Defective interfering passages of Sindbis virus: chemical composition, biological activity, and mode of interference

Area of Science:

• Virology
• Molecular Biology

Background:

• Defective interfering (DI) particles are variants of standard viruses that arise during serial propagation.
• Sindbis virus (SV) is a well-characterized alphavirus model system.

Purpose of the Study:

• To characterize the biophysical and molecular properties of Sindbis virus DI particles.
• To investigate the impact of DI particle coinfection on host cell and viral gene expression and replication.

Main Methods:

• Serial passage of Sindbis virus and isolation of defective interfering particles.
• Analysis of virion RNA and proteins using polyacrylamide gel electrophoresis.
• Co-infection experiments in cell culture and analysis of intracellular viral RNA and protein synthesis.

Main Results:

• Sindbis virus DI particles cosediment with and share buoyant density with standard virus.
• Late passage virion RNA is heterogeneous, while early passage RNA is homogeneous; virion proteins are similar.
• Co-infection with DI particles inhibits virus production by over 90% but does not reduce total intracellular viral RNA and protein synthesis.
• DI particle co-infection leads to the synthesis of two new intracellular RNA species and a new intracellular protein, while blocking nucleocapsid assembly and reducing capsid protein by 50%.

Conclusions:

• Sindbis virus DI particles possess distinct molecular characteristics, including altered RNA composition.
• DI particles interfere with viral replication by disrupting nucleocapsid assembly and altering protein synthesis, leading to significantly reduced virus production.