TNF and COVID-19: As TNF-α is one of the most elevated cytokines, with IL-6 and IL-8, in the cerebrospinal fluid of COVID-19 patients [39], the influence of this inflammatory cytokine in modulating the viral entry was investigated using qRT-PCR targeting the viral gene E. The relative amount of gene E was significantly lower when SH-SY5Y cells were exposed to 10 ng/mL of TNF-α concomitantly with the inoculum (one-way ANOVA, 5.6 ± 2.9 vs. 24.0 ± 3.5, p < 0.01) (Figure S1B).