51] Virus yield-reduction assay for interferon by titration of Sindbis virus hemagglutinin

Abstract

The basic steps in a hemagglutination (HA) reduction assay for interferon are (1) incubation of interferon (IF) dilutions on cultures, (2) challenge of the cultures with a high input multiplicity (MOI) of hemagglutinating virus, and (3) measurement of the reduction of hemagglutinin yield. The chapter presents the rationale for performing such an assay and a detailed description of the procedures. Some of the advantages of the HA reduction assay over the infectious virus yield-reduction assay are that HA titrations are simpler, more rapid, and less expensive than infectious virus titrations and hemagglutinin is usually more stable than infectivity, hence the time of collection of the samples after maximum virus production for HA titration is not as critical as it is for infectivity titrations. The major disadvantages usually encountered are (1) the preparation of reagents needed to obtain the proper pH for optimal HA activity, (2) inhibitors of HA activity that may be present in serum or culture fluids, and (3) the availability of male goose erythrocytes.