Engineering temperature sensitive live attenuated influenza vaccines from emerging viruses

Area of Science:

• Virology
• Vaccine Development
• Molecular Biology

Background:

• Licensed live attenuated influenza A vaccines (LAIVs) are reassortants combining genes from master donor and circulating strains.
• Rapid recombinant virus technologies enable engineering LAIV candidates directly from patient specimens.
• Temperature-sensitive (ts) mutations are crucial for the attenuation phenotype of cold-adapted LAIV master donor strains.

Purpose of the Study:

• To engineer alternative LAIV candidates with genomes entirely from pandemic or seasonal strains.
• To introduce specific temperature-sensitive mutations into pandemic H1N1 influenza A virus strains.
• To evaluate the attenuation, replication, and protective efficacy of these engineered LAIV candidates.

Main Methods:

• Introduction of multiple temperature-sensitive mutations (e.g., PB1-K391E, D581G, A661T; PB2-P112S, N265S, N556D, Y658H) into pandemic H1N1 strains (rNY1682-WT) to create rNY1682-TS1 and rNY1682-TS2.
• Assessment of viral replication in vitro at different temperatures (30°C, 33°C, 39°C).
• Evaluation of clinical symptoms, lung virus replication, and protective efficacy in mice challenged with virulent influenza A viruses.

Main Results:

• Engineered viruses rNY1682-TS1 and rNY1682-TS2 exhibited efficient replication at lower temperatures but were restricted at 39°C.
• rNY1682-TS2 showed complete restriction at 39°C and demonstrated enhanced protective efficacy against homologous and heterologous H1N1 challenges in mice compared to licensed LAIV.
• Introduction of TS1 or TS2 mutations into a distantly related seasonal H1N1 virus also resulted in significant in vitro replication restriction.

Conclusions:

• Engineering specific temperature-sensitive mutations into influenza A virus genomes effectively attenuates divergent human virus lineages.
• This strategy provides an alternative method for generating novel live attenuated influenza vaccines (LAIVs).
• The engineered rNY1682-TS2 candidate shows promise as a more protective LAIV.