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A novel monoclonal IgG1 antibody specific for Galactose-alpha-1,3-galactose questions alpha-Gal epitope expression by bacteria.

ABSTRACT: The alpha-Gal epitope (α-Gal) with the determining element galactose-α1,3-galactose can lead to clinically relevant allergic reactions and rejections in xenotransplantation. These immune reactions can develop because humans are devoid of this carbohydrate due to evolutionary loss of the enzyme α1,3-galactosyltransferase (GGTA1). In addition, up to 1% of human IgG antibodies are directed against α-Gal, but the stimulus for the induction of anti-α-Gal antibodies is still unclear. Commensal bacteria have been suggested as a causal factor for this induction as α-Gal binding tools such as lectins were found to stain cultivated bacteria isolated from the intestinal tract. Currently available tools for the detection of the definite α-Gal epitope, however, are cross-reactive, or have limited affinity and, hence, offer restricted possibilities for application. In this study, we describe a novel monoclonal IgG1 antibody (27H8) specific for the α-Gal epitope. The 27H8 antibody was generated by immunization of Ggta1 knockout mice and displays a high affinity towards synthetic and naturally occurring α-Gal in various applications. Using this novel tool, we found that intestinal bacteria reported to be α-Gal positive cannot be stained with 27H8 questioning whether commensal bacteria express the native α-Gal epitope at all.

SUBMITTER: Kreft L

PROVIDER: S-EPMC9391071 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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A novel monoclonal IgG1 antibody specific for Galactose-alpha-1,3-galactose questions alpha-Gal epitope expression by bacteria.

Kreft Luisa L Schepers Aloys A Hils Miriam M Swiontek Kyra K Flatley Andrew A Janowski Robert R Mirzaei Mohammadali Khan MK Dittmar Michael M Chakrapani Neera N Desai Mahesh S MS Eyerich Stefanie S Deng Li L Niessing Dierk D Fischer Konrad K Feederle Regina R Blank Simon S Schmidt-Weber Carsten B CB Hilger Christiane C Biedermann Tilo T Ohnmacht Caspar C

Frontiers in immunology 20220805

The alpha-Gal epitope (α-Gal) with the determining element galactose-α1,3-galactose can lead to clinically relevant allergic reactions and rejections in xenotransplantation. These immune reactions can develop because humans are devoid of this carbohydrate due to evolutionary loss of the enzyme α1,3-galactosyltransferase (GGTA1). In addition, up to 1% of human IgG antibodies are directed against α-Gal, but the stimulus for the induction of anti-α-Gal antibodies is still unclear. Commensal bacteri ...[more]

PMID: 35990627

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Project description: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.

Project description:This review describes the significance of the α-gal epitope (Galα-3Galβ1-4GlcNAc-R) as the core of human blood-group A and B antigens (A and B antigens), determines in mouse models the principles underlying the immune response to these antigens, and suggests future strategies for the induction of immune tolerance to incompatible A and B antigens in human allografts. Carbohydrate antigens, such as ABO antigens and the α-gal epitope, differ from protein antigens in that they do not interact with T cells, but B cells interacting with them require T-cell help for their activation. The α-gal epitope is the core of both A and B antigens and is the ligand of the natural anti-Gal antibody, which is abundant in all humans. In A and O individuals, anti-Gal clones (called anti-Gal/B) comprise >85% of the so-called anti-B activity and bind to the B antigen in facets that do not include fucose-linked α1-2 to the core α-gal. As many as 1% of B cells are anti-Gal B cells. Activation of quiescent anti-Gal B cells upon exposure to α-gal epitopes on xenografts and some protozoa can increase the titer of anti-Gal by 100-fold. α1,3-Galactosyltransferase knockout (GT-KO) mice lack α-gal epitopes and can produce anti-Gal. These mice simulate human recipients of ABO-incompatible human allografts. Exposure for 2-4 weeks of naïve and memory mouse anti-Gal B cells to α-gal epitopes in the heterotopically grafted wild-type (WT) mouse heart results in the elimination of these cells and immune tolerance to this epitope. Shorter exposures of 7 days of anti-Gal B cells to α-gal epitopes in the WT heart result in the production of accommodating anti-Gal antibodies that bind to α-gal epitopes but do not lyse cells or reject the graft. Tolerance to α-gal epitopes due to the elimination of naïve and memory anti-Gal B cells can be further induced by 2 weeks in vivo exposure to WT lymphocytes or autologous lymphocytes engineered to present α-gal epitopes by transduction of the α1,3-galactosyltransferase gene. These mouse studies suggest that autologous human lymphocytes similarly engineered to present the A or B antigen may induce corresponding tolerance in recipients of ABO-incompatible allografts. The review further summarizes experimental works demonstrating the efficacy of α-gal therapies in amplifying anti-viral and anti-tumor immune-protection and regeneration of injured tissues.

Dataset Information

A novel monoclonal IgG1 antibody specific for Galactose-alpha-1,3-galactose questions alpha-Gal epitope expression by bacteria.

Publications

A novel monoclonal IgG1 antibody specific for Galactose-alpha-1,3-galactose questions alpha-Gal epitope expression by bacteria.

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