This study aimed to investigate the effectiveness of carrageenan (CGN) as an oral immune adjuvant. During the initial research, the inadvertent shallow insertion of an oral gavage needle confirmed CGN’s effect as an adjuvant for esophageal immunization. However, in oral immunization, antibody formation was not observed regardless of CGN’s presence or absence as an adjuvant. Conversely, when bovine serum albumin (used as an antigen) was introduced into the esophagus along with CGN, it resulted in the production of antigen-specific IgG. An exploration was conducted to ascertain whether CGN’s adjuvant effects were associated with prolonging the antigen’s residence time in the esophagus. Upon introducing the antigen into the esophagus without CGN, it was undetectable at two minutes post-introduction. Conversely, when administered with CGN, the antigen remained detectable in the esophagus for up to five minutes post-introduction. To investigate whether this immune response was elicited through mucosal immune mechanisms in the esophagus, the production of IgA, a representative immunoglobulin of mucosal immunity, was assessed. Following esophageal immunization with CGN as an adjuvant, total IgG, IgG1, and IgG2a were detected in serum, while IgA was not detected. These findings suggest that under specific conditions, the esophagus may serve as a site for initiating a novel immune response.

This study investigated the efficacy of four Brucella (B.) abortus recombinant proteins, namely adenylate kinase (Adk), nucleoside diphosphate kinase (Ndk), 50S ribosomal protein (L7/L12) and preprotein translocase subunit (SecB), as a combined subunit vaccine (CSV) against B. abortus infection in BALB/c mice. Immunoblotting assay showed that these four recombinant proteins as well as pcold-TF vector reacted individually with Brucella-positive serum, but not with Brucella-negative serum. The peripheral blood CD4+ T cell population was increased in CSV-immunized mice compared to PBS and pcold-TF vector groups. In addition, CSV and pcold-TF groups displayed induced IgG1 and IgG2a antibodies production compared to PBS and RB51 group, whereas IgG2a titer was higher than IgG1 titer in CSV group. The secretion profiles of IgG1 and IgG2a production together with an enhancement of CD4+ T cell population suggested that CSV did not only induce T helper 1 (Th1) T cell immunity but also humoral immunity. Therein, Th1 T cell immunity is more predominant in eliminating intracellular bacteria B. abortus. Furthermore, CSV immunization significantly reduced the bacterial burden in the spleen as well as the spleen weight in comparison to PBS and pcold-TF groups. Altogether, combination of these antigens could be potential to induce protective immunity against B. abortus infection in animals.

This study evaluated the protective effects of a combination of eight B. abortus recombinant proteins that were cloned and expressed into a pMal vector system and DH5α: nucleoside diphosphate kinase (rNdk), 50S ribosomal protein (rL7/L12), malate dehydrogenase (rMDH), DNA starvation/stationary phase protection protein (rDps), elongation factor (rTsf), arginase (rRocF), superoxide dismutase (rSodC), and riboflavin synthase subunit beta (rRibH). The proteins were induced, purified, and administered intraperitoneally into BALB/c mice. The mice were immunized three times at weeks 0, 2, and 5 and then infected intraperitoneally (IP) with 5×104 CFU of virulent B. abortus 544 one week after the last immunization. The spleens were collected and the bacterial burden was evaluated at four weeks post-infection. The results showed that this combination produced a significant reduction of the bacterial burden in the spleen with a log reduction of 1.01 compared to the PBS group. Cytokine analysis revealed induction of the cell-mediated immune response in that TNF (tumor necrosis factor) and proinflammatory cytokines IL-6 (Interleukin 6) and MCP-1 (macrophage chemoattractant protein-1) were elevated significantly. In summary, vaccination with a combination of eight different proteins induced a significant protective effect indicative of a cell mediated immune response.