α-Gal and other recent findings that have informed our understanding of anaphylaxis

Alpha-Gal Syndrome: A Novel and Increasingly Common Cause of Anaphylaxis

The alpha-gal syndrome is a recently described cause of anaphylaxis to red meat that has been increasing in frequency over time. It is related to Lone Star tick bites in the United States and occurs in many other parts of the world. It is especially common in the southeastern United States. In addition to the usual symptoms of anaphylaxis, gastrointestinal symptoms are prominent. Another unusual feature is the delay of several hours between eating meat and the development of symptoms. Diagnosis can be made by a blood test for the immunoglobulin E antibodies to a specific oligosaccharide. As many as 10% of patients diagnosed with idiopathic anaphylaxis have alpha-gal syndrome in some parts of the United States. The only current treatment is a meat-free diet. Clinician awareness of alpha-gal syndrome is low, and because severe recurrent life-threatening episodes can occur, it is an important condition for emergency clinicians to be aware of.

Snail-induced anaphylaxis in patients with underlying Artemisia vulgaris pollinosis: the role of carbohydrates

PURPOSE

The importance of carbohydrates in anaphylaxis has been described with some foods. The current work intends to obtain clinical and immunological evidence of the importance of the O-glycans for IgE binding activity in anaphylactic reactions due to Helix aspersa (HA) ingestión and Artemisia vulgaris (AV) exposition.

METHODS

The studio focused on two cases of IgE-mediated anaphylaxis induced by snail ingestion in patients with underlying rhino-conjunctivitis and asthma due to AV. We performed on both patients: skin prick tests ( SPTs) with HA and AV and with a battery of aeroallergen, controlled nasal challenge and specific IgE to HA and AV, ImmunoCAP ISAC®, and a differential pattern of IgE recognition with SDS-PAGE Immunoblotting (SDSI) when these allergens have suffered an O-deglycosylation procedure.

RESULTS

The patients showed positive results in SPTs, nasal challenges, and serum-specific IgE against HA and AV. In patient 1, the SDSI detected several IgE-binding proteins in AV with a molecular mass of 22, 24, and 44 kDa, whereas a band of 12 kDa was detected in HA. On the other hand, patient 2's serum revealed an IgE-binding zone between 75 and 20 kDa in the AV and a band of 24 kDa in the HA. When glycans were removed, patient 1's serum only revealed the AV's 22 and 24 kDa bands, whereas patient 2's serum did not detect any IgE-reactive protein in the HA.

CONCLUSIONS

Our data suggest that O-glycosylation can be relevant in patients with anaphylaxis due to snails and allergy to Artemisia vulgaris. This new entity representing cross-reactivity between AV and HA could be named Snail-Artemisia Syndrome.

Alpha-Gal Sensitization in a US Screening Population Is Not Associated With a Decreased Meat Intake or Gastrointestinal Symptoms

INTRODUCTION

Patients with alpha-gal syndrome, a delayed reaction to mammalian meat, can present with isolated gastrointestinal (GI) symptoms. We aimed to estimate the frequency of alpha-gal sensitization in a Southeastern US population and determine the association between sensitization and mammalian product dietary intake or GI symptoms.

METHODS

We performed a cross-sectional study of participants who underwent a screening colonoscopy at our center between 2013 and 2015. We quantified serum alpha-gal immunoglobulin E antibodies in participants who were prospectively enrolled at screening colonoscopy and compared diet intake and lower GI symptoms reported in standardized questionnaires among those with elevated versus no alpha-gal IgE antibodies.

RESULTS

Alpha-gal IgE antibodies were common-31.4% of screening colonoscopy participants (127 of 404) had elevated serum alpha-gal IgE >0.1 kU/L. Alpha-gal-sensitized participants endorsed similar rates of abdominal pain compared with those without alpha-gal antibodies (33% vs 38%, adjusted odds ratio 0.9, 95% confidence interval 0.7-1.3). Mammalian meat consumption did not differ based on alpha-gal sensitization status (average 1.43 servings/d in sensitized subjects vs 1.50 in alpha-gal IgE-negative subjects, P = 0.9). Alpha-gal-sensitized participants with levels ≥10 (n = 21) were overrepresented in the lowest quartiles of mammalian meat consumption, but not among those with GI symptoms in general. Participants with high alpha-gal antibody levels >2 kU/L (n = 45) or ≥10 U/L (n = 21) did not have a reduced mean daily mammalian meat intake compared with seronegative people.

DISCUSSION

Elevated alpha-gal IgE antibodies were common and not associated with a reduced mammalian meat intake, abdominal pain, or diarrhea. Seropositivity did not predict symptomatic alpha-gal sensitization in this general screening population. Other host factors likely contribute to the phenotypic expression of alpha-gal syndrome.

α-Gal specific-IgE prevalence and levels in Ecuador and Kenya: Relation to diet, parasites, and IgG4

BACKGROUND

IgE to α-Gal is a cause of mammalian meat allergy and has been linked to tick bites in North America, Australia, and Eurasia. Reports from the developing world indicate that α-Gal sensitization is prevalent but has been little investigated.

OBJECTIVE

We sought evidence for the cause(s) of α-Gal sensitization and lack of reported meat allergy among children in less developed settings in Ecuador and Kenya.

METHODS

IgE to α-Gal and total IgE were assessed in children from Ecuador (n = 599) and Kenya (n = 254) and compared with children with (n = 42) and without known (n = 63) mammalian meat allergy from the southeastern United States. Information on diet, potential risk factors, and helminth infections was available for children from Ecuador. IgG₄ to α-Gal and antibodies to regionally representative parasites were assessed in a subset of children.

RESULTS

In Ecuador (32%) and Kenya (54%), α-Gal specific IgE was prevalent, but levels were lower than in children with meat allergy from the United States. Sensitization was associated with rural living, antibody markers of Ascaris exposure, and total IgE, but not active infections with Ascaris or Trichuris species. In Ecuador, 87.5% reported consuming beef at least once per week, including 83.9% of those who had α-Gal specific IgE. Levels of α-Gal specific IgG₄ were not high in Ecuador, but were greater than in children from the United States.

CONCLUSIONS

These results suggest that in areas of the developing world with endemic parasitism, α-Gal sensitization is (1) common, (2) associated with Ascaris exposure, and (3) distinguished by a low percentage of specific/total IgE compared with individuals with meat allergy in the United States.

The Role of Food Allergy in Eosinophilic Esophagitis

Food allergy is often understood as an IgE-mediated hypersensitivity, characterized by allergic symptoms which occur “immediately” after the ingestion of a relevant food allergen. Increasingly, however, other food-related immune-mediated disorders are recognized in which symptoms can have a delayed onset and IgE does not play a central role. One of the described examples of the latter is eosinophilic esophagitis (EoE) – a disease defined pathologically by local eosinophilic inflammation in the esophagus in the setting of symptoms of esophageal dysfunction. The evidence that EoE is a food-mediated allergic disease includes i) almost all patients respond to an elemental diet and many respond to a diet in which dairy, wheat, eggs and/or soy are eliminated, ii) the presence of food-specific IgE and Th2 cells are consistent with a loss of tolerance to trigger foods and iii) many EoE patients have concomitant IgE-mediated food allergy and other allergic co-morbidities. This narrative review focuses on the hypothesis that EoE is a form of chronic food allergy. The goal is to describe similarities and differences in EoE and IgE-mediated food allergy, and to consider ways that these two increasingly common forms of food allergy are related to each other.