A Quantitative Spectrophotometric Study of Virus Infected KB Cells

The effect of adenovirus and vaccinia infection on KB cells was studied spectrophotometrically by comparing the DNA, RNA, and protein concentrations of infected cells with normal cells. The concentration of these macromolecules in normal cells was established by assaying a large number of KB cultures at different stages of growth. Data were plotted against cell count and time. DNA, RNA, and protein concentrations were found to be linear functions of cell count within a range of 5-25 x 10^5 cells/ml. Replicate cultures of KB cells were inoculated with vaccinia or adenovirus at 10 PFU/cell and harvested at 24 hr intervals for 4 days. The cells were counted microscopically at each interval and the concentrations of DNA, RNA, and protein were determined. These results were compared to concentrations and cell counts in uninfected cells and plotted against time. Cell division was inhibited by infection with either of the viruses. At 24 hr post infection (PI) the RNA concentration in infected cells was greater than that found in normal cells. A sharp decrease in RNA content occurred after 24 hr PI until the levels in infected cells were below those in uninfected cells. DNA and protein concentrations were much lower in the infected cells than in the normal cultures. DNA and protein levels increased in the infected cells at 72 hr PI while the DNA concentration in the uninfected cells remained constant. In vaccinia-infected cells the rise in protein synthesis occurred simultaneously with a rise in hemagglutination titer. A similar increase in protein concentration paralleled a rise in complement fixation titer in adenovirus-infected cells.