Antiviral activity of chloroquine against human coronavirus OC43 infection in newborn mice

Abstract

Until recently, human coronaviruses (HCoVs), such as HCoV strain OC43 (HCoV-OC43), were mainly known to cause 15 to 30% of mild upper respiratory tract infections. In recent years, the identification of new HCoVs, including severe acute respiratory syndrome coronavirus, revealed that HCoVs can be highly pathogenic and can cause more severe upper and lower respiratory tract infections, including bronchiolitis and pneumonia. To date, no specific antiviral drugs to prevent or treat HCoV infections are available. We demonstrate that chloroquine, a widely used drug with well-known antimalarial effects, inhibits HCoV-OC43 replication in HRT-18 cells, with a 50% effective concentration (+/- standard deviation) of 0.306 +/- 0.0091 microM and a 50% cytotoxic concentration (+/- standard deviation) of 419 +/- 192.5 microM, resulting in a selectivity index of 1,369. Further, we investigated whether chloroquine could prevent HCoV-OC43-induced death in newborn mice. Our results show that a lethal HCoV-OC43 infection in newborn C57BL/6 mice can be treated with chloroquine acquired transplacentally or via maternal milk. The highest survival rate (98.6%) of the pups was found when mother mice were treated daily with a concentration of 15 mg of chloroquine per kg of body weight. Survival rates declined in a dose-dependent manner, with 88% survival when treated with 5 mg/kg chloroquine and 13% survival when treated with 1 mg/kg chloroquine. Our results show that chloroquine can be highly effective against HCoV-OC43 infection in newborn mice and may be considered as a future drug against HCoVs.

Figures

FIG. 1.

Time-dependent antiviral effect of chloroquine on HCoV-OC43 replication in HRT-18 cells. HCoV-OC43-infected HRT-18 cells were treated with 10 μM chloroquine at the time of infection or at different time points thereafter (•). The virus control represents HCoV-OC43-infected cells incubated with medium (▪). The background (▾) represents the residual viral load that was detected after washing the cells. Twenty-eight hours after infection, cell supernatants were collected and viral RNA was extracted and quantified by qRT-PCR. Data are mean values ± standard errors of the means from two independent experiments performed in duplicate.

FIG. 2.

Survival curves for newborn mice after HCoV-OC43 infection. Newborn mice were infected intracerebrally with 103 HCoV-OC43 copies, and mother mice were treated subcutaneously with 1, 5, or 15 mg/kg chloroquine (CQ) prepartum (A) or postpartum (B). N represents the number of mother mice per group, and n represents the number of newborn mice per group.

FIG. 3.

Survival curves for newborn mice after HCoV-OC43 infection. Five-day-old suckling mice were infected intracerebrally with 103 HCoV-OC43 copies and did or did not receive chloroquine (CQ) either via the placenta or via maternal milk. N represents the number of mother mice per group, and n represents the number of newborn mice per group.