Evaluation by double‐blind placebo‐controlled oral challenge of the clinical relevance of IgE antibodies against plant glycans

Abstract

The clinical relevance of immunoglobulin E (IgE) to plant glycans is a longstanding debate. We sought to evaluate their clinical reactivity using the human glycoprotein lactoferrin expressed in rice. Allergic patients with IgE antibodies against plant glycans were analyzed for the presence of IgE against rice-produced lactoferrin. The potency of IgE to induce mediator release was assessed by basophil histamine release and skin prick tests (SPTs). Clinical relevance was evaluated by double-blind placebo-controlled oral challenge (DBPCOC). Twenty-four of 29 sera (82.7%) with IgE antibodies against plant glycans demonstrated IgE binding to transgenic lactoferrin. In three of five cases transgenic lactoferrin induced histamine release. Compared to a control major grass pollen allergen lactoferrin concentrations needed for biological activity of IgE were 5-6 orders of magnitude higher. Skin prick test and DBPCOC were negative in five patients with potential clinical reactivity that volunteered to undergo these in vivo challenges. Poor or no biological activity and lack of clinical relevance of IgE-binding plant glycans (five out of five) was demonstrated using human lactoferrin expressed in rice as a model.