Serodiagnostic potential of Brucella outer membrane and periplasmic proteins

Abstract

The aim of this study was to evaluate the serological diagnostic potential of the Brucella recombinant outer membrane(rOMP25, rOMP31) and periplasmic proteins (rBP26, rSOD) in a comparative way using an indirect enzyme-linked immunosorbentassay (i-ELISA). Rabbit and/or mouse antibodies to Brucella whole cell and/or soluble protein preparations recognized all recombinantproteins used, which confirms the expression of target antigens in E. coli in active form. The recombinant proteins showed differentantigenicity to antibodies of cattle kept on a brucellosis-affected (endemic) farm and/or a new focus of infection. Thus, the presence ofanti-Brucella antibodies was confirmed by i-ELISA/rSOD in 79% of cows from endemic conditions with positive results by conventionalserological tests (RBPT and/or CFT). However, antibodies specific to this protein were detected in only 14% of seropositive animals keptin the hotbed of a new brucellosis infection. Moreover, rSOD-specific antibodies were not detected in the sera of vaccinated cattle froma brucellosis-free farm, whereas antibodies to other recombinant proteins were found in 2%–8% of animals. Using recombinant proteinsin immunoassays significantly reduced the number of cows positive for brucellosis. Furthermore, there was not a single protein amongthe rOMPs that would show the total positive results of all proteins used. Thus, the development of reliable ELISA tests for the diagnosisof brucellosis requires further comprehensive study of the recombinant proteins in order to design a multiprotein antigen that consistsof a combination of several proteins with diagnostic potential.