Abstract
The fluorescent spot technique was developed so that the flocculation reaction between viral particles and antibodies could be seen quickly and simply on a glass slide. This technique was readily available for testing the purity of the Sendai virus during its purification. Immune serum prepared against normal sedimentable material of uninfected eggs was particularly useful to test for the presence of host components in purified viral suspensions. A highly purified fraction of high HA titer obtained by adsorption on, and elution from aluminum phosphate gel, was shown by this spot technique to be almost free from normal components. When such a purified preparation was used for HAI titration, the antibody titer was low because of the increased viral antigenic surface around the particles. The hemolytic properties known to be associated with Sendai virus were also reduced in such a purified preparation.