SARS-CoV-2 viral persistence in lung alveolar macrophages is controlled by IFN-g and NK cells [BALF_BloodNK_SARSWu_NHP]

SARS-CoV-2 RNA generally becomes undetectable in upper airways after a few days or weeks post-infection. It is unclear however if the virus persists in other parts of the body and which mechanism(s) regulate SARS-CoV-2 persistence. We addressed this question in the macaque model. Replication-competent virus was detected in bronchioalveolar lavages (BAL) macrophages beyond 6 months post-infection. SARS-CoV-2 propagated in BAL macrophages from cell-to-cell. IFN-γ inhibited this replication. IFN-γ production within BAL lymphocytes was strongest in NKG2r+CD8+ T and NKG2Alo NK cells and was further increased in NKG2Alo NK cells after Spike protein stimulation. However, IFN-γ production was impaired in NK cells from animals with persisting virus. IFN-γ also enhanced MHC-E expression on BAL macrophages, possibly inhibiting natural killer cell mediated killing. Animals with less persisting virus mounted adaptive NK cells escaping this MHC-E dependent inhibition. Our findings reveal an interplay between NK cells and macrophages mediated by IFN-γ, regulating SARS-CoV-2 persistence in macrophages. Gene expression in bronchoalveolar lavage fluid (BALF) NK cells in SARS-CoV-2 convalescent monkeys. Gene expression profiles in NKG2a/c+ NK cells from BALF of 12 wuhan infected cynomolgus macaques and their blood counterparts at ≥461 days post-infection, based on mRNA counts normalized via the nanoString nCounter System.