Brucella secreted effector BspH stimulates intracellular ion flux and confers anti-Brucella immunity.

The facultative intracellular pathogen Brucella spp. relies on the translocation of secreted effector proteins, such as BspH, to establish and maintain its persistent niche within mammalian and human host cell. Following the cloning, expression, and purification of secreted protein BspH, we assessed its immunocompetence. The recombinant protein (rBspH) was used to stimulate murine RAW 264.7 macrophages, and the production of cytokines along with hydrogen (H+), calcium (Ca2+), and hydrogen peroxide (H2O2) ions was measured. Additionally, the immune responses in mice immunized with rBspH were evaluated by ELISA. The results indicated that stimulation of macrophages with rBspH specifically induced the production of H+ and Ca2+ ions, but not H2O2. Furthermore, it triggered the secretion of both Th1 and Th2-associated cytokines. In immunized mice, rBspH elicited a robust humoral response, characterized by the production of specific IgG and elevated levels of Th1 and Th2 cytokines. Crucially, this immune activation conferred significant protection against a subsequent challenge with B. abortus A19. Collectively, these results establish rBspH as a promising candidate for the development of a subunit vaccine against brucellosis.