Polyclonal human antibodies against glycans bearing red meat-derived non-human sialic acid N-glycolylneuraminic acid are stable, reproducible, complex and vary between individuals: Total antibody levels are associated with colorectal cancer risk.
N-glycolylneuraminic acid (Neu5Gc) is a non-human red-meat-derived sialic acid immunogenic to humans. Neu5Gc can be metabolically incorporated into glycan chains on human endothelial and epithelial surfaces. This represents the first example of a "xeno-autoantigen", against which circulating human "xeno-autoantibodies" can react. The resulting inflammation ("xenosialitis") has been demonstrated in human-like Neu5Gc-deficient mice and contributed to carcinoma progression via antibody-mediated inflammation. Anti-Neu5Gc antibodies have potential as biomarkers for diseases associated with red meat consumption such as carcinomas, atherosclerosis, and type 2 diabetes. METHODS: ELISA assays measured antibodies against Neu5Gc or Neu5Gc-glycans in plasma or serum samples from the Nurses' Health Studies, the Health Professionals Follow-up Study, and the European Prospective Investigation into Cancer and Nutrition, including inter-assay reproducibility, stability with delayed sample processing, and within-person reproducibility over 1-3 years in archived samples. We also assessed associations between antibody levels and coronary artery disease risk (CAD) or red meat intake. A glycan microarray was used to detected antibodies against multiple Neu5Gc-glycan epitopes. A nested case-control study design assessed the association between total anti-Neu5Gc antibodies detected in the glycan array assay and the risk of colorectal cancer (CRC). RESULTS: ELISA assays showed a wide range of anti-Neu5Gc responses and good inter-assay reproducibility, stability with delayed sample processing, and within-person reproducibility over time, but these antibody levels did not correlate with CAD risk or red meat intake. Antibodies against Neu5Gc alone or against individual Neu5Gc-bearing epitopes were also not associated with colorectal cancer (CRC) risk. However, a sialoglycan microarray study demonstrated positive association with CRC risk when the total antibody responses against all Neu5Gc-glycans were combined. Individuals in the top quartile of total anti-Neu5Gc IgG antibody concentrations had nearly three times the risk compared to those in the bottom quartile (Multivariate Odds Ratio comparing top to bottom quartile: 2.98, 95% CI: 0.80, 11.1; P for trend = 0.02). CONCLUSIONS: Further work harnessing the utility of these anti-Neu5Gc antibodies as biomarkers in red meat-associated diseases must consider diversity in individual antibody profiles against different Neu5Gc-bearing glycans. Traditional ELISA assays for antibodies directed against Neu5Gc alone, or against specific Neu5Gc-glycans may not be adequate to define risk associations. Our finding of a positive association of total anti-Neu5Gc antibodies with CRC risk also warrants confirmation in larger prospective studies.
Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Slone Epidemiology Center, Boston University, Boston, Massachusetts, United States of America. Department of Public Health and Primary Care, University of Cambridge, Cambridge, United Kingdom. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Department of Chemistry, University of California, Davis, California, United States of America. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America. Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America. Department of Chemistry, University of California, Davis, California, United States of America. Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America. Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America. Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America. Department of Public Health and Primary Care, University of Cambridge, Cambridge, United Kingdom. Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America. Department of Medicine, University of California, San Diego, California, United States of America. Department of Cellular & Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, California, United States of America.
