CD40LG and COVID-19: All subjects are monitored for safety (adverse events/severe adverse events), COVID-19 symptoms, SARS-Cov-2 virus test, blood SARS-Cov-2 IgM and IgG antibodies tests, blood cytokine and inflammatory (CRP, IL_6, IL-10, TNFα) tests and disease severity evaluation for 6 months after the last dose of AdMSC infusion for the study group and 6 months after the enrollment for the control group.