C. Agabriel

Component‐resolved diagnosis with commercially available D. pteronyssinus Der p 1, Der p 2 and Der p 10: relevant markers for house dust mite allergy

Commercially available house dust mite components may improve routine testing of allergic patients.

Ara h 2 and Ara h 6 sensitization predicts peanut allergy in Mediterranean pediatric patients

Peanut allergy (PA) management was improved by the introduction of molecular allergology, but guidelines for Mediterranean patients are lacking. We aimed at evaluating peanut component‐resolved diagnosis as a diagnostic and prognostic tool in children from Southern France.

Fish allergy: in Cyp c1 we trust

IgE-mediated fish allergy in patients presenting a suggestive clinical history is usually confirmed by skin prick testing (SPT) and/or in vitro fish-specific IgE testing. Basophil activation test (BAT) and fish oral challenge are required at times (1–3). We report herein the case of a girl, clinically diagnosed with fish allergy and whose only positive IgEbinding test was sensitization to rCyp c1. At the age of 3 months, a meal containing codfish resulted in vomiting a few minutes later. Symptoms recurred when the girl’s parents attempted to feed her codfish again at the ages of 9 and 19 months. Three attempts to feed her chicken resulted in similar symptoms. All other foods were tolerated. At the age of 3, codfish SPT (Stallergènes, Antony, France) tested negative; no detectable specific IgE were found for codfish, tuna, chicken, shrimp, egg, or peanut (Bayer Diagnostics; Siemens Medical Solutions Diagnostics, Munich, Germany), and total IgE level was normal. An open oral codfish challenge resulted in severe vomiting. Fish and chicken exclusion was applied thereafter. SPT with either Stallergènes extracts or fresh food and fish and chicken-specific IgE testing (Phadia, Uppsala, Sweden) were repeated at the ages of 4, 6, 8, and 10. These tests were negative. Accidental consumption of chicken (ravioli, chicken nuggets) or fish (codfish, sole) and another oral codfish challenge resulted in vomiting and abdominal pain. At the age of 10, the child underwent codfish and chicken SPT (Stallergènes), codfish BAT (Bühlmann Laboratories, Schönenbuch, Switzerland), and specific IgE testing for codfish and for the recent rCyp c1 (Phadia). SPT and BAT were negative; no codfish-specific IgE was detected. Surprisingly, a small amount of rCyp c1 IgE was present: 0.31 kUA/l, with concentrations above 0.1 kUA/l considered positive. Because low levels of food-specific IgE may be associated with severe clinical reactions, complementary testing of other fish species eaten in our region was performed. This concerned tuna, trout, sole, anchovy, hake, halibut, mackerel, swordfish, chub mackerel (Phadia). All tested negative. Thus, the clinical diagnosis of fish allergy received a late biologic confirmation when rCyp c1 sensitization was evidenced. rCyp c1 is a recombinant carp betaparvalbumin, the major fish allergen, extensively cross-reacting among most species (4). To the best of our knowledge, this is the first case of isolated rCyp c1 sensitization. Such a result may be surprising at first sight, yet it might become a common finding with component-resolved diagnosis development. Indeed, parvalbumin content in the fish ImmunoCAP is lower than in the rCyp c1 ImmunoCAP, yielding a higher sensitivity of the latter. Parvalbumin content and folding may be altered during the process of fish ImmunoCAP production. Finally, parvalbumin accessibility may be hampered by other components in the fish ImmunoCAP. This result is important because first step in vitro allergy testing does not usually include recombinant beta-parvalbumin (rCyp c1, rGad c1)-specific IgE. Rare cases of IgE-mediated fish allergy may thus lack confirmation. There may also be patients with monosensitivity to other fish parvalbumins. Thus, apart from rCyp c 1, other recombinant parvalbumins could be useful in the diagnostic work-up of fish allergy diagnosis. Parvalbumin sensitization may play a central role in the association chicken and fish allergy in this child. Indeed, alpha-parvalbumin has recently been identified as a chicken meat allergen, involved in allergic reactions which do not cross-react with egg or feathers (5). The protein identity of known carp beta-parvalbumin and chicken alphaparvalbumin ranges between 50 and 60% (http://www.expasy.ch). This hypothesis is difficult to check in our patient, who lacks detectable serum-specific IgE to chicken. Nevertheless, parvalbumin homologs among different species may represent a missing biologic link in some fish and meat allergies (6). In conclusion, we report here the case of a child presenting with persistent fish and chicken meat allergy whose only IgE-mediation proof was shown by serum rCyp c1 IgE testing. We therefore suggest that beta-parvalbumin-specific IgE should be tested not only when SPT and/or total fish extract IgE testing have already yielded positive results but also as a first-line in vitro test for fish-induced adverse reactions.

Sequential allergen microarray testing during the follow-up of allergic patients

Results Median age was 6 years (10 months to 17 years) when ISAC was first performed, and 8 years (22 months to 18 years) when the latest ISAC was performed. With respect to the number and intensity of IgE reactivities, ISAC follow-up results entered one of the following categories: progression (16), stability (12), attenuation (8). Two patients displayed complex alterations of their molecular profile over time. In most cases, ISAC followup provided aid for the management of food exclusion or reintroduction regimens. Storage protein reactivity was the most frequent setting, but transition from one molecular profile to another, which were not clinically distinguishable, such as lipid tranfer proteins versus thaumatin-like proteins, was als noted. Complex cross-reactivity patterns or allergy to components which are unavailable for individual testing (sesame Ses i 1, thaumatin-like Act d 2, 7S vicillins other than those from Fabaceae, wheat Tri a 14) gained better insight from repeated ISAC assays. Finally, sequential “allergen landscape views” improved the understanding of the patient’s biological and clinical evolution.

Tomosyn functions as a PKCδ-regulated fusion clamp in mast cell degranulation

PKCδ-dependent phosphorylation of the SNARE inhibitor tomosyn reduces mast cell degranulation. The right partner for secretion Basophils and mast cells are immune cells that initiate allergic reactions and participate in host defense by releasing intracellular granules that contain proteases, lipid mediators, cytokines, and histamine. Degranulation requires the fusion of secretory granules with the plasma membrane, a process that is tightly controlled by SNARE family proteins. Madera-Salcedo et al. noted that, in basophils of allergy patients, serum IgE concentration correlated with the abundance of tomosyn, an inhibitor of SNARE activity. PKCδ-dependent phosphorylation of tomosyn caused it to swap its SNARE protein binding partner. Inhibition or loss of PKC increased mast cell degranulation. The authors suggest that the IgE-correlated expression of tomosyn may function as a feedback loop to limit mast cell degranulation and allergic symptoms in patients. Soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) family proteins mediate membrane fusion critical for vesicular transport and cellular secretion. Mast cells rely on SNARE-mediated membrane fusion for degranulation stimulated by crosslinking of immunoglobulin E (IgE) bound to the Fcε receptor (FcεRI). We investigated the mechanisms downstream of receptor activation that control degranulation. We found that the SNARE binding protein tomosyn-1 (also known as STXBP5) inhibited FcεRI-stimulated degranulation of mast cells. After mast cell activation, tomosyn-1 was phosphorylated on serine and threonine residues, dissociated from the SNARE protein syntaxin 4 (STX4), and associated with STX3. We identified PKCδ as the major kinase required for tomosyn-1 threonine phosphorylation and for regulation of the interaction with STXs. Incubation with high IgE concentrations increased tomosyn-1 abundance in cultured mast cells. Similarly, in basophils from allergic patients with high amounts of serum IgE, the abundance of tomosyn-1 was increased as compared to that in patients with normal IgE concentrations. Our findings identified tomosyn-1 as an inhibitor of mast cell degranulation that required PKCδ to switch its interaction with STX partners during fusion. We suggest that the IgE-mediated increase in tomosyn-1 abundance in allergic patients may represent a counterregulatory mechanism to limit disease development.