Differential of antiviral activity between chloroquine and hydroxychloroquine sulfate against SARS-CoV-2 in vitro.

ABSTRACT

Objective To investigated the in vitro antiviral activity of chloroquine and hydroxychloroquine sulfate against different variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Prototype, Beta, Delta, Omicron) by changing the sequence of drug and virus introduction. Methods Prophylactic treatment Vero E6 cells were treated with Chloroquine or hydroxychloroquine sulfate (200.00, 150.00, 100.00, 50.00, 16.70, 5.55, 1.85, 0.62, 0.21 micromol.L-1) for 1 h, then the virus was added and incubated for another 2 h. The virus-drug mixture was repalced with fresh medium until the end of the experiment. Post-entry treatment Vero E6 cells were incubated with virus for 2 h, then the virus was removed and the cells were cultured with drug-containing medium until the end of the experiment. Full-time treatment Vero E6 cells were pretreated with the drug for 1 h ahead, then virus was added and incubated for another 2 h. The virus-drug mixture was discarded and the cells were cultured with drug-containing medium until the end of the experiment. After 72 h of culture, the cells were observed to see whether they became round and shed to determine the cytopathic situation, and the semi-maximum effect concentration (EC50) and drug selection index (SI) were calculated. Results Both drugs were less effective in preventing SARS-CoV-2. Chloroquine/hydroxychloroquine sulfate showed good antiviral activity under both therapeutic and full-time treatment. EC50 of hydroxychloroquine sulfate was less than chloroquine, SI was greater than chloroquine, antiviral effect of hydroxychloroquine sulfate was better than chloroquine. The antiviral effect of chloroquine (EC50 = 0.904 micromol.L-1) and hydroxychloroquine sulfate (EC50 = 0.143 micromol.L-1) was more significant against Omicron variant than other variants under therapeutic and full-time treatment conditions. Conclusion Chloroquine/hydroxychloroquine sulfate showed good antiviral activity under both therapeutic and full-time treatment, and both drugs were significantly more active against the Omicron variant than the other variants.Copyright © 2023 Authors. All rights reserved.