Development of mumps virus-specific sialidase imaging probes through chemical modifications of sialic acid

Some viruses, such as mumps virus (MuV), possess sialidases that cleave terminal sialic acids, primarily N-acetylneuraminic acid (Neu5Ac), from glycans. Previously, we developed a sialidase fluorescent imaging probe (BTP3-Neu5Ac) and visualized cells infected with sialidase-expressing viruses. However, BTP3-Neu5Ac could not specifically identify these viruses, as it reacted with a wide range of sialidases from viruses, bacteria, and mammals. Here, to confer specificity of BTP3-Neu5Ac to MuV sialidase, which features a hydrophobic cavity extending toward the C5 position of bound Neu5Ac, we evaluated BTP3-Neu5Ac derivatives containing hydrophobic groups at the C5 position of Neu5Ac moiety across various viral sialidases, including influenza A and B viruses. Linear N-acyl groups with 5-8 carbon atoms at this position improved specificity for MuV sialidase. These derivatives might enable precise identification and diagnosis of MuV infections. Our findings demonstrate that chemical modifications to Neu5Ac in BTP3-Neu5Ac can effectively modulate its specificity for viral sialidases.