Defective influenza viral ribonucleoproteins cause interference

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Influenza viruses possess segmented RNA genomes packaged into ribonucleoproteins (RNPs).
• Defective interfering (DI) virus particles arise during replication and interfere with standard virus propagation.
• The precise nature and role of RNPs in DI virus interference are not fully understood.

Purpose of the Study:

• To characterize the RNP composition of infectious and DI influenza viruses.
• To investigate the interference activity associated with specific RNP fractions.
• To determine if DI RNA within RNPs is the causative agent of interference.

Main Methods:

• Glycerol gradient centrifugation to isolate RNP fractions.
• Polyacrylamide gel electrophoresis (PAGE) to analyze RNA content of RNPs.
• Infectious center reduction assay to measure interference activity.
• RNase sensitivity assays to confirm RNA's role in interference.

Main Results:

• Three major RNP peaks (I, II, III) were identified in both infectious and DI influenza viruses.
• Peak III RNP was enriched in DI virus preparations and contained characteristic DI RNA segments.
• Only Peak III RNP from DI virus exhibited significant interference activity, which was RNase sensitive.
• Interfering RNPs were heterogeneous and migrated slower than M and NS gene-containing RNPs.

Conclusions:

• DI RNA, packaged within specific DI RNPs (Peak III), is the primary agent responsible for interference.
• DI RNPs play a crucial role in the phenomenon of defective interference in segmented, negative-stranded RNA viruses.
• These findings elucidate the molecular basis of interference mediated by DI particles in influenza virus.