Occurrence and reactivation of latent Aujeszky's disease virus following challenge in previously vaccinated pigs.

Pigs which were vaccinated with an inactivated ADV vaccine developed a latent ADV infection up to 18 months after ADV challenge. Up to 6.5 months p.i. latent virus could be demonstrated by co-cultivation of different organ tissues (lungs, tonsils, olfactory bulb, brain stem, medulla). Afterwards, reactivation of latent virus was only achieved by immunosuppression of the animals. Immunosuppression led to a limited virus replication in nasal mucosa, tonsils, lymph nodes and central nervous system. In addition ADV was detected in the nasal secretions., Humoral and cellular immunity was investigated before and after immunosuppression of the animals. Before immunosuppression most of the animals displayed SCC, ADV-ADCC and ADV-LYST, and all animals had medium to high titres of neutralizing serum antibodies. After immunosuppression the number of pigs reacting in SCC and ADV-LYST, assays was distinctly reduced, but the number of animals reacting in ADV-ADCC assays remained unaltered. A significant reduction of serum antibody titres occurred only in 2 of 12 animals one day after the end of immunosuppression.