Clinical Trial: Development of a Skin Test for the Na-ASP-2 Hookworm Antigen

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Development of a Skin Test to Detect Immediate-type Hypersensitivity to the Experimental Na-ASP-2 Hookworm Antigen

Brief Summary: 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. This study will evaluate solutions of varying concentrations of the protein in both a skin prick-puncture and intradermal test that will eventually be used to screen volunteers living in hookworm endemic areas who are being considered as potential participants in vaccine trials, to reduce the potential of inducing allergic reactions in those vaccinated with the Na-ASP-2 Hookworm Vaccine.

Detailed Summary:

  • Study site: George Washington University Medical Center
  • Number of participants: up to 15
  • Study duration: up to 3 months; each participant will undergo a minimum of one screening visit and one study visit.

  • 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:

    1. Skin prick-puncture: four different concentrations of Na-ASP-2 solution (1, 10, 100, and 1000 μg/mL) will be applied simultaneously in duplicate, to the left forearm.
    2. Intradermal: three different concentrations of Na-ASP-2 (10, 100, and 1000 μg/mL) will be injected simultaneously, in duplicate, to the right forearm.
    3. Allergen diluent and histamine solutions will be utilized as the negative and positive controls, respectively, for both the skin prick-puncture and intradermal tests.
    4. Participants will be observed in the study clinic for at least 30 minutes following application of the skin tests, and will be contacted via telephone 2 days following skin testing.
    5. 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, in order to measure antibodies (particularly IgG and IgE) to Na-ASP-2 using an ELISA procedure.
    • Sponsor: Albert B. Sabin Vaccine Institute

    Current Primary Outcome: 100 Mcg/ml Na-ASP-2 Prick-puncture Skin Test [ Time Frame: 15 minutes after skin test application ]

    Mean grade of wheal reaction after 2 applications of the skin test reagent per participant. For each skin test reaction, the grade of the test was determined based on the mean of the longest and orthogonal diameters, which was then compared to the equivalent measurements of a histamine solution positive control that was applied at the same time as the test. Grading was as follows:

    0 no discernible wheal

    1. < ½ histamine diameter
    2. ≥ ½ histamine; < histamine diameter
    3. = size of histamine control ± 1 mm
    4. > histamine diameter; < 2x diameter
    5. ≥ 2x histamine control


    Original Primary Outcome: Size of skin test reactions to application of prick-puncture and intradermal injections of test antigen solutions and positive and negative controls [ Time Frame: 15 minutes after skin test application ]

    Current Secondary Outcome:

    • 1000 Mcg/ml Na-ASP-2 Prick-puncture Skin Test [ Time Frame: 15 minutes after skin test application ]

      Mean grade of wheal reaction after 2 applications of the skin test reagent per participant. For each skin test reaction, the grade of the test was determined based on the mean of the longest and orthogonal diameters, which was then compared to the equivalent measurements of a histamine solution positive control that was applied at the same time as the test. Grading was as follows:

      0 no discernible wheal

      1. < ½ histamine diameter
      2. ≥ ½ histamine; < histamine diameter
      3. = size of histamine control ± 1 mm
      4. > histamine diameter; < 2x diameter
      5. ≥ 2x histamine control
    • 100 Mcg/ml Na-ASP-2 Intradermal Skin Test [ Time Frame: 15 minutes after skin test application ]

      Mean grade of wheal reaction after 2 applications of the skin test reagent per participant. For each skin test reaction, the grade of the test was determined based on the mean of the longest and orthogonal diameters, which was then compared to the equivalent measurements of a histamine solution positive control that was applied at the same time as the test. Grading was as follows:

      0 no discernible wheal

      1. < ½ histamine diameter
      2. ≥ ½ histamine; < histamine diameter
      3. = size of histamine control ± 1 mm
      4. > histamine diameter; < 2x diameter
      5. ≥ 2x histamine control
    • 1000 Mcg/ml Na-ASP-2 Intradermal Skin Test [ Time Frame: 15 minutes after skin test application ]

      Mean grade of wheal reaction after 2 applications of the skin test reagent per participant. For each skin test reaction, the grade of the test was determined based on the mean of the longest and orthogonal diameters, which was then compared to the equivalent measurements of a histamine solution positive control that was applied at the same time as the test. Grading was as follows:

      0 no discernible wheal

      1. < ½ histamine diameter
      2. ≥ ½ histamine; < histamine diameter
      3. = size of histamine control ± 1 mm
      4. > histamine diameter; < 2x diameter
      5. ≥ 2x histamine control


    Original Secondary Outcome:

    Information By: Albert B. Sabin Vaccine Institute

    Dates:
    Date Received: January 17, 2008
    Date Started: March 2008
    Date Completion:
    Last Updated: January 18, 2012
    Last Verified: January 2012