Immunotherapy In Dogs Research Articles

Translational History and Hope of Immunotherapy of Canine Tumors.

Companion dogs have served an important role in cancer immunotherapy research. Sharing similar environments and diets with humans, dogs naturally develop many of the same cancers. These shared exposures, coupled with dogs' diverse genetic makeup, make them ideal subjects for studying cancer therapies. Tumors like osteosarcoma, hemangiosarcoma, soft-tissue sarcoma, and non-Hodgkin lymphoma occur with greater frequency than their counterpart disease in humans. Canine brain tumors allow the study of therapy strategies with imaging, surgery, and radiotherapy equipment in veterinary patients with near-human geometry. Nonspecific immunostimulants, autologous and allogeneic vaccines, immune checkpoint inhibitors, and cellular therapies used in treating canine cancers have been tested in veterinary clinical trials. These treatments have not only improved outcomes for dogs but have also provided valuable insights for human cancer treatment. Advancements in radiation technology and the development of tools to characterize canine immune responses have further facilitated the ability to translate veterinary clinical trial results to human applications. Advancements in immunotherapy of canine tumors have directly supported translation to human clinical trials leading to approved therapies for patients with cancer around the world. The study of immunotherapy in dogs has been and will continue to be a promising avenue for advancing human cancer treatment.

Preclinical evaluation and first-in-dog clinical trials of PBMC-expanded natural killer cells for adoptive immunotherapy in dogs with cancer

BackgroundNatural killer (NK) cells are cytotoxic cells capable of recognizing heterogeneous cancer targets without prior sensitization, making them promising prospects for use in cellular immunotherapy. Companion dogs develop spontaneous cancers...

A randomised, double-blinded trial to assess the effect of oclacitinib and prednisolone on intradermal allergen and prick tests in dogs with atopic dermatitis.

Intradermal (IDT) and prick (PT) tests are used to select allergens for allergen-specific immunotherapy in dogs with atopic dermatitis (cAD). However, the use of antipruritic drugs before performing these tests may influence the results. To evaluate the influence of the drugs oclacitinib and prednisolone on the immediate-phase reactions of IDT and PT. Thirty client-owned dogs with cAD with positive reactions to at least one allergen extract on IDT or PT. Dogs were randomly assigned to receive oclacitinib 0.4-0.58 mg/kg per os, every 12 h (n = 14), or prednisolone 0.37-0.65 mg/kg p.o., every 12 h (n = 16) for 14 days. IDT and PT were performed on Day (D)0 before treatment and on D14. At D14 there was no significant reduction in the means of the orthogonal diameters of the positive immediate-phase reactions of the IDT (p = 0.064) in the oclacitinib group; however, in the PT, the diameter of the positive reactions reduced significantly (p = 0.048). In both tests, there was no significant reduction in the total number of positive reactions (IDT, p > 0.999; PT, p = 0.735). In the prednisolone group, the means of the orthogonal diameters of positive immediate-phase reactions were significantly reduced in both tests (IDT, p = 0.001; PT, p ≤ 0.001) and there also was a reduction in the total number of positive reactions (IDT, p = 0.022; PT, p = 0.001). The use of oclacitinib 0.4-0.58 mg/kg twice daily for 14 days does not interfere with IDT results in dogs with cAD. However, oclacitinib may reduce PT reactivity. The use of prednisolone 0.37-0.65 mg/kg twice daily results in a reduction in both IDT and PT results.

Hymenoptera Venom Immunotherapy in Dogs: Safety and Clinical Efficacy.

Hymenoptera allergens are the main triggers for anaphylaxis in susceptible dogs and humans. Hymenoptera venom specific immunotherapy (VIT), the only disease-modifying treatment, has the potential to prevent future life-threatening reactions in human patients. Prospective clinical data on VIT efficacy in dogs are currently lacking. Therefore, the aim of this study was to show that VIT is not only safe but also efficacious in preventing anaphylaxis in dogs allergic to Hymenoptera. This uncontrolled prospective clinical trial included 10 client-owned dogs with a history of anaphylaxis following repeated Hymenoptera stings. The sensitization to bee and wasp allergens was demonstrated by intradermal testing (IDT) and allergen-specific IgE serology. For VIT induction (induction phase), dogs received a shortened rush immunotherapy protocol with aqueous allergens, which was then followed by monthly injections of 100 µg of alum-precipitated allergen (maintenance phase). VIT efficacy was determined by observing patients' clinical reactions to re-stings. No systemic adverse events were seen during the induction and maintenance phases. From the seven re-stung dogs, only one developed a mild angioedema at the site of the sting; the remaining dogs were asymptomatic. These results show that VIT represents a safe and effective treatment option for Hymenoptera-allergic dogs.

Modified rush venom immunotherapy in dogs with Hymenoptera hypersensitivity.

Hymenoptera envenomation occurs frequently in people and dogs and can trigger anaphylaxis. Venom immunotherapy (VIT) is the only preventive treatment for Hymenoptera hypersensitivity and is indicated for people with severe adverse reactions to insect stings. Rush VIT is an accelerated VIT protocol in people. This has not been reported in dogs. The objective of the study was to evaluate the safety of modified rush VIT. Twenty client-owned dogs with Hymenoptera hypersensitivity based on a history of adverse reactions to Hymenoptera envenomation and a positive intradermal test to honey bee and/or paper wasp venom. Dogs received incremental doses of venom via subcutaneous injection one day per week for three consecutive weeks until the maintenance dose was achieved. Vital signs were recorded every 30 min prior to venom administration. Adverse reactions were categorised as localised or grade I-IV systemic reactions. Nineteen of 20 dogs (95%) completed rush VIT. One dog experienced a grade III systemic adverse reaction and was withdrawn from the study. No adverse reactions occurred in 10 of 20 dogs (50%). Localised and grade I-II systemic reactions occurred in nine of 20 dogs (45%), including nausea (n = 5), injection site pruritus (n = 3) and diarrhoea and lethargy (n = 1). Modified rush VIT in dogs was well-tolerated and should be considered for dogs with Hymenoptera hypersensitivity. Larger studies are needed to evaluate the efficacy of VIT in dogs for preventing hypersensitivity reactions to insect stings.

Clinical Implications of Immune Checkpoints and the RANK/RANK-L Signaling Pathway in High-Grade Canine Mast Cell Tumors.

Mast cell tumors (MCTs) are the most common malignant cutaneous tumors in dogs, and they present extremely variable biological behavior. The interaction between RANK, RANK-L, and immune checkpoints is frequently detected in the tumor microenvironment, and, together, they participate in every stage of cancer development. Thus, the aim of this study was to characterize the molecular profiles of PD-L1, CTLA-4, RANK/RANK-L signaling pathway, and IFN-γ in primary tumors and lymph node metastases. Formalin-fixed, paraffin-embedded slides of MCTs and metastatic lymph nodes of ten dogs were submitted to immunohistochemical investigations. The results demonstrated that the tumor microenvironment of the high-grade mast cell tumors showed moderate or intense immunolabeling of all proteins, and the lymph node metastases also showed moderate or intense immunolabeling of checkpoint proteins. In addition, MCTs larger than 3 cm were associated with intensified PD-L1 (p = 0.03) in metastatic lymph nodes and RANK-L (p = 0.049) immunoreactivity in the tumor. Furthermore, dogs with a survival time of less than 6 months showed higher PD-L1 immunoreactivity (p = 0.042). In conclusion, high-grade MCT is associated with an immunosuppressive microenvironment that exhibits elevated RANK/RANK-L signaling and enhanced immune checkpoint immunoreactivity, potentially facilitating intratumorally immune escape. These biomarkers show promise as clinical indicators of disease progression and might response to immunotherapy in dogs with high-grade MCTs, thus emphasizing their importance for guiding treatment decisions and improving outcomes.

A systematic review of allergen immunotherapy, a successful therapy for canine atopic dermatitis and feline atopic skin syndrome.

Canine atopic dermatitis and feline atopic skin syndrome are common presentations in small animal practice. Numerous drugs are used for symptomatic therapy. The only definitive treatment based on the cause of the disease is allergen immunotherapy. Classical allergen immunotherapy (AIT) consists of subcutaneous injections of an extract containing offending allergens, with increasing doses and allergen concentrations at short intervals during the induction phase of several weeks to months followed by a maintenance phase, where a fixed dose is typically given at longer intervals. Dose and interval are tailored to the individual patient. Newer types of AIT include rush immunotherapy, where the induction phase is abbreviated, intralymphatic immunotherapy, and oromucosal or sublingual immunotherapy. AIT aims at inducing a regulatory T-cell response and subsequently downregulating the exaggerated immune response to offending allergens leading to clinical signs. This article reviews the published knowledge about allergen immunotherapy in dogs and cats for small animal practitioners.

Effective immuno-therapeutic treatment of Canine Leishmaniasis.

Canine Leishmaniasis (CanL) caused by the L. infantum species is one of the biggest threats to the health of the South American canine population. Chemotherapeutics currently used for the treatment of CanL fail to induce a total parasite clearance while inducing numerous side effects. As CanL is an immunomodulated disease, the use of immuno-treatments should strengthen the deficient immune response of infected dogs. In this study, we evaluated a nasally administered immunotherapy in dogs naturally infected with L. infantum (stage 2), with both visceral and cutaneous manifestations. Noteworthy, some of them were also infected by other parasites (E. canis, D. immitis, A. platys), what worsen their chance of survival. The treatment was based on 2 intranasal (IN.) administrations of a killed L. infantum parasite loaded into maltodextrin nanoparticles, which treatment was compared with the classical oral administration of Miltefosine (2 mg/kg) for 28 days, as well as a combination of these 2 treatments. The results showed that two IN administrations significantly reduced the serology, and were at least as efficient as the chemotherapy to reduce the skin and bone marrow parasite burden, as well as clinical scores, and that unlike Miltefosine treatments, this nasally administered nanoparticle vaccine was without side effects. These results confirm the feasibility of a simple therapeutic immuno-treatment against L. infantum infected dogs, which is a promising tool for future developments.

Single cell and genomic profiling of PBMC-expanded NK cells in first-in-dog clinical trial of allogeneic adoptive NK cell therapy for dogs with cancer

Abstract Natural killer (NK) cells are innate cytotoxic cells with a crucial role in anti-tumor responses, making them a promising candidate for adoptive immunotherapy (IT). CD5 depletion was previously used to isolate CD5 dim-expressing NK cells as a source of expanded NK cells for IT, but this technique can limit the yield of the final NK product. Here, we used bulk and single cell (SC) sequencing to compare ex vivo culture conditions using standard CD5 depletion versus unmanipulated PBMCs as the source of expanded NK cells comparing transcriptomic profiles from 5 matched healthy beagle donors using both techniques and subsequently from 5 dogs with naturally occurring malignant melanoma who received allogeneic PBMC-expanded NK cells in a first-in-dog clinical trial. Notably, beagle-derived PBMC-expanded cells had upregulation of NK pathways related to activation and function compared to CD5 depleted cells, suggesting bulk PBMCs may yield a superior product. Clinically, there were no serious adverse events using PBMC-expanded allogeneic NK cells, and one dog survived 445 days post-treatment, suggesting possible clinical benefit. SC analysis of PBMCs from this dog before, during, and after treatment showed a robust NK cell population across timepoints with high expression of cytotoxicity-related genes, such as GZMB and NCR3, lasting 14 days post-NK transfer. SC data also suggested a previously uncharacterized concordance of NK and CD8 T cell gene expression profiles in canine peripheral blood. Overall, allogeneic NK transfer using PBMC-expanded NK cells appears promising in dogs with cancer, and pre-clinical and clinical data support the use of SC analysis as a valuable technique for biomarker identification and optimizing NK IT in dogs. This study was funded by the National Institutes of Health/National Cancer Institute grant U01 CA224166-01, the 3U01CA224166-02S1 and 5R03CA252793-02 grants, and the V Foundation Victory over Cancer through the Canter Laboratory. Student support was provided by the AVMA/AVMF 2nd Opportunity Summer Research Scholarship.

Single cell RNA sequencing analysis of tumor responses to triple drug oral immunotherapy in dogs with osteosarcoma

Abstract Osteosarcoma constitutes a rare childhood cancer that is associated with dismal outcomes. As such, there is a need to develop non-invasive immunotherapeutic approaches to treat this aggressive malignancy. To address this need, we described the cellular heterogeneity in spontaneously occurring canine osteosarcoma tumors then evaluated how treatment with adjuvant immunotherapy altered the tumor microenvironment. We investigated the effects of a triple drug immunotherapeutic (orally administered losartan, ladarixin, and toceranib) that was designed to deplete immune suppressive macrophages and promote antitumor immunity. The treated cohort of dogs were given the adjuvant immunotherapy for 14 days prior to amputation, while naïve samples were collected from unrelated dogs undergoing amputation to treat a primary osteosarcoma tumor. In total, we completed single cell RNA sequencing on 6 naïve dogs and 6 treated dogs to profile just under 100,000 cells. Unsupervised clustering revealed 30 unique cell populations with T cells, macrophages, and neutrophils making up the majority of immune infiltrates. Evaluation of changes to the cellular proportions following treatment revealed a marked reduction in macrophages, which suggests the combination immunotherapy was able to alter the tumor microenvironment. Overall, this study provides unique insights into the heterogeneity within canine osteosarcoma tumors and highlights the impacts of adjuvant immunotherapy on tumor infiltrating immune cell transcriptional programs. T32 OD012201 U01 CA5341458 Shipley family foundation

Chronic adrenergic stress and generation of myeloid-derived suppressor cells: Implications for cancer immunotherapy in dogs.

Recent studies have highlighted a key role played by the sympathetic nervous system (SNS) and adrenergic stress in mediating immune suppression associated with chronic inflammation in cancer and other diseases. The connection between chronic SNS activation, adrenergic stress and immune suppression is linked in part to the ability of catecholamines to stimulate the bone marrow release and differentiation of myeloid-derived suppressor cells (MDSC). Rodent model studies have revealed an important role for β-adrenergic receptor signalling in suppression of cancer immunity in mice subjected to chronic stresses, including thermal stress. Importantly, therapeutic blockade of beta-adrenergic responses by drugs such as propranolol can partially reverse the generation and differentiation of MDSC, and partly restore tumour immunity. Clinical trials in both humans and dogs with cancer have demonstrated that propranolol blockade can improve responses to radiation therapy, cancer vaccines and immune checkpoint inhibitors. Thus, the SNS stress response has become an important new target to relieve immune suppression in cancer and other chronic inflammatory conditions.

Immunological mechanisms involved in the human response to a dog dander allergoid

BackgroundDog allergens are a common cause of allergic sensitisation and trigger respiratory symptoms worldwide. However, clinical evidence regarding dog immunotherapy is limited. Therefore, the aim of this study was to analyse the immunomodulatory properties of a new allergoid from dog dander, thereby deepening the understanding of the molecular mechanisms involved in the reestablishment of the tolerogenic response. MethodsThree independent batches of dog dander native and allergoid allergen extracts were manufactured and characterised. Allergenic profiles were analysed by the identification of all dog allergens and quantification of the major allergens Can f 1 and Can f 5. The allergenicity profile of the allergoid was studied using biological potency and basophil activation tests. In vitro immunomodulatory parameters was evaluated as the capacity of the allergoid to induce IgG antibodies that block IgE binding to the allergen and cytokine promotion (IFN-γ, IL-4, IL-6, IL-10, IL-13, and TNF-α) in PBMCs from allergic donors. ResultsThe presence of all dog allergens, including Can f 1 and Can f 5, was confirmed in both types of extracts. The new allergoid showed a low IgE binding capacity, which significantly affected the activation of effector cells, such as basophils. The IgG antibodies induced by the allergoid in rabbits blocked human IgE binding epitopes on the dog native extract and induced Th1 and Treg responses by increasing IFN-γ and IL-10 levels in PBMCs from allergic donors. ConclusionThis new dog dander allergoid containing Can f 1 and Can f 5 showed a low capacity to bind IgE and to activate basophils in dog allergic patients. Furthermore, it showed potent activation of Th1 mediators and induction of tolerance through Treg activation. This allergoid could offer a safer profile than the native extract and could be an effective immunotherapy treatment for dog allergic patients.

Immunological mechanisms involved in dog dander allergoid response

Dog allergens cause allergic sensitisation and trigger respiratory symptoms worldwide. However, clinical evidence regarding dog immunotherapy is limited. The aim of this study was to analyse the immunologic parameters that depict the in vitro safety and efficacy profile of a new allergoid of dog dander.

Determination of the efficacy rate and time-to-efficacy of subcutaneous immunotherapy in dogs with atopic dermatitis.

Allergen-specific immunotherapy (ASIT) is reported to have a success rate of 50-70% when given for up to 12 months to dogs with atopic dermatitis (AD). How soon ASIT is clinically effective is unclear. To compare the efficacy rate (ER) and time-to-efficacy (TTE) of various types of subcutaneous immunotherapy (SCIT) administered using conventional dosing regimens using the methodology of a critically appraised topic. Three databases were searched to extract information on the ER and TTE of SCIT in dogs with AD. Herein, "efficacy" was defined as a ≥50% reduction in pruritus and/or skin lesions, and the TTE as the time needed to achieve such a reduction. We selected 12 publications including 194 dogs. The ER was significantly higher with the polymerised allergoids coupled with nonoxidized mannan than for the "classic" aqueous and alum-precipitated SCIT types. A TTE of three months or shorter was seen in a significantly higher proportion of dogs receiving mannan-couple allergoids, pullulan-conjugated Der f 2 or tyrosine-adjuvanted than aqueous or alum-precipitated SCIT; with the latter two formulations, the TTE might be nine months or longer in ≤20% of atopic dogs. In spite of the low number of articles available for review and small number of enrolled dogs, novel SCIT regimens appear to have a faster - and possibly higher - efficacy than the currently available aqueous or alum-precipitated formulations. A standardisation of outcome measures for ASIT clearly is needed to allow a more meaningful comparison between SCIT types.

Safety analysis ofex vivo-expanded canine natural killer cells in a xenogeneic mouse model of graft-versus-host disease

Canine natural killer (NK) cells are large, granular lymphocytes that are neither B lymphocytes nor T lymphocytes. However, it has been reported that canine NK cells share some of the phenotypic characteristics of T lymphocytes, such as CD3 and CD5. Studies are needed to assess the safety of canine NK cells for immunotherapy, especially because the safety of using allogeneic NK cells as an immunotherapy for dogs has yet to be shown. In this study, the safety of cultured canine NK cells was assessed using a xenogeneic mouse model of graft-versus-host disease (GVHD). Mice were injected with either canine peripheral blood mononuclear cells (PBMCs) or cultured NK cells for 2 or 3 weeks. Data were then collected on changes in mice body weights, disease severity scores, and survival rates. Histopathological and immunohistochemical evaluations were also performed. All mice injected with canine PBMCs died within 45 days after injection. Severe clinical signs were caused by GVHD. The histopathological and immunohistochemical evaluations showed that mice injected with canine PBMCs had multiple lesions, including necrosis in their lungs, livers, kidneys, and stomachs, and the injected cells were present around the lesions. By contrast, no mice injected with cultured NK cells without removing the CD3+ TCR- cells exhibited any clinical abnormalities. Moreover, they all survived the 90-day experimental period without exhibiting any histopathological changes. Accordingly, the results of this study suggest that canine NK cells do not cause significant side effects such as GVHD and allogeneic NK cells can safely be used for cancer immunotherapy in dogs.

Reproducibility of serum testing for environmental allergen-specific IgE in dogs in Europe.

Serum testing for allergen-specific immunoglobulin (Ig)E is commonly employed to identify allergens used for allergen-specific immunotherapy in dogs, yet the reliability of results has been a matter of debate. The aim of this study was to evaluate the reproducibility of serum tests for environmental allergen-specific IgE in three European laboratories. Serum was obtained from 33 client-owned dogs diagnosed with atopic dermatitis, divided into three aliquots and sent to the laboratories under different names. Two aliquots were sent simultaneously to one of the laboratories on the first day; the third sample was then sent to the same laboratory on the subsequent day. The laboratory for each patient was chosen according to a predetermined randomization list. The agreement between different samples from the same dog for each of the laboratories was calculated with a Cohen's Kappa test. Spearman's rank coefficients (rsp ) as well as the coefficients of variation (CV) additionally were calculated. The intra- and interassay agreements for laboratories A, B and C were 0.79 and 0.75, 0.92 and 0.90, and 0.90 and 0.85, respectively. The CVs were 18.92% and 22.95%, 14.43% and 18.79%, and 15.38% and 18.75% (respectively) and the rsp 0.73 and 0.68, 0.95 and 0.92, and 0.82 and 0.74 (respectively). The differences in reproducibility between laboratories complicate test interpretation and underline the importance of interpreting results of serum testing for allergen-specific IgE in the context of the patient's clinical history.

Effective Activation and Expansion of Canine Lymphocytes Using a Novel Nano-Sized Magnetic Beads Approach.

Expansion protocols for human T lymphocytes using magnetic beads, which serve as artificial antigen presenting cells (aAPCs), is well-studied. Yet, the efficacy of magnetic beads for propagation and functionality of peripheral blood lymphocytes (PBLs) isolated from companion dogs still remains limited. Domestic dog models are important in immuno-oncology field. Thus, we built the platform for induction of canine PBLs function, proliferation and biological activity using nano-sized magnetic beads (termed as MicroBeads) coated with anti-canine CD3 and CD28 antibodies. Herein we reveal that activation of canine PBLs via MicroBeads induces a range of genes involved in immediate-early response to T cell activation in dogs. Furthermore, canine T lymphocytes are effectively activated by MicroBeads, as measured by cluster formation and induction of activation marker CD25 on canine T cells as quickly as 24 h post stimulation. Similar to human T cells, canine PBLs require lower activation signal strength for efficient proliferation and expansion, as revealed by titration studies using a range of MicroBeads in the culture. Additionally, the impact of temperature was assessed in multiple stimulation settings, showing that both 37°C and 38.5°C are optimal for the expansion of canine T cells. In contrast to stimulation using plant mitogen Concanavalin A (ConA), MicroBead-based activation did not increase activation-induced cell death. In turn, MicroBeads supported the propagation of T cells with an effector memory phenotype that secreted substantial IL-2 and IFN-γ. Thus, MicroBeads represent an accessible and affordable tool for conducting immunological studies on domestic dog models. Similarities in inducing intracellular signaling pathways further underscore the importance of this model in comparative medicine. Presented herein MicroBead-based expansion platforms for canine PBLs may benefit adoptive immunotherapy in dogs and facilitate the design of next-generation clinical trials in humans.

PD-L1 immunohistochemistry for canine cancers and clinical benefit of anti-PD-L1 antibody in dogs with pulmonary metastatic oral malignant melanoma

Immunotherapy targeting programmed cell death 1 (PD-1) and PD-ligand 1 (PD-L1) represents promising treatments for human cancers. Our previous studies demonstrated PD-L1 overexpression in some canine cancers, and suggested the therapeutic potential of a canine chimeric anti-PD-L1 monoclonal antibody (c4G12). However, such evidence is scarce, limiting the clinical application in dogs. In the present report, canine PD-L1 expression was assessed in various cancer types, using a new anti-PD-L1 mAb, 6C11-3A11, and the safety and efficacy of c4G12 were explored in 29 dogs with pulmonary metastatic oral malignant melanoma (OMM). PD-L1 expression was detected in most canine malignant cancers including OMM, and survival was significantly longer in the c4G12 treatment group (median 143 days) when compared to a historical control group (n = 15, median 54 days). In dogs with measurable disease (n = 13), one dog (7.7%) experienced a complete response. Treatment-related adverse events of any grade were observed in 15 dogs (51.7%). Here we show that PD-L1 is a promising target for cancer immunotherapy in dogs, and dogs could be a useful large animal model for human cancer research.

Detection of indoleamine 2,3-dioxygenase 1-expressing cells in canine normal and tumor tissues.

Cancer immunotherapy is a novel cancer treatment for canine tumors. Indoleamine 2,3-dioxygenase 1 (IDO1) is overexpressed in some human tumors and inhibits antitumor immunity. In this study, we comprehensively evaluated expression pattern of IDO1 and the nature of IDO1-expressing cells in canine normal and tumor tissues. In normal tissue samples, IDO1 expression was detected only in the lymph nodes, spleen, tonsil tissues, and colon tissues. In contrast, IDO1-positive tumor cells were observed in several tumor tissue types. This is the first study to evaluate IDO1 expression in canine normal and tumor tissues, and the results suggest that IDO1 is a promising target for novel cancer immunotherapy in dogs with tumors.

Allergen-specific immunotherapy in dogs with atopic dermatitis: is owner compliance the main success-limiting factor?

While the efficacy of allergen-specific immunotherapy (ASIT) to treat canine atopic dermatitis has been well established, it remains unclear why not all dogs show the same response to treatment. The goal of the study was to determine the relationship between duration of ASIT and two measurements of success: disease severity and concomitant medication sparing effect. Data were retrospectively compiled for 145 dogs with atopic dermatitis treated with ASIT. As a measure of treatment compliance, cases were stratified into dogs treated for less than 12 months or for at least 12 months. Treatment efficacy, defined as a reduction in disease severity score (scale 0-10), was compared between both groups, and correlations between treatment success and several related factors were examined. ASIT treatment duration was strongly correlated with treatment efficacy. Animals treated for less than 12 months showed lower efficacy rates (22 per cent) than those treated for at least 12 months (65 per cent). Further, in animals treated for at least 12 months, concomitant medications were reduced more (87 per cent) than in animals treated for less than 12 months (39 per cent). A lack of owner compliance emerged as the main factor explaining the reduced effectiveness of ASIT. To improve treatment adherence, veterinarians and owners need to be better informed about ASIT mechanisms of action before starting treatment.