PROTECTION OF MICE AND SWINE AGAINST INFECTION WITH ACTINOBACILLUS-PLEUROPNEUMONIAE BY VACCINATION

CaCl2 and LiCl cell extracts and a crude hemolysin preparation were is olated from Actinobacillus pleuropneumoniae serotype 1 strain 4074 and tested for protection against A. pleuropneumoniae serotype 1 and 5 in mice. The LiCl cell extract adsorbed on AlPO4 and the crude hemolysin preparation adsorbed on Al(OH)(3) showed a highly significant protect ion (P< 0.01) against both serotypes. Different vaccine preparations w ere used to immunize pigs by intra-muscular injection at days 0 and 14 ; the pigs were then challenged at day 21 by intra-tracheal inoculatio n of 1x10(8) colony forming units (CFU) of a serotype 1 strain 4074. A vaccine which combined the LiCl extract and the crude hemolysin prepa ration adsorbed on Al(OH)(3) gave the best protection with no mortalit y and no sign of morbidity in the vaccinated pigs. In the other experi mental groups which included a group immunized with a commercial bacte rin, mortality, respiratory disease and extensive pulmonary lesions we re noted. This mixture shows good potential as a vaccine against pleur opneumonia in pigs.