Alpha-gal syndrome: when treatment of hypovolemic shock can lead to anaphylaxis.

Delayed anaphylaxis after ingestion of red meat because of galactose-alpha-1,3-galactose (alpha-gal) syndrome has increased in recent years. The mechanism involves an immunoglobulin E reaction to alpha-gal, a molecule found in mammalian meat, dairy products, medications and excipients containing mammalian-derived components, and tick salivary glycans. Sensitization occurs due to the bite of a lone star tick and the transmission of alpha-gal molecules into person's bloodstream. We describe a case of alpha-gal syndrome with severe food, drug, and perioperative allergy in which anaphylaxis with hypovolemic shock occurred immediately after an emergency surgical procedure, when a gelatin-containing drug was injected. This case study confirms that the clinical manifestations of alpha-gal syndrome could be different depending on the route of administration, with immediate reactions if an alpha-gal-containing drug is injected and delayed type allergic manifestations occurring several hours after oral intake. The purpose of this report is to highlight the importance of risk communication in case of exposure to medical products and surgical procedures of patients with alpha-gal syndrome and to encourage drug manufacturers to indicate clearly the origin of excipients in product literature.

Immunoglobulin E Sensitization to Mammalian Oligosaccharide Galactose-α-1,3 (α-Gal) Is Associated With Noncalcified Plaque, Obstructive Coronary Artery Disease, and ST-Segment-Elevated Myocardial Infarction.

BACKGROUND: Treating known risk factors for coronary artery disease (CAD) has substantially reduced CAD morbidity and mortality. However, a significant burden of CAD remains unexplained. Immunoglobulin E sensitization to mammalian oligosaccharide galactose-α-1,3-galactose (α-Gal) was recently associated with CAD in a small observational study. We sought to confirm that α-Gal sensitization is associated with CAD burden, in particular noncalcified plaque. Additionally, we sort to assess whether that α-Gal sensitization is associated with ST-segment-elevated myocardial infarction (STEMI) Methods: We performed a cross-sectional analysis of participants enrolled in the BioHEART cohort study. We measured α-Gal specific-immunoglobulin E antibodies in serum of 1056 patients referred for CT coronary angiography for suspected CAD and 100 selected patients presenting with STEMI, enriched for patients without standard modifiable risk factors. CT coronary angiograms were assessed using coronary artery calcium scores and segmental plaque scores. RESULTS: α-Gal sensitization was associated with presence of noncalcified plaque (odds ratio, 1.62 [95% CI, 1.04-2.53], P=0.03) and obstructive CAD (odds ratio, 2.05 [95% CI, 1.29-3.25], P=0.002), independent of age, sex, and traditional risk factors. The α-Gal sensitization rate was 12.8-fold higher in patients with STEMI compared with matched healthy controls and 2.2-fold higher in the patients with STEMI compared with matched stable CAD patients (17% versus 1.3%, P=0.01 and 20% versus 9%, P=0.03, respectively). CONCLUSIONS: α-Gal sensitization is independently associated with noncalcified plaque burden and obstructive CAD and occurs at higher frequency in patients with STEMI than those with stable or no CAD. These findings may have implications for individuals exposed to ticks, as well as public health policy. Registration: URL: https://www.anzctr.org.au; Unique identifier: ACTRN12618001322224.

Therapeutic plasma exchange for peripheral neuropathy associated with trisulfated heparan disaccharide IgM antibodies: A case series of 17 patients.

BACKGROUND: Small fiber neuropathy (SFN) can be associated with autoantibodies, including those of IgM class with specificity for the trisulfated heparan disaccharide (TS-HDS) antigen. We hypothesized that, as an IgM autoantibody-mediated disorder, TS-HDS-associated SFN symptoms may be reduced with therapeutic plasma exchange (TPE). STUDY METHODS: This was an observational analysis of all patients referred for TPE from 2018 to 2020 following laboratory confirmation of SFN with TS-HDS autoantibodies; a loading course of 3 to 5 procedures over 2 weeks was completed, with some patients returning for monthly procedures. The following data were collected: demographics, symptoms and duration, TS-HDS levels, skin biopsy results, reported responses to TPE, and TPE-associated adverse events. RESULTS: Of the 17 subjects, 12 (71%) were female and the mean age was 57.5 years (range 27-94). The most common reported symptom was lower extremity paresthesia (88% of subjects). The mean number of TPE procedures completed per subject was 9 (range 3-18), with 71% (12/17) reporting symptomatic improvement or slowed disease progression. About 15% of procedures were associated with an adverse event, with vasovagal reactions being the most common; 53% of patients had at least one adverse event. CONCLUSIONS: Given a reported symptomatic response rate of more than 70%, TPE may be a treatment option for individuals with autoimmune-mediated SFN associated with increased titers of TS-HDS IgM autoantibodies. Since TPE-associated adverse events appear common in this population, close monitoring during procedures is warranted.

Immunogenicity Evaluation of N-Glycans Recognized by HIV Broadly Neutralizing Antibodies.

While the improved treatment of human immunodeficiency virus type 1 (HIV-1) infection is available, the development of an effective and safe prophylactic vaccine against HIV-1 is still an unrealized goal. Encouragingly, the discovery of broadly neutralizing antibodies (bNAbs) from HIV-1 positive patients that are capable of neutralizing a broad spectrum of HIV-1 isolates of various clades has accelerated the progress of vaccine development in the past few years. Some of these bNAbs recognize the N-glycans on the viral surface gp120 glycoprotein. We have been interested in using the glycan epitopes recognized by bNAbs for the development of vaccines to elicit bNAb-like antibodies with broadly neutralizing activities. Toward this goal, we have identified novel hybrid-type structures with subnanomolar avidity toward several bNAbs including PG16, PGT121, PGT128-3C, 2G12, VRC13, VRC-PG05, VRC26.25, VRC26.09, PGDM1400, 35O22, and 10-1074. Here, we report the immunogenicity evaluation of a novel hybrid glycan conjugated to carrier DTCRM197, a nontoxic mutant of the diphtheria toxin, for immunization in mice. Our results indicated that the IgG response was mainly against the chitobiose motif with nonspecific binding to a panel of N-glycans with reducing end GlcNAc-GlcNAc (chitobiose) printed on the glass slides. However, the IgM response was mainly toward the reducing end GlcNAc moiety. We further used the glycoconjugates of Man3GlcNAc2, Man5GlcNAc2, and Man9GlcNAc2 glycans for immunization, and a similar specificity pattern was observed. These findings suggest that the immunogenicity of chitobiose may interfere with the outcome of N-glycan-based vaccines, and modification may be necessary to increase the immunogenicity of the entire N-glycan epitope.

Immunoglobulin M and Immunoglobulin G Subclass Distribution of Anti-galactose-Alpha-1,3-Galactose and Anti-N-Glycolylneuraminic Acid Antibodies in Healthy Korean Adults.

BACKGROUND: Human preformed antibodies (Abs), anti-galactose-alpha-1,3-galactose (Gal) and anti-N-glycolylneuraminic acid (Neu5Gc), can react with porcine antigens of wild-type pigs. To provide basic population data of the Abs for potential application in clinical xenotransplantation, we developed enzyme-linked immunosorbent assay methods and investigated the serum titers of anti-Gal and anti-Neu5Gc Abs, including immunoglobulin (Ig) M and IgG along with its subclasses, in humans. METHODS: Anti-Gal and anti-Neu5Gc Abs serum titers were measured in 380 healthy Korean adults using the in-house enzyme-linked immunosorbent assays. The frequency and median values of anti-Gal and anti-Neu5Gc were measured, and their class and subclass distribution were evaluated. RESULTS: The detection frequencies of anti-Gal were 99.2%, 95.0%, 23.2%, 94.5%, 12.4%, and 3.4% for IgM, IgG, IgG1, IgG2, IgG3, and IgG4, respectively. The detection frequencies of anti-Neu5Gc Abs were 87.4%, 96.6%, 1.6%, 46.3%, 0.0%, and 0.0% for IgM, IgG, IgG1, IgG2, IgG3, and IgG4, respectively. The median values of anti-Gal IgM (1001.6 ng/mL) and IgG (1198.3 ng/mL) were significantly higher than those of anti-Neu5Gc Abs (IgM, 328.4 ng/mL; IgG, 194.7 ng/mL; P < .001). IgG2 titers of both anti-Gal and anti-Neu5Gc Abs correlated better with the IgG class than the titers of other IgG subclasses. CONCLUSIONS: The titers of anti-Gal Abs were higher than those of anti-Neu5Gc Abs. IgG2 was the main IgG subclass in both anti-Gal and anti-Neu5Gc Abs. Variation in the titers of anti-Gal or anti-Neu5Gc Abs may partly explain the biological and immunologic changes that occur in recipients of xenotransplants.

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

BACKGROUND: IgE to α-Gal is a cause of mammalian meat allergy and has been linked to tick bites in North America, Australia, and Eurasia. Reports from the developing world indicate that α-Gal sensitization is prevalent but has been little investigated. OBJECTIVE: We sought evidence for the cause(s) of α-Gal sensitization and lack of reported meat allergy among children in less developed settings in Ecuador and Kenya. METHODS: IgE to α-Gal and total IgE were assessed in children from Ecuador (n = 599) and Kenya (n = 254) and compared with children with (n = 42) and without known (n = 63) mammalian meat allergy from the southeastern United States. Information on diet, potential risk factors, and helminth infections was available for children from Ecuador. IgG4 to α-Gal and antibodies to regionally representative parasites were assessed in a subset of children. RESULTS: In Ecuador (32%) and Kenya (54%), α-Gal specific IgE was prevalent, but levels were lower than in children with meat allergy from the United States. Sensitization was associated with rural living, antibody markers of Ascaris exposure, and total IgE, but not active infections with Ascaris or Trichuris species. In Ecuador, 87.5% reported consuming beef at least once per week, including 83.9% of those who had α-Gal specific IgE. Levels of α-Gal specific IgG4 were not high in Ecuador, but were greater than in children from the United States. CONCLUSIONS: These results suggest that in areas of the developing world with endemic parasitism, α-Gal sensitization is (1) common, (2) associated with Ascaris exposure, and (3) distinguished by a low percentage of specific/total IgE compared with individuals with meat allergy in the United States.

The antibody response to the glycan α-Gal correlates with COVID-19 disease symptoms.

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected millions of people worldwide. Characterization of the immunological mechanisms involved in disease symptomatology and protective response is important to progress in disease control and prevention. Humans evolved by losing the capacity to synthesize the glycan Galα1-3Galß1-(3)4GlcNAc-R (α-Gal), which resulted in the development of a protective response against pathogenic viruses and other microorganisms containing this modification on membrane proteins mediated by anti-α-Gal immunoglobulin M (IgM)/IgG antibodies produced in response to bacterial microbiota. In addition to anti-α-Gal antibody-mediated pathogen opsonization, this glycan induces various immune mechanisms that have shown protection in animal models against infectious diseases without inflammatory responses. In this study, we hypothesized that the immune response to α-Gal may contribute to the control of COVID-19. To address this hypothesis, we characterized the antibody response to α-Gal in patients at different stages of COVID-19 and in comparison with healthy control individuals. The results showed that while the inflammatory response and the anti-SARS-CoV-2 (Spike) IgG antibody titers increased, reduction in anti-α-Gal IgE, IgM, and IgG antibody titers and alteration of anti-α-Gal antibody isotype composition correlated with COVID-19 severity. The results suggested that the inhibition of the α-Gal-induced immune response may translate into more aggressive viremia and severe disease inflammatory symptoms. These results support the proposal of developing interventions such as probiotics based on commensal bacteria with α-Gal epitopes to modify the microbiota and increase α-Gal-induced protective immune response and reduce severity of COVID-19.

Association between lone star tick bites and increased alpha-gal sensitization: evidence from a prospective cohort of outdoor workers.

BACKGROUND: Alpha-gal is an oligosaccharide implicated in delayed anaphylaxis following red meat consumption. Exposure to tick bites has been correlated with development of an allergic response to alpha-gal. However, evidence prospectively linking exposure to a single tick species and an immune response to alpha-gal is lacking. METHODS: We used serum samples from a prior study cohort of outdoor workers in North Carolina, USA, with high exposure to the lone star tick, Amblyomma americanum, to prospectively evaluate the relationship between tick bites and anti-alpha-gal IgE antibodies. RESULTS: Individuals who reported exposure to one or more tick bites were significantly more likely to have a positive change in anti-alpha-gal IgE compared to individuals with no reported tick bites. This relationship was not dependent on time. A trend toward increasing number of tick bites and increased anti-alpha-gal IgE levels was observed but not statistically significant. CONCLUSION: To our knowledge, this is the first study to prospectively link documented exposure to A. americanum bites and increased sensitization to alpha-gal in a cohort of outdoor workers. Our results support the role of A. americanum as likely agents for eliciting an allergic response to red meat, and highlight the importance of preventing tick bites.

Human Natural Antibodies Recognizing Glycan Galß1-3GlcNAc (LeC).

The level of human natural antibodies of immunoglobulin M isotype against LeC in patients with breast cancer is lower than in healthy women. The epitope specificity of these antibodies has been characterized using a printed glycan array and enzyme-linked immunosorbent assay (ELISA), the antibodies being isolated from donors' blood using LeC-Sepharose (LeC is Galß1-3GlcNAcß). The isolated antibodies recognize the disaccharide but do not bind to glycans terminated with LeC, which implies the impossibility of binding to regular glycoproteins of non-malignant cells. The avidity (as dissociation constant value) of antibodies probed with a multivalent disaccharide is 10-9 M; the nanomolar level indicates that the concentration is sufficient for physiological binding to the cognate antigen. Testing of several breast cancer cell lines showed the strongest binding to ZR 75-1. Interestingly, only 7% of the cells were positive in a monolayer with a low density, increasing up to 96% at highest density. The enhanced interaction (instead of the expected inhibition) of antibodies with ZR 75-1 cells in the presence of Galß1-3GlcNAcß disaccharide, indicates that the target epitope of anti-LeC antibodies is a molecular pattern with a carbohydrate constituent rather than a glycan.

Functional Dyspepsia and Food: Immune Overlap with Food Sensitivity Disorders.

PURPOSE OF REVIEW: Functional dyspepsia (FD) is a chronic functional gastrointestinal disorder characterised by upper gastrointestinal symptoms. Here, we aimed to examine the evidence for immune responses to food in FD and overlap with food hypersensitivity conditions. RECENT FINDINGS: A feature of FD in a subset of patients is an increase in mucosal eosinophils, mast cells, intraepithelial cytotoxic T cells and systemic gut-homing T cells in the duodenum, suggesting that immune dysfunction is characteristic of this disease. Rates of self-reported non-celiac wheat/gluten sensitivity (NCW/GS) are higher in FD patients. FD patients commonly report worsening symptoms following consumption of wheat, fermentable oligosaccharides, disaccharides, monosaccharides, or polyols (FODMAPs), high-fat foods and spicy foods containing capsaicin. Particularly, wheat proteins and fructan in wheat may drive symptoms. Immune mechanisms that drive responses to food in FD are still poorly characterised but share key effector cells to common food hypersensitivities including non-IgE-mediated food allergy and eosinophilic oesophagitis.

Complement activation by human IgG antibodies to galactose-α-1,3-galactose.

Some human antibodies may paradoxically inhibit complement activation on bacteria and enhance pathogen survival in humans. This property was also claimed for IgG antibodies reacting with terminal galactose-α-1,3-galactose (Galα3Gal; IgG anti-αGal), a naturally occurring and abundant antibody in human plasma that targets numerous different pathogens. To reinvestigate these effects, we used IgG anti-αGal affinity isolated from a pool of normal human IgG and human hypogammaglobulinaemia serum as a complement source. Flow cytometry was performed to examine antibody binding and complement deposition on pig erythrocytes, Escherichia coli O86 and Streptococcus pneumoniae serotype 9V. Specific nanobodies were used to block the effect of single complement factors and to delineate the complement pathways involved. IgG anti-αGal was capable of activating the classical complement pathway on all the tested target cells. The degree of activation was exponentially related to the density of bound antibody on E. coli O86 and pig erythrocytes, but more linearly on S. pneumoniae 9V. The alternative pathway of complement amplified complement deposition. Deposited C3 fragments covered the activating IgG anti-αGal, obstructing its detection and highlighting this as a likely general caveat in studies of antibody density and complement deposition. The inherent capacity for complement activation by the purified carbohydrate reactive IgG anti-αGal was similar to that of normal human IgG. We propose that the previously reported complement inhibition by IgG anti-αGal relates to suboptimal assay configurations, in contrast to the complement activating property of the antibodies demonstrated in this paper.

Alpha-gal syndrome: An emerging cause of food and drug allergy.

Alpha-gal syndrome (AGS) describes a wide spectrum of hypersensitivity reactions mediated by specific IgE to the α-gal epitope (galactose-α-1,3-galactose) ubiquitously expressed on glycolipids/glycoproteins of most mammals. This fascinating new entity has completely changed the paradigms of allergy as allergic response is directed against an oligosaccharide and the reactions can be both immediate and delayed. They appear to be stimulated only by tick bites which induce production of α-gal specific IgE antibodies that lead to (at times fatal) hypersensitivity response. AGS is completely different to previously described anaphylaxis to tick saliva. It provides unique insight into the interplay between different arms of the immune system and the role of ectoparasites in the development of anaphylaxis to food and medication in patients at risk of tick bites including travellers. This review summarises recent advances in our understanding of its clinical presentation, pathomechanism and role of various tick species in the development of AGS.

Red Meat Allergies after Lone Star Tick (Amblyomma americanum) Bites.

Red meat allergies have followed tick bites on every continent except Antarctica. The sensitizing antigen is galactose-α-1,3-galactose (α-gal), an oligosaccharide constituent of nonprimate blood and meat, acquired by ticks during animal bloodfeeding. Because red meat allergy after tick bites is a worldwide phenomenon, the objectives of this review were to describe the global epidemiology of red meat allergy after tick bites and its immunological mechanisms; to identify the human risk factors for red meat allergy after tick bites; to identify the most common tick vectors of red meat allergy worldwide; to describe the clinical manifestations, diagnostic confirmation, and management of patients with red meat allergy after tick bites; and to recommend strategies for the prevention of tick bites. To meet these objectives, Internet search engines were queried with keywords to select scientific articles for review. The keywords included ticks, tick bites, allergy, anaphylaxis, and meat allergy. The study period was defined as 1980-2019. The major risk factors for red meat allergy after tick bites included male sex, non-B blood type, systemic mastocytosis, a bioprosthetic (bovine or porcine) heart valve, and preexisting allergies to gelatin or animal dander. Following confirmation by challenge testing, patients with red meat allergies should avoid red meats, foods containing gelatin, and intravenous immunotherapy with monoclonal antibodies such as cetuximab and infliximab produced in SP2/0 mouse cell lines. Red meat allergy after tick bites represents an emerging threat from tick bites in addition to infectious diseases.

A fentanyl vaccine constructed upon opsonizing antibodies specific for the Galα1-3Gal epitope.

A double conjugation strategy was implemented to produce an anti-fentanyl vaccine, which was predicated upon preformed-antibody-assisted antigen presentation. The new vaccine was found to reduce the psychoactive effects of fentanyl without the addition of the immunostimulant CpG oligodeoxynucleotide.

Abundant human anti-Galα3Gal antibodies display broad pathogen reactivity.

Antibodies of the IgG class to terminal Galα3Gal (IgG anti-αGal) is abundant in human plasma and are reported to bind most sepsis-causing Gram-negative bacteria. However, these seminal findings, made more than two decades ago, have not been reexamined. Our aim was to assess IgG anti-αGal´s pathogen reactivity. We affinity purified IgG anti-αGal from a therapeutic grade normal human IgG pool applying two rounds of positive selection with Galα3Gal-coupled beads and included removal of column matrix reactive antibodies. The purified antibodies were rigorously characterized in terms of specificity and purity in various solid-phase immunoassays. We used flow cytometry to study reactivity against 100 consecutive clinical isolates diagnosed as cause of sepsis in humans. We found that the purified IgG anti-αGal displays high specificity for Galα3Gal. Also, IgG anti-αGal at 5 mg/L bound 56 out of 100 pathogens with predilection for Gram-positive bacteria binding 39 out of 52 strains. We confirm that although IgG anti-αGal comprise a small fraction of the human antibody pool (~0.1%), these antibodies targets an impressively large part of pathogens causing invasive disease.