Neutralization of Borna disease virus depends upon terminal carbohydrate residues (alpha-D-Man, beta-D-GlcNac) of glycoproteins gp17 and gp94

Borna disease virus (BDV) is an enveloped, nonsegmented, negative-stranded RNA virus that causes infections of the brain in a wide range of animal spe cies and man. The third open reading frame codes for a protein of 17 kD (gp 17) that is N-glycosylated and contains terminal alpha-D-mannose and N-acet yl-beta-D-glucosamine residues. Rat sera raised against these carbohydrates (anti-sugar antisera) show high in vitro neutralization activity and were capable of precipitating BDV. The neutralizing capacity of sera derived fro m experimentally BDV-infected rabbits:, in turn, decreased after adsorption with those carbohydrates. They partially inhibited infection of primary yo ung rabbit brain cells in a dose-dependent manner. Furthermore, the anti-su gar antisera recognized a second virus-specific glycoprotein with an appare nt molecular mass of 94 kD (gp94), providing indirect evidence that gp94 is involved in virus adsorption and/or entry into cells. Neutralization of BD V comprises a complex event and, as shown for the first time, involves the carbohydrate residues of both glycoproteins of BDV.