Peptidome Analysis of Western Blots Identifies Natural Bispecific Antibody-Bound Corynebacterium and Phage B-cell Epitopes with Potential Relevance to Psoriasis

The high prevalence of Corynebacterium (C.) simulans in lesional and non-lesional psoriatic skin, and its correlation with disease severity, suggest a potential role in psoriasis pathophysiology. Previous exploratory Western blot and peptidome analyses of C. simulans extracts using IgG from psoriasis patients identified B-cell epitopes bound by natural bispecific antibodies (nBsAbs, presumably IgG4). These epitopes were primarily derived from intrinsically disordered proteins, autoantigens, and bacteriophage proteins. Subsequent analyses using pooled psoriasis serum unexpectedly revealed antigenic peptides from numerous Corynebacterium species. Taxonomic filtering identified several thousand Corynebacterium-derived epitopes across 40 species, including C. simulans, C. striatum, C. diphtheriae, common skin commensals, environmental and food-associated strains, the plant pathogen Clavibacter michiganensis, and the zoonotic pathogens C. pseudotuberculosis and C. ulcerans. Additional epitopes originated from related genera (Prescottella, Tsukamurella, Mycobacterium, Gordonia, Nocardia, and Rhodococcus) as well as bacteriophages of the order Caudovirales. Among the identified peptides, 183 epitopes from 46 antigens mapped to 30S and 50S ribosomal proteins. Numerous additional epitopes derived from proteins involved in transcription, translation, aminoacyl-tRNA ligases (covering 17 amino acids), transcriptional regulation, RNA processing and degradation, sigma factors, and ribosome-associated proteins. Notably, 40 epitopes originated from highly conserved FoF1-ATP synthase subunits (, {beta}, {gamma}, {delta}). One peptide containing the catalytic Walker A nucleotide-binding motif showed sequence identity with mitochondrial FoF1-ATP synthase, suggesting potential autoimmune cross-reactivity and implicating this enzyme complex as a psoriasis-associated autoantigen candidate. Thousands of further epitopes were identified from proteins involved in respiratory chain function, stress responses, bacterial immunity, membrane transport, chaperones, cell wall biosynthesis, proteases, and peptidases, particularly ATP-dependent Clp proteases. Antigens from biosynthetic and metabolic pathways represented the most abundant nBsAb targets. In addition, 368 DECOY peptides were assigned to bacteriophage proteins. The detection of epitopes from toxin-producing species such as C. diphtheriae, C. pseudotuberculosis, and C. ulcerans further supports a potential microbial contribution to psoriasis pathogenesis. This exploratory study presents a streamlined strategy for B-cell epitope mapping of Corynebacterium antigens using IDP-enriched antigen-IgG4 complexes. The approach holds promise for the development of B-cell epitope-based vaccines targeting microbial, viral, tumor, and allergen-associated diseases.