Immune Responses After Human Subject Challenge With Sand Fly Bites

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

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.

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.

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