Antigenic landscape of the human helminth IgE antibody response

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Antigenic landscape of the human anti-helminth IgE antibody response Scott A. Smith ABSTRACT Despite its perceived central role in helminth immunity, very little is known about the naturally occurring human IgE antibody response, the dominant helminth target proteins or even the size and complexity of the functional antibody repertoire. Most of our knowledge of the IgE antibodies targeting helminth infection and/or allergens has come from studies using polyclonal sera or inferred from murine monoclonal antibodies (mAbs). We hypothesize that the human anti-helminth IgE antibody response is complex but is comprised of B cell clones which target helminth proteins that are homologues of known allergen proteins and are capable of mediating key effector cell functions in vitro. Here we employ a human B cell hybridoma method newly created in my lab, immortalizing growing memory B cells to generate for the first time ever, naturally occurring full-length human IgE mAbs. Patient clinical information is used to select samples that contain cells directed toward important helminth pathogens. In the initial studies described in this proposal, we selected three helminth infected subjects, one having strongyloidiasis and two with filariasis. The frequencies of IgE encoding B cells was found to be approximately three per million mononuclear cells with great variability seen in their reactivity to helminth lysate. These B cell frequencies and our technical efficiencies are sufficient to greatly expand this work and make hundreds of IgE mAbs. Due to funding restraints our initial characterization studies were performed on a small panel of six Wuchereria bancrofti IgE and three Strongyloides stercoralis IgE mAbs. Purified IgE mAbs were also found to have variable reactivity to helminth lysate in both ELISA and Western blot. Specific helminth protein targets were identified by immunoaffinity chromatography/mass spectrometry and fell into known allergen protein families. Crude allergen protein cross-reactivity studies were performed using Phadia diagnostic technologies and found in some cases to be positive, suggesting that allergens can resemble helminth proteins. IgE sequence analysis demonstrates significant degrees of somatic hypermutation. Initial functional studies show that each IgE helminth-specific mAb is capable of dose dependent mast cell mediator release in the presence of lysate - functional potency studies are underway. Ultimately helminth- specific IgE mAb panels will be assembled to reflect a hierarchy of immune dominant helminth protein targets and effector cell functionality. In addition to improving our basic understanding of this poorly studied branch of human immunity and allergic sensitization, the information obtained through studies outlined in this proposal will allow for the design and development of new helminth vaccines.