Microstructure of the sialic acid moiety of N-glycolylneuraminyllactosylceramide and the elucidation of Hanganutziu and Deicher (HD) antigenicity

Identification of chicken-derived scFv against N-glycolylneuraminic acid retrieved from an immune library by phage display

N- glycolylneuraminic acid (Neu5Gc) is a type of sialic acid, it can be synthesized by a range of mammals except chickens and healthy human. After entering human body, Neu5Gc in foods such as red meat and milk can cause chronic inflammation, thus promoting the development of cancer and related diseases. In this study, we identified a gene sequence of Neu5Gc-specific single-chain variable fragment (ScFv) by phage display from a primary chicken antibodies library. Then the gene sequence was used to express a 29 kDa anti-Neu5Gc ScFv protein as detection probe in competitive inhibition ELISA (IC-ELISA). The linear regression equation of the IC-ELISA was y = 23.12x+33.19 (R = 0.980), and the half-maximal inhibitory concentration (IC50) and the limit of detection (LOD) was 5.333 and 0.66 μg/mL. The mean recovery of the spiked samples was 83.04%, and the intra-assay and inter-assay coefficients of variation (CVs) were both 5.59%. The results suggested that the specific anti-Neu5Gc ScFv is a promising probe for the development of IC-ELISA and test strip in order to detect the presence of Neu5Gc in red meat, milk, and tumor tissues.

From "Serum Sickness" to "Xenosialitis": Past, Present, and Future Significance of the Non-human Sialic Acid Neu5Gc

The description of "serum sickness" more than a century ago in humans transfused with animal sera eventually led to identification of a class of human antibodies directed against glycans terminating in the common mammalian sialic acid N-Glycolylneuraminic acid (Neu5Gc), hereafter called "Neu5Gc-glycans." The detection of such glycans in malignant and fetal human tissues initially raised the possibility that it was an oncofetal antigen. However, "serum sickness" antibodies were also noted in various human disease states. These findings spurred further research on Neu5Gc, and the discovery that it is not synthesized in the human body due to a human-lineage specific genetic mutation in the enzyme CMAH. However, with more sensitive techniques Neu5Gc-glycans were detected in smaller quantities on certain human cell types, particularly epithelia and endothelia. The likely explanation is metabolic incorporation of Neu5Gc from dietary sources, especially red meat of mammalian origin. This incorporated Neu5Gc on glycans appears to be the first example of a "xeno-autoantigen," against which varying levels of "xeno-autoantibodies" are present in all humans. The resulting chronic inflammation or "xenosialitis" may have important implications in human health and disease, especially in conditions known to be aggravated by consumption of red meat. In this review, we will cover the early history of the discovery of "serum sickness" antibodies, the subsequent recognition that they were partly directed against Neu5Gc-glycans, the discovery of the genetic defect eliminating Neu5Gc production in humans, and the later recognition that this was not an oncofetal antigen but the first example of a "xeno-autoantigen." Further, we will present comments about implications for disease risks associated with red meat consumption such as cancer and atherosclerosis. We will also mention the potential utility of these anti-Neu5Gc-glycan antibodies in cancer immunotherapy and provide some suggestions and perspectives for the future. Other reviews in this special issue cover many other aspects of this unusual pathological process, for which there appears to be no other described precedent.

Synthesis of a Benvitimod Impurity: (Z)-3,5-Dihydroxy-4-Isopropylstilbene

(E)-3,5-dihydroxy-4-isopropylstilbene (Benvitimod), a new medicine for the treatment of psoriasis and eczema, belongs to the hydroxystilbene family. The synthesis leads to the E-isomer, (Z)-3,5-dihydroxy-4-isopropylstilbene being present as a major impurity in the preparation of Benvitimod. We describe a synthesis of the Benvitimod impurity: (Z)-3,5-dihydroxy-4-isopropylstilbene starting from 3,5-dihydroxybenzoic acid, through an isopropyl reaction, esterification and etherification, reduction, oxidation, Perkin condensation, decarboxylation and demethylation. The optimal reaction conditions were also determined.

Involvement of a non-human sialic Acid in human cancer

Sialic acids are common monosaccharides that are widely expressed as outer terminal units on all vertebrate cell surfaces, and play fundamental roles in cell–cell and cell–microenvironment interactions. The predominant sialic acids on most mammalian cells are N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac). Neu5Gc is notable for its deficiency in humans due to a species-specific and species-universal inactivating deletion in the CMAH gene encoding the hydroxylase that converts CMP-Neu5Ac to CMP-Neu5Gc. However, Neu5Gc is metabolically incorporated into human tissues from dietary sources (particularly red meat), and detected at even higher levels in some human cancers. Early life exposure to Neu5Gc-containing foods in the presence of certain commensal bacteria that incorporate dietary Neu5Gc into lipooligosaccharides can lead to generation of antibodies that are also cross-reactive against Neu5Gc-containing glycans in human tissues (“xeno-autoantigens”). Such anti-Neu5Gc “xeno-autoantibodies” are found in all humans, although ranging widely in levels among individuals, and displaying diverse and variable specificities for the underlying glycan. Experimental evidence in a human-like Neu5Gc-deficient Cmah^−/−mouse model shows that inflammation due to “xenosialitis” caused by this antigen–antibody interaction can promote tumor progression, suggesting a likely mechanism for the well-known epidemiological link between red meat consumption and carcinoma risk. In this review, we discuss the history of this field, mechanisms of Neu5Gc incorporation into tissues, the origin and specificities of human anti-Neu5Gc antibodies, their use as possible cancer biomarkers, implications of xenosialitis in cancer initiation and progression, and current and future approaches toward immunotherapy that could take advantage of this unusual human-specific phenomenon.

Establishment of a human monoclonal antibody to Hanganutziu-Deicher antigen as a tumor-associated carbohydrate antigen

We have established a human-human hybridoma producing a monoclonal antibody against a tumor-associated carbohydrate-specific antigen, Hanganutziu-Deicher (HD) antigen. Human spleen lymphocytes from a patient with esophageal varices complicated with liver cirrhosis were cultured in serum-free medium and co-stimulated with both anti-human mu-chain antibodies and supernatants of concanavalin A-stimulated human spleen cell culture (ConA sup). The activated lymphocytes were subsequently primed in vitro with particulate HD3 antigen and fused with a parent hybrid myeloma cell line, KR-12. A hybridoma, 1F43E31G7 produced anti-HD human monoclonal antibody (IgM lambda). This monoclonal antibody reacted strongly with N-glycolylneuraminyl alpha 2-3 lactosylceramide (HD3) and slightly with N-glycolylneuraminyl alpha 2-3 lactoneotetraosylceramide (HD5), but did not react with N-glycolylneuraminyl alpha 2-3 lactoneohexaosylceramide (HD7), N-acetylneuraminyl alpha 2-3 lactosylceramide (GM3) and other derivatives of HD3 prepared by chemical modification of the sialic acid residue of HD3, which indicates that the monoclonal antibody is directed precisely toward the terminal sialic acid and whole structure of HD3.