A novel immunostimulating factor (ISTF) of Actinobacillus actinomycetemcomitans ATCC 29522 was isolated and characterized as inducing proliferation of mouse B cells and human peripheral blood mononuclear cells. This factor was isolated from the bacterial culture medium and purified by size exclusion chromatography, dye-ligand affinity chromatography, immunoaffinity chromatography using monoclonal antibodies, and preparative electrophoresis. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the purified ISTF migrated as a single band corresponding to a molecular mass of 13 kDa. ISTF was a proteinaceous material distinct from lipopolysaccharide; it directly induced the proliferation of B lymphocytes but had no effect on the proliferation of T lymphocytes, even in the presence of antigen-presenting cells. A B-lymphocyte-mitogenic activity of ISTF was also shown by flow cytometric analysis of responding cell subpopulations. Immunoblot analysis revealed that ISTF was a component of the outer membranes of bacteria, could exist as a soluble form, and was released by growing and/or lysed bacteria. These results suggest that ISTF produced by A. actinomycetemcomitans may play an important role in immunopathologic changes associated with A. actinomycetemcomitans infections.Actinobacillus actinomycetemcomitans, a nonmotile, gramnegative coccobacillus, is associated with several human diseases including endocarditis, meningitis, osteomyelitis, subcutaneous abscesses, and periodontal diseases (2,8,20,24,30). Although the pathogenic mechanism of A. actinomycetemcomitans is not known, it has been proposed that the impairment of the host immune mechanism by the bacteria-producing virulence factors might contribute to the disease process. Many other studies have described several virulence factors of A. actinomycetemcomitans, which exhibited alterations in immune regulation. Immunosuppressive factor (ISF; 60 kDa) inhibited mitogen-induced T-cell proliferation and immunoglobulin (Ig) production (26,27). Suppressive factor 1 (SF1; 14 kDa) downregulated T-cell proliferation and cytokine production (13). Leukotoxin (115 kDa) inhibited the responsiveness of human peripheral blood mononuclear cells (PBMC) to mitogens and antigens by subverting monocytes (23). Lipopolysaccharide (LPS) suppressed antigen-and mitogen-induced human T-cell proliferation by inducing the release of prostaglandin E2 from activated macrophages (5). As all these factors contributed to the suppression of lymphocyte activation, it has been suggested that products of A. actinomycetemcomitans might possess a lymphocyte-activating substance like a superantigen (1,16,17,32). During studies in our laboratory focusing on an understanding of the immunomodulatory activity of the products from A. actinomycetemcomitans, we became intrigued by an indication that immunosuppressing and immunostimulating activities were present simultaneously in the bacterial preparations. A consistent pattern was observed: A. actinomycetemcomitans homogenates ...

Abstract:Immunostimulating factor (ISTF) isolated from Actinobacillus actinomycetemcomitans which has been described previously, is distinct from lipopolysaccharide and induces proliferation of B cells. This study was undertaken to investigate whether ISTF might enhance the stimulation of other immune cells. Immunohistochemically, ISTF exhibited a profound stimulating effect on macrophages and dendritic cells as well as B cells in the spleen of BALB/c mice. ISTF was also recognized for its capacity to induce direct activation of mouse macrophages to produce IL-6, TNF-␣, and NO and MHC class II expression. Therefore, it is postulated that ISTF stimulates macrophages and possibly other cells to produce a wide variety of proinflammatory mediators, which may be involved in the chronicity and tissue destruction of periodontal disease.

The objective of this research was to provide the characterization and method for producing anti-E. coli O157:H7 antibodies in egg-laying hens and to determine if the antibody can restrain the proliferation of E. coli O157:H7 in-vitro. Selected antigenic fractions (whole cell, outer membrane protein and lipopolysaccharide (LPS)) from E. coli O157:H7 were injected to hens in order to produce anti-E. coli O157:H7 antibodies. The immune response and the egg yolk antibodies of laying hens against the whole cell, outer membrane protein and LPS antigens were monitored by ELISA. The level of antibodies against whole cell antigen monitored through ELISA sharply increased after the initial immunization, and it was found to be maximum on day 49 however, the level was maintained up to day 70. Antibodies (5 mg/ml) directed against the whole cell inhibited E. coli proliferation 10-13 times more than outer membrane protein or LPS. The antibody response against the whole cell antigens appeared to have higher activity in restraining the proliferation of E. coli O157:H7 than antibody against outer membrane protein or LPS. Results reflected that increasing the IgY's in the egg yolk could prevent greater economic losses due to human and animal health from pathogenic bacteria i.e. E. coli O157:H7.

No abstract