Function of Molecular Species of Influenza Virus-Binding Sialic Acid and Development of a Sialidase-Based Technique for Detecting Virus

Influenza A virus (IAV)-binding receptors are classified mainly to two molecular species of sialic acids at the terminals of glycoconjugates, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc). We investigated the function of Neu5Gc in IAV infection by using Neu5Gc binding-modified IAVs and Neu5Gc-expressed cells in an Neu5Gc biosynthesis-deficient human cell line. We compared substrate specificity of IAV enzyme sialidase for Neu5Ac and Neu5Gc among human IAVs and equine IAVs. In this review, we introduce our studies about the function of Neu5Gc in IAV infection and substrate specificity of IAV sialidase for Neu5Gc. In addition, we developed a fluorescence imaging technique for detecting IAV and the infected cells using a sialidase imaging probe. The combination use of the probe and anti-influenza drugs enabled selective detection and isolation of drug-resistant IAVs. In this review, we also introduce our recent studies about virus detection using the sialidase imaging probe and its applications.