(158a) Quantitative Imaging of Human Rhinovirus Gene Expression Kinetics at the Single-Cell Level

The progress of a viral infection within a human host may cause mild or severe disease depending on the productivity of the earliest infected cells. The behaviors of these infected cells can be extremely heterogenous with respect to viral gene expression or virus production. It is an open question what role the state of the host cell may play in the observed behaviors. To probe this question, we infected HeLa cells, cultured in the presence or absence of serum, with a recombinant human rhinovirus (A16), engineered to express the green fluorescent protein (GFP) as a byproduct of infection. The fluorescent signals from GFP were quantified at the single-cell level as a measure of viral gene expression kinetics. Cells cultured two days in the absence of serum appeared stressed, based on smaller cell areas and loss of cell-cell contacts, and they exhibited lower susceptibility to infection based on productive GFP expression at MOI 0.01. Despite these differences, however, parameters of viral gene expression showed negligible differences between infections of serum-fed and serum-starved cells. The reduction in susceptibility to infection without apparent consequences on the kinetics of gene expression may be linked to mechanisms of autophagy, a hypothesis currently under investigation. These results provide an example of how quantitative single-cell measures may open new dimensions for probing significant biological questions such as how the virus and the host compete in their arms race.