Th2-related immune responses by the Brucella abortus cellular antigens, malate dehydrogenase, elongation factor, and arginase

Abstract

Brucellosis is an important zoonotic disease caused by Brucella species. The disease is difficult to control due to the intracellular survival of the bacterium and the lack of precise understanding of pathogenesis. Despite of continuous researches on the pathogenesis of Brucella spp. infection, there is still question on the pathogenesis, especially earlier immune response in the bacterial infection. Malate dehydrogenase (MDH), elongation factor (Tsf), and arginase (RocF), which showed serological reactivity, were purified after gene cloning, and their immune modulating activities were then analyzed in a murine model. Cytokine production profiles were investigated by stimulating RAW 264.7 cells and navie splenocytes with the three recombinant proteins. Also, immune responses were analyzed by ELISA and an ELispot assay after immunizing mice with the three proteins. Only TNF-alpha was produced in stimulated RAW 264.7 cells, whereas Th1-related cytokines, IFN-gamma and IL-2, were induced in navie splenocytes. In contrast, Th2-type immune response was more strongly induced in antigen-secreting cells in the splenocytes obtained 28 days after immunizing mice with the three proteins, as were IgM and IgG. The induction of Th2-related antibody, IgG1, was higher than the Th1-related antibody, IgG2a, in immunized mice. These results suggest that the three proteins strongly induce Th2-type immune response in vivo, even though Th1-related cytokines were produced in vitro. (C) 2017 Elsevier Ltd. All rights reserved.