Evaluation of specific humoral immune response in pigs vaccinated intradermally with deleted Aujeszky's disease vaccine and challenged with virulent strain of Herpesvirus suis type 1.

A comparison of intradermal (ID) versus intramuscular (IM) routes of pig vaccination with deleted Aujeszky's disease (AD) vaccine on the formation of specific postvaccinal and postchallenge humoral immune response was performed. The studies were carried out on 21 eight week-old piglets, divided into three groups--two experimental and one control of 7 piglets each. Animals of first two groups were vaccinated twice in 12 and 16 week of age with deleted, live attenuated AD vaccine Porcilis Begonia (Intervet). Group I was vaccinated with a dose of 2.0 ml (10(6.0) TCID50)) intramuscularly (IM) into neck muscles, and group II received 0.2 ml (10(5.0) TCID50) intradermally (ID) in neck area using needleless apparatus SERENA model SD 1-2 (Emplast, Italy). In group K (control) 2.0 ml PBS IM was used. Seventy days after the first vaccination all pigs were intranasally infected with a dose of 10(5.5) TCID50 of virulent Northern Ireland Aujeszky-3 (NIA-3) strain of Herpesvirus suis type 1 (SHV-1) by instilling 0.5 ml of virus suspension into each nostril. Specific humoral immune response was evaluated using seroneutralization (SN) test and gE-ELISA-Pseudorabies virus gpI Antibody Test Kit (Herd Chek Anti-PRV gpI), IDEXX Lab Inc (USA). It was found that challenge caused anamnestic reaction in both groups of vaccinated pigs, but postchallenge immune response was stronger in ID-vaccinated group--on 14 day post infection (dpi) SN antibody level was considerably higher than in IM-vaccinated group. The obtained results suggest that secondary immunological response after challenge is decidedly more effective in the range of evaluated parameters in animals vaccinated by ID route, which can be linked to, perhaps underestimated yet and seldom utilized, skin immunity mechanisms in specific prophylaxis of infectious diseases. Advantages and disadvantages of SN test and ELISA are also discussed.