Potency of an experimental DNA vaccine against Aujeszky's disease in pigs

Intradermal vaccination with plasmid DNA encoding envelope glycoprotein C ( gC) of pseudorabies virus (PrV) conferred protection of pigs against Aujesz ky's disease when challenged with strain 75V19, but proved to be inadequate for protection against the highly virulent strain NIA-3. To improve the pe rformance of the DNA vaccine, animals were vaccinated intradermally with a combination of plasmids expressing PrV glycoproteins gB, gC, go, or gE unde r control of the major immediate-early promotor/enhancer of human cytomegal ovirus. 12.5 mu g per plasmid were used per immunization of 5-week old pigl ets which were injected three times at biweekly intervals. Five out of six animals survived a lethal challenge with strain NIA-3, without exhibiting c entral nervous signs, whereas all the control animals succumbed to the dise ase. This result shows the increased protection afforded by administration of the plasmid mixture over vaccination with a gC expressing plasmid alone. A comparative trial was performed using commercially available inactivated and modified-live vaccines and a mixture of plasmids expressing gB, gC, an d go, gE was omitted to conform with current eradication strategies based o n gE-deleted vaccines. All six animals vaccinated with the live vaccine sur vived the lethal NIA-3 challenge without showing severe clinical signs. In contrast, five of six animals immunized with the inactivated vaccine died, as did two non-vaccinated controls. In this test, three of six animals vacc inated with the DNA vaccine survived without severe clinical signs, whereas three succumbed to the disease. Comparing weight reduction and virus excre tion, the DNA vaccine also ranged between the inactivated and modified-live vaccines. Thus, administration of DNA constructs expressing different PrV glycoproteins was superior to an adjuvanted inactivated vaccine but less ef fective than an attenuated live vaccine in protection of pigs against PrV i nfection. Our data suggest a potential use of DNA vaccination in circumstan ces which do not allow administration of live attenuated vaccines. (C) 1999 Elsevier Science B.V. All rights reserved.