title: Mechanisms of monophosphoryl lipid A augmentation of host responses to recombinant HagB from Porphyromonas gingivalis.
abstract: Porphyromonas gingivalis, a gram-negative, black-pigmented anaerobe, is among the microorganisms implicated in the etiology of adult periodontal disease. This bacterium possesses a number of factors, including hemagglutinins, of potential importance in virulence. Our laboratory has shown the induction of protection to P. gingivalis infection after subcutaneous immunization with recombinant hemagglutinin B (rHagB). The purpose of this study was to determine if humoral antibody responses are induced after intranasal (i.n.) immunization of rHagB and if monophosphoryl lipid A (MPL), a nontoxic derivative of the lipid A region of lipopolysaccharide, acts as a mucosal adjuvant and potentiates responses to rHagB. Further, the effects of MPL on the nature of the response to HagB and on the costimulatory molecules B7-1 and B7-2 on different antigen-presenting cells (APC) were evaluated. Groups of BALB/c mice were immunized three times (2-week intervals) by the i.n. route with HagB (20 microg) alone or with MPL (25 microg). A group of nonimmunized mice served as control. Serum and saliva samples were collected prior to immunization and at approximately 2-week intervals and evaluated for serum immunoglobulin G (IgG) and IgG subclass and for salivary IgA antibody activity by enzyme-linked immunosorbent assay. Mice immunized with rHagB plus MPL had significantly higher salivary IgA (P < 0.05) and serum IgG (P < 0.05) anti-HagB responses than mice immunized with rHagB alone. The IgG1 and IgG2a subclass responses seen in mice immunized with rHagB plus MPL were significantly higher (P < 0.05) than those seen in mice immunized with rHagB only. Further, the IgG2a/IgG1 ratio in the latter group was approximately 1, whereas in mice immunized with rHagB plus MPL the ratio was <1. These results provide evidence for the participation of T helper (Th) 1 and Th2 cells in responses to rHagB and that MPL potentiates a type 2 response to HagB. MPL was also shown to preferentially up-regulate B7-2 expression on B cells, whereas a preferential increase in B7-1 costimulatory molecule was seen on macrophages and dendritic cells. These results provide evidence that MPL exerts a differential regulation in the expression of costimulatory molecules on APC.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: Qiu-Bo
authors.initials: QB
authors.lastname: Yang
authors.forename: Michael
authors.initials: M
authors.lastname: Martin
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Michalek
authors.forename: Jannet
authors.initials: J
authors.lastname: Katz
mesh_terms: D018829:Adhesins, Bacterial; D000276:Adjuvants, Immunologic; D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D018122:B7-1 Antigen / Q000276:immunology; D051940:B7-2 Antigen; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology*; D016866:Bacteroidaceae Infections / Q000276:immunology / Q000517:prevention & control*; D005260:Female; D005434:Flow Cytometry; D006388:Hemagglutinins / Q000235:genetics / Q000276:immunology*; D037102:Lectins; D008050:Lipid A / Q000031:analogs & derivatives* / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D012463:Saliva / Q000276:immunology; D014614:Vaccines, Synthetic / Q000235:genetics / Q000276:immunology*
chemical_list: D018829:Adhesins, Bacterial; D000276:Adjuvants, Immunologic; D000942:Antigens, Bacterial; D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; C497965:Cd86 protein, mouse; C098582:HagB protein, Porphyromonas gingivalis; D006388:Hemagglutinins; D037102:Lectins; D008050:Lipid A; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D014614:Vaccines, Synthetic; C048436:monophosphoryl lipid A