Alpha-Gal Allergy as a Cause of Intestinal Symptoms in a Gastroenterology Community Practice

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%.

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.

Emerging Trends in Information-Seeking Behavior for Alpha-Gal Syndrome: Infodemiology Study Using Time Series and Content Analysis

BACKGROUND

Alpha-gal syndrome is an emerging allergy characterized by an immune reaction to the carbohydrate molecule alpha-gal found in red meat. This unique food allergy is likely triggered by a tick bite. Cases of the allergy are on the rise, but prevalence estimates do not currently exist. Furthermore, varying symptoms and limited awareness of the allergy among health care providers contribute to delayed diagnosis, leading individuals to seek out their own information and potentially self-diagnose.

OBJECTIVE

The study aimed to (1) describe the volume and patterns of information-seeking related to alpha-gal, (2) explore correlations between alpha-gal and lone star ticks, and (3) identify specific areas of interest that individuals are searching for in relation to alpha-gal.

METHODS

Google Trends Supercharged-Glimpse, a new extension of Google Trends, provides estimates of the absolute volume of searches and related search queries. This extension was used to assess trends in searches for alpha-gal and lone star ticks (lone star tick, alpha gal, and meat allergy, as well as food allergy for comparison) in the United States. Time series analyses were used to examine search volume trends over time, and Spearman correlation matrices and choropleth maps were used to explore geographic and temporal correlations between alpha-gal and lone star tick searches. Content analysis was performed on related search queries to identify themes and subcategories that are of interest to information seekers.

RESULTS

Time series analysis revealed a rapidly increasing trend in search volumes for alpha-gal beginning in 2015. After adjusting for long-term trends, seasonal trends, and media coverage, from 2015 to 2022, the predicted adjusted average annual percent change in search volume for alpha-gal was 33.78%. The estimated overall change in average search volume was 627%. In comparison, the average annual percent change was 9.23% for lone star tick, 7.34% for meat allergy, and 2.45% for food allergy during this time. Geographic analysis showed strong significant correlations between alpha-gal and lone star tick searches especially in recent years (ρ=0.80; P<.001), with primary overlap and highest search rates found in the southeastern region of the United States. Content analysis identified 10 themes of primary interest: diet, diagnosis or testing, treatment, medications or contraindications of medications, symptoms, tick related, specific sources of information and locations, general education information, alternative words for alpha-gal, and unrelated or other.

CONCLUSIONS

The study provides insights into the changing information-seeking patterns for alpha-gal, indicating growing awareness and interest. Alpha-gal search volume is increasing at a rapid rate. Understanding specific questions and concerns can help health care providers and public health educators to tailor communication strategies. The Google Trends Supercharged-Glimpse tool offers enhanced features for analyzing information-seeking behavior and can be valuable for infodemiology research. Further research is needed to explore the evolving prevalence and impact of alpha-gal syndrome.

Alpha-Gal IgE Prevalence Patterns in the United States: An Investigation of 3,000 Military Recruits

BACKGROUND

IgE to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal) is an important cause of allergic reactions to mammalian meat. The "alpha-gal syndrome" is strongly associated with a preceding history of tick bites and in the United States is most commonly reported in parts of the southeast, but there has been limited investigation into national alpha-gal sensitization patterns and the relevance of other risk factors.

OBJECTIVE

To systematically investigate alpha-gal IgE prevalence, regional patterns, and risk factors.

METHODS

Alpha-gal IgE was measured by ImmunoCAP in biobanked serum samples collected from 3000 service members who presented for intake to 1 of 10 military bases in the central/eastern United States. Alpha-gal IgE sensitization (cutoff 0.1 international units/mL) was related to home of record at enlistment.

RESULTS

Of the cohort, 2456 (81.9%) subjects were male, median age was 19 years (interquartile range: 18-22 years), and alpha-gal IgE was detected in 179 (6.0%). Home of record spanned all 50 states, with a median of 36 recruits per state (range: 3-261). The highest prevalence rates were in Arkansas (39%), Oklahoma (35%), and Missouri (29%), with several other southeastern states >10%. Granular mapping revealed sensitization patterns that closely mimicked county-level Amblyomma americanum reports and Ehrlichia chaffeensis infections. Sensitization was associated with male sex, rural residence, and White race in univariate and multivariable models.

CONCLUSIONS

In this systematic survey, the prevalence of alpha-gal IgE among incoming military personnel was 6.0%. There were significant regional differences, with an overall pattern consistent with the known range of the lone star tick (A. americanum) and highest frequency in an area including Arkansas, Oklahoma, and Missouri.

Gastrointestinal-isolated Distress is Common in Alpha-gal Allergic Patients on Mammalian Meat Challenge

BACKGROUND AND AIMS

Alpha-gal allergy causes a delayed reaction to mammalian meats and has been reported worldwide. Patients with the allergy may present with isolated gastrointestinal (GI) symptoms, but this phenotype is poorly understood.

METHODS

We pooled and analyzed symptoms and demographics of patients from two prospective cohorts of patients with a diagnosis of alpha-gal allergy who reacted after eating mammalian meat under observation. We compared the characteristics of patients who demonstrated GI-isolated symptoms on a challenge with those who exhibited symptoms outside the GI tract (skin, respiratory, and circulatory).

RESULTS

Among the 91 children and adult alpha-gal allergic patients who exhibited symptoms after oral challenge with mammalian meat, 72.5% experienced GI distress with one or more GI symptoms, which was the most frequent class of symptoms, compared with skin changes in 57.1% and respiratory distress in 5.5%. The most common GI symptoms were abdominal pain (71%) and vomiting (22.0%). GI-isolated symptoms occurred in 37 patients (40.7%) who reacted, and those patients reacted more quickly than patients who exhibited systemic symptoms (median onset of symptoms in GI-isolated group 90 min vs 120 min) and were more likely to be children than adults (relative risk=1.94, 95% CI: 1.04-3.63).

CONCLUSIONS

Isolated-GI distress occurred in 4 in every 10 alpha-gal allergic individuals who developed symptoms on oral food challenge with mammalian meat. Alpha-gal allergic patients, particularly children, may exhibit GI distress alone, and adult and pediatric gastroenterologists should be aware of the diagnosis and management of the allergy.

Getting the BS out of Irritable Bowel Syndrome with Diarrhea (IBS-D): Let's Make a Diagnosis

PURPOSE OF REVIEW

Irritable bowel syndrome with diarrhea (IBS-D) is diagnosed when chronic symptoms of abdominal pain accompany loose stools, and alarm features, such as fever, anemia, rectal bleeding, and weight loss are absent. This combination of symptoms makes structural disorders, such as inflammatory bowel disease or cancer, unlikely, but does not exclude other conditions that cause these symptoms. The question is whether making a "positive diagnosis" of IBS-D based on symptoms alone and instituting therapy based on that diagnosis still makes sense.

RECENT FINDINGS

Clinical observations suggest that at least two-thirds of cases of IBS-D can be explained by three mechanisms: a) food intolerances (~ 30-40%), b) bile acid diarrhea (~ 20-30%), and c) disturbed microbial flora (~ 15-20%). Other conditions that are less frequent but can cause IBS symptoms or be confused with IBS include: celiac disease, microscopic colitis, mastocytosis/mast cell activation, and drug side-effects. Many cases of IBS-D have a discoverable, underlying cause that can direct therapy more efficiently.

Alpha-gal syndrome: A review for the dermatologist

Alpha-gal syndrome (AGS) is an allergy to "red meat" and other mammalian products due to immunoglobulin E (IgE) antibodies against the sugar moiety galactose-alpha-1,3-galactose (alpha-gal), which is acquired following tick bites. Clinically, AGS presents with urticaria, abdominal pain, nausea, and occasionally anaphylaxis, and has wide inter- and intra-personal variability. Because symptom onset is generally delayed by 2 to 6 hours after meat consumption, AGS can be easily confused with other causes of urticaria and anaphylaxis, such as chronic spontaneous urticaria (CSU) and mast cell activation syndrome (MCAS). Diagnosis relies on a combination of clinical history, positive alpha-gal IgE blood testing and improvement on a mammalian-restricted diet. Management of the syndrome centers primarily on avoidance of mammalian meats (and occasionally dairy and other products) as well as acute management of allergic symptoms. Counseling about tick avoidance measures is also important as AGS will wane over time in many patients.

Alpha-gal syndrome-Food or drug allergy: A case report

Alpha-gal syndrome is an immunoglobulin E-mediated hypersensitivity characterized by delayed allergic reactions to ingested products containing alpha-gal carbohydrate. We present a patient with recurrent urticaria and suspected repaglinide hypersensitivity, who was eventually diagnosed with alpha-gal syndrome, wanting to emphasize possible drug allergy misdiagnosis and required caution with the medication choice.

Nonanaphylactic Variant of Alpha-Gal Syndrome as an Etiology for Chronic Gastrointestinal Symptoms in Children

We report 3 pediatric patients who presented with only nonanaphylactic symptoms of alpha-gal syndrome. This report highlights the necessity of not discounting alpha-gal syndrome from a differential diagnosis for patients with recurrent gastrointestinal distress and emesis after consuming mammalian meat, even in the absence of an anaphylactic reaction.

Clinical Presentation of Alpha-Gal Syndrome in Pediatric Gastroenterology and Response to Mammalian Dietary Elimination

INTRODUCTION

Alpha-gal syndrome is an immunoglobulin E (IgE)-mediated delayed hypersensitivity reaction to nonprimate mammalian products, which has a newly established gastrointestinal (GI) phenotype in adults. We assessed the GI presentation and treatment response in children.

METHODS

This is a retrospective study of patients presenting in a pediatric gastroenterology clinic tested for alpha-gal IgE.

RESULTS

Forty of 199 patients (20%) tested had a positive alpha-gal-specific IgE, with 77.5% reporting GI symptoms in isolation. Of the 30 that attempted dietary elimination, 8 (27%) experienced full resolution of symptoms.

DISCUSSION

Alpha-gal syndrome can present with isolated GI symptoms in children.

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.

AGA Clinical Practice Update on Alpha-Gal Syndrome for the GI Clinician: Commentary

DESCRIPTION

Alpha-gal syndrome is an emerging allergy first described in the early 2000s. The allergy can cause anaphylaxis, gastrointestinal (GI) symptoms, and skin changes one to several hours after ingestion of mammalian products. A GI phenotype that is increasingly recognized manifests with nonspecific symptoms like abdominal pain, diarrhea, nausea or vomiting without predominant skin, respiratory or circulatory symptoms. Though the syndrome has been reported on all continents except Antarctica, in the United States most reports are within the range of the Lone Star tick, extending from New York and Iowa to Texas and Florida. The purpose of this AGA Clinical Practice Update (CPU) Commentary is to increase awareness among gastroenterologists about the presentation and management of alpha-gal syndrome.

METHODS

This CPU commentary was commissioned and approved by the AGA Institute Clinical Practice Updates Committee (CPUC) and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the CPUC and external peer review through standard procedures of Clinical Gastroenterology and Hepatology. This expert commentary incorporates important as well as recently published studies in this field, and it reflects the experiences of the authors. Formal ratings regarding the quality of evidence or strength of the presented considerations were not included since systematic reviews were not performed.

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.

Food Allergies and Alpha-gal Syndrome for the Gastroenterologist

PURPOSE OF REVIEW

Food allergies are typically not considered as a cause of gastrointestinal (GI) distress without additional allergic symptoms, apart from celiac disease and eosinophilic esophagitis. However, recent reports of patients with alpha-gal syndrome who presented with GI-only symptoms like abdominal pain, vomiting, and diarrhea challenge this paradigm. Alpha-gal syndrome is an IgE-mediated allergy characterized by delayed reactions after eating mammalian meat or mammalian-derived products that contain galactose-alpha-1,3-galactose (alpha-gal). The purpose of this review is to discuss our current understanding of food allergies, GI illness, and the GI manifestations of alpha-gal syndrome.

RECENT FINDINGS

Among Southeastern U.S. GI clinic patients who screened positive for serum alpha-gal IgE, a majority of patients reported significant symptom improvement on an alpha-gal-avoidant diet, suggesting that the allergy had played a role in their GI symptoms. Diagnosis of alpha-gal syndrome is typically made with concerning allergic symptoms, elevated alpha-gal specific IgE in the serum, and symptom improvement on an alpha-gal avoidant diet. Alpha-gal syndrome can cause a delayed allergic response that is increasingly recognized worldwide, including among patients with predominant GI symptoms.

The Two-Sided Experimental Model of ImmunoCAP Inhibition Test as a Useful Tool for the Examination of Allergens Cross-Reactivity on the Example of α-Gal and Mammalian Meat Sensitization-A Preliminary Study

Cross-reactivity of allergens is the cause of various, sometimes unexpected, clinical reactions. There are no standard methods to investigate cross-reactivity. We present an experimental model of a two-sided inhibition test (IT) on ImmunoCAP membranes (CAP). We constructed the described model based on the known cross-allergy syndrome to red meat developing in people bitten by ticks (α-Gal syndrome; AGS). Some individuals who are bitten by ticks develop IgE antibodies specific to the carbohydrate determinant, galactose-α-1,3-galactose (α-Gal), present in the tick's saliva. These antibodies can cross-react with α-Gal molecules expressed on mammalian meat proteins. The well-known property of anti-α-Gal IgE antibodies binding by various sources of this allergen was used by us in the proposed model of the two-sided inhibition test on ImmunoCAP membranes. We expected that anti-α-Gal IgE antibodies bind allergens from mammalian meat and blocking them abolishes this reactivity, and the two-sided inhibition test model we proposed on ImmunoCAP membranes allowed us to observe such a relationship. We conducted the experiment three times on biological material from people with different clinical manifestations of allergy to α-Gal, each time obtaining similar results. In conclusion, the model of bilateral inhibition on ImmunoCAP membranes proposed by us seems to be an attractive, simple tool for direct testing of allergic cross-reactivity.

Alpha-Gal Syndrome in the Infectious Diseases Clinic: A Series of 5 Cases in Central North Carolina

Background

Alpha-gal syndrome (AGS) is a recently described allergy to galactose-α-1,3-galactose, an oligosaccharide present in mammalian meat. AGS can present with angioedema, urticaria, and anaphylaxis arising 3-6 hours after ingestion, although symptoms such as gastrointestinal distress, fatigue, and arthralgias are also reported. Because AGS appears to be associated with tick bites, patients may present to infectious diseases (ID) clinics for evaluation.

Methods

We documented a series of 5 patients referred to the University of North Carolina ID Clinic between 2020 and 2022 for various tick-borne infections that were found to have symptoms and laboratory testing consistent with AGS. Patients were subsequently referred to the Allergy and Immunology Clinic.

Results

Patients were referred to the ID Clinic for persistent symptoms following positive tick-borne disease testing or presumed tick-borne infection. All patients had an elevated alpha-gal immunoglobulin E and clinical presentation consistent with AGS. Common symptoms included episodic gastrointestinal distress (eg, cramping, nausea, diarrhea), fatigue, arthralgias, and subjective cognitive impairment, but a notable absence of severe anaphylaxis. Four patients were seen by at least 1 nonallergy specialist prior to referral to ID. Patients reported substantial improvement in their symptoms following dietary restriction.

Conclusions

ID physicians should be aware of AGS as a cause of persistent, nonspecific symptoms following a tick exposure or tick-borne illness. Further research is needed to determine the prevalence of alpha-gal sensitization and AGS following tick-borne bites.

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.