Ann L. Sandberg

Complement-Dependent Stimulation of Prostaglandin Synthesis and Bone Resorption

Complement-sufficient heterologous serum induced prostaglandin synthesis and resultant resorption in cultures of fetal rat long bones. Bone resorption was enhanced with unheated normal rabbit serum as compared to heated serum or serum from rabbits lacking the sixth component of complement (C6). Addition of functionally purified C6 restored resorptive activity in C6-deficient serum. Concentrations of prostaglandin E were increased in the culture media of bones incubated with complement-sufficient serum. The resorptive effects of active serum as well as the appearance of prostaglandin E in the media were inhibited by indomethacin.

Salivary Receptors for the Proline-rich Protein-binding and Lectin-like Adhesins of Oral Actinomyces and Streptococci

Colonization of the tooth surface by actinomyces and viridans group streptococci involves the attachment of these bacteria to adsorbed salivary components of the acquired enamel pellicle. The hypothesis that this attachment depends on specific adhesins has now been assessed from the binding of bacteria with well-defined adhesive properties to blots of SDS-PAGE-separated parotid and submandibular-sublingual (SM-SL) saliva. Streptococcus sanguis and type 2 fimbriated Actinomyces naeslundii, which bound terminal sialic acid and Galβ1-3GalNAc, respectively, recognized only a few SM-SL salivary components, primarily MG2. In contrast, type 1 fimbriated A. naeslundii and S. gordonii, which bound purified proline-rich proteins (PRPs), recognized several other components from both SM-SL and parotid saliva. Significantly, bacteria that lacked PRP-binding and the lectin-like activities detected by binding to MG2 failed to bind any immobilized salivary component. These findings suggest the involvement of specific adhesins in bacterial recognition of many adsorbed salivary proteins and glycoproteins.

Characterization of mouse allergens.

The major allergens present in mouse skin, serum, and urine have been identified. Skin extracts, serum, and urine were chromatographed, and the activities of the fractions were monitored by histamine release from the leukocytes of individuals sensitive to mice. Fractionation of skin extracts revealed two major allergens. The large allergen has a molecular weight of approximately 67,000 daltons and by biochemical and immunochemical criteria appears to be identical to mouse albumin. The smaller molecular weight allergen is approximately 17,000 daltons. The same two allergens are also found in mouse serum and mouse urine. Histamine release by leukocytes of individuals allergic to mice demonstrated that some individuals react predominantly to the large allergen, some to the small allergen, and one group of patients reacts to both allergens.

Identification of Polymorphonuclear Leukocyte and HL-60 Cell Receptors for Adhesins of Streptococcus gordonii and Actinomyces naeslundii

ABSTRACT Interactions of oral streptococci and actinomyces with polymorphonuclear leukocytes (PMNs), mediated by sialic acid- and Gal/GalNAc-reactive adhesins, respectively, result in activation of the PMNs and thereby may contribute to the initiation of oral inflammation. Sialidase treatment of PMNs or HL-60 cells abolished adhesion ofStreptococcus gordonii but was required for adhesion ofActinomyces naeslundii. The same effects of sialidase were noted for adhesion of these bacteria to a major 150-kDa surface glycoprotein of either PMNs or undifferentiated HL-60 cells and to a 130-kDa surface glycoprotein of differentiated HL-60 cells. These glycoproteins were both identified as leukosialin (CD43) by immunoprecipitation with a specific monoclonal antibody (MAb). Adhesion of streptococci and actinomyces to a 200-kDa minor PMN surface glycoprotein was also detected by bacterial overlay of untreated and sialidase-treated nitrocellulose transfers, respectively. This glycoprotein was identified as leukocyte common antigen (CD45) by immunoprecipitation with a specific MAb. CD43 and CD45 both possess extracellular mucinlike domains in addition to intracellular domains that are implicated in signal transduction. Consequently, the interactions of streptococci and actinomyces with the mucinlike domains of these mammalian cell surface glycoproteins result not only in adhesion but, in addition, may represent the initial step in PMN activation by these bacteria.

The Function and Distribution of Different Fimbriae on Strains of Actinomyces viscosus and Actinomyces naeslundii

Actinomyces viscosus and Actinomyces naeslundii differ in their abilities to colonize tooth and epithelial surfaces. These differences appear to be associated with the distribution of different fimbriae on the two species and with the distinct adherence-related functions of these structures.

Specific Inhibitors of Bacterial Adhesion: Observations From the Study of Gram-Positive Bacteria that Initiate Biofilm Formation on the Tooth Surface

Oral surfaces are bathed in secretory antibodies and other salivary macromolecules that are potential inhibitors of specific microbial adhesion. Indigenous Gram-positive bacteria that colonize teeth, including viridans streptococci and actinomyces, may avoid inhibition of adhesion by host secretory molecules through various strategies that involve the structural design and binding properties of bacterial adhesins and receptors. Further studies to define the interactions of these molecules within the host environment may suggest novel approaches for the control of oral biofilm formation.

Resistance of Streptococcus gordonii to Polymorphonuclear Leukocyte Killing Is a Potential Virulence Determinant of Infective Endocarditis

ABSTRACT Significant differences in virulence among seven representative Streptococcus gordonii strains were observed by using the rat model of infective endocarditis. Five strains, including S. gordonii DL1, caused severe disease, while the other two strains, including S. gordonii SK12, caused minimal or no disease. The differences in virulence were evident from the visible presence of streptococci in the vegetations present on the aortic valves of catheterized rats that were challenged with individual strains and also from the much greater recovery of rifampin-resistant S. gordonii DLl than of streptomycin-resistant S. gordonii SK12 from the hearts of animals coinfected with both organisms. Each S. gordonii strain aggregated with human platelets and bound to polymorphonuclear leukocytes (PMNs), as shown by the stimulation of PMN superoxide anion production. These interactions were reduced or abolished by pretreatment of the platelets or PMNs with sialidase, indicating that there was bacterial recognition of host sialic acid-containing receptors. Adhesin-mediated binding of each S. gordonii strain to PMNs also triggered phagocytosis. However, the subsequent PMN-dependent killing differed significantly for the seven strains. The five virulent strains included three strains that were not killed and two strains whose numbers were reduced by approximately 50%. In contrast, the level of killing of each avirulent strain under the same conditions was significantly greater and approached 90% of the bacteria added. Parallel studies performed with rat PMNs revealed comparable differences in the resistance or susceptibility of representative virulent and avirulent strains. Thus, the ability of S. gordonii to survive in PMNs following adhesin-mediated phagocytosis may be an important virulence determinant of infective endocarditis.

In vitro effects of antitumor antibody--chemotactic factor complexes.

Abstract Antitumor antibodies with in vitro chemotactic activity for guinea pig peritoneal exudate macrophages and polymorphonuclear leukocytes were obtained by covalent linkage of the chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (fMLP) to rabbit IgG reactive with a strain 13 guinea pig hepatoma. In addition to its chemotactic properties, the fMLP coupled to antibody also retained its ability to stimulate the production of superoxide anions by macrophages. Neither the IgG nor the IgG treated with the carbodiimide coupling reagent exhibited any of these biological activities. The antibodies, which were adsorbed with sheep erythrocytes and normal strain 13 liver cells prior to the coupling procedure, reacted with surface antigens present on the hepatoma cells but not with those on fibrosarcoma cells or fibroblasts as determined by complement-dependent cytotoxicity. This complement-mediated function was, however, greatly diminished by coupling the IgG to fMLP although indirect immunofluorescent staining patterns established binding of the complexes to hepatoma cells but not to normal liver cells. When bound to tumor cells the antibody-peptide conjugates were also chemotactic, implying that the conjugated antibodies, conjugated antibody-tumor antigen complexes, or fMLP may be released and establish an effective chemotactic gradient for peritoneal exudate cells in vitro.

Enhancement of macrophage invasion of tumors by administration of chemotactic factor-antitumor antibody conjugates.

The numbers of macrophages in peritoneal guinea pig hepatomas were significantly (P less than 0.005) elevated by the intraperitoneal injection of a covalent conjugate of the chemotactic peptide, formylmethionylleucylphenylalanine (fMLP), and IgG reactive with surface antigens on the hepatoma cells. These conjugates, which were previously shown to be chemotactic for guinea pig peritoneal exudate macrophages in vitro, increased the numbers of macrophages in the tumors approximately twofold when injected either in a single dose or in five doses. Although five injections of unconjugated fMLP were nearly as effective as the IgG-fMLP conjugates, free fMLP did not enhance the numbers of macrophages in tumors when injected as a single dose. Unconjugated IgG had no effect. The mean tumor weights were decreased in those groups of guinea pigs which received IgG-fMLP but statistical significance was not achieved due to tumor weight variability in all groups.

Activation of serum complement inhibits collagen synthesis in fetal rat bone in organ culture

SummaryActivation of rabbit serum complement caused a marked reduction in collagen synthesis but a much smaller change in noncollagen protein synthesis in fetal rat calvaria maintained in organ culture. In the periosteum of the fetal rat calvarium, both collagen and noncollagen protein synthesis were reduced, whereas in the central bone, presumably enriched in osteoblasts, only collagen synthesis was inhibited. This large decrease in bone collagen synthesis could not be attributed to enhanced degradation of newly synthesized collagen or its release into the culture medium. Activation of complement also stimulated the production of PGE in fetal rat calvaria. Antagonists of prostaglandin cyclooxygenase decreased prostaglandin synthesis but did not restore collagen synthesis in complement-treated bones, suggesting that complement decreases osteoblast collagen synthesis by a mechanism largely independent of prostaglandin production.