Inhibition of SARS-CoV-2 by type I and type III interferons

Abstract

The recently emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of the devastating COVID-19 lung disease pandemic. Here, we tested the inhibitory activities of the antiviral interferons of type I (IFN-α) and type III (IFN-λ) against SARS-CoV-2 and compared them with those against SARS-CoV-1, which emerged in 2003. Using two mammalian epithelial cell lines (human Calu-3 and simian Vero E6), we found that both IFNs dose-dependently inhibit SARS-CoV-2. In contrast, SARS-CoV-1 was restricted only by IFN-α in these cell lines. SARS-CoV-2 generally exhibited a broader IFN sensitivity than SARS-CoV-1. Moreover, ruxolitinib, an inhibitor of IFN-triggered Janus kinase/signal transducer and activator of transcription signaling, boosted SARS-CoV-2 replication in the IFN-competent Calu-3 cells. We conclude that SARS-CoV-2 is sensitive to exogenously added IFNs. This finding suggests that type I and especially the less adverse effect-prone type III IFN are good candidates for the management of COVID-19.

Keywords: COVID-19; SARS–CoV-2; antiviral agent; cytokine action; infection; innate immunity; interferon; interferon-alpha/beta; interferon-lambda; ruxolitinib; virology; virus.

Figure 1.

Sensitivity of SARS–CoV-2 and SARS–CoV-1 to type I IFN dose escalation. Calu-3 (A) and Vero E6 cells (B) were pretreated with recombinant human IFN-α and infected at an MOI of 0.01. Titers were measured at 24 h postinfection by plaque assay. Individual titers (dots) and geometric mean values (bars) from three biological replicates are shown. Log-transformed titers of each virus dose-response experiment were analyzed by Spearman's exact rank correlation test. CC and exact one-sided p values are provided. Note that titer values that were below the plaque assay detection level (50 PFU/ml; indicated by the dashed line) were set to 1 PFU/ml.

Figure 2.

Sensitivity of SARS–CoV-2 and SARS–CoV-1 to intermediate-dose type I IFN. Calu-3 (A) and Vero E6 cells (B) were pretreated with 100 units/ml IFN-α, infected at an MOI of 0.01, and titrated 24 h later. Log-transformed data were analyzed by two-way ANOVA with factors “IFN” and “virus,” for each of which the specific p values are indicated. p (interaction) designates the probability that IFN sensitivity depends on the virus species. Data points and geometric mean values from six independent experiments are shown. Note that three of the six biological repeats are repeats from Fig. 1.

Figure 3.

Sensitivity of SARS–CoV-2 and SARS–CoV-1 to type III IFN. A, experiments were performed as described for Fig. 1, except that recombinant human IFN-λ was used. Log-transformed titers of each virus dose-response experiment with concentrations of 10 and 100 ng/ml IFN-λ were analyzed by Spearman's exact rank correlation test. CCs and exact one-sided p values are provided. B, three additional biological replicates of the 10 ng/ml IFN-λ were performed, and the resulting titer data were pooled with the 10 ng/ml IFN-λ data from A. Log-transformed titers were analyzed by unpaired one-tailed Student's t test. n.s., nonsignificant.

Figure 4.

Effect of the JAK/STAT inhibitor ruxolitinib on SARS–CoV-2 replication. Calu-3 (A) and Vero E6 (B) cells were pretreated with 1 μm ruxolitinib (Rux) and infected with SARS–CoV-2 at an MOI of 0.01, and titers were determined at 24 and 48 h postinfection. Individual titers (dots) and geometric mean values (bars) from three biological replicates are shown. Log-transformed titers were analyzed by unpaired two-tailed Student's t test. n.s., nonsignificant.

Figure 5.

Effect of IFNs and ruxolitinib on Calu-3 and Vero E6 cells. Calu-3 and Vero E6 cells were incubated with the indicated amounts of IFNs and ruxolitinib (added 1 h before IFN) and 24 h later were analyzed for the indicated antigens using immunoblotting. The data are representative of three independent experiments. Molecular markers are shown on the left sides of the blots.