Borna disease viruses (BDV) isolated from more than 20 naturally infected horses, 2 sheep and a possible feline isolate were included in these studies. Most of these wild-type viruses were grown in rabbit cells. Specifically rabbit-adapted viruses establish
persistent infection in immortalized cell lines of various animal species. Brain-, tissue culture-, and cell-free released viruses could all be neutralized with
antibodies from naturally and experimentally infected animals (horse; hamster, rat, rabbit, mouse, and chicken), with highest titres in birds. Splenectomized rabbits, which were subsequently infected with BDV, efficiently produced high titres of
neutralizing antibodies. All of the neutralizing sera and cerebrospinal fluids from infected animals inhibited tissue culture spread of BDV. Experimental
infection and hyperimmunization induced
antibodies directed against the major components of the soluble
antigen (60, 40/38, 25 and 14.5 kD
proteins). Analysis of the s-
antigen complex with these sera and 6 stable
monoclonal antibodies revealed that it consists of 40/38 and 25 kD
proteins. Although each of these
antibodies detected intracellular virus-specific structures they did not recognize outer plasma membrane
antigens, showed no cross-reactivity, and had no neutralizing capacity. Unifying pathogenetic concepts of this neurotropic virus and its structural elements are discussed.