Protein biomarkers discriminate Leishmania major-infected and non-infected individuals in areas endemic for cutaneous leishmaniasis

A Prospective cohort study of zoonotic cutaneous leishmaniasis in tunisia: Clinical and Immunological features and immune correlates of protection

BACKGROUND

This study aimed to define immunological markers of exposure to L. major parasites and identify correlates of protection against infection.

METHODS

We analyzed a cohort of 790 individuals at risk of developing ZCL living in endemic areas with varying L. major infection prevalence. One area had a high infection prevalence indicated by high proportions of leishmanin skin test (LST) positive subjects, while the other areas were recent foci with lower infection prevalence. Blood samples were collected before the transmission season to measure Interferon gamma (IFN-γ), Interleukin 10 (IL-10), and Granzyme B (GrB) levels in response to parasite stimulation in peripheral blood mononuclear cells. A one-year follow-up period involved active detection of new ZCL cases to estimate disease incidence after a transmission season and identify immune correlates of protection.

RESULTS

The study population showed heterogeneity in parasite contact, evident from specific scars and/or positive LST results, significantly higher in the old focus compared to recent foci. IFN-γ and GrB were markers of parasite exposure and reliable indicators of immunity to L. major. Positive correlations were observed between IFN-γ/IL-10 and GrB/IL-10 ratios and LST results. Unexpectedly, only 29 new ZCL cases (4%) appeared after a transmission season, with 27 cases reported in recent foci and 2 in the oldest focus. Our findings indicate that individuals in L. major endemic areas are likely to develop ZCL regardless of their LST status. We showed that high pre-transmission season levels of IFN-γ and GrB produced by PBMC, along with a high IFN-γ/IL-10 ratio, were associated with protection.

CONCLUSION

This study on a large cohort at risk of ZCL confirmed IFN-γ and GrB as protective factors against the disease. A high IFN-γ/IL-10 ratio, but not GrB/IL-10 ratio was associated with resistance. These results are valuable for developing and evaluating of a vaccine against human leishmaniasis.

Immunomodulatory and biological properties of helminth-derived small molecules: Potential applications in diagnostics and therapeutics

Parasitic helminths secrete and excrete a vast array of molecules known to help skew or suppress the host's immune response, thereby establishing a niche for sustained parasite maintenance. Indeed, the immunomodulatory potency of helminths is attributed mainly to excretory/secretory products (ESPs). The ESPs of helminths and the identified small molecules (SM) are reported to have diverse biological and pharmacological properties. The available literature reports only limited metabolites, and the identity of many metabolites remains unknown due to limitations in the identification protocols and helminth-specific compound libraries. Many metabolites are known to be involved in host-parasite interactions and pathogenicity. For example, fatty acids (e.g., stearic acid) detected in the infective stages of helminths are known to have a role in host interaction through facilitating successful penetration and migration inside the host. Moreover, excreted/secreted SM detected in helminth species are found to possess various biological properties, including anti-inflammatory activities, suggesting their potential in developing immunomodulatory drugs. For example, helminths-derived somatic tissue extracts and whole crude ESPs showed anti-inflammatory properties by inhibiting the secretion of proinflammatory cytokines from human peripheral blood mononuclear cells and suppressing the pathology in chemically-induced experimental mice model of colitis. Unlike bigger molecules like proteins, SM are ideal candidates for drug development since they are small structures, malleable, and lack immunogenicity. Future studies should strive toward identifying unknown SM and isolating the under-explored niche of helminth metabolites using the latest metabolomics technologies and associated software, which hold potential keys for finding new diagnostics and novel therapeutics.

Potential biomarkers of immune protection in human leishmaniasis

Leishmaniasis is a vector-borne neglected tropical disease endemic in over 100 countries around the world. Available control measures are not always successful, therapeutic options are limited, and there is no vaccine available against human leishmaniasis, although several candidate antigens have been evaluated over the last decades. Plenty of studies have aimed to evaluate the immune response development and a diverse range of host immune factors have been described to be associated with protection or disease progression in leishmaniasis; however, to date, no comprehensive biomarker(s) have been identified as surrogate marker of protection or exacerbation, and lack of enough information remains a barrier for vaccine development. Most of the current understanding of the role of different markers of immune response in leishmaniasis has been collected from experimental animal models. Although the data generated from the animal models are crucial, it might not always be extrapolated to humans. Here, we briefly review the events during Leishmania invasion of host cells and the immune responses induced against Leishmania in animal models and humans and their potential role as a biomarker of protection against human leishmaniasis.

Enhanced production of pro-inflammatory cytokines and chemokines in Ethiopian cutaneous leishmaniasis upon exposure to Leishmania aethiopica

The clinical course and outcome of cutaneous leishmaniasis (CL) vary due to the infecting Leishmania species and host genetic makeup that result in different immune responses against the parasites. The host immune response to Leishmania aethiopica (L.aethiopica), the causative agent of CL in Ethiopia, is poorly understood. To contribute to the understanding of the protective immune response in CL due to L.aethiopica, we characterized the cytokine response to L. aethiopica in patients with the localized form of CL (LCL) and age-and sex-matched apparently healthy controls. By applying a whole blood based in vitro culture we found enhanced release of TNF, IL-6, MCP-1 or CCL2, IP-10 or CXCL10, MIP-1β or CCL4 and IL-8 or CXCL8- but not of IL-10CL patients in response to L. aethiopica compared to the controls. No difference was observed between LCL cases and controls in the secretion of these cytokines and chemokines in whole blood cultures treated with the TLR-ligands LPS, MALP-2 or polyI: C. The observed increased secretion of the pro-inflammatory cytokines/chemokines reflects an enhanced response against the parasites by LCL patients as compared to healthy controls rather than a generally enhanced ability of blood leukocytes from LCL patients to respond to microbial constituents. Our findings suggest that the enhanced production of pro-inflammatory cytokines/chemokines is associated with localized cutaneous leishmaniasis caused by L.aethiopica.

Profiling inflammatory response in lesions of cutaneous leishmaniasis patients using a non-invasive sampling method combined with a high-throughput protein detection assay

BACKGROUND

Cutaneous leishmaniasis (CL) is an infection caused by Leishmania (L.) protozoa transmitted through the bite of infected sand fly. Previously, invasive sampling of blood and skin along with low throughput methods were used for determination of inflammatory response in CL patients.

AIMS/METHODOLOGY

We established a novel approach based on a non-invasive adhesive tape-disc sampling combined with a powerful multiplexing technique called proximity extension assay for profiling 92 inflammatory cytokines, chemokines and surface molecules in the lesions of CL patients infected with L. tropica. Sample collection was done non-invasively by using adhesive tape-discs from lesion and normal skin of 33 L. tropica positive patients.

RESULTS

Out of 92 inflammatory proteins, the level of 34 proteins was significantly increased in the lesions of CL patients compared to their normal skin. This includes the chemokines CCL2, CCL3, CCL4, CXCL1, CXCL5, CXCL9, CXCL10 and CXCL11, together with the interleukins IL-6, IL-8, IL-18, LIF and OSM. The remaining significantly changed inflammatory proteins include 7 surface molecules and receptors: CD5, CD40, CDCP1, 4E-BP1, TNFRSF9, IL-18R1 and OPG as well as 16 other cytokines and proteins: MMP-1, CSF-1, VEGFA, uPA, EN-RAGE, LAP TGF-β1, HGF, MMP-10, CASP-8, TNFSF14, STAMPB, ADA, TRAIL and ST1A1. Further, 13 proteins showed an increasing trend, albeit not statistically significant, in the CL lesions, including TGF-α, CCL23, MCP-2, IL-12B, CXCL6, IL-24, FGF-19, TNFβ, CD6, TRANCE, IL10, SIR2 and CCL20.

CONCLUSION

We herein report a novel approach based on a non-invasive sampling method combined with the high-throughput protein assay for profiling inflammatory proteins in CL lesions. Using this approach, we could profile inflammatory proteins in the lesions from CL patients. This new non-invasive approach may have implications for studying skin inflammatory mediators in CL and other skin disorders.

Design of multi-epitope peptides containing HLA class-I and class-II-restricted epitopes derived from immunogenic Leishmania proteins, and evaluation of CD4+ and CD8+ T cell responses induced in cured cutaneous leishmaniasis subjects

Human leishmaniasis is a public health problem worldwide for which the development of a vaccine remains a challenge. T cell-mediated immune responses are crucial for protection. Peptide vaccines based on the identification of immunodominant T cell epitopes able to induce T cell specific immune responses constitute a promising strategy. Here, we report the identification of human leukocyte antigen class-I (HLA-I) and -II (HLA-II)-restricted multi-epitope peptides from Leishmania proteins that we have previously described as vaccine candidates. Promastigote Surface Antigen (PSA), LmlRAB (L. major large RAB GTPase) and Histone (H2B) were screened, in silico, for T cell epitopes. 6 HLA-I and 5 HLA-II-restricted multi-epitope peptides, able to bind to the most frequent HLA molecules, were designed and used as pools to stimulate PBMCs from individuals with healed cutaneous leishmaniasis. IFN-γ, IL-10, TNF-α and granzyme B (GrB) production was evaluated by ELISA/CBA. The frequency of IFN-γ-producing T cells was quantified by ELISpot. T cells secreting cytokines and memory T cells were analyzed by flow cytometry. 16 of 25 peptide pools containing HLA-I, HLA-II or HLA-I and -II peptides were able to induce specific and significant IFN-γ levels. No IL-10 was detected. 6 peptide pools were selected among those inducing the highest IFN-γ levels for further characterization. 3/6 pools were able to induce a significant increase of the percentages of CD4+IFN-γ+, CD8+IFN-γ+ and CD4+GrB+ T cells. The same pools also induced a significant increase of the percentages of bifunctional IFN-γ+/TNF-α+CD4+ and/or central memory T cells. We identified highly promiscuous HLA-I and -II restricted epitope combinations from H2B, PSA and LmlRAB proteins that stimulate both CD4+ and CD8+ T cell responses in recovered individuals. These multi-epitope peptides could be used as potential components of a polytope vaccine for human leishmaniasis.

The control of leishmaniasis, a neglected tropical disease of public health importance, caused by protozoan parasites of the genus Leishmania, mainly relies on chemotherapy, which is highly toxic. Currently, there is no vaccine against human leishmaniasis. Peptide-based vaccines consisting of T cell epitopes identified within proteins of interest by epitope predictive algorithms are a promising strategy for vaccine development. Here, we identified multi-epitope peptides composed of HLA-I and -II-restricted epitopes, using immunoinformatic tools, within Leishmania proteins previously described as potential vaccine candidates. We showed that multi-epitope peptides used as pools were able to activate IFN-γ producing CD4+ as well as CD8+ T cells, both required for parasite elimination. In addition, granzyme B-producing CD4+ T cells, bifunctional CD4+ IFN-γ+/TNF-α+ and/or TNF-α+/IL-2+ T cells as well as CD4+ and CD8+ central memory T cells, all involved in Leishmania infection control, were significantly increased in response to multi-epitope peptide stimulation. As far as we know, no study has described the detection of both CD4+ and CD8+ T cell populations in response to stimulation by both HLA-I and II-restricted peptides in humans. The immunogenic HLA-I and -II-restricted multi-epitope peptides identified in this study could constitute potential vaccine candidates against human leishmaniasis.

Label-free quantitative proteomic analysis reveals potential biomarkers for early healing in cutaneous leishmaniasis

Background

Leishmaniasis is a parasitic disease caused by more than 20 species of the Leishmania genus. The disease is globally distributed and is endemic in 97 countries and three territories in the tropical and subtropical regions. The efficacy of the current treatments is becoming increasingly low either due to incomplete treatment or resistant parasites. Failure of treatment is frequent, and therefore, the search for early biomarkers of therapeutic response in cutaneous leishmaniasis (CL) is urgently needed.

Objective

The aim of this study was to compare the proteomic profiles in patients with CL before and after 7 days of treatment and identify early biomarkers of curative response.

Methods

Four patients with a parasitological diagnosis of leishmaniasis with confirmation of species by PCR-RFLP were recruited. All patients had a single lesion, and a protein from the middle of the ulcer was quantified by liquid chromatography and mass spectrometry.

Results

A total of 12 proteins showed differential expression in the comparative LC-electrospray ionization MS/MS (LC-ESI-MS/MS) triplicate analysis. Seven of them were up-regulated and five of them were down-regulated. Calcium binding proteins A2, A8, and A9 and hemoglobin subunits alpha-2 and delta showed high correlation with epidermis development and immune response.

Conclusion

We identified changes in the profiles of proteins that had a positive therapeutic response to the treatment. The proteins identified with differential expression are related to the reduction of inflammation and increased tissue repair. These proteins can be useful as biomarkers for early monitoring of therapeutic response in CL.

Biomarkers of Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) is an immune-mediated skin pathology caused mainly by Leishmania (L.) major, Leishmania tropica, Leishmania braziliensis, L. mexicana, and L. amazonensis. The burden of CL in terms of morbidity and social stigmas are concentrated on certain developing countries in Asia, Africa, and South America. People with asymptomatic CL represent a large proportion of the infected individuals in the endemic areas who exhibit no lesion and can control the infection by as yet not fully understood mechanisms. Currently, there is no approved prophylactic control measure for CL. Discovery of biomarkers of CL infection and immunity can inform the development of more precise diagnostics tools as well as curative or preventive strategies to control CL. Herein, we provide a brief overview of the state-of-the-art for the biomarkers of CL with a special emphasis on the asymptomatic CL biomarkers. Among the identified CL biomarkers so far, direct biomarkers which indicate the actual presence of the infection as well as indirect biomarkers which reflect the host's reaction to the infection, such as alterations in delayed type hypersensitivity, T-cell subpopulations and cytokines, adenosine deaminase, and antibodies against the sand fly saliva proteins are discussed in detail. The future avenues such as the use of systems analysis to identify and characterize novel CL biomarkers are also discussed.

Comparison of pro-inflammatory cytokines of non-healing and healing cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) heals spontaneously within several weeks or months, but, in rare cases, CL-active lesions last for many years. In this study, we assessed cell-mediated immunity in non-healing CL through the measurement of three pro-inflammatory cytokines: Interferon-γ (IFN-γ), IL-17a and CXCL-11. For this, 32 patients afflicted with healing or non-healing CL were recruited in this study. Peripheral blood mononuclear cells (PBMCs) of every patient were treated with three antigens: purified protein derivative (PPD), soluble Leishmania antigen (SLA) and phytohaemagglutinin (PHA). Cytokine quantification was performed using enzyme-linked immunosorbent assay (ELISA) method. Results of our study showed that neither cytokine produced in the presence of a PPD stimulator (as an irrelevant antigen) significantly differed between the healing and non-healing groups (P-value ≥0.05 for all of them). However, IFN-γ, CXCL-11 and IL-17a levels produced in the presence of PHA or SLA were significantly higher within the healing than in the non-healing group (P-value <0.01 for all of them). It seems that appropriate levels of IFN-γ, as well as IL-17a and CXCL-11, contribute to the control of Leishmania infection.