Catch, Cut, or Block? Versatile 4-N-Derivatized Sialyl Glycosides for Influenza Virus Neuraminidase Detection and Purification.

Seasonal influenza continues to threaten human lives and pose a significant burden to healthcare systems and the economy, emphasizing the need for developing better influenza vaccines, diagnostics, and antiviral therapeutics. To address these challenges, we generated a library of structurally diverse sialyl glycosides containing 4-N-derivatized sialic acids by a highly efficient one-pot two-enzyme chemoenzymatic sialylation strategy. Sialosides containing 4-azido-substituted sialic acid were selectively cleaved by sialidases from influenza viruses, whereas sialosides containing 4-acetamido-modified sialic acid were resistant to sialidase cleavage. Interestingly, sialosides containing 4-amino- or 4-guanidino-substituted sialic acid were effective inhibitors moderately or highly resistant to cleavage by influenza sialidases (also called neuraminidases). The sialosides containing the 4-guanidino-substituted sialic acid represent a new class of sialidase substrate analog-based inhibitors. We took advantage of this unique property to create a ligand-based approach for efficiently isolating influenza virions from egg allantoic fluid with high purity. Together, these compounds are versatile probes and ligands for developing new approaches to detect, profile, isolate, and characterize influenza viruses via neuraminidases on their surface.