Fusion of Na-ASP-2 with human immunoglobulin Fcγ abrogates histamine release from basophils sensitized with anti-Na-ASP-2 IgE

Document Type

Journal Article

Publication Date

8-1-2012

Journal

Parasite Immunology

Volume

34

Issue

8-9

DOI

10.1111/j.1365-3024.2012.01371.x

Keywords

Allergy; FcγRIIb; FcεRI; Hookworm; IgE; Na-ASP-2; Necator americanus; Vaccine

Abstract

Na-ASP-2 is a major protein secreted by infective third-stage larvae (L3) of the human hookworm Necator americanus upon host entry. It was chosen as a lead vaccine candidate for its ability to elicit protective immune responses. However, clinical development of this antigen as a recombinant vaccine was halted because it caused allergic reactions among some of human volunteers previously infected with N. americanus. To prevent IgE-mediated allergic reactions induced by Na-ASP-2 but keep its immunogenicity as a vaccine antigen, we designed and tested a genetically engineered fusion protein, Fcγ/Na-ASP-2, composed of full-length Na-ASP-2 and truncated human IgG Fcγ1 that targets the negative signalling receptor FcγRIIb expressed on pro-allergic cells. The chimeric recombinant Fcγ/Na-ASP-2 protein was expressed in Pichia pastoris and shared the similar antigenicity as native Na-ASP-2. Compared to Na-ASP-2, the chimeric fusion protein efficiently reduced the release of histamine in human basophils sensitized with anti-Na-ASP-2 IgE obtained from individuals living in a hookworm-endemic area. In dogs infected with canine hookworm, Fcγ/Na-ASP-2 resulted in significantly reduced immediate-type skin reactivity when injected intradermally compared with Na-ASP-2. Hamsters vaccinated with Fcγ/Na-ASP-2 formulated with Alhydrogel® produced specific IgG that recognized Na-ASP-2 and elicited similar protection level against N. americanus L3 challenge as native Na-ASP-2. © 2012 Blackwell Publishing Ltd.

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