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Objectives: Existing Brucella vaccines are attenuated and can cause vaccine-associated brucellosis; and these safety concerns have affected their application. Although subunit vaccines have the advantages of safety, efficacy, low cost, and rapid production, they are usually poorly immunogenic and insufficient to trigger persistent immunity. Therefore, we added layered double hydroxide (LDH) as an adjuvant to Brucella subunit vaccine formulations to enhance the immune response to the antigen., Materials and Methods: LDH and Freund's adjuvant were combined with Brucella outer-membrane vesicles (OMVs) and OMV-associated proteins to form a subunit vaccine, respectively. The immunogenicity of LDH as an adjuvant was assessed in BALB/c mice. We examined levels of immunoglobulin G, G1, and G2a (IgG, IgG1, and IgG2a) antibodies (aBs); percentages of Cluster of Differentiation 4-positive (CD4 + ) and CD8 + T cells in peripheral-blood lymphocytes; and secretion of cytokines in mouse spleen lymphocytes. Finally, splenic index and splenic bacterial load were assessed via Brucella challenge experiments on mice., Results: The LDH subunit vaccine also produced high levels of specific aBs in mice compared with Freund's adjuvant subunit vaccine and induced mainly T-helper 1 cell (T h 1)-type immune responses. In addition, mice in the LDH subunit vaccine group had significantly lower bacterial loads in their spleens than those in the Freund's adjuvant subunit vaccine group, and the LDH-OMV vaccine offered a higher level of protection against Brucella attack., Conclusion: LDH as an adjuvant-paired vaccine provided a high level of protection against Brucella infection., Competing Interests: The authors have no conflicts of interest to declare.

Background: Brucella infection induces brucellosis, a zoonotic disease. The intracellular circulation process and virulence of Brucella mainly depend on its type IV secretion system (T4SS) expressing secretory effectors. Secreted protein BspJ is a nucleomodulin of Brucella that invades the host cell nucleus. BspJ mediates host energy synthesis and apoptosis through interaction with proteins. However, the mechanism of BspJ as it affects the intracellular survival of Brucella remains to be clarified., Objectives: To verify the functions of nucleomodulin BspJ in Brucella 's intracellular infection cycles., Methods: Constructed Brucella abortus BspJ gene deletion strain ( B. abortus ΔBspJ) and complement strain ( B. abortus pBspJ) and studied their roles in the proliferation of Brucella both in vivo and in vitro ., Results: BspJ gene deletion reduced the survival and intracellular proliferation of Brucella at the replicating Brucella -containing vacuoles (rBCV) stage. Compared with the parent strain, the colonization ability of the bacteria in mice was significantly reduced, causing less inflammatory infiltration and pathological damage. We also found that the knockout of BspJ altered the secretion of cytokines (interleukin [IL]-6, IL-1β, IL-10, tumor necrosis factor-α, interferon-γ) in host cells and in mice to affect the intracellular survival of Brucella ., Conclusions: BspJ is extremely important for the circulatory proliferation of Brucella in the host, and it may be involved in a previously unknown mechanism of Brucella 's intracellular survival., Competing Interests: The authors declare no conflicts of interest., (© 2022 The Korean Society of Veterinary Science.)