Preparation and Titration of CsCl-Banded Adenovirus Stock

An important step m the development of modern experimental virology was the development of the plaque assay, first with bacteriophage, then with eukaryotic viruses. In order to obtain quantitative, interpretable, and reproducible results, it is necessary to know how much virus is being used in the experiment. With adenoviruses, several approaches have generally been used to quantitate virus stocks. First, virus particles are counted, e.g., in an electron microscope (1 ,2 ). Another approach is to quantitate virion DNA by optical absorbance (2 ). The problem with these approaches is that many adenovirus particles are not infectious, perhaps because they have a defective complete genome or they lack fiber or some other protein. The second approach is to determine the number of plaque-forming units (PFU) per mL. Here, the analysis quantitates the number of virions capable of a full infectious cycle. This approach will be described in detail in this article.