Protective effects of partially purified antigens of Actinobacillus pleuropneumoniae on experimentally infected mice.

ABSTRACT

Three different models of protection experiments in mice using partially purified Actinobacillus pleuropneumoniae antigens such as crude culture supernatant extract (CCSE) and partially purified cell extract (PPCE) were attempted. Biochemical analysis showed that these two immunogens had protein concentration of 0.17-0.2 mg/mL and pentose concentration of 0.012-0.014 mg/mL. In the first model intranasal (IN) vaccination with different doses (from 0.01-10 IN-LD50) against IN challenge with the dose of 20 IN-LD50 containing 1.2 x 10(9) colony forming unit (CFU)/50 microL showed that only those with the dose more than 1 IN-LD50 had slight protection in terms of survival index (SI). In the second model of protection experiment, in which subcutaneous vaccination (s.c.) with the immunogens plus soybean oil against IN challenge with 10 IN-LD50 containing 6 x 10(8) CFU/50 microL, showed that formalin-killed bacteria (bacterin) and CCSE plus PPCE had only a slight protection whereas vaccination with CCSE or PPCE immunogen alone had no protection. In the third model of protection experiment, in which the intramuscular (i.m.) vaccination with the immunogens plus aluminum hydroxide [Al(OH3)] gel against intraperitoneal (i.p.) challenge with the dose of either 2 or 6 i.p.-LD50 containing 1.2-3.6 x 10(8) CFU/0.5 mL of 0.3% mucin saline showed highly effective.