Aim: The aim of the study was to obtain a vaccine against animal brucellosis having high immunogenic properties by carrying an evaluation of the effectiveness of split-conjugated animal brucellosis vaccine combined with fosprenil and polypeptide C as a molecular immunomodulatory adjuvant according to the results of serological studies of the blood of animals: Agglutination reaction, complement fixation, and rose Bengal sample.

Materials and Methods: Eighteen calves of Holstein Friesians breed, aged 5 months, with a living weight of 100-150 kg, were divided into three groups of six animals each. All animals were healthy and they received a prophylactic vaccination against brucellosis. The dry split-conjugated vaccine against brucellosis in animals was dissolved in saline and for this purpose, 10 ml of saline was poured into the vaccine vial. Then the content was mixed, and afterward 1 ml was used per animal. Fosprenil was used at the rate of 1 kg of animal weight: 100 kg (calf weight) was multiplied by 0.05 (dose/1 kg of animal weight); 5 ml of fosprenil was obtained, which was collected into disposable syringes and intramuscularly sterilely injected into the croup area.

Calves in the first group (control) were intramuscularly injected with the vaccine at a dose of 1.0 ml, and fosprenil at a dose of 5.0 ml was administered intramuscularly once to the croup area. Animals from the second group were subcutaneously immunized by the vaccine with polypeptide C at a dose of 1.0 ml. Polypeptide C is a solution that was poured into a vial with a vaccine at a dose of 10.0 ml, the content was mixed, and then calves were injected subcutaneously into the middle third of the neck in 1 ml (10 doses in a vial).

Immunization of calves in the third group was carried out with a vaccine, diluted with an isotonic sodium chloride solution of 0.9%, at a dose of 1.0 ml subcutaneously once. At the 14th, 30th, and 90th days after vaccination, a blood sampling was taken for serological tests: Agglutination test, complement fixation test, and rose Bengal test.

Results: After conducting serological studies, it was noted that split-conjugated vaccine against animal brucellosis using fosprenil forms antibodies in large titers and they persist for a longer time in the body of animals compared to the other tested vaccine: The first combination with the immunomodulatory polypeptide C and the vaccine only on the physiological solution.

Conclusion: The developed complex of split-conjugated vaccine against brucellosis in animals enhances the humoral immune response of the organism against brucellosis and improves the protection of animals against the disease when it is used with the immunomodulatory fosprenil. In the future, we want to expand the use of the resulting complex in the fight against brucellosis on a larger population and to study the change in cellular immunity after the introduction of the resulting complex on an animal organism.

Keywords: brucellosis, fosprenil, polypeptide C, split-conjugated vaccine against animal brucellosis.