Antigenic Activity of Various Rhodococcus equi Strain Plasmids

Background and Aim. Rhodococcus equi (R. equi) infection is a fatal cause of equine rhodococcosis. Infections have also been reported in other species and humans. This study evaluated the immune response of R. equi in rabbits.Materials and Methods. Different strains of R. equi (with and without plasmids) were administered to rabbits. Blood samples were collected from the ear veins of the rabbits at 7, 14, 21, and 28 days after the initial administration of the antigen, and the serum was examined for specific antibodies against R. equi plasmid antigens using the complement fixation reaction.Results. The minimum antibody level was recorded on day 7. The average antibody level throughout the study period was slightly above the median, indicating a small asymmetry toward higher values. By day 28, the antibody level had reached 75% of values ≤4.25.Conclusion. All strains of R. equi exhibited antigenic properties to varying degrees. The antibody level upon plasmid pVapN administration was higher than that of the other cases.