Antigens involved in vaccination of swine against Aujeszky's disease (pseudorabies) virus

L-particle production during primary replication of pseudorabies virus in the nasal mucosa of swine

Different tissue culture cell lines infected with a number of alphaherpesviruses produce, in addition to virions, light particles (L particles). L particles are composed of the envelope and tegument components of the virion but totally lack the proteins of the capsid and the virus genome; therefore, they are noninfectious. In this electron microscopy report, we show that L particles are produced during primary replication of the alphaherpesvirus pseudorabies virus (PRV) in the nasal mucosa of experimentally infected swine, its natural host. Although PRV infected different types of cells of the respiratory and olfactory mucosae, PRV L particles were found to be produced exclusively by epithelial cells and fibroblasts. We observed that formation of noninfectious particles occurred by budding of condensed tegument at the inner nuclear membrane and at membranes of cytoplasmic vesicles, resulting in intracisternal and intravesicular L particles, respectively. Both forms of capsidless particles were clearly distinguishable by the presence of prominent surface projections on the envelope and the higher electron density of the tegument, morphological features which were only observed in intravesicular L particles. Moreover, intravesicular but not intracisternal L particles were found to be released by exocytosis and were also identified extracellularly. Comparative analysis between PRV virion and L-particle morphogenesis indicates that both types of virus particles share a common intracellular pathway of assembly and egress but that they show different production patterns during the replication cycle of PRV.

The role of biotechnologically engineered vaccines and diagnostics in pseudorabies (Aujeszky's disease) eradication strategies

Modern-day biotechnology has an almost unlimited number of possibilities for reducing the impact of hereditary and infectious diseases. To date one of its most visible and rewarding applications for veterinary medicine has been in the genetic engineering of vaccines and diagnostics to assist in the eventual eradication of pseudorabies (PR, Aujeszky's disease). In the following review we summarize some of the most pertinent issues relative to PR eradication and point out the present and potential role of biotechnology in achieving our goal.

Efficacy of various non-oily adjuvants in immunization against the Aujeszky's disease (pseudorabies) virus

Standard oil and various non-oily adjuvants were compared for use in immunization against the Aujeszky's disease (pseudorabies) virus, both in mice and swine, and using either inactivated virions or purified glycoproteins as antigen. Mineral oil, sodium alginate, aluminium hydroxide, and saponin were assayed in mice as adjuvants for inactivated virions, saponin being the most efficient. The addition of Mab anti-CD3 did not improve either immune response or protection achieved in mice using viral particles with oil or sodium alginate. When purified glycoproteins were used as antigens, the use of ISCOM greatly enhanced specific T-cell responses and protection of mice. The incorporation of Mab anti-CD3 into ISCOM conferred 100% protection of mice. Surprisingly, when an ISCOM containing glycoproteins was assayed in swine in a single-dose trial, no improvement on the protection conferred by the oily adjuvant was observed.

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.