Influenza A virus neuraminidase N9 (NA)

Influenza A virus neuraminidase N9 is a critical surface glycoprotein and enzyme found in certain strains of the influenza A virus, most notably the avian-origin H7N9 subtype [1, 10]. It functions as an exo-alpha-sialidase, catalyzing the cleavage of terminal sialic acid residues from host cell receptors and viral glycoproteins [10, 12]. This enzymatic activity is essential for the release of newly formed virions from the surface of infected cells, preventing viral aggregation and facilitating the spread of the infection within the respiratory tract [8, 13]. In addition to its role in viral budding, N9 neuraminidase helps the virus penetrate the mucus layer of the airway by cleaving sialic acids on mucins [12]. As a primary therapeutic target, its active site is the focus of neuraminidase inhibitors like oseltamivir and zanamivir, which arrest viral replication by trapping progeny virions on the host cell [5, 11]. The N9 subtype is of significant public health concern due to its association with highly pathogenic avian influenza outbreaks and its potential for pandemic spread [4, 8]. However, the emergence of drug-resistant mutations, such as the R292K substitution, poses a significant challenge to clinical management and pandemic preparedness [1, 3]. Ongoing surveillance of N9 neuraminidase activity and resistance profiles is vital for the development of next-generation antivirals and vaccines [14, 15].

Other names

NeuraminidaseSialidaseN9 subtypeExo-alpha-sialidaseNA protein

Neuraminidase inhibitors bind to the active site of the N9 enzyme, mimicking the sialic acid substrate. This inhibition prevents the cleavage of sialic acid residues on the host cell surface and viral envelope, thereby trapping newly formed virions on the cell surface and halting the spread of the infection [5, 6, 11].