Antiviral Assay by CPE:  

This test is for initial screening of potentially antiviral compounds.  The antiviral activity of the compound is evaluated based on the ability of the compound to prevent virus from causing viral cytopathic effects (CPE) in mammalian cell culture.  Eight dilutions of test compound are assayed, and the effective antiviral concentration determined by regression analysis.  The toxicity of the test compound is determined in parallel. An abbreviated test with only 4 dilutions of compound may be employed to screen large numbers of compounds quickly and at a reduced cost.

Virus Yield Reduction Assay:

This test evaluates the ability of the compound to inhibit virus production in mammalian cell culture. This is a two-step assay where virus is first produced in cultures containing the antiviral substance at varying dilutions, followed later by titration of the samples for virus titer by endpoint dilution in 96-well microplates. Eight dilutions of test compound are assayed, and the effective antiviral concentration determined by regression analysis. This test is normally requested as a follow-up for compounds that demonstrate activity in the CPE assay.

Virucidal Assay:

This assay shows whether a test compound inactivates ("kills") virus outside of cells, or in other words, whether the compound inactivates the virus before infection of the cells. A virucidal compound will appear active in the antiviral assay, but virucidal compounds (e.g. alcohol, sodium hypochlorite, etc.) are normally not considered candidates for antiviral treatment.  The assay is performed by incubating virus plus compound for 1 hour (or a length of time requested by the sponsor), followed by determining virus titer by endpoint dilution in 96-well microplates of cells.