Corrigendum: Antiviral and Immunomodulatory Effects of Pelargonium sidoides DC. Root Extract EPs® 7630 in SARS-CoV-2-Infected Human Lung Cells (Front. Pharmacol., (2021), 12, (2871), 10.3389/fphar.2021.757666)

Abstract

In the original article, there was a mistake in Figure 2 as published. The legend for Figure 2A was missing in an updated version of the figure after proofs. In addition, a minor mistake was corrected in Figure 6 (CXCL1 y-axis tick numbers partially covered by neighboring graph). The corrected Figure 2 and Figure 6 appear below. In the original article, there was an error. The term “virus entry” was used instead of “virus propagation” as intended. A correction has been made to the section “EPs 7630 and Distinct Fractions Limit Immune Gene Expression but Enhance Anti-inflammatory TNFAIP3 Induction,” paragraph 1. “Apart from inhibiting virus entry, EPs 7630 has immunomodulatory effects (Noldner and Schotz, 2007; Peric et al., 2021) that might be beneficial for counteracting virus infections and preventing inflammation and immune dysregulation (cytokine storm), which is associated with high COVID-19 morbidity and mortality. The variable SARS-CoV-2 inhibition of the different EPs 7630 fractions (Figure 4B) encouraged us to compare immunomodulatory effects of EPs 7630 and its fractions in SARS-CoV-2-infected Calu-3 cells. Whereas EPs 7630 or its fractions (each 100 μg/ml) alone (Figure 5, green bar; Supplementary Figure S7) had nomajor effects on pro-inflammatory (CCL5, IL6, IL1B), IFN-dependent (IFNB1, IFIT1, MX1), or antiinflammatory (TNFAIP3) gene expression, SARS-CoV-2 infection resulted in 10 to 100-fold increased expression of all genes except TNFAIP3 at 48 h post-infection (Figure 5, red bars). EPs 7630 treatment post-SARS-CoV-2 infection resulted in a significant reduction of IL1B gene expression and strong upregulation of anti-inflammatory TNFAIP3. All other genes showed a limited but non-significant decrease in gene activation suggesting either limited transcriptional regulation or restoration of mRNA levels late in infection. Notably, reduced virus growth as a consequence of entry inhibition (see Figures 2, 4) might also generally limit the SARS-CoV-2-induced upregulation of immune genes. Still, the low molecular weight fractions <1 and 1-3 kDa, which had limited effects on virus propagation using 100 μg/ml (see Figure 4B), resembled EPs 7630-dependent gene regulation patterns with the strongest effects on IL1B and TNFAIP3 during SARS-CoV-2 infection. The 4 fractions between 3 and >30 kDa had minor effects on anti-inflammatory TNFAIP3, but strong inhibitory effects on most of the proinflammatory and IFN-dependent genes. The differential gene activation patterns might be explained by the composition of the fractions containing gallocatechins, benzopyranones such as umckalin and umckalin sulfate, and purine derivatives in the two low molecular weight fractions, and increasing amounts of di-, tri-, hexa-, oligo-, and polymeric prodelphinidins in the high molecular weight fractions (Table 1).” In the original article, there was a mistake in the legend for Figures 2, 4-6 as published. A copy-paste error was detected for p value definitions (definition for “****” is accidentally labeled with “*”). The correct legends for Figure 2 and Figure 6 appear in the new figures. The correct legends for Figure 4 and Figure 5 appear below. FIGURE 4 | EPs 7630 molecular fractions differentially inhibit SARS-CoV-2 propagation. (A) Infection of Calu-3 cells with SARS-CoV-2-Spike VSVpp (SARS-CoV-2-S) or VSV-G as control was done in the presence of compounds for 30 min at 4°C at 500 × g followed by 1-h incubation at 37°C. Cell lysates were prepared after 24 h and the luciferase signal was measured using a multi-mode 96-well plate reader. Bars represent mean values and SD from n = 5-8 biological samples from two independent experiments. Technical outliers were removed from the analysis. (B) Calu-3 cells were infected with SARS-CoV-2 (MOI = 0.0005) and treated with fractions of ultrafiltrated EPs 7630 simultaneously. Virus-containing supernatants were collected 48 h post-infection and viral titers were determined as plaque-forming units (PFU)/ml by plaque titration assay. Data are derived from n = 3 biological samples (for <30 kDa 66 μg/ml, 5-10 kDa 33 μg/ ml, 1-3 kDa 33 μg/ml, and <1 kDa 33 μg/ml: n = 2). Vehicle = medium. Statistical significance (treatment vs. vehicle) is indicated by (*) as determined by two-way (A) or one-way (B) ANOVA with Dunnett’s multiple comparison testing. Asterisks are shown only for significantly different data sets in comparison to vehicle treatment. (*) = p < 0.05; (**) = p < 0.01; (***) = p < 0.001; (****) = p < 0.0001. FIGURE 5 | Calu-3 cells treated with EPs 7630 or ultrafiltrated fractions show enhanced anti-inflammatory responses during SARS-CoV-2 infection. Calu-3 cells were treated with EPs 7630 (100 μg/ml), infected with SARS-CoV-2 (MOI = 0.0005; vehicle), or a combination of both. Additionally, cells were treated with ultrafiltrated fractions of EPs 7630 and infected with SARSCoV- 2. Cell lysates were prepared 48 h post-infection and cellular RNA of the indicated immune genes was quantified by RT-qPCR. Green bars show EPs 7630-treated, non-infected cells for comparison. Vehicle = medium. Data are derived from n = 3 biological samples and are presented as fold gene expression relative to untreated cells and normalized to reference gene expression (TBP). Statistical significance in samples from SARS-CoV-2 infected cells (treatment vs. vehicle) is indicated by (*) as determined by twoway ANOVA with Dunnett’s multiple comparison testing. (*) = p < 0.05; (**) = p < 0.01; (***) = p < 0.001; (****) = p < 0.0001. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.