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

Parasite Immunol. Aug-Sep 2012;34(8-9):404-11. doi: 10.1111/j.1365-3024.2012.01371.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Helminth / genetics
  • Antigens, Helminth / immunology
  • Basophils / immunology*
  • Cricetinae
  • Dogs
  • Gene Expression
  • Histamine Release*
  • Humans
  • Hypersensitivity / prevention & control
  • Immunization*
  • Immunoglobulin E / immunology*
  • Immunoglobulin Fc Fragments / genetics
  • Immunoglobulin Fc Fragments / immunology*
  • Immunoglobulins
  • Necator americanus / immunology*
  • Pichia / genetics
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / immunology
  • Skin / pathology
  • Vaccination / adverse effects
  • Vaccination / methods*

Substances

  • Antigens, Helminth
  • Immunoglobulin Fc Fragments
  • Immunoglobulins
  • Recombinant Fusion Proteins
  • Immunoglobulin E