[Partial characterization of the Pixuna virus receptor present on erythrocytes of one-day-old chicks]

A study was undertaken to evaluate the physical, chemical and immunological aspects of a receptor for Pixuna virus present on 1-day-old chicken erythrocytes. The proteases trypsin and chymotrypsin were able to expose more binding sites on the erythrocytes, increasing the hemagglutinating titer (p < 0.001). Membrane components from red blood cell membranes (ROG) were extracted with the nonionic detergent octyl glucoside. ROG could bind to Pixuna virus and prevent hemagglutination. When ROG was filtered through a 0.22 mu filter, the activity was lost, but the filtrate inhibited plaque formation in Vero cells. The membrane components did not lose activity when kept at temperatures from -5 degrees C to -134 degrees C for months. After heating at 37 degrees C for 1 h and/or at 75 degrees C for 15 min the activity remained constant. A rabbit policlonal antiserum against the membranes gave precipitin lines in ID and in CIEF that disappeared after the enzymatic treatment, but the proteases did not affect the activity to produce hemagglutination-inhibition. Similar results were obtained when a mouse antiserum against ROG was used. The present study showed that the receptor for Pixuna virus present on 1-day-old chicken erythrocytes is not proteic in nature. The membrane components, ROG, with the property of inhibiting hemagglutination, contain proteins but they were not essential for the activity. It appears that the active compound was not able to produce antibodies in these experimental conditions. ROG had two different kinds of receptors: one that was able to produce hemagglutination-inhibition and another one with the property to inhibit plaque formation in Vero cells. Apparently, lipids would be involved in the hemagglutination-inhibition activity.