Strategic use of 4 % deltamethrin impregnated-collar in seropositive dogs reduces the incidence of seroreactivity to visceral leishmaniasis in dogs from endemic areas.

The effectiveness of a visceral leishmaniasis (VL) control strategy based on the application of 4 % deltamethrin impregnated collars (DIC) exclusively in seropositive dogs was assessed between 2018 and 2019, through a prospective study. The effectiveness of DIC-collaring was evaluated by comparing the incidence rate of anti-leishmanial antibodies among dogs from two endemic districts in Brazil. In one of the areas, the conventional control measure which is based on the non-compulsory euthanasia of LV seropositive dogs, was practiced by the official healthy service as a regular procedure, whereas strategic collaring, conceived in this study, was carried out in the other. Results of serological tests applied to serum samples collected from all domiciled dogs were evaluated in three consecutive times, spaced by around 200 days. Incidence rates of VL seroreactivity were compared between districts in the same period of time as well as within the same district, in consecutive periods. Based on the results, the risk of infection in the population under conventional control measure was up to four times higher than the risk of infection where DIC-collaring was used. The strategic use of collar proposed here emerged as a promising measure for VL control in dogs from endemic areas. Strategic collaring does not rely on the euthanasia of infected animals, an extremely controversial procedure, and instead of being used in all dogs, as collaring is normally recommended; only seropositive dogs are intervened. Strategic use of DIC has the potential to drastically reduce costs, if compared to mass collaring canine population.

Pharmacokinetics, Dose-Proportionality, and Tolerability of Intravenous Tanespimycin (17-AAG) in Single and Multiple Doses in Dogs: A Potential Novel Treatment for Canine Visceral Leishmaniasis.

In the New World, dogs are considered the main reservoir of visceral leishmaniasis (VL). Due to inefficacies in existing treatments and the lack of an efficient vaccine, dog culling is one of the main strategies used to control disease, making the development of new therapeutic interventions mandatory. We previously showed that Tanespimycin (17-AAG), a Hsp90 inhibitor, demonstrated potential for use in leishmaniasis treatment. The present study aimed to test the safety of 17-AAG in dogs by evaluating plasma pharmacokinetics, dose-proportionality, and the tolerability of 17-AAG in response to a dose-escalation protocol and multiple administrations at a single dose in healthy dogs. Two protocols were used: Study A: four dogs received variable intravenous (IV) doses (50, 100, 150, 200, or 250 mg/m2) of 17-AAG or a placebo (n = 4/dose level), using a cross-over design with a 7-day "wash-out" period; Study B: nine dogs received three IV doses of 150 mg/m2 of 17-AAG administered at 48 h intervals. 17-AAG concentrations were determined by a validated high-performance liquid chromatographic (HPLC) method: linearity (R2 = 0.9964), intra-day precision with a coefficient of variation (CV) ≤ 8%, inter-day precision (CV ≤ 20%), and detection and quantification limits of 12.5 and 25 ng/mL, respectively. In Study A, 17-AAG was generally well tolerated. However, increased levels of liver enzymes-alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT)-and bloody diarrhea were observed in all four dogs receiving the highest dosage of 250 mg/m2. After single doses of 17-AAG (50-250 mg/m2), maximum plasma concentrations (Cmax) ranged between 1405 ± 686 and 9439 ± 991 ng/mL, and the area under the curve (AUC) plotting plasma concentration against time ranged between 1483 ± 694 and 11,902 ± 1962 AUC 0-8 h µg/mL × h, respectively. Cmax and AUC parameters were dose-proportionate between the 50 and 200 mg/m2 doses. Regarding Study B, 17-AAG was found to be well tolerated at multiple doses of 150 mg/m2. Increased levels of liver enzymes-ALT (28.57 ± 4.29 to 173.33 ± 49.56 U/L), AST (27.85 ± 3.80 to 248.20 ± 85.80 U/L), and GGT (1.60 ± 0.06 to 12.70 ± 0.50 U/L)-and bloody diarrhea were observed in only 3/9 of these dogs. After the administration of multiple doses, Cmax and AUC 0-48 h were 5254 ± 2784 µg/mL and 6850 ± 469 µg/mL × h in plasma and 736 ± 294 µg/mL and 7382 ± 1357 µg/mL × h in tissue transudate, respectively. In conclusion, our results demonstrate the potential of 17-AAG in the treatment of CVL, using a regimen of three doses at 150 mg/m2, since it presents the maintenance of high concentrations in subcutaneous interstitial fluid, low toxicity, and reversible hepatotoxicity.

Global Distribution of Canine Visceral Leishmaniasis and the Role of the Dog in the Epidemiology of the Disease.

Visceral leishmaniasis is a disease caused by protozoa of the species Leishmania (Leishmania) infantum (syn = Leishmania chagasi) and Leishmania (Leishmania) donovani, which are transmitted by hematophagous insects of the genera Lutzomyia and Phlebotomus. The domestic dog (Canis familiaris) is considered the main urban reservoir of the parasite due to the high parasite load on its skin, serving as a source of infection for sandfly vectors and, consequently, perpetuating the disease in the urban environment. Some factors are considered important in the perpetuation and spread of canine visceral leishmaniasis (CVL) in urban areas, such as stray dogs, with their errant behavior, and houses that have backyards with trees, shade, and organic materials, creating an attractive environment for sandfly vectors. CVL is found in approximately 50 countries, with the number of infected dogs reaching millions. However, due to the difficulty of controlling and diagnosing the disease, the number of infected animals could be even greater. In the four continents endemic for CVL, there are reports of disease expansion in endemic countries such as Brazil, Italy, Morocco, and Tunisia, as well as in areas where CVL is not endemic, for example, Uruguay. Socio-environmental factors, such as migration, drought, deforestation, and global warming, have been pointed out as reasons for the expansion into areas where it had been absent. Thus, the objective of this review is to address (i) the distribution of CVL in endemic areas, (ii) the role of the dog in the visceral leishmaniasis epidemiology and the factors that influence dog infection and the spread of the disease, and (iii) the challenges faced in the control of CVL.

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.

Canine Visceral Leishmaniasis: A Histological and Immunohistochemical Study of Fibropoiesis in Chronic Interstitial Pneumonitis.

We studied some fibrotic aspects of chronic interstitial pneumonitis in the lungs of dogs infected with Leishmania infantum. The lungs of eleven naturally infected dogs, twelve experimentally infected with two distinct strains of L. infantum (BH401 and BH46), and six uninfected (controls) dogs, were analyzed by histological, parasitological, and immunohistochemical studies. Conventional histology (HE), collagen deposition (Gomori's silver staining for reticulin collagen fibers), and immunohistochemistry for myofibroblast characterization were carried out based on the cellular expression of alpha-smooth muscle actin, vimentin, cytokeratin, E-cadherin, snail antigen homologue 1 (SNAI1) (Snail), and the cytokine expression of transforming growth factor-beta (TGF-ß). Parasitological screening was carried out using conventional polymerase chain reaction (PCR) and the immunohistochemical reaction of streptavidin-peroxidase for visualizing Leishmania amastigotes. Dogs naturally infected with L. infantum and experimentally infected with L. infantum BH401 strains showed intense interstitial pneumonitis characterized by thickening of the alveolar septa as a consequence of an intense diffuse and focal (plaques) chronic exudate of mononuclear cells associated with fibrogenesis. The expression of alpha-actin, vimentin, and TGF-ß was higher in the lung interstitium of all infected dogs than in the other two groups (BH46 strain and controls). Moreover, in both the naturally and experimentally infected dog (BH401 strain) groups, the expression of Snail was moderate to intense in contrast to the other groups. Based on these immunohistochemical results, we concluded that mesenchymal cells are active in promoting changes in the extracellular matrix in the lungs of dogs naturally and experimentally infected with L. infantum, but it depends on the virulence of the parasite.

Comparative Study of Colorimetric In Situ Hybridization and Quantitative Real-Time Polymerase Chain Reaction for Diagnosis of Infection by Leishmania infantum in Dogs in Formalin-Fixed and Paraffin-Embedded Skin.

The zoonotic visceral leishmaniasis is caused by the protozoan Leishmania infantum and dogs are reservoirs for this parasite. For the diagnosis of Leishmania at the species level in dogs in formalin-fixed, paraffin-embedded skin (FFPES) samples, colorimetric in situ hybridization (CISH) and quantitative real-time polymerase chain reaction (qPCR) are options, but their sensitivities are not well established. Therefore, the aim of this study was to determine the sensitivity of these two techniques in FFPES for the diagnosis of the L. infantum infection in dogs using culture as the reference standard. The FFPES of 48 dogs with cutaneous infection by L. infantum confirmed by culture and by multilocus enzyme electrophoresis were examined by CISH and qPCR using specific probes for L. infantum. The sensitivities of qPCR, CISH and their combination were, respectively, 77.0%, 58.0% and 83.3%. The sensitivities of qPCR in dogs with and without clinical signs were, respectively, 74.2% and 82.4%. The sensitivities of CISH in dogs with and without clinical signs were, respectively, 61.3% and 52.9%. The CISH and qPCR showed satisfactory sensitivities for the diagnosis of L. infantum in the FFPES of dogs, even in dogs without clinical signs, and their combination increases the sensitivity for this diagnosis.

Diagnosis of Canine Visceral Leishmaniasis by Flow Cytometry Serology using the rMELEISH Multiepitope Antigen Coupled in a Functional Bead.

BACKGROUND: Visceral leishmaniasis (VL) is a zoonotic disease, with dogs being the main reservoir of the Leishmania infantum parasite. OBJECTIVE: To develop a new flow cytometry test to diagnosis canine VL (CVL) diagnosis. METHODS: The current study addresses a new flow cytometry test using beads coupled to the multiepitope antigen rMELEISH. RESULTS: In the study set of samples a sensitivity (87.1%) and specificity (89.9%) was observed. Considering the dogs' clinical status, 20/20 (100.0%) of the symptomatic sera tested positive, while 19/22 (86.4%) of the oligosymptomatic and 16/20 (80.0%) of asymptomatic were positive. In the non-infected control, all samples (0/30) tested as negative. In the cross-reaction control, the test was more efficient in dogs infected with L. braziliensis (2/10) and Trypanosoma cruzi (0/10), than those with Babesia canis (4/10) and Ehrlichia canis (4/10). Dogs immunized with different vaccines (Leishmune, Leish-Tec®, or LBSap) did not present serological reactivity. CONCLUSION: The flow cytometry serology through coupling the antigen rMELEISH in functional beads showed high accuracy in diagnosing CVL.

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.

Presence of Leishmania sp. amastigotes in the reproductive tract of dogs with visceral leishmaniasis

ABSTRACT Background: Although canine visceral leishmaniasis (CVL) transmission primarily occurs through the bite of phlebotomine sand flies infected with Leishmania infantum, alternative routes may exist. Methods: Thirty-four dogs diagnosed with CVL were sampled for parasitological investigation in tissues from the reproductive tract. Results: Amastigotes of Leishmania sp. were present in 79% (27/34) of the reproductive system samples, with distinct infection rates depending on the tissue. Conclusions: Our data confirms that alternative routes, such as horizontal and vertical transmissions, should be considered in the epidemiological chain of CVL.

Elucidating the role played by bone marrow in visceral leishmaniasis.

Leishmaniasis is a widespread group of infectious diseases that significantly impact global health. Despite high prevalence, leishmaniasis often receives inadequate attention in the prioritization of measures targeting tropical diseases. The causative agents of leishmaniasis are protozoan parasites of the Leishmania genus, which give rise to a diverse range of clinical manifestations, including cutaneous and visceral forms. Visceral leishmaniasis (VL), the most severe form, can be life-threatening if left untreated. Parasites can spread systemically within the body, infecting a range of organs, such as the liver, spleen, bone marrow and lymph nodes. Natural reservoirs for these protozoa include rodents, dogs, foxes, jackals, and wolves, with dogs serving as the primary urban reservoir for Leishmania infantum. Dogs exhibit clinical and pathological similarities to human VL and are valuable models for studying disease progression. Both human and canine VL provoke clinical symptoms, such as organ enlargement, fever, weight loss and abnormal gamma globulin levels. Hematologic abnormalities have also been observed, including anemia, leukopenia with lymphocytosis, neutropenia, and thrombocytopenia. Studies in dogs have linked these hematologic changes in peripheral blood to alterations in the bone marrow. Mouse models of VL have also contributed significantly to our understanding of the mechanisms underlying these hematologic and bone marrow abnormalities. This review consolidates information on hematological and immunological changes in the bone marrow of humans, dogs, and mice infected with Leishmania species causing VL. It includes findings on the role of bone marrow as a source of parasite persistence in internal organs and VL development. Highlighting gaps in current knowledge, the review emphasizes the need for future research to enhance our understanding of VL and identify potential targets for novel diagnostic and therapeutic approaches.

Transmission-Blocking Vaccines for Canine Visceral Leishmaniasis: New Progress and Yet New Challenges.

Dogs with visceral leishmaniasis play a key role in the transmission cycle of Leishmania infantum to humans in the urban environment. There is a consensus regarding the importance of developing a vaccine to control this disease. Despite many efforts to develop a protective vaccine against CVL, the ones currently available, Leish-tec® and LetiFend®, have limited effectiveness. This is due, in part, to the complexity of the immune response of the naturally infected dogs against the parasite and the complexity of the parasite transmission cycle. Thus, strategies, such as the development of a transmission-blocking vaccines (TBVs) already being applied to other vector-borne diseases like malaria and dengue, would be an attractive alternative to control leishmaniasis. TBVs induce the production of antibodies in the vertebrate host, which can inhibit parasite development in the vector and/or interfere with aspects of vector biology, leading to an interruption of parasite transmission. To date, there are few TBV studies for CVL and other leishmaniasis forms. However, the few studies that exist show promising results, thus justifying the further development of this approach.

Diagnostic Potential for the Detection of Canine Visceral Leishmaniasis of an ELISA Assay Based on the Q5 Recombinant Protein: A Large-Scale and Comparative Evaluation Using Canine Sera with a Positive Diagnosis from the Dual-Path-Platform (DPP) Test.

Dogs are considered the major domestic reservoir for human visceral leishmaniasis, a serious disease caused by the Leishmania infantum parasite. Diagnosis of canine visceral leishmaniasis (CVL) is critical for disease control, with several methods currently available. Among the serological tests, the DPP rapid test and the EIE-LVC, more commonly used in Brazil, are associated with variable sensitivity and specificity. Research with novel recombinant proteins such as the ELISA with the recombinant chimeric protein Q5 may therefore improve the CVL diagnosis. This study aimed to evaluate the true diagnostic potential of Q5 in an ELISA assay using a large number of CVL-suspected sera (406) with a previous positive diagnosis based on the rapid DPP test. Sera from the DPP-positive dogs, also assessed with the EIE-LVC test, were compared with sera from healthy dogs (n = 46) and used for ELISA tests using the recombinant Q5. The resulting data as well as the correlation with the clinical signs and the environmental characteristics of the animals were analyzed using Medal and GraphPad Prism 8.0. Overall, similar levels of lower sensitivity (67-68%) were seen for both the commercial EIE-LVC test and the Q5 ELISA when all assessed sera were considered, but a much greater sensitivity (92%) was seen for those samples from symptomatic dogs only. In contrast, many negative results were observed for the DPP-positive sera from asymptomatic dogs or those with no clinical information available. A selection of those sera were tested yet again in new ELISA assays using a second batch of the recombinant Q5, purified under milder denaturing conditions, as well as using another recombinant protein (Lci13). The results reveal a higher-than-expected incidence of likely false-positive results for DPP, reinforcing the need for other recombinant proteins, such as the chimeric Q5, to be investigated as possible alternatives to the currently used CVL diagnostic methods.

Prevalence and incidence of canine visceral leishmaniasis and its clinical-immunological features in an endemic area of the Brazilian Amazon.

BACKGROUND: A cohort study for 2 years period analysed the prevalence, incidence and clinical-immunological features of canine Leishmania (L.) chagasi-infection in 316 mongrel dogs in a visceral leishmaniasis-endemic area in Pará State, Brazil. OBJECTIVE/METHODS: Diagnosis of infection was performed by the indirect fluorescent antibody test (IFAT-IgG), the leishmanin skin test (LST) and a parasite search (from the popliteal lymph node aspiration) at the beginning of the study and at 6, 12 and 24 months intervals. RESULTS: IFAT/LST revealed three immune profiles of infection: (I) IFAT(+) /LST(-) (81), (II) IFAT(-) /LST(+) (17) and (III) IFAT(+) /LST(+) (13). Prevalence of profiles I, II and III were 25.6, 5.4 and 4.1%, and an overall prevalence 35.1%. Incidence of profiles I, II and III were 5.4, 0.3 and 0.0%, and an overall incidence 5.7% dogs per month. Incidence at the age ranges <1 year, ≥1 year, <7 years and ≥7 years evidenced a highest rate in the age range <1 year (6.6% dogs per month). Parasitological diagnosis was positive in 19% dogs at the prevalence (85.7% profile I), and in 11% at the incidence (100% profile I). The clinical picture of 179 infected dogs showed 145 (81%) of profile I (82% subclinical); 21 (11.7%) of profile II (100% subclinical); and 13 (7.3%) of profile III (84.6% subclinical). Conversion from subclinical to sick dogs was higher (p < 0.05) in profile I (40.2%) than in profiles II (5.8%) and III (9%). Immunological conversion showed that only 3.2% of profile I dogs (prevalence) converted to LST(+) (two at the end of the first 6 months and 1 after 24 months), while 82.3% of profile II dogs converted to IFAT(+) (11 in the first 6 months, whereas three after 12 months). A 100% death rate was observed in dogs from profile I alone. CONCLUSION: These results reinforce the need of adopting preventive strategies against CVL as early as in the first semester of the dog's life.

The Program for the Control of Visceral Leishmaniasis in Brazil: The Effect of the Systematic Euthanasia of Seropositive Dogs as a Single Control Action in Porteirinha, a Brazilian City with an Intense Transmission of Visceral Leishmaniasis.

BACKGROUND: Porteirinha is endemic for visceral leishmaniasis (VL), with intense disease transmission of the disease. We evaluated the impact of canine euthanasia as a single control measure on the incidence of VL in humans and canines. METHODS: A prospective observational cohort study was carried out over four years (1998-2002) in 8 of the 12 neighborhoods of the city. The dynamics of canine visceral leishmaniasis (CVL) transmission were evaluated for 2 years, before beginning the screening-culling intervention. The comparative morbidity index (CMI) was used to stratify areas with the greatest risk of CVL, and the spatial distribution of human and canine VL cases was compared using univariate and bivariate K-functions. RESULTS: Human cases conglomerated in three neighborhoods. Spatial clusters were detected for CVL in 1998, 2000, and 2001, but not in 1999, when greater spatial dispersion occurred. The screening and culling intervention reduced the number of human VL cases and decreased the incidence of CVL, mainly in neighborhoods with a high CMI. CONCLUSIONS: The systematic euthanasia of seropositive dogs was shown to be an effective control action of the Program for Control of Visceral Leishmaniasis (PCLV) in Brazil. The fundamental role of domestic dogs in the epidemiological chain of VL was reaffirmed.

Dogs with canine visceral leishmaniasis have a boost of extracellular vesicles and miR-21-5p up-expression.

This retrospective cohort study analysed extracellular vesicles (EVs) and microRNAs (miRNAs) excreted in canine sera from dogs with canine visceral leishmaniasis (CanVL). A total of 56 canine sera were divided into Group I (28, from healthy dogs) and Group II (28, from the same dogs, but already with CanVL). CanVL was determined by clinical and laboratory diagnoses. Canine sera were ultra-centrifuged to recover EVs (Can-EVs). Analyses by transmission electron microscopy, nanoparticle tracking analysis (NTA), sodium dodecyl sulfate-poli-acrylammide gel eletroforesis (SDS-PAGE) and, Immunoblot confirmed the presence of (i) microvesicles/exosomes and (ii) the tetraspanins CD63 and CD9. EVs secreted by Leishmania (Leishmania) infantum-EVs were reactive against sera from dogs with CanVL (performed by ELISA and Immunoblot). NTA analyses exhibited that concentrations of Can-EVs from dogs with CanVL (7.78 × 1010 Can-EVs/mL) were higher (p < .0001) than the non-infected dogs (mean: 1.47 × 1010 Can-EVs/mL). These results suggested that concentrations of Can-EVs were able to distinguish dogs with CanVL from healthy dogs. The relative expressions of 11 miRNAs species (miR-21-5p, miR-146a-5p, miR-125b-5p, miR-144-3p, miR-194-5p, miR-346, miR-29c-3p, miR-155-5p, miR-24-3p, miR-181a-5p, and miR-9-5p) were estimated in purified miRNAs of 30 canine sera. Dogs with CanVL up-expressed miR-21-5p and miR-146a-5p when compared with healthy dogs. The other miRNA species were poorly or not expressed in canine sera. In conclusion, this study suggests that CanVL induces changes in size and concentration of Can-EVs, as well as, the up-expression of miR-21-5p and miR-146a-5p in infected dogs.

Canine visceral leishmaniasis diagnosis by UV spectroscopy of blood serum and machine learning algorithms.

Visceral leishmaniasis (VL) is a zoonotic disease caused by the protozoan Leishmania infantum, and dogs are considered the main urban hosts for future disease transmission. The first and most effective control against the spread of disease relies on identifying infected animals, followed by their treatment or sacrifice, to reduce the protozoan reservoirs. Despite the availability of various diagnostic tests for VL in dogs the development of a quick and accurate diagnosis is essential from a public health and ethical point of view. Here we analyze the use of UV-Vis spectroscopy as an alternative diagnostic method for VL diagnosis by using the antigen-antibody interaction in canine blood serum and machine learning algorithms. The main UV spectra in the 220 to 280 nm range exhibit nine electronic absorption bands, but no significative difference could be identified between the positive and negative group spectra. Finally, UV pre-proceed spectra by SNV (standard normal variate) were submitted to principal component analysis followed by Linear SVM algorithm, the prediction model was tested in a leave-one-out cross-validation and external validation test reaching an overall accuracy of 75%.

LBMPL Vaccine Therapy Induces Progressive Organization of the Spleen Microarchitecture, Improved Th1 Adaptative Immune Response and Control of Parasitism in Leishmania infantum Naturally Infected Dogs.

The spleen plays a central role in human and canine visceral leishmaniasis, where the activation of the immune response occurs in one of the tissues where Leishmania infantum reproduces. Therefore, this organ is both a target to understand the mechanisms involved in the parasite control and a parameter for assessing the therapeutic response. In this sense, this study aimed to evaluate the main histological, immunological and parasitological aspects in the spleen of symptomatic dogs naturally infected by L. infantum treated with the therapeutic vaccine LBMPL. For this, dogs were divided into four groups: dogs uninfected and untreated (NI group); L. infantum-infected dogs that were not treated (INT group); L. infantum-infected dogs that received treatment only with monophosphoryl lipid A adjuvant (MPL group); and L. infantum-infected dogs that received treatment with the vaccine composed by L. braziliensis promastigote proteins associated with MPL adjuvant (LBMPL group). Ninety days after the therapeutics protocol, the dogs were euthanized and the spleen was collected for the proposed evaluations. Our results demonstrated a reduction of hyperplasia of red pulp and follicular area of white pulp, increased mRNA expression of IFN-γ, TNF-α, IL-12 and iNOS, and decreased IL-10 and TGF-ß1, and intense reduction of splenic parasitism in dogs treated with the LBMPL vaccine. These results possibly suggest that the pro-inflammatory environment promoted the progressive organization of the splenic architecture favoring the cellular activation, with consequent parasite control. Along with previously obtained data, our results propose the LBMPL vaccine as a possible treatment strategy for canine visceral leishmaniasis (CVL).

CD4+ T-lymphocytes from asymptomatic dogs infected with Leishmania infantum are able to activate macrophages for higher leishmanicidal ability in an in vitro co-culture experiment.

Dogs are the most common domestic reservoir of Leishmania infantum, making canine visceral leishmaniasis (CVL) a serious public health issue. Identifying new methodologies that can mimic lymphoid and myeloid competence in naturally infected dogs could lower costs and save time in preliminary screenings of potential immunotherapeutic agents and vaccines against CVL. For that, we established a cell-to-cell communication approach between lymphocytes and myeloid cells from healthy, asymptomatic (infected, without apparent clinical signs) and symptomatic (infected with apparent clinical signs) dogs. Peripheral blood mononuclear cells (PBMC) from these dogs were used as source of CD4+, CD8+ T lymphocytes and macrophages, that were posteriorly infected with L. infantum GFP+ promastigotes (green fluorescent protein). Macrophages co-cultured with purified lymphocytes were tested for the ability to control cellular parasitism, and their microbicidal function by producing nitric oxide (NO) and reactive oxygen species (ROS). The kind of T cell response within the co-culture was also evaluated, by assessing their ability to produce interferon-gamma (IFN-γ) and interleukin 4 (IL-4). The data suggests that T lymphocytes from symptomatic dogs are more prone to produce IL-4 than the ones from asymptomatic dogs. Macrophages from asymptomatic dogs also demonstrated a higher microbicidal potential, with increased levels of NO and ROS production, compared to symptomatic dogs, mainly in highly parasitized cells. Together, our results identify the ratio of IL-4/IFN-γ produced by CD4+ and CD8+ T cells, as well as, the ratio between parasite GFP signal/NO and ROS signal in macrophages as potential immunological biomarkers of failure and success of the screened agents. Our findings also propose a reliable methodology that can be used to follow the immune response in trials of potential drugs or vaccines targeting CVL.

Diagnostic Classification of Cases of Canine Leishmaniasis Using Machine Learning.

Proposal techniques that reduce financial costs in the diagnosis and treatment of animal diseases are welcome. This work uses some machine learning techniques to classify whether or not cases of canine visceral leishmaniasis are present by physical examinations. For validation of the method, four machine learning models were chosen: K-nearest neighbor, Naïve Bayes, support vector machine and logistic regression models. The tests were performed on three hundred and forty dogs, using eighteen characteristics of the animal and the ELISA (enzyme-linked immunosorbent assay) serological test as validation. Logistic regression achieved the best metrics: Accuracy of 75%, sensitivity of 84%, specificity of 67%, a positive likelihood ratio of 2.53 and a negative likelihood ratio of 0.23, showing a positive relationship in the evaluation between the true positives and rejecting the cases of false negatives.

Antigens and their diagnostic performance for Canine Visceral Leishmaniasis: A critical review.

Canine visceral leishmaniasis (CVL) is the most aggressive and lethal form of leishmaniasis manifesting in dogs and represents a major public health concern. Although there are sufficiently sensitive molecular tools for CVL diagnosis, they are not accessible at the main points of disease dissemination, in which context serodiagnosis has been used as an alternative tool on the epidemiological control. As an attempt to develop more accurate immunodiagnostic assays, many antigens have been tested over the years, on different platforms. This review aimed to access studies reporting new antigens that can be applied for CVL serodiagnosis. Articles published from January of 2016 to March of 2021 were retrieved from Google Scholar, Science Direct, and PubMed, using "Canine Visceral Leishmaniasis" and "Serodiagnosis" as keywords. In total, 1527 articles were identified, of which 42 were selected based on exclusion factors. Sensitivity, specificity, sample size, and sample quality data were extracted by manual curation and analyzed. Of the selected articles, 26 contemplated ELISA, which enabled a more thorough comparison and a critical review of these studies. Soluble Leishmania Antigens (SLA) and the A2 protein were used as controls in 53.8 and 46.15 % of these articles, respectively, and were evaluated separately; their frequent use was questioned. Subsequently, articles that evaluated other assay platforms, such as immunochromatography, immunosensors, and others, were also reported and evaluated. Finally, data relative to validation studies of commercial kits were briefly discussed. Our results show that there are several antigens with great potential for the development of accurate diagnostic tools, but further testing is required. The critical analysis also brings insights that can be useful for more assertive diagnostic development of more robust tools for CVL serodiagnosis.