Meglumine Antimoniate and Miltefosine Combined With Allopurinol Sustain Pro-inflammatory Immune Environments During Canine Leishmaniosis Treatment

Treatment of Canine Leishmaniasis with Meglumine Antimoniate: A Clinical Study of Tolerability and Efficacy

Antimoniate therapy, in association with allopurinol, is one of the first-line treatments of canine leishmaniasis (CanL). This study evaluates the potential adverse effects associated with aNm in the treatment of CanL through both a retrospective analysis and a long-term prospective study also aimed to investigate its efficacy. The retrospective study reviewed records of 87 dogs with CanL with at least one follow-up available during or at the end of therapy with aNm (Glucantime®) at a dose of 50 mg/kg administered subcutaneously twice a day in association with allopurinol. In total, 29.8% of dogs showed adverse effects during treatment as local reactions at the injection site (n = 6), severe systemic reaction to pain (originating from the inoculation site) with depression and anorexia (n = 4), systemic disease due to renal function worsening (n = 4), acute pancreatitis (n = 1), diarrhea (n = 5), vomiting (n = 3) and severe idiosyncratic skin reactions (n = 3). Of these dogs, 13 (14.9%) required treatment suspension. The prospective study included 16 dogs, selected among the LeishVet stages II and III CKD IRIS stage 1 (International Renal Interest Society staging of canine Chronic Kidney Disease) and treated with the same aNm plus allopurinol protocol as in the retrospective study and observed for 360 days; 2 dogs were excluded for severe reactions at the injection site. Mild and transient adverse events were reported in the other 4 dogs. The criteria used to evaluate the efficacy of treatment with aNm were as follows: a reduction in the clinical score and improvement and/or normalization of laboratory parameters, negativization of PCR on the bone marrow samples and disease-free interval time. The proportion of reduction in the clinical score reached 91.9% at D180. No animals showed clinical laboratory relapse during the whole study duration and interestingly, the PCR results showed complete negativity between D0 and D60 in 78.5% of animals. Veterinarians must be vigilant regarding the potentially serious adverse effects associated with aNm and promptly stop drug administration if unexpected clinical manifestations occur. On the other hand, they should not discard its use for CanL treatment since it is confirmed that aNm in association with allopurinol is highly effective in controlling CanL.

Critically Appraised Topic on Canine Leishmaniosis: Does Treatment with Antimonials and Allopurinol Have the Same Clinical and Clinicopathological Efficacy as Treatment with Miltefosine and Allopurinol, after One Month of Treatment?

The treatment of canine leishmaniosis commonly involves meglumine antimoniate with allopurinol or miltefosine with allopurinol. This study aims to compare the clinical and clinicopathological efficacy at 28-30 days of conventional dosing regimens for both treatments using the critically appraised topic methodology. A comprehensive search across three databases (PubMed, CAB Abstracts, and Web of Science) from March 2004 to September 2023 yielded 16 relevant articles, encompassing 325 ogs treated with meglumine antimoniate and allopurinol, and 273 dogs treated with miltefosine and allopurinol. The findings indicated a significantly higher rate of complete clinical cure in the group treated with meglumine antimoniate and allopurinol. Most dogs in both groups exhibited improvement in clinicopathological alterations after one month of treatment. No significant difference was observed in the number of dogs that showed a negative Leishmania qPCR between the two groups, one month post-treatment. However, quantitative serology results were not commonly reported in the available data and therefore this aspect could not be compared.

Synthetic Peptides Selected by Immunoinformatics as Potential Tools for the Specific Diagnosis of Canine Visceral Leishmaniasis

Diagnosing canine visceral leishmaniasis (CVL) in Brazil faces challenges due to the limitations regarding the sensitivity and specificity of the current diagnostic protocol. Therefore, it is urgent to map new antigens or enhance the existing ones for future diagnostic techniques. Immunoinformatic tools are promising in the identification of new potential epitopes or antigen candidates. In this study, we evaluated peptides selected by epitope prediction for CVL serodiagnosis in ELISA assays. Ten B-cell epitopes were immunogenic in silico, but two peptides (peptides No. 45 and No. 48) showed the best performance in vitro. The selected peptides, both individually and in combination, were highly diagnostically accurate, with sensitivities ranging from 86.4% to 100% and with a specificity of approximately 90%. We observed that the combination of peptides showed better performance when compared to peptide alone, by detecting all asymptomatic dogs, showing lower cross-reactivity in sera from dogs with other canine infections, and did not detect vaccinated animals. Moreover, our data indicate the potential use of immunoinformatic tools associated with ELISA assays for the selection and evaluation of potential new targets, such as peptides, applied to the diagnosis of CVL.

Clinical and parasitological impact of short-term treatment using miltefosine and allopurinol monotherapy or combination therapy in canine visceral leishmaniasis

Canine visceral leishmaniasis is an endemic zoonosis in Brazil. Dogs are the main hosts in urban environments. The treatment has gained popularity since the Brazilian government authorized miltefosine for canine treatment. The aim of this study was to investigate the clinical and parasitological impact of short-term treatment with miltefosine and allopurinol, alone and in combination. We evaluated the ability of pharmacotherapy to reduce clinical signs of disease, antibody levels using the indirect fluorescence antibody test (IFAT) and skin parasite load via qPCR after 28 days of treatment. The therapeutic protocols promoted a significant decline in clinical signs and in the skin parasite load in dogs (p < 0.01). We observed a moderate correlation between the skin parasite load and the clinical score in all three treatment groups (r > 0.5) Antibody levels did not decrease in this short period. It was concluded that the treatment with allopurinol reduced the number of parasites in the skin of dogs with visceral leishmaniasis in the short term. However, its efficiency is potentiated when associated with miltefosine.

Canine Leishmaniasis: Update on Epidemiology, Diagnosis, Treatment, and Prevention

Dog are the main reservoir of Leishmania infantum, causing canine leishmaniasis, an incurable multisystemic disease that leads to death in symptomatic dogs, when not treated. This parasite causes visceral, cutaneous, and mucosal leishmaniasis in people in the Mediterranean Basin, North Africa, South America, and West Asia. This disease is mostly unknown by veterinarians outside the endemic areas, but the disease is expanding in the Northern Hemisphere due to travel and climate change. New methodologies to study the epidemiology of the disease have found new hosts of leishmaniasis and drawn a completely new picture of the parasite biological cycle. Canine leishmaniasis diagnosis has evolved over the years through the analysis of new samples using novel molecular techniques. Given the neglected nature of leishmaniasis, progress in drug discovery is slow, and the few drugs that reach clinical stages in humans are unlikely to be commercialised for dogs, but several approaches have been developed to support chemotherapy. New-generation vaccines developed during the last decade are now widely used, along with novel prevention strategies. The implications of the epidemiology, diagnosis, treatment, and prevention of canine leishmaniasis are fundamental to public health.

Dogs with leishmaniosis: how are we managing proteinuria in daily practice? A Portuguese questionnaire-based study

Background

Proteinuria is a common finding in dogs with leishmaniosis. Although antileishmanial therapeutic protocols are widely implemented, little information is available on which treatments are most adequate for identifying proteinuria in patients with canine leishmaniosis (CanL), especially regarding the use of immunosuppressants. The aim of this study was to explore the current paradigm regarding the antiproteinuric approach adopted by veterinary practitioners in Portugal to treat dogs with CanL.

Methods

A questionnaire-based study was developed using Google Forms®. The questionnaire presented a number of different hypothetical scenarios of CanL, and the topics surveyed included the general features of the respondents and the protocols preferred by these respondents to manage proteinuria in the presented scenarios, including choice of therapeutic drugs, appropriate diet and use of immunosuppressants, in dogs with immune-mediated glomerulonephritis. The questionnaire was internally prevalidated and diffused online over a 2-month period through Portuguese veterinary social networking groups, and data were collected for descriptive analysis.

Results

A total of 86 veterinary practitioners responded to the survey. When exposed to theoretical scenarios of proteinuria in dogs with CanL at stages IIb, III and IV (LeishVet guidelines), 16.3%, 62.8% and 93.8% of the respondents, respectively, answered that they would treat it. The dog was started on a renal diet as therapy by 28.6%, 83.3% and 97.4% of respondents, respectively. Angiotensin-converting enzyme inhibitors (ACEI) were prescribed by 100%, 85.2% and 78.9% of respondents as first-choice drugs for CanL at stages IIb, III and IV, respectively, with ACEI used in monotherapy by 64.3%, 40.7% and 46.1%. In comparison, protocols using ACEI in combination with other compounds were chosen by 7.1%, 33.3% and 39.5% of respondents, and combination therapy which did not include ACEI was the choice of 0.0%, 12.9% and 14.5%. Regarding immunosuppressants, 44.2% of the respondents answered they would prescribe them, with 97.4% electing for prednisolone and 5.3% choosing mycophenolate mofetil.

Conclusions

Among the veterinary practitioners who responded, proteinuria treatment was considered since stage IIb CanL, although implementation of a therapeutic approach was more evident in advanced CanL stages. ACEI were the first-choice drugs, particularly for the treatment of stage IIb CanL; in advanced stages, a combination of antiproteinuric drugs was more often used. Immunosuppressant use was controversial, although when applied, prednisolone was the preferred choice. These findings reinforce the small body of evidence that supports the use of such drugs and the need to further explore their role in CanL.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05222-w.

A Questionnaire-Based Survey on the Long-Term Management of Canine Leishmaniosis by Veterinary Practitioners

Simple Summary

Canine Leishmaniosis is a chronic and potentially fatal disease, caused by Leishmania infantum, a zoonotic microorganism. In economically disadvantaged regions, costs associated with long-term patient monitoring may determine that some owners decline veterinary follow-up of their dogs, with potentially severe implications for animal welfare and public health. This online, questionnaire-based survey aimed to assess how Portuguese veterinary practitioners perform long-term patient management and recognize relapses. More than half of the respondents stated that most dog owners declare having financial restraints, which condition the use of diagnostic tests during long-term follow-up. Allopurinol ad aeternum or until disease remission and domperidone were the most prescribed treatment, and relapses were detected by the reappearance or worsening of clinical signs by most veterinary practitioners. The rate of relapse detection was higher in the most economically favored regions, probably because of a lesser constraint on the use of the appropriate diagnostic tests. This study confirms that owner financial restraints negatively influence veterinary follow-up and relapse recognition, potentially compromising clinical decision making and favoring the maintenance of Leishmania infantum infection endemic status in Portugal.

Abstract

Canine Leishmaniosis (CanL) is a chronic and potentially fatal disease. In economically disadvantaged regions, costs associated with long-term patient monitoring may determine that some owners decline veterinary follow-up of their dogs. This online, questionnaire-based survey aimed to assess how Portuguese veterinary practitioners perform long-term patient monitoring and recognize relapses. More than 50% of respondents reported that 50–100% of dog owners declared financial restraints. Hence, in these circumstances, most veterinary practitioners only performed clinical examination and serology. However, when owners did not declare financial restriction, other tests were additionally performed, such as renal and hepatic profiles, hemogram, serum protein electrophoresis and urine protein creatinine ratio. The mean number of exams performed when owners presented financial restraints was significantly lower than the number of exams performed without economic limitations. Most veterinary practitioners prescribed allopurinol ad aeternum or until disease remission and domperidone. CanL relapses were recognized by more than half of respondents “Always”, through the reappearance or worsening of clinical signs, whereas about a quarter detected an increase in anti-Leishmania antibody levels and identified abnormalities in the serum protein electrophoresis profile. The relapse rate was higher in the Lisbon Metropolitan Area and north, the most economically favored regions of Portugal. This study confirms that owner financial restraints negatively influence veterinary follow-up and relapse recognition, ultimately compromising clinical decision making and favoring the maintenance of Leishmania infantum infection endemicity.

Comparative evaluation of meglumine antimoniate encapsulated in a mixture of conventional and PEGylated liposomes and immunotherapy using an anti-canine IL-10 receptor-blocking monoclonal antibody on canine visceral leishmaniasis

This study compared the therapeutic potential of the chemotherapy using meglumine antimoniate encapsulated in a mixture of conventional and PEGylated liposomes (Nano Sb^v) and immunotherapy with anti-canine IL-10 receptor-blocking monoclonal antibody (Anti IL-10R) on canine visceral leishmaniasis (CVL). Twenty mongrel dogs naturally infected by L. infantum, displaying clinical signs of visceral leishmaniasis were randomly divided in two groups. In the first one, nine dogs received six intravenous doses of a mixture of conventional and PEGylated liposomes containing meglumine antimoniate at 6.5 mg Sb/kg/dose. In the second one, eleven dogs received two intramuscular doses of 4 mg of anti-canine IL-10 receptor-blocking monoclonal antibody. The animals were evaluated before (T0) and 30, 90, and 180 days after treatments. Our major results demonstrated that both treatments were able to maintain hematological and biochemical parameters, increase circulating T lymphocytes subpopulations, increase the IFN-γ producing T-CD4 lymphocytes, restore the lymphoproliferative capacity and improve the clinical status. However, although these improvements were observed in the initial post-treatment times, they did not maintain until the end of the experimental follow-up. We believe that the use of booster doses or the association of chemotherapy and immunotherapy (immunochemotherapy) is promising to improve the effectiveness of treating CVL for improving the clinical signs and possibly reducing the parasite burden in dogs infected with Leishmania infantum.

Detection of Leishmania infantum amastigotes in neutrophil from peripheral blood in a naturally infected dog

Canine visceral leishmaniasis (CVL) is a zoonotic disease of high lethality caused by Leishmania infantum in the Americas. In the infected dog, the amastigotes are scarce in blood, especially in the late phase of the disease. This study aimed to report a rare case of L. infantum amastigotes found in neutrophils from peripheral blood of a naturally infected dog in terminal phase of CVL, also describing its clinical status before and after treatment with miltefosine 2%. The dog, which presented as polysymptomatic and with classical signs and symptoms of CVL was submitted to the following tests: Dual Path Platform (DPP) rapid test, ELISA and parasitological examination of peripheral blood. Hematological and biochemical parameters were obtained before and after treatment. All diagnostic tests were positive for CVL. The identification of L. infantum amastigotes inside neutrophils from peripheral blood was confirmed through microscopy, and the species was confirmed by molecular analysis. At the end of the treatment, peripheral parasitemia was not detected, and improvements were observed in clinical and laboratorial parameters. Finally, this atypical finding can be used as example to raise discussions about the real immunological role of neutrophils in late phases of CVL and its clinical/therapeutic implications.

Diagnosis and clinical management of canine leishmaniosis by general veterinary practitioners: a questionnaire-based survey in Portugal

BACKGROUND

Canine leishmaniosis (CanL) can be appropriately managed following international recommendations. However, few studies have assessed the preferred protocols in real-life veterinary practice and whether these are in line with the guidelines. This survey aimed to investigate the current trends in the clinical management of CanL among veterinary practitioners in Portugal, taking into consideration different scenarios of infection/disease and the awareness of and application by veterinary practitioners of the current guidelines.

METHODS

A questionnaire-based survey was conducted online using an electronic platform. The following topics were surveyed: (i) general characteristics of the responding veterinarian; (ii) the preferred protocols used for the diagnosis, treatment and prevention of CanL, considering different theoretical scenarios of infection/disease; and (iii) the responding veterinarian's current knowledge and application of the existing guidelines on CanL. After internal validation, the survey was distributed online, for 2 months, via Portuguese social network veterinary groups. Data were collected for descriptive analysis.

RESULTS

Eighty-six replies were obtained. Analysis of the results showed that the preferred diagnostic techniques varied widely according to the theoretical scenario of infection/disease. In general daily practice, serology testing (enzyme-linked immunosorbent assay [ELISA]) was the most used tool (67.4%). The preferred matrices used for PCR test were lymph nodes (62.3%) and/or bone marrow (59.0%). Regarding treatment, for subclinical infection/stage I CanL, 51.2% of the respondents did not prescribe any medical treatment, but 98.8% proceeded with both monitoring and preventive measures. Among those who prescribed a treatment (n = 42), most chose domperidone (47.6%). For the treament of stages IIa, IIb and III CanL, allopurinol/meglumine antimoniate (MA) was chosen by 69.8, 73.3 and 51.2% of respondents, respectively, followed by allopurinol/miltefosine (20.9, 19.8 and 38.4%, respectively). In contrast, dogs with stage IV CanL were mostly treated with allopurinol/miltefosine (48.8%) rather than with allopurinol/MA (23.3%). The use of repellents was the preferred preventive strategy (98.8%). About 93.0% of responders were aware of the existence of guidelines, and most of these veterinarians consulted the guidelines of the LeishVet group and the Canine Leishmaniosis Working Group; however, 31.3% reported that they did not follow any specific recommendations.

CONCLUSIONS

Of the veterinarians responding to the survey, most reported following international guidelines for the clinical management of CanL. While allopurinol/MA was the preferred therapeutic protocol for the treatment of stages II/III CanL, allopurinol/miltefosine was the first choice for the treatment of stage IV CanL, possibly due to the unpredictable effect of MA on renal function. This study contributes to a better understanding of the trends in practical approaches to the treatment of CanL in Portugal.

Comparison of Two Dosing Regimens of Miltefosine, Both in Combination With Allopurinol, on Clinical and Parasitological Findings of Dogs With Leishmaniosis: A Pilot Study

Miltefosine (MIL)–allopurinol combination therapy administered at standard dosage is effective to treat canine leishmaniosis, nevertheless for some dogs the digestive tolerance of MIL is not acceptable. This study evaluates an alternative therapeutic protocol by using a modified dosage of MIL to increase its effectiveness and improve the digestive tolerance. Thirty-four Leishmania infantum owned naturally infected dogs were included and monitored for 180 days. The dogs were allocated in two randomized groups: Group X−18 dogs treated with MIL registered dose of 2 mg/kg, oral administration, once daily, for 28 days; Group Y−16 dogs treated with 1.2 mg/kg for 5 days followed by 2.5 mg/kg for 25 days. Both groups were also treated with allopurinol. Digestive tolerance was monitored by adverse events observation. Treatments effectiveness was evaluated by monitoring the reduction of clinical score, the improvement of clinicopathological abnormalities, the reduction of parasitological load by PCR and the number of relapses. 16.6% dogs of group X and 12.5% dogs of group Y showed treatment associated adverse events. The reduction of clinical score was 61.7% for group X and 71.6% for group Y. All dogs showed an improvement of laboratory parameters after treatment. Quantitative PCR showed better results in group Y compared to group X; relapses were only registered in four dogs of group X. The modified protocol demonstrates a better trend of results in term of tolerance, clinical effectiveness, parasitological load reduction and relapses control, suggesting it could be considered for new large-scale studies.

3D-Hepatocyte Culture Applied to Parasitology: Immune Activation of Canine Hepatic Spheroids Exposed to Leishmania infantum

The application of innovative three-dimensional (3D) spheroids cell culture strategy to Parasitology offers the opportunity to closely explore host–parasite interactions. Here we present a first report on the application of 3D hepatic spheroids to unravel the immune response of canine hepatocytes exposed to Leishmania infantum. The liver, usually considered a major metabolic organ, also performs several important immunological functions and constitutes a target organ for L. infantum infection, the etiological agent of canine leishmaniasis (CanL), and a parasitic disease of major veterinary and public health concern. 3D hepatic spheroids were able to sense and immunologically react to L. infantum parasites, generating an innate immune response by increasing nitric oxide (NO) production and enhancing toll-like receptor (TLR) 2 and interleukin-10 gene expression. The immune response orchestrated by canine hepatocytes also lead to the impairment of several cytochrome P450 (CYP450) with possible implications for liver natural xenobiotic metabolization capacity. The application of meglumine antimoniate (MgA) increased the inflammatory response of 3D hepatic spheroids by inducing the expression of Nucleotide oligomerization domain (NOD) -like receptors 1 and NOD2 and TLR2, TLR4, and TLR9 and enhancing gene expression of tumour necrosis factor α. It is therefore suggested that hepatocytes are key effector cells and can activate and orchestrate the immune response to L. infantum parasites.

Prognostic Factors and Life Expectancy in Canine Leishmaniosis

Canine leishmaniosis (CanL) is a chronic and potentially fatal disease. The prognosis of CanL depends on the severity of the clinical signs and clinicopathological abnormalities presented by the dog at the time of diagnosis. This study aims to estimate the survival time of dogs with CanL, determining the prognostic value of different clinical and clinicopathological parameters. Medical records of 99 dogs diagnosed with CanL in five veterinary centers of the Alentejo region (Portugal) were examined retrospectively. The majority of dogs presented hyperproteinemia, moderate normocytic normochromic anemia, normal blood urea and creatinine levels and were classified as stage 1 according to the International Interest Society (IRIS) guidelines at the time of diagnosis. The severity of anemia, presence of concomitant infectious diseases at the time of diagnosis and the anti-Leishmania therapy were correlated with the survival time. The influence of renal dysfunction was evaluated by Receiver Operating Characteristic (ROC) curve and survival analysis. Survival analysis demonstrated that patients classified as IRIS 1 at the time of diagnosis survived more than four years, in contrast with dogs classified as IRIS 2 that survived around two and half years and dogs classified as IRIS 3-4 that survived around one month. IRIS stage deteriorated during the course of CanL in one third of the dogs and was the principal cause of death or euthanasia in a high proportion of animals. In some cases, dogs did not receive anti-Leishmania treatment or abandoned the veterinary follow-ups, which may have considerable repercussions for animal wellbeing and public health. This study reinforces the value of blood urea and creatinine levels as prognostic factors in CanL.

Immunophenotyping of Peripheral Blood, Lymph Node, and Bone Marrow T Lymphocytes During Canine Leishmaniosis and the Impact of Antileishmanial Chemotherapy

Dogs are a major reservoir of Leishmania infantum, etiological agent of canine leishmaniosis (CanL) a zoonotic visceral disease of worldwide concern. Therapeutic protocols based on antileishmanial drugs are commonly used to treat sick dogs and improve their clinical condition. To better understand the impact of Leishmania infection and antileishmanial drugs on the dog's immune response, this study investigates the profile of CD4⁺ and CD8⁺ T cell subsets in peripheral blood, lymph node, and bone marrow of sick dogs and after two different CanL treatments. Two CanL groups of six dogs each were treated with either miltefosine or meglumine antimoniate combined with allopurinol. Another group of 10 clinically healthy dogs was used as control. Upon diagnosis and during the following 3 months of treatment, peripheral blood, popliteal lymph node, and bone marrow mononuclear cells were collected, labeled for surface markers CD45, CD3, CD4, CD8, CD25, and intracellular nuclear factor FoxP3, and T lymphocyte subpopulations were immunophenotyped by flow cytometry. CanL dogs presented an overall increased frequency of CD8⁺ and CD4⁺CD8⁺ double-positive T cells in all tissues and a decreased frequency of CD4⁺ T cells in the blood. Furthermore, there was a higher frequency of CD8⁺ T cells expressing CD25⁺FoxP3⁺ in the blood and bone marrow. During treatment, these subsets recovered to levels similar to those of healthy dogs. Nevertheless, antileishmanial therapy caused an increase of CD4⁺CD25⁺FoxP3⁺ T cells in all tissues, associated with the decrease of CD8⁺CD25⁻FoxP3⁻ T cell percentages. These findings may support previous studies that indicate that L. infantum manipulates the dog's immune system to avoid the development of a protective response, ensuring the parasite's survival and the conditions that allow the completion of Leishmania life cycle. Both treatments used appear to have an effect on the dog's immune response, proving to be effective in promoting the normalization of T cell subsets.