Significance of the evolutionary α1,3-galactosyltransferase (GGTA1) gene inactivation in preventing extinction of apes and old world monkeys

Alpha-Gal, epitope responsible for allergy to red meat, in the Mediterranean tick Hyalomma lusitanicum

Alpha-Gal/α-Gal is an oligosaccharide produced by non-primate mammals. Humans have developed an immune response mediated by anti-α-Gal antibodies that can trigger an allergic reaction and cause anaphylaxis. In recent years, cases of patients with delayed allergic reaction to mammalian meat have been reported worldwide. In Spain, these cases have been related to the species Ixodes ricinus L. (Ixodida: Ixodidae), whose distribution is located in the north of the country. In this work, the presence of α-Gal in water-soluble extracts from samples of salivary glands and digestive tracts of Hyalomma lusitanicum Koch (Ixodida: Ixodidae) both engorged and collected from vegetation were studied. The presence of that epitope was confirmed by the presence of reactive proteins of >250 kDa in both samples. The highest concentrations of α-Gal were detected in salivary glands. Neither sex nor diet influenced the concentration of α-Gal, which seems to indicate its endogenous production and its possible inoculation to the host during tick feeding.

The Acari Hypothesis, IV: revisiting the role of hygiene in allergy

Allergy and its manifestations were first appreciated in the 1870 s. Today, the mechanism by which specific substances elicit allergic reactions remains poorly understood. This is problematic from a healthcare perspective because the prevalence of allergic disease and its societal costs are substantial. Regarding mechanistic understanding of allergy, a new proposal, The Acari Hypothesis, has been forwarded. The Hypothesis, borne from consideration of alpha-gal syndrome, postulates that acarians, i.e., mites and ticks, are operative agents of allergy. By way of their pathogenic payloads and salivary pattern recognition receptor(s), acarians potentiate in human hosts the generation of IgE against acarian dietary elements. Those elements account for most, if not all, known human allergens. Inasmuch as acarian-human interactions occur on human epithelial surfaces, it is to be expected factors that influence the presence and/or operation of acarians on those surfaces influence the expression of allergic diseases. In this report, it is proposed that two adaptations of catarrhine primates, i.e., Old World monkeys, apes and humans, evolved to deter acarian species: firstly, the expansion of eccrine glands across the entirety of body surface area, and, secondly, the secretion of sweat by those glands. Contemporary hygienic practices that reduce and/or disrupt the operation of eccrine glands are likely responsible for the increase in allergic disease seen today.

IgE and anaphylaxis specific to the carbohydrate alpha-gal depend on IL-4

BACKGROUND

Alpha-gal (Galα1-3Galβ1-4GlcNAc) is a carbohydrate with the potential to elicit fatal allergic reactions to mammalian meat and drugs of mammalian origin. This type of allergy is induced by tick bites, and therapeutic options for this skin-driven food allergy are limited to the avoidance of the allergen and treatment of symptoms. Thus, a better understanding of the immune mechanisms resulting in sensitization through the skin is crucial, especially in the case of a carbohydrate allergen for which underlying immune responses are poorly understood.

OBJECTIVE

We aimed to establish a mouse model of alpha-gal allergy for in-depth immunologic analyses.

METHODS

Alpha-galactosyltransferase 1-deficient mice devoid of alpha-gal glycosylations were sensitized with the alpha-gal-carrying self-protein mouse serum albumin by repetitive intracutaneous injections in combination with the adjuvant aluminum hydroxide. The role of basophils and IL-4 in sensitization was investigated by antibody-mediated depletion.

RESULTS

Alpha-gal-sensitized mice displayed increased levels of alpha-gal-specific IgE and IgG1 and developed systemic anaphylaxis on challenge with both alpha-gal-containing glycoproteins and glycolipids. In accordance with alpha-gal-allergic patients, we detected elevated numbers of basophils at the site of sensitization as well as increased numbers of alpha-gal-specific B cells, germinal center B cells, and B cells of IgE and IgG1 isotypes in skin-draining lymph nodes. By depleting IL-4 during sensitization, we demonstrated for the first time that sensitization and elicitation of allergy to alpha-gal and correspondingly to a carbohydrate allergen is dependent on IL-4.

CONCLUSION

These findings establish IL-4 as a potential target to interfere with alpha-gal allergy elicited by tick bites.

Influence of microbiota-driven natural antibodies on dengue transmission

Dengue has had a significant global health impact, with a dramatic increase in incidence over the past 50 years, affecting more than 100 countries. The absence of a specific treatment or widely applicable vaccine emphasizes the urgent need for innovative strategies. This perspective reevaluates current evidence supporting the concept of dual protection against the dengue virus (DENV) through natural antibodies (NAbs), particularly anti-α-Gal antibodies induced by the host's gut microbiome (GM). These anti-α-Gal antibodies serve a dual purpose. Firstly, they can directly identify DENV, as mosquito-derived viral particles have been observed to carry α-Gal, thereby providing a safeguard against human infections. Secondly, they possess the potential to impede virus development in the vector by interacting with the vector's microbiome and triggering infection-refractory states. The intricate interplay between human GM and NAbs on one side and DENV and vector microbiome on the other suggests a novel approach, using NAbs to directly target DENV and simultaneously disrupt vector microbiome to decrease pathogen transmission and vector competence, thereby blocking DENV transmission cycles.

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.

Validation of an anti-α-Gal IgE fluoroenzyme-immunoassay for the screening of patients at risk of severe anaphylaxis to cetuximab

BACKGROUND

The link between immediate hypersensitivity reactions (HSR) following the first cetuximab infusion and the IgE sensitization against anti-galactose-α-1,3-galactose (α-Gal) is now well-established. An automated Fluoroenzyme-Immunoassay (FEIA) is available and may facilitate the screening of patients with anti-α-Gal IgE before treatment.

METHODS

This study aimed to evaluate its performances as compared to a previously validated anti-cetuximab IgE ELISA, using 185 samples from two previously studied cohorts.

RESULTS

Despite 21.1% of discrepancies between the two techniques, FEIA discriminated better positive patients and similarly negative ones with a ≥ 0.525 kU_A/L threshold. Sensitivity was 87.5% for both tests, specificity was better for FEIA (96.3% vs ELISA: 82.1%). FEIA had a higher positive likelihood ratio (23.9 vs ELISA: 4.89) and a similar negative likelihood ratio (0.13 vs ELISA: 0.15). In our population, the risk of severe HSR following a positive test was higher with FEIA (56.7% vs ELISA: 19.6%) and similar following a negative test (0.7% vs ELISA: 0.8%).

CONCLUSION

Although the predictive value of the IgE screening before cetuximab infusion remains discussed, this automated commercial test can identify high-risk patients and is suitable for routine use in laboratories. It could help avoiding cetuximab-induced HSR by a systematic anti-α-Gal IgE screening before treatment.

Emerging Nano-/Biotechnology Drives Oncolytic Virus-Activated and Combined Cancer Immunotherapy

Oncolytic viruses (OVs) as one promising antitumor methods have made important contributions to tumor immunotherapy, which arouse increasing attention. They provide the dual mechanisms including direct killing effect toward tumor cells and immune activation for elevating antitumor responses, which have been proved in many preclinical studies. Especially, natural or genetically modified viruses as clinical immune preparations have emerged as a new promising approach objective to oncology treatment. The approval of talimogene laherparepvec (T-VEC) by the U.S. Food and Drug Administration (FDA) for the therapy of advanced melanoma could be considered as a milestone achievement in the clinical translation of OV. In this review, we first discussed the antitumor mechanisms of OVs with an emphasis on targeting, replication, and propagation. We further outlined the state of the art of current OVs in tumor and underlined the activated biological effects especially including immunity. More significantly, the enhanced immune responses based on OVs were systematically discussed from different perspectives such as combination with immunotherapy, genetic engineering of OVs, integration with nanobiotechnology or nanoparticles, and antiviral response counteraction, where their principles were shed light on. The development of OVs in the clinics was also highlighted to analyze the actuality and concerns of different OV applications in clinical trials. At last, the future perspectives and challenges of OVs as an already widely accepted treatment means were discussed. This review will provide a systematic review and deep insight into OV development and also offer new opportunities and guidance pathways to drive the further clinical translation.

Current and Future Strategies for the Diagnosis and Treatment of the Alpha-Gal Syndrome (AGS)

The α-Gal syndrome (AGS) is a pathognomonic immunoglobulin E (IgE)-mediated delayed anaphylaxis in foods containing the oligosaccharide galactose-α-1,3-galactose (α-Gal) such as mammalian meat or dairy products. Clinical presentation of AGS can also comprise immediate hypersensitivity due to anticancer therapy, gelatin-containing vaccines or mammalian serum-based antivenom. The IgE initial sensitization is caused by hard-bodied tick bites and symptomatic individuals typically develop delayed pruritus, urticaria, angioedema, anaphylaxis, malaise or gut-related symptoms. Due to inapparent presentation, delayed reactions and a wide variety of patients´ clinical history, the AGS diagnosis and treatment remain challenging. This review covers not only current diagnostic methods used for AGS such as the skin prick test (SPT), the oral food challenge (OFC), anti-α-Gal IgE levels measurement and the basophil activation test (BAT), but also potentially relevant next-generation diagnostic tools like the mast cell activation test (MAT), the histamine-release (HR) assay, omics technologies and model-based reasoning (MBR). Moreover, it focuses on the therapeutical medical and non-medical methods available and current research methods that are being applied in order to elucidate the molecular, physiological and immune mechanisms underlying this allergic disorder. Lastly, future treatment and preventive tools are also discussed, being of utmost importance for the identification of tick salivary molecules, with or without α-Gal modifications, that trigger IgE sensitivity as they could be the key for further vaccine development. Bearing in mind climate change, the tick-host paradigm will shift towards an increasing number of AGS cases in new regions worldwide, which will pose new challenges for clinicians in the future.

Genetic and structural basis of the human anti-α-galactosyl antibody response

Humans lack the capacity to produce the Galα1-3Galβ1-4GlcNAc (α-gal) glycan, and produce anti-α-gal antibodies upon exposure to the carbohydrate on a diverse set of immunogens, including commensal gut bacteria, malaria parasites, cetuximab, and tick proteins. Here we use X-ray crystallographic analysis of antibodies from α-gal knockout mice and humans in complex with the glycan to reveal a common binding motif, centered on a germline-encoded tryptophan residue at Kabat position 33 (W33) of the complementarity-determining region of the variable heavy chain (CDRH1). Immunoglobulin sequencing of anti-α-gal B cells in healthy humans and tick-induced mammalian meat anaphylaxis patients revealed preferential use of heavy chain germline IGHV3-7, encoding W33, among an otherwise highly polyclonal antibody response. Antigen binding was critically dependent on the presence of the germline-encoded W33 residue for all of the analyzed antibodies; moreover, introduction of the W33 motif into naive IGHV3-23 antibody phage libraries enabled the rapid selection of α-gal binders. Our results outline structural and genetic factors that shape the human anti-α-galactosyl antibody response, and provide a framework for future therapeutics development.

Poly-L-Lysine-Based αGal-Glycoconjugates for Treating Anti-αGal IgE-Mediated Diseases

Anti-αGal IgE antibodies mediate a spreading allergic condition known as αGal-syndrome (AGS). People exposed to hard tick bites are sensitized to αGal, producing elevated levels of anti-αGal IgE, which are responsible for AGS. This work presents an immunotherapy based on polymeric αGal-glycoconjugates for potentially treating allergic disorders by selectively inhibiting anti-αGal IgE antibodies. We synthesized a set of αGal-glycoconjugates, based on poly-L-lysine of different degrees of polymerization (DP1000, DP600, and DP100), to specifically inhibit in vitro the anti-αGal IgE antibodies in the serum of αGal-sensitized patients (n=13). Moreover, an animal model for αGal sensitization in GalT-KO mice was developed by intradermal administration of hard tick' salivary gland extract, mimicking the sensitization mechanism postulated in humans. The in vitro exposure to all polymeric glycoconjugates (5-10-20-50-100 µg/mL) mainly inhibited anti-αGal IgE and IgM isotypes, with a lower inhibition effect on the IgA and IgG, respectively. We demonstrated a differential anti-αGal isotype inhibition as a function of the length of the poly-L-lysine and the number of αGal residues exposed in the glycoconjugates. These results defined a minimum of 27 αGal residues to inhibit most of the induced anti-αGal IgE in vitro. Furthermore, the αGal-glycoconjugate DP1000-RA0118 (10 mg/kg sc.) showed a high capacity to remove the anti-αGal IgE antibodies (≥75% on average) induced in GalT-KO mice, together with similar inhibition for circulating anti-αGal IgG and IgM. Our study suggests the potential clinical use of poly-L-lysine-based αGal-glycoconjugates for treating allergic disorders mediated by anti-αGal IgE antibodies.

Immunological Risk Assessment of Xenogeneic Dural Patch by Comparing with Raw Material via GTKO Mice

OBJECTIVE

In this study, α-Gal epitope-deficient (GGTA1 knockout (GTKO)) mice were used to assess the immunological risks of xenogeneic dural patch by comparing with raw material.

METHODS

The xenogeneic dural patch (T2) was prepared from bovine pericardium (T1, raw material) through decellularization and carboxymethyl chitosan (CMCS) coating. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the collagen fibers and surface microstructural changes in the T1 and T2 samples. The remnant α-Gal epitopes and DNA of implants were detected by standardized method. T1 and T2 were implanted subcutaneously into GTKO mice for 4 and 12 weeks, respectively, and the negative control group (Con) was only performed sham operation. The total serum antibody, anti-Gal antibody, and splenic lymphocyte subtypes were analyzed by ELISA or flow cytometry, and histological analysis of implant-tissue was performed by H&E and Masson stain.

RESULTS

TEM and Sirius red staining showed that the collagen fibers in the dural patch were closely arranged, and SEM showed that a loose three-dimensional structure was successfully constructed on the surface of the dural patch after CMCS coating. The remnant DNA in T2 was 24.64 ± 8.73 ng/mg (dry weight), and clearance of α-Gal epitope was up to 99.83% compared to T1. The significant increases in serum total IgM, anti-Gal IgG, and anti-Gal IgM at 4 weeks and the significant changes in anti-Gal IgG and spleen lymphocyte at 12 weeks were observed in the T1 group, but no significant change was observed in the T2 group, compared to the control group. Histological semiquantitative analysis showed severe cell and tissue responses at 4 weeks and a moderate response at 12 weeks in the T1 group, while a moderate response at 4 weeks and a slight response at 12 weeks in the T2 group.

CONCLUSIONS

The results demonstrated that the xenogeneic dural patch has a lower and acceptable immunological risk compared to the raw material and control, respectively. On the other hand, it was suggested that GTKO mice are useful experimental model for immunological risk assessment of animal tissue-derived biomaterials.

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.

Vaccinomics: a future avenue for vaccine development against emerging pathogens

INTRODUCTION

Vaccines are a major achievement in medical sciences, but the development of more effective vaccines against infectious diseases is essential for prevention and control of emerging pathogens worldwide. The application of omics technologies has advanced vaccinology through the characterization of host-vector-pathogen molecular interactions and the identification of candidate protective antigens. However, major challenges such as host immunity, pathogen and environmental factors, vaccine efficacy and safety need to be addressed. Vaccinomics provides a platform to address these challenges and improve vaccine efficacy and safety.

AREAS COVERED

In this review, we summarize current information on vaccinomics and propose quantum vaccinomics approaches to further advance vaccine development through the identification and combination of antigen protective epitopes, the immunological quantum. The COVID-19 pandemic caused by SARS-CoV-2 is an example of emerging infectious diseases with global impact on human health.

EXPERT OPINION

Vaccines are required for the effective and environmentally sustainable intervention for the control of emerging infectious diseases worldwide. Recent advances in vaccinomics provide a platform to address challenges in improving vaccine efficacy and implementation. As proposed here, quantum vaccinomics will contribute to vaccine development, efficacy, and safety by facilitating antigen combinations to target pathogen infection and transmission in emerging infectious diseases.

Kcnk3, Ggta1, and Gpr84 are involved in hyperbaric oxygenation preconditioning protection on cerebral ischemia-reperfusion injury

The present study aimed to explore the potential mechanism of the effect of hyperbaric oxygenation (HBO) preconditioning on cerebral ischemia and reperfusion injury (CIRI). GSE23160 dataset was used to identify differentially expressed genes (DEGs) from striatum between the middle cerebral artery occlusion (MCAO)/reperfusion and sham rats. The gene clusters with continuous increase and decrease were identified by soft clustering analysis in Mfuzz, and functional enrichment analysis of these genes was performed using clusterProfiler package. The intersection set of the genes with significantly altered expression at post-reperfusion 2, 8, and 24 h were screened in comparison to 0 h (sham group), and the expression of these genes was detected in the MCAO/reperfusion model and HBO preconditioning groups by real-time PCR (RT-PCR) and western blotting. A total of 41 upregulated DEGs, and 7 downregulated DEGs were detected, among which the expression of Gpr84 and Ggta1 was significantly upregulated at each reperfusion phase as compared to the sham group, while the expression of Kcnk3 was significantly downregulated except in the postreperfusion 8 h in the striatum group. RT-PCR and western blotting analyses showed that the expression of Ggta1, Gpr84, and Kcnk3 genes between the MCAO/reperfusion and sham rats were consistent with the bioinformatics analysis. In addition, the HBO preconditioning reduced the expression of Ggta1 and Gpr84 and increased the expression of Kcnk3 in MCAO/reperfusion rats. Kcnk3, Ggta1, and Gpr84 may play a major role in HBO-mediated protection of the brain against CIRI.

Carbohydrate epitopes currently recognized as targets for IgE antibodies

Until recently, glycan epitopes have not been documented by the WHO/IUIS Allergen Nomenclature Sub-Committee. This was in part due to scarce or incomplete information on these oligosaccharides, but also due to the widely held opinion that IgE to these epitopes had little or no relevance to allergic symptoms. Most IgE-binding glycans recognized up to 2008 were considered to be "classical" cross-reactive carbohydrate determinants (CCD) that occur in insects, some helminths and throughout the plant kingdom. Since 2008, the prevailing opinion on lack of clinical relevance of IgE-binding glycans has been subject to a reevaluation. This was because IgE specific for the mammalian disaccharide galactose-alpha-1,3-galactose (alpha-gal) was identified as a cause of delayed anaphylaxis to mammalian meat in the United States, an observation that has been confirmed by allergists in many parts of the world. Several experimental studies have shown that oligosaccharides with one or more terminal alpha-gal epitopes can be attached as a hapten to many different mammalian proteins or lipids. The classical CCDs also behave like haptens since they can be expressed on proteins from multiple species. This is the explanation for extensive in vitro cross-reactivity related to CCDs. Because of these developments, the Allergen Nomenclature Sub-Committee recently decided to include glycans as potentially allergenic epitopes in an adjunct section of its website (www.allergen.org). In this article, the features of the main glycan groups known to be involved in IgE recognition are revisited, and their characteristic structural, functional, and clinical features are discussed.

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

Ticks and tick-borne diseases are significant public health concerns. Bioactive molecules in tick saliva facilitate prolonged blood-feeding and transmission of tick-borne pathogens to the vertebrate host. Alpha-gal syndrome (AGS), a newly reported food allergy, is believed to be induced by saliva proteins decorated with a sugar molecule, the oligosaccharide galactose-⍺-1,3-galactose (α-gal). This syndrome is characterized by an IgE antibody-directed hypersensitivity against α-gal. The α-gal antigen was discovered in the salivary glands and saliva of various tick species including, the Lone Star tick (Amblyomma americanum). The underlying immune mechanisms linking tick bites with α-gal-specific IgE production are poorly understood and are crucial to identify and establish novel treatments for this disease. This article reviews the current understanding of AGS and its involvement with tick species.

Altered Blood Levels of Anti-Gal Antibodies in Alzheimer's Disease: A New Clue to Pathogenesis?

Alzheimer's disease is a neurodegenerative disorder whose pathological mechanisms, despite recent advances, are not fully understood. However, the deposition of beta amyloid -peptide and neuroinflammation, which is probably aggravated by dysbiotic microbiota, seem to play a key role. Anti-Gal are the most abundant xenoreactive natural antibodies. They are supposed to stem from immunization against the gut microbiota and have been implicated in the pathogenesis of several diseases, including multiple sclerosis. These antibodies target the alpha-Gal epitope, expressed on the terminal sugar units of glycoprotein or glycolipid of all mammals except apes, Old World monkeys and humans. The alpha-Gal is constitutively expressed in several bacteria constituting the brain microbiota, and alpha-Gal-like epitopes have been detected in gray matter, amyloid plaque, neurofibrillary tangles and corpora amylacea of the human brain, suggesting a potential link between anti-Gal and Alzheimer's disease etiopathogenesis. For the first time, our study searched for possible alterations of anti-Gal immunoglobulin levels in Alzheimer's disease patients. IgG and IgM blood levels were significantly lower, and IgA significantly higher in patients than in healthy subjects. These results suggest that such immunoglobulins might be implicated in Alzheimer's disease pathogenesis and open new scenarios in the research for new biomarkers and therapeutic strategies.

Tick-human interactions: from allergic klendusity to the α-Gal syndrome

Ticks and the pathogens they transmit, including bacteria, viruses, protozoa, and helminths, constitute a growing burden for human and animal health worldwide. The ability of some animal species to acquire resistance to blood-feeding by ticks after a single or repeated infestation is known as acquired tick resistance (ATR). This resistance has been associated to tick-specific IgE response, the generation of skin-resident memory CD4+ T cells, basophil recruitment, histamine release, and epidermal hyperplasia. ATR has also been associated with protection to tick-borne tularemia through allergic klendusity, a disease-escaping ability produced by the development of hypersensitivity to an allergen. In addition to pathogen transmission, tick infestation in humans is associated with the α-Gal syndrome (AGS), a type of allergy characterized by an IgE response against the carbohydrate Galα1-3Gal (α-Gal). This glycan is present in tick salivary proteins and on the surface of tick-borne pathogens such as Borrelia burgdorferi and Anaplasma phagocytophilum, the causative agents of Lyme disease and granulocytic anaplasmosis. Most α-Gal-sensitized individuals develop IgE specific against this glycan, but only a small fraction develop the AGS. This review summarizes our current understanding of ATR and its impact on the continuum α-Gal sensitization, allergy, and the AGS. We propose that the α-Gal-specific IgE response in humans is an evolutionary adaptation associated with ATR and allergic klendusity with the trade-off of developing AGS.

Anti α1-3Gal antibodies and Gal content in gut microbiota in immune disorders and multiple sclerosis

Recent observations suggest that Gal antigen content in gut microbiota and anti-Gal antibody response may influence inflammation in immune related disorders. In this review we summarized the current knowledge on antibody response to the Gal epitope in various immune disorders. We discuss the origin of Gal antigen associated to gut microbiota. In multiple sclerosis, the possible mechanisms by which the altered microbiota and/or circulating anti-Gal level could affect the immune response in this disease are presented.

Characterization of the anti-α-Gal antibody profile in association with Guillain-Barré syndrome, implications for tick-related allergic reactions

Humans evolved by losing the capacity to synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal), which resulted in the capacity to develop a protective response mediated by anti-α-Gal IgM/IgG antibodies against pathogens containing this modification on membrane proteins. As an evolutionary trade-off, humans can develop the alpha-Gal syndrome (AGS), a recently diagnosed disease mainly associated with allergic reactions to mammalian meat consumption. The etiology of the AGS is the exposure to tick bites and the IgE antibody response against α-Gal-containing glycoproteins and glycolipids. The objective of this study was to characterize the anti-α-Gal antibody response in association with the immune-mediated peripheral neuropathy, Guillain-Barré syndrome (GBS), and compare it with different factors known to modulate the antibody response to α-Gal such as exposure to tick bites and development of allergic reactions in response to tick bites. The results showed a significant decrease in the IgM/IgG response to α-Gal in GBS patients when compared to healthy individuals. In contrast, the IgM/IgG levels to α-Gal did not change in patients with allergic reactions to tick bites. The IgE response was not affected in GBS patients, but as expected, the IgE levels significantly increased in individuals exposed to tick bites and patients with tick-associated allergies. These results suggest that the immune pathways of anti-α-Gal IgM/IgG and IgE production are independent. Further studies should consider the susceptibility to allergic reactions to tick bites in GBS patients.

Future Perspectives in Small-Diameter Vascular Graft Engineering

The increased demands of small-diameter vascular grafts (SDVGs) globally has forced the scientific society to explore alternative strategies utilizing the tissue engineering approaches. Cardiovascular disease (CVD) comprises one of the most lethal groups of non-communicable disorders worldwide. It has been estimated that in Europe, the healthcare cost for the administration of CVD is more than 169 billion €. Common manifestations involve the narrowing or occlusion of blood vessels. The replacement of damaged vessels with autologous grafts represents one of the applied therapeutic approaches in CVD. However, significant drawbacks are accompanying the above procedure; therefore, the exploration of alternative vessel sources must be performed. Engineered SDVGs can be produced through the utilization of non-degradable/degradable and naturally derived materials. Decellularized vessels represent also an alternative valuable source for the development of SDVGs. In this review, a great number of SDVG engineering approaches will be highlighted. Importantly, the state-of-the-art methodologies, which are currently employed, will be comprehensively presented. A discussion summarizing the key marks and the future perspectives of SDVG engineering will be included in this review. Taking into consideration the increased number of patients with CVD, SDVG engineering may assist significantly in cardiovascular reconstructive surgery and, therefore, the overall improvement of patients' life.

A dataset for the analysis of antibody response to glycan alpha-Gal in individuals with immune-mediated disorders

Humans evolved by losing the capacity to synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal), which resulted in the development of a protective response mediated by anti-α-Gal IgM/IgG/IgA antibodies against pathogens containing this modification on membrane proteins. As an evolutionary trade-off, humans can develop the alpha-Gal syndrome (AGS), a recently diagnosed disease mediated by anti-α-Gal IgE antibodies and associated with allergic reactions to mammalian meat consumption and tick bites. However, the anti-α-Gal antibody response may be associated with other immune-mediated disorders such as those occurring in patients with COVID-19 and Guillain-Barré syndrome (GBS). Here, we provide a dataset (209 entries) on the IgE/IgM/IgG/IgA anti-α-Gal antibody response in healthy individuals and patients diagnosed with AGS, tick-borne allergies, GBS and COVID-19. The data allows correlative analyses of the anti-α-Gal antibody response with factors such as patient and clinical characteristics, record of tick bites, blood group, age and sex. These analyses could provide insights into the role of anti-α-Gal antibody response in disease symptomatology and possible protective mechanisms.

A dataset for the analysis of antibody response to glycan alpha-Gal in individuals with immune-mediated disorders

Humans evolved by losing the capacity to synthesize the glycan Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal), which resulted in the development of a protective response mediated by anti-α-Gal IgM/IgG/IgA antibodies against pathogens containing this modification on membrane proteins. As an evolutionary trade-off, humans can develop the alpha-Gal syndrome (AGS), a recently diagnosed disease mediated by anti-α-Gal IgE antibodies and associated with allergic reactions to mammalian meat consumption and tick bites. However, the anti-α-Gal antibody response may be associated with other immune-mediated disorders such as those occurring in patients with COVID-19 and Guillain-Barré syndrome (GBS). Here, we provide a dataset (209 entries) on the IgE/IgM/IgG/IgA anti-α-Gal antibody response in healthy individuals and patients diagnosed with AGS, tick-borne allergies, GBS and COVID-19. The data allows correlative analyses of the anti-α-Gal antibody response with factors such as patient and clinical characteristics, record of tick bites, blood group, age and sex. These analyses could provide insights into the role of anti-α-Gal antibody response in disease symptomatology and possible protective mechanisms.

The History of Carbohydrates in Type I Allergy

Although first described decades ago, the relevance of carbohydrate specific antibodies as mediators of type I allergy had not been recognized until recently. Previously, allergen specific IgE antibodies binding to carbohydrate epitopes were considered to demonstrate a clinically irrelevant cross-reactivity. However, this changed following the discovery of type I allergies specifically mediated by oligosaccharide structures. Especially the emerging understanding of red meat allergy characterized by IgE directed to the oligosaccharide alpha-gal showed that carbohydrate-mediated reactions can result in life threatening systemic anaphylaxis which in contrast to former assumptions proves a high clinical relevance of some carbohydrate allergens. Within the scope of this review article, we illustrate the historical development of carbohydrate-allergen-research, reaching from only diagnostically relevant crossreactive-carbohydrate-determinants to clinically important antigens mediating type I allergy. Focusing on clinical and immunological features of the alpha-gal syndrome, we highlight the discovery of oligosaccharides as potentially highly immunogenic antigens and mediators of type I allergy, report what is known about the route of sensitization and the immunological mechanisms involved in sensitization and elicitation phase of allergic responses as well as currently available diagnostic and therapeutic tools. Finally, we briefly report on carbohydrates being involved in type I allergies different from alpha-gal.

C57BL/6 α-1,3-Galactosyltransferase Knockout Mouse as an Animal Model for Experimental Chagas Disease

The leading animal model of experimental Chagas disease, the mouse, plays a significant role in studies for vaccine development, diagnosis, and human therapies. Humans, along with Old World primates, alone among mammals, cannot make the terminal carbohydrate linkage of the α-Gal trisaccharide. It has been established that the anti-α-Gal immune response is likely to be a critical factor for protection against Trypanosoma cruzi (T. cruzi) infection in humans. However, the mice customarily employed for the study of T. cruzi infection naturally express the α-Gal epitope and therefore do not produce anti-α-Gal antibodies. Here, we used the C57BL/6 α-1,3-galactosyltransferase knockout (α-GalT-KO) mouse, which does not express the α-Gal epitope as a model for experimental Chagas disease. We found the anti-α-Gal IgG antibody response to an increase in α-GalT-KO mice infected with Arequipa and Colombiana strains of T. cruzi, leading to fewer parasite nests, lower parasitemia, and an increase of INF-γ, TNF-α, and IL-12 cytokines in the heart of α-GalT-KO mice compared with α-GalT-WT mice on days 60 and 120 postinfection. We therefore agree that the C57BL/6 α-GalT-KO mouse represents a useful model for initial testing of therapeutic and immunological approaches against different strains of T. cruzi.

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.

A New Humanized Mouse Model Mimics Humans in Lacking α-Gal Epitopes and Secreting Anti-Gal Antibodies

Mice have been used as accepted tools for investigating complex human diseases and new drug therapies because of their shared genetics and anatomical characteristics with humans. However, the tissues in mice are different from humans in that human cells have a natural mutation in the α1,3 galactosyltransferase (α1,3GT) gene and lack α-Gal epitopes on glycosylated proteins, whereas mice and other nonprimate mammals express this epitope. The lack of α-Gal epitopes in humans results in the loss of immune tolerance to this epitope and production of abundant natural anti-Gal Abs. These natural anti-Gal Abs can be used as an adjuvant to enhance processing of vaccine epitopes to APCs. However, wild-type mice and all existing humanized mouse models cannot be used to test the efficacy of vaccines expressing α-Gal epitopes because they express α-Gal epitopes and lack anti-Gal Abs. Therefore, in an effort to bridge the gap between the mouse models and humans, we developed a new humanized mouse model that mimics humans in that it lacks α-Gal epitopes and secretes human anti-Gal Abs. The new humanized mouse model (Hu-NSG/α-Gal^null) is designed to be used for preclinical evaluations of viral and tumor vaccines based on α-Gal epitopes, human-specific immune responses, xenotransplantation studies, and in vivo biomaterials evaluation. To our knowledge, our new Hu-NSG/α-Gal^null is the first available humanized mouse model with such features.

Distribution of Bacterial α1,3-Galactosyltransferase Genes in the Human Gut Microbiome

Because of a loss-of-function mutation in the GGTA1 gene, humans are unable to synthetize α1,3-Galactose (Gal) decorated glycans and develop high levels of circulating anti-α1,3-Galactose antibodies (anti-Gal Abs). Anti-Gal Abs have been identified as a major obstacle of organ xenotransplantation and play a role in several host-pathogen relationships including potential susceptibility to infection. Anti-Gal Abs are supposed to stem from immunization against the gut microbiota, an assumption derived from the observation that some pathogens display α1,3-Gal and that antibiotic treatment decreases the level of anti-Gal. However, there is little information to date concerning the microorganisms producing α1,3-Gal in the human gut microbiome. Here, available α1,3-Galactosyltransferase (GT) gene sequences from gut bacteria were selectively quantified for the first time in the gut microbiome shotgun sequences of 163 adult individuals from three published population-based metagenomics analyses. We showed that most of the gut microbiome of adult individuals contained a small set of bacteria bearing α1,3-GT genes. These bacteria belong mainly to the Enterobacteriaceae family, including Escherichia coli, but also to Pasteurellaceae genera, Haemophilus influenza and Lactobacillus species. α1,3-Gal antigens and α1,3-GT activity were detected in healthy stools of individuals exhibiting α1,3-GT bacterial gene sequences in their shotgun data.

Galactose α-1,3-galactose phenotypes: Lessons from various patient populations

OBJECTIVE

To review published studies on galactose α-1,3-galactose (α-gal), a carbohydrate epitope found on proteins and lipids in nonprimate mammals and present in foods (particularly organ or fat-rich red meat) and medications, where it causes delayed-onset and immediate-onset anaphylaxis.

DATA SOURCES

A literature search for the terms galactose α-1,3-galactose and α-gal using PubMed and Embase was performed.

STUDY SELECTIONS

Studies on α-gal were included in this review.

RESULTS

Several species of ticks contain α-gal epitopes and possibly salivary adjuvants that promote high titer sensitization and clinical reactivity. Risk factors for α-gal syndrome include exposure to ticks of particular species. Age and sex differences seen in various cohorts possibly reflect the prevalence of these exposures that vary according to setting.

CONCLUSION

The reason and mechanisms for delayed onset of food-related anaphylaxis and the preponderance of abdominal reactions are not clear but may involve the kinetics of allergen digestion and processing or immunologic presentation via a different mechanism from usual immediate-type food allergy.

Environmental and Molecular Drivers of the α-Gal Syndrome

The α-Gal syndrome (AGS) is a type of allergy characterized by an IgE antibody (Ab) response against the carbohydrate Galα1-3Galβ1-4GlcNAc-R (α-Gal), which is present in glycoproteins from tick saliva and tissues of non-catarrhine mammals. Recurrent tick bites induce high levels of anti-α-Gal IgE Abs that mediate delayed hypersensitivity to consumed red meat products in humans. This was the first evidence that tick glycoproteins play a major role in allergy development with the potential to cause fatal delayed anaphylaxis to α-Gal-containing foods and drugs and immediate anaphylaxis to tick bites. Initially, it was thought that the origin of tick-derived α-Gal was either residual blood meal mammalian glycoproteins containing α-Gal or tick gut bacteria producing this glycan. However, recently tick galactosyltransferases were shown to be involved in α-Gal synthesis with a role in tick and tick-borne pathogen life cycles. The tick-borne pathogen Anaplasma phagocytophilum increases the level of tick α-Gal, which potentially increases the risk of developing AGS after a bite by a pathogen-infected tick. Two mechanisms might explain the production of anti-α-Gal IgE Abs after tick bites. The first mechanism proposes that the α-Gal antigen on tick salivary proteins is presented to antigen-presenting cells and B-lymphocytes in the context of Th₂ cell-mediated immunity induced by tick saliva. The second mechanism is based on the possibility that tick salivary prostaglandin E2 triggers Immunoglobulin class switching to anti-α-Gal IgE-producing B cells from preexisting mature B cells clones producing anti-α-Gal IgM and/or IgG. Importantly, blood group antigens influence the capacity of the immune system to produce anti-α-Gal Abs which in turn impacts individual susceptibility to AGS. The presence of blood type B reduces the capacity of the immune system to produce anti-α-Gal Abs, presumably due to tolerance to α-Gal, which is very similar in structure to blood group B antigen. Therefore, individuals with blood group B and reduced levels of anti-α-Gal Abs have lower risk to develop AGS. Specific immunity to tick α-Gal is linked to host immunity to tick bites. Basophil activation and release of histamine have been implicated in IgE-mediated acquired protective immunity to tick infestations and chronic itch. Basophil reactivity was also found to be higher in patients with AGS when compared to asymptomatic α-Gal sensitized individuals. In addition, host resistance to tick infestation is associated with resistance to tick-borne pathogen infection. Anti-α-Gal IgM and IgG Abs protect humans against vector-borne pathogens and blood group B individuals seem to be more susceptible to vector-borne diseases. The link between blood groups and anti-α-Gal immunity which in turn affects resistance to vector-borne pathogens and susceptibility to AGS, suggests a trade-off between susceptibility to AGS and protection to some infectious diseases. The understanding of the environmental and molecular drivers of the immune mechanisms involved in AGS is essential to developing tools for the diagnosis, control, and prevention of this growing health problem.

The Formation of Glycan-Specific Natural Antibodies Repertoire in GalT-KO Mice Is Determined by Gut Microbiota

Gut commensal bacteria are known to have a significant role in regulating the innate and adaptive immune homeostasis. Alterations in the intestinal microbial composition have been associated with several disease states, including autoimmune and inflammatory conditions. However, it is not entirely clear how commensal gut microbiota modulate and contribute to the systemic immunity, and whether circulating elements of the host immune system could regulate the microbiome. Thus, we have studied the diversity and abundance of specific taxons in the gut microbiota of inbred GalT-KO mice during 7 months of animal life by metagenetic high-throughput sequencing (16S rRNA gene, variable regions V3-V5). The repertoire of glycan-specific natural antibodies, obtained by printed glycan array technology, was then associated with the microbial diversity for each animal by metagenome-wide association studies (MWAS). Our data show that the orders clostridiales (most abundant), bacteriodales, lactobacillales, and deferribacterales may be associated with the development of the final repertoire of natural anti-glycan antibodies in GalT-KO mice. The main changes in microbiota diversity (month-2 and month-3) were related to important changes in levels and repertoire of natural anti-glycan antibodies in these mice. Additionally, significant positive and negative associations were found between the gut microbiota and the pattern of specific anti-glycan antibodies. Regarding individual features, the gut microbiota and the corresponding repertoire of natural anti-glycan antibodies showed differences among the examined animals. We also found redundancy in different taxa associated with the development of specific anti-glycan antibodies. Differences in microbial diversity did not, therefore, necessarily influence the overall functional output of the gut microbiome of GalT-KO mice. In summary, the repertoire of natural anti-carbohydrate antibodies may be partially determined by the continuous antigenic stimulation produced by the gut bacterial population of each GalT-KO mouse. Small differences in gut microbiota diversity could determine different repertoire and levels of natural anti-glycan antibodies and consequently might induce different immune responses to pathogens or other potential threats.

Role and Mechanism of Galactose-Alpha-1,3-Galactose in the Elicitation of Delayed Anaphylactic Reactions to Red Meat

Purpose of Review

The alpha-Gal (α-Gal) syndrome is characterized by the presence of IgE antibodies directed at the carbohydrate galactose-alpha-1,3-galactose (α-Gal). In this article, we review the presence of α-Gal in food and non-food sources; we discuss the evolutionary context of the antibody response to α-Gal and highlight immune responses to α-Gal and other carbohydrates.

Recent findings

IgE antibodies have been associated with delayed allergy to red meat. In addition to food, drugs, and other products of animal origin are increasingly perceived as a risk for patients sensitized to α-Gal. The link between tick bites and anti-α-Gal IgE-antibody production that has been established first by epidemiological studies has now been confirmed in mouse models.

Summary

The anti-α-Gal immune response is complex and characterized by a unique feature. IgM and IgG antibodies have been found to confer protection against pathogens whereas the IgE-response to α-Gal is detrimental and causes severe reactions upon exposure to mammalian meat and other products.

Xenogeneic bone matrix immune risk assessment using GGTA1 knockout mice

Homeotransplantation of bones for replacement therapy have been demonstrated reliably in clinical data. However, human donor bones applicable for homeotransplantation are in short supply, which facilitates the search for suitable alternatives, such as xenografts grafts. The α-Gal antigen-related immune risk of xenografts directly affects the safety and effectiveness of the biomaterials and limits their applications in the clinic. The immune risk can be prevented by depletion or breaking anti-Gal antibody prior to transplant. Therefore, how to assess the immune risk of the bone substitutes and select the reliable animal research model become extremely important. In this study, we prepared lyophilized bone substitutes (T1) and Guanghao Biotech bone substitutes (T2, animal-derived biomaterials with α-Gal antigen decreased), aimed to assess the immune risk of xenografts bone substitutes on GGTA1 knockout mice. The α-Gal antigen contents of T1 and T2 were firstly detected by ELISA method in vitro. The bone substitutes were then implanted subcutaneously into GGTA1 knockout mice for 2, 4 and 12 weeks, respectively. The total serum antibody levels, anti-α-Gal antibody levels, inflammatory cytokine and splenic lymphocyte surface molecules were detected and histology analysis of skin and thymus were performed to systematically evaluate the immune response caused by the T1 and T2 bone substitutes in mice. In vitro results showed that the amount of α-Gal epitopes in T1 bone substitutes was significantly higher than T2 bone substitutes, and the clearance rate of α-Gal antigen in T2 bone substitutes achieved about 55.6%. Results of antibody level in vivo showed that the T1 bone substitutes group possessed significantly higher total IgG, IgM, IgA and anti-α-Gal IgG levels than T2 and control group, while T2 group showed no significant changes of these indexes compared with control. In terms of inflammatory cytokines, T1 bone substitutes showed evidently higher levels of IL-4, IL-12P70 and IL-10 than T2 and control, while T2 group was comparable to control. No changes in the levels of splenic lymphocyte surface molecules were found in the three groups (T1, T2 and control group) during the experimental periods. The pathological results demonstrated that the inflammatory response in T2 group was lighter than the T1 group, which was in accordance with the inflammatory cytokines levels. The above results indicated that the process of antigen removal effectively reduced the α-Gal antigens content in T2 bone substitutes, which caused little immune response in vivo and could be used as bone healing materials. This study also demonstrated that GGTA1 knockout mice can be used as a routine tool to assess the immune risk of animal-derived biomaterials.

Cytokine Profile Associated with Selective Removal of Natural Anti-αGal Antibodies in a Sepsis Model in Gal-KO Mice

Selective depletion of natural anti-Galα1-3Galβ1-4GlcNAc (so-called anti-αGal) antibodies is achieved in α1,3-galactosyltransferase knockout (Gal-KO) mice by administration of the soluble glycoconjugate of αGal GAS914. This molecule removed up to 90% of natural circulating anti-αGal antibodies without causing unspecific production of cytokines in wild-type (CBA) and Gal-KO mice. However, the removal of anti-αGal antibodies in Gal-KO mice with GAS914 in the context of sepsis after cecal ligation and puncture (CLP) was associated with a significant increase in the production of leptin, CXLC1, CXLC13, and TIMP-1 cytokines compared to vehicle (PBS)-treated controls. Despite the current lack of understanding of the underlying mechanism, our data suggest a putative role of natural anti-αGal antibodies in the regulation of some cytokines during sepsis.

Molecular Evolution of the Glycosyltransferase 6 Gene Family in Primates

Glycosyltransferase 6 gene family includes ABO, Ggta1, iGb3S, and GBGT1 genes and by three putative genes restricted to mammals, GT6m6, GTm6, and GT6m7, only the latter is found in primates. GT6 genes may encode functional and nonfunctional proteins. Ggta1 and GBGT1 genes, for instance, are pseudogenes in catarrhine primates, while iGb3S gene is only inactive in human, bonobo, and chimpanzee. Even inactivated, these genes tend to be conversed in primates. As some of the GT6 genes are related to the susceptibility or resistance to parasites, we investigated (i) the selective pressure on the GT6 paralogs genes in primates; (ii) the basis of the conservation of iGb3S in human, chimpanzee, and bonobo; and (iii) the functional potential of the GBGT1 and GT6m7 in catarrhines. We observed that the purifying selection is prevalent and these genes have a low diversity, though ABO and Ggta1 genes have some sites under positive selection. GT6m7, a putative gene associated with aggressive periodontitis, may have regulatory function, but experimental studies are needed to assess its function. The evolutionary conservation of iGb3S in humans, chimpanzee, and bonobo seems to be the result of proximity to genes with important biological functions.

Enhanced anti-tumor immunity against breast cancer induced by whole tumor cell vaccines genetically modified expressing α-Gal epitopes

Whole tumor cell vaccines have shown much promise, but demonstrated poor efficiency in phase III trials. In this study, we modified MDA-MB‑231 tumor cells (MDA-MB‑231Gal+) to express α-1, 3-galactosyltransferase (α-1, 3-GT) protein, to potentially enhance antitumor effect of whole tumor cell vaccines. MDA-MB‑231 tumor cell vaccines were transfected with a reconstructed lentiviral containing α-1, 3-GT genes. Tumor growth, tumorigenesis and survival of Hu-NOD-SCID mice were observed when tumor-bearing mice were injected with tumor cell vaccines. Proliferation and apoptosis in MDA-MB‑231 tumor xenografts were observed by immunohistochemistry. The levels of cytokine secretion in the serum of mice were tested by ELISA. CD8+ T cells infiltrating tumors were assessed by flow cytometry. MDA-MB‑231Gal+ cells expressed active α-1, 3-GT and produced α-Gal in vitro. MDA-MB‑231Gal+ cell vaccines suppressed tumor growth and tumorigenesis in immunized Hu-NOD-SCID mice. Additionally, decrease of TGF-β, IL-10 and increase of INF-γ, IL-12 were observed in tumor cell vaccinated mice. Furthermore, the cell vaccines enhanced infiltration of cytotoxic CD8+ T cells in the tumor microenvironment of immunized mice. The MDA-MB‑231Gal+ cell vaccines modified α-1, 3-GT genes improved the antitumor effect.

Characteristics of α-Gal epitope, anti-Gal antibody, α1,3 galactosyltransferase and its clinical exploitation (Review)

The α-Gal epitope (Galα1,3Galα1,4GlcNAc-R) is ubiquitously presented in non-primate mammals, marsupials and New World Monkeys, but it is absent in humans, apes and Old World monkeys. However, the anti-Gal antibody (~1% of immunoglobulins) is naturally generated in human, and is found as the immunoglobulin G (IgG), IgM and IgA isotypes. Owing to the specific binding of the anti-Gal antibody with the α-Gal epitope, humans have a distinct anti-α-gal reactivity, which is responsible for hyperacute rejection of organs transplanted from α-gal donors. In addition, the α1,3 galactosyltransferases (α1,3GT) can catalyze the synthesis of the α-Gal epitope. Therefore, the α1,3GT gene, which encodes the α1,3GT, is developed profoundly. The distributions of the α-Gal epitope and anti-Gal antibody, and the activation of α1,3GT, reveal that the enzyme of α1,3GT in ancestral primates is ineffective. Comparison of the nucleotide sequence of the human α1,3-GT pseudogene to the corresponding different species sequence, and according to the evolutionary tree of different species, the results of evolutionary inactivation of the α1,3GT gene in ancestral primates attribute to the mutations under a stronger selective pressure. However, on the basis of the structure, the mechanism and the specificity of the α-Gal epitope and anti-Gal antibody, they can be applied to clinical exploitation. Knocking out the α1,3GT gene will eliminate the xenoantigen, Gal(α1,3)Gal, so that the transplantation of α1,3GT gene knockout pig organ into human becomes a potential clinically acceptable treatment for solving the problem of organ shortage. By contrast, the α-Gal epitope expressed through the application of chemical, biochemical and genetic engineering can be exploited for the clinical use. Targeting anti-Gal-mediated autologous tumor vaccines, which express α-Gal epitope to antigen-presenting cells, would increase their immunogenicity and elicit an immune response, which will be potent enough to eradicate the residual tumor cells. For tumor vaccines, the way of increasing immunogenicity of certain viral vaccines, including flu vaccines and human immunodeficiency virus vaccines, can also be used in the elderly. Recently, α-Gal epitope nanoparticles have been applied to accelerate wound healing and further directions on regeneration of internally injured tissues.