Tick Saliva and the Alpha-Gal Syndrome: Finding a Needle in a Haystack

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.

Analysis of Amblyomma americanum microRNAs in response to Ehrlichia chaff eensis infection and their potential role in vectorial capacity

Background

MicroRNAs (miRNAs) represent a subset of small noncoding RNAs and carry tremendous potential for regulating gene expression at the post-transcriptional level. They play pivotal roles in distinct cellular mechanisms including inhibition of bacterial, parasitic, and viral infections via immune response pathways. Intriguingly, pathogens have developed strategies to manipulate the host's miRNA profile, fostering environments conducive to successful infection. Therefore, changes in an arthropod host's miRNA profile in response to pathogen invasion could be critical in understanding host-pathogen dynamics. Additionally, this area of study could provide insights into discovering new targets for disease control and prevention. The main objective of the present study is to investigate the functional role of differentially expressed miRNAs upon Ehrlichia chaf feensis, a tick-borne pathogen, infection in tick vector, Amblyomma americanum .

Methods

Small RNA libraries from uninfected and E. chaffeensis -infected Am. americanum midgut and salivary gland tissues were prepared using the Illumina Truseq kit. Small RNA sequencing data was analyzed using miRDeep2 and sRNAtoolbox to identify novel and known miRNAs. The differentially expressed miRNAs were validated using a quantitative PCR assay. Furthermore, a miRNA inhibitor approach was used to determine the functional role of selected miRNA candidates.

Results

The sequencing of small RNA libraries generated >147 million raw reads in all four libraries and identified a total of >250 miRNAs across the four libraries. We identified 23 and 14 differentially expressed miRNAs in salivary glands, and midgut tissues infected with E. chaffeensis , respectively. Three differentially expressed miRNAs (miR-87, miR-750, and miR-275) were further characterized to determine their roles in pathogen infection. Inhibition of target miRNAs significantly decreased the E. chaffeensis load in tick tissues, which warrants more in-depth mechanistic studies.

Conclusions

The current study identified known and novel miRNAs and suggests that interfering with these miRNAs may impact the vectorial capacity of ticks to harbor Ehrlichia . This study identified several new miRNAs for future analysis of their functions in tick biology and tick-pathogen interaction studies.

Immunoassay Testing of Alpha-Gal Specific Immunoglobulin-E: Data from a National Reference Laboratory

BACKGROUND

Immunoassay measurements of serum alpha-gal (AG) specific IgE (sIgE) enable antibody detection and quantification with high sensitivity and specificity and are essential for AG syndrome diagnosis and patient management. We here present and analyze results from over 15 000 patient serum samples tested using the ImmunoCAP (Thermo/Phadia) assay.

METHODS

AG-sIgE levels and positivity rates were correlated to patient age, gender, geographic location, repeat testing results, sIgE levels to co-tested red meat whole allergen extracts, and Rocky Mountain spotted fever (RMSF) serology performed on a subset of patient samples.

RESULTS

Of the tested samples, 36.7% contained detectable (>0.1 KUA/L) AG-sIgE. Antibody levels were higher in patients of older age, in samples submitted from lower midwestern and southern states, and during the June-December period of the year. Specific IgE to co-tested red meat whole allergens showed moderate to strong correlation to AG-sIgE and were of lower levels. Samples with positive RMSF IgG titers (≥1:64) were of overall higher AG-IgE levels.

CONCLUSION

Findings are consistent with the role of lone star ticks in AG syndrome pathogenesis. Levels of measured sIgE to AG are higher than co-tested sIgE to red meat whole allergen, consistent with the improved diagnostic performance of component-resolved testing.

Use of antithymocyte globulin (rabbit) in a patient with known alpha-gal syndrome undergoing allogenic stem cell transplantation

INTRODUCTION

Alpha-gal syndrome (AGS) is a hypersensitivity disorder in which tick bites-most commonly from the lone star tick (Ambylomma americanum)-trigger immunoglobulin E-mediated hypersensitivity reaction upon exposure to oligosaccharide galactosse-alpha-1,3-galactose (α-gal). α-gal is most notorious for being found in "red meat" products but is present in mammalian meats such as beef, pork, lamb, rabbit, and others. Manifestations of AGS hypersensitivity are variable. There is currently no in vivo data describing allergic reactions against rabbit products in patients with AGS.

CASE REPORT

Here, we describe a case of a 44-year-old male with myelodysplastic syndrome and a known history of AGS undergoing allogeneic hematopoietic cell transplantation (allo-HSCT) with the use of rabbit antithymocyte globulin (rATG) for graft-versus-host disease (GVHD) prophylaxis.

MANAGEMENT AND OUTCOME

The risk of cross-reactivity against rATG in our patient with AGS could not be ruled out and, therefore, a test dose was administered. The patient tolerated the test dose with no signs of anaphylaxis. After demonstrating tolerance to the test dose, rATG was utilized for GVHD prophylaxis.

DISCUSSION

Due to the heterogeneity of AGS manifestations in patients, the use of rATG in patients with known AGS should be considered on a case-by-case basis. The administration of a test dose may help predict the occurrence of severe hypersensitivity reactions. The limited data surrounding the risk of AGS with rabbit-containing products and the various indications for the use of rATG warrants more in-depth study of the reactivity of this medication in this population.

Gene-edited pigs: a translational model for human food allergy against alpha-Gal and anaphylaxis

The prevalence of food allergy is rising and is estimated to approach 10%. Red meat allergy is the first known food allergy elicited by immunoglobulin E (IgE) antibodies recognizing a carbohydrate. Due to the loss of function of the alpha-1,3-galactosyltransferase (GGTA1) gene in humans, the disaccharide galactose-α-1,3-galactose (α-Gal) cannot be synthesized and therefore became immunogenic. IgE sensitization is elicited through the skin by repetitive tick bites transmitting α-Gal. The underlying mechanisms regarding innate and adaptive immune cell activation, including the B-cell isotype switch to IgE, are poorly understood, requiring further research and physiologically relevant animal models. Here, we describe a new animal model of red meat allergy using percutaneous α-Gal sensitization of gene-edited GGTA1-deficient pigs. Total and α-Gal-specific IgG, IgG1, IgG2, IgG4, and IgE levels were tracked. Further key factors associated with allergic skin inflammation, type 2 immunity, and allergy development were measured in PBMCs and skin samples. Significant increases in α-Gal-specific IgG1 and IgE levels indicated successful sensitization to the allergen α-Gal. Intracutaneous sensitizations with α-Gal recruited lymphocytes to the skin, including elevated numbers of T helper 2 (Th2) cells. Finally, α-Gal-sensitized pigs not only recognized α-Gal as non-self-antigen following α-Gal exposure through the skin but also developed anaphylaxis upon antigen challenge. Based on the similarities between the porcine and human skin, this new large animal model for α-Gal allergy should help to unveil the consecutive steps of cutaneous sensitization and aid the development of prophylactic and treatment interventions.

Tick bite-induced alpha-gal syndrome and immunologic responses in an alpha-gal deficient murine model

Introduction

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated just in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of specific IgE. However, the precise mechanism by which tick bites influence the host's immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism.

Methods

Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined.

Results

Our results showed a significant increase in the total IgE, IgG1, and α-gal IgG1 antibodies titers in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen.

Conclusion

This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

Local Sources of Protein in Low- and Middle-Income Countries: How to Improve the Protein Quality?

Protein inadequacy is a major contributor to nutritional deficiencies and adverse health outcomes of populations in low- and middle-income countries (LMICs). People in LMICs often consume a diet predominantly based on staple crops, such as cereals or starches, and derive most of their daily protein intakes from these sources. However, plant-based sources of protein often contain low levels of indispensable amino acids (IAAs). Inadequate intake of IAA in comparison with daily requirements is a limiting factor that results in protein deficiency, consequently in the long-term stunting and wasting. In addition, plant-based sources contain factors such as antinutrients that can diminish protein digestion and absorption. This review describes factors that affect protein quality, reviews dietary patterns of populations in LMICs and discusses traditional and novel small- and large-scale techniques that can improve the quality of plant protein sources for enhanced protein bioavailability and digestibility as an approach to tackle malnutrition in LMICs. The more accessible small-scale food-processing techniques that can be implemented at home in LMICs include soaking, cooking, and germination, whereas many large-scale techniques must be implemented on an industrial level such as autoclaving and extrusion. Limitations and considerations to implement those techniques locally in LMICs are discussed. For instance, at-home processing techniques can cause loss of nutrients and contamination, whereas limitations with larger scale techniques include high energy requirements, costs, and safety considerations. This review suggests that combining these small- and large-scale approaches could improve the quality of local sources of proteins, and thereby address adverse health outcomes, particularly in vulnerable population groups such as children, adolescents, elderly, and pregnant and lactating women.

High levels of alpha-gal with large variation in the salivary glands of lone star ticks fed on human blood

Tick bites, associated with the secretion of tick saliva containing the xenoglycan galactose-alpha-1, 3-galactose (alpha-gal or aGal), are recognized as the causal factors of alpha-Gal syndrome (AGS; or red meat allergy) in humans. AGS occurs after the increased production of IgE antibodies against aGal, which is found in most mammalian cells, except for the Old World monkey and humans. The aGal sensitization event has been linked to an initial tick bite, followed by consumption of red meat containing the aGal glycan, which triggers the onset of the allergic response resulting in urticaria, anaphylaxis, or even death. In North America, the lone star tick, Amblyomma americanum, has been identified as the main culprit for AGS. However, only a subset of the human population exposed to lone star tick bites develops AGS. This suggests the presence of unidentified variables associated with the sensitization event. To evaluate the quantitative variations of the aGal in ticks, we evaluated the differences in aGal levels in different strains of A. americanum ticks partially fed on different blood sources using an artificial feeding system and animal hosts. We found significantly higher aGal levels in the female ticks fed on human blood than those fed on the blood of other mammals with large variations among different tick populations and individuals. We propose that host-specific genetic components in the A. americanum ticks are involved in the production of high aGal epitope in the tick saliva, which provides a part of the explanation for the variables associated with the AGS sensitization event of the tick bite.

Multi-omics analysis of zebrafish response to tick saliva reveals biological processes associated with alpha-Gal syndrome

The alpha-Gal syndrome (AGS) is a tick-borne allergy. A multi-omics approach was used to determine the effect of tick saliva and mammalian meat consumption on zebrafish gut transcriptome and proteome. Bioinformatics analysis using R software was focused on significant biological and metabolic pathway changes associated with AGS. Ortholog mapping identified highly concordant human ortholog genes for the detection of disease-enriched pathways. Tick saliva treatment increased zebrafish mortality, incidence of hemorrhagic type allergic reactions and changes in behavior and feeding patterns. Transcriptomics analysis showed downregulation of biological and metabolic pathways correlated with anti-alpha-Gal IgE and allergic reactions to tick saliva affecting blood circulation, cardiac and vascular smooth muscle contraction, behavior and sensory perception. Disease enrichment analysis revealed downregulated orthologous genes associated with human disorders affecting nervous, musculoskeletal, and cardiovascular systems. Proteomics analysis revealed suppression of pathways associated with immune system production of reactive oxygen species and cardiac muscle contraction. Underrepresented proteins were mainly linked to nervous and metabolic human disorders. Multi-omics data revealed inhibition of pathways associated with adrenergic signaling in cardiomyocytes, and heart and muscle contraction. Results identify tick saliva-related biological pathways supporting multisystemic organ involvement and linking α-Gal sensitization with other illnesses for the identification of potential disease biomarkers.

Tick salivary glycans - a sugar-coated tick bite

Ticks are hematophagous arthropods that transmit disease-causing pathogens worldwide. Tick saliva deposited into the tick-bite site is composed of an array of immunomodulatory proteins that ensure successful feeding and pathogen transmission. These salivary proteins are often glycosylated, and glycosylation is potentially critical for the function of these proteins. Some salivary glycans are linked to the phenomenon of red meat allergy - an allergic response to red meat consumption in humans exposed to certain tick species. Tick salivary glycans are also invoked in the phenomenon of acquired tick resistance wherein non-natural host species exposed to tick bites develop an immune response that thwarts subsequent tick feeding. This review dwells on our current knowledge of these two phenomena, thematically linked by salivary glycans.

Tick bite-induced Alpha-Gal Syndrome and Immunologic Responses in an Alpha-Gal Deficient Murine Model

Introduction

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of α-gal specific IgE. However, the precise mechanism by which tick bites influence the hosťs immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism.

Methods

Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined.

Results

Our results showed a significant increase in the titer of total IgE, IgG1, and α-gal IgG1 antibodies in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen, while Am. maculatum did not.

Conclusion

This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

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.

Allergic reactions to tick saliva components in zebrafish model

BACKGROUND

Alpha-Gal syndrome (AGS) is a tick-borne food allergy caused by IgE antibodies against the glycan galactose-alpha-1,3-galactose (α-Gal) present in glycoproteins and glycolipids from mammalian meat. To advance in the diagnosis and treatment of AGS, further research is needed to unravel the molecular and immune mechanisms underlying this syndrome. The objective of this study is the characterization of tick salivary components and proteins with and without α-Gal modifications involved in modulating human immune response against this carbohydrate.

METHODS

Protein and α-Gal content were determined in tick saliva components, and proteins were identified by proteomics analysis of tick saliva fractions. Pathophysiological changes were recorded in the zebrafish (Danio rerio) model after exposure to distinct Ixodes ricinus tick salivary components. Serum samples were collected from zebrafish at day 8 of exposure to determine anti-α-Gal, anti-glycan, and anti-tick saliva protein IgM antibody titers by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Zebrafish treated with tick saliva and saliva protein fractions combined with non-protein fractions demonstrated significantly higher incidence of hemorrhagic type allergic reactions, abnormal behavioral patterns, or mortality when compared to the phosphate-buffered saline (PBS)-treated control group. The main tick salivary proteins identified in these fractions with possible functional implication in AGS were the secreted protein B7P208-salivary antigen p23 and metalloproteases. Anti-α-Gal and anti-tick salivary gland IgM antibody titers were significantly higher in distinct saliva protein fractions and deglycosylated saliva group when compared with PBS-treated controls. Anti-glycan antibodies showed group-related profiles.

CONCLUSIONS

Results support the hypothesis that tick salivary biomolecules with and without α-Gal modifications are involved in modulating immune response against this carbohydrate.

Perioperative implications of patients with alpha gal allergies

Alpha Gal Syndrome (AGS) is an emerging immune response to mammalian products (MP) containing the oligosaccharide galactose-α-1,3 galactose (α-Gal) which includes meats and inactive ingredients in certain medications. This becomes clinically important in the perioperative realm as MPs are commonly found in the operating room, and pre- and post-operative settings, and can trigger responses as severe as anaphylaxis. In this review, authors discuss the epidemiology, diagnosis and treatment of AGS reactions. Additionally, strategies are explored in order to screen and prevent exposure to MP with a multidisciplinary approach. While this emerging allergy is still not fully understood, it is of paramount importance that all anesthesia providers recognize the implications of MP exposure in AGS patients and ultimately prevent harm in this highly vulnerable population.

Identification, Baculoviral Expression, and Biochemical Characterization of a Novel Cholinesterase of Amblyomma americanum (Acari: Ixodidae)

A cDNA encoding a novel cholinesterase (ChE, EC 3.1.1.8) from the larvae of Amblyomma americanum (Linnaeus) was identified, sequenced, and expressed in Sf21 insect cell culture using the baculoviral expression vector pBlueBac4.5/V5-His. The open reading frame (1746 nucleotides) of the cDNA encoded 581 amino acids beginning with the initiation codon. Identical cDNA sequences were amplified from the total RNA of adult tick synganglion and salivary gland, strongly suggesting expression in both tick synganglion and saliva. The recombinant enzyme (rAaChE1) was highly sensitive to eserine and BW284c51, relatively insensitive to tetraisopropyl pyrophosphoramide (iso-OMPA) and ethopropazine, and hydrolyzed butyrylthiocholine (BuTCh) 5.7 times as fast as acetylthiocholine (ATCh) at 120 µM, with calculated K_M values for acetylthiocholine (ATCh) and butyrylthiocholine of 6.39 µM and 14.18 µM, respectively. The recombinant enzyme was highly sensitive to inhibition by malaoxon, paraoxon, and coroxon in either substrate. Western blots using polyclonal rabbit antibody produced by immunization with a peptide specific for rAaChE1 exhibited reactivity in salivary and synganglial extract blots, indicating the presence of AaChE1 antigenic protein. Total cholinesterase activities of synganglial or salivary gland extracts from adult ticks exhibited biochemical properties very different from the expressed rAaACh1 enzyme, evidencing the substantial presence of additional cholinesterase activities in tick synganglion and saliva. The biological function of AaChE1 remains to be elucidated, but its presence in tick saliva is suggestive of functions in hydrolysis of cholinergic substrates present in the large blood mean and potential involvement in the modulation of host immune responses to tick feeding and introduced pathogens.

Analysis of Immunogenic Galactose-α-1,3-galactose-Containing N-Glycans in Beef, Mutton, and Pork Tenderloin by Combining Matrix-Assisted Laser Desorption/Ionization-Mass Spectroscopy and Capillary Electrophoresis Hyphenated with Mass Spectrometry via Electrospray Ionization

Severe allergic reactions to certain types of meat following tick bites have been reported in geographic regions which are endemic with ticks. This immune response is directed to a carbohydrate antigen (galactose-α-1,3-galactose or α-Gal), which is present in glycoproteins of mammalian meats. At the moment, asparagine-linked complex carbohydrates (N-glycans) with α-Gal motifs in meat glycoproteins and in which cell types or tissue morphologies these α-Gal moieties are present in mammalian meats are still unclear. In this study, we analyzed α-Gal-containing N-glycans in beef, mutton, and pork tenderloin and provided for the first time the spatial distribution of these types of N-glycans in various meat samples. Terminal α-Gal-modified N-glycans were found to be highly abundant in all analyzed samples (55, 45, and 36% of N-glycome in beef, mutton, and pork, respectively). Visualizations of the N-glycans with α-Gal modification revealed that this motif was mainly present in the fibroconnective tissue. To conclude, this study contributes to a better understanding of the glycosylation biology of meat samples and provides guidance for processed meat products, in which only meat fibers are required as an ingredient (i.e., sausages or canned meat).

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.

Incidence and associated factors of cetuximab-induced hypersensitivity infusion reactions in 1392 cancer patients treated in four French areas: a possible association with Lyme disease?

BACKGROUND

Previous studies have observed an increased incidence of Cetuximab-induced hypersensitivity infusion reactions (CI-IRs) in the southeastern states of the USA. Tick's bites were suspected of generating cross-reactions between cetuximab and alpha-gal. This study aims was to describe the incidence and associated risk factors of CI-IRs, in the French areas chosen according to their Lyme disease incidence.

PATIENTS AND METHODS

A retrospective chart review was conducted on patients that received cetuximab infusion from January 2010 to June 2019 in 4 French areas with different Lyme disease incidence rates.

RESULTS

Of 1392 patients, 117 (8.4%) experienced a CI-IR, including 68 severe (grade 3 or 4) reactions (4.9%). This CI-IR incidence was significantly higher in the Lyme disease high-risk area than in the other areas (13.2% versus 7.1%, 8.1% and 6.4%; P = 0.016). Sex (P = 0.53), premedication (P = 0.91), primary cancer location (P = 0.46) and chemotherapy regimen type (P = 0.78) had no impact on CI-IR incidence in the overall population. In the head and neck squamous cell carcinoma (HNSCC) patient subgroup, CI-IRs were significantly more frequent in the high-risk area (16.4% versus 6.7%, 7.1% and 7.0%; P = 0.0015).

CONCLUSION

This study suggests that patients treated in the French area with the highest incidence of Lyme disease are at a higher risk of CI-IRs.

Northward Expansion of Amblyomma americanum (Acari: Ixodidae) into Southwestern Michigan

Amblyomma americanum (Linnaeus) (Acari: Ixodidae) (lone star tick) is an aggressive, generalist parasite that vectors numerous important human and animal pathogens. In recent decades its geographic range has expanded northwards from endemic regions in the southeastern and southcentral United States. In 2019 five questing A. americanum ticks, comprising two life stages were detected at one site in southwestern Michigan, satisfying one CDC criterium for an established population for the first time in recent history in the state. To better characterize the extent of emerging A. americanum, we conducted active surveillance (i.e., drag sampling) in summer 2020 throughout Michigan's southern counties and detected one adult A. americanum from each of six widespread sites, including where they had been detected in 2019. A larger established population was identified at another site in Berrien County, which yielded 691 A. americanum comprising three life stages, and questing phenologies here were similar to that reported for other endemic regions. Statewide surveillance in 2021 revealed no A. americanum outside of Berrien County, but establishment criteria were met again at the two sites where established populations were first detected respectively in 2019 and 2020. These observations may represent the successful invasion of A. americanum into Michigan. Data from passive (1999-2020) and active surveillance (2004-2021) efforts, including a domestic animal sentinel program (2015-2018), are reported to provide context for this nascent invasion. Continued active surveillance is needed to help inform the public, medical professionals, and public health officials of the health risks associated with this vector.

Redox Imbalance and Its Metabolic Consequences in Tick-Borne Diseases

One of the growing global health problems are vector-borne diseases, including tick-borne diseases. The most common tick-borne diseases include Lyme disease, tick-borne encephalitis, human granulocytic anaplasmosis, and babesiosis. Taking into account the metabolic effects in the patient’s body, tick-borne diseases are a significant problem from an epidemiological and clinical point of view. Inflammation and oxidative stress are key elements in the pathogenesis of infectious diseases, including tick-borne diseases. In consequence, this leads to oxidative modifications of the structure and function of phospholipids and proteins and results in qualitative and quantitative changes at the level of lipid mediators arising in both reactive oxygen species (ROS) and ROS enzyme–dependent reactions. These types of metabolic modifications affect the functioning of the cells and the host organism. Therefore, links between the severity of the disease state and redox imbalance and the level of phospholipid metabolites are being searched, hoping to find unambiguous diagnostic biomarkers. Assessment of molecular effects of oxidative stress may also enable the monitoring of the disease process and treatment efficacy.

Range Expansion of Native and Invasive Ticks, a Looming Public Health Threat

Native and invasive tick species pose a serious public health concern in the United States. Range expansion of several medically important tick species has resulted in an increasing number of communities at risk for exposure to ticks and tickborne pathogens.

The tick and I: Parasite-host interactions between ticks and humans

Ticks, particularly hard ticks (Ixodidae), which are among the most important vectors of dangerous infectious agents, feed on their hosts for extended periods of time. With this lifestyle, numerous adaptations have evolved in ticks and their hosts, the pharmacological importance of which is increasingly being recognized. Many bioactive substances in tick saliva are being considered as the basis of new drugs. For example, components of tick cement can be developed into tissue adhesives or wound closures. Analgesic and antipruritic salivary components inhibit histamine or bradykinin, while other tick-derived molecules bind opioid or cannabinoid receptors. Tick saliva inhibits the extrinsic, intrinsic, or common pathway of blood coagulation with implications for the treatment of thromboembolic diseases. It contains vasodilating substances and affects wound healing. The broad spectrum of immunomodulatory and immunosuppressive effects of tick saliva, such as inhibition of chemokines or cellular immune responses, allows development of drugs against inflammation in autoimmune diseases and/or infections. Finally, modern vaccines against ticks can curb the spread of serious infections. The medical importance of the complex tick-host interactions is increasingly being recognized and translated into first clinical applications. Using selected examples, an overview of the mutual adaptations of ticks and hosts is given here, focusing on their significance to medical advance.

Recently Evolved Francisella-Like Endosymbiont Outcompetes an Ancient and Evolutionarily Associated Coxiella-Like Endosymbiont in the Lone Star Tick (Amblyomma americanum) Linked to the Alpha-Gal Syndrome

Background

Ticks are hematophagous arthropods that transmit various bacterial, viral, and protozoan pathogens of public health significance. The lone star tick (Amblyomma americanum) is an aggressive human-biting tick that transmits bacterial and viral pathogens, and its bites are suspected of eliciting the alpha-gal syndrome, a newly emerged delayed hypersensitivity following consumption of red meat in the United States. While ongoing studies have attempted to investigate the contribution of different tick-inherent factors to the induction of alpha-gal syndrome, an otherwise understudied aspect is the contribution of the tick microbiome and specifically obligate endosymbionts to the establishment of the alpha-gal syndrome in humans.

Materials and Methods

Here we utilized a high-throughput metagenomic sequencing approach to cataloging the entire microbial communities residing within different developmental stages and tissues of unfed and blood-fed ticks from laboratory-maintained ticks and three new geographical locations in the United States. The Quantitative Insights Into Microbial Ecology (QIIME2) pipeline was used to perform data analysis and taxonomic classification. Moreover, using a SparCC (Sparse Correlations for Compositional data) network construction model, we investigated potential interactions between members of the microbial communities from laboratory-maintained and field-collected ticks.

Results

Overall, Francisellaceae was the most dominant bacteria identified in the microbiome of both laboratory-raised and field-collected Am. americanum across all tissues and developmental stages. Likewise, microbial diversity was seen to be significantly higher in field-collected ticks compared with laboratory-maintained ticks as seen with a higher number of both Operational Taxonomic Units and measures of species richness. Several potential positive and negative correlations were identified from our network analysis. We observed a strong positive correlation between Francisellaceae, Rickettsiaceae, and Midichloriaceae in both developmental stages and tissues from laboratory-maintained ticks, whereas ovarian tissues had a strong positive correlation of bacteria in the family Xanthobacteraceae and Rhizobiaceae. A negative interaction was observed between Coxiellaceae and Francisellaceae in Illinois, and all the bacteria detected from ticks from Delaware were negatively correlated.

Conclusion

This study is the first to catalog the microbiome of Am. americanum throughout its developmental stages and different tissue niches and report the potential replacement of Coxiellaceae by Francisellaceae across developmental stages and tissues tested except in ovarian tissues. These unique and significant findings advance our knowledge and open a new avenue of research to further understand the role of tick microbiome in tick-borne diseases and develop a holistic strategy to control alpha-gal syndrome.

Tick Intrastadial Feeding and Its Role on IgE Production in the Murine Model of Alpha-gal Syndrome: The Tick "Transmission" Hypothesis

Recent studies have provided strong evidence indicating that lone star tick bites are a cause of AGS (alpha-gal syndrome, also known as red meat allergy RMA) in humans. AGS is characterized by an increase in IgE antibody production against galactose-alpha-1,3-galactose (aGal), which is a common glycan found in mammalian tissue, except in Old World monkeys and humans. The main causative factor of AGS, the lone star tick (Amblyomma americanum), is broadly distributed throughout the east and midwest of the United States and is a vector of a wide range of human and animal pathogens. Our earlier glycomics study of the salivary glands of partially fed male and female ticks revealed relatively high levels of aGal epitopes. In this study, we found that partially fed males of A. americanum on bovine blood, which engage in multiple intrastadial feedings, carry a large amount of aGal in the salivary glands. In our current work, we aimed to test whether ticks mediate the transmission of the aGal sensitizer acquired from nonhuman blood to humans in the intrastadial host switch (referred to as the "transmission" hypothesis). To test this hypothesis, we used an alpha-galactosyltransferase knockout mutant mouse (aGT-KO) model system infested with ticks that were unfed or partially fed on bovine blood. Based on the levels of total IgE and specific IgG and IgE antibodies against aGal after tick feedings, aGT-KO mice significantly responded to tick feeding and injection of aGal (Galα1-3Galβ1-4GlcNAc) conjugated to human serum albumin or mouse serum albumin (aGal-HSA or aGal-MSA) by increasing total IgE and aGal-specific IgE levels compared to those in C57BL/6 control mice. All of the treatments of aGT-KO mice involving the feeding of partially fed and unfed ticks functioned as sensitizers that increased the levels of specific IgE against aGal, with large individual variations. The data in this study do not support the "transmission" component of AGS, although they confirmed that aGT-KO mice can be used as a model for RMA studies.

Molecular Characterization and Gene Expression Analysis of Aquaporin in Haemaphysalis qinghaiensis

Aquaporins (AQPs) are important functional proteins and are widely present in the cell membrane of almost all organisms, mediating transmembrane transport of liquid and other solutes. Much is known about the molecular characterization of AQPs in other tick species; however, nothing is known about them in Haemaphysalis qinghaiensis. In this study, we first sequenced the transcript variants of AQPs in H. qinghaiensis (HqAQPs), analyzed the biological structure features of AQPs, and investigated the pattern of gene expression of the AQP gene of H. qinghaiensis in different tick tissues and stages to predict their biological functions. In conclusion, four AQP transcript variants (i.e., HqAQP1-1, HqAQP1-2, HqAQP1-3, and HqAQP1-4) of H. qinghaiensis were found, and the sequences were comparable with its orthologs from the reported tick species. Gene expression of AQPs in different tick tissues and stages showed the higher expression level in salivary glands and gut of adult female, as well as in the female and nymph than in Malpighian tubules, ovary, male, larvae, and egg. Further studies will be performed to evaluate the function of HqAQPs against H. qinghaiensis infestation on animals.

Responses of ticks to immersion in hot bathing water: Effect of surface type, water temperature, and soap on tick motor control

Preventing bites from undetected ticks through bathing practices would benefit public health, but the effects of these practices have been researched minimally. We immersed nymphal and adult hard ticks of species common in the eastern United States in tap water, using temperatures and durations that are realistic for human hot bathing. The effect of (a) different skin-equivalent surfaces (silicone and pig skin), and (b) water temperature was tested on Amblyomma americanum, Dermacentor variabilis and Ixodes scapularis nymphs. Overall, the type of surface had a much larger effect on the nymphs’ tendency to stay in contact with the surface than water temperature did. Most nymphs that separated from the surface did so within the first 10 s of immersion, with the majority losing contact due to the formation of an air bubble between their ventral side and the test surface. In addition, adult Ixodes scapularis were tested for the effect of immersion time, temperature, and soap on tick responsiveness. Some individual adults moved abnormally or stopped moving as a result of longer or hotter immersion, but soap had little effect on responsiveness. Taken together, our results suggest that the surface plays a role in ticks’ tendency to stay in contact; the use of different bath additives warrants further research. While water temperature did not have a significant short-term effect on tick separation, ticks that have not attached by their mouth parts may be rendered unresponsive and eventually lose contact with a person’s skin in a hot bath. It should be noted that our research did not consider potential temperature effects on the pathogens themselves, as previous research suggests that some tickborne pathogens may become less hazardous even if the tick harboring them survives hot-water exposures and later bites the bather after remaining undetected.

Characterization of tick salivary gland and saliva alphagalactome reveals candidate alpha-gal syndrome disease biomarkers

BACKGROUND

Ticks are obligate hematophagous arthropods that synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal) associated with the alpha-gal syndrome (AGS) or allergy to mammalian meat consumption.

RESEARCH DESIGN AND METHODS

In this study, we used a proteomics approach to characterize tick proteins in salivary glands (sialome SG), secreted saliva (sialome SA) and with α-Gal modification (alphagalactome SG and SA) in model tick species associated with the AGS in the United States (Amblyomma americanum) and Australia (Ixodes holocyclus). Selected proteins reactive to sera (IgE) from patients with AGS were identified to advance in the identification of possible proteins associated with the AGS. For comparative analysis, the α-Gal content was measured in various tick species.

RESULTS

The results confirmed that ticks produce proteins with α-Gal modifications and secreted into saliva during feeding. Proteins identified in tick alphagalactome SA by sera from patients with severe AGS symptomatology may constitute candidate disease biomarkers.

CONCLUSIONS

The results support the presence tick-derived proteins with α-Gal modifications in the saliva with potential implications in AGS and other disorders and protective capacity against tick infestations and pathogen infection. Future research should focus on the characterization of the function of tick glycoproteins with α-Gal in tick biology and AGS.

Alpha-Gal Syndrome: Involvement of Amblyomma americanum α-D-Galactosidase and β-1,4 Galactosyltransferase Enzymes in α-Gal Metabolism

Alpha-Gal Syndrome (AGS) is an IgE-mediated delayed-type hypersensitivity reaction to the oligosaccharide galactose-α-1, 3-galactose (α-gal) injected into humans from the lone-star tick (Amblyomma americanum) bite. Indeed, α-gal is discovered in salivary glands of lone-star tick; however, the tick's specific intrinsic factors involved in endogenous α-gal production and presentation to host during hematophagy are poorly understood. This study aimed to investigate the functional role of two tick enzymes, α-D-galactosidase (ADGal) and β-1,4 galactosyltransferases (β-1,4GalT), in endogenous α-gal production, carbohydrate metabolism, and N-glycan profile in lone-star tick. The ADGal enzyme cleaves terminal α-galactose moieties from glycoproteins and glycolipids, whereas β-1,4GalT transfers α-galactose to a β1,4 terminal linkage acceptor sugars-GlcNAc, Glc, and Xyl-in various processes of glycoconjugate synthesis. An RNA interference approach was utilized to silence ADGal and β-1,4GalT in Am. americanum to examine their function in α-gal metabolism in tick and AGS onset. Silencing of ADGal led to the significant downregulation of genes involved in galactose metabolism and transport in Am. americanum. Immunoblot and N-glycan analysis of the Am. americanum salivary glands showed a significant reduction in α-gal levels in silenced tissues. However, there was no significant difference in the level of α-gal in β-1,4GalT-silenced tick salivary glands. A basophil-activation test showed a decrease in the frequency of activated basophil by ADGal-silenced salivary glands. These results provide an insight into the roles of ADGal and β-1,4GalT in α-gal production and presentation in ticks and the probable involvement in the onset of AGS.