Immune Responses After Human Subject Challenge With Sand Fly Bites

Study Overview
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Brief Summary
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Sand flies can carry the infection leishmaniasis (a parasite). The purpose of this study is to evaluate the human immune response to uninfected laboratory raised sand fly bites and select from the immune response to sand fly saliva, possible substances to use for a future vaccine to protect against the parasite leishmaniasis.

Detailed Description
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Based on travel history and possible exposure, subjects were entered into one of 2 arms, Ph. dubosqui or Lu. lutzomyia controlled sand fly repeated feedings. At baseline a pheresis was done to collect baseline cells. Subjects received sand fly bites on a q2 week schedule for 2 months followed by a q2 months schedule for one year. They had an option to extend for a late recall feeding at 18 months, when a skin biopsy was performed 48 hours after sand fly bites. Currently the study is fully enrolled and all human subject contact is complete. We (laboratory at NIAID) are studying the humoral, cellular immune responses using blood samples, and cytokine expression in the skin biopsy samples.

Official Title
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Immune Responses After Human Subject Challenge With Sand Fly Bites: Exploratory Study for Selection of Potential Leishmania Vaccine Antigen Candidates

Conditions
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Healthy

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18-50 Plans to remain in DC area for at least one year willingness to participate in all study procedures general good health military health care beneficiary able to provide informed consent Exclusion Criteria: Prior travel to geographic areas where leishmania transmitting sand flies are common positive antibody to sand fly saliva on screening blood test pregnancy elevated serum IgE history of chronic medical illness adult history of treatment requiring anemia large reactions to insect bites history of multiple vasovagal reactions to phlebotomy difficult venous access for phlebotomy Taking medications that could interfere with immune responses

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Phlebotomus group<br>Those in the Phlebotomus group will have exposure to P. duboscqui sand fly | |
| Lutzomyia group<br>Those placed in this group will receive exposure to L. longipalpis sand fly bites. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Human Th1 immune response to specific sand fly salivary proteins | Subject blood will be obtained at set points after repeated controlled sand fly feedings, duration for 20 minutes. Sand fly salivary molecules that demonstrate a strong Th1 immune response in these human PBMC, and little Th2 cytokine induction will be considered for development as future leishmania vaccine antigen candidates. | 6-18 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Sandfly, leishmaniasis, immune response, individuals age 18-50