TNF and COVID-19: Inflammatory factors, such as IL-6, TNF-ɑ, and MCP1, have been reported to be elevated in COVID-19 patients and models.18 In the present study, we also detected increased levels of IL-6, TNF-ɑ, and MCP1 in the brain of infected K18-hACE2 mice and hamsters by RT-PCR (Fig. 2g).