Fischer J, Huynh HN, Hebsaker J, Forchhammer S, Yazdi AS
International archives of allergy and immunology •
Alpha-gal syndrome is a complex allergy with high clinical relevance regarding mammalian-derived food and drugs and is characterized by the presence of IgE antibodies directed at the carbohydrate galactose-α-1,3-galactose. As not all alpha-gal sIgE-positive individuals pre-sent clinical symptoms upon consumption of mammalian meat, the diagnostic value of alpha-gal sIgE has yet to be clarified. To investigate the prevalence of alpha-gal-sIgE positivity among allergy patients, examine the impact of tick bites as associated risk factors and determine the diagnostic value of alpha-gal-sIgE positivity. A retrospective cross-sectional study evaluating patients in the Allergy Unit was performed. Alpha-gal-sIgE levels were assessed by ImmunoCAP assay. Exposure to tick bites was assessed by a questionnaire. A receiver operating characteristics (ROC) curve analysis was performed to determine the diagnostic value of alpha-gal sIgE for the diagnosis of alpha-gal syndrome. In the study population (n = 1369), the overall prevalence of alpha-gal-sIgE-positive (≥0.10 kUA/L) individuals was 19.9%, and the highest prevalence (30.2%) was found in patients with insect venom allergies. A reported tick bite within the 12 months prior to blood sampling significantly increased the risk of alpha-gal-sIgE positivity (OR 2.084). The ROC curve analysis indicated alpha-gal sIgE ≥0.54 kUA/L as the optimal cutoff point for assessing the diagnostic value of alpha-gal syndrome in allergy patients. In allergy care settings, alpha-gal-sIgE positivity is a common finding. Alpha-gal sIgE is a sensitive marker in the diagnosis of alpha-gal syndrome but has limited predictive value for the characteristics or severity of this allergy.
Jappe U, Minge S, Kreft B, Ludwig A, Przybilla B, et al.
Allergy •
Glycoproteins and glycolipids of some mammalian species contain the disaccharide galactosyl-α-(1,3)-galactose (α-Gal). It is known that α-Gal is immunogenic in humans and causes glycan-specific IgG and also IgE responses with clinical relevance. α-Gal is part of the IgE-reactive monoclonal therapeutic antibody cetuximab (CTX) and is associated with delayed anaphylaxis to red meat. In this study, different α-Gal-containing analytes are examined in singleplex and multiplex assays to resolve individual sensitization patterns with IgE against α-Gal. Three serum groups, α-Gal-associated meat allergy (MA) patients, idiopathic anaphylaxis (IA) patients with suspected MA, and non-meat-allergic healthy control individuals (HC), were analyzed via singleplex allergy diagnostics and a newly established immunoblot diagnostic system. The new dot blot detection system resolved individual IgE sensitization profiles for α-Gal-containing analytes CTX, bovine thyroglobulin (Bos d TG), and human serum albumin (HSA)-conjugated α-Gal. Singleplex allergy diagnostics using the α-Gal analytes CTX and Bos d TG confirms the history of MA patients in 91% and 88% of the cases, respectively. A novel dot blot-based assay system for the detection of IgE against α-Gal reveals individual IgE sensitization profiles for α-Gal-containing analytes. An α-Gal-associated IgE cross-reactivity profile (IgE against CTX, Bos d TG, and HSA-α-Gal) was identified, which is associated with MA. Detection of individual sensitization patterns with different α-Gal-containing analytes provides the basis for an individual allergy diagnosis for α-Gal-sensitized patients. Higher amounts of α-Gal in pork and beef innards compared to muscle meat as indicated by a higher staining intensity are a plausible explanation for the difference in allergic symptom severity.
