Natural Killer cell activation, reduced ACE2, TMPRSS2, cytokines G CSF, M CSF and SARS CoV 2 S pseudovirus infectivity by MEK inhibitor treatment of human cells.

COVID-19 affects vulnerable populations including elderly individuals and patients with cancer. Natural Killer (NK) cells and innate-immune TRAIL suppress transformed and virally-infected cells. ACE2, and TMPRSS2 protease promote SARS-CoV-2 infectivity, while inflammatory cytokines IL-6, or G-CSF worsen COVID-19 severity. We show MEK inhibitors (MEKi) VS-6766, trametinib and selumetinib reduce ACE2 expression in human cells. Chloroquine or hydroxychloroquine increase cleaved active SP-domain of TMPRSS2, and this is potentiated by MEKi. In some human cells, remdesivir increases ACE2-promoter luciferase-reporter expression, ACE2 mRNA and protein, and ACE2 expression is attenuated by MEKi. We show elevated cytokines in COVID-19- (+) patient plasma (N=9) versus control (N=11). TMPRSS2, inflammatory cytokines G-CSF, M- CSF, IL-1a, IL-6 and MCP-1 are suppressed by MEKi alone or in combination with remdesivir. MEKi enhance NK cell (but not T-cell) killing of target-cells, without suppressing TRAIL-mediated cytotoxicity. We generated a pseudotyped SARS-CoV-2 virus with a lentiviral core but with the SARS-CoV-2 D614 or G614 SPIKE (S) protein on its envelope and used VSV-G lentivirus as a negative control. Our results show infection of human bronchial epithelial cells or lung cancer cells and that MEKi suppress infectivity of the SARS-CoV-2-S pseudovirus following infection. We show a drug class-effect with MEKi to promote immune responses involving NK cells, inhibit inflammatory cytokines and block host-factors for SARS-CoV-2 infection leading also to suppression of SARS-CoV-2-S pseudovirus infection of human cells in a model system. MEKi may attenuate coronavirus infection to allow immune responses and antiviral agents to control COVID-19 disease progression and severity.