Methodology — A Critique

The most useful way to assess antiviral activity is to examine the effect of the compound on infectious virus in cell cultures, accompanied by an appropriate parameter for infectivity, usually plaque forming units (pfu) or TCD₅₀. Several viruses should be used in the screening program in order to offer all possible targets to the compound, i.e., proteins, glycoproteins, lipids, and single- and double-stranded DNA and RNA. Measurements of virus infectivity, such as TCD₅₀ or statistically adequate end-point determinations that also measure infectious virions, are also acceptable. The majority of the virus particles may be noninfectious for a variety of reasons, even though they maintain their integrity. Since most animal viruses are selective in terms of susceptible cell type, then very often different viruses have to be assayed in different cell cultures. The use of cell cultures is the easiest, quickest, and most economical way to assess the potential of an antiviral compound or extract.