Baseline Assessment of Skin Resident Memory T Cells in Healthy Unvaccinated Participants

NCT07636551 | Not Yet Recruiting

• 1 other identifier: 1966/25
• Study Type: interventional
• Target: 40
• Locations: 1 country
• Sites: 1

Brief Summary

In The main GeKoSkimm trial (= A randomized controlled trial to compare the immunogenicity and skin imprinting of intradermal, subcutaneous and intramuscular yellow fever vaccination) the investigators try to understand whether the route of injection (in the muscle, under the skin, or in the skin) when giving the yellow fever vaccine affects the strength of the body's immune response to yellow fever. More in particular the investigators want to know how well the immune responses are retained in the skin, as this is the place where the virus enters the body after a mosquito bite. This will be important for vaccines against infections transmitted via bites of mosquitoes and ticks, such as yellow fever virus. Because this is the first attempt on human samples and only skin samples after vaccination with yellow fever vaccine are available, the investigators want to assess the baseline or background immune response in 'unvaccinated' skin. Therefore, 40 volunteers will be recruited that have not been previously vaccinated against yellow fever and will not receive a yellow fever vaccine during this study. The participant will be requested to provide two skin samples from the upper arm and a blood sample to confirm their vaccination status regarded to yellow fever.

Conditions

Yellow Fever (Healthy Volunteers); Biopsy/Methods

Outcome Measures

Primary Outcomes (1)

• Estimate the baseline number and proportion of skin-resident memory T cells against YFV (YFV-TRM) in the skin of unvaccinated and healthy volunteers against YFV

  The number and proportion of YFV-specific T cells within the skin-resident lymphocyte parent population at visit 2, measured by flow cytometry.

  Day 14 (Visit 2)

Secondary Outcomes (1)

• Estimate the baseline number and proportion of circulating effector- (YFV-TEM) and central-memory T cells against YFV (YFV-TCM) in the blood of unvaccinated and healthy volunteers against YFV

  Day 0 (Visit 1)

Other Outcomes (4)

• Estimate the baseline cytokine and chemokine concentrations in peripheral and capillary blood, and microbiopsies of unvaccinated and healthy volunteers against YFV

  Day 14 (Visit 2)

• Estimate the baseline YFV-specific IgG/IgM levels in peripheral and capillary blood of unvaccinated and healthy volunteers

  Day 14 (Visit 2)

• Describe the spatially-resolved position of TRM cells in the skin of unvaccinated and healthy volunteers against YFV

  D14 (Visit 2)

Study Arms (1)

Healthy unvaccinated participants against yellow fever virus

OTHER

Healthy participants that have not been vaccinated against yellow fever virus

Procedure: Skin punch biopsy; Procedure: Blood samples

Interventions

Skin punch biopsy PROCEDURE

2 x 4mm skin punch biopsies in the upper arm will be taken from each participant at visit 2 with additional microsampling (microbiopsy and wound blood sampling)

Healthy unvaccinated participants against yellow fever virus

Blood samples PROCEDURE

Blood sampling of 15 mL (10mL Lithium-Heparine + 5 mL SST) is performed on Visit 1 to confirm their vaccination status regarded to yellow fever

Healthy unvaccinated participants against yellow fever virus

Eligibility Criteria

• Age: 18 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• BMI \>/=18,5 kg/m2 and ≤35 kg/m2
• Agreement to share and discuss participant's medical history and medical records when relevant with the study team
• Able and willing to provide written informed consent
• Agreement to refrain from blood donation and other vaccinations during the study

You may not qualify if:

• Participants with a confirmed flavivirus infection in the past
• Participants who received a flavivirus vaccination prior to enrolment (e.g. YFV, Japanese encephalitis virus, tick-borne encephalitis virus, Dengue)
• Receipt of any vaccine (licensed or experimental) within 30 days prior to enrolment or during the study
• Active participation in another interventional clinical study with active substance intake or large medical procedures affecting the study procedures during or 1 month prior to enrolment
• Any confirmed or suspected immunosuppressive or immunodeficient state (incl. cancer and human immunodeficiency virus/hepatitis B virus infection); asplenia; recurrent severe infections and use of immunosuppressant medication (including antineoplastic and immunomodulating agents or radiotherapy) within the last 6 months prior to enrolment, except topical or short-term oral steroids (\<2 weeks of daily receipt of 20 mg of prednisone or equivalent). Refer to annex 1 for a list of immunosuppressive medication
• Severe and/or uncontrolled cardiovascular disease, respiratory disease, gastrointestinal disease, liver disease, renal disease, endocrine disorder, psychiatric and neurological illness (mild/moderate well controlled comorbidities are allowed)
• History of bleeding disorder (e.g. factor deficiency, coagulopathy or platelet disorder), or prior history of significant bleeding or bruising following venipuncture
• Any significant disease, disorder or planned surgery which may affect the ability of the volunteer to participate in the study or impact (skin) immunity homeostasis
• Suspected or known alcohol or drug dependency
• Known pregnancy
• Tendency to keloid (scar) formation in response to skin damage
• Skin diseases or tattoo at the biopsy site
• In the opinion of the investigator, unlikely compliance to the requirements of the study
• History of thymus dysfunction (including myasthenia gravis, thymoma) or thymectomy
• Individuals who are working at the investigational site or within the research team of this study

Sponsors & Collaborators

• Institute of Tropical Medicine, Belgium: lead

Study Sites (1)

Clinical Trial Site of the Institute of Tropical Medicine

Antwerp, Belgium

Location

MeSH Terms

Conditions

Yellow Fever

Interventions

Blood Specimen Collection

Condition Hierarchy (Ancestors)

Mosquito-Borne Diseases; Vector Borne Diseases; Infections; Arbovirus Infections; Virus Diseases; Flavivirus Infections; Flaviviridae Infections; RNA Virus Infections; Hemorrhagic Fevers, Viral

Intervention Hierarchy (Ancestors)

Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Investigative Techniques

Central Study Contacts

Prof. Dr. Patrick Soentjens

CONTACT

+3232476641; psoentjens@itg.be

Wim Adriaensen

CONTACT

wadriaensen@itg.be

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: May 18, 2026
• First Posted: June 9, 2026
• Study Start: June 15, 2026
• Primary Completion (Estimated): November 15, 2026
• Study Completion (Estimated): November 15, 2026
• Last Updated: June 9, 2026

Record last verified: 2026-05

Locations

BE (1)