Influenza virus plaque assay v1

Determine virus concentration from cell culture, lung homogenates, and more. This protocol measures virus in plaque forming units per ml solution. This protocol differs from classic flu plaque assays by using a semi-solid overlay (Avicel) as opposed to agarose. This is beneficial in avoiding reproducibility issues that can arise from burning monolayers with hot overlay, and is faster to make and aspirate. The negative is that you cannot plaque purify viral isolates as you can with agarose. Theoretically one infectious virion can spawn one plaque by initiating in a cell and infecting neighboring cells. This is the gold standard for virology, and for influenza, the plaque:particle ration is ~ 1:100. Thus there are lots of non/semi-infectious or defective interfering particles that are produced that are not on their own infectious.