Ollert M

Longitudinal Follow-up Reveals Peripheral Immunological Changes Upon Tick Bite in α-Gal-Sensitized Individuals.

α-Gal syndrome is characterized by specific IgE (sIgE) antibodies to the carbohydrate galactose-α-1,3-galactose (α-Gal) and delayed onset of allergic symptoms after ingestion of mammalian meat. While tick bites are assumed to mediate sensitization, the immune response to tick bites has not yet been investigated. Objective: To investigate the peripheral immune response to tick bites in humans over time. In a longitudinal cohort study, immunological reactions associated with tick bites (Ixodes species) were analyzed within 1 day (V1), 2 weeks (V2), 1 month (V3), and 3 months (V4) after the occurrence of a bite. sIgE, sIgG, and sIgG subclass levels, as well as 10 cytokines, were quantified. Deep immune phenotyping was performed using mass cytometry. A total of 4 controls and 10 patients were bitten by a tick and followed up over 3 months. None of the controls developed sIgE to α-Gal, and sIgE increased in all patients from V1 until V2/V3, as did IL-8 levels. We noted a significant increase in CD19+ B cells and B-cell subpopulations, as well as a decrease in γδ CD56+ T cells in patients between V0 and V1. At V1, frequencies of plasmacytoid dendritic cells (pDCs) and γδ CD56+ T cells were lower in patients than in controls. Our study provides evidence of significant changes in several immune cell populations in α-Gal-sensitized patients, along with increased levels of IL-8 and sIgE. This is the first exploratory study to investigate longitudinal peripheral immune profiles in patients and controls bitten by ticks.

Recurrent tick bites induce high IgG1 antibody responses to α-Gal in sensitized and non-sensitized forestry employees in Luxembourg.

The α-Gal syndrome (AGS) is characterized by the presence of specific IgE-antibodies to the carbohydrate galactose-α-1,3-galactose (α-Gal). Sensitization to α-Gal has been associated with tick bites and individuals exposed to ticks have an elevated risk of sensitization. The aim of this study was to analyze IgG and IgE antibody responses to α-Gal in a high-risk cohort of forestry employees (FE) in Luxembourg. Questionnaires and serum samples of FE from Luxembourg (n = 219) were retrospectively analyzed. α-Gal specific IgE was quantified by ImmunoCAP, α-Gal specific IgG and subclasses IgG were determined by ELISA. Additionally, sera from population-based controls (n = 150) and two groups of food-allergic patients, patients with AGS (n = 45) and fish-allergic patients (n = 22) were assessed for IgG antibody responses to α-Gal and cod extract. Twenty-one percent of FE was sensitized to α-Gal (sIgE ≥ 0.1 kU/L). Both sensitized and non-sensitized FE exhibited high levels of α-Gal specific IgG, IgG1 and IgG3 compared with controls, indicating a stimulation of IgG responses by recurrent tick bites, independent of the sensitization status. AGS patients had the highest levels of IgG1 and IgG2 antibodies, whereas the profile of fish-allergic patients was similar to the profile of the controls for which anti-α-Gal responses were dominated by IgG2 antibodies. α-Gal sIgG4 levels were either very low or undetectable in all groups. Our study provides evidence for a continuous stimulation of α-Gal related immune responses by repeated tick bites, translating into highly elevated levels of IgG1 antibodies directed against α-Gal.

Delayed reaction in alpha-gal allergy is reflected in serum levels after ingestion of pork kidney, and absorption is dependent on food processing.

α-Gal present on both glycolipids and glycoproteins contributes to immune response in meat-allergic patients.

The α-Gal syndrome is associated with the presence of IgE directed to the carbohydrate galactose-α-1,3-galactose (α-Gal) and is characterized by a delayed allergic reaction occurring 2 to 6 hours after ingestion of mammalian meat. On the basis of their slow digestion and processing kinetics, α-Gal-carrying glycolipids have been proposed as the main trigger of the delayed reaction. We analyzed and compared the in vitro allergenicity of α-Gal-carrying glycoproteins and glycolipids from natural food sources. Proteins and lipids were extracted from pork kidney (PK), beef, and chicken. Glycolipids were purified from rabbit erythrocytes. The presence of α-Gal and IgE binding of α-Gal-allergic patient sera (n = 39) was assessed by thin-layer chromatography as well as by direct and inhibition enzyme-linked immunosorbent assay. The in vitro allergenicity of glycoproteins and glycolipids from different meat extracts was determined by basophil activation test. Glycoprotein stability was evaluated by simulated gastric and intestinal digestion assays. α-Gal was detected on glycolipids of PK and beef. Patient IgE antibodies recognized α-Gal bound to glycoproteins and glycolipids, although binding to glycoproteins was more potent. Rabbit glycolipids were able to strongly activate patient basophils, whereas lipid extracts from PK and beef were also found to trigger basophil activation, but at a lower capacity compared to the respective protein extracts. Simulated gastric digestion assays of PK showed a high stability of α-Gal-carrying proteins in PK. Both α-Gal-carrying glycoproteins and glycolipids are able to strongly activate patient basophils. In PK and beef, α-Gal epitopes seem to be less abundant on glycolipids than on glycoproteins, suggesting a major role of glycoproteins in delayed anaphylaxis upon consumption of these food sources.