Fusion of Na-ASP-2 with human immunoglobulin Fcγ abrogates histamine release from basophils sensitized with anti-Na-ASP-2 IgE.
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.
Section of Pediatric Tropical Medicine, Departments of Pediatrics and Molecular Virology and Microbiology, and National School of Tropical Medicine, Baylor College of Medicine, Houston, TX 77030, USA. bzhan@bcm.edu
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Zhan
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Santiago
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Gillespie
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Xue
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Bethony
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Jiang
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Diemert
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Jones
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Bottazzi
D000818:Animals; D000947:Antigens, Helminth / Q000235:genetics / Q000276:immunology; D001491:Basophils / Q000276:immunology*; D006224:Cricetinae; D004285:Dogs; D015870:Gene Expression; D006636:Histamine Release; D006801:Humans; D006967:Hypersensitivity / Q000517:prevention & control; D007114:Immunization; D007073:Immunoglobulin E / Q000276:immunology*; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000276:immunology*; D007136:Immunoglobulins; D017221:Necator americanus / Q000276:immunology*; D010843:Pichia / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D012867:Skin / Q000473:pathology; D014611:Vaccination / Q000009:adverse effects / Q000379:methods*
D000947:Antigens, Helminth; D007141:Immunoglobulin Fc Fragments; D007136:Immunoglobulins; D011993:Recombinant Fusion Proteins; D007073:Immunoglobulin E