Exogenous surfactant reduces inflammation and redox imbalance in rats under prone or supine mechanical ventilation

Mechanical ventilation (MV) is a lifesaving therapy for patients with acute or chronic respiratory failure. Despite, it can also cause lung injury by inducing or worsening inflammatory responses and oxidative stress. Several clinical approaches have protective effects on the lungs, including the prone position and exogenous surfactant; however, few studies have evaluated the association between the two strategies, especially in individuals without previous lung injury. We tested the hypothesis that the effects of the homogenization in lung aeration caused by the prone position in association with the anti-inflammatory properties of exogenous surfactant pre-treatment could have a cumulative protective effect against ventilator-induced lung injury. Therefore, Wistar rats were divided into four experimental groups: Mechanical Ventilation in Supine Position (MVSP), Mechanical Ventilation in Prone position (MVPP), Mechanical Ventilation in Supine Position + surfactant (MVSPS), and Mechanical Ventilation in Prone Position + Surfactant (MVPPS). The intranasal instillation of a porcine surfactant (Curosurf®) was performed in the animals of MVSPS and MVPPS 1 h before the MV, all the rats were subjected to MV for 1 h. The prone position in association with surfactant decreased mRNA expression levels of pro-inflammatory cytokines in ventilated animals compared to the supine position; in addition, the NfκB was lower in MVPP, MVSPS and MVPPS when compared to MVSP. However, it had no effects on oxidative stress caused by MV. Pre-treatment with exogenous surfactant was more efficient in promoting lung protection than the prone position, as it also reduced oxidative damage in the lung parenchyma. Nevertheless, the surfactant did not cause additional improvements in most parameters that were also improved by the prone position. Our results indicate that the pre-treatment with exogenous surfactant, regardless of the position adopted in mechanical ventilation, preserves the original lung histoarchitecture, reduces redox imbalance, and reduces acute inflammatory responses caused by mechanical ventilation in healthy adult Wistar rats.

A specific Leishmania infantum polyepitope vaccine triggers Th1-type immune response and protects against experimental visceral leishmaniasis

The development of an immunogenic, effective, and safe vaccine is essential as an alternative for disease control. The present study aimed to evaluate the immunogenicity and efficacy potential of a polyepitope T-cell antigen candidate against visceral leishmaniasis in a murine model. BALB/c mice were immunized with three doses subcutaneously with Poly-T Leish alone or adjuvanted with Saponin plus Monophosphoryl lipid A, with 15-day intervals between doses, and challenged with 10⁷ stationary-phase Leishmania infantum promastigotes via tail vein. Immunogenicity and parasitism in spleen and liver of immunized mice were evaluated 45 days post-challenge. Our results revealed that the immunization with Poly-T Leish and Poly-T Leish/SM increases the percentage of specific T (CD4⁺ and CD8⁺) lymphocytes proliferation in vitro after antigen-specific stimulation. Also, Poly-T Leish and Poly-T Leish/SM groups showed a high percentage of IFN-γ and TNF-α-producing T cells, meanwhile, the Poly-T Leish/SM group also showed an increased percentage of multifunctional T cells producing double and triple-positive (IFN-γ⁺TNF-α⁺IL-2⁺) cytokines. The immunization with Poly-T Leish or Poly-T Leish/SM stimulated a decreased IL-4 and IL-10 compared to the Saline and adjuvant group. Poly-T Leish/SM immunized mice exhibit a noteworthy reduction in the parasite burden (spleen and liver) through real-time PCR (96%). Moreover, we observed higher nitrite secretion in 120-hour stimulated-culture supernatant using Griess method. We demonstrated that the Poly-T Leish/SM candidate was potentially immunogenic, providing enhancement of protective immune mechanisms, and conferred protection reducing parasitism. Our candidate was considered potential against visceral leishmaniasis, and eventually, could be tested in phase I and II clinical trials in dogs.

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-β1, 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).

Immunochemotherapy for visceral leishmaniasis: combinatorial action of Miltefosine plus LBSapMPL vaccine improves adaptative Th1 immune response with control of splenic parasitism in experimental hamster model

The control of human visceral leishmaniasis (VL) is hard since there are no vaccines available as well as the treatment is hampered by toxicity and resistant parasites. Furthermore, as human, and canine VL causes immunosuppression, the combination of drugs with immunostimulatory agents is interesting to upregulate the immunity, reducing side-effects, improving treatment approaches against disease. Herein, we assessed the immunochemotherapy using miltefosine along with a vaccine formulated by Leishmania braziliensis antigens + saponin + monophosphoryl lipid-A (LBSapMPL) in L. infantum-infected hamsters. Two months after infection, the animals received treatments, and after 15 days they were evaluated for the treatment effect. The potential anti-Leishmania effect of miltefosine + LBSapMPL-vaccine was revealed by a specific immune response activation reflecting in control of spleen parasitism using half the miltefosine treatment time. The treated animals also showed an increase of total and T-CD4 splenocytes producing IFN-γ and TNF-α and a decrease of interleukin-10 and anti-Leishmania circulating IgG. In addition, it was demonstrated that the control of spleen parasitism is related to the generation of a protective Th1 immune response. Hence, due to the combinatorial action of miltefosine with LBSapMPL-vaccine in immunostimulating and controlling parasitism, this immunochemotherapy protocol can be an important alternative option against canine and human VL.

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.

Hepatoprotective, antioxidant, anti-inflammatory, and antiviral activities of silymarin against mayaro virus infection

Infection caused by Mayaro virus (MAYV) is responsible for causing acute nonspecific fever, in which the majority of patients develop incapacitating and persistent arthritis/arthralgia. Mayaro fever is a neglected and underreported disease without treatment or vaccine, which has gained attention in recent years after the competence of Aedes aegypti to transmit MAYV was observed in the laboratory, coupled with the fact that cases are being increasingly reported outside of endemic forest areas, calling attention to the potential of an urban cycle arising in the near future. Thus, to mitigate the lack of information about the pathological aspects of MAYV, we previously described the involvement of oxidative stress in MAYV infection in cultured cells and in a non-lethal mouse model. Additionally, we showed that silymarin, a natural compound, attenuated MAYV-induced oxidative stress and inhibited MAYV replication in cells. The antioxidant and anti-MAYV effects prompted us to determine whether silymarin could also reduce oxidative stress and MAYV replication after infection in an immunocompetent animal model. We show that infected mice exhibited reduced weight gain, hepatomegaly, splenomegaly, anaemia, thrombocytopenia, leukopenia, increased liver transaminases, increased pro-inflammatory cytokines and liver inflammation, increased oxidative damage biomarkers, and reduced antioxidant enzyme activity. However, in animals infected and treated with silymarin, all these parameters were reversed or significantly improved, and the detection of viral load in the liver, spleen, brain, thigh muscle, and footpad was significantly reduced. This work reinforces the potent hepatoprotective, antioxidant, anti-inflammatory, and antiviral effects of silymarin against MAYV infection, demonstrating its potential against Mayaro fever disease.

IL-10 receptor blockade controls the in vitro infectivity of Leishmania infantum and promotes a Th1 activation in PBMC of dogs with visceral leishmaniasis

An important strategy to reduce the risk of visceral leishmaniasis (VL) in humans is to control the infection and disease progression in dogs, the domestic reservoir of Leishmania infantum parasites. Certain therapeutic strategies that modulate the host immune response show great potential for the treatment of experimental VL, restoring the impaired effector functions or decreasing host excessive responses. It is known that the overproduction of interleukin-10 (IL-10) promotes parasite replication and disease progression in human VL as well as in canine visceral leishmaniasis (CVL). Thus, in the present study we investigated the potential of the anti-canine IL-10 receptor-blocking monoclonal antibody (Bloq IL-10R) to control and reduce in vitro infectivity of L. infantum and improve the ability of PBMC isolated from VL dogs to alter the lymphoproliferative response and intracytoplasmic cytokines. Overall, GFP⁺Leishmania showed lower capacity of in vitro infectivity in the presence of Bloq IL-10R. Moreover, addition of Bloq IL-10R in cultured PBMC enhanced T-CD4 and CD8 proliferative response and altered the intracytoplasmic cytokine synthesis, reducing CD4⁺IL-4⁺ cells and increasing CD8⁺IFN-γ⁺ cells after specific antigen stimulation in PBMC of dogs. Furthermore, we observed an increase of TNF-α levels in supernatant of cultured PBMC under IL-10R neutralizing conditions. Together, our findings are encouraging and reaffirm an important factor that could influence the effectiveness of immune modulation in dogs with VL and suggest that blocking IL-10R activity has the potential to be a useful approach to CVL treatment.

A chimeric vaccine combined with adjuvant system induces immunogenicity and protection against visceral leishmaniasis in BALB/c mice

In Brazil, canine visceral leishmaniasis is an important public health problem due to its alarming growth. The high prevalence of infected dogs reinforces the need for a vaccine for use in prophylactic vaccination campaigns. In the present study, we evaluate the immunogenicity and protection of the best dose of Chimera A selected through the screening of cytokines production important in disease. BALB/c mice were vaccinated subcutaneously with three doses and challenged intravenously with 1 × 10⁷L. infantum promastigotes. Spleen samples were collected to assess the intracellular cytokine profile production, T cell proliferation and parasite load. At first, three different doses of Chimera A (5 μg, 10 μg and 20 μg) were evaluated through the production of IFN-γ and IL-10 cytokines. Since the dose of 20 μg showed the best results, it was chosen to continue the study. Secondarily, Chimera A at dose of 20 μg was formulated with Saponin plus Monophosphoryl lipid A. Vaccination with Chimera A alone and formulated with SM adjuvant system was able to increase the percentage of the proliferation of specific T lymphocytes and stimulated a Th1 response with increased levels of IFN-γ, TNF-α and IL-2, and decreased of IL-4 and IL-10. The vaccine efficacy through real-time PCR demonstrated a reduction in the splenic parasite load in animals that received Chimera A formulated with the SM adjuvant system (92%). Additionally, we observed increased levels of nitric oxide in stimulated-culture supernatants. The Chimera A formulated with the SM adjuvant system was potentially immunogenic, being able to induce immunoprotective mechanisms and reduce parasite load. Therefore, the use of T-cell multi-epitope vaccine is promising against visceral leishmaniasis.

Heterologous vaccine therapy associated with half course of Miltefosine promote activation of the proinflammatory response with control of splenic parasitism in a hamster model of visceral leishmaniasis

Visceral leishmaniasis (VL) is a serious and neglected disease present worldwide. Chemotherapy using pentavalent antimony (Sb^V) is the most practical and inexpensive strategy available for the VL treatment today, however, it has high toxicity. Alternatively, other drugs are used as viable leishmanicidal therapeutic options. Miltefosine is the only anti-leishmanial agent administered orally, however, it has been reducing its effectiveness. In this sense, there is no ideal therapy for VL since the drugs currently used trigger severe side effects causing discontinuation of treatment, which carries an imminent risk for the emergence of parasite resistance. With that, other therapeutic strategies are gaining prominence. Among them, immunotherapy and/or immunochemotherapy, which the activation/modulation of the immune system can redirect the host's immune response to an effective therapeutic result. Therefore, this work was designed to assess an immunochemotherapy protocol composed of half course of Miltefosine associated with LBSap vaccine (Milt+LBSap) using the hamster Mesocricetus auratus as an experimental model for VL treatment. When evaluating the main hematobiochemical, immunological and therapeutic efficacy parameters, it was demonstrated that the treatment with Milt+LBSap showed restoration of hematobiochemical condition and reduced serum levels of IgG-anti-Leishmania compared to animals infected non treated (INT). Beyond that, an increase in the number of CD4⁺ lymphocytes producers of IFN-γ in relation to INT or to animals treated with miltefosine during 28 days, and TNF-α increased compared to INT were observed. Also, it was found a reduction of IL-10-production in relation to INT, or animals that received LBSap vaccine only, or miltefosine, following by a reduction in the splenic parasitic burden. These results demonstrate that the immunochemotherapy protocol used can stimulate the immune response, inducing an expressive cellular response sufficient to control spleen parasitism, standing out as a promising proposal for the VL treatment.

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New therapy protocols for treatment of visceral leishmaniasis are requested.

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Immunochemotherapy can strengthen the immune response concomitant with a direct action of the drug against L.infantum.

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Immunochemotherapy with miltefosine plus LBSap vaccine against VL induces activation of cellular response immune.

Phase I and II Clinical Trial Comparing the LBSap, Leishmune®, and Leish-Tec® Vaccines against Canine Visceral Leishmaniasis

In this study, we performed a phase I and II clinical trial in dogs to evaluate the toxicity and immunogenicity of LBSap-vaccine prototype, in comparison to Leishmune® and Leish-Tec® vaccines. Twenty-eight dogs were classified in four groups: (i) control group received 1 mL of sterile 0.9% saline solution; (ii) LBSap group received 600 μg of Leishmania braziliensis promastigotes protein and 1 mg of saponin adjuvant; (iii) Leishmune®; and (iv) Leish-Tec®. The safety and toxicity of the vaccines were measured before and after three immunizations by clinical, biochemical, and hematological parameters. The clinical examinations revealed that some dogs of LBSap and Leishmune® groups presented changes at the site of vaccination inoculum, such as nodules, mild edema, and local pain, which were transient and disappeared seventy-two hours after vaccination, but these results indicate that adverse changes caused by the immunizations are tolerable. The immunogenicity results demonstrate an increase of B lymphocytes CD21+ regarding the Leishmune® group and monocytes CD14+ concerning LBSap and Leishmune® groups. In the in vitro analyses, an increase in lymphoproliferative activity in LBSap and Leishmune® groups was observed, with an increase of antigen-specific CD4+ and CD8+ T lymphocytes in the LBSap group. A second approach of in vitro assays aimed at evaluating the percentage of antigen-specific CD4+ and CD8+ T lymphocytes producers of IFN-γ and IL-4, where an increase in both IFN-γ producing subpopulations in the LBSap group was observed, also showed an increase in IFN-γ producers in CD8+ lymphocytes in the Leish-Tec® group. Our data regarding immunogenicity indicate that the vaccination process, especially with the LBSap vaccine, generated a protective immune response compatible with L. infantum parasite control. Based on the foregoing, the LBSap vaccine would be suitable for further studies of phase III clinical trial in endemic areas with high prevalence and incidence of canine visceral leishmaniasis (VL) cases.

Liver infusion tryptose (LIT): the best choice for growth, viability, and infectivity of Leishmania infantum parasites

Leishmania spp. parasites have a complex biological cycle presenting basically two different morphological stages, the amastigote and promastigote forms. In vitro cultivation allows a more complete study of the biological aspects of these parasites, indicating better conditions for infection, immunoassay tests, drug evaluations, and vaccines. Thus, we evaluated the three most used culture media for Leishmania spp., Grace’s insect cell culture medium (Grace’s), liver infusion tryptose (LIT), and Schneider’s insect medium (Schneider’s), without supplementation or supplemented with fetal calf serum (FCS) and bovine serum albumin (Albumin) to evaluate the growth, viability, and infectivity of the L. infantum promastigotes. It was observed that promastigote forms have a better growth in LIT and Schneider’s with or without FCS when compared to that in Grace’s. The supplementation with albumin promoted greater viability of the parasites independent of the medium. For in vitro infection of J774.A1 macrophages using light microscopy and flow cytometry analyses, FCS-supplemented LIT and Grace’s promoted higher percentage of infected macrophages and parasite load compared with Schneider’s media. Taken together, our results demonstrated that the supplementation of LIT culture medium with FCS is the most suitable strategy to cultivate Leishmania infantum parasites enabling the maintenance of growth and infective parasites for research uses.

In vitro Infectivity of Strains Isolated From Dogs Naturally Infected With Leishmania infantum Present a Distinct Pathogenic Profile in Hamsters

Visceral leishmaniasis (VL) is a severe disease caused by Leishmania infantum. Dogs are the parasite's main reservoir, favoring its transmission in the urban environment. The analysis of L. infantum from infected dogs contributes to the identification of more virulent parasites, thereby supporting basic and applied studies such as vaccinal and therapeutic strategies. We proposed the in vitro and in vivo characterization of L. infantum strains from naturally infected dogs from a VL endemic area based on an infectivity and pathogenicity analysis. DH82 canine macrophages were infected in vitro with different strains for infectivity analysis, showing distinct infectivity profiles. The strains that showed greater and lesser infectivity using in vitro analyses (616 and 614, respectively) were used to infect hamsters for pathogenicity analysis. The group infected with strain 616 showed 100% survival while the group infected with strain 614 showed 50% after seven months of follow up. Furthermore, the 614 strain induced more noticeable clinicopathological changes and biochemical abnormalities in liver function, along with high inflammation and parasite load in the liver and spleen. We confirmed high variability of infectivity and pathogenicity in L. infantum strains from infected dogs. The results support the belief that screening for L. infantum infectivity using in vitro experiments is inadequate when it comes to selecting the most pathogenic strain.

Recent advances and new strategies on leishmaniasis treatment

Leishmaniasis is one of the most important tropical neglected diseases according to the World Health Organization. Even after more than a century, we still have few drugs for the disease therapy and their great toxicity and side effects put in check the treatment control program around the world. Moreover, the emergence of strains resistant to conventional drugs, co-infections such as HIV/Leishmania spp., the small therapeutic arsenal (pentavalent antimonials, amphotericin B and formulations, and miltefosine), and the low investment for the discovery/development of new drugs force researchers and world health agencies to seek new strategies to combat and control this important neglected disease. In this context, the aim of this review is to summarize new advances and new strategies used on leishmaniasis therapy addressing alternative and innovative treatment paths such as physical and local/topical therapies, combination or multi-drug uses, immunomodulation, drug repurposing, and the nanotechnology-based drug delivery systems.Key points• The treatment of leishmaniasis is a challenge for global health agencies.• Toxicity, side effects, reduced therapeutic arsenal, and drug resistance are the main problems.• New strategies and recent advances on leishmaniasis treatment are urgent.• Immunomodulators, nanotechnology, and drug repurposing are the future of leishmaniasis treatment.

Canine visceral leishmaniasis biomarkers and their employment in vaccines

The natural history of canine visceral leishmaniasis (CVL) has been well described, particularly with respect to the parasite load in different tissues and immunopathological changes according to the progression of clinical forms. The biomarkers evaluated in these studies provide support for the improvement of the tools used in developing vaccines against CVL. Thus, we describe the major studies using the dog model that supplies the rationale for including different biomarkers (tissue parasitism, histopathology, hematological changes, leucocytes immunophenotyping, cytokines patterns, and in vitroco-culture systems using purified T-cells subsets and macrophages infected with L. infantum) for immunogenicity and protection evaluations in phases I and II applied to pre-clinical and clinical vaccine trials against CVL. The search for biomarkers related to resistance or susceptibility has revealed a mixed cytokine profile with a prominent proinflammatory immune response as relevant for Leishmania replication at low levels as observed in asymptomatic dogs (highlighted by high levels of IFN-γ and TNF-α and decreased levels in IL-4, TGF-β and IL-10). Furthermore, increased levels in CD4⁺ and CD8⁺ T-cell subsets, presenting intracytoplasmic proinflammatory cytokine balance, have been associated with a resistance profile against CVL. In contrast, a polyclonal B-cell expansion towards plasma cell differentiation contributes to high antibody production, which is the hallmark of symptomatic dogs associated with high susceptibility in CVL. Finally, the different studies used to analyze biomarkers have been incorporated into vaccine immunogenicity and protection evaluations. Those biomarkers identified as resistance or susceptibility markers in CVL have been used to evaluate the vaccine performance against L. infantum in a kennel trial conducted before the field trial in an area known to be endemic for visceral leishmaniasis. This rationale has been a guiding force in the testing and selection of the best vaccine candidates against CVL and provides a way for the veterinary industry to register commercial immunobiological products.

Pharmacokinetics and Tissue Distribution of Benznidazole after Oral Administration in Mice

Specific chemotherapy using benznidazole (BNZ) for Chagas disease during the chronic stage is controversial due to its limited efficacy and toxic effects. Although BNZ has been used to treat Chagas disease since the 1970s, few studies about the biodistribution of this drug exist. In this study, BNZ tissue biodistribution in a murine model and its pharmacokinetic profile in plasma were monitored. A bioanalytical high-performance liquid chromatography method with a UV detector (HPLC-UV) was developed and validated according to the European Medicines Agency for quantification of BNZ in organs and plasma samples prepared by liquid-liquid extraction using ethyl acetate. The developed method was linear in the BNZ concentration, which ranged from 0.1 to 100.0 μg/ml for plasma, spleen, brain, colon, heart, lung, and kidney and from 0.2 to 100.0 μg/ml for liver. Validation assays demonstrated good stability for BNZ under all conditions evaluated. Pharmacokinetic parameters confirmed rapid, but low, absorption of BNZ after oral administration. Biodistribution assays demonstrated different maximum concentrations in organs and similar times to maximum concentration and mean residence times, with means of 40 min and 2.5 h, respectively. Therefore, the biodistribution of BNZ is extensive, reaching organs such as the heart and colon, which are the most relevant organs affected by Trypanosoma cruzi infection, and also the spleen, brain, liver, lungs, and kidneys. Simultaneous analyses of tissues and plasma indicated high BNZ metabolism in the liver. Our results suggest that low bioavailability, instead of inadequate biodistribution, could be responsible for therapeutic failure during the chronic phase of Chagas disease.

A Vaccine Therapy for Canine Visceral Leishmaniasis Promoted Significant Improvement of Clinical and Immune Status with Reduction in Parasite Burden

Herein, we evaluated the treatment strategy employing a therapeutic heterologous vaccine composed of antigens of Leishmania braziliensis associated with MPL adjuvant (LBMPL vaccine) for visceral leishmaniasis (VL) in symptomatic dogs naturally infected by Leishmania infantum. Sixteen dogs received immunotherapy with MPL adjuvant (n = 6) or with a vaccine composed of antigens of L. braziliensis associated with MPL (LBMPL vaccine therapy, n = 10). Dogs were submitted to an immunotherapeutic scheme consisting of 3 series composed of 10 subcutaneous doses with 10-day interval between each series. The animals were evaluated before (T0) and 90 days after treatment (T90) for their biochemical/hematological, immunological, clinical, and parasitological variables. Our major results showed that the vaccine therapy with LBMPL was able to restore and normalize main biochemical (urea, AST, ALP, and bilirubin) and hematological (erythrocytes, hemoglobin, hematocrit, and platelets) parameters. In addition, in an ex vivo analysis using flow cytometry, dogs treated with LBMPL vaccine showed increased CD3⁺ T lymphocytes and their subpopulations (TCD4⁺ and TCD8⁺), reduction of CD21⁺ B lymphocytes, increased NK cells (CD5^-CD16⁺) and CD14⁺ monocytes. Under in vitro conditions, the animals developed a strong antigen-specific lymphoproliferation mainly by TCD4⁺ and TCD8⁺ cells; increasing in both TCD4⁺IFN-γ⁺ and TCD8⁺IFN-γ⁺ as well as reduction of TCD4⁺IL-4⁺ and TCD8⁺IL-4⁺ lymphocytes with an increased production of TNF-α and reduced levels of IL-10. Concerning the clinical signs of canine visceral leishmaniasis, the animals showed an important reduction in the number and intensity of the disease signs; increase body weight as well as reduction of splenomegaly. In addition, the LBMPL immunotherapy also promoted a reduction in parasite burden assessed by real-time PCR. In the bone marrow, we observed seven times less parasites in LBMPL animals compared with MPL group. The skin tissue showed a reduction in parasite burden in LBMPL dogs 127.5 times higher than MPL. As expected, with skin parasite reduction promoted by immunotherapy, we observed a blocking transmission to sand flies in LBMPL dogs with only three positive dogs after xenodiagnosis. The results obtained in this study highlighted the strong potential for the use of this heterologous vaccine therapy as an important strategy for VL treatment.

Clinical, hematological and biochemical alterations in hamster (Mesocricetus auratus) experimentally infected with Leishmania infantum through different routes of inoculation

Background

Leishmaniasis remains among the most important parasitic diseases in the developing world and visceral leishmaniasis (VL) is the most fatal. The hamster Mesocricetus auratus is a susceptible model for the characterization of the disease, since infection of hamsters with L. infantum reproduces the clinical and pathological features of human VL. In this context, it provides a unique opportunity to study VL in its active form. The main goal of this study was to evaluate the clinical, biochemical, and hematological changes in male hamsters infected through different routes and strains of L. infantum.

Methods

In the current study, hamsters (Mesocricetus auratus) were infected with the L. infantum strains (WHO/MHOM/BR/74/PP75 and MCAN/BR/2008/OP46) by intradermal, intraperitoneal and intracardiac routes. The animals were monitored for a nine  month follow-up period.

Results

The hamsters showed clinical signs similar to those observed in classical canine and human symptomatic VL, including splenomegaly, severe weight loss, anemia, and leucopenia. Therefore the OP46 strain was more infective, clinical signs were more frequent and more exacerbated in IC group with 80 to 100 % of the animals showing splenomegaly, in the last month infection. Additionally, desquamation, hair loss and external mucocutaneous lesions and ulcers localized in the snout, accompanied by swelling of the paws in all animals, were observed. Consequently, the animals presented severe weight loss/cachexia, hunched posture, an inability to eat or drink, and non-responsiveness to external stimuli. Furthermore, regardless of strain, route of inoculum and time assessed, the animals showed renal and hepatic alterations, with increased serum levels of urea and creatinine as well as elevated serum levels of aspartate aminotransferase and alanine aminotransferase.

Conclusions

These results strongly suggest that the inoculation through the intracardiac route resulted in a higher severity among infections, especially in the sixth and ninth month after infection via intracardiac, exhibited clinical manifestations and biochemical/hematological findings similar to human visceral leishmaniasis. Therefore, we suggest that this route must be preferentially used in experimental infections for pathogenesis studies of VL in the hamster model.

The TcI and TcII Trypanosoma cruzi experimental infections induce distinct immune responses and cardiac fibrosis in dogs

Trypanosoma cruzi infection may be caused by different strains with distinct discrete typing units (DTUs) that can result in variable clinical forms of chronic Chagas disease. The present study evaluates the immune response and cardiac lesions in dogs experimentally infected with different T. cruzi strains with distinct DTUs, namely, the Colombian (Col) and Y strains of TcI and TcII DTU, respectively. During infection with the Col strain, increased levels of alanine aminotransferase, erythrocytes, haematocrit and haemoglobin were observed. In addition, CD8⁺ T-lymphocytes isolated from the peripheral blood produced higher levels of interleukin (IL)-4. The latter suggests that during the acute phase, infection with the Col strain may remain unnoticed by circulating mononuclear cells. In the chronic phase, a significant increase in the number of inflammatory cells was detected in the right atrium. Conversely, infection with the Y strain led to leucopoenia, thrombopoenia, inversion of the ratio of CD4⁺/CD8⁺ T-lymphocytes and alterations in monocyte number. The Y strain stimulated the production of interferon-γ by CD4⁺ and CD8⁺ T-lymphocytes and IL-4 by CD8⁺ T-cells. In the chronic phase, significant heart inflammation and fibrosis were observed, demonstrating that strains of different DTUs interact differently with the host.

Dogs immunized with LBSap vaccine displayed high levels of IL-12 and IL-10 cytokines and CCL4, CCL5 and CXCL8 chemokines in the dermis

The complex interplay between cytokines and chemokines regulates innate and adaptive immune responses against pathogens; specifically, cytokine and chemokine expression drives activation of immune effector cells and their recruitment to tissue infection sites. Herein, we inoculated dogs with Leishmania braziliensis antigens plus saponin (the LBSap vaccine), as well as with the vaccine components, and then used real-time PCR to evaluate the kinetics of dermal expression of mRNAs of cytokines (IL-12, IFN-γ, TNF-α, IL-4, IL-13, TGF-β and IL-10) and chemokines (CCL2, CCL4, CCL5, CCL21 and CXCL8) 1, 12, 24 and 48 h after inoculation. We also evaluated the correlation between cytokine and chemokine expression and dermal cellularity. The LBSap vaccine induced high levels of IL-12 and IL-10 expression at 12 and 24 h, respectively. Furthermore, we observed positive correlations between IL-12 and IL-13 expression, IFN-γ and IL-13 expression, and IL-13 and TGF-β expression, suggesting that a mixed cytokine microenvironment developed after immunization with the vaccine. Inoculation with the saponin adjuvant alone induced a chemokine and cytokine expression profile similar to that observed in the LBSap group. CCL4 and CXCL8 chemokine expression was up regulated by the LBSap vaccine. CCL5 expression was initially highest in the LBSap group, but at 48 h, expression was highest in the LB group. Information about the kinetics of the immune response to this vaccine gained using this dog model will help to elucidate the mechanisms of and factors involved in a protective response against Leishmania infection and will aid in establishing rational approaches for the development of vaccines against canine visceral leishmaniasis.

Parasite burden in hamsters infected with two different strains of leishmania (Leishmania) infantum: "Leishman Donovan units" versus real-time PCR

To develop and test new therapeutics and immune prophylaxis strategies for visceral leishmaniasis (VL), understanding tissue parasitism evolution after experimental infection with Leishmania infantum is important. Experimental infection in a hamster model (Mesocricetus auratus) reproduces several typical aspects of canine and human VL that are closely related to the inoculum’s route. We quantified the parasitism in the liver and spleen of hamsters experimentally infected by various routes (intradermal, intraperitoneal, and intracardiac [IC]) and different strains of L. infantum (MHOM/BR/74/PP75 and Wild) and compared two different methodologies to evaluate tissue parasitism (Leishman Donovan units [LDU] and real-time qPCR). In addition, the quantification of specific total-IgG in the serum of uninfected and infected hamsters was determined by ELISA. The animals were followed for 1, 3, 6 and 9 months post-infection for survival analysis. We found that infection with the Wild strain by the IC route resulted in higher mortality. Positive antibody (IgG) responses were detected with higher peaks at 6 and 9 months in the IC group inoculated with PP75 strain. However, in animals infected with the Wild strain the IgG levels were elevated in all infected groups during all the time evaluated. We also observed by LDU analysis that the IC route lead to higher parasitism in the liver and spleen with both strains. Furthermore, qPCR showed higher sensitivity for identifying animals with low parasitic burden. In conclusion, qPCR can be useful for assessing parasitism in the spleen and liver of a hamster model infected with L. infantum independent of the route of infection, and this technique may become an essential tool for assessing parasite density in the hamster model after experimental treatment or immunization with potential vaccine candidates.