Immunotherapy in clinical canine leishmaniosis: a comparative update

Efficacy of a combination of nucleotides and lactoferrin in maintaining stable or improving the clinical picture and laboratory findings of leishmaniotic dogs: A randomized controlled study

This prospective, randomized, controlled, therapeutic study aimed to evaluate the efficacy of a product containing nucleotides and lactoferrin in maintaining or improving the clinical picture and laboratory findings of canine leishmaniosis (CanL). The safety and tolerance of this combination were also assessed. Forty Leishmania infantum-seropositive dogs, not requiring leishmanicidal and/or leishmaniostatic treatment, were enrolled in the study and randomized into treatment (TG) and placebo (CG) groups. Products A (containing nucleotides and lactoferrin) and B (placebo) were blindly administered to TG and CG, respectively, as palatable tablets at a rate of 1 tablet per 10 kg of weight once every 24 h for 6 months. Following inclusion (T0), dogs were followed up after 3 (T90) and 6 (T180) months. At each time point, for all animals enrolled physical examination and laboratory tests (complete blood count, biochemical panel including C-reactive protein [CRP] and ferritin, and serum protein electrophoresis) were performed. The immunofluorescence antibody test to detect antibodies for L. infantum (T0, T180), Ehrlichia canis (T0, T90, and T180), and Anaplasma phagocytophilum (T0, T90, and T180) was executed. A CanL-dedicated clinical score, using a validated scale from 0 (i.e., absence of clinical signs) to 19, was assigned. Four dogs (n=2 in TG, n=2 in CG) did not complete the study. No statistically significant differences in CanL clinical score were observed between CG and TG at T0, T90 and T180. Both TG and CG showed significant variations in anti-L. infantum antibody titres (p=0.0001 and p=0.004, respectively). In TG, antibody titres decreased in 77.8 %, increased in 5.5 %, and remained stable in 16.7 % of dogs, while in CG, decreased in 27.8 %, increased in 50 %, and remained stable in 22.2 % of dogs. During the study, CRP and ferritin remained stable in TG and significantly increased in CG. At T180, 9 out of 18 dogs (50 %) enrolled in the CG, and 1 out of 18 (5.6 %) enrolled in the TG, developed an active form of leishmaniosis. No side effects were reported in any patient included. In conclusion, a 6-month oral administration of a supplement containing nucleotides and lactoferrin was effective in maintaining a stable clinical score, improving antibody titres and potentially reducing the progression from non-active to active forms in L. infatum seropositive dogs. Furthermore, the product was well-tolerated, easy to administer, and free of side effects.

New immunomodulatory treatment protocol for canine leishmaniosis reduces parasitemia and proteinuria

The current standard treatment for canine leishmaniosis (CanL), N-methylglucamine antimoniate (MGA) given with allopurinol, is not fully effective and may cause adverse effects and drug resistance. In vitro and in vivo studies have shown that nucleotides, administered alone or with AHCC, offer benefits in the treatment of CanL. This study examines the effects of a new immunomodulatory treatment protocol in which dietary nucleotides and AHCC are added to the recommended standard treatment. Out of 160 sick dogs with naturally occurring clinical leishmaniosis recruited, 97 were randomized to a supplement (n = 47) or control (n = 50) group. All dogs received an initial 28-day course of MGA and 365-day course of allopurinol. From day 0 to day 730, dogs in the control group additionally received a placebo, while dogs in the supplement group received Impromune (Bioiberica S.A.U., Esplugues de Llobregat, Spain), an oral supplement providing 32 mg/kg nucleotides and 17 mg/kg AHCC daily. After 2 years, five dogs had relapsed in the supplement group (18.5%) while seven did so in the control group (22.6%). Over time, animals in both groups showed significant improvements in body weight, LeishVet clinical stage, clinical score, and anti-Leishmania antibodies. Adding the supplement to the standard protocol resulted in further significant improvements, namely in reducing the parasite load and urinary protein/creatinine ratio, improving IRIS stage, lowering serum creatinine levels on day 30, deceasing urine turbidity on day 365, and improving weight gain on day 545. The daily intake of the supplement over two years proved safe and well tolerated. Our study confirms the efficacy of the recommended standard treatment for CanL, but also reveals that by adding Impromune additional benefits are obtained, especially reduced parasitemia and improved renal function.

LaSap vaccine: Immunotherapy and immunochemotherapy associated with allopurinol in dogs naturally infected with Leishmania infantum

Canine visceral leishmaniasis is a parasitic zoonosis that has a profound impact on public health in countries where it is endemic. Chemotherapeutic treatments cannot keep dogs stable for long periods, and the risk of generating parasitic resistance must be considered. Forty-four symptomatic and naturally infected dogs with Leishmania infantum were tested with two treatment protocols (i) immunotherapy with LaSap vaccine and (ii) immunochemotherapy with LaSap vaccine plus allopurinol. At 90 days after the end of the treatment, it was verified that, although both protocols had generated significant clinical improvements with a greater production of IFN-γ/IL-10, in relation to the parasite load, mainly in the skin, the dogs treated only with immunotherapy maintained the same profile. These results indicate that LaSap is a good strategy to control dog parasitism.

Pilot Study on QTc Interval in Dogs Treated with Domperidone

Domperidone is used as an immunomodulatory drug for Leishmania infantum infection and disease in dogs. However, a pro-arrhythmic side effect, caused by prolonged QT intervals, is reported in humans. This pilot study evaluated the corrected QT (QTc) interval in dogs treated with domperidone for preventive or therapeutic management of leishmaniosis. The electrocardiogram and blood concentration of creatinine, urea nitrogen, sodium, potassium, and chloride were evaluated seven days before the start and on the last day of therapy in 17 dogs receiving domperidone for four weeks. In two dogs, the QTc interval was measured before and 2 h, 3 h, and 12 h after administration of the drug on the first day of treatment. After treatment, QTc measures and chloride concentrations increased significantly, although the QTc value slightly exceeded the upper reference limit only in one dog, and chloride concentrations were always normal. Creatinine concentrations significantly decreased after therapy. In the two dogs monitored at different times on the first day of treatment, QTc values were always normal. Domperidone caused a slight prolongation of QTc interval, and further studies should be made for a risk assessment in dogs with cardiac diseases, electrolytic imbalance, and in those receiving drugs increasing QT interval or competing with domperidone metabolism.

State-of-the-art Review on the Antiparasitic Activity of Benzimidazolebased Derivatives: Facing Malaria, Leishmaniasis, and Trypanosomiasis

Protozoan parasites represent a significant risk for public health worldwide, afflicting particularly people in more vulnerable categories and cause large morbidity and heavy economic impact. Traditional drugs are limited by their toxicity, low efficacy, route of administration, and cost, reflecting their low priority in global health management. Moreover, the drug resistance phenomenon threatens the positive therapy outcome. This scenario claims the need of addressing more adequate therapies. Among the diverse strategies implemented, the medicinal chemistry efforts have also focused their attention on the benzimidazole nucleus as a promising pharmacophore for the generation of new drug candidates. Hence, the present review provides a global insight into recent progress in benzimidazole-based derivatives drug discovery against important protozoan diseases, such as malaria, leishmaniasis and trypanosomiasis. The more relevant chemical features and structure-activity relationship studies of these molecules are discussed for the purpose of paving the way towards the development of more viable drugs for the treatment of these parasitic infections.

A blinded, randomized and controlled multicenter clinical trial to assess the efficacy and safety of Leisguard® as an immunotherapeutic treatment for healthy Leishmania infantum-seropositive dogs

BACKGROUND

Domperidone (Leisguard®) is an immunomodulatory drug used as a preventive measure in healthy dogs. However, no studies have been published in healthy Leishmania infantum-seropositive dogs. The aim of this study was to evaluate the clinical efficacy and safety of domperidone as immunotherapy in Leishmania-seropositive healthy dogs.

METHODS

Sixty-seven dogs were treated with domperidone at 0.5 mg/kg and 44 dogs received placebo, once daily for 4 consecutive weeks. Monthly treatments were repeated every 4 months until the end of the 1-year follow-up period. Veterinary examinations were performed on days 0, 30, 120, 150, 240, 270 and 360. Samples of blood and urine were collected on days 0, 120, 240 and 360 for routine laboratory tests and quantitative in-house ELISA for the detection of L. infantum-specific antibodies. Furthermore, Leishmania real-time PCR and IFN-γ ELISA were performed at day 0 and the end of the study. Dogs that developed disease were withdrawn from the study and classified as sick dogs. Adverse drug reactions were reported.

RESULTS

Thirty dogs developed disease during the follow-up period: 13/67 (19.4%) in the group treated with domperidone and 17/44 (38.6%) in the placebo-treated group (P = 0.03). Low-seropositive dogs treated with domperidone (4/40, 9.1%) were significantly less likely to develop disease compared to low-seropositive dogs treated with placebo (7/24, 29.2%; P = 0.04), while no differences were found between domperidone (9/23, 39.1%) and placebo (10/20, 50%) in medium- to high-seropositive dogs. At the end of the study, a higher proportion of Leishmania PCR-positive dogs was observed in the placebo-treated group (16/33, 48.5%) compared to the domperidone group (13/51, 25.5%; P = 0.04). Furthermore, low-seropositive dogs treated with domperidone with an increase of IFN-γ concentration presented a higher increase than those treated with placebo at the end of the study. Four dogs treated with domperidone presented self-limiting diarrhea.

CONCLUSIONS

Healthy dogs with low L. infantum antibody levels treated with domperidone were less likely to develop disease compared to placebo-treated dogs. Furthermore, domperidone presented a good safety profile.

Signalment, Immunological and Parasitological Status and Clinicopathological Findings of Leishmania-Seropositive Apparently Healthy Dogs

Canine leishmaniosis caused by Leishmania infantum is a disease with a wide range of clinical manifestations. Epidemiological serosurveys performed in Europe often lack a thorough assessment of clinical health status of studied dogs. The aim of this study was to evaluate signalment, immunological and parasitological status and clinicopathological findings of L. infantum-seropositive apparently healthy dogs (n = 212) living in endemic areas. Routine laboratory tests, endpoint in-house ELISA to quantify the anti-Leishmania antibodies, blood Leishmania qPCR and IFN-γ ELISA were performed. All dogs enrolled were L. infantum-seropositive and were classified as healthy (n = 105) or sick (n = 107) according to LeishVet guidelines. The sick group presented a higher proportion of medium to high antibody levels and positive qPCR and lower IFN-γ concentration compared to the healthy group. Sick dogs were mostly classified in LeishVet stage IIa. Biochemical alterations (98%) were the most common clinicopathological findings, with fewer urinary tract (46%) and hematological (40%) alterations. Apparently healthy L. infantum-seropositive dogs can be classified between truly healthy dogs and sick dogs with clinicopathological findings. Sick dogs presented medium to high seropositivity and parasitemia and low IFN-γ concentrations, and their most common clinicopathological abnormalities were serum protein alterations followed by proteinuria and lymphopenia.

Efficacy of domperidone plus renal diet in slowing the progression of chronic kidney disease in dogs with leishmaniosis

BACKGROUND

Chronic kidney disease (CKD) represents the main cause of mortality in dogs with leishmaniosis. Domperidone has recently been reported to improve kidney function in leishmaniotic dogs affected by CKD. Serum symmetric dimethylarginine (sSDMA) has also been shown to be a useful biomarker for earlier detection of decreased kidney function when compared to serum creatinine (sCr). This study aimed to assess the efficacy of domperidone plus renal diet in slowing the progression of nephropathy in leishmaniotic dogs with CKD, evaluating sSDMA and sCr as markers of kidney function.

METHODS

This study was a therapeutic, prospective, randomized, controlled, 11-month-long field trial. Dogs were recruited if classified as "exposed" to or "infected" with Leishmania infantum and affected by CKD at early stages. After enrolment (T0), dogs were randomized into groups T (treatment) and C (control). All dogs were fed a renal diet and then followed up at 90 (T1), 210 (T2), and 330 (T3) days after inclusion in the study. At T1 and T2, dogs in group T received an oral suspension of domperidone (1 ml/10 kg once a day for up to 28 days).

RESULTS

Twenty-two dogs (i.e., n = 12 in group T and n = 10 in group C) completed the study. At T0, the entire population of enrolled dogs presented a mean sSDMA value of 16.5 ± 3.4 μg/dl. At T1 (i.e., after 3 months of renal diet), sSDMA was significantly decreased in both groups, with an sSDMA of 13.1 ± 4.4 μg/dl for the entire population involved. From T1 to T3, sSDMA gradually increased in group C, while remaining stable in group T, which continued to show a significantly lower value of sSDMA at T3 than at T0. Regarding sCr, at T0 and T1, the mean values of the entire population of dogs were 1.1 ± 0.3 and 1.0 ± 0.4 mg/dl, respectively, with no statistical differences between groups T and C. In group T, sCr decreased significantly from T0 to T1, while returning at T3 to values similar to T0.

CONCLUSIONS

In this study, domperidone plus renal diet reduced the progression of kidney disease in leishmaniotic dogs affected by CKD.

Modulation of Host Immune Response during Leishmania infantum Natural Infection: A Whole-Transcriptome Analysis of the Popliteal Lymph Nodes in Dogs

Leishmania infantum, the etiological agent of canine leishmaniosis (CanL) in Europe, was responsible of the largest outbreak of human leishmaniosis in Spain. The parasite infects and survives within myeloid lineage cells, causing a potentially fatal disease if left untreated. The only treatment option relies on chemotherapy, although immunotherapy strategies are being considered as novel approaches to prevent progression of the disease. To this aim, a deeper characterization of the molecular mechanisms behind the immunopathogenesis of leishmaniosis is necessary. Thus, we evaluated, for the first time, the host immune response during L. infantum infection through transcriptome sequencing of the popliteal lymph nodes aspirates of dogs with CanL. Differential expression and weighted gene co-expression network analyses were performed, resulting in the identification of 5,461 differentially expressed genes (DEGs) and four key modules in sick dogs, compared to controls. As expected, defense response was the highest enriched biological process in the DEGs, with six genes related to immune response against pathogens (CHI3L1, SLPI, ACOD1, CCL5, MPO, BPI) included among the ten most expressed genes; and two of the key co-expression modules were associated with regulation of immune response, which also positively correlated with clinical stage and blood monocyte concentration. In particular, sick dogs displayed significant changes in the expression of Th1, Th2, Th17 and Tr1 cytokines (e. g. TNF-α, IFN-γ, IL-21, IL-17, IL-15), markers of T cell and NK cell exhaustion (e. g. LAG3, CD244, Blimp-1, JUN), and B cell, monocyte and macrophage disrupted functionality (e. g. CD40LG, MAPK4, IL-1R, NLRP3, BCMA). In addition, we found an overexpression of XBP1 and some other genes involved in endoplasmic reticulum stress and the IRE1 branch of the unfolded protein response, as well as one co-expression module associated with these processes, which could be induced by L. infantum to prevent host cell apoptosis and modulate inflammation-induced lymphangiogenesis at lymph nodes. Moreover, 21 lncRNAs were differentially expressed in sick dogs, and one key co-expression module was associated with chromatin organization, suggesting that epigenetic mechanisms could also contribute to dampening host immune response during natural L. infantum infection in the lymph nodes of dogs suffering from clinical leishmaniosis.

Nutritional Modulation of the Immune Response Mediated by Nucleotides in Canine Leishmaniosis

Leishmaniasis is an emerging, uncontrolled, and neglected zoonotic disease. Climate change is contributing to its ongoing global expansion. The dog is the main reservoir; hence the importance of implementing effective treatment, prevention, and control measures in this animal species to protect public health. However, although the standard treatment for canine leishmaniosis (CanL) is effective, it does not provide full parasitological clearance, and side effects and drug resistance have been described. The host's immune system plays a key role in the establishment and evolution of leishmaniasis. Dietary nucleotides modulate the immune response and, given their reported efficacy and safety in sick and clinically healthy Leishmania-infected dogs and because they represent a sustainable option with no associated side effects or resistance, they could be included within the prevention, treatment, and control strategies for leishmaniasis. This article briefly summarizes the scientific literature on CanL management, including unresolved issues, and reviews the scientific evidence on immunomodulatory effects of dietary nucleotides in different animal species. It also proposes a CanL management algorithm, including nucleotides. It is concluded that nutritional modulation of the immune response with nucleotides can contribute to better management of leishmaniasis following a One Health approach, especially in the COVID-19 era.

Effect of domperidone (leisguard®) on antibody titers, inflammatory markers and creatinine in dogs with leishmaniosis and chronic kidney disease

Background

Immunotherapeutic drugs, such as domperidone, have been shown to be promising treatments against canine leishmaniosis (CanL), but limited data are available. The aim of this pilot study (therapeutic, prospective and non-controlled) was to evaluate the effect of domperidone on serum antibody titers of Leishmania infantum, globulins, gamma globulins, acute-phase proteins (e.g. C-reactive protein [CRP]), big endothelin-1 (big ET-1), serum creatinine (SC) and proteinuria in dogs with leishmaniosis affected by chronic kidney disease (CKD).

Methods

Dogs were recruited if “exposed” to or “infected” with L. infantum and affected by CKD (IRIS stage 1 [proteinuric] or IRIS stage 2–3a [SC < 3.5 mg/dl; proteinuric or non-proteinuric]). After inclusion, an oral suspension of domperidone was administered, and the dogs were followed up for 180 days, with checks at 30, 60, 90 and 180 days after initial treatment.

Results

Of the 14 recruited dogs, nine showed a statistically significant reduction in SC (χ² = 9.1, df = 3, P = 0.028), but not in the urine protein/creatinine ratio (χ² = 6.43, df = 3, P = 0.092). All dogs showed a significant reduction in antibody titers for L. infantum (χ² = 9.56, df = 2, P = 0.008), globulins (χ² = 11.08, df = 3, P = 0.011) and gamma globulins (χ² = 12.38, df = 3, P = 0.006) during the study period. There was also a statistically significant reduction in CRP (χ² = 16.7, df = 3, P = 0.001), but not in big ET-1 (χ² = 2.04, df = 3, P = 0.563).

Conclusions

This study provides preliminary results on the ability of domperidone to improve SC and reduce anti-L. infantum antibody titers, globulins, gamma globulins and CRP in dogs with leishmaniosis and CKD.

Graphical abstract

The recent development of thymol derivative as a promising pharmacological scaffold

Thymol (a phenol ring bearing active phytoconstituent) is a privileged scaffold, which is diversified in natural sources. This scaffold acts as an obligatory template for scheming and arriving at designing some newer drug-molecules with potential biological activities. In the pharmacological perspective, the promising active sites of the scaffold are the positions C-1, C-4, and C-6 of thymol that would be accountable for developing potent drug candidates. This review aims to explore the various synthetic routes and the structural-activity relationship of thymol scaffold with suitable active pharmacophore sites.

Preventive measures of canine leishmaniosis in Italy: Attitudes of veterinarians based on a questionnaire

There are several topical ectoparasiticides, drugs, supplements and vaccines that protect dogs against sand fly bites and/or reduce the risk of Leishmania infantum infection. This large variety of products and the absence of comparative studies mean that veterinarians are often faced with uncertainty. The aim of the study was to characterise the attitudes of veterinarians towards leishmaniosis prevention in client-owned dogs in Italy. A web-based questionnaire was prepared with 28 questions covering the working environment of veterinarians, advice given to owners regarding topical ectoparasiticides, advice on systemic prevention, and the use of diagnostic tests on which to base advice for prevention. The questionnaire was emailed to 9,426 veterinarians and answers were collected after 100 days. A total of 542 questionnaires were returned (response percentage 5.8 %): 54.8 % of the veterinarians considered their working area to be endemic, 29.3 % examined dogs from urban areas, and 42.3 % diagnosed ≥10 dogs/year with leishmaniosis. Those veterinarians who diagnosed ≥10 dogs/year with leishmaniosis were more likely to consider their working area to be endemic, whereas those who examined dogs mainly from urban areas were less likely to consider the area to be endemic. Veterinarians who considered the working area to be endemic were more prone to prescribe ectoparasiticides throughout the year, including collars and spot-on products and a combination of the two, vaccine alone or vaccine and domperidone combined, and used qualitative serological Leishmania tests. The attitude of veterinarians did not differ whether dogs were from urban or rural areas. In conclusion, veterinarians who consider their working area to be endemic or who frequently diagnose dogs with leishmaniosis tend to adopt more comprehensive strategies, and their attitudes are not influenced by the origin of the dogs: urban or rural. Overall, in Italy the attitudes of veterinarians in relation to canine leishmaniosis prevention appear to vary considerably.

Nucleotides and AHCC Enhance Th1 Responses In Vitro in Leishmania-Stimulated/Infected Murine Cells

A stronger Th1 (cellular) immune response in canine leishmaniosis (CanL) leads to a better prognosis. Dietary nucleotides plus AHCC^® have shown beneficial effects in dogs with clinical leishmaniosis and in clinically healthy Leishmania-infected dogs. The potential leishmanicidal activity of nucleotides and AHCC was assessed by quantifying nitric oxide (NO) production and replication of parasites. Their effects on lymphocyte proliferation were studied with and without soluble Leishmania infantum antigen (SLA) stimulation. Cytokine level variations were assessed using naïve and L. infantum-infected macrophages/lymphocytes cocultures. Promastigotes and amastigotes proliferation and NO macrophage production were not directly affected. Lymphocyte proliferation was significantly enhanced by nucleotides, AHCC, and their combinations only after SLA stimulation. Nucleotides and AHCC significantly increased the production of IL-1β, IL-2, IL-5, IL-9, IL-10, and IL-12 by naïve immune cells. In naïve and L. infantum-infected macrophage/lymphocyte cocultures, nucleotides with or without AHCC led to significant increases in IFN-γ and TNF-α. Given that these cytokines are involved in the effective Th1 immune response against Leishmania parasites, these mechanisms of action could explain the previously reported in vivo clinical efficacy of such combination and further support the use of nucleotides with or without AHCC in the management of CanL patients.