Cloned defective interfering influenza virus protects ferrets from pandemic 2009 influenza A virus and allows protective immunity to be established.
Authors: Dimmock Nigel J, Dove Brian K, Scott Paul D, Meng Bo, Taylor Irene, Cheung Linda, Hallis Bassam, Marriott Anthony C, Carroll Miles W, Easton Andrew J
Journal: PloS one
Summary
# Editorial Summary: Defective Interfering Influenza Virus as a Novel Protective Strategy Pandemic influenza poses significant respiratory and systemic challenges across multiple species, including horses, yet current control measures through vaccination and antivirals have recognised limitations. Researchers investigated whether cloned defective interfering (DI) influenza A virus—specifically 244 DI RNA, engineered with a large deletion in segment 1 that confers antiviral properties—could provide protective immunity when administered intranasally to ferrets prior to exposure with pandemic H1N1 (A/California/04/09). A single intranasal dose of either 2 or 0.2 µg of 244 DI RNA delivered as A/PR/8/34 virus particles substantially reduced fever, weight loss, respiratory symptoms, and infectious viral load compared to controls; notably, the 244 DI RNA amplified in nasal secretions following challenge, indicating active replication at the site of infection. Despite attenuated clinical disease, treated ferrets developed robust serum haemagglutination-inhibiting antibodies specific to A/Cal and demonstrated solid immunity upon rechallenge, demonstrating that DI virus administration does not compromise adaptive immune responses. For equine practitioners, these findings suggest potential therapeutic applications for influenza control strategies, particularly given that DI viruses may offer protection across influenza A subtypes whilst simultaneously allowing immunological priming—offering a mechanistically distinct approach to conventional vaccines and antivirals that warrants investigation in equine models.
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Practical Takeaways
- •This research demonstrates proof-of-concept for defective interfering viruses as a novel antiviral therapy for influenza; potential future application as an alternative to traditional vaccines and antivirals with broad-spectrum activity across influenza A subtypes
- •The approach allows protective immunity to develop despite viral attenuation, suggesting DI viruses could function as therapeutic antivirals without compromising subsequent vaccination or natural immunity
- •While tested in ferrets (a human disease model), this approach may have future applications in controlling influenza outbreaks in horses and other domestic animals mentioned as susceptible to influenza
Key Findings
- •Intranasal administration of cloned defective interfering (DI) RNA derived from influenza segment 1 protected ferrets from pandemic A/California/04/09 (H1N1) virus infection
- •Single dose treatment with 244 DI virus significantly reduced fever, weight loss, respiratory symptoms, and infectious viral load in infected ferrets
- •Despite disease attenuation by DI virus treatment, ferrets developed high levels of A/Cal-specific serum antibodies and remained solidly immune to viral rechallenge
- •244 DI RNA was amplified in nasal washes following infection, indicating active replication consistent with clinical protection