of 10 mg/kg q12h PO was initiated on day 798. There were no adverse effects of MMF and prednisolone was discontinued on day 1183. Clinical signs resolved and the cat’s general condition remained stable with MMF alone at a dosage of 10 mg/kg q48h PO on day 1600.

Relevance and novel information

There is limited information describing feline IMPA and its treatment options other than the use of prednisolone. This is the first report of the successful treatment and long-term follow-up of feline IMPA with MMF. MMF may be a safe and effective option as an additional immunosuppressant in feline IMPA.

Ehrlichia canis in dogs experimentally infected, treated, and then immune suppressed during the acute or subclinical phases

Background

Concerns for recrudescence of Ehrlichia canis infection arise when immunosuppressive drugs are used to treat immune‐mediated diseases in dogs previously infected with E. canis.

Objectives

Determine whether administration of prednisolone and cyclosporine would reactivate E. canis infection in dogs previously treated with doxycycline during the acute or subclinical phases.

Animals

Seven beagles previously experimentally infected with E. canis and administered doxycycline for 4 weeks were included. Three of the 7 dogs were incidentally concurrently infected with Anaplasma platys and Babesia vogeli and were administered 2 doses of imidocarb 2 weeks apart before enrollment in the current study.

Methods

Experimental study. Each dog was administered prednisolone and cyclosporine for 6 weeks. Clinical signs, complete blood cell count (CBC), polymerase chain reaction (PCR) assays for E. canis, A. platys, and B. vogeli DNA in blood, E. canis indirect fluorescent antibodies (IFA) titers, and flow cytometry for antiplatelet antibodies were monitored.

Results

All dogs completed the immunosuppressive protocol. No evidence for recrudescence of E. canis, A. platys, or B. vogeli were detected based on clinical signs or results of CBC, PCR, IFA, and flow cytometry for antiplatelet antibodies. E. canis IFA titers were negative in 5/7 dogs at the end of immunosuppressive protocol and were negative 6 months after the protocol in 5/5 dogs available for testing.

Conclusions and Clinical Importance

Dogs administered with a 4‐week course of doxycycline with or without imidocarb failed to show evidence of activation of E. canis infection after administration of a commonly used immune suppressive protocol.

Comparison of the efficacy of cyclosporine and leflunomide in treating inflammatory colorectal polyps in miniature dachshunds

Inflammatory colorectal polyps (ICRPs) are frequently observed in miniature dachshunds in Japan and treated by prednisolone and immunosuppressive drugs such as cyclosporine and leflunomide. The purpose of this retrospective study was to compare the treatment efficacy, such as response rate, response interval, recurrence rate, and adverse events between cyclosporine and leflunomide. While the response rates were significantly higher in dogs treated with leflunomide, no significant differences were observed in the response interval or recurrence rate. Two of the 11 dogs treated with leflunomide showed hematological or gastrointestinal adverse events, while no dog treated with cyclosporine showed any adverse events. A case-controlled prospective study to compare the treatment efficacy of leflunomide with that of cyclosporine should be conducted.

Effects of cyclosporine on feline lymphocytes activated in vitro

Cyclosporine A (CsA) is a calcineurin inhibitor that is known to decrease lymphocyte expression of NFAT-regulated cytokines in humans, dogs and cats, and thereby depress lymphocyte function. Less is known about the effects of CsA on lymphocytes in cats than in other species. Peripheral blood mononuclear cells (PBMCs) were isolated from 6 healthy cats. PBMCs were exposed to i) no treatment, ii) 5 μg/ml concavalin A (ConA), iii) 500 ng/ml CsA and iv) 5 μg/ml ConA and 500 ng/ml CsA. The effects of CsA on cell proliferation were assessed via live and necrotic cell counts from day 1 to day 6. Additionally, flow cytometry was utilized to determine the effect of CsA on apoptosis in feline lymphocytes at day 1 and day 5. ConA exposure resulted in increases in cell counts from day 1 to 6, peaking at day 5. CsA inhibited cell proliferation, indicated via decreased live lymphocyte cell counts in the cell cultures exposed to ConA and CsA, compared to the cell cultures exposed to ConA only. Furthermore, CsA induced early and late apoptotic changes in feline PBMCs. Differences in these responses may influence an individual cat's response to cyclosporine therapy.

Pharmacokinetics of mycophenolic acid and its effect on CD4+ and CD8+ T cells after oral administration of mycophenolate mofetil to healthy cats

Background

Mycophenolate mofetil (MMF) is an immunosuppressant used in human and veterinary medicine. Little pharmacokinetic and pharmacodynamic information on MMF is available in cats.

Objective

To evaluate the plasma disposition of mycophenolic acid (MPA) and assess its effect on total peripheral blood mononuclear cells and CD4⁺/CD8⁺ ratios after PO administration of MMF.

Animals

Healthy cats (n = 10).

Methods

Mycophenolate mofetil was administered at a dosage of 10 mg/kg q12h (n = 3), 15 mg/kg q12h (n = 3), and 15 mg/kg q8h (n = 4) for 7 days. Concentrations of MPA and derivatives were determined using ultra‐high‐performance liquid chromatography. Flow cytometry was used to assess CD4⁺/CD8⁺ T‐cell ratios.

Results

All cats biotransformed MMF into MPA. Half of the cats (5/10) had adverse effects within 1 week of MMF administration. Area under the curve limit of quantification (AUC_0‐LOQh) of MPA ranged from 1.27 to 2.03 hours·μg/mL and from 1.77 to 8.54 hours·μg/mL after the first and last PO dose of 10 mg/kg. The AUC_0‐loqh of MPA ranged from 2.18 to 31 hours·μg/mL after the first dose of 15 mg/kg of MMF. Before the first dose of MMF, the average total number of PBMC ranged from 1.2 to 9.3 million/mL. At the last dose of MMF, the average total number of PBMC ranged from 3 to 5 million/mL.

Conclusion

Mycophenolic acid was detected in all cats. The dose 10 mg/kg given q12h for 1 week was tolerated (n = 3). The efficacy of MMF as an immunosuppressant and long‐term safety in cats of this dosage regimen is unknown.

Comparative pathophysiology and management of protein-losing enteropathy

Protein‐losing enteropathy, or PLE, is not a disease but a syndrome that develops in numerous disease states of differing etiologies and often involving the lymphatic system, such as lymphangiectasia and lymphangitis in dogs. The pathophysiology of lymphatic disease is incompletely understood, and the disease is challenging to manage. Understanding of PLE mechanisms requires knowledge of lymphatic system structure and function, which are reviewed here. The mechanisms of enteric protein loss in PLE are identical in dogs and people, irrespective of the underlying cause. In people, PLE is usually associated with primary intestinal lymphangiectasia, suspected to arise from genetic susceptibility, or “idiopathic” lymphatic vascular obstruction. In dogs, PLE is most often a feature of inflammatory bowel disease (IBD), and less frequently intestinal lymphangiectasia, although it is not proven which process is the true driving defect. In cats, PLE is relatively rare. Review of the veterinary literature (1977‐2018) reveals that PLE was life‐ending in 54.2% of dogs compared to published disease‐associated deaths in IBD of <20%, implying that PLE is not merely a continuum of IBD spectrum pathophysiology. In people, diet is the cornerstone of management, whereas dogs are often treated with immunosuppression for causes of PLE including lymphangiectasia, lymphangitis, and crypt disease. Currently, however, there is no scientific, extrapolated, or evidence‐based support for an autoimmune or immune‐mediated mechanism. Moreover, people with PLE have disease‐associated loss of immune function, including lymphopenia, severe CD4+ T‐cell depletion, and negative vaccinal titers. Comparison of PLE in people and dogs is undertaken here, and theories in treatment of PLE are presented.

Pharmacokinetics and pharmacodynamics of mycophenolic acid in healthy cats after twice-daily intravenous infusion of mycophenolate mofetil for three days

OBJECTIVE To evaluate the plasma disposition of mycophenolic acid (MPA) and its derivatives MPA glucuronide and MPA glucoside after twice-daily infusions of mycophenolate mofetil (MMF) in healthy cats for 3 days and to assess the effect of MMF administration on peripheral blood mononuclear cell (PBMC) counts and CD4⁺-to-CD8⁺ ratios. ANIMALS 5 healthy adult cats. PROCEDURES MMF was administered to each cat (10 mg/kg, IV, q 12 h for 3 days). Each dose of MMF was diluted with 5% dextrose in water and then administered over a 2-hour period with a syringe pump. Blood samples were collected for analysis. A chromatographic method was used to quantitate concentrations of MPA and its metabolites. Effects of MMF on PBMC counts and CD4⁺-to-CD8⁺ ratios were assessed by use of flow cytometry. RESULTS All cats biotransformed MMF into MPA. The MPA area under the plasma concentration-time curve from 0 to 14 hours ranged from 14.6 to 37.6 mg·h/L and from 14.4 to 22.3 mg·h/L after the first and last infusion, respectively. Total number of PBMCs was reduced in 4 of 5 cats (mean ± SD reduction, 25.9 ± 15.8% and 26.7 ± 19.3%) at 24 and 48 hours after the end of the first infusion of MMF, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Plasma disposition of MPA after twice-daily IV infusions for 3 days was variable in all cats. There were no remarkable changes in PBMC counts and CD4⁺-to-CD8⁺ ratios.

Treatment Outcome of 22 Dogs With Masticatory Muscle Myositis (1999-2015)

Medical records of dogs diagnosed with masticatory muscle myositis (MMM) at Ryan Veterinary Hospital of the University of Pennsylvania during a period of 17 years (from 1999 to 2015) were reviewed. Twenty-two dogs were included in this retrospective case series study. Immunosuppressive doses of prednisone were prescribed to all dogs. Twenty dogs had full recovery of masticatory function. The mean (SD) improvement in the vertical mandibular range of motion (vmROM) was 5.3 (3.1) cm during the first 4 weeks of treatment (weeks 1-4) and 2.8 (2.2) cm during the subsequent 8 weeks (weeks 5-12). The vmROM continued to improve for several more months. Six dogs had a relapse, but the clinical signs were more severe in dogs when no longer receiving prednisone compared to dogs still on prednisone at the time of relapse. When diagnosed and treated appropriately, MMM has a good prognosis with relatively quick return to masticatory function. Early discontinuation of prednisone therapy should be avoided. Approximately 1 year of therapy is recommended prior to discontinuing the medication. Educating the client about how to perform muscle palpation, determine vmROM at home, recognize signs of pain, and notice behavioral changes may help in the early detection of relapses.

Mycophenolic acid in patients with immune-mediated inflammatory diseases: From humans to dogs

Mycophenolic acid (MPA), a noncompetitive, selective and reversible inhibitor of inosine 5'-monophosphate dehydrogenase (IMPDH), is an immunosuppressive agent that has a long history in medicine. Mechanistically, the inhibition of IMPDH leads to the selective and eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil (MMF), the first MPA-based product to receive marketing approval over two decades ago, was originally indicated for the prophylaxis of organ rejection in human transplant patients. Given its broad immunosuppressive properties and ability to selectively inhibit lymphocyte division and effector functions, the clinical utility of MPA was subsequently explored in a host of autoimmune diseases. Human clinical studies have shown MPA to be safe and effective and support its off-label administration for immune-mediated diseases such as lupus, myasthenia gravis and atopic dermatitis. MMF became generically available in the United States in 2008, and its clinical utility is increasingly being explored as a treatment option for dogs with immune-mediated diseases. This review summarizes the available literature for MPA pharmacokinetics and pharmacodynamics, and the current status of MPA as a treatment for client-owned dogs diagnosed with immune-mediated diseases.

The evaluation of three treatment protocols using oral prednisone and oral meloxicam for therapy of canine idiopathic lymphoplasmacytic rhinitis: a pilot study

Background

Idiopathic lymphoplasmacytic rhinitis (LPR) is a common inflammatory disorder of the nasal cavity in dogs due to unknown etiology. It is characterised by non-specific clinical signs, including nasal discharge, epistaxis and breathing problems. Diagnosis is usually based on the histopathologic identification of infiltrating plasmocytes and lymphocytes in the nasal mucosa and the exclusion of other underlying diseases. Treatment strategies include glucocorticoids, non-steroidal anti-inflammatory drugs, antibiotics and antifungal medications. The aim of this study was to evaluate the efficacy of various therapeutic protocols for managing canine lymphoplasmacytic rhinitis based on the results of clinical, endoscopic and histological examinations, and to determine the relapse rate for LPR in dogs.

Twenty dogs of different breeds and both sexes, aged 1 to 14 years, were divided into four groups, each consisting of five dogs, including three experimental groups diagnosed with LPR and a control group.

The dogs from the first experimental group were administered prednisone orally at 1 mg/kg/day in the first 4 weeks and 0,5 mg/kg/day in the following 2 weeks. The second group of dogs was administered meloxicam orally at 0,1 mg/kg/day in the first 3 weeks, followed by prednisone at 1 mg/kg/day in the following 2 weeks and 0,5 mg/kg/day in the last week of the treatment. The dogs from the third experimental group were administered meloxicam orally at 0,1 mg/kg/day for 6 weeks. The control group of dogs was administered empty gelatin capsules (placebo) orally for 6 weeks. Clinical signs, endoscopic and histopathologic lesions were scored before and after treatment. Groups were compared using Chi- squared statistics in a 2 × 2 table for pre- versus post-treatment scores.

Results

Clinical signs persisted in the group treated with meloxicam and were mostly resolved in prednisone-treated dogs. However, endoscopic and histological changes were still observed in these two groups after treatment. The severity of all diagnostic features was reduced in the group treated with meloxicam for 3 weeks followed by prednisone for 3 weeks. The significant differences (p < 0.05) were noted between experimental and control groups. The dogs showed a statistically significant reduction in characteristics of the LPR before and after treatment, as measured by clinical signs (Group 1vs.4 p = 0.00, group 2 vs 4 p = 0.00, group 3 vs 4 p = 0,01), by endoscopy (1 vs 4 p = 0,01, 2 vs 4 p = 0,00, 3 vs 4 p = 0,03), and by histopathology (groups 1 vs 4 p = 0,00, 2 vs 4 p = 0,00, 3 vs 4 p = 0,03). The significant differences were noted between experimental groups, as measured by endoscopy (group 2vs 3 p = 0,04), and by relapse rate (groups 1 and 2 p = 0,03, groups 2 and 3 p = 0,01).

Conclusions

The three treatment protocols administered to dogs improved clinical, endoscopic and histological status. However, oral administration of meloxicam for 3 weeks, followed by prednisone for 3 weeks, appeared to be the most successful treatment. These patients remained asymptomatic for 6 months.

Pharmacokinetics of Mycophenolic Acid after Intravenous Administration of Mycophenolate Mofetil to Healthy Cats

Background

Mycophenolate mofetil (MMF), the prodrug of mycophenolic acid (MPA), is becoming increasingly popular as an alternative immunosuppressant in feline medicine. Pharmacokinetic information is not available for cats.

Objective

The purpose of this study was to determine whether MMF is biotransformed into the active metabolite MPA and to evaluate the disposition of MPA after a 2‐hour constant rate intravenous (IV) infusion of MMF in healthy cats.

Animals

Healthy cats (n = 6).

Methods

This was a prospective pilot study. All cats were administered MMF at 20 mg/kg every 12 hours over a 2‐hour constant rate infusion for 1 day. The concentrations of MPA and its derivatives in blood were determined using a validated UHPLC–UV method.

Results

All cats biotransformed MMF into MPA. The mean AUC_0‐14 h ranged from 6 to 50 h*mg/L after IV dosing of MMF. Transient large bowel diarrhea was recorded in 2 of 6 cats after medication administration.

Conclusion and Clinical Importance

The disposition of MPA in plasma was highly variable, which could result in high interindividual variability in the safety and efficacy of treatment with MMF in cats.

Pharmacokinetics and dynamics of mycophenolate mofetil after single-dose oral administration in juvenile dachshunds

Mycophenolate mofetil (MMF) is recommended as an alternative/complementary immunosuppressant. Pharmacokinetic and dynamic effects of MMF are unknown in young-aged dogs. We investigated the pharmacokinetics and pharmacodynamics of single oral dose MMF metabolite, mycophenolic acid (MPA), in healthy juvenile dogs purpose-bred for the tripeptidyl peptidase 1 gene (TPP1) mutation. The dogs were heterozygous for the mutation (nonaffected carriers). Six dogs received 13 mg/kg oral MMF and two placebo. Pharmacokinetic parameters derived from plasma MPA were evaluated. Whole-blood mitogen-stimulated T-cell proliferation was determined using a flow cytometric assay. Plasma MPA C_max (mean ± SD, 9.33 ± 7.04 μg/ml) occurred at <1 hr. The AUC_0-∞ (mean ± SD, 12.84±6.62 hr*μg/ml), MRT_inf (mean ± SD, 11.09 ± 9.63 min), T1/2 (harmonic mean ± PseudoSD 5.50 ± 3.80 min), and k/d (mean ± SD, 0.002 ± 0.001 1/min). Significant differences could not be detected between % inhibition of proliferating CD5+ T lymphocytes at any time point (p = .380). No relationship was observed between MPA concentration and % inhibition of proliferating CD5+ T lymphocytes (R = .148, p = .324). Pharmacodynamics do not support the use of MMF in juvenile dogs at the administered dose based on existing therapeutic targets.

Anti-thymocyte serum as part of an immunosuppressive regimen in treating haematological immune-mediated diseases in dogs

OBJECTIVES

To report the outcomes associated with the use of rabbit anti-dog thymocyte serum in dogs with haematological immune-mediated diseases.

METHODS

Medical records from 2000 to 2016 of patients diagnosed with immune-mediated haemolytic anaemia, immune-mediated thrombocytopenia, pancytopenia and myelofibrosis were reviewed. All dogs had a severe or refractory disease and received rabbit anti-dog thymocyte serum. Lymphocyte counts were used to monitor the immediate anti-thymocyte effect of therapy; long-term patient outcome was recorded.

RESULTS

A total of 10 dogs were included. All dogs except one had a notable decrease in their lymphocyte count after rabbit anti-dog thymocyte serum; four of nine had a decrease to less than 10% of the initial lymphocyte count and one dog reached 10·8%. All dogs were discharged from the hospital following their treatment. The dog with no alteration of lymphocyte count following therapy with rabbit anti-dog thymocyte serum had refractory immune mediated haemolytic anemia and was euthanised within two weeks. All other cases achieved clinical remission with immunosuppressive therapy eventually being tapered (3 of 10) or discontinued (6 of 10).

CLINICAL SIGNIFICANCE

Rabbit anti-dog thymocyte serum therapy might be of interest as an adjunctive therapy in refractory immune-mediated diseases and suppressed lymphocyte counts in most dogs.

Acquired Fanconi syndrome in four cats treated with chlorambucil

CASE SERIES SUMMARY

Fanconi syndrome (FS) is well described in humans and dogs, but has not been reported in cats. This case series describes four cats with acquired FS. On the basis of clinical signs and intestinal biopsies, all cats were initially diagnosed with alimentary lymphoma or inflammatory bowel disease. Treatment with chlorambucil and corticosteroids was started at standard doses, based on published protocols. Within 2-26 months of the start of treatment, glucosuria, despite normoglycemia, was identified incidentally on routine biochemical screening; FS was diagnosed with urine metabolic assays, confirming aminoaciduria and glucosuria in all four cases. Neither polyuria nor polydipsia were noted in any case, and only 1/4 cats had any clinical signs at the time of diagnosis. Partial or complete resolution of FS was seen in 3/4 cases within 3 months of discontinuing chlorambucil therapy.

RELEVANCE AND NOVEL INFORMATION

This is the first case series to document acquired FS in the cat, and the first to suggest a possible association between chlorambucil and acquired FS. Cats treated with chlorambucil should be monitored for the development of glucosuria, and discontinuation of chlorambucil should be considered if FS is identified. Further study into the association between chlorambucil and acquired FS in cats is warranted.

The transferability from rat subacute 4-week oral toxicity study to translational research exemplified by two pharmaceutical immunosuppressants and two environmental pollutants with immunomodulating properties

Exposure to chemicals may have an influence on the immune system. Often, this is an unwanted effect but in some pharmaceuticals, it is the intended mechanism of action. Immune function tests and in depth histopathological investigations of immune organs were integrated in rodent toxicity studies performed according to an extended OECD test guideline 407 protocol. Exemplified by two immunosuppressive drugs, azathioprine and cyclosporine A, and two environmental chemicals, hexachlorobenzene and benzo[a]pyrene, results of subacute rat studies were compared to knowledge in other species particular in humans. Although immune function has a high concordance in mammalian species, regarding the transferability from rodents to humans various factors have to be taken into account. In rats, sensitivity seems to depend on factors such as strain, sex, stress levels as well as metabolism. The two immunosuppressive drugs showed a high similarity of effects in animals and humans as the immune system was the most sensitive target in both. Hexachlorobenzene gave an inconsistent pattern of effects when considering the immune system of different species. In some species pronounced inflammation was observed, whereas in primates liver toxicity seemed more obvious. Generally, the immune system was not the most sensitive target in hexachlorobenzene-treatment. Immune function tests in rats gave evidence of a reaction to systemic inflammation rather than a direct impact on immune cells. Data from humans are likewise equivocal. In the case of benzo[a]pyrene, the immune system was the most sensitive target in rats. In the in vitro plaque forming cell assay (Mishell-Dutton culture) a direct comparison of cells from different species including rat and human was possible and showed similar reactions. The doses in the rat study had, however, no realistic relation to human exposure, which occurs exclusively in mixtures and in a much lower range. In summary, a case by case approach is necessary when testing immunotoxicity. Improvements for the translation from animals to humans related to immune cells can be expected from in vitro tests which offer direct comparison with reactions of human immune cells. This may lead to a better understanding of results and variations seen in animal studies.

Inflammatory joint disease in cats

Practical relevance:

Osteoarthritis, a degenerative non-inflammatory joint disease, is common in cats, usually causing gradual changes in behavior and lifestyle rather than severe lameness. Inflammatory arthritis occurs much less frequently and is nearly always associated with debilitating lameness. It may have an infectious or immune-mediated cause – but, unlike the canine disease, is much more likely to be infectious in origin.

Clinical challenges:

Cats with inflammatory joint disease are presented for evaluation of lethargy, anorexia, reluctance to walk or fever. Synovial fluid collection and analysis is required to confirm joint inflammation, but this is a procedure many veterinarians are not comfortable performing in cats. Once inflammatory arthritis is confirmed, extensive testing is required to diagnose infectious causes and determine appropriate treatment. Immune-mediated polyarthritis can be treated with immunosuppressive drugs only after all infectious possibilities are eliminated. Radiographs are used to characterize the arthritis as erosive or nonerosive, but radiographic changes in cats are often subtle compared with those described in canine rheumatoid-like arthritis.

Audience:

This review, aimed at all veterinarians who treat cats, describes the general clinical approach to feline joint disease, the collection and analysis of synovial fluid, and the diagnosis and management of inflammatory joint diseases affecting cats. The diagnostic approach to an unusual case of erosive polyarthritis is discussed in the Case Notes.

Evidence base:

To date, the veterinary literature on inflammatory joint disease in cats has been limited to older reviews of immune-mediated disorders and multiple single case reports or small case series describing infectious disorders. This article offers a current comprehensive review of these disorders.