Authors: Blanchard et al

Link to paper:

Journal/ Pre-Print: bioRxiv

Tags: Cell Biology, Molecular biology, Therapeutics

Research Highlights

1. Synthetic mRNA-based platform with Cas13a used to target and mitigate influenza A and SARS-CoV-2.

2. System validated to effectively degrade influenza A and SARS-CoV-2 viral RNA in vitro.

3. System validated to effectively degrade influenza A viral in an in vivo mouse model using nebulizer for mRNA delivery.


Delivery of synthetic mRNA of Cas13a and guide RNAs post-infection is sufficient to target Influenza A Virus polymerase genes and limit viral proliferation in cell-lines and a mouse model. Similar strategy but delivering Cas13A and guide RNAs prior to SARS-CoV-2 infection limits viral copies in a cell line.

Impact for SARS-CoV2/COVID19 research efforts

Possible treatment of SARS-CoV-2 positive individuals.

Study Type

· In vitro study

· In vivo mouse study

Strengths and limitations of the paper


First demonstration that this approach can be used post-infection, how this approach scales with MOI and is functional over a 3-day period.

Standing in the field:

Two studies previously demonstrated ability of Cas13b or d to degrade influenza RNA. mRNA approach previously benchmarked due to not all knockdown of RNA being mediated by Cas13a.

Appropriate statistics:

2-way ANOVA, correct for comparing significant difference between multiple conditions.

Viral model used:

Influenza A and SARS-CoV-2 used for in vitro studies, only influenza A used for in vivo work


Show that can deliver Cas13 mRNA and guides with PBAE-based polymer via nebulizer and this is effective for treating Influenza RNA in mouse model. In vivo testing for SARS-CoV-2 still required.

Main limitations:

· No SARS-CoV-2 in vivo data

· The Cas13a strategy was delivered prior to SARS-CoV-2 infection of a cell line

· Variations in the time post infection guides delivered and RNA levels measured.

· Fig 5: effective guides less effective in initial screen compared to detailed analysis.

· SARS-CoV-2 analysis is a very different set of experiments to that of IVA, looking more at cytopathic effect on cells than anything else.