Study of the immunopotentiator effects of dialyzable leukocyte extracts obtained out of leukocytes previously used for interferon production

Dialyzable leukocyte extract used in the prevention of Salmonella infection in calves

The protective effect of dialyzable leukocyte extract (DLE) was investigated in the experimental model of Salmonella infection in calves. DLE was obtained from the lymphatic nodes and spleens of fattening bulls immunized with whole-cell Salmonella vaccine (designated DLEs-im), from the same organs of calves immunized and subsequently infected with Salmonella typhimurium (DLEs-inf), and from non-immunized fattening bulls (DLEn). Three doses of DLEs-inf and DLEs-im applied intravenously at 3-day intervals induced protection in all calves against infection. There were statistically significant differences in the immunological, clinical and microbiological parameters. Three doses of DLEs-inf injected intramuscularly at 3-day intervals provided a protective effect; however, one calf died. The intravenous application of DLEn induced low protection against experimental Salmonella infection and two calves died. The results indicate that the preparation of antigen-specific DLE may be possible via immunization of fattening bulls.