Respiratory Delivery of Highly Conserved Antiviral siRNAs Suppress SARS-CoV-2 Infection

Area of Science:

• Virology
• Immunology
• RNA Therapeutics

Background:

• COVID-19 poses a global health challenge, with over 777 million cases and 7 million deaths.
• Current vaccines are less effective in immunocompromised populations, necessitating alternative antiviral treatments.
• Highly conserved regions of SARS-CoV-2 are attractive targets for novel antiviral therapies.

Purpose of the Study:

• To evaluate the in vitro antiviral efficacy of four conserved anti-COVID small interfering RNAs (siRNAs).
• To investigate the direct in vivo delivery of naked siRNAs to the respiratory tract via intranasal instillation.
• To provide proof-of-concept for siRNA-based respiratory viral suppression.

Main Methods:

• siRNAs targeting conserved SARS-CoV-2 regions (ORF1a-Nsp1, Membrane, Nucleocapsid) were designed and tested in vitro.
• Dose-response analysis determined half-maximal inhibitory concentrations (IC50) for siRNAs.
• Naked siRNAs were administered intranasally to K18-hACE2 transgenic mice infected with SARS-CoV-2.

Main Results:

• siRNAs demonstrated potent antiviral activity in vitro, with IC50 values ranging from 0.02 nM to 0.9 nM.
• Intranasal administration of siRNA-18 significantly reduced viral mRNA levels and disease severity in a mouse model.
• Chemical modification (2'-O-methyl-AS456) of siRNA-30 minimized off-target immune activation while maintaining antiviral efficacy.

Conclusions:

• Direct intranasal administration of naked siRNAs is a feasible method for in vivo respiratory viral suppression.
• Utilizing conserved target sequences enhances siRNA efficacy against SARS-CoV-2.
• Chemical modification of siRNAs can improve therapeutic safety by reducing unintended immune responses.