2  Antiviral properties of chloroquine
In vitro, chloroquine appears as a versatile bioactive agent reported to possess antiviral activity against RNA viruses as diverse as rabies virus [16], poliovirus [17], HIV [12,[18], [19], [20], hepatitis A virus [21,22], hepatitis C virus [23], influenza A and B viruses [24], [25], [26], [27], influenza A H5N1 virus [28], Chikungunya virus [29], [30], [31], Dengue virus [32,33], Zika virus [34], Lassa virus [35], Hendra and Nipah viruses [36,37], Crimean–Congo hemorrhagic fever virus [38] and Ebola virus [39], as well as various DNA viruses such as hepatitis B virus [40] and herpes simplex virus [41].The antiviral properties of chloroquine described in vitro have sometimes been confirmed during treatment of virus-infected patients but have not always been reproduced in clinical trials depending on the disease, the concentration of chloroquine used, the duration of treatment and the clinical team in charge of the trial.
Regarding coronaviruses, the potential therapeutic benefits of chloroquine were notably reported for SARS-CoV-1 [11,42]. Chloroquine was also reported to inhibit in vitro the replication of HCoV-229E in epithelial lung cell cultures [43,44]. In 2009, it was reported that lethal infections of newborn mice with the HCoV-O43 coronavirus could be averted by administering chloroquine through the mother's milk. In vitro experiments also showed a strong antiviral effect of chloroquine on a recombinant HCoV-O43 coronavirus [45]. Although chloroquine was reported to be active against Middle East respiratory syndrome coronavirus (MERS-CoV) in vitro [46], this observation remains controversial [47].