Ex Vivo Immunogenicity Screening of Vaccine Candidate Antigen Combinations in Ethiopian Patients With Leishmaniasis (LEISHVAC)

Ex Vivo Immunogenicity Screening of Vaccine Candidate Antigen Combinations in Ethiopian Patients With Visceral and Cutaneous Leishmaniasis

This study assesses the immunoprevalence (presence of the induced T-cell response across different patients (and thus HLA types) of six prioritized IPX-derived Leishmania antigens, using Good Laboratory Practice-grade soluble Leishmania antigen (GLP-SLA) as a positive control. Longitudinal GLP-SLA stimulation validates its IFN-γ release assay performance to support licensing of a QuantiFERON-like test (Leish-IGRA) for treatment monitoring. IPX-derived Leishmania antigen screening focuses on day 0 and EOT, while GLP-SLA includes all timepoints. Induced T-cell responses by ex vivo stimulation of blood and tissue samples (lesion, bone marrow, or spleen) from patients with cutaneous and visceral leishmaniasis (two-centre cohort) before and after treatment will be verified. Samples from Ethiopian 'non-infected' healthy volunteers will be included in parallel to differentiate from Leishmania antigen-specific versus aspecific T-cell activation. The induced T-cell response will mainly be determined by the expressed IFN-γ levels after stimulation. Additional analyses are included to further characterize the activation and cytokine profiles of these IPX-derived Leishmania antigen-specific T-cells, while the breadth of the T-cell response will be determined by mapping the response across different patients (and thus different HLA types).

Study Overview

• Status: Recruiting
• Conditions: Leishmaniasis; Leishmaniasis, Cutaneous; Leishmaniasis, Visceral; Immunogenicity

Detailed Description

Despite decades of effort, to date, there is no licensed vaccine for human leishmaniasis. For subunit vaccine development, candidate antigens were mostly identified through in silico predictions or animal experimental models, and their immunogenicity, while promising in these systems, did not translate into sufficiently or consistently induced T-cell responses in humans.

To address this gap, the Institute of Tropical Medicine Antwerp (ITM) has recently applied a sensitive immunopeptidomics method (IPX) to directly identify naturally processed and MHC-presented Leishmania epitopes from tissue samples of patients with cutaneous leishmaniasis (CL). These epitopes, and their source antigens, represent clinically relevant human-derived vaccine candidate targets.

This study assesses the immunoprevalence (presence of the induced T-cell response across different patients (and thus HLA types) of six prioritized IPX-derived Leishmania antigens, using Good Laboratory Practice-grade soluble Leishmania antigen (GLP-SLA) as a positive control. Longitudinal GLP-SLA stimulation validates its IFN-γ release assay performance to support licensing of a QuantiFERON-like test (Leish-IGRA) for treatment monitoring. IPX-derived Leishmania antigen screening focuses on day 0 and EOT, while GLP-SLA includes all timepoints. Induced T-cell responses by ex vivo stimulation of blood and tissue samples (lesion, bone marrow, or spleen) from patients with cutaneous and visceral leishmaniasis (two-centre cohort) before and after treatment will be verified. Samples from Ethiopian 'non-infected' healthy volunteers will be included in parallel to differentiate from Leishmania antigen-specific versus aspecific T-cell activation. The induced T-cell response will mainly be determined by the expressed IFN-γ levels after stimulation. Additional analyses are included to further characterize the activation and cytokine profiles of these IPX-derived Leishmania antigen-specific T-cells, while the breadth of the T-cell response will be determined by mapping the response across different patients (and thus different HLA types).

• Study Type: Observational
• Enrollment (Estimated): 90

Contacts and Locations

• Study Contact: Name: Eshetu Molla, PhD; Phone Number: 00251 9 12 35 62 50; Email: eshetmolla@gmail.com
• Study Contact Backup: Name: Thao-Thy Pham, PhD; Phone Number: +32(0)33455227; Email: thaothypham@itg.be

Study Locations

• Ethiopia
  • Addis Ababa, Ethiopia
    • Recruiting
    • Armauer Hansen Research Institute
    • Contact: Eshetu Molla, PhD; Phone Number: +251(0)9 12 35 62 50; Email: eshetmolla@gmail.com
    • Contact: Shimelis Doni, MD; Phone Number: +251(0)9 11 64 20 60; Email: shimelis321@gmail.com
  • Gonder, Ethiopia
    • Recruiting
    • Leishmaniasis Research and Treatment Center
    • Contact: Mezgebu Asres, MD; Phone Number: +251921576259; Email: mezgebusilamsaw@yahoo.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Ethiopian population

Description

1. VL and CL patients

   INCLUSION CRITERIA:

   • Aged 18-65 years To minimize variability within this first study to verify induced T-cell responses specifically towards vaccine candidate target antigens/peptide pools, we focus on more robust adult immune responses. Children and elderly are vulnerable populations with divergent immune responses and are therefore excluded.

   • Suspected diagnosis of VL or CL, defined as:

     • VL: Clinically suspected VL presentation (e.g., prolonged fever, splenomegaly)
     • CL: Clinically suspected lesions (e.g., nodular, ulcerative, or plaque-like lesions) Including suspected VL and CL patients was done in earlier VL and CL studies (Clinicaltrials.gov Identifier: NCT05602610 and NCT05332093, >95% of suspected cohort confirmed to have VL or CL, respectively) to facilitate efficient recruitment flow for both the patient as the study team.
   • Willing and able to provide informed consent Ensures autonomy and understanding, allowing participants to fully understand their risks and benefits, and the possibility to withdraw at any time without affecting care.

   EXCLUSION CRITERIA:

   • Are currently enrolled in another interventional clinical study
   • Have known severe comorbidities (e.g., autoimmune disease, HIV, tuberculosis, leprosy, or malaria)
   • Have known pregnancy
   • Cognitively impaired individuals
   • Have received immunosuppressive drugs in the past month
   • Have received a vaccine in the past month
   • Have received modern antileishmanial treatment in the past month
   • Are on anticoagulation medication or have bleeding disorders that would contraindicate safe blood or tissue sampling

   • For CL patients:

     • Primary lesion size < 2 cm
     • Too difficult or too painful sampling zone (e.g., close to the mucosa or lymphatic system, on joints, eyelid or ear)
     • Not eligible for systemic SSG treatment
2. Ethiopian 'non-infected' healthy volunteers

INCLUSION CRITERIA:

• Aged 18-65 years Matching the age range of VL and CL patients
• Resides in Addis Ababa An uninfected control group is included to distinguish true antigen-specific T-cell responses from non-specific (background) T-cell activation. This control group should ideally consist of healthy individuals without prior symptomatic or asymptomatic exposure to Leishmania, as previous (unknown) asymptomatic infections could lead to detectable Leishmania-specific T-cell responses and thus confound background baseline measurements. To minimize this risk, we will recruit healthy volunteers from 'non-infected' areas, specifically the Addis Ababa region, and apply strict (retrospective) exclusion criteria to ensure absence of prior Leishmania exposure.
• Generally healthy Ensures volunteers who are not in a state of severe medical nor socioeconomic vulnerability, to ensure that participation is not unduly influenced by financial compensation.
• Willing and able to provide informed consent. Ensures autonomy and understanding, allowing participants to fully understand their risks and benefits, and the possibility to withdraw at any time without affecting care.

• Passed autonomy and voluntariness assessment (questions listed below) to further ensure autonomy and understanding.

  • Can you explain in your own words what participation involves and that it is voluntary?
  • Would saying no affect your access to care in any way?
  • Is the compensation offered influencing your decision in a way that makes you feel you must participate?
  • Would not receiving this compensation cause you significant difficulty?

EXCLUSION CRITERIA:

• Have history of contracting VL or CL
• Cohabitate with a person treated for CL/VL within the past 12 months

• Residence or overnight stays in any of these areas within the past 5 years should be considered potentially exposed, even if they reside in the capital.

  • Kebeles in Addis: Saris, Kality, and Akaki
  • Ethiopian highlands: widespread foci for CL in Amhara (South Gondar, North Gondar, South Wollo, North Wollo), Tigray (Wukro, Mekelle surroundings), Oromia (Sebeta, Bale, Jimma), and SNNPR (Silte, Gurage, Sidama highlands).
  • VL endemic lowland/hotspot areas: Afar, Somali Region, Benishangul-Gumuz, Metema-Humera lowlands (Amhara/Tigray border), and South Omo (SNNPR).
• Have known severe comorbidities (e.g., autoimmune disease, HIV, tuberculosis, leprosy, and malaria)
• Have known pregnancy
• Cognitively impaired individuals
• Have received immunosuppressive drugs in the past month
• Have received a vaccine in the past month
• Are on anticoagulation medication or have bleeding disorders that would contraindicate safe blood or tissue sampling
• If their Leish-IGRA demonstrate positive values, the participant will be retrospectively excluded as this indicates the presence of a past Leishmania infection.

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort
Ethiopian non-infected healthy volunteers
cutaneous leishmaniasis
visceral leishmaniasis

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
To determine the immunoprevalence of IPX-derived Leishmania antigens and their combinations in Ethiopian patients with VL and CL.	Proportion of patients that demonstrate an induced T-cell response (represented by IFN-γ expression) after ex vivo stimulation of IPX-derived antigens Leishmania and combinations.	"Day 0" (baseline) until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)

Secondary Outcome Measures

Outcome Measure	Time Frame
To further characterize the phenotype (e.g., flow cytometry, single-cell sequencing) and polyfunctionality (multiplex cytokine determination) of the induced T-cell response after ex vivo stimulation with IPX-derived Leishmania antigens and GLP-SLA	"Day 0" (baseline) until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)
To compare the induced T-cell response of IPX-derived Leishmania antigens with GLP-SLA in blood versus tissues, by clinical presentation	"Day 0" (baseline) until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)
To determine the dynamics of the induced T-cell response of IPX-derived Leishmania antigens versus GLP-SLA before and at end of successful versus failed treatment	"Day 0" (baseline) until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)
To assess the predictive value of the Leish-IGRA for treatment outcome in CL and VL patients before, during and at end of treatment	"Day 0" (baseline), "Day 7", until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)
To characterize the HLA-TCR interactions involved in the recognition of IPX-derived Leishmania antigens through TCR sequencing and HLA typing	"Day 0" (baseline) until "Day 17" or "Day 28" (end of treatment, may vary due to treatment)

Collaborators and Investigators

• Sponsor: Institute of Tropical Medicine, Belgium
• Collaborators: Universiteit Antwerpen
• Investigators: Principal Investigator: Wim Adriaensen, PhD, Institute of Tropical Medicine Antwerp; Principal Investigator: Thao-Thy Pham, Institute of Tropical Medicine Antwerp; Principal Investigator: Eshetu Molla, PhD, Armauer Hansen Research Institute, Ethiopia; Principal Investigator: Endalamaw Gadisa, PhD, Armauer Hansen Research Institute, Ethiopia

Study record dates

Study Major Dates

• Study Start (Actual): May 26, 2026
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: May 15, 2026
• First Submitted That Met QC Criteria: August 19, 2026
• First Posted (Actual): August 24, 2026

Study Record Updates

• Last Update Posted (Actual): August 24, 2026
• Last Update Submitted That Met QC Criteria: August 19, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: leishmania vaccine candidate antigens; leishmania vaccine; leishmaniasis vaccine
• Additional Relevant MeSH Terms: Vector Borne Diseases; Infections; Protozoan Infections; Parasitic Diseases; Skin Diseases; Skin Diseases, Infectious; Skin Diseases, Parasitic; Euglenozoa Infections; Skin and Connective Tissue Diseases; Leishmaniasis; Leishmaniasis, Visceral; Leishmaniasis, Cutaneous
• Other Study ID Numbers: 1950/25

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: IPD can be requested via the Data Access Committee of the Institute of Tropical Medicine Antwerp (https:// www. itg. be/ en/ resea rch/ data-shari ng-and-open-access) via a formal application and signed Data Sharing Agreement. In line with the study's data sharing policy, these datasets will be made available one year after completion of all planned primary publications.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No