Effects of Sialic Acid Modifications on Virus Binding and Infection

Abstract

Sialic acids (Sias) are abundantly displayed on the surfaces of vertebrate cells, and particularly on all mucosal surfaces. Sias interact with microbes of many types, and are the targets of specific recognition by many different viruses. They may mediate virus binding and infection of cells, or alternatively can act as decoy receptors that bind virions and block virus infection. These nine-carbon backbone monosaccharides naturally occur in many different modified forms, and are attached to underlying glycans through varied linkages, creating significant diversity in the pathogen receptor forms. Here we review the current knowledge regarding the distribution of modified Sias in different vertebrate hosts, tissues, and cells, their effects on viral pathogens where those have been examined, and outline unresolved questions.

Keywords: inhibitor.; modification; receptor; sialic acids; virus.

Figure 1

Modified Sialic Acids. (A) Diverse glycan forms exist at the cell surface in both bound and secreted (or free) forms. Sias predominantly terminate carbohydrate chains, while encompassing their own chemical diversity. Reprinted from , with permission. (B) Sias are diverse structures, including modified forms induced by enzymatic functions that vary between species, tissues, and even individual cells. Representative hydroxylation and acetylations discussed in this review are shown on the base Sia (Neu5Ac) chemistry. We note the known (and unknown) encoded-enzymes that modify the CMP-Sia precursor molecule.