Porcine reproductive and respiratory syndrome virus hemagglutinin (HAin) was readily adsorbed on mouse erythrocytes at 4, 22, or 37°C, but not on goose erythrocytes. The adsorbed HAin could not be eluted from the cells by resuspending in phosphate buffered saline, by incubating at 37 or 50°C, or by incubating in the presence of neuraminidase. The hemagglutinating activity was not dependent on the pH and NaCl molarity tested. The receptor of mouse erythrocytes for the HAin was relatively stable to trypsin, neuraminidase, sodium deoxycholate (DOC), potassium periodate (KIO4
), dithiothreitol (DTT), 2-mercaptoethanol (2-ME) and formalin treatments. The HAin was inactivated by 2-ME and was gradually inactivated by pepsin, formalin and DTT, but not by β-glucosidase, trypsin, α-amylase, papain, phospholipase C, neuraminidase, KIO4
, and ethylendiamine tetraacetic acid (EDTA) treatments. The HAin was stable at 37°C or lower temperatures, but not at 56°C or higher. The HAin was relatively resistant to ultraviolet irradiation and sonication. In the equilibrium centrifugation of the HAin preparation on a CsCl density gradient, the HAin activity showed a sharp peak at 1.17 g/cm3
. In the SDS-PAGE analysis, the structural polypeptide of HAin in the peak fraction seems to be the nucleocapsid (N) polypeptide with molecular weight of 15 kDa.