Cytokine Release Assays as Tests for Exposure to Leishmania, and for Confirming Cure from Leishmaniasis, in Solid Organ Transplant Recipients

Leishmaniasis in transplant patients: what do we know so far?

PURPOSE OF REVIEW

The number of cases of visceral leishmaniasis associated with transplant-associated immunosuppression has increased in recent years. Reviewing and updating the latest developments in its diagnostic management, treatment, and follow-up is necessary and relevant.

RECENT FINDINGS

Visceral leishmaniasis cases associated with non-HIV immunosuppression are a growing cause of the parasitic infections, and the transplant patients are included in this context. These have been described especially in kidney transplantation. Liposomal amphotericin B is the first-line treatment. Due to immunosuppression, these patients often suffer from recurrent infections. The use of markers that indicate whether the patient has developed an adequate cellular response against Leishmania after treatment seems to be good biomarkers of cure and useful for monitoring and guiding secondary prophylaxis.

SUMMARY

There is a lack of consensus regarding the need for leishmaniasis screening in donors and recipients and the indications for secondary prophylaxis. The study of new biomarkers of cure may be useful in all three contexts.

Evaluation of Chemokines MIG and IP-10 as Immunological Biomarkers of Human Visceral Leishmaniasis: A Systematic Review

Visceral leishmaniasis (VL) is a neglected tropical disease that is potentially fatal when untreated. Current diagnostic methods have limitations that contribute to ongoing transmission and poor prognosis. Thus, new tests are needed to provide quick, accurate diagnoses and evaluate clinical progression and treatment efficacy. The monokine induced by interferon-gamma (MIG) and interferon-gamma-inducible protein 10 (IP-10) has been associated with the host susceptibility to VL with potential diagnostic and prognostic purposes. We performed a systematic review using four search databases (Scopus, PubMed, Web of Science, and MEDLINE) to identify studies assessing MIG and IP-10 as potential biomarkers in patients with VL across various clinical conditions. A total of 13 studies were potentially eligible and included in this review. The articles, in general, reveal that the chemokines MIG and IP-10 are elevated in response to infection by Leishmania spp., acting on the host's resistance to the development of the disease. They are associated with asymptomatic conditions and after VL treatment, and this relationship can be observed in both immunocompetent and immunocompromised individuals. Consequently, these chemokines hold relevance in the diagnoses and appropriate management of individuals with VL.

Differences in the Cellular Immune Response during and after Treatment of Sudanese Patients with Post-kala-azar Dermal Leishmaniasis, and Possible Implications for Outcome

BACKGROUND

The host cellular immune response associated with two treatments for post-kala-azar dermal leishmaniasis (PKDL) - paromomycin plus miltefosine (Arm 1), and liposomal amphotericin B plus miltefosine (Arm 2) - was examined in Sudanese patients before treatment (D0), at the end of treatment (D42), and during the post-treatment period (D180).

METHODS

Whole blood samples were stimulated with soluble Leishmania antigen for 24 h (whole blood assay [WBA]) and the concentrations of Th1/Th2/Th17-associated cytokines, IP-10, PDL-1 and granzyme B were determined.

RESULTS

The Arm 1 treatment (98.2% cure rate) induced a Th1/Th2/Th17 response, while the Arm 2 treatment (80% cure rate) induced a Th1/Th2 response. Five Arm 2 patients relapsed and showed lower IFN-γ, TNF and IL-1β concentrations at D0 than non-relapsers in this Arm. In patients with low-IFN-γ-production at D0, Arm 1 treatment led to a better host immune response and clinical outcome than Arm 2 treatment.

CONCLUSIONS

A Th1/Th2/Th17 response was associated with a higher cure rate. Patients with low IFN-γ, TNF and IL-1β before treatment are more likely to relapse if they undergo Arm 2-type treatment. Determining IFN-γ, TNF and IL-10 levels prior to treatment could help predict patients at higher risk of relapse/recovery from PKDL.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03399955, Registered 17 January 2018, https://clinicaltrials.gov/study/ NCT03399955.

Potential selection of antimony and methotrexate cross-resistance in Leishmania infantum circulating strains

BACKGROUND

Visceral leishmaniasis (VL) resolution depends on a wide range of factors, including the instauration of an effective treatment coupled to a functional host immune system. Patients with a depressed immune system, like the ones receiving methotrexate (MTX), are at higher risk of developing VL and refusing antileishmanial drugs. Moreover, the alarmingly growing levels of antimicrobial resistance, especially in endemic areas, contribute to the increasing the burden of this complex zoonotic disease.

PRINCIPAL FINDINGS

To understand the potential links between immunosuppressants and antileishmanial drugs, we have studied the interaction of antimony (Sb) and MTX in a Leishmania infantum reference strain (LiWT) and in two L. infantum clinical strains (LiFS-A and LiFS-B) naturally circulating in non-treated VL dogs in Spain. The LiFS-A strain was isolated before Sb treatment in a case that responded positively to the treatment, while the LiFS-B strain was recovered from a dog before Sb treatment, with the dog later relapsing after the treatment. Our results show that, exposure to Sb or MTX leads to an increase in the production of reactive oxygen species (ROS) in LiWT which correlates with a sensitive phenotype against both drugs in promastigotes and intracellular amastigotes. LiFS-A was sensitive against Sb but resistant against MTX, displaying high levels of protection against ROS when exposed to MTX. LiFS-B was resistant to both drugs. Evaluation of the melting proteomes of the two LiFS, in the presence and absence of Sb and MTX, showed a differential enrichment of direct and indirect targets for both drugs, including common and unique pathways.

CONCLUSION

Our results show the potential selection of Sb-MTX cross-resistant parasites in the field, pointing to the possibility to undermine antileishmanial treatment of those patients being treated with immunosuppressant drugs in Leishmania endemic areas.

Exploring the Relationship between Neutrophil Activation and Different States of Canine L. infantum Infection: Nitroblue Tetrazolium Test and IFN-γ

This study aimed to investigate the role of neutrophils in canine leishmaniosis by assessing neutrophil activation and its relationship with different states of L. infantum infection and antibody and IFN-γ production. Dogs were categorized into five groups: healthy-seronegative (n = 25), healthy-seropositive (n = 21), LeishVet-stage I (n = 25), Leishvet-stage II (n = 41), and LeishVet-stage III-IV (n = 16). Results of the nitroblue tetrazolium reduction test (NBT) showed significantly higher neutrophil activation in stage I (median:17.17, range: [7.33-31.50]%) compared to in healthy-seronegative (4.10 [1.20-18.00]%), healthy-seropositive (7.65 [3.98-21.74]%), stage II (6.50 [1.50-28.70]%), and stage III-IV (7.50 [3.00-16.75]%) groups (p < 0.0001). Healthy-seropositive dogs also displayed higher values than all groups except stage I. Stages II and III-IV did not show significant differences compared to healthy-seronegative. Regarding IFN-γ, stage I dogs had higher concentrations (median:127.90, range: [0-3998.00] pg/mL) than healthy-seronegative (0 [0-109.50] pg/mL) (p = 0.0002), stage II (9.00 [0-5086.00] pg/mL) (p = 0.045), and stage III-IV (3.50 [80.00-548.80] pg/mL) (p = 0.02) dogs. Stage II dogs showed increased IFN-γ compared to healthy-seronegative dogs (p = 0.015), while stage III-IV dogs had no significant differences compared to healthy-seronegative dogs (p = 0.12). Healthy-seropositive dogs had elevated IFN-γ concentrations compared to healthy-seronegative dogs (p = 0.001) and dogs in stage III-IV (p = 0.03). In conclusion, neutrophil activation was higher in dogs with mild disease and healthy-seropositive dogs, and a relationship between neutrophil activation and the production of IFN-γ was found.

Leishmania infantum infection after visiting southern Spain in patients on biological treatment; an observational, longitudinal, cohort study

BACKGROUND

Reports of leishmaniasis in immunosuppressed patients after visiting the Mediterranean Basin are becoming increasingly common. Still, awareness of the risk of infection and its clinical manifestations may be insufficient among healthcare professionals in the travellers' home countries.

METHODS

This observational, longitudinal study included 47 patients from Sweden with rheumatic disease and ongoing immunomodulatory treatment, who visited a rehabilitation centre in southern Spain where leishmaniasis is endemic. Patients were evaluated for clinical signs of leishmaniasis at baseline and after three years. Patients with leishmaniasis were followed for 4-5 years. The treatment outcome was assessed by clinical evaluation and determination of the cell-mediated immunological response to Leishmania by a whole blood cytokine release assay.

RESULTS

Seven patients (15%) were diagnosed with leishmaniasis. The median time from exposure to the onset of symptoms was 3 [1-17] months. The median delay between the onset of symptoms and treatment start was 9 [1-12] months. All patients with leishmaniasis responded well to treatment. Only one patient had a relapse, which occurred within the first year.

CONCLUSION

Healthcare professionals need to be aware of the increased risk of leishmaniasis for travellers who are immunosuppressed. Knowledge of the symptoms is crucial for a timely diagnosis and early treatment.

Effect of Clindamycin on Intestinal Microbiome and Miltefosine Pharmacology in Hamsters Infected with Leishmania infantum

Visceral leishmaniasis (VL), a vector-borne parasitic disease caused by Leishmania donovani and L. infantum (Kinetoplastida), affects humans and dogs, being fatal unless treated. Miltefosine (MIL) is the only oral medication for VL and is considered a first choice drug when resistance to antimonials is present. Comorbidity and comedication are common in many affected patients but the relationship between microbiome composition, drugs administered and their pharmacology is still unknown. To explore the effect of clindamycin on the intestinal microbiome and the availability and distribution of MIL in target organs, Syrian hamsters (120-140 g) were inoculated with L. infantum (108 promastigotes/animal). Infection was maintained for 16 weeks, and the animals were treated with MIL (7 days, 5 mg/kg/day), clindamycin (1 mg/kg, single dose) + MIL (7 days, 5 mg/kg/day) or kept untreated. Infection was monitored by ELISA and fecal samples (16 wpi, 18 wpi, end point) were analyzed to determine the 16S metagenomic composition (OTUs) of the microbiome. MIL levels were determined by LC-MS/MS in plasma (24 h after the last treatment; end point) and target organs (spleen, liver) (end point). MIL did not significantly affect the composition of intestinal microbiome, but clindamycin provoked a transient albeit significant modification of the relative abundance of 45% of the genera, including Ruminococcaceae UCG-014, Ruminococcus 2; Bacteroides and (Eubacterium) ruminantium group, besides its effect on less abundant phyla and families. Intestinal dysbiosis in the antibiotic-treated animals was associated with significantly lower levels of MIL in plasma, though not in target organs at the end of the experiment. No clear relationship between microbiome composition (OTUs) and pharmacological parameters was found.

Evaluation of prime and prime-boost immunization strategies in BALB/c mice inoculated with Leishmania infantum transfected with toxic plasmids

The etiologic agents of visceral leishmaniasis are Leishmania infantum and Leishmania donovani. Despite the variety of drugs available to treat leishmaniasis, most lead to serious adverse effects, and resistance to these drugs has been reported. Currently, no leishmaniasis vaccine is available for humans. That is why the group developed transgenic L. infantum promastigote lines, which express toxic proteins after differentiation into amastigotes. That is why group developed the pFL-AMA plasmid and transfected it into L. Infantum promastigotes. This plasmid was expressed only in the amastigote form of the parasite. Sequences encoding toxic proteins (active bovine trypsin and egg avidin) were inserted in this plasmid, and the transfected parasites died after the differentiation process. In this study, two immunization protocols were performed in BALB/c mice: prime and prime-boost immunization prior to challenge with the wild-type L. infantum (WT). The parasite burdens in the spleen, liver, and bone marrow were evaluated to verify immunological protection. Histopathological analysis of the spleen and liver and the humoral immune response were also performed. The data showed that the parasite burden was reduced in prime-boosted mice in the spleen, liver, and bone marrow, indicating that mice immunized with two doses of the transfected parasites were satisfactorily protected. High levels of IgG, IgG1, and IgG2a antibodies were observed, as well as the presence of anti-inflammatory cytokine Interleukine-10 and pro-inflammatory cytokine Tumor Necrosis Factor-α (TNF-α) and Interferon-γ (IFN - γ) suggesting a Th1/Th2 mix response, in addition to the presence of multinucleated giant cells in the spleen and lymphocyte infiltration in the liver. Therefore, L. infantum transfected with a toxic plasmid is an excellent vaccine candidate against visceral leishmaniasis and the application of a boost before the challenge promotes greater protection against WT L. infantum infection.

Comparison of serum cytokine levels in symptomatic and asymptomatic HIV-Leishmania coinfected individuals from a Brazilian visceral leishmaniasis endemic area

Background

Visceral leishmaniasis (VL) remains an important infectious disease worldwide. VL-HIV coinfected individuals can present with atypical clinical forms of VL and have a high risk of VL relapse. Some cytokines have been described as potential markers to diagnose active VL and to predict the severity of the cases. However, few studies have included VL-HIV coinfected patients. We aimed to characterize the levels of several cytokines among VL-HIV coinfected individuals living in a VL-endemic area in Northeast Brazil.

Methods

This was a retrospective, cross-sectional study, aiming to estimate the levels of various cytokines in symptomatic and asymptomatic VL-HIV coinfected individuals. There were 134 study participants (35 symptomatic VL-HIV, 75 asymptomatic VL-HIV, and 24 healthy controls), all ≥ 18 years-old. Serum cytokine levels (interferon-γ, tumor necrosis factor, and interleukins 2, 4, 6, 10, and 17A) were quantified using the Becton Dickinson-BD’s Cytometric Bead Array (CBA) system.

Results

The population mainly consisted of men (64.9%), with a median age of 35 (27–41) years. Asymptomatic individuals were younger (p = 0.013), with more years of education (p < 0.001), and were more often on antiretroviral therapy (p < 0.001) than those in the symptomatic group. Hemoglobin levels (p < 0.001), lymphocytes (p < 0.001) and CD4 count (p < 0.001) were lower in symptomatic individuals, while HIV viral loads were higher (p < 0.001). In the symptomatic VL-HIV coinfected group, we observed increased serum levels of IL-17A, IL-6, and IL-10 compared to asymptomatic patients and the healthy controls. There were no differences in the levels of all cytokines between asymptomatic VL-HIV coinfected individuals and the healthy controls.

Conclusions

Higher serum levels of IL-17A, IL-6, and IL-10 cytokines were observed in symptomatic coinfected individuals but not in asymptomatically infected individuals. More studies among HIV-positive persons are needed to better understand the role of serum cytokines for prognosis, to define cure and predict VL relapses in VL-HIV coinfected individuals.

Visceral leishmaniasis (VL) is a parasitic disease, classified as a neglected disease by the World Health Organization. It is present in more than 60 countries in four continents, with most tropical and subtropical countries affected. Without treatment, the disease is fatal. HIV-positive persons are especially affected by VL, with a worst prognosis. One of the main complications is the frequent reactivation of the disease even after successful treatment (VL relapse). Up to now, it is not clear why and when these reactivations occur, and many researches are trying to find some biological markers to answer this. Cytokines are one of these markers that may explain the progression of the disease. In this study, we compared the level of several key cytokines in symptomatic VL-HIV coinfected patients, asymptomatic VL-HIV coinfected individuals, and healthy controls living in a VL-endemic region in Northeastern Brazil. The serum cytokine levels were higher in symptomatic patients when compared with asymptomatic and healthy controls. More studies following VL-HIV patients are necessary to understand how these cytokines and the other biomarkers vary over time and whether they can predict VL relapse, and also the progression and the prognosis of the disease.

An exploratory analysis of C-X-C motif chemokine ligand 10 as a new biomarker of asymptomatic Leishmania infantum infection in Solid-Organ Transplant Recipients

OBJECTIVE

Sensitive and less laborious assays are needed to detect asymptomatic Leishmania among solid organ transplant (SOT) recipients. Using SLA-stimulated plasma from SOT recipients living where an outbreak of Leishmania infantum occurred, we examined potential biomarkers to identify asymptomatic Leishmania infections.

METHODS

Concentrations of cytokines/chemokines in plasma from whole blood stimulated with specific Leishmania antigen (SLA) were compared against infection status as determined by a currently used cell proliferation assay.

RESULTS

Twenty-six percent (13/50) of the SOT recipients had a cell proliferation assay (CPA) indicating asymptomatic infection, and showed higher processed plasma C-X-C motif chemokine ligand 10 (CXCL10 or IP-10) concentrations than did non-infected subjects (median 2272.0 pg/ml [IQR-1570-2772] vs. 18.2 pg/ml [IQR 1-150.1]; p<0.0001). CXCL10 showed a sensitivity of 93% and a specificity of 95% compared to CPA. In addition, we demonstrated that the number of asymptomatic infections detected using CXCL10, decreased with distance from a park at the centre of the mentioned outbreak.

CONCLUSION

CXCL10 in plasma from SLA-stimulated blood could be a robust biomarker of asymptomatic L. infantum infection in solid organ transplant recipients.

Immunomodulatory role of Th17 pathway in experimental visceral leishmaniasis

Visceral leishmaniasis (VL) or Kala-azar is a vector borne protozoan infection caused by Leishmania donovani in the Indian subcontinent mainly India, Nepal and Bangladesh. It is a major public health problem in these countries mostly affecting the socio-economically poor population. Leishmaniasis ranks the third most important disease after malaria and filariasis but is still considered as one of the neglected tropical diseases of the world. For development of better therapeutic agents and effective vaccine against VL, there is a need to understand host immunological changes that play a vital role during course of infection. Therefore, we investigated the role of Th17 pathway in Balb/c mice during Leishmania donovani infection and treatment with amphotericin B. Mice were divided in four groups i.e. Control, Infected, Uninfected treated and Infected treated. The cytokine levels were estimated in the spleen of Balb/c mice on days 1, 3, 7, 14, 17, 21, 28, 35, 45 and 60 post infection and during course of treatment. The mRNA levels of the Th17 pathway during active Leishmania donovani infection and after treatment were determined by real time polymerase chain reaction (RT-PCR) and protein levels by flow cytometry and ELISA. Results of our study revealed that active infection was associated with low levels of Th17 cytokines IL-17, IL-22 and IL-23 and elevated levels of IL-6, IL-1β and TGF-β. Amphotericin B treatment restored production of pro-inflammatory cytokines IL-17 and IL-22. The levels of transcription factor RORγt were found to correlate with the levels of IL-17 during infection and also after chemotherapy whereas STAT3 levels were elevated during infection and vice versa after treatment. The findings of this study suggest that Th17 cytokines IL-17 and IL-22 are associated with protection against VL infection and development of any interventions or chemotherapeutic agents targeting Th17 pathway could be an important approach for VL treatment.

Leishmaniasis: A new method for confirming cure and detecting asymptomatic infection in patients receiving immunosuppressive treatment for autoimmune disease

Visceral leishmaniasis (VL) in patients receiving immunosuppressant drugs for autoimmune disease has been on the rise. It is important—but difficult—to know when cure has been achieved in these patients since the withdrawal of immunosuppressants during antileishmania treatment is commonly required, and there is a risk of relapse when immunosuppression is restored. The prevalence of asymptomatic infection among those immunosuppressed for autoimmune disease is also uncertain. The present work describes how cytokine release assays can be used to confirm the cure of VL, and to determine the prevalence of asymptomatic infection, in such patients. After collection of blood from volunteers (n = 108), SLA-stimulation of peripheral blood mononuclear cell cultures and of whole blood was found to induce the production of different combinations of cytokines that served to confirm recovery from VL, and asymptomatic Leishmania infection. Indeed, cure was confirmed in 14 patients, all of whom showed a specific Th1 immune response against Leishmania, and the prevalence of asymptomatic infection was determined as 21.27%. Cytokine profiles could be used to manage VL in patients with autoimmune disease, and to identify and better protect those with asymptomatic infection who are at risk of developing this disease.

Cytokine release assays were used to confirm the cure of visceral leishmaniasis in patients (from an area where Leishmania infantum is endemic) with autoimmune disease. They were also used to determine the prevalence of asymptomatic Leishmania infantum infection in similar patients. Some 21.27% of those with no clinical history of leishmaniasis were shown to have been contact with the parasite.

Tropical Infections in the Context of Kidney Transplantation in Latin America

Reports on tropical infections among kidney transplant (KT) recipients have increased in recent years, mainly because of the growing number of KT programs located in tropical and subtropical areas, and greater mobility or migration between different areas of the world. Endemic in emerging and developing regions, like most countries in Latin America, tropical infections are an important cause of morbidity and mortality in this population. Tropical infections in KT recipients may exhibit different pathways for acquisition compared with those in nonrecipients, such as transmission through a graft and reactivation of a latent infection triggered by immunosuppression. Clinical presentation may differ compared with that in immunocompetent patients, and there are also particularities in diagnostic aspects, treatment, and prognosis. KT patients must be screened for latent infections and immunized properly. Last, drug-drug interactions between immunosuppressive agents and drugs used to treat tropical infections are an additional challenge in KT patients. In this review, we summarize the management of tropical infections in KT patients.

Effect of immunosuppressants on the parasite load developed in, and immune response to, visceral leishmaniasis: A comparative study in a mouse model

The increasing use of immunosuppressants in areas where visceral leishmaniasis (VL) is endemic has increased the number of people susceptible to developing more severe forms of the disease. Few studies have examined the quality of the immune response in immunosuppressed patients or experimental animals with VL. The present work characterises the parasite load developed in, and immune response to, Leishmania infantum-induced VL in C57BL/6 mice that, prior to and during infection, received immunosuppressant treatment with methylprednisolone (MPDN), anti-tumour necrosis factor (anti-TNF) antibodies, or methotrexate (MTX). The latter two treatments induced a significant reduction in the number of CD4+ T lymphocytes over the infection period. The anti-TNF treatment was also associated with a higher parasite load in the liver and a lower parasite load in the spleen. This, plus a possibly treatment-induced reduction in the number of cytokine-producing Th1 cells in the spleen, indicates the development of more severe VL. Interestingly, the MPDN and (especially) MTX treatments provoked a greater presence of soluble Leishmania antigen-specific multi-cytokine-producing T cells in the spleen and a lower liver parasite load than in control animals. These results highlight the need to better understand how immunosuppressant treatments might influence the severity of VL in human patients.

Case Report: Cutaneous Leishmaniasis Misdiagnosed as Pyoderma Gangrenosum

With an estimated prevalence of 0.7%, pyoderma gangrenosum (PG) is the most frequent type of reactive skin lesions seen in the setting of inflammatory bowel disease, together with metastatic Crohn's disease. However, in the case of persistent cutaneous ulcerations in patients with Crohn's disease under biologic and/or immunosuppressive therapy, infectious or malignant etiologies should be excluded. We report a case of multiple difficult-to-treat skin ulcerations due to Leishmania in a patient with Crohn's disease treated with antitumor necrosis factor-alpha drugs, misinterpreted for a long time as PG.

Prevalence of asymptomatic Leishmania infection and associated risk factors, after an outbreak in the south-western Madrid region, Spain, 2015

BackgroundA large outbreak of leishmaniasis with 758 cutaneous and visceral leishmaniasis cases occurred in 2009 in Fuenlabrada, in the south-west of the Madrid region of Spain.AimWe aimed to determine the prevalence of asymptomatic Leishmania infection after this outbreak, and its associated risk factors.MethodsA cross-sectional study of 804 healthy individuals living in Fuenlabrada who had no history of leishmaniasis, was conducted between January and July 2015. Asymptomatic infections were sought by either a combination of PCR, immunofluorescent antibody titre, and direct agglutination tests, or by whole blood stimulation assay (WBA) with interleukin-2 (IL-2) quantification.ResultsUsing the first approach, prevalence of asymptomatic individuals was 1.1% (9/804), while the second returned a value of 20.7% (143/804). Older age, being male, proximity to the park where the focus of infection was identified, and living in a detached house, were all strongly associated with the prevalence of asymptomatic infection.ConclusionsThe true number of infected individuals may be underestimated if only serological methods are used. The combination of WBA with IL-2 quantification may allow to better determine the prevalence of asymptomatic Leishmania infection, which would be useful in establishing control measures and in quantifying their impact. In our study, the use of WBA with IL-2 quantification also helped establish the risk factors that influence exposure to and infection by Leishmania.

Implications of asymptomatic infection for the natural history of selected parasitic tropical diseases

Progress has been made in the control or elimination of tropical diseases, with a significant reduction of incidence. However, there is a risk of re-emergence if the factors fueling transmission are not dealt with. Although it is essential to understand these underlying factors for each disease, asymptomatic carriers are a common element that may promote resurgence; their impact in terms of proportion in the population and role in transmission needs to be determined. In this paper, we review the current evidence on whether or not to treat asymptomatic carriers given the relevance of their role in the transmission of a specific disease, the efficacy and toxicity of existing drugs, the Public Health interest, and the benefit at an individual level, for example, in Chagas disease, to prevent irreversible organ damage. In the absence of other control tools such as vaccines, there is a need for safer drugs with good risk/benefit profiles in order to change the paradigm so that it addresses the complete infectious process beyond manifest disease to include treatment of non-symptomatic infected persons.

Whole Blood Stimulation Assay as a Treatment Outcome Monitoring Tool for VL Patients in Ethiopia: A Pilot Evaluation

Visceral leishmaniasis (VL) is a lethal disease if left untreated. Current treatments produce variable rates of treatment failure and toxicity without sterile cure, rendering treatment efficacy monitoring essential. To avoid repeated invasive tissue aspirates as well as empirical treatment, there is a need for new tools that allow a less-invasive and early assessment of treatment efficacy in the field. Cross-sectional studies have suggested levels of cytokines/chemokines after whole blood stimulation as good markers of cure, but longitudinal studies are lacking. In this study, we followed 13 active VL cases in an endemic area in Ethiopia by measuring the production of IFN-γ, TNF-α, IP-10, IL-2, IL-10, MCP-1, and MIG before, during, and at the end of treatment. After 24 hours of stimulation of whole blood with soluble Leishmania antigen, we observed an early, robust, and incremental increase of IFN-γ, TNF-α, and IP-10 levels in all patients during treatment. Moreover, based on the IFN-γ levels that showed an average 13-fold increase from the time of diagnosis until the end of treatment, we could almost perfectly discriminate active from cured status. Similar concentrations and patterns were found in stimulation assays with the two main Leishmania species. The levels of IFN-γ, IP-10, or TNF-α also seemed to be inversely associated with the parasite load at baseline. Despite a 1/10 drop in concentrations, similar patterns were observed in IFN-γ and IP-10 levels when dried plasma spots were stored at 4°C for an average of 225 days. All the above evidence suggests a detectable restoration of cell-mediated immunity in VL and its association with parasite clearance. With a potential application in rural settings by means of dried plasma spots, we recommend to further explore the early diagnostic value of such assays for treatment efficacy monitoring in large cohort studies including treatment failure cases.

Leishmania infantum asymptomatic infection in inflammatory bowel disease patients under anti-TNF therapy

BACKGROUND

In recent years anti-TNF therapy has been associated with leishmaniasis in immunocompromised patients from endemic areas. Nevertheless, data on asymptomatic Leishmania infection in such patients is scarce. The aim of this study was to determine the prevalence of asymptomatic infection in inflammatory bowel disease (IBD) patients treated with TNF inhibitors living in an endemic area (Catalonia) and to follow up them to study how the infection evolved.

METHODS

192 IBD patients (143 Crohn's disease; 49 ulcerative colitis) from Catalonia (Spain), an area endemic for L. infantum, were recruited. Peripheral blood samples were collected and tested for anti-Leishmania antibodies by Western blotting (WB). Leishmania kinetoplast DNA was detected in peripheral blood mononuclear cells (PBMC) by a quantitative PCR.

RESULTS

Serology was positive in 3.1% and Leishmania DNA was found in 8.8%, with a low parasitic load and humoral response. The prevalence was 10.9%, patients being considered infected if they tested positive by at least one of the techniques. Eight out of the 21 patients with asymptomatic leishmaniasis were monitored for 3-8 months after the first test. None of them showed an increased parasitemia or humoral response, or developed leishmaniasis during the follow-up period.

CONCLUSION

The prevalence of Leishmania asymptomatic infection detected in our IBD cohort is similar to that found in healthy population in close endemic areas. Due to the short monitoring period, it is not possible to reach a conclusion about the risk of Leishmania reactivation from this study.

Screening strategies for the diagnosis of asymptomatic Leishmania infection in dialysis patients as a model for kidney transplant candidates

Despite being considered a tropical disease, visceral leishmaniasis (VL) caused by L. infantum is also endemic in the Mediterranean Europe and represents an increasing cause of morbidity and mortality in solid organ transplant (SOT) recipients. VL occurring in kidney transplant recipients is a severe event, often worsening the renal damage and leading to poor outcome. It is believed that most of VL cases in transplant recipients are caused by reactivation of a pre-existent, dormant leishmanial infection induced by the immunosuppressive drugs. Nevertheless, the prevalence of asymptomatic Leishmania infection in candidates to kidney transplant residing in or visiting endemic areas is unknown. As L. infantum is highly circulating in northeastern Italy, we aimed to examine the occurrence of this parasitic infection in 119 dialysis patients living in the mentioned area, 71 of whom were potential candidates to kidney transplant. By employing a combination of sensitive serological and molecular methods, we observed a prevalence of 15.9% asymptomatic Leishmania infection in the study cohort. This finding emphasizes the need of further evaluating potential screening strategies for Leishmania infection in solid organ transplant candidates residing in or visiting endemic areas.

New Strategies and Biomarkers for the Control of Visceral Leishmaniasis

Effective diagnosis and treatment of visceral leishmaniasis, together with the study of vectors and reservoirs, can lead to a better understanding of the parasite transmission dynamics and the development of more efficient control measures. Recent studies have applied new methodologies and biomarkers, and these have contributed to the early and rapid diagnosis of the disease; assessment of success of pharmacological treatments; efficient monitoring of immunosuppressed individuals; and to population screening for field trials of vaccine efficacy. This opinion article proposes an update to the diagnostic tools for visceral leishmaniasis and their rational and combined use to establish the real prevalence of infection or of exposure to Leishmania in endemic areas.

Assessment of Vaccine-Induced Immunity Against Canine Visceral Leishmaniasis

Canine visceral leishmaniasis is an increasingly important public health problem. Dogs infected by Leishmania infantum are the main domestic reservoir of the parasite and play a key role in its transmission to humans. Recent findings have helped in the development of novel diagnostic methods, and of control measures such as vaccines, some of which are already commercially available. However, quantitative procedures should be followed to confirm whether these vaccines elicit a cell-mediated immune response. The present work describes the need for this evaluation, and the techniques available for confirming this type of immune response.

Asymptomatic immune responders to Leishmania among HIV positive patients

Concomitant infection with human immunodeficiency virus (HIV) and the Leishmania parasite is a growing public health problem, the result of the former spreading to areas where the latter is endemic. Leishmania infection is usually asymptomatic in immunocompetent individuals, but the proportion of HIV+ individuals in contact with the parasite who remain asymptomatic is not known. The aim of the present work was to examine the use of cytokine release assays in the detection of asymptomatic immune responders to Leishmania among HIV+ patients with no previous leishmaniasis or current symptomatology. Eighty two HIV+ patients (all from Fuenlabrada, Madrid, Spain, where a leishmaniasis outbreak occurred in 2009) were examined for Leishmania infantum infection using molecular and humoral response-based methods. None returned a positive molecular or serological result for the parasite. Thirteen subjects showed a positive lymphoproliferative response to soluble Leishmania antigen (SLA), although the mean CD4+ T lymphocyte counts of these patients was below the normal range. Stimulation of peripheral blood mononuclear cells (PBMC) or whole blood with SLA (the lymphoproliferative assay and whole blood assay respectively), led to the production of specific cytokines and chemokines. Thus, despite being immunocompromised, HIV+ patients can maintain a Th1-type cellular response to Leishmania. In addition, cytokine release assays would appear to be useful tools for detecting these individuals via the identification of IFN-γ in the supernatants of SLA-stimulated PBMC, and of IFN-γ, MIG and IL-2 in SLA-stimulated whole blood. These biomarkers appear to be 100% reliable for detecting asymptomatic immune responders to Leishmania among HIV+ patients.

The proportion of patients with HIV+ who have at some time been infected with the Leishmania parasite, but who remain asymptomatic, is unknown. It is important to be able to identify such patients to determine the prevalence of asymptomatic leishmaniasis in the HIV+ population, and because these persons are at increased risk of developing symptomatic visceral leishmaniasis. In the present work, a population of HIV+ patients showing a cellular immune response to Leishmania infantum was identified. These subjects all showed a clear Th1-type response when their PBMC or blood were stimulated in vitro with soluble Leishmania antigen (SLA). Cytokine release assays and the detection of IFN-γ, MIG and IL-2 (specific biomarkers for immunity to Leishmania) were found to be useful for detecting this population of HIV+ patients. New studies with larger numbers of patients are needed to confirm the present results.

[Pancytopenia of unknown origin in a 52-year-old patient]

A 52-year-old patient developed pancytopenia of unknown origin 1.5 years after allogeneic stem cell transplantation. The bone marrow aspirate showed visceral leishmaniasis (VL). Although VL is distributed world-wide, the incidence in patients after allogeneic stem cell transplantation is rare.

Cellular Markers of Active Disease and Cure in Different Forms of Leishmania infantum-Induced Disease

Increased numbers of peripheral blood mononucleocytes (PBMC) and increased IFN-γ secretion following in vitro challenge of blood samples with soluble Leishmania antigen (SLA), have been proposed as biomarkers of specific cell-mediated immunity, indicating that treatment of visceral leishmaniasis (VL) has been successful. However, Leishmania infantum infection may manifest as cutaneous leishmaniasis (CL), and less commonly as localized leishmanial lymphadenopathy (LLL) or mucosal leishmaniasis (ML). The present work examines the value of these biomarkers as indicators of cured leishmaniasis presenting in these different forms. Blood samples were collected before and after treatment from patients living in Fuenlabrada (Madrid, Spain), an L. infantum-endemic area recently the center of a leishmaniasis outbreak. All samples were subjected to Leishmania-specific PCR, serological tests (IFAT and rK39-ICT), and the SLA-cell proliferation assay (SLA-CPA), recording PBMC proliferation and the associated changes in IFN-γ production. Differences in the results recorded for the active and cured conditions were only significant for VL. PCR returned positive results in 67% of patients with active VL and in 3% of those with cured leishmaniasis. Similarly, rK39-ICT returned a positive result in 77% of active VL samples vs. 52% in cured VL samples, and IFAT in 90% vs. 56%; in the SLA-CPA, PBMC proliferation was seen in 16% vs. 90%, and an associated increase in IFN-γ production of 14 and 84%, respectively. The present findings reinforce the idea that PBMC proliferation and increased IFN-γ production in SLA-stimulated PBMC provide biomarkers of clinical cure in VL. Other tests are urgently needed to distinguish between the cured and active forms of the other types of clinical leishmaniasis caused by L. infantum.

Recent Development of Visceral Leishmaniasis Treatments: Successes, Pitfalls, and Perspectives

Research in visceral leishmaniasis in the last decade has been focused on how better to use the existing medicines as monotherapy or in combination. Systematic research by geographical regions has shown that a universal treatment is far from today's reality. Substantial progress has been made in the elimination of kala-azar in South Asia, with a clear strategy on first- and second-line therapy options of single-dose liposomal amphotericin B and a combination of paromomycin and miltefosine, respectively, among other interventions. In Eastern Africa, sodium stibogluconate (SSG) and paromomycin in combination offer an advantage compared to the previous SSG monotherapy, although not exempted of limitations, as this therapy requires 17 days of painful double injections and bears the risk of SSG-related cardiotoxicity. In this region, attempts to improve the combination therapy have been unsuccessful. However, pharmacokinetic studies have led to a better understanding of underlying mechanisms, like the underexposure of children to miltefosine treatment, and an improved regimen using an allometric dosage. Given this global scenario of progress and pitfalls, we here review what steps need to be taken with existing medicines and highlight the urgent need for oral drugs. Furthermore, it should be noted that six candidates belonging to five new chemical classes are reaching phase I, ensuring an optimistic near future.

Growth arrested live-attenuated Leishmania infantum KHARON1 null mutants display cytokinesis defect and protective immunity in mice

There is no safe and efficacious vaccine against human leishmaniasis available and live attenuated vaccines have been used as a prophylactic alternative against the disease. In order to obtain an attenuated Leishmania parasite for vaccine purposes, we generated L. infantum KHARON1 (KH1) null mutants (ΔLikh1). This gene was previously associated with growth defects in L. mexicana. ΔLikh1 was obtained and confirmed by PCR, qPCR and Southern blot. We also generate a KH1 complemented line with the introduction of episomal copies of KH1. Although ΔLikh1 promastigote forms exhibited a growth pattern similar to the wild-type line, they differ in morphology without affecting parasite viability. L. infantum KH1-deficient amastigotes were unable to sustain experimental infection in macrophages, forming multinucleate cells which was confirmed by in vivo attenuation phenotype. The cell cycle analysis of ΔLikh1 amastigotes showed arrested cells at G₂/M phase. ΔLikh1-immunized mice presented reduced parasite burden upon challenging with virulent L. infantum, when compared to naïve mice. An effect associated with increased Li SLA-specific IgG serum levels and IL-17 production. Thus, ΔLikh1 parasites present an infective-attenuated phenotype due to a cytokinesis defect, whereas it induces immunity against visceral leishmaniasis in mouse model, being a candidate for antileishmanial vaccine purposes.

New insights into leishmaniasis in the immunosuppressed

Immunosuppression contributes significantly to the caseload of visceral leishmaniasis (VL). HIV coinfection, solid organ transplantation, malnutrition, and helminth infections are the most important immunosuppression-related factors. This review briefly describes the challenges of these associations. East Africa and the Indian subcontinent are the places where HIV imposes the highest burden in VL. In the highlands of Northern Ethiopia, migrant rural workers are at a greater risk of coinfection and malnutrition, while in India, HIV reduces the sustainability of a successful elimination programme. As shown from a longitudinal cohort in Madrid, VL is an additional threat to solid organ transplantation. The association with malnutrition is more complex since it can be both a cause and a consequence of VL. Different regimes for therapy and secondary prevention are discussed as well as the role of nutrients on the prophylaxis of VL in poverty-stricken endemic areas.

Current approaches to visceral leishmaniasis treatment in solid organ transplant recipients

INTRODUCTION

The increasing number of transplants performed worldwide and the growing global mobility with migration and travel to and from developing countries and tropical areas are bringing new challenges for the management of transplant infectious diseases, previously less commonly seen, such as Leishmaniasis. However, in this scenario there is a lack of information and the current knowledge is based on a few studies. The selection of the most appropriate treatment depends on various factors, such as patient profile, Leishmania species, disease extent, drug availability, concomitant infections and previous treatments. Therapeutic options may include different formulations of amphotericin B, pentavalent antimonials, miltefosine and paromomycin, among others. These drugs can be used alone or in combination. Areas covered: This review is a practical guide for Visceral Leishmaniasis (VL) specific treatment in solid organ transplant recipients (SOT), including therapeutic options and assessment of therapy response. Expert commentary: The main challenges for treatment of leishmaniasis in SOT recipients are related to the duration of therapy, curative criteria and secondary prophylaxis. Immunosuppression dose reduction is often recommended, but such decisions must be made on an individual basis. At present, Liposomal Amphotericin B is the best choice for treatment and prophylaxis.

Antigenicity of Leishmania-Activated C-Kinase Antigen (LACK) in Human Peripheral Blood Mononuclear Cells, and Protective Effect of Prime-Boost Vaccination With pCI-neo-LACK Plus Attenuated LACK-Expressing Vaccinia Viruses in Hamsters

Leishmania-activated C-kinase antigen (LACK) is a highly conserved protein among Leishmania species and is considered a viable vaccine candidate for human leishmaniasis. In animal models, prime-boost vaccination with LACK-expressing plasmids plus attenuated vaccinia viruses (modified vaccinia Ankara [MVA] and mutant M65) expressing LACK, has been shown to protect against cutaneous leishmaniasis (CL). Further, LACK demonstrated to induce the production of protective cytokines in patients with active CL or cured visceral leishmaniasis, as well as in asymptomatic individuals from endemic areas. However, whether LACK is capable to trigger cytokine release by peripheral blood mononuclear cells from patients cured of CL due to Leishmania infantum (L. infantum) or induce protection in L. infantum-infected hamsters [visceral leishmaniasis (VL) model], has not yet been analyzed. The present work examines the ex vivo immunogenicity of LACK in cured VL and CL patients, and asymptomatic subjects from an L. infantum area. It also evaluates the vaccine potential of LACK against L. infantum infection in hamsters, in a protocol of priming with plasmid pCI-neo-LACK (DNA-LACK) followed by a booster with the poxvirus vectors MVA-LACK or M65-LACK. LACK-stimulated PBMC from both asymptomatic and cured subjects responded by producing IFN-γ, TNF-α, and granzyme B (Th1-type response). Further, 78% of PBMC samples that responded to soluble Leishmania antigen showed IFN-γ secretion following stimulation with LACK. In hamsters, the protocol of DNA-LACK prime/MVA-LACK or M65-LACK virus boost vaccination significantly reduced the amount of Leishmania DNA in the liver and bone marrow, with no differences recorded between the use of MVA or M65 virus vector options. In summary, the Th1-type and cytotoxic responses elicited by LACK in PBMC from human subjects infected with L. infantum, and the parasite protective effect of prime/boost vaccination in hamsters with DNA-LACK/MVA-LACK and DNA-LACK/M65-LACK, revealed the significance of LACK in activating human and hamster immune responses and support LACK to be a valuable candidate for inclusion in a vaccine against human VL.

Nutritional supplements for patients being treated for active visceral leishmaniasis

BACKGROUND

Visceral leishmaniasis (VL) is a disease caused by a parasite, which can lead to death if untreated. Poor nutritional status hastens the progression of VL infection, and VL worsens malnutrition status. Malnutrition is one of the poor prognostic factors identified for leishmaniasis. However, the effects of nutritional supplementation in people treated for VL are not known.

OBJECTIVES

To assess the effects of oral nutritional supplements in people being treated with anti-leishmanial drug therapy for VL.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group (CIDG) Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, and two trial registers up to 12 September 2017. We checked conference proceedings and WHO consultative meeting reports, the reference lists of key documents and existing reviews, and contacted experts and nutritional supplement companies.

SELECTION CRITERIA

Randomized controlled trials (RCTs), quasi-randomized controlled trials (quasi-RCTs), and non-randomized controlled trials (NRCTs) of any oral nutritional supplement, compared to no nutritional intervention, placebo, or dietary advice alone, in people being treated for VL.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the literature search results for studies that met the inclusion criteria. We had planned for two review authors to independently extract data and assess the risk of bias of the included studies. We planned to follow the Cochrane standard methodological procedures for assessing risk of bias and analysing the data.

MAIN RESULTS

We identified no eligible studies for this review, either completed or ongoing.

AUTHORS' CONCLUSIONS

We found no studies, either completed or ongoing, that assessed the effects of oral nutritional supplements in people with VL who were being treated with anti-leishmanial drug therapy. Thus, we could not draw any conclusions on the impact of these interventions on primary cure of VL, definitive cure of VL, treatment completion, self-reported recovery from illness or resolution of symptoms, weight gain, increased skinfold thickness, other measures of lean or total mass, or growth in children.This absence of evidence should not be interpreted as evidence of no effect for nutritional supplements in people under VL treatment. It means that we did not identify research that fulfilled our review inclusion criteria.The effects of oral nutritional supplements in people with VL who are being treated with anti-leishmanial drug therapy have yet to be determined by rigorous experimental studies, such as cluster-randomized trials, that focus on outcomes relevant for patients.

Cytokines and chemokines measured in dried SLA-stimulated whole blood spots for asymptomatic Leishmania infantum and Leishmania donovani infection

Whole blood stimulation with soluble Leishmania antigen (SLA), followed by plasma cytokine and chemokine determination, provides means of detecting subjects with asymptomatic Leishmania infection. This work examines the potential of Protein Saver 903 cards for the storage and transport of SLA-stimulated dried plasma spot samples. Blood was collected from asymptomatic and negative control subjects living in a Leishmania infantum- (Spain) and Leishmania donovani-endemic area (Bangladesh). After SLA-stimulation, three types of sample were prepared: frozen liquid plasma (-20 °C), and plasma dropped onto Protein Saver cards kept at -20 °C (DPS-FZ), and at ambient temperature (DPS-AT). The concentrations of IFN-γ, IL-2, CXCL10, CXCL9, CCL2 and CXCL8 in the thawed liquid plasma (TLP), DPS-FZ and DPS-AT samples were then determined. Strong correlations were seen between the TLP and DPS-FZ/AT samples for all the studied cytokines/chemokines in both the L. infantum and L. donovani areas. Protein Saver 903 cards would therefore appear to allow for the transport of SLA-stimulated plasma samples by courier at ambient temperature. The CXCL10 and CXCL9 detectable in these plasma spots provided robust markers for identifying asymptomatic subjects from both endemic areas. This easy procedure opens up new possibilities for field studies in resource-limited settings, which could help in Leishmania control.

Leishmania infantum-specific IFN-γ production in stimulated blood from dogs with clinical leishmaniosis at diagnosis and during treatment

There is limited data regarding Leishmania infantum specific T cell mediated immunity in naturally infected sick dogs at the time of diagnosis and during anti-Leishmania treatment. Our aim was to investigate the kinetics of L. infantum specific IFN-γ production in dogs with leishmaniosis at the time of diagnosis and during treatment and to correlate it with specific L. infantum antibodies, blood parasitemia and clinicopathological findings. Thirty-four dogs were diagnosed with leishmaniosis based on physical examination, routine laboratory tests and L. infantum-specific antibody levels by quantitative ELISA. Heparinized whole blood was stimulated with L. infantum soluble antigen (LSA) and concanavalin A (ConA) and incubated for 5days. IFN-γ concentration was evaluated in supernatants of stimulated blood using a commercial sandwich ELISA. Leishmania real-time PCR was also performed for assessing blood parasitemia. Dogs were treated with meglumine antimoniate and allopurinol. Sixteen dogs were classified as IFN-γ non-producers after LSA stimulation (mean±SD: 0±0pg/mL) and 18 dogs as IFN-γ producers (mean±SD: 2885.3±4436.1pg/mL) at the time of diagnosis (P<0.0001). IFN-γ non-producers were classified in a more severe clinical staging than IFN-γ producers that presented a mild to moderate clinical staging (P=0.03). In the IFN-γ non-producer group, production of IFN-γ after LSA stimulation was significantly increased during treatment especially at day 365 (P=0.018) together with clinical improvement when compared with day 0. In contrast, IFN-γ producers maintained their IFN-γ production after LSA stimulation and no statistically significant changes were found during treatment follow-up. At diagnosis, IFN-γ non-producers showed a significantly higher blood parasitemia versus IFN-γ -producers (P=0.005). IFN-γ non-producers drastically reduced blood parasitemia to minimum values at day 365 when compared with day 0 (P=0.017). No significant differences were found at day 365 in blood parasitemia of IFN-γ producers compared to pre-treatment. At diagnosis, L. infantum specific antibodies were higher in IFN-γ non-producers than IFN-γ producers (P=0.014). A marked reduction of antibody levels was found at day 365 when compared with day 0 in IFN-γ non-producers (P=0.005) and producers (P=0.001). These results demonstrate that IFN-γ concentration increases with long-term anti-Leishmania treatment together with clinical improvement in dogs that do not produce IFN-γ at diagnosis. Together with clinical recovery, reduction in blood parasitemia and L. infantum specific antibodies, tracking IFN-γ concentration could constitute an important prognostic tool for immune monitoring in CanL.

Monocyte Chemotactic Protein 1 in Plasma from Soluble Leishmania Antigen-Stimulated Whole Blood as a Potential Biomarker of the Cellular Immune Response to Leishmania infantum

New biomarkers are needed to identify asymptomatic Leishmania infection as well as immunity following vaccination or treatment. With the aim of finding a robust biomarker to assess an effective cellular immune response, monocyte chemotactic protein 1 (MCP-1) was examined in plasma from soluble Leishmania antigen (SLA)-stimulated whole blood collected from subjects living in a Leishmania infantum-endemic area. MCP-1, expressed 110 times more strongly than IL-2, identified 87.5% of asymptomatic subjects and verified some asymptomatic subjects close to the cutoff. MCP-1 was also significantly elevated in all patients cured of visceral leishmaniasis (VL), unlike IL-2, indicating the specific memory response generated against Leishmania. These results show MCP-1 to be a robust candidate biomarker of immunity that could be used as a marker of cure and to both select and follow the population in vaccine phase I–III human clinical trials with developed rapid, easy-to-use field tools.

F1 Domain of the Leishmania (Leishmania) donovani Nucleoside Hydrolase Promotes a Th1 Response in Leishmania (Leishmania) infantum Cured Patients and in Asymptomatic Individuals Living in an Endemic Area of Leishmaniasis

The Leishmania (Leishmania) donovani nucleoside hydrolase NH36 is the main antigen of the Leishmune® vaccine and one of the promising candidates for vaccination against visceral leishmaniasis. The antigenicity of the N-terminal (F1), the central (F2), or the C-terminal recombinant domain (F3) of NH36 was evaluated using peripheral blood mononuclear cells (PBMC) from individuals infected with L. (L.) infantum from an endemic area of visceral leishmaniasis of Spain. Both NH36 and F1 domains significantly increased the PBMC proliferation stimulation index of cured patients and infected asymptomatic individuals compared to healthy controls. Moreover, F1 induced a 19% higher proliferative response than NH36 in asymptomatic exposed subjects. In addition, in patients cured from visceral leishmaniasis, proliferation in response to NH36 and F1 was accompanied by a significant increase of IFN-γ and TNF-α secretion, which was 42-43% higher, in response to F1 than to NH36. The interleukin 17 (IL-17) secretion was stronger in asymptomatic subjects, in response to F1, as well as in cured cutaneous leishmaniasis after NH36 stimulation. While no IL-10 secretion was determined by F1, a granzyme B increase was detected in supernatants from cured patients after stimulation with either NH36 or F1. These data demonstrate that F1 is the domain of NH36 that induces a recall cellular response in individuals with acquired resistance to the infection by L. (L.) infantum. In addition, F1 and NH36 discriminated the IgG3 humoral response in patients with active visceral leishmaniasis due to L. (L.) donovani (Ethiopia) and L. (L.) infantum (Spain) from that of endemic and non-endemic area controls. NH36 showed higher reactivity with sera from L. (L.) donovani-infected individuals, indicating species specificity. We conclude that the F1 domain, previously characterized as an inducer of the Th1 and Th17 responses in cured/exposed patients infected with L. (L.) infantum chagasi, may also be involved in the generation of a protective response against L. (L.) infantum and represents a potential vaccine candidate for the control of human leishmaniasis alone, or in combination with other HLA epitopes/antigens.

IFN-γ, IL-2, IP-10, and MIG as Biomarkers of Exposure to Leishmania spp., and of Cure in Human Visceral Leishmaniasis

New biomarkers are needed for monitoring the effectiveness of treatment for visceral leishmaniasis (VL). They might also improve the detection of the asymptomatic population in Leishmania-endemic areas. This paper examines the IL-2, IFN-γ, IFN-γ-induced protein 10 (IP-10), and monokine-induced-by-IFN-γ (MIG) levels in whole blood-stimulated in vitro with soluble Leishmania antigen (SLA)-taken from asymptomatic individuals and patients treated for VL living in a post-outbreak (Leishmania infantum) area in Spain, and in an endemic (Leishmania donovani) area of Bangladesh. IP-10 was found to be an accurate global marker of asymptomatic subjects with positive cellular/humoral tests, while MIG was found to be a better marker of contact with L. donovani than IL-2 but no for those with L. infantum. Determining IP-10, MIG, and IFN-γ levels proved useful in monitoring the cellular immune response following treatment for active disease caused by L. infantum.

Interleukin-2 as a marker for detecting asymptomatic individuals in areas where Leishmania infantum is endemic

No field method exists for identifying asymptomatic individuals in areas where Leishmania infantum is endemic. This work reports that, 24 h after stimulating whole blood with soluble Leishmania antigen (SLA), plasma interferon-γ (IFN-γ) and interleukin-2 (IL-2) become significantly elevated in samples from asymptomatic individuals (n=47) compared with those from negative controls (n=50), all of them recruited from a blood bank. When compared with the reference test SLA-lymphoproliferative assay, IL-2 appears as a new, 100% sensitive and specific marker for asymptomatic individuals with a positive cellular response (compared with 100% and 84.78%, respectively, for IFN-γ). Further studies in other transmission areas and in other cohorts of exposed people need to be performed to confirm these results. Once validated, IFN-γ and IL-2 levels in SLA-stimulated whole blood could be reliably used in the field to estimate the prevalence of those asymptomatic individuals with Leishmania-specific cellular immune responses.