A. Western blot showing the absence of SIRT5 and SIRT1 in SIRT5- and SIRT1-KO A549-ACE2 cells, after CRISPR knockout. B. Decrease in cell-associated viral mRNA levels in SIRT5- and SIRT1-KO cells infected with SARS-Cov-2 for 3 days at MOI = 0.1 or MOI = 1, as shown by RT-qPCR. Data show fold-changes compared to WT levels at MOI = 0.1. n = 4. C. Decrease in viral titers in SIRT5- and SIRT1-KO cells infected with SARS-Cov-2 for 3 days at MOI = 1, as shown by plaque assay. n = 4. D. Absence of cytotoxicity in A549-ACE2 cells treated with Sirt5-i and Ex-527 inhibitor, as measured by flow cytometry. n = 4. E. Decrease in cell-associated viral mRNA levels in A549-ACE2 cells infected with SARS-Cov-2 for 3 days at MOI = 0.1, and treated with SIRT5 and SIRT1 inhibitors Sirt5-i and Ex-527, as shown by RT-qPCR. Data show fold-change compared to DMSO-treated levels. n = 6. F. Decrease in viral titers in A549-ACE2 cells infected with SARS-Cov-2 for 3 days at MOI = 0.1, and treated with SIRT5 and SIRT1 inhibitors Sirt5-i and Ex-527, as shown by plaque assay. n = 9. G/H. Same as E. (with n = 4), and F. (n = 6), using Calu3 cells. B-H. Data show mean and standard error of the mean (SEM) between biological replicates. RT-qPCR results were internally normalized with GAPDH and ACTIN reference genes. Viral titers after plaque assay are expressed in log-transformed PFU (plaque-forming unit) per mL of supernatant. Asterisks summarize the results of one-way ANOVAs followed by Holm–Šidák multiple comparisons test (on log-transformed data for plaque assays) *: p < 0.05, **: p < 0.01, ***: p < 0.001, ****: p < 0.0001.