Repertoire and Properties of Anti-drug Antibodies Involved in Immediate Hypersensitivity in the Operating Room

Acute per-anesthetic hypersensitivity reaction (HSA-PA) is a rapidly occurring systemic reaction following injection of a drug during anesthesia (mortality between 3 and 9%). The substances responsible for these reactions in France are curare in 60% of cases, followed by antibiotics. The main mechanism mentioned is an immediate systemic hypersensitivity immune reaction mediated by IgE antibodies (anaphylaxis).

NeuroMuscular Blocking Agents (NMBA; curare) used in the clinic (e.g., atracurium, suxamethonium, rocuronium, vecuronium) belong to the curare family and block the nicotinic acetylcholine receptor to cause muscle relaxation. They share the presence of quaternary ammonium groups that are required for binding the acetylcholine receptor, and thus for their biological activity. Even though NMBA are relatively safe molecules, two main types of adverse reactions have been reported.

The most striking are immediate and severe anti-drug reactions at NMBA infusion with 1/10,000 patients suffering from severe hypersensitivity reactions, i.e. anaphylaxis. Anaphylaxis is classically considered to rely on IgE antibodies against the culprit compound, and to involve massive histamine liberation by mast cells and basophils, following antigen-induced aggregation of IgE receptor (FcεRI)-bound specific IgE antibodies1. The clinical diagnosis of anaphylaxis to NMBA is based on this IgE paradigm. NMBA quaternary ammonium cations are considered their major allergenic epitopes2, even if patients are rarely hypersensitive to several NMBA, even closely related NMBA like rocuronium and vecuronium that derive from each other, suggesting that antibodies may bind NMBA-specific structures other than quaternary ammoniums. Antibodies may even interact with NMBA as a "whole" epitope due to NMBA very reduced size; NMBA indeed vary from 300-1,000 Da. Intriguingly, 10-20% of patients who experience NMBA-induced anaphylaxis do not present with any biological signs of IgE-dependent immune activation, suggestive of other potential mechanisms. 4 An IgG antibody pathway has recently been described in NMBA-induced human anaphylaxis, leading to Platelet-Activating Factor release, neutrophil and platelet activation, which may aggravate anaphylaxis in combination with the IgE-pathway or underlie anaphylaxis in the absence of specific IgE.

The other most common adverse reaction is not allergic in nature, and is due to prolonged presence of NMBA following surgery, i.e. "residual curarization". This very frequent complication (up to 83% of the patients) leads to adverse postoperative pulmonary events, pharyngeal dysfunction, urgent tracheal reintubation and prolonged stay in post-anesthesia care units that lead to a high economic burden13. The first option for pharmacological neuromuscular blockade reversal, prostigmine (used for atracurium reversal), is restricted to situations where half of the spontaneous reversal is effective. The second one is a synthetic cyclodextrin, sugammadex, that captures rocuronium or vecuronium in vivo within minutes following injection. Instant blockade reversal might be necessary, as in difficult intubation scenarios, explaining that it has been considered economically advantageous to administer sugammadex despite a cost of $100/dose, leading to a $400-$3,000 economy per patient.

Based on strong preliminary results, our study proposes to characterize anti-drugs antibody repertoires in patients with various NMBA or antibiotics-anaphylaxis, describe activation pathways leading to anaphylaxis, develop and validate diagnostic and therapeutic molecules to ameliorate patient screening, NMBA-anaphylaxis and reverse profound neuromuscular block.