Journal of investigational allergology & clinical immunology •
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.
Fischer J, Riel S, Fehrenbacher B, Frank A, Schaller M, et al.
Ticks and tick-borne diseases •
Alpha-gal syndrome is a complex allergic disease in humans that is caused by specific IgE (sIgE) against the carbohydrate galactose-α-1,3-galactose (alpha-gal). Tick saliva contains alpha-gal, and tick bites are considered a major cause of the induction of alpha-gal-sIgE. The origin of alpha-gal in tick saliva remains unclarified. The presence of alpha-gal in tick tissue was visualized in this study to provide an overview of the spatial distribution of alpha-gal and to further elucidate the origin of alpha-gal in tick saliva. Fed and unfed Ixodes ricinus females were examined by histology, immunohistochemistry, immunofluorescence, transmission electron microscopy and immunoelectron microscopy using the alpha-gal-specific monoclonal antibody M86 and Marasmius oreades agglutinin (MOA) lectin. Alpha-gal epitopes were detected in the midgut, hemolymph and salivary glands, and the immunofluorescence analysis revealed signs of the endocytosis of alpha-gal-containing constituents during the process of hematophagy. Alpha-gal epitopes in endosomes of the digestive gut cells of the ticks were observed via immunoelectron microscopy. Alpha-gal epitopes were detected in dried droplets of hemolymph from unfed ticks. Intense staining of alpha-gal epitopes was found in type II granular acini of the salivary glands of fed and unfed ticks. Our data suggest that alpha-gal is not ubiquitously expressed in tick tissue but is present in both fed and unfed ticks. The findings also indicate that both the metabolic incorporation of constituents from a mammalian blood meal and endogenous production contribute to the presence of alpha-gal epitopes in ticks.
