Silencing of SARS-CoV-2 with modified siRNA-peptide dendrimer formulation

Background

First vaccines for prevention of Coronavirus disease 2019 (COVID‐19) are becoming available but there is a huge and unmet need for specific forms of treatment. In this study we aimed to evaluate the anti‐SARS‐CoV‐2 effect of siRNA both in vitro and in vivo.

Methods

To identify the most effective molecule out of a panel of 15 in silico designed siRNAs, an in vitro screening system based on vectors expressing SARS‐CoV‐2 genes fused with the firefly luciferase reporter gene and SARS‐CoV‐2‐infected cells was used. The most potent siRNA, siR‐7, was modified by Locked nucleic acids (LNAs) to obtain siR‐7‐EM with increased stability and was formulated with the peptide dendrimer KK‐46 for enhancing cellular uptake to allow topical application by inhalation of the final formulation – siR‐7‐EM/KK‐46. Using the Syrian Hamster model for SARS‐CoV‐2 infection the antiviral capacity of siR‐7‐EM/KK‐46 complex was evaluated.

Results

We identified the siRNA, siR‐7, targeting SARS‐CoV‐2 RNA‐dependent RNA polymerase (RdRp) as the most efficient siRNA inhibiting viral replication in vitro. Moreover, we showed that LNA‐modification and complexation with the designed peptide dendrimer enhanced the antiviral capacity of siR‐7 in vitro. We demonstrated significant reduction of virus titer and lung inflammation in animals exposed to inhalation of siR‐7‐EM/KK‐46 in vivo.

Conclusions

Thus, we developed a therapeutic strategy for COVID‐19 based on inhalation of a modified siRNA‐peptide dendrimer formulation. The developed medication is intended for inhalation treatment of COVID‐19 patients.

Avidity of IgG to SARS-CoV-2 RBD as a Prognostic Factor for the Severity of COVID-19 Reinfection

The avidity index (AI) of IgG to the RBD of SARS-CoV-2 was determined for 71 patients with a mild (outpatient) course of COVID-19, including 39 primarily and 36 secondarily reinfected, and 92 patients with a severe (hospital) course of COVID-19, including 82 primarily and 10 secondarily infected. The AI was shown to correlate with the severity of repeated disease. In the group of outpatients with a mild course, the reinfected patients had significantly higher median AIs than those with primary infections (82.3% vs. 37.1%, p < 0.0001). At the same time, in patients with a severe course of COVID-19, reinfected patients still had low-avidity antibodies (median AI of 28.4% vs. 25% in the primarily infected, difference not significant, p > 0.05). This suggests that the presence of low-avidity IgG to RBD during reinfection is a negative prognostic factor, in which a patient’s risk of developing COVID-19 in a severe form is significantly increased. Thus, patients with IgG of low avidity (AI ≤ 40%) had an 89 ± 20.5% chance of a severe course of recurrent COVID-19, whereas the detection of high-avidity antibodies (AI ≥ 50%) gave a probability of 94 ± 7.9% for a mild course of recurrent disease (p < 0.05).

Data on the genome analysis of the wood-rotting fungus Steccherinum ochraceum LE-BIN 3174

In the present article, we report data on the whole-genome sequencing of wood-rotting (white-rot) fungus Steccherinum ochraceum LE-BIN 3174. The S. ochraceum LE-BIN 3174 genome consists of 770 scaffolds (N50 = 62,812 bp) with the total length of assembly ∼35 Mb. The structural annotation of the genome resulted in the prediction of 12,441 gene models, among which 181 were models of tRNA-coding genes, and 12,260 - protein-coding genes. The protein-coding genes were annotated with different databases (Pfam, InterPro, eggNOG, dbCAN, and MEROPS). The whole genome sequence and functional annotation provide an important information for the deep investigation of biochemical processes that take place during the late stages of wood decomposition by Basidiomycetes. The Whole Genome project of S. ochraceum LE-BIN 3174 had been deposited at DDBJ/ENA/GenBank under the accession RWJN00000000. The version described in this work is version RWJN00000000.1. For further interpretation of the data provided in this article, please refer to the research article "Fungal Adaptation to the Advanced Stages of Wood Decomposition: Insights from the Steccherinum ochraceum" [1].

Validation of the method for determining the specific activity of the gel with recombinant endolysin

A method for determining the specific bactericidal activity of the gel with the recombinant modified endolysin of the bacteriophage ECD7 has been developed. Bacterial strains to determine the specific bactericidal activity were selected and acceptance criteria were determined. The developed methodology was validated according to the indicators “Specificity”, “Accuracy” and “Intermediate precision”. The developed method has been successfully validated and is suitable for determining the specific bactericidal activity of a gel with a recombinant modified endolysin.