Comparison of the protective efficacy of Aujeszky's disease (pseudorabies) virus glycoproteins obtained from different sources.

The immunogenic properties of a series of glycoprotein preparations are compared using inactivated conventional vaccines as reference. Serological response and protective efficacy of vaccination of mice and pigs are evaluated for glycoprotein immunogens obtained from various sources. BHK-21 cell cultures were infected with Aujeszky's disease virus and used as antigenic source. Glycoproteins were obtained from (i) the whole culture (ii) the cell sediment and (iii) the clarified supernatant. Both in pigs and in mice, protection was greater with glycoproteins purified from infected-cell membranes than with viral mature particle glycoproteins. The specific profiles of humoral responses were basically identical regardless of the source of glycoprotein. Bartha strain, one of the gI- strains most commonly used as an attenuated vaccine, was also used as a glycoprotein source. Immunogens obtained from this strain were protective in challenge trials with the virulent E-974 strain of the Aujeszky's disease virus. Glycoproteins did not induce detectable delayed type hypersensitivity in mice but conferred greater protection than particulate antigens (which, conversely, did induce a detectable delayed type hypersensitivity reaction). Until the recent proposal of the potency criterion delta 7, no objective method was available to evaluate the degree of protection conferred by Aujeszky's disease vaccines. In this study, we thus used the protection index, a quantitative parameter designed to evaluate potency of vaccines against Aujeszky's disease virus.