Hemagglutination by equine infectious anemia virus.

Equine infectious anemia (EIA) virus which was propagated on an equine dermal cell line agglutinated guinea pig erythrocytes. Viral fluids containing about 10(7.5) mean tissue culture infective doses/ml showed hemagglutinating (HA) titers ranging from 16 to 32 units/0.05 ml. Results of cesium chloride equilibrium density gradient centrifugation revealed that the hemagglutinin was inseparable from the virus particles. The hemagglutination reaction persisted over a wide range of temperature and pH, and the absence of divalent cations did not decrease its activity. The HA activity was stable at 4 degrees C but not at 56 degreesC. The activity was destroyed by virus-disrupting lipid solvents and moderately sensitive to a proteolytic enzyme. Neuraminidase enhanced HA activity slightly. Phospholipase C had no effect on HA titer, although it completely inactivated infectivity. It was relatively stable to ultraviolet irradiation. Thus, the hemagglutinin appears to be closely associated with virus particles, and its activity is dependent on the presence of its lipids and proteins. Hemagglutination was inhibited by sera from horses infected with EIA virus. Hemagglutinin receptors on the erythrocytes were inactivated by a proteolytic enzyme and formaldehyde but were not influenced by neuraminidase, sodium deoxycholate, or KIO4.