Figure 4.

Cysteamine and cystamine decreased viral production in Calu-3 cells. (A,B) Calu-3 cells (0.375 × 10⁶ cells/well in 24-well plate) were treated with different doses of cysteamine (panel A) or cystamine (panel B), as indicated, or H₂O as control 1 h before SARS-CoV-2 infection (MOI = 0.1). Absorption of the virus was allowed for 1 h at 37 °C in the presence of different treatments. The unabsorbed virus was removed and replaced by fresh medium with cysteamine, cystamine, or H₂O. Cells were then treated every 24 h and incubated at 37 °C with 5% CO₂ for 48 h when culture medium was collected. Virus yield was measured by back-titration of supernatants as described in the methods. Virus titers are expressed as 50% tissue-culture effective dose (TCID₅₀/mL) values according to the Reed–Muench method. Statistically significant differences between compound- and H₂O-treated cells have been calculated using Wilcoxon matched-pairs rank tests.