IL6 and COVID-19: Despite the lymphopenia and general trend of promoted inflammation that are important features of severe COVID-19 [56,67], the subtle changes in individual cytokines/chemokines in infected AAV/hACE2 mice are also comparable to those in patients, such as the increase of TNF-α, IL-6, CCL2, and CCL3 in the circulation (Fig 5) [4,60,68].