50] Virus yield-reduction assay for interferon by titration of infectious virus

Abstract

Publisher Summary This chapter presents the temporal changes in antiviral activity that occur within a cell following interferon (IF) treatment and the ultimate effect of these changes on the virus growth cycle, the yield-reduction assays are the method of choice. The critical advantage is that yield-reduction assays are based on the inhibition of virus replication during a single growth cycle, which is achieved either by the use of a high-input multiplicity of challenge virus or by harvesting the progeny virus after one growth cycle. This assay consists of three sequential parts: (1) the incubation of IF dilutions with sensitive cell cultures, (2) the challenge of IF-treated cells with a high multiplicity of virus, and (3) measurement of the degree of inhibition of viral yield. This chapter presents the rationale for the relative advantages of this assay and procedures for performing the assay. Some of the advantages of the yield-reduction assay are that (1) the effect of endogenous IF induced in the system is minimal because the input multiplicity (MOI) of the challenge virus is high enough to infect approximately 100% of the cells [5-10 plaque-forming units (PFU) per cell], (2) the effects of the decay of antiviral activity during the time the challenge virus is replicating in the cells is minimal, and (3) high accuracy can be achieved by titrating progeny virus in a cell type that allows plaquing of the virus.