ADNKA overcomes SARS-CoV2-mediated NK cell inhibition through non-spike antibodies

SARS-CoV-2 antagonises the cellular interferon response, but whether the virus manipulates cellular immunity is unclear. An unbiased proteomic approach to determine how cell surface protein expression is altered on SARS-CoV-2-infected lung epithelial cells showed downregulation of activating NK cell ligands: B7-H6, MICA, ULBP2, and Nectin1, but no effect on surface MHC-I expression. NK ligand downregulation correlated with a reduction in NK cell activation by infected cells, and was overcome by antibody-dependent NK cell activation (ADNKA). Depletion of spike-specific antibodies confirmed their dominant role in virus neutralisation, but these antibodies played only a minor role in ADNKA compared to antibodies to other viral proteins, including ORF3a, Membrane, and Nucleocapsid. In contrast, ADNKA induced following vaccination was focussed solely on spike, was weaker than ADNKA following natural infection, and was not boosted by the second dose. These insights have important implications for understanding disease progression, vaccine efficacy, and vaccine design.