Combined prophylactic and therapeutic use maximizes hydroxychloroquine anti-SARS-CoV-2 effects in vitro

Nicola Clementi; Elena Criscuolo; Roberta Antonia Diotti; Roberto Ferrarese; Matteo Castelli; Roberto Burioni; Massimo Clementi; Nicasio Mancini

The two molecules were tested using different experimental protocols, and virus adsorption was performed at both 37°C and 4°C. CPE was assessed at 72 hpi ( Fig. 1 and 2) . Virus infection positive control showed marked effects on cell morphology at 37°C as well as 4°C adsorption conditions. HCQ was effective in full-time treatment at both adsorption temperatures, and in post-adsorption treatment only when the virus was added to cells for 1 h at 4°C. The molecules did not show the same degree of protection from CPE in pre-adsorption treatment at both adsorption temperatures, as well as in post-adsorption treatment at 37°C adsorption. BFLA was tested as control of inhibition of viral infectivity at a phagolysosome level in a pre-adsorption treatment, showing full CPE protection at 37°C virus adsorption, while only partial protection was observed when the virus was added to cells at 4°C (Fig. 2) . No drug-related cytotoxic effect was observed on uninfected cells, in all experimental settings (data not shown).