Prevalence and Impact of Type I Sensitization to Alpha-Gal in Patients Consulting an Allergy Unit

Connecting Diagnostics and Clinical Relevance of the α-Gal Syndrome-Individual Sensitization Patterns of Patients with Suspected α-Gal-Associated Allergy

BACKGROUND/OBJECTIVES

Sensitization to the carbohydrate antigen α-Gal is associated with allergic reactions against different types of food that contain α-Gal (e.g., mammalian meat). This form of allergy is termed α-Gal syndrome (AGS), and the diagnosis is challenging due to delayed symptom onset and cross-reactivity with multiple mammalian products. It is estimated that AGS is underdiagnosed, pointing to an unmet need for patient care.

METHODS

Sera from patients with suspected AGS based on clinical history were analyzed by ImmunoCAP and the IgE cross-reactivity immune profiling (ICRIP) system specifically developed by us. IgE from patient sera against different forms of α-Gal was analyzed using α-Gal-containing analytes and negative controls.

RESULTS

Sera from 33 patients with suspected AGS were analyzed. Sera from 22 patients yielded a clearly positive signal (>0.35 kU/L) for IgE against α-Gal in ImmunoCAP. For 7 of the remaining 11 patients with negative or ambiguous (IgE level between 0.1 and 0.35 kU/L) results in ImmunoCAP, ICRIP analyses supported the suspected association of the allergy symptoms with IgE against α-Gal components. This component-resolved analysis helps the allergist to provide an individual diagnosis for each patient.

CONCLUSIONS

The diagnosis of AGS is challenging. An interplay between clinical history and lab analysis via ImmunoCAP and the specifically developed ICRIP system helps patients and allergists in establishing the correct diagnosis, thereby preventing accidental exposure and recurrent AGS episodes.

French Guiana and AGS: a path to uncovering hidden clues

INTRODUCTION

This article is a narrative review exploring how research in French Guiana could unlock the mysteries surrounding Alpha-Gal Syndrome (AGS), a recently identified IgE-mediated allergy with delayed reactions to exposure to non-Catarrhine mammalian-derived products. Although fewer than 10 cases have been reported across Latin America, two case series involving 11 and 18 patients with AGS have been documented in French Guiana.

AREAS COVERED

This article discusses risk factors such as ethnicity, prior pathogen-induced immunization to α-Gal, vectors responsible for AGS, their environment and ecosystems, observed phenotypes, and therapeutic implications for sensitized individuals. Literature research was based on PubMed between 12/2023 and 08/2024, using: α-Gal/Alpha-1,3-Galactose/galactose-α 1,3-galactose/Red meat allergy/Mammalian meat allergy/Alpha gal syndrome/Antivipmyn. Grey literature from French Guiana were obtained from Prof. Loïc Epelboin.

EXPERT OPINION

Advancing AGS research in French Guiana could yield valuable epidemiological insights, as existing data predominantly stem from European, North American, Australian, and Japanese contexts - regions with comparatively lower diversity in tick species, their mammalian hosts, associated pathogens, and parasitic infestations. Additionally, French Guiana presents unique therapeutic scenarios, such as Viperidae envenomation and transfusions under inventory constraints, that merit further investigation.

Increasing prevalence of galactose-α-1,3-galactose sensitization in the Danish general adult population

BACKGROUND

Alpha-gal syndrome is a novel food allergy to the oligosaccharide galactose-α-1,3-galactose (alpha-gal) present in mammalian meat. Tick bites are considered an important route of sensitization to alpha-gal. Data on alpha-gal sensitization in the general population is scant. We utilized a unique data source of repeated population-based health examination studies to assess prevalence, time trends, risk factors, and characteristics of alpha-gal sensitization.

METHODS

Alpha-gal sensitization was assessed in >11.000 adults from four health examination studies of randomly invited residents in the Copenhagen region conducted in 1990-1991, 2011-2012, 2012-2015, and 2016-2017. Alpha-gal sensitization was defined as serum specific IgE (sIgE) to alpha-gal ≥0.1 kUA/L; ≥0.35 kUA/L; ≥0.7 kUA/L; ≥3.5 kUA/L. The population was characterized according to genetically determined ABO blood group, aeroallergen sensitization, and pets at home.

RESULTS

The prevalence of sIgE to alpha-gal ≥0.1 kUA/L was 1.3% in 1990-1991, 3.7% in 2012-2015 and 3.2% in 2016-2017. Of those sensitized to alpha-gal >97% reported to consume red meat at least once a week, even for sIgE to alpha-gal ≥3.5 kUA/L. Male sex, older age, aeroallergen sensitization, cat at home, and blood group A were associated with increased odds of alpha-gal sensitization. The known protective effect of blood group B was confirmed.

CONCLUSION

In this general adult population, the prevalence of alpha-gal sensitization had doubled from 1990-1991 to 2016-2017. This could potentially be due to increased tick exposure and an increased atopic predisposition.

Mammalian Meat Allergy and IgE to Alpha-Gal in Central Virginia: Findings From a COVID-19 Vaccine and Patient Cohort

BACKGROUND

IgE to galactose-alpha-1,3-galactose (alpha-gal) is linked to tick bites and an important cause of anaphylaxis and urticarial reactions to mammalian meat. The alpha-gal syndrome (AGS) is recognized as being common in the southeastern United States. However, prevalence studies are lacking and open questions remain about risk factors and clinical presentation of alpha-gal sensitization.

OBJECTIVE

Here we characterized the prevalence as well as the presentation and risk factors of AGS and alpha-gal IgE sensitization in adults in central Virginia recruited without regard to the history of allergic disease.

METHODS

Adults in central Virginia, primarily University of Virginia Health employees, were recruited as part of a COVID-19 vaccine study. Subjects provided at least one blood sample and answered questionnaires about medical and dietary history. We used ImmunoCAP for IgE assays and assessed the ABO blood group by reverse typing using stored serum. We also investigated biobanked serum from COVID-19 patients.

RESULTS

Median age of the 267 enrollees was 42 years, 76% were female, and 43 (16%) were sensitized to alpha-gal (cutoff of 0.1 IU/mL), of which mammalian meat allergy was reported by seven (2.6%). Sensitized subjects (1) were older, (2) had higher total IgE levels but a similar frequency of IgE to common respiratory allergens, and (3) were more likely to report tick bites than were nonsensitized subjects. Among those who were sensitized, alpha-gal IgE levels were higher among meat-allergic than nonallergic subjects (geometric mean, 9.0 vs 0.5 IU/mL; P < .001). Mammalian meat and dairy consumption was common in individuals with low-level sensitization.

CONCLUSION

In central Virginia, AGS is a dominant cause of adult food allergy with a prevalence approaching or exceeding 2%.

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

BACKGROUND

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.

METHODS

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 IgG1-4 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.

RESULTS

Twenty-one percent of FE was sensitized to α-Gal (sIgE ≥ 0.1 kUA/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.

CONCLUSION

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.

Alpha-Gal Syndrome: An Underrated Serious Disease and a Potential Future Challenge

Over the past decades, red meat allergy, also known as mammalian meat allergy, which manifests differently from classic food allergies, has been reported in different countries and regions, including China. The allergen of this disease is not a protein but an oligosaccharide: galactose-α-1,3-galactose, i.e., alpha-gal or α-gal. Therefore, this clinical syndrome is also called α-gal syndrome (AGS). It clinically manifests as delayed anaphylaxis, i.e., patients generally develop allergic symptoms 2-6 h after ingesting red meat. This clinical manifestation is believed to be related to sensitization to α-gal after tick bites. Sensitized individuals may also develop anaphylaxis after ingesting food and medicine or being exposed to medical equipment containing α-gal, such as cetuximab and gelatin. Here, the literature on AGS is reviewed for a better understanding of its pathogenesis, clinical diagnosis, and treatment.

Tick bites, IgE to galactose-alpha-1,3-galactose and urticarial or anaphylactic reactions to mammalian meat: The alpha-gal syndrome

The recent recognition of a syndrome of tick-acquired mammalian meat allergy has transformed the previously held view that mammalian meat is an uncommon allergen. The syndrome, mediated by IgE antibodies against the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), can also involve reactions to visceral organs, dairy, gelatin and other products, including medications sourced from non-primate mammals. Thus, fittingly, this allergic disorder is now called the alpha-gal syndrome (AGS). The syndrome is strikingly regional, reflecting the important role of tick bites in sensitization, and is more common in demographic groups at risk of tick exposure. Reactions in AGS are delayed, often by 2-6 h after ingestion of mammalian meat. In addition to classic allergic symptomatology such as urticaria and anaphylaxis, AGS is increasingly recognized as a cause of isolated gastrointestinal morbidity and alpha-gal sensitization has also been linked with cardiovascular disease. The unusual link with tick bites may be explained by the fact that allergic cells and mediators are mobilized to the site of tick bites and play a role in resistance against ticks and tick-borne infections. IgE directed to alpha-gal is likely an incidental consequence of what is otherwise an adaptive immune strategy for host defense against endo- and ectoparasites, including ticks.

Clinical Use of the ImmunoCAP Inhibition Test in the Diagnosis of Meat Allergy Caused by a Tick Bite in an Adult Male with No Previous Atopic History

(1) Background: alpha-gal syndrome (AGS) is a serious, potentially life-threatening allergic reaction. This is a type of food allergy to red meat and other mammalian products (e.g., gelatin). In Poland, this problem seems to be rare or, more likely, very underdiagnosed. The diagnosis of AGS is difficult. It seems that the knowledge about this syndrome is insufficient. There are no effective diagnostic tools able to clearly diagnose this cross-reactive allergy. This paper presents the clinical application of a non-standard method in the diagnosis of a cross-reactive allergy using the example of AGS. (2) Methods: standard tests for in vitro allergy diagnostics and the non-standard ImmunoCAP inhibition test(IT) were carried out for serum collected from a patient with a red meat allergy. (3) Results: the serum concentration of anti-α-Gal IgE was very high (302 kUA/L), and IgE antibodies toanti-mammalian-meat allergens were found. The level of IgE antibodies to mammalian meat allergens decreased after blocking on α-GAL-CAP. The concentration of anti-α-Gal IgE decreased after blocking on CAPs coated with various mammalian meat allergens. Blocking with allergens of poultry meat did not affect the concentration of anti-α-Gal IgE. (4) Conclusions: the ImmunoCAP ITseems to be a useful tool in the diagnosis of cross-reactive allergies. Based on their clinical history and test results, the patient was diagnosed with AGS caused by a primary sensitization to α-Gal after a tick bite. This is the second case of AGS described in Poland and the first in Pomerania.

Clinical and laboratory features of patients diagnosed with alpha-gal syndrome-2010-2019

BACKGROUND

Alpha-gal syndrome (AGS) is an IgE-mediated allergy to galactose-alpha-1,3-galactose. Clinical presentation ranges from hives to anaphylaxis; episodes typically occur 2-6 h after exposure to alpha-gal-containing products. In the United States, lone star tick bites are associated with the development of AGS. To characterize features of AGS, we evaluated a cohort of patients presenting for care at the University of North Carolina, focusing on symptoms, severity, and identifying features unique to specific alpha-gal-containing product exposures.

METHODS

We performed a chart review and descriptive analysis of 100 randomly selected patients with AGS during 2010-2019.

RESULTS

Median age at onset was 53 years, 56% were female, 95% reported White race, 86% reported a history of tick bite, and 75% met the criteria for anaphylaxis based on the involvement of ≥2 organ systems. Those reporting dairy reactions were significantly less likely to report isolated mucocutaneous symptoms (3% vs. 24%; ratio [95% CI]: 0.1 [0.1, 0.3]) than those who tolerated dairy, and were more likely to report gastrointestinal symptoms (79% vs. 59%; ratio [95% CI]: 1.3 [0.7, 2.6]), although this difference was not statistically significant. Dairy-tolerant patients demonstrated higher alpha-gal sIgE titers (as a percentage of total IgE) than dairy-reactive patients (GM 4.1 [95% CI: 2.7, 6.1] vs. GM 2.5 [95% CI: 1.3, 4.8], respectively; ratio -1.6 [95% CI: -1.0, 3.9]).

CONCLUSION

While tick exposure is common in the southern United States, nearly all AGS patients reported a tick bite. Gastrointestinal symptoms were prominent among those reporting reactions to dairy. Anaphylaxis was common, underscoring the severity and need to raise awareness of AGS among patients and providers.

Alpha-gal syndrome initially misdiagnosed as chronic spontaneous urticaria in a pediatric patient: a case report and review of the literature

INTRODUCTION

Delayed allergy to red meat, also termed alpha-gal syndrome, is increasingly reported in adults and African communities, while pediatric cases remain rare.

CASE PRESENTATION

Here, we report on a 7-year-old Caucasian boy presenting with recurrent wheals since the age of 5 years old. Episodes with hives occurred around every 3 weeks, mainly in the evening. One of these episodes was also associated with angioedema. No clear trigger was identified. At the first visit, after excluding an infection and autoimmune thyroiditis, chronic spontaneous urticaria was suspected and symptomatic treatment with antihistamines was prescribed. Six months later, the boy presented at the emergency room with generalized urticaria, dyspnoea, and emesis. Symptoms resolved after administration of epinephrine and antihistamines. A detailed medical history after this event revealed that he had eaten three sausages as well as jelly beans containing gelatine several hours prior to this episode. More precisely, after eating the sausages and jelly beans during the day, he had shown some hives before going to bed, and later developed the other symptoms in the middle of the night, suggesting alpha-gal syndrome. In his history, several tick bites are reported. Immunoglobulin E levels for alpha-gal were clearly elevated, confirming the diagnosis of a delayed-appearing immunoglobulin E-mediated allergic reaction to alpha-gal. Emergency medication was prescribed and avoidance of red meat and gelatine-containing foods was recommended. Under this exclusion diet, the boy remained asymptomatic, with the exception of two accidents in the follow up of 3 years, one developing during a barbecue and the second after exceptionally eating marshmallows.

CONCLUSION

A detailed clinical history led to the diagnosis of alpha-gal syndrome. Although alpha-gal syndrome is typically seen in adults, our case illustrates that children can also present with this potentially life-threatening allergy. Since alpha-gal syndrome is rare in Europe, the disease is not well known and often overlooked for several years, especially in children.

The Meat of the Matter: Understanding and Managing Alpha-Gal Syndrome

Alpha-gal syndrome is an unconventional food allergy, characterized by IgE-mediated hypersensitivity responses to the glycan galactose-alpha-1,3-galactose (alpha-gal) and not to a food-protein. In this review, we discuss how alpha-gal syndrome reframes our current conception of the mechanisms of pathogenesis of food allergy. The development of alpha-gal IgE is associated with tick bites though the possibility of other parasites promoting sensitization to alpha-gal remains. We review the immune cell populations involved in the sensitization and effector phases of alpha-gal syndrome and describe the current understanding of why allergic responses to ingested alpha-gal can be delayed by several hours. We review the foundation of management in alpha-gal syndrome, namely avoidance, but also discuss the use of antihistamines, mast cell stabilizers, and the emerging role of complementary and alternative therapies, biological products, and oral immunotherapy in the management of this condition. Alpha-gal syndrome influences the safety and tolerability of medications and medical devices containing or derived from mammalian products and impacts quality of life well beyond food choices.

Initiating Psychotropic Treatment in a Patient With Alpha-Gal Syndrome

Alpha-gal syndrome, which is typically acquired by a tick bite, is an IgE-mediated immune response to galactose-alpha-1,3-galactose (alpha-gal), an oligosaccharide in most mammalian tissue. This report describes a 29-year-old Caucasian female with comorbid alpha-gal syndrome who presented to the inpatient psychiatric unit after an intentional overdose. Because of the patient’s alpha-gal syndrome, the treatment team worked with the hospital pharmacy to evaluate treatment options that did not contain mammalian products. After carefully reviewing the ingredients of suitable medications on formulary, the patient was started on a generic sertraline formulation that was free of mammalian derivatives. At the time of discharge, the patient reported significant symptom improvement and was free of symptoms suggesting an alpha-gal allergic reaction. This case illustrates the challenges of starting psychiatric medications in a patient with comorbid alpha-gal syndrome.

Sensitisation and allergic reactions to alpha-1,3-galactose in Podlasie, Poland, an area endemic for tick-borne infections

PURPOSE

Ticks transmit several pathogens and seem implicated in the production of specific IgE antibodies to alpha-1,3-galactose (α-gal sIgE). They cause delayed and immediate allergy to mammalian meat and medication including antivenoms, vaccines and monoclonal antibodies.

METHODS

We assessed the prevalence of α-gal sIgE in forest workers and healthy controls in the Podlasie voivodeship, north-eastern Poland; the relationship between α-gal sIgE and allergy to α-gal-containing products; the correlation between α-gal sIgE and anti-Borrelia burgdorferi and anti-tick-borne encephalitis virus (TBEV) antibodies; the relationship between α-gal sIgE and markers of infection with lesser-known pathogens transmitted by ticks such as Anaplasma phagocytophilum.

RESULTS

Production of α-gal sIgE was closely related to tick bites. The odds ratio for detectable α-gal sIgE was 9.31 times higher among people with a history of tick bites (OR 9.3; p < .05). There was no correlation with the history of TBE, Lyme disease or human granulocytic anaplasmosis. However, serum α-gal sIgE correlated with anti-TBEV IgM antibodies in CSF. There was a strong correlation between α-gal sIgE and total IgE and sIgE to pork and beef.

CONCLUSIONS

Our data support the link between I.ricinus ticks and the production of α-gal sIgE and confirm that the pathogens carried by ticks we examined for do not seem implicated in this immune response.

Food allergy and hypersensitivity reactions in children and adults-A review

Adverse reactions after food intake are commonly reported and a cause of concern and anxiety that can lead to a very strict diet. The severity of the reaction can vary depending on the type of food and mechanism, and it is not always easy to disentangle different hypersensitivity diagnoses, which sometimes can exist simultaneously. After a carefully taken medical history, hypersensitivity to food can often be ruled out or suspected. The most common type of allergic reaction is immunoglobulin E (IgE)-mediated food allergy (prevalence 5-10%). Symptoms vary from mild itching, stomach pain, and rash to severe anaphylaxis. The definition of IgE-mediated food allergy is allergic symptoms combined with specific IgE-antibodies, and therefore only IgE-antibodies to suspected allergens should be analyzed. Nowadays, methods of molecular allergology can help with the diagnostic process. The most common allergens are milk and egg in infants, peanut and tree nuts in children, and fish and shellfish in adults. In young children, milk/egg allergy has a good chance to remit, making it important to follow up and reintroduce the food when possible. Other diseases triggered by food are non-IgE-mediated food allergy, for example, eosinophilic esophagitis, celiac disease, food protein-induced enterocolitis syndrome, and hypersensitivity to milk and biogenic amines. Some of the food hypersensitivities dominate in childhood, others are more common in adults. Interesting studies are ongoing regarding the possibilities of treating food hypersensitivity, such as through oral immunotherapy. The purpose of this review was to provide an overview of the most common types of food hypersensitivity reactions.

[Alpha-gal syndrome : Overview of clinical presentation and pathophysiology]

Das Alpha-Gal-Syndrom gehört zu den spannendsten Entdeckungen in der Allergologie der letzten 15 Jahre und wird ausgelöst durch spezifisches Immunglobulin E (sIgE) gegen den für Menschen immunogenen Zucker Galaktose-α‑1,3‑Galaktose (Alpha-Gal). Säugetierfleisch, Milch und daraus hergestellte Nahrungsmittel enthalten Alpha-Gal und können zu Anaphylaxien führen. Auch Arzneimittel und Medizinprodukte aus Säugetiergewebe können allergen sein. Zeckenstiche gelten als Hauptquelle einer Induktion von Alpha-Gal-sIgE. Ziel dieses Beitrags ist es, einen Überblick über den Stand des Wissens zum klinischen Bild und zu pathophysiologischen Konzepten zu geben.

The Quantification of IgG Specific to α-Gal Could Be Used as a Risk Marker for Suffering Mammalian Meat Allergy

The alpha-Gal Syndrome is a delayed meat allergy characterized by the presence of sIgE against α-Gal epitope. It is known that the α-Gal present in tick saliva induces the sensitization to this epitope ending in the production of sIgG and sIgE to α-Gal. It could be considered that the more times a person is bitten by tick species, the higher the probability of making the switch from sIgG to sIgE to α-Gal and developing allergy, but it is no clear when the switch occurs. To determine the likelihood that a subject bitten by ticks but without AGS be at risk of developing this allergy, we quantified the levels of sIgG to α-Gal by an automated system (ImmunoCap). To stablish a cut-off value for sIgG to α-Gal, a receiving operating curve (ROC) was constructed. The statistical analysis demonstrated that the risk of suffering AGS in individuals bitten by ticks was 35% when the sIgG to α-Gal was greater than or equal to 40 µg/mL. Our data indicate that the sIgG values against α-Gal could be used as a prognostic marker for developing mammalian meat allergy.

Successful Treatment for Alpha Gal Mammal Product Allergy Using Auricular Acupuncture: A Case Series

Introduction: Alpha gal syndrome (AGS) is an acquired allergy to mammalian products correlates with a tick bite(s) that appears to cause immune sensitization to an oligosaccharide in meat. Most publications on AGS describe no management other than avoidance of the offending agent(s). The objective of this study is to describe 2 populations of subjects who underwent Soliman Auricular Allergy Treatment (SAAT) for significant AGS meat and/or dairy allergy. Methods: We performed a retrospective review of subjects treated at 2 different medical clinics that apply the same method of auricular acupuncture (SAAT) to AGS patients. Results: A total of 137 patients presented to the 2 sites included in this study. The majority of patients were mammal product eaters before AGS; however, at the time of treatment only 7.3% of individuals (n = 10) actively consumed mammal products. Most subjects were reactive to beef (n = 135) and dairy (n = 95). The most common organ system involved in prior allergic reactions associated with AGS were gastrointestinal (n = 82, 59.9%) and dermatologic (n = 61, 44.5%). For those individuals with available outcome data on SAAT effectiveness (n = 126), 121 (96%) patients indicated that their symptoms were in remission after SAAT. Five individuals indicated that their symptoms were not in remission. Eleven individuals were unsure of treatment response or unable to be reached for follow-up. Conclusion: The SAAT method showed effectiveness in the large majority of patients. No adverse reactions were noted as a result of auricular acupuncture. This alternative medicine approach to AGS management should be further studied in prospective trials with laboratory confirmation both before and after the procedure. This low-risk treatment shows promise in treating a medical condition that causes distress in an increasing number of patients.

Diagnostic testing for galactose-alpha-1,3-galactose, United States, 2010 to 2018

BACKGROUND

Alpha-gal syndrome (AGS) is an emerging immunoglobulin E (IgE)-mediated allergy to galactose-alpha-1,3-galactose (alpha-gal). The geographic distribution and burden of AGS in the United States are unknown.

OBJECTIVE

To characterize alpha-gal IgE testing patterns and describe the trends and distribution from 2010 to 2018 in the United States.

METHODS

This retrospective analysis included all persons tested for alpha-gal IgE antibodies by Viracor-IBT Laboratories (Lee's Summit, Missouri), the primary site of testing in the United States. Data included age and sex of person tested, specimen state of origin, collection date, and result value; persons with at least 1 positive test result (≥0.1 kU/L) were compared with negatives. Proportions tested and with positive test results were calculated using the US Census population estimates.

RESULTS

Overall, 122,068 specimens from 105,674 persons were tested for alpha-gal IgE during July 1, 2010, to December 31, 2018. Nearly one-third (34,256, 32.4%) had at least 1 positive result. The number of persons receiving positive test results increased 6-fold from 1110 in 2011 to 7798 in 2018. Of those receiving positive test results, mean [SD] age was 46.9 (19.8) years; men were more likely to test positive than women (43.3% vs 26.0%). Arkansas, Virginia, Kentucky, Oklahoma, and Missouri had the highest number of persons who were tested and had a positive result per 100,000 population.

CONCLUSION

More than 34,000 persons, most presumably symptomatic, have received positive test results for IgE antibodies to alpha-gal, suggesting AGS is an increasingly recognized public health problem. The geographic distribution of persons who tested positive is consistent with exposure to Amblyomma americanum ticks.

Gelatin-Containing Vaccines for Varicella, Zoster, Measles, Mumps, and Rubella Induce Basophil Activation in Patients with Alpha-Gal Syndrome

BACKGROUND

The alpha-gal syndrome (AGS) describes a new type I allergy entity to the carbohydrate epitope galactose-α-1,3-galactose (alpha-gal), which is mainly found in mammalian food products (e.g., beef, pork, and venison). Apart from meat products, alpha-gal can also be found in products containing gelatin of bovine or porcine origin. Recent case reports pointed to severe anaphylaxis in patients suffering from AGS after vaccination with vaccines containing hydrolyzed gelatin. It was the objective of this study to evaluate if basophil activation tests (BATs) performed with such vaccines were positive in patients with AGS.

METHODS

BAT was performed with different dilutions of a gelatin-containing measles, mumps, and rubella (MMR) live vaccine; an attenuated varicella (V) vaccine; an attenuated V-zoster (VZ) vaccine; a MMR live vaccine not containing gelatin (non-gelatin MMR vaccine) in 2 patients with confirmed AGS, 2 patients highly suspicious for AGS, and 2 healthy individuals without any previous medical history for allergies.

RESULTS

All patients showed strongly positive results for all gelatin-containing vaccines (MMR vaccine, V vaccine, and VZ vaccine). Non-gelatin MMR vaccine was negative. The 2 healthy controls did not show any basophil activation.

CONCLUSIONS

Gelatin-containing vaccines should be administered with caution or avoided in patients with AGS because of their high potential to activate basophils indicating a risk for anaphylaxis. Also, BAT is a useful additional tool when it comes to screening for potentially high-risk alpha-gal-containing drugs.

Idiopathic Anaphylaxis: a Perplexing Diagnostic Challenge for Allergists

PURPOSE OF REVIEW

The aim of this systematic review is to present the proposed theories of pathogenesis for idiopathic anaphylaxis (IA), to discuss its classification, its diagnostic approach, and management.

RECENT FINDINGS

IA represents a major diagnostic challenge and is diagnosed when excluding the possible identifiable triggers of anaphylaxis. The current research, however, revealed that certain conditions including mastocytosis, mast cell activation syndromes, and hereditary alpha tryptasemia can masquerade and overlap with its symptomatology. Also, newly identified galactose-alpha-1,3-galactose mammalian red meat allergy has recently been recognized as underlying cause of anaphylaxis in some cases that were previously considered as IA. IA comprises a heterogenous group of conditions where, in some cases, inherently dysfunctional mast cells play a role in pathogenesis. The standard trigger avoidance strategies are ineffective, and episodes are unpredictable. Therefore, prompt recognition and treatment as well as prophylaxis are critical. The patients should always carry an epinephrine autoinjector.

Tick exposures and alpha-gal syndrome: A systematic review of the evidence

Alpha-gal syndrome (AGS) refers to a delayed allergic reaction to galactose-α-1,3-galactose (α-Gal) that occurs following the consumption of mammalian meat or exposure to other animal-based foods and products. Increasing evidence suggests that bites from certain tick species can lead to AGS through sensitization of a person's α-Gal specific IgE levels. This systematic review aimed to summarize the published evidence on this topic to understand post-tick exposure AGS epidemiology and health outcomes. A structured search for literature in eight bibliographic databases was conducted in January, 2020. Grey literature and verification searches were also performed. The exposure of interest was tick bites, and the outcome of interest was AGS. All primary research study designs were eligible for inclusion. References were screened for relevance, and data extraction and risk-of-bias assessment were conducted on relevant studies by two independent reviewers. Data were descriptively and narratively summarized. Of 1390 references screened, 102 relevant articles (103 unique studies) were identified (published from 2009 to 2020). Most studies (76.7 %) were case report or series. These 79 studies reported on 236 post-tick exposure AGS cases from 20 different countries, mostly the United States (33.5 %), Spain (19.5 %), Sweden (18.6 %), and France (12.7 %). The mean case age was 51.3 (SD = 16.7, range 5-85, n = 229), while 68.1 % were male (n = 226). The most commonly reported symptom was urticaria (71.2 %); 51.7 % of cases reported anaphylaxis. Twenty-one observational studies were reported, mostly (95.2 %) among clinical allergy patients. The proportion of AGS cases that recalled tick bites was highly variable across these studies. Three challenge studies evaluating tick exposures and α-Gal levels in α-Gal deficient mice were identified. The existing evidence suggests tick bites lead to α-Gal-specific IgE sensitization, which can cause AGS, but further research is needed to clarify if AGS is only attributable to certain tick species and whether other vectors may trigger AGS. Additional research is needed on risk factors for AGS development, evaluation of diagnostic immunoassays, and the epidemiology and distribution of AGS in different populations. Climate change will likely lead to future cases of AGS in new regions worldwide due to the predicted alteration of suitable tick habitats.