Abstract
The indirect hemagglutination technique has been improved by fixing the carrier erythrocytes successively with glutaraldehyde and sulfosalicylic acid. Sensitization by covalent conjugation of influenza virus antigens to the erythrocytes with various coupling reagents, which resulted in stable and highly sensitive test cells, has been defined. An economical affinity chromatography procedure using antibody-coated agarose has been developed to prepare sufficiently pure antigens from fowl plague virus-infected choriollantoic membranes.