EXPERIMENTAL VACCINATION OF PIGS WITH AN ACTINOBACILLUS-PLEUROPNEUMONIAE SEROTYPE 5B CAPSULAR POLYSACCHARIDE TETANUS TOXOID CONJUGATE

The protective efficacy of an Actinobacillus pleuropneumoniae serotype 5b capsular polysaccharide-tetanus toroid conjugate (Ap5bCP-TT) again st homologous challenge of pigs was investigated. Four pigs were non-v accinated controls (group A), 4 pigs were injected with adjuvant witho ut antigen (group B) and 8 pigs were vaccinated with Ap5bCP-TT and adj uvant (group 0). Pigs vaccinated with Ap5bCP-TT developed antibody res ponses to the capsular polysaccharide from A. pleuropneumoniae serotyp e 5b (Ap5bCP). After challenge, all pigs in groups A and B had severe clinical signs of disease and were euthanized. In group C, 3 out of 8 pigs showed severe symptoms and were euthanized. Five pigs in group C survived throughout the study. The post challenge observation period w as 72 h. All pigs were subject to necropsy and results from gross path ological findings and microbiological examination are described. Pigs vaccinated with Ap5bCP-TT had statistically significant reduced values of the mass ratio of affected to unaffected lung tissue compared to p igs in groups A and B (p = 0.01 and p = 0.007, respectively). The resu lts showed that Ap5bCP-TT-vaccination had considerable protective effi cacy against lethality and pulmonary lesions caused by experimental in fection with A. pleuropneumoniae serotype 5b.