Immunotherapy in treatment of leishmaniasis

Monoclonal antibodies: From magic bullet to precision weapon

Monoclonal antibodies (mAbs) are used to prevent, detect, and treat a broad spectrum of non-communicable and communicable diseases. Over the past few years, the market for mAbs has grown exponentially with an expected compound annual growth rate (CAGR) of 11.07% from 2024 (237.64 billion USD estimated at the end of 2023) to 2033 (679.03 billion USD expected by the end of 2033). Ever since the advent of hybridoma technology introduced in 1975, antibody-based therapeutics were realized using murine antibodies which further progressed into humanized and fully human antibodies, reducing the risk of immunogenicity. Some benefits of using mAbs over conventional drugs include a drastic reduction in the chances of adverse reactions, interactions between drugs, and targeting specific proteins. While antibodies are very efficient, their higher production costs impede the process of commercialization. However, their cost factor has been improved by developing biosimilar antibodies as affordable versions of therapeutic antibodies. Along with the recent advancements and innovations in antibody engineering have helped and will furtherly help to design bio-better antibodies with improved efficacy than the conventional ones. These novel mAb-based therapeutics are set to revolutionize existing drug therapies targeting a wide spectrum of diseases, thereby meeting several unmet medical needs. This review provides comprehensive insights into the current fundamental landscape of mAbs development and applications and the key factors influencing the future projections, advancement, and incorporation of such promising immunotherapeutic candidates as a confrontation approach against a wide list of diseases, with a rationalistic mentioning of any limitations facing this field.

N6-methyltubercidin gives sterile cure in a cutaneous Leishmania amazonensis mouse model

Leishmania is a trypanosomatid parasite that causes skin lesions in its cutaneous form. Current therapies rely on old and expensive drugs, against which the parasites have acquired considerable resistance. Trypanosomatids are unable to synthesize purines relying on salvaging from the host, and nucleoside analogues have emerged as attractive antiparasitic drug candidates. 4-Methyl-7-β-D-ribofuranosyl-7H-pyrrolo[2,3-d]pyrimidine (CL5564), an analogue of tubercidin in which the amine has been replaced by a methyl group, demonstrates activity against Trypanosoma cruzi and Leishmania infantum. Herein, we investigated its in vitro and in vivo activity against L. amazonensis. CL5564 was 6.5-fold (P = 0.0002) more potent than milteforan™ (ML) against intracellular forms in peritoneal mouse macrophages, and highly selective, while combination with ML gave an additive effect. These results stimulated us to study the activity of CL5564 in mouse model of cutaneous Leishmania infection. BALB/c female and male mice infected by L. amazonensis treated with CL5564 (10 mg kg−1, intralesional route for five days) presented a >93% reduction of paw lesion size likely ML given orally at 40 mg kg−1, while the combination (10 + 40 mg kg−1 of CL5564 and ML, respectively) caused >96% reduction. The qPCR confirmed the suppression of parasite load, but only the combination approach reached 66% of parasitological cure. These results support additional studies with nucleoside derivatives.

Maltodextrin-Nanoparticles as a Delivery System for Nasal Vaccines: A Review Article

Nanoparticles are increasingly being studied as antigen delivery systems for immunization with nasal vaccines. The addition of adjuvants is still generally required in many nanoparticle formulations, which can induce potential side effects owing to mucosal reactogenicity. In contrast, maltodextrin nanoparticles do not require additional immunomodulators, and have been shown to be efficient vaccine delivery systems. In this review, the development of maltodextrin nanoparticles is presented, specifically their physico-chemical properties, their ability to load antigens and deliver them into airway mucosal cells, and the extent to which they trigger protective immune responses against bacterial, viral, and parasitic infections. We demonstrate that the addition of lipids to maltodextrin nanoparticles increases their potency as a vaccine delivery system for nasal administration.

A novel outlook in the delivery of artemisinin: production and efficacy in experimental visceral leishmaniasis

The visceral form of leishmaniasis (VL), due to infection by Leishmania infantum, is a neglected tropical disease. The accessible therapeutic options are limited. Artemisinin is an efficient antileishmanial product with poor biological availability that requires high repetition of therapeutic doses in VL. Solid lipid nanoparticles (SLNs) provide targeted delivery, increase bioavailability and reduce toxicity of the traditional therapeutic strategy. The spherical shape artemisinin-loaded SLNs were prepared in a particle diameter of 222.0 ± 14.0 nm. The SLNs showed no particular toxic effect on the parasites, whereas the native artemisinin demonstrated a significant toxicity rate of 31% in viability of the promastigotes at the 250 µg/ml concentration. The therapeutic efficacy of the artemisinin-loaded SLNs was demonstrated in the experimental VL, using the L. infantum-infected BALB/c mice, in the present study. The 10 and 20 mg/kg doses of artemisinin-loaded SLNs showed higher level of antileishmanial efficacy compared with the free artemisinin. There was a significant diminishing of the parasite burden in liver (84.7 ± 4.9%) and spleen (85.0 ± 3.1%) and hepatosplenomegaly by the artemisinin-loaded SLNs treated at 20 mg/kg compared to the free artemisinin. Therefore, the present study supports the superior efficacy of artemisinin-loaded SLNs over the free artemisinin and could be considered as a new therapeutic strategy in the treatment of leishmaniasis.

S. Marinho V, H. Holanda F, M. Ferreira I, Oliveira da Silva E. Polymeric nanoparticles containing kojic acid induce structural alterations and apoptosis-like death in Leishmania (Leishmania) amazonensis

Leishmaniasis encompasses a cluster of neglected tropical diseases triggered by kinetoplastid phatogens belonging to the genus Leishmania. Current therapeutic approaches are toxic, expensive, and require long-term treatment. Nanoparticles are emerging as a new alternative for the treatment of neglected tropical diseases. Silk Fibroin is a biocompatible and amphiphilic protein that can be used for formulating nanoemulsions, while kojic acid is a secondary metabolite with antileishmanial actions. Thus, this study evaluated the efficacy of a nanoemulsion, formulated with silk fibroin as the surfactant and containing kojic acid (NanoFKA), against promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. The NanoFKA had an average particle size of 176 nm, Polydispersity Index (PDI) of 0.370, and a Zeta Potential of -32.3 mV. It presented inhibitory concentration (IC50) values of >56 μg/mL and >7 μg/mL for the promastigote and amastigote forms, respectively. Ultrastructural analysis, cell cycle distribution and phosphatidylserine exposure showed that NanoFKA treatment induces apoptosis-like cell death and cell cycle arrest in L. (L.) amazonensis. In addition, NanoFKA exhibited no cytotoxicity against macrophages. Given these results, NanoFKA present leishmanicidal activity against L. (L.) amazonensis.

The association between rLiHyp1 protein plus adjuvant and amphotericin B is an effective immunotherapy against visceral leishmaniasis in mice

Treatment of visceral leishmaniasis (VL) is compromised by drug toxicity, high cost and/or the emergence of resistant strains. Though canine vaccines are available, there are no licensed prophylactic human vaccines. One strategy to improve clinical outcome for infected patients is immunotherapy, which associates a chemotherapy that acts directly to reduce parasitism and the administration of an immunogen-adjuvant that activates the host protective Th1-type immune response. In this study, we evaluated an immunotherapy protocol in a murine model by combining recombinant (r)LiHyp1 (a hypothetical amastigote-specific Leishmania protein protective against Leishmania infantum infection), with monophosphoryl-lipid A (MPLA) as adjuvant and amphotericin B (AmpB) as reference antileishmanial drug. We used this protocol to treat L. infantum infected-BALB/c mice, and parasitological, immunological and toxicological evaluations were performed at 1 and 30 days after treatment. Results showed that mice treated with rLiHyp1/MPLA/AmpB presented the lowest parasite burden in all organs evaluated, when both a limiting dilution technique and qPCR were used. In addition, these animals produced higher levels of IFN-γ and IL-12 cytokines and IgG2a isotype antibody, which were associated with lower production of IL-4 and IL-10 and IgG1 isotype. Furthermore, low levels of renal and hepatic damage markers were found in animals treated with rLiHyp1/MPLA/AmpB possibly reflecting the lower parasite load, as compared to the other groups. We conclude that the rLiHyp1/MPLA/AmpB combination could be considered in future studies as an immunotherapy protocol to treat against VL.

Efficacy of an Immunotherapy Combining Immunogenic Chimeric Protein Plus Adjuvant and Amphotericin B against Murine Visceral Leishmaniasis

Visceral leishmaniasis (VL) in the Americas is a chronic systemic disease caused by infection with Leishmania infantum parasites. The toxicity of antileishmanial drugs, long treatment course and limited efficacy are significant concerns that hamper adequate treatment against the disease. Studies have shown the promise of an immunotherapeutics approach, combining antileishmanial drugs to reduce the parasitism and vaccine immunogens to activate the host immune system. In the current study, we developed an immunotherapy using a recombinant T cell epitope-based chimeric protein, ChimT, previously shown to be protective against Leishmania infantum, with the adjuvant monophosphoryl lipid A (MPLA) and amphotericin B (AmpB) as the antileishmanial drug. BALB/c mice were infected with L. infantum stationary promastigotes and later they received saline or were treated with AmpB, MPLA, ChimT/Amp, ChimT/MPLA or ChimT/MPLA/AmpB. The combination of ChimT/MPLA/AmpB significantly reduced the parasite load in mouse organs (p < 0.05) and induced a Th1-type immune response, which was characterized by higher ratios of anti-ChimT and anti-parasite IgG2a:IgG1 antibodies, increased IFN-γ mRNA and IFN-γ and IL-12 cytokines and accompanied by lower levels of IL-4 and IL-10 cytokines, when compared to other treatments and controls (all p < 0.05). Organ toxicity was also lower with the ChimT/MPLA/AmpB immunotherapy, suggesting that the inclusion of the vaccine and adjuvant ameliorated the toxicity of AmpB to some degree. In addition, the ChimT vaccine alone stimulated in vitro murine macrophages to significantly kill three different internalized species of Leishmania parasites and to produce Th1-type cytokines into the culture supernatants. To conclude, our data suggest that the combination of ChimT/MPLA/AmpB could be considered for further studies as an immunotherapy for L. infantum infection.

Leishmania Animal Models Used in Drug Discovery: A Systematic Review

Many different animal models are in use for drug development for leishmaniasis, but a universal model does not exist. There is a plethora of models, and this review assesses their design, quality, and limitations, including the attention paid to animal welfare in the study design and execution. A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines of available literature after the year 2000 describing animal models for leishmaniasis. The risk of bias was determined using the SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE) risk of bias assessment tool. A total of 10,980 records were initially identified after searching the databases PubMed, EMBASE, LILACS, and SciELO. Based on the application of predetermined exclusion and inclusion criteria, a total of 203 papers describing 216 animal experiments were available for full analysis. Major reasons for exclusion were a lack of essential study information or appropriate ethical review and approval. Mice (82.8%; an average of 35.9 animals per study) and hamsters (17.1%; an average of 7.4 animals per study) were the most frequently used animals, mostly commercially sourced, in the included studies. All studies lacked a formal sample size analysis. The promastigote stages of L. amazonensis or L. major were most frequently used to establish experimental infections (single inoculum). Animal welfare was poorly addressed in all included studies, as the definition of a human end-point or consideration of the 3Rs (Replacement, Reduction, Refinement) was hardly addressed. Most animals were euthanized at the termination of the experiment. The majority of the studies had an unknown or high risk of bias. Animal experiments for drug development for leishmaniasis mainly poorly designed and of low quality, lack appropriate ethical review, and are deficient in essential information needed to replicate and interpret the study. Importantly, aspects of animal welfare are hardly considered. This underpins the need to better consider and record the details of the study design and animal welfare.

Effective immuno-therapeutic treatment of Canine Leishmaniasis

BACKGROUND

Canine Leishmaniasis (CanL) caused by the L. infantum species is one of the biggest threats to the health of the South American canine population. Chemotherapeutics currently used for the treatment of CanL fail to induce a total parasite clearance while inducing numerous side effects. As CanL is an immunomodulated disease, the use of immuno-treatments should strengthen the deficient immune response of infected dogs. In this study, we evaluated a nasally administered immunotherapy in dogs naturally infected with L. infantum (stage 2), with both visceral and cutaneous manifestations. Noteworthy, some of them were also infected by other parasites (E. canis, D. immitis, A. platys), what worsen their chance of survival.

METHODOLOGY/PRINCIPAL FINDINGS

The treatment was based on 2 intranasal (IN.) administrations of a killed L. infantum parasite loaded into maltodextrin nanoparticles, which treatment was compared with the classical oral administration of Miltefosine (2 mg/kg) for 28 days, as well as a combination of these 2 treatments. The results showed that two IN administrations significantly reduced the serology, and were at least as efficient as the chemotherapy to reduce the skin and bone marrow parasite burden, as well as clinical scores, and that unlike Miltefosine treatments, this nasally administered nanoparticle vaccine was without side effects.

CONCLUSIONS

These results confirm the feasibility of a simple therapeutic immuno-treatment against L. infantum infected dogs, which is a promising tool for future developments.

Synthetic hydrazones: In silico studies and in vitro evaluation of the antileishmania potential

Bioprospecting and synthesis of strategically designed molecules have been used in the search for drugs that can be in leishmaniasis. Hydrazones (HDZ) are promising compounds with extensive biological activities. The objective of this work was to perform in silico studies of hydrazones 1-5 and to evaluate their antileishmanial, cytotoxic and macrophage immunomodulatory potential in vitro. Hydrazones were subjected to prediction and molecular docking studies. Antileishmanial protocols on promastigotes and amastigotes of Leishmania amazonensis, cytotoxicity and macrophage immunomodulatory activity were performed. Hydrazones showed a good pharmacokinetic profile and hydrazone 3 and hydrazone 5 were classified as non-carcinogenic. Hydrazone 5 obtained the best conformation with trypanothione reductase. Hydrazone 1 and hydrazone 3 obtained the best mean inhibitory concentration (IC₅₀) values for promastigotes, 4.4-61.96 μM and 8.0-58.75 μM, respectively. It also showed good activity on intramacrophagic amastigotes, with hydrazone 1 being the most active (IC₅₀ = 6.79 μM) with selectivity index of 56. In cytotoxicity to macrophages hydrazone 3 was the most cytotoxic (CC₅₀ = 256.3 ± 0,04 μM), while hydrazone 4 the least (CC₅₀ = 1055.9 ± 0.03 μM). It can be concluded that the hydrazones revealed important pharmacokinetic and toxicological properties, in addition to antileishmania potential in reducing infection and infectivity in parasitized macrophages.

Leishmanicidal Activity of Guanidine Derivatives against Leishmania infantum

Leishmaniasis is a neglected tropical infectious disease with thousands of cases annually; it is of great concern to global health, particularly the most severe form, visceral leishmaniasis. Visceral leishmaniasis treatments are minimal and have severe adverse effects. As guanidine-bearing compounds have shown antimicrobial activity, we analyzed the cytotoxic effects of several guanidine-bearing compounds on Leishmania infantum in their promastigote and amastigote forms in vitro, their cytotoxicity in human cells, and their impact on reactive nitrogen species production. LQOFG-2, LQOFG-6, and LQOFG-7 had IC50 values of 12.7, 24.4, and 23.6 µM, respectively, in promastigotes. These compounds exhibited cytotoxicity in axenic amastigotes at 26.1, 21.1, and 18.6 µM, respectively. The compounds showed no apparent cytotoxicity in cells from healthy donors. To identify mechanisms of action, we evaluated cell death processes by annexin V and propidium iodide staining and nitrite production. Guanidine-containing compounds caused a significant percentage of death by apoptosis in amastigotes. Independent of L. infantum infection, LQOFG-7 increased nitrite production in peripheral blood mononuclear cells, which suggests a potential mechanism of action for this compound. Therefore, these data suggest that guanidine derivatives are potential anti-microbial molecules, and further research is needed to fully understand their mechanism of action, especially in anti-leishmanial studies.

Immunotherapy Using Immunogenic Mimotopes Selected by Phage Display plus Amphotericin B Inducing a Therapeutic Response in Mice Infected with Leishmania amazonensis

Leishmania amazonensis can cause cutaneous and visceral clinical manifestations of leishmaniasis in infected hosts. Once the treatment against disease is toxic, presents high cost, and/or there is the emergence of parasite-resistant strains, alternative means through which to control the disease must be developed. In this context, immunotherapeutics combining known drugs with immunogens could be applied to control infections and allow hosts to recover from the disease. In this study, immunotherapeutics protocols associating mimotopes selected by phage display and amphotericin B (AmpB) were evaluated in L. amazonensis-infected mice. Immunogens, A4 and A8 phages, were administered alone or associated with AmpB. Other animals received saline, AmpB, a wild-type phage (WTP), or WTP/AmpB as controls. Evaluations performed one and thirty days after the application of immunotherapeutics showed that the A4/AmpB and A8/AmpB combinations induced the most polarized Th1-type immune responses, which reflected in significant reductions in the lesion's average diameter and in the parasite load in the infected tissue and distinct organs of the animals. In addition, the combination also reduced the drug toxicity, as compared to values found using it alone. In this context, preliminary data presented here suggest the potential to associate A4 and A8 phages with AmpB to be applied in future studies for treatment against leishmaniasis.

Unraveling the role of natural killer cells in leishmaniasis

NK cells are known as frontline responders that are efficient in combating several maladies as well as leishmaniasis caused by Leishmania spp. As such they are being investigated to be used for adoptive transfer therapy and vaccine. In spite of the lack of antigen-specific receptors at their surface, NK cells can selectively recognize pathogens, accomplished by the activation of the receptors on the NK cell surface and also as the result of their effector functions. Activation of NK cells can occur through interaction between TLR-2 expressed on NK cells and. LPG of Leishmania parasites. In addition, NK cell activation can occur by cytokines (e.g., IFN-γ and IL-12) that also lead to producing cytokines and chemokines and lysis of target cells. This review summarizes several evidences that support NK cells activation for controlling leishmaniasis and the potentially lucrative roles of NK cells during leishmaniasis. Furthermore, we discuss strategies of Leishmania parasites in inhibiting NK cell functions. Leishmania LPG can utilizes TLR2 to evade host-immune responses. Also, Leishmania GP63 can directly binds to NK cells and modulates NK cell phenotype. Finally, this review analyzes the potentialities to harness NK cells effectiveness in therapy regimens and vaccinations.

Unwinding the mechanism of macrophage repolarization potential of Oceanimonas sp. BPMS22-derived protein protease inhibitor through Toll-like receptor 4 against experimental visceral leishmaniasis

The Oceanimonas sp. BPMS22-derived protein protease inhibitor (PPI) has been proven to shift macrophages towards an inflammatory state and reduce Leishmania donovani infection in vitro and in vivo. The current study explored and validated the mechanistic aspects of the PPI and Toll-like receptor (TLR) interaction. The PPI exhibited the upregulation of TLR2, TLR4, and TLR6 during treatment which was proven to orchestrate parasite clearance effectively. An in silico study confirmed the high interaction with TLR4 and PPI. Immune blotting confirmed the significant upregulation of TLR4 in macrophages irrespective of L. donovani infection. Pharmacological inhibition and immune blot study confirmed the involvement of the PPI in TLR4-mediated phosphorylation of p38 MAPK and dephosphorylation of ERK1/2, repolarizing to pro-inflammatory macrophage state against experimental visceral leishmaniasis. In addition, in TLR4 knockdown condition, PPI treatment failed to diminish M2 phenotypical markers (CD68, Fizz1, Ym1, CD206, and MSR-2) and anti-inflammatory cytokines (IL-4, IL-10, and TGF-β). Simultaneously, the PPI failed to upregulate the M1 phenotypical markers and pro-inflammatory cytokines (IL-1β, IL-6, IL-12, and IFN-γ) (p < 0.001) during the TLR4 knockdown condition. In the absence of TLR4, the PPI also failed to reduce the parasite load and T-cell proliferation and impaired the delayed-type hypersensitivity response. The absence of pro-inflammatory cytokines was observed during a co-culture study with PPI-treated macrophages (in the TLR4 knockdown condition) with day 10 T-cell obtained from L. donovani-infected mice. This study supports the immunotherapeutic potential of the PPI as it interacted with TLR4 and promoted macrophage repolarization (M2-M1) to restrict the L. donovani parasite burden and helps in the mounting immune response against experimental visceral leishmaniasis.

Current leishmaniasis drug discovery

Leishmaniasis is a complex protozoan infectious disease and, associated with malnutrition, poor health services and unavailability of prophylactic control measures, neglected populations are particularly affected. Current drug regimens are outdated and associated with some drawbacks, such as cytotoxicity and resistance, and the development of novel, efficacious and less toxic drug regimens is urgently required. In addition, leishmanial pathogenesis is not well established or understood, and a prophylactic vaccine is an unfulfilled goal. Human kinetoplastid protozoan infections, including leishmaniasis, have been neglected for many years, and in an attempt to overcome this situation, some new drug targets were recently identified, enabling the development of new drugs and vaccines. Compounds from new drug classes have also shown excellent antileishmanial activities, some of the most promising ones included in clinical trials, and could be a hope to control the disease burden of this endemic disease in the near future. In this review, we discuss the limitations of current control methods, explore the wide range of compounds that are being screened and identified as antileishmanial drug prototypes, summarize the advances in identifying new drug targets aiming at innovative treatments and explore the state-of-art vaccine development field, including immunomodulation strategies.

Nitric Oxide Induction in Peritoneal Macrophages by a 1,2,3-Triazole Derivative Improves Its Efficacy upon Leishmania amazonensis In Vitro Infection

1,2,3-Triazole is one of the most flexible chemical scaffolds broadly used in various fields. Here, we report the antileishmanial activity of 1,2,3-triazole derivatives, the ultrastructural alterations induced by their treatment, and the nitric oxide (NO) modulation effect on their efficacy against Leishmania amazonensis in vitro infection. After the screening of eleven compounds, compound 4 exhibited better results against L. amazonensis promastigotes (IC₅₀ = 15.52 ± 3.782 μM) and intracellular amastigotes (IC₅₀ = 4.10 ± 1.136 μM), 50% cytotoxicity concentration at 84.01 ± 3.064 μM against BALB/c peritoneal macrophages, and 20.49-fold selectivity for the parasite over the cells. Compound 4 induced ultrastructural mitochondrial alterations and lipid inclusions in L. amazonensis promastigotes, upregulated tumor necrosis factor α, interleukin (IL)-1β, IL-6, IL-12, and IL-10 messenger RNA expressions, and enhanced the NO production, verified by nitrite (p = 0.0095) and inducible nitric oxide synthase expression (p = 0.0049) quantification, which played an important role in its activity against intramacrophagic L. amazonensis. In silico prediction in association with antileishmanial activity results showed compound 4 as a hit compound with promising potential for further studies of new leishmaniasis treatment options.

Early Transcriptional Liver Signatures in Experimental Visceral Leishmaniasis

Transcriptional analysis of complex biological scenarios has been used extensively, even though sometimes the results of such analysis may prove imprecise or difficult to interpret due to an overwhelming amount of information. In this study, a large-scale real-time qPCR experiment was coupled to multivariate statistical analysis in order to describe the main immunological events underlying the early L. infantum infection in livers of BALB/c mice. High-throughput qPCR was used to evaluate the expression of 223 genes related to immunological response and metabolism 1, 3, 5, and 10 days post infection. This integrative analysis showed strikingly different gene signatures at 1 and 10 days post infection, revealing the progression of infection in the experimental model based on the upregulation of particular immunological response patterns and mediators. The gene signature 1 day post infection was not only characterized by the upregulation of mediators involved in interferon signaling and cell chemotaxis, but also the upregulation of some inhibitory markers. In contrast, at 10 days post infection, the upregulation of many inflammatory and Th1 markers characterized a more defined gene signature with the upregulation of mediators in the IL-12 signaling pathway. Our results reveal a significant connection between the expression of innate immune response and metabolic and inhibitory markers in early L. infantum infection of the liver.