Azithromycin

Human iSLK.219 cells are latently infected with a recombinant rKSHV.219 virus and contain a doxycycline (Dox)-inducible RTA, constructed and named by Dr. Don Ganem’s lab^{12 (link)}. The rKSHV.219 virus expresses both the red fluorescent protein (RFP) under the control of KSHV lytic PAN promoter and the green fluorescent protein (GFP) under the control of the elongation factor 1 promoter (EF-1α)^{30 (link)}. HEK293T (Human embryonic kidney 293T) cells and KSHV + PEL cell lines, BCP-1 and BCBL-1, were purchased from American Type Culture Collection (ATCC) and cultured as recommended by the manufacturer. The anti-COVID-19 drugs: Azithromycin, Chloroquine diphosphate, Hydroxychloroquine sulfate, Nafamostat mesylate, Remdesivir, and Tocilizumab were purchased from Selleck Chemicals. All the other chemicals if not indicated specifically were purchased from Sigma-Aldrich.

The following antibiotics were used in this study: azithromycin (AZM; Selleck Chemicals), aztreonam (ATM; Azactam), ceftazidime (CAZ; Biovision), ciprofloxacin (CIP; Sigma Aldrich), colistin (CST; Saphhire Biosciences), gentamicin (GEN; Biochemica), tigecycline (TGC; Adooq Bioscience) and tobramycin (TOB; US Pharmacopeia). The β-lactamase inhibitor avibactam (AVI; MedChem Express) was used alone or in combination with ceftazidime (ceftazidime/avibactam; CZA).
azithromycin was dissolved in citric acid (Sigma Aldrich) at a 4:1 w/w ratio in 0.9% sterile saline with pH adjusted to 7.0-7.2 using 3 M NaOH. Other antibiotics were dissolved in sterile water for in vitro experiments or in 0.9% sterile saline (Sigma Aldrich) for in vivo experiments. avibactam was used at a fixed 1:4 w/w ratio with ceftazidime. All antibiotic stock solutions were filter sterilized using 0.22 μm PES membrane syringe filters.

Vero cell (ATCC, CCL-81) was cultured at 37°C in Dulbecco’s modified Eagle’s medium (DMEM, Gibco) supplemented with 10% fetal bovine serum (FBS, Gibco) in the atmosphere with 5% CO₂. Cells were seeded in 96-well plates and cultured overnight with a density of 5 × 10⁴ cells/well prior infection or drug feeding. Remdesivir, Azithromycin, Pralatrexat, Sofosbuvir and Amoxicillin were obtained from Selleck Chemicals. All drugs were dissolved in DMSO to prepare 50 mM stock solutions, and stored at -20°C. DMSO was used in the controls.