Mixed Formulation of Conventional and Pegylated Meglumine Antimoniate-Containing Liposomes Reduces Inflammatory Process and Parasite Burden in Leishmania infantum-Infected BALB/c Mice

CD4+ Th1 and Th17 responses and multifunctional CD8 T lymphocytes associated with cure or disease worsening in human visceral leishmaniasis

Introduction

In VL, a proinflammatory phenotype is typically associated with enhanced phagocytosis and a Th1 mediated immune response resulting in infection control. In contrast, an anti-inflammatory phenotype, associated with a predominant regulatory response, typically enables intracellular multiplication of Leishmania parasites and disease progression.

Methods

To investigate the impact of chemotherapy on Th2 and Th17 immune responses in patients with visceral leishmaniasis (VL), we assessed all combinations of intracellular expression of IFN-γ, IL-10, IL-4 and IL-17 in the CD4+ and CD8+ T cell populations of peripheral blood mononuclear cell (PBMC) samples from patients, after antigenic stimulation with Leishmania lysate, throughout treatment and follow-up. As increases in spleen and liver sizes and decreases in hematocrit, hemogloblin, erythrocytes, monocytes, leukocytes and platelets levels are strongly related to the disease, we studied the correlations between the frequencies of T cells producing the afore mentioned cytokines, individually and in combination, and these variables, as markers of disease or cure.

Results

We found that the frequency of IFN-γ-producingCD4+ T cells increased until the end of chemotherapy with Glucantime® or AmBisome ®, while IL-10, IL-4 and IL-17-producing CD4+ T cells peaked on day 7 following the start of treatment. Although the frequency of CD4+IL-17+ cells decreased during treatment an increase was observed after clinical cure. The frequency of CD4+ T cells producing only IFN-γ or IL-17 correlated with blood monocytes levels. Frequencies of double-producers of IFN-γ and IL-10 or IL-4 correlated positively with eosinophils and platelets levels. Together, this suggest that IFN-γ drives the immune response towards Th1 at cure. In contrast, and associated with disease or Th2 response, the frequency of CD4+ IL-10+ cells correlated positively with spleen sizes and negatively with circulating monocyte levels, while the frequency of CD4+ producing both IL-4 and IL-10 correlated negatively with platelets levels. The frequency of CD8+ single-producers of IFN-γ increased from day 21 to 90 while that of single-producers of IL-10 peaked on day 7, of IL-4 on day 30 and of IL-17, on day 180. IFN-γ expression in CD8+ single- and double-producers of cytokines was indicative of an immune response associated with cure. In contrast, frequencies of CD8+ double-producers of IL-4 and IL-10, IL-4 and IL-17 and IL-10 and IL-17 and producers of three and four cytokines, were associated with disease and were low after the cure. Frequencies of CD8+ T cells producing IFN-γ alone or with IL-17 were positively correlated with platelets levels. In contrast, as markers of disease: 1) frequencies of single producers of IL-10 correlated negatively with leukocytes levels, 2) frequencies of double producers of IL-4 and IL-10 correlated negatively with platelet, leukocyte, lymphocyte and circulating monocyte levels, 3) frequencies of triple-producers of IFN-γ, IL-4 and IL-10 correlated negatively with platelet, leukocyte and neutrophil levels and 4) frequencies of producers of IFN-γ, IL-4, IL-10 and IL-17 simultaneously correlated positively with spleen size, and negatively with leukocyte and neutrophil levels.

Discussion

Our results confirmed that the clinical improvement of VL patients correlates with the decrease of an IL-4 and IL-10 CD4+Th2 response, the recovery of CD4+ Th1 and Th17 responses and the frequency of CD8+ single-producers of IFN-γ and double producers of IFN-γ and IL-17.

The Use of an Adjuvant System Improves Innate and Adaptive Immune Response When Associated with a Leishmania (Viannia) braziliensis Antigen in a Vaccine Candidate against L. (Leishmania) infantum Infection

BACKGROUND

The adjuvants' optimal dose and the administration route can directly influence the epitope recognition patterns and profiles of innate response. We aimed to establish the effect and the optimal dose of adjuvant systems for proposing a vaccine candidate to be employed with Leishmania (Viannia) braziliensis.

METHODS

We evaluated the adjuvants saponin (SAP), monophosphoryl lipid A (MPL) and resiquimod (R-848) isolated and combined as adjuvant systems in a lower dose corresponding to 25%, 33%, and 50% of each adjuvant total dose. Male outbred BALB/c mice were divided into 13 groups, SAP, MPL, and R-848 isolated, and the adjuvant systems SAP plus MPL (SM), SAP plus R-848 (SR), and MPL plus R-848 (MR).

RESULTS

SM50 increased levels of all chemokines analyzed and TNF production, while it presented an increased inflammatory cell infiltrate in the skin with macrophage recruitment. Thus, we proposed a vaccine candidate employing L. (V.) braziliensis antigen associated with the SM adjuvant system against experimental L. (Leishmania) infantum challenge. We observed a significant increase in the frequency of cells expressing the central and effector memory CD4⁺ T cells phenotype in immunized mice with the LBSM50. In the liver, there was a decreased parasite load when mice received LBSM50.

CONCLUSIONS

When combined with L. (V.) braziliensis antigen, SM50 increases TNF and IFN-γ, which generates central and effector memory CD4⁺ T cells. Therefore, using an adjuvant system can promote an effective innate immune response with the potential to compose future vaccines.

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.

Repositioning of Tamoxifen in Surface-Modified Nanocapsules as a Promising Oral Treatment for Visceral Leishmaniasis

Standards of care for human visceral leishmaniasis (VL) are based on drugs used parenterally, and oral treatment options are urgently needed. In the present study, a repurposing strategy was used associating tamoxifen (TMX) with polyethylene glycol-block-polylactide nanocapsules (NC) and its anti-leishmanial efficacy was reported in vivo. Stable surface modified-NC (5 mg/mL of TMX) exhibited 200 nm in size, +42 mV of zeta potential, and 98% encapsulation efficiency. Atomic force microscopy evidenced core-shell-NC. Treatment with TMX-NC reduced parasite-DNA quantified in liver and spleen compared to free-TMX; and provided a similar reduction of parasite burden compared with meglumine antimoniate in mice and hamster models. Image-guided biodistribution showed accumulation of NC in liver and spleen after 30 min post-administration. TMX-NC reduced the number of liver granulomas and restored the aspect of capsules and trabeculae in the spleen of infected animals. TMX-NC was tested for the first time against VL models, indicating a promising formulation for oral treatment.

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.

Berberine-Loaded Liposomes for the Treatment of Leishmania infantum-Infected BALB/c Mice

Berberine (BER)—an anti-inflammatory quaternary isoquinoline alkaloid extracted from plants—has been reported to have a variety of biologic properties, including antileishmanial activity. This work addresses the preparation of BER-loaded liposomes with the aim to prevent its rapid liver metabolism and improve the drug selective delivery to the infected organs in visceral leishmaniasis (VL). BER liposomes (LP-BER) displayed a mean size of 120 nm, negative Z-potential of −38 mV and loaded 6 nmol/μmol lipid. In vitro, the loading of BER in liposomes enhanced its selectivity index more than 7-fold by decreasing its cytotoxicity to macrophages. In mice, LP-BER enhanced drug accumulation in the liver and the spleen. Consequently, the liposomal delivery of the drug reduced parasite burden in the liver and spleen by three and one logarithms (99.2 and 93.5%), whereas the free drug only decreased the infection in the liver by 1-log. The organ drug concentrations—far from IC₅₀ values— indicate that BER immunomodulatory activity or drug metabolites also contribute to the efficacy. Although LP-BER decreased 10-fold—an extremely rapid clearance of the free drug in mice—the value remains very high. Moreover, LP-BER reduced plasma triglycerides levels.

Therapeutic Efficacy of a Mixed Formulation of Conventional and PEGylated Liposomes Containing Meglumine Antimoniate, Combined with Allopurinol, in Dogs Naturally Infected with Leishmania infantum

The treatment of dogs naturally infected with Leishmania infantum using meglumine antimoniate (MA) encapsulated in conventional liposomes (LC) in association with allopurinol has been previously reported to promote a marked reduction in the parasite burden in the main infection sites. Here, a new assay in naturally infected dogs was performed using a novel liposome formulation of MA consisting of a mixture of conventional and long-circulating (PEGylated) liposomes (LCP), with expected broader distribution among affected tissues of the mononuclear phagocyte system. Experimental groups of naturally infected dogs were as follows: LCP plus Allop, receiving LCP intravenously as 2 cycles of 6 doses (6.5 mg Sb/kg of body weight/dose) at 4-day intervals plus allopurinol at 30 mg/kg/12 h per os (p.o.) during 130 days (LCP+Allop); LC plus Allop, receiving LC intravenously as 2 cycles of 6 doses (6.5 mg Sb/kg/dose) plus allopurinol during 130 days (LC+Allop); Allop, treated with allopurinol only; and a nontreated control. Parasite loads were evaluated by quantitative PCR in liver, spleen, and bone marrow tissue and by immunohistochemistry in the ear skin, before treatment, just after treatment, and 4 months later. The LCP+Allop and LC+Allop groups, but not the Allop group, showed significant suppression of the parasites in the liver, spleen, and bone marrow 4 months after treatment compared to the pretreatment period or the control group. Only LCP+Allop group showed significantly lower parasite burden in the skin in comparison to the control group. On the basis of clinical staging and parasitological evaluations, the LCP formulation exhibited a more favorable therapeutic profile than the LC one, being therefore promising for the treatment of canine visceral leishmaniasis.

Chimeric Vaccines Designed by Immunoinformatics-Activated Polyfunctional and Memory T Cells That Trigger Protection against Experimental Visceral Leishmaniasis

Many vaccine candidates against visceral leishmaniasis (VL) have been proposed; however, to date, none of them have been efficacious for the human or canine disease. On this basis, the design of leishmaniasis vaccines has been constantly changing, and the use of approaches to select specific epitopes seems to be crucial in this scenario. The ability to predict T cell-specific epitopes makes immunoinformatics an even more necessary approach, as in VL an efficient immune response against the parasite is triggered by T lymphocytes in response to Leishmania spp. immunogenic antigens. Moreover, the success of vaccines depends on the capacity to generate long-lasting memory and polyfunctional cells that are able to eliminate the parasite. In this sense, our study used a combination of different approaches to develop potential chimera candidate vaccines against VL. The first point was to identify the most immunogenic epitopes of Leishmania infantum proteins and construct chimeras composed of Major histocompatibility complex (MHC) class I and II epitopes. For this, we used immunoinformatics features. Following this, we validated these chimeras in a murine model in a thorough memory study and multifunctionality of T cells that contribute to a better elucidation of the immunological protective mechanisms of polyepitope vaccines (chimera A and B) using multicolor flow cytometry. Our results showed that in silico-designed chimeras can elicit polyfunctional T cells producing T helper (Th)1 cytokines, a strong immune response against Leishmania antigen, and the generation of central and effector memory T cells in the spleen cells of vaccinated animals that was able to reduce the parasite burden in this organ. These findings contribute two potential candidate vaccines against VL that can be used in further studies, and help in this complex field of vaccine development against this challenging parasite.

In vitro and in vivo immunomodulatory properties of octyl-β-D-galactofuranoside during Leishmania donovani infection

BACKGROUND

The chemotherapeutic arsenal available to treat visceral leishmaniasis is currently limited, in view of many drawbacks such as high cost, toxicity or emerging resistance. New therapeutic strategies are particularly needed to improve the management and the outcome in immunosuppressed patients. The combination of an immunomodulatory drug to a conventional anti-Leishmania treatment is an emerging concept to reverse the immune bias from Th2 to Th1 response to boost healing and prevent relapses.

METHODS

Here, immunostimulating and leishmanicidal properties of octyl-β-D-galactofuranose (Galf) were assessed in human monocyte-derived macrophages (HM) and in a murine model, after challenge with Leishmania donovani promastigotes. We recorded parasite loads and expression of various cytokines and immune effectors in HM and mouse organs (liver, spleen, bone marrow), following treatment with free (Galf) and liposomal (L-Galf) formulations.

RESULTS

Both treatments significantly reduced parasite proliferation in HM, as well as liver parasite burden in vivo (Galf, P < 0.05). Consistent with in vitro results, we showed that Galf- and L-Galf-treated mice displayed an enhanced Th1 immune response, particularly in the spleen where pro-inflammatory cytokines TNF-α, IL-1β and IL-12 were significantly overexpressed compared to control group. The hepatic recruitment of myeloid cells was also favored by L-Galf treatment as evidenced by the five-fold increase of myeloperoxidase (MPO) induction, which was associated with a higher number of MPO-positive cells within granulomas. By contrast, the systemic level of various cytokines such as IL-1β, IL-6, IL-17A or IL-27 was drastically reduced at the end of treatment.

CONCLUSIONS

Overall, these results suggest that Galf could be tested as an adjuvant in combination with current anti-parasitic drugs, to restore an efficient immune response against infection in a model of immunosuppressed mice.

Development and evaluation of novel miltefosine-polyphenol co-loaded second generation nano-transfersomes for the topical treatment of cutaneous leishmaniasis

Objective: To test the hypothesis that miltefosine (MTF)-polyphenol co-loaded second-generation nano-transfersomes (SGNTs) can be an effective approach for the topical treatment of cutaneous leishmaniasis (CL).Methods: The co-loaded SGNTs with various MTF-polyphenol combinations were developed, evaluated and compared for the entrapment efficiency, vesicle size, deformability index, ex-vivo permeation, cytotoxicity, and anti-leishmanial potential, using both in-vitro and in-vivo models.Results: The co-loaded SGNTs were spherical in shape, with an average size of 119 ± 1.5 nm and a high entrapment efficiency of 73.7 ± 3.7%. The ex-vivo study displayed a 3.2-fold higher permeation of MTF when entrapped in co-loaded SGNTs, whereas cytotoxicity potential of co-loaded SGNTs was 43.2% higher than the MTF solution. A synergistic interaction was observed between MTF and apigenin (APG) among all polyphenols and an 8.0-fold lower IC₅₀ was found against amastigotes of DsRed Leishmania mexicana, compared with the plain MTF solution. Moreover, the in-vivo studies displayed a 9.5-fold reduced parasitic burden in the L. mexicana infected BALB/c mice treated with MTF-APG co-loaded SGNTs gel.Conclusions: The potential of MTF-APG co-loaded SGNTs topical formulation is established for the first time as an effective drug delivery strategy against CL.

Synthetic Peptides Elicit Strong Cellular Immunity in Visceral Leishmaniasis Natural Reservoir and Contribute to Long-Lasting Polyfunctional T-Cells in BALB/c Mice

Reverse vaccinology or immunoinformatics is a computational methodology which integrates data from in silico epitope prediction, associated to other important information as, for example, the predicted subcellular location of the proteins used in the design of the context of vaccine development. This approach has the potential to search for new targets for vaccine development in the predicted proteome of pathogenic organisms. To date, there is no effective vaccine employed in vaccination campaigns against visceral leishmaniasis (VL). For the first time, herein, an in silico, in vitro, and in vivo peptide screening was performed, and immunogenic peptides were selected to constitute VL peptide-based vaccines. Firstly, the screening of in silico potential peptides using dogs naturally infected by L. infantum was conducted and the peptides with the best performance were selected. The mentioned peptides were used to compose Cockt-1 (cocktail 1) and Cockt-2 (cocktail 2) in combination with saponin as the adjuvant. Therefore, tests for immunogenicity, polyfunctional T-cells, and the ability to induce central and effector memory in T-lymphocytes capacity in reducing the parasite load on the spleen for Cockt-1 and Cockt-2 were performed. Among the vaccines under study, Cockt-1 showed the best results, eliciting CD4⁺ and CD8⁺ polyfunctional T-cells, with a reduction in spleen parasitism that correlates to the generation of T CD4⁺ central memory and T CD8⁺ effector memory cells. In this way, our findings corroborate the use of immunoinformatics as a tool for the development of future vaccines against VL.

Behavior of two Leishmania infantum strains-evaluation of susceptibility to antimonials and expression of microRNAs in experimentally infected J774 macrophages and in BALB/c mice

Strains of the same Leishmania parasite species, isolated from different host organisms, may exhibit unique infection profiles and induce a change in the expression of microRNAs among host macrophages and in model host mice. MicroRNAs (MiR) are endogenous molecules of about 22 nucleotides that are involved in many regulatory processes, including the vertebrate host immune response. In this respect, the infectivity and susceptibility to antimonials of two L. infantum strains, BH46, isolated from human, and OP46, isolated from symptomatic dog, were characterized in J774 macrophages and BALB/c mice. Parasite burden was assessed in the liver, spleen, and bone marrow using the serial limiting dilution technique. A higher parasite burden was observed in the spleen and bone marrow of animals infected with OP46 compared to BH46 strain. Our results also showed that OP46 was less susceptible to the antimonials. In addition, miR-122 and miR-155 expression was evaluated in the liver and J774 macrophages, and in spleens from infected animals, respectively. An increase was observed in the expression of miR-155 in J774 macrophages infected with both strains compared to uninfected cells, with a higher expression in cells infected with OP46. However, no difference in the expression of miR-122 and miR-155 was observed in the infected animals. Thus, this study shows that OP46 was more infective for mice, it caused a higher increase in miR-155 expression in infected macrophages and was less susceptible to the antimonials evaluated. These data suggest that alteration in miR-155 level likely plays a role in regulating the response to L. infantum.