Brucella abortus as a potential vaccine candidate: induction of interleukin-12 secretion and enhanced B7.1 and B7.2 and intercellular adhesion molecule 1 surface expression in elutriated human monocytes stimulated by heat-inactivated B. abortus.
Development of a vaccine which is capable of generating a strong cellular immune response associated with gamma interferon (IFN-gamma) production and cytotoxic T-cell development requires that the immunogen be capable of inducing the secretion of interleukin-12 (IL-12), which is a pivotal factor for the differentiation of Th1 or Tc1 cells. We have previously shown that the heat-inactivated gram-negative bacterium Brucella abortus can induce IFN-gamma secretion by T cells. In the present study, we demonstrate that B. abortus and lipopolysaccharide (LPS) from B. abortus can induce IL-12 p40 mRNA expression and protein secretion by human elutriated monocytes (99% pure). p40 mRNA was detected within 4 h, and p40 protein could be measured at 24 h. This induction was abrogated by anti-CD14 monoclonal antibody, suggesting that monocytes recognize B. abortus via their receptor for LPS. The biological activity of IL-12 secreted by B. abortus-stimulated monocytes was demonstrated by its ability to upregulate IFN-gamma mRNA expression in T cells separated from monocytes and B. abortus by a transwell membrane. The B. abortus-induced IL-12 also enhanced NK cytolytic activity against K562 target cells. B. abortus was shown to rapidly increase the expression of the costimulatory molecules B7.1 and B7.2 and intercellular adhesion molecule 1 on human monocytes. Together, these data indicate that B. abortus can directly activate human monocytes and provide the cytokine milieu which would direct the immune response towards Th1-Tc1 differentiation.
Zaitseva
M
M
Laboratory of Retrovirus Research, Division of Viral Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, Maryland 20892, USA.
Golding
H
H
Manischewitz
J
J
Webb
D
D
Golding
B
B
D015703:Antigens, CD / Q000378:metabolism*; D018122:B7-1 Antigen / Q000378:metabolism*; D051940:B7-2 Antigen; D001428:Bacterial Vaccines / Q000276:immunology*; D001483:Base Sequence; D002003:Brucella abortus / Q000276:immunology*; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics; D018664:Interleukin-12 / Q000235:genetics / Q000378:metabolism; D015848:Interleukin-5 / Q000096:biosynthesis / Q000235:genetics; D007694:Killer Cells, Natural / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology*; D012333:RNA, Messenger / Q000032:analysis; D011940:Receptor Aggregation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D015854:Up-Regulation; D015164:Vaccines, Inactivated / Q000276:immunology*
D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D001428:Bacterial Vaccines; C497964:CD86 protein, human; D015848:Interleukin-5; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D015164:Vaccines, Inactivated; D018799:Intercellular Adhesion Molecule-1; D018664:Interleukin-12; D007371:Interferon-gamma