(719b) Quantification of Interactions Between Viruses and Their Defective Interfering Particles

When a virus infects a susceptible host cell, it hijacks the cell’s biosynthetic machinery and resources to produce progeny virus. Infected cells may also produce virus-like particles that carry genetic material but are unable to further infect cells.  One class of such virus-like particles are defective interfering particles (DIPs), which carry a defective viral genome that renders them unable to reproduce in living cells.  However, when DIPs co-infect a cell with viable virus, they can interfere with virus production. Their ability to interfere with or attenuate normal viral infections makes DIPs a useful tool to probe virus-cell interactions and potentially treat viral infections.  These features provide motivation to develop quantitative measures to better understand how DIP and virus particles interact.  As a model system, we study the behavior of vesicular stomatitis virus (VSV) and its DIPs when cultured on baby hamster kidney (BHK21) cells.  VSV is a negative-sense single-stranded RNA virus related to rabies, ebola and respiratory syncytial virus, but it is non-pathogenic to humans and it has served as a prototype for the study of virus-DIP interactions.  Here we show how measures of virus and virus-like particle counts and activity level can be integrated to gain insight into the mechanism of infection interference.  More broadly, our results show that non-infectious byproducts of infection can nevertheless have important consequences for the growth and spread of viruses.