Antibodies Against Unusual Forms of Sialylated Glycans

P S Obukhova; M M Ziganshina; N V Shilova; A A Chinarev; G V Pazynina; A Y Nokel; A V Terenteva; N R Khasbiullina; G T Sukhikh; A A Ragimov; E L Salimov; V I Butvilovskaya; S M Polyakova; J Saha; N V Bovin

doi:10.32607/actanaturae.11631

Antibodies Against Unusual Forms of Sialylated Glycans

Acta Naturae. 2022 Apr-Jun;14(2):85-92. doi: 10.32607/actanaturae.11631.

Authors

P S Obukhova^{1

2}, M M Ziganshina², N V Shilova^{1

2}, A A Chinarev¹, G V Pazynina¹, A Y Nokel^{1

2}, A V Terenteva², N R Khasbiullina², G T Sukhikh^{2

3}, A A Ragimov³, E L Salimov³, V I Butvilovskaya⁴, S M Polyakova^{1

5}, J Saha⁶, N V Bovin^{1

7}

Affiliations

¹ Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, 117997 Russia.
² National Medical Research Center for Obstetrics, Gynecology and Perinatology named after V.I. Kulakov of the Ministry of Health care of Russian Federation, Moscow, 117997 Russia.
³ I.M. Sechenov First Moscow State Medical University of the Ministry of Health care of the Russian Federation (Sechenov University), Moscow, 119991 Russia.
⁴ Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences, Moscow, 119991 Russia.
⁵ Synthaur LLC, Moscow, 117997 Russia.
⁶ Centre of Biomedical Research, Sanjay Gandhi PostGraduate Institute of Medical Science, Lucknow, 226014 India.
⁷ Centre for Kode Technology Innovation, Auckland University of Technology, Auckland, 1010 New Zealand.

Abstract

Previous studies have shown that in the blood of healthy donors (1) there are no natural antibodies against sialylated glycoproteins, which contain Neu5Acα (N-acetylneuraminic acid) as the most widespread form of human sialic acid, and (2) there is a moderate level of antibodies capable of binding unnatural oligosaccharides, where Neu5Ac is beta-linked to a typical mammalian glycan core. In the present study, we investigated antibodies against βNeu5Ac in more detail and verified the presence of Kdn (2-keto-3-deoxy- D-glycero-D-galacto-nonulosonic acid) as a possible cause behind their appearance in humans, taking into account the expected cross-reactivity to Kdn glycans, which are found in bacterial glycoconjugates in both the α- and β-forms. We observed the binding of peripheral blood immunoglobulins to sialyllactosamines (where "sialyl" is Kdn or neuraminic acid) in only a very limited number of donors, while the binding to monosaccharide Kdn occurred in all samples, regardless of the configuration of the glycosidic bond of the Kdn moiety. In some individuals, the binding level of some of the immunoglobulins was high. This means that bacterial Kdn glycoconjugates are very unlikely to induce antibodies to βNeu5Ac glycans in humans. To determine the reason for the presence of these antibodies, we focused on noninfectious pathologies, as well as on a normal state in which a significant change in the immune system occurs: namely, pregnancy. As a result, we found that 2/3 of pregnant women have IgM in the blood against Neu5Acβ2-3Galβ1-4GlcNAcβ. Moreover, IgG class antibodies against Neu5Acβ2-3Galβ1-4GlcNAcβ and Neu5Acβ2-6Galβ1-4GlcNAcβ were also detected in eluates from the placenta. Presumably, these antibodies block fetal antigens.

Keywords: Kdn; alylated glycans; glycoarray; human natural antibodies; pregnancy.