Functional and metabolic activity of neutrophils in young cattle sensitized with a non-agglutinogenic strain of Brucella

Introduction . Brucellosis remains one of the most common highly dangerous zoonotic infections. Resistance to the pathogenic microorganisms of the genus Brucella depends on the appropriate cell-mediated immunity, which includes the activation of the bactericidal mechanisms of phagocytes. Despite the repeatedly proven role of neutrophils in the fight against many bacterial pathogens, the functions of these immunocompetent cells in the setting of brucellosis have long remained unstudied. Objective . The study aimed to examine the functional and metabolic activity of neutrophils in young cattle sensitized with a non-agglutinogenic strain of Brucella . Materials and methods . The functional and metabolic state of neutrophils in young cattle immunized against brucellosis with a vaccine produced from the non-agglutinogenic RB-51 strain of Brucella abortus was assessed on days 7, 14, 21, 28, 35 after immunization using nitroblue tetrazolium (NBT) test, as well as based on the level of the enzymatic activity of myeloperoxidase and the content of non-enzymatic cationic proteins. The measurements were made photometrically in the spontaneous and stimulated variants of the test, with subsequent calculation of stimulation coefficients. Disintegrated and corpuscular antigens prepared from Brucella vaccine strains with different antigen structures were used as reaction stimulants. Results . It was found that the functional and metabolic status of neutrophils in young cattle immunized with the non-agglutinogenic strain of Brucella is characterized by increased neutrophil activity in the NBT test on days 7 and 35 of the experiment, by the absence of significant changes in the enzymatic activity of myeloperoxidase and a decrease in the content of non-enzymatic cationic proteins on days 7–14 after vaccination. Conclusion . The most pronounced increase in stimulation coefficients was observed when using disintegrated Brucella antigens as a reaction stimulant. The highest stimulation coefficients were registered on day 28 after vaccination during the assessment of the oxygen-dependent metabolism of neutrophils with the NBT test and on day 14 during the assessment of the oxygen-independent metabolism.