(105g) Kinetics of Genome Replication During Infection of Host Cells by An RNA Virus

Viruses are a major threat to human health, causing diverse diseases such as the common cold, cancer and AIDS. The earliest stages of viral disease often involve the encounter of a virus particle with susceptible tissues or cells of its host. The virus adsorbs to the surface of a host cell and delivers its genome into the cell, initiating a process that exploits resources of the cell to manufacture hundreds or thousands of virus progeny. We hypothesize that a quantitative and mechanistic understanding of virus growth as an integrated manufacturing process will advance the development of new anti-viral strategies and biomedical applications of viruses. As a model system, we study vesicular stomatitis virus (VSV), an RNA virus that carries a single-stranded negative-sense RNA genome that codes for five proteins. VSV is readily cultured on diverse cell types, it causes no known human disease, and it may be engineered to stimulate immune responses against pathogenic viruses. Moreover, it has potential applications as an oncolytic therapeutic, preferentially infecting and killing cancer cells. The precise replication strategy of VSV is still unknown; we aim to elucidate this mechanism through quantitative measurements and modeling. Two mechanisms have been proposed for amplification of VSV genomes during infection. In the first, linear stamping, the initial viral genome is used as a template to replicate a pool of anti-genomic templates, which are then used as templates for the generation of genomes that are packaged into viral progeny. In the second mechanism, geometric growth, progeny genomes may be fed back into the initial replication pool and used in subsequent rounds of anti-genome generation. Quantitative measurements of the number of genomes and anti-genomes early in infection are combined with model development to identify the likely mechanism of genome replication. In addition to genomic and anti-genomic RNA, absolute measurements of mRNA species are used to validate and refine a kinetic model of VSV genomic replication and growth. The levels of all RNA species during an infection are compared to predicted levels from a published model which accurately predicted VSV growth. Further, two initial infection conditions are considered: a low virus-to-cell ratio, representing the initial stages of an infection in a host organism, and a high virus-to-cell ratio to representing a later stage of spreading-infection in a host organism. This research will help advance the field of predictive biology, give insight into virus-host interactions, an open new perspectives into the development of robust anti-viral therapies.