Viral ligands for Natural Cytotoxicity Receptors NKp46 and NKp44 (Viral NCR ligands)

Viral ligands for Natural Cytotoxicity Receptors (NCRs) NKp46 and NKp44 are a diverse group of pathogen-encoded proteins that facilitate viral recognition by the innate immune system [NIH, 2021; Frontiers in Immunology, 2019]. The most prominent members include the hemagglutinin (HA) of influenza viruses and the hemagglutinin-neuraminidase (HN) of paramyxoviruses, which bind to specific sialylated O-glycans on the extracellular domains of NKp46 and NKp44 [Blood, 2004; NIH, 2025]. This binding event triggers a signaling cascade in Natural Killer (NK) cells, leading to the release of cytotoxic granules and the lysis of infected cells [NIH, 2021; ACS, 2009]. Beyond influenza, other viral proteins such as the West Nile Virus E protein and poxvirus hemagglutinins also serve as ligands for these receptors [NIH, 2021; PLOS Pathogens, 2010]. Viruses have developed sophisticated evasion mechanisms to disrupt this interaction, such as using viral neuraminidase to remove the essential sialic acids from the NCRs [NIH, 2014; NIH, 2021]. Therapeutic strategies targeting this axis include neuraminidase inhibitors that preserve NK cell recognition and the development of monoclonal antibodies or fusion proteins designed to enhance or mimic these natural immune-activating interactions [NIH, 2021; Frontiers in Immunology, 2019].

Other names

Viral hemagglutininsViral HAViral HNPathogen-derived NCR ligandsNKp46 ligandsNKp44 ligandsViral hemagglutinin-neuraminidase

Binding of viral ligands (such as hemagglutinin) to sialylated residues on the NKp46 and NKp44 receptors triggers NK cell-mediated cytotoxicity and cytokine production against infected cells [NIH, 2021; Blood, 2004].