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

Abstract

BackgroundN-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.MethodsELISA 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).ResultsELISA 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).ConclusionsFurther 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.

Human species-specific loss of CMP- N -acetylneuraminic acid hydroxylase enhances atherosclerosis via intrinsic and extrinsic mechanisms

“…S8G). This is likely because the polyclonal antibody response is extremely complex and variable between individuals, and no single epitope can be easily correlated with disease (43). In general, we show that the immune response to the metabolically incorporated foreign Neu5Gc in Gc-immunized Cmah −/− Ldlr −/− mice fed a Neu5Gc-rich HFD was significantly correlated with the increased atherosclerosis development.…”

“…The Combination of Human-Like Anti-Neu5Gc Antibodies and Neu5Gc-HFD Further Increases Atherogenesis in Cmah −/− Ldlr −/− Mice. Due to the lack of Neu5Gc production most humans develop circulating anti-Neu5Gc antibodies (42,43). Unlike humans, Cmah −/− Ldlr −/− mice do not spontaneously produce anti-Neu5Gc antibodies even after long-term feeding of Neu5Gc-rich chow (44).…”

Blood Type Diets (BTD) and Aging: An Overview

“…All MOAs: Notwithstanding any of the four MOA, the result is the same: food ingredients can interact with the human GI mucosae and/or cross the intestine barrier into the blood stream. Specifically, glycans can be absorbed by cells and circulate in the body [9]. Several studies demonstrated AGA are found in the blood of non-allergic donors, confirming food glycans can cross the barrier [168].…”

“…Because of their unique chemical properties, glycans have unsurpassed structural variability, and enormous changeability beyond the simple sequence, as for proteins or nucleic acids [7]. The presence of an anomeric carbon atom, the possibility of linkage formation involving different acceptor sites and the ring size with frequent occurrence of branching and site-specific modifications allows glycans to display unique properties [8,9]. Hence, it can be stated that the proteosome and the nucleosome are no match for the glycome, as the coding capacity of the oligosaccharide language is simply orders of magnitude higher [10].…”

No Increase in Colon Cancer Risk Following Induction with Neu5Gc-Bearing Rabbit Anti-T Cell IgG (ATG) in Recipients of Kidney Transplants

“…The proposed causal role of anti-Neu5G in inducing tumors in mice [ 17 ] is speculative in humans. Although no difference was observed using ELISA, higher anti-Neu5Gc binding synthetic Neu5Gc glycans have been recently reported in a series of 71 patients with colon carcinoma [ 19 ]. These findings did not attain statistical power and the proposed causal role of Neu5Gc accumulation in tumors [ 5 ] remains speculative.…”