Hyperimmune sera against four strains of Corynebacterium pseudotuberculosis isolated from different animals (sheep, goat, buffalo and cattle) were obtained by inoculating rabbits with strains in different forms (live, dead plus live or dead). Immunization with live or dead bac teria followed by live strains gave similar results with regard to antibody titres and number of precipitin lines. Typing 21 strains of C. pseudotuberculosis by specific precipitin reac tions in agar gel was performed by using antigens extracted with sodium deoxycholate. The authors concluded that they were divisible into two serotypes, I and II. The nitrate reduction test and animal pathogenicity tests (by inocu lating guinea-pigs subcutaneously) demonstrated additional differences between the two types. Type I was nitrate negative, and produced local and general absces ses in guinea-pigs, with a prolonged course (15 days) ending fatally. It included all the strains originating from sheep and goats, but only 3 of 5 cattle strains. Type II comprised all 7 isolates from buffaloes and 2 of the cattle strains. All strains were nitrate positive and did not produce abscesses in guinea-pigs, but they caused tissue necrosis at the site of inoculation, with a rapid course (not more than five days) ending in death.
Corynebacterium ovis has a clear immunopotentiating effect when used as an adjuvant with several antigens including egg albumin, Salmonella typhimurium and foot and mouth disease virus, inoculated into guinea pigs. The optimal dose was found to be 400 mg of C. ovis mixed with antigen. However, a dose of 300 mg of C. ovis when mixed with incomplete Freund's adjuvant was enough to stimulate a sustained potent immune response which was superior to that obtained with the complete Freund's adjuvant. Immunopotentiation is a topic in immunology that is attracting increasing interest. In this field, oil adjuvants have proved their superiority and Freund et al. (10) have shown that the addition of some bacteria, such as mycobacte ria, to such oil adjuvants improves their immunopotentiating effect. Current studies carried out in our laboratory on crystal violet treated C. ovis have clearly shown its capacity as a non-specific immune stimulant, capable of raising the resistance of sheep to artificial infection with potential pathogens, in a manner comparable with that produced by BCG (5, 6). It was decided to test the formalin-killed C. ovis for its immunopotentiat ing ability when used as an adjuvant with inert antigens and killed microbial vaccines. MATERIALS AND METHODS Animals. Guinea pigs : 630 healthy albino adult guinea pigs, weighing approxim ately 400-500 grams, were used in this study. The animals were put in equal * Under-Secretary of State for Veterinary Affairs, Egypt.
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