Intranasal type I interferon treatment is beneficial only when administered before clinical signs onset in the SARS-CoV-2 hamster model

Abstract

Impaired type I interferons (IFNs) production or signaling have been associated with severe COVID-19, further promoting the evaluation of recombinant type I IFNs as therapeutics against SARS-CoV-2 infection. In the Syrian hamster model, we show that intranasal administration of IFN-α starting one day pre-infection or one day post-infection limited weight loss and decreased viral lung titers. By contrast, intranasal administration of IFN-α starting at the onset of symptoms three days post-infection had no impact on the clinical course of SARS-CoV-2 infection. Our results provide evidence that early type I IFN treatment is beneficial, while late interventions are ineffective, although not associated with signs of enhanced disease.

Fig 1. Impact of IFN-α treatment on Mx1 lung transcript and protein levels in non-infected hamsters.

(A) Syrian hamsters were treated intranasally either with placebo or with 10⁵ IU recombinant universal IFN-α (IFN). Tissues were harvested at day 1 post-treatment. Transcripts levels of Mx1 relative to the housekeeping genes RPL18 and RPS6KB1 were determined by RT-qPCR. Results are expressed as means ± SEM. Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test. (B-D) Syrian hamsters were treated intranasally either with placebo or with 10⁵ UI IFN or with 7.10⁵ IU IFN. Tissues were harvested either at day 1 or day 2 post-treatment. (B) Lung transcripts levels of Mx1 relative to the housekeeping genes RPL18 and RPS6KB1 determined by RT-qPCR. (C) Representative pictures were selected to display Mx1 lung protein levels detected by immuno-chemistry (IHC). Scale bar: 100μm. (D) Quantification of percent lung area positive for Mx1 protein detected by IHC. D0: day 0; D1: day 1; D2; day 2. Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test.

Fig 2. Impact of type I IFN-α treatment on SARS-CoV-2-induced weight loss and viral titers.

(A) Overview study design. (B) Percentage of body weight change with weight measured day 1 pre-infection before the IFN-pre treatment set as the reference weight (6 animals per group). Statistical analysis: two-way ANOVA comparing treatment effects with Geisser-Greenhouse correction followed by Tukey’s multiple comparisons test. (C). Viral genomic RNA in oropharyngeal swabs (6 animals per group). The dotted line indicates limit of detection. (D and E) Lungs viral titers determined by RT-qPCR targeting viral sgRNA relative to the housekeeping genes RPL18 and RPS6KB1 (D) and by TCID₅₀ (E). D2: day 2 post infection; D5: day 5 post infection. Results are expressed as means ± SEM. Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test.

Fig 3. Histopathological analysis of the impact of type I IFN-α treatment.

(A) Representative pictures were selected to display the pathology from haematoxylin and eosin (H&E) stained lung section from animals at day 2 post infection. Scale bar: 100μm. (B) Severity of lung pathology based on lesional scores evaluated from haematoxylin and eosin (H&E) stained lung section. Statistical analysis: Mann-Whitney test. (C) Quantification of percent lung area positive for viral RNA in lung sections stained with RNAScope in situ hybridization (ISH). Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test. (D) Quantification of percent lung area positive for Mx1 protein detected by immunohistochemistry (IHC). Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test. D2: day 2 post infection; D5: day 5 post infection; D15: day 15 post infection. Results are expressed as means ± SEM.

Fig 4. Impact of type I IFN-α treatment on the immune response to SARS-CoV-2.

(A) Lung transcripts levels of Mx1, ISG15, IFN-γ, CXCL10, IL-6 and IL-10 relative to the housekeeping genes RPL18 and RPS6KB1 determined by RT-qPCR. (B) Lung protein levels for CXCL10, IL-6, IL-10 and IL-1β protein levels determined by ELISA or a multiplex assay. (C) Plasmatic protein levels for CCL2 and TNF-α determined by a multiplex assay. D2: day 2 post infection; D5: day 5 post infection; D15: day 15 post infection. Results are expressed as means ± SEM. Statistical analysis: one-way ANOVA with Tukey’s multiple comparisons test.