Peptide Antibody Reactivity to Homologous Regions in Glutamate Decarboxylase Isoforms and Coxsackievirus B4 P2C

Abstract

Two isoforms of the glutamate decarboxylase (GAD) enzyme exist, GAD65 and GAD67, which are associated with type 1 diabetes (T1D) and stiff-person syndrome (SPS), respectively. Interestingly, it has been reported that T1D patients seldom develop SPS, whereas patients with SPS occasionally develop T1D. In addition, coxsackievirus B4 (CVB4) has previously been proposed to be involved in the onset of T1D through molecular mimicry. On this basis, we aimed to examine antibody cross-reactivity between a specific region of GAD65 and GAD67, which has high sequence homology to the nonstructural P2C protein of CVB4 to determine potential correlations at antibody level. Monoclonal peptide antibodies generated in mice specific for a region with high similarity in all three proteins were screened for reactivity along with human sera in immunoassays. In total, six antibodies were generated. Two of the antibodies reacted to both GAD isoforms. However, none of the antibodies were cross-reactive to CVB, suggesting that antibody cross-reactivity between GAD65 and CVB, and GAD67 and CVB may not contribute to the onset of T1D and SPS, respectively.

Antibody Cross-Reactivity in Auto-Immune Diseases

“…Cross-reactivity associated with molecular mimicry can be divided into subgroups: structural homology and sequence homology (Table 2) [7,41,[84][85][86][87][88][89][90][91]. Sequence homology The term "molecular mimicry" was originally used to describe the existence of "similar" antigens expressed by infectious agents and an infected host, which may facilitate the ability of microbes to avoid the host's immune response [81].…”

Advances in Antibody Design and Antigenic Peptide Targeting 2.0

“…Peptides which are suitable for use in generation of peptide antibodies may be identified using bioinformatic tools or phage display [5,6] or carefully selected by studying the protein structure and amino acid sequence, depending on the intended use [7,8]. Following the identification of targets, peptide antibodies are generated using standard procedures, e.g., by immunization of an animal, typically mice, or by phage display [6][7][8][9].…”

“…Peptides which are suitable for use in generation of peptide antibodies may be identified using bioinformatic tools or phage display [5,6] or carefully selected by studying the protein structure and amino acid sequence, depending on the intended use [7,8]. Following the identification of targets, peptide antibodies are generated using standard procedures, e.g., by immunization of an animal, typically mice, or by phage display [6][7][8][9]. For example, Petry and colleagues successfully examined the reproducibility of phage-displayed peptide selection tools for the production of antibodies, whereas Valdovino-Navaro and coworkers described the selection of a peptide antibody to SARS-CoV-2 SP240, which was isolated from a peptide phage library with high stability [6,10].…”

“…For example, Petry and colleagues successfully examined the reproducibility of phage-displayed peptide selection tools for the production of antibodies, whereas Valdovino-Navaro and coworkers described the selection of a peptide antibody to SARS-CoV-2 SP240, which was isolated from a peptide phage library with high stability [6,10]. In contrast, studies by AlEraky, Trier and Mughal used carefully selected peptides based on amino acid analysis to generate peptide antibodies using common immunization procedures [7][8][9].…”

“…Furthermore, peptide antibodies may function as specific research tools. Along these lines, Trier et al, examined antibody cross-reactivities between the P2C coxsackie virus B (CVB) protein and glutamate decarboxylase (GAD)65 by generating peptide antibodies for regions in P2C and GAD65 with 100% sequence similarity (PEVKEK) to examine the potential role of CVB contributing to type 1 diabetes trough molecular mimicry; however, no cross-reactive antibody clones were detected [8]. This is in direct contrast to the results of a recent study by Ehlers and collaborators which generated an antibody to the glucocorticoid receptor; which was found to cross react with the AMP deaminase 2 (AMPD2) and transcription intermediary factor 1-beta (TRIM28) [13].…”