Selective labeling and visualization of viral and bacterial neuraminidases using <i>ortho</i> -quinone methide-based probes

Neuraminidases (NAs) are critical virulence factors in pathogens. In viruses such as influenza A, neuraminidase facilitates the release of virions, thereby enabling infection propagation. In pathogenic bacteria, NA activity has been linked to the pathogenicity of species such as <i>S. pneumoniae</i>, <i>P. aeruginosa</i>, and <i>V. cholerae</i>. Studies suggest that bacterial NAs play roles in mucus degradation, exposing host epitopes to enhance bacterial adhesion, biofilm formation, and bacterial survival. However, the specific mechanisms by which bacterial NAs contribute to pathogenesis remain poorly understood and largely unknown. To gain a deeper understanding of the molecular mechanisms underlying this class of enzymes, highly selective and sensitive strategies are needed for screening, detecting, and studying active NAs in complex biological samples. Specifically, chemical tools that can covalently label NAs without interfering with their enzymatic activity offer a powerful approach to precisely label and visualize these enzymes in their native environments. In this work, we present the development of novel <i>ortho</i>-quinone methide-based probes featuring an azide and biotin tags for the labeling and detection of NAs. These probes exhibit high selectivity in labeling recombinantly expressed NAs from influenza A virus and pathogenic Gram-negative <i>Prevotella</i> strains at nanomolar concentrations. Moreover, we developed a strategy that significantly improves labeling specificity of NAs when using our probes in complex samples, addressing the common issue of nonspecific labeling associated with quinone methide-based probes. Additionally, we demonstrate the potential of these probes for imaging extracellular NAs on bacterial surfaces, highlighting their utility for studying NAs in their native environments.