Prevalence of Hookworm Infection and Community Preparedness for Hookworm Vaccine Trials in Endemic Areas of Brazil
Na-ASP-2 is a protein expressed during the larval stage of the N. americanus hookworm life cycle. In a clinical study in previously hookworm-infected adults in Brazil, this protein induced urticarial reactions (rash) in a subset of volunteers. The clinical trial component of this study involves skin testing for immediate-type hypersensitivity to the Na-ASP-2 Antigen. Both prick-puncture and intradermal tests will be applied.
|Study Design:||Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Diagnostic
|Official Title:||Determination of Prevalence and Intensity of Hookworm Infection and Community Preparedness for Hookworm Vaccine Trials in Endemic Areas of Northeastern Minas Gerais, Brazil|
- Size of wheal diameter at site of skin test application, measured 15 minutes after injection [ Time Frame: 15 minutes after skin test application ] [ Designated as safety issue: Yes ]
- Anti-Na-ASP-2 IgE antibody level on day of skin test reaction [ Time Frame: Upon skin testing ] [ Designated as safety issue: No ]
|Study Start Date:||August 2009|
|Study Completion Date:||December 2012|
|Primary Completion Date:||January 2012 (Final data collection date for primary outcome measure)|
Experimental: Na-ASP-2 Hookworm Antigen Skin Test
All participants will be skin tested with Na-ASP-2 skin test reagent applied to their arms, using both the prick-puncture and intradermal techniques.
Biological: Na-ASP-2 Skin Test Reagent
Na-ASP-2 Hookworm Skin Test Reagent, 1-1000 mcg/mL solution
The clinical testing of the Na-ASP-2 Skin Test Reagent to detect Immediate-type hypersensitivity to the Na-ASP-2 hookworm antigen will be conducted as part of a larger, on-going observational study of the prevalence and intensity of hookworm infection currently underway in Brazil. Eligible adult participants (ages 18-45 years) in this observational study will be invited to undergo the skin testing procedure. Skin testing will only be performed if they agree and sign the supplemental informed consent form for this skin testing procedure.
- Study site: Americaninhas Vaccine Center, Americaninhas, Minas Gerais, Brazil
- Number of participants to be skin tested: approximately 150 adults
- Duration of the skin testing procedures: up to 1 month; each participant will undergo skin testing and a follow-up blood collection 21+/-7 days after skin testing.
Each participant will have both skin prick-puncture and intradermal skin tests applied on the same study day. The prick-puncture and intradermal tests will be applied sequentially to the volar aspects of the participant's forearms:
- Skin prick-puncture: three different concentrations of Na-ASP-2 solution (10, 100, and 1000 μg/mL) will be applied sequentially in duplicate, to the left forearm.
- Intradermal: one concentration of Na-ASP-2 (100 μg/mL) will be injected, in duplicate, to the right forearm.
- Allergen diluent and histamine solutions will be utilized as the negative and positive controls, respectively, for both the skin prick-puncture and intradermal tests.
- Participants will be observed in the study clinic for at least 30 minutes following application of the skin tests, and will be examined 2 and 7 days following skin testing.
- Sizes of the wheal and erythema reactions for each application will be recorded and graded in comparison to the histamine positive control reaction.
- Each participant will have blood collected via venipuncture (a maximum of 25 mL) immediately prior to application of the skin tests, and between 2 and 4 weeks after skin testing, in order to measure antibodies (particularly IgG and IgE) to Na-ASP-2 using an ELISA procedure.
|Centro de Pesquisas Rene Rachou|
|Belo Horizonte, Minas Gerais, Brazil|
|Principal Investigator:||Jeffrey Bethony, PhD||Albert B. Sabin Vaccine Institute|