Evasion of human innate and acquired immunity by a bacterial homolog of CD11b that inhibits opsonophagocytosis.

Microbial pathogens must evade the human immune system to survive, disseminate and cause disease. By proteome analysis of the bacterium Group A Streptococcus (GAS), we identified a secreted protein with homology to the alpha-subunit of Mac-1, a leukocyte beta2 integrin required for innate immunity to invading microbes. The GAS Mac-1-like protein (Mac) was secreted by most pathogenic strains, produced in log-phase and controlled by the covR-covS two-component gene regulatory system, which also regulates transcription of other GAS virulence factors. Patients with GAS infection had titers of antibody specific to Mac that correlated with the course of disease, demonstrating that Mac was produced in vivo. Mac bound to CD16 (FcgammaRIIIB) on the surface of human polymorphonuclear leukocytes and inhibited opsonophagocytosis and production of reactive oxygen species, which resulted in significantly decreased pathogen killing. Thus, by mimicking a host-cell receptor required for an innate immune response, the GAS Mac protein inhibits professional phagocyte function by a novel strategy that enhances pathogen survival, establishment of infection and dissemination.

Streptococcal erythrogenic toxin B abrogates fibronectin-dependent internalization of Streptococcus pyogenes by cultured mammalian cells.

Streptococcus pyogenes secretes several proteins that influence host-pathogen interactions. A tissue-culture model was used to study the influence of the secreted cysteine protease streptococcal erythrogenic toxin B (SPE B) on the interaction between S. pyogenes strain NZ131 (serotype M49) and mammalian cells. Inactivation of the speB gene enhanced fibronectin-dependent uptake of the pathogen by Chinese hamster ovary (CHO-K1) cells compared to that in the isogenic wild-type strain. Preincubation of the NZ131 speB mutant with purified SPE B protease significantly inhibited fibronectin-dependent uptake by both CHO-K1 and CHO-pgs745 cells. The effect was attributed to an abrogation of fibronectin binding to the surface of the bacteria that did not involve either the M49 protein or the streptococcal fibronectin-binding protein SfbI. In contrast, pretreatment of the NZ131 speB mutant with SPE B did not influence sulfated polysaccharide-mediated uptake by CHO-pgs745 cells. The results indicate that the SPE B protease specifically alters bacterial cell surface proteins and thereby influences pathogen uptake.

Contrasting calcium dependencies of SAPK and ERK activations by glutamate in cultured striatal neurons.

Stress-activated protein kinase (SAPK) and extracellular signal-regulated kinase (ERK), both members of the mitogen-activated protein kinase (MAPK) family, may in some circumstances serve opposing functions with respect to cell survival. However, SAPK and ERK can also be coordinately activated in neurons in response to glutamate stimulation of NMDA receptors. To explore the mechanisms of these MAPK activations, we compared the ionic mechanisms mediating SAPK and ERK activations by glutamate. In primary cultures of striatal neurons, glutamatergic activation of ERK and one of its transcription factor targets, CREB, showed a calcium dependence typical of NMDA receptor-mediated responses. In contrast, extracellular calcium was not required for glutamatergic, NMDA receptor-mediated activation of SAPK and phosphorylation of its substrate, c-Jun. Increasing extracellular calcium enhanced ERK activation but reversed SAPK activation, further distinguishing the calcium dependencies of these two NMDA receptor-mediated effects. Finally, reducing extracellular sodium prevented the glutamatergic activation of SAPK but only partially blocked that of ERK. These contrasting ionic dependencies suggest a mechanism by which NMDA receptor activation may, under distinct conditions, differentially regulate neuronal MAPKs and their divergent functions.

Entry of OpaA+ gonococci into HEp-2 cells requires concerted action of glycosaminoglycans, fibronectin and integrin receptors.

Heparan sulphate proteoglycans are increasingly implicated as eukaryotic cell surface receptors for bacterial pathogens. Here, we report that Neisseria gonorrhoeae adheres to proteoglycan receptors on HEp-2 epithelial cells but that internalization of the bacterium by this cell type requires the serum glycoprotein fibronectin. Fibronectin was shown to bind specifically to gonococci producing the OpaA adhesin. Binding assays with fibronectin fragments located the bacterial binding site near the N-terminal end of the molecule. However, none of the tested fibronectin fragments supported gonococcal entry into the eukaryotic cells; a 120 kDa fragment carrying the cell adhesion domain with the amino acid sequence RGD even inhibited the fibronectin-mediated uptake of MS11-OpaA. This inhibition could be mimicked by an RGD-containing hexapeptide and by alpha 5 beta 1 integrin-specific antibodies, suggesting that interaction of the central region of fibronectin with integrin receptors facilitated bacterial uptake. Fibronectin was unable to promote gonococcal entry into HEp-2 cells that had been treated with the enzyme heparinase III, which degrades the glycosaminoglycan side-chains of proteoglycan receptors. On the basis of these results, we propose a novel cellular uptake pathway for bacteria, which involves the binding of the pathogen to glycosaminoglycans that, in turn, act as co-receptors facilitating fibronectin-mediated bacterial uptake through integrin receptors. In this scenario, fibronectin would act as a molecular bridge linking to Opa-proteoglycan complex with host cell integrin receptors.

Immunologic cross-reaction between HIV type 1 p17 and Mycoplasma hyorhinis variable lipoprotein.

Monoclonal antibodies directed against the HIV-1 matrix protein p17 that react with a component present on the surface of HIV-1-infected cells have previously been described. In this study we show that one of these monoclonal antibodies binds to persistently HIV-1-infected cell lines that are coinfected with Mycoplasma hyorhinis, but not to cell lines that are uninfected with mycoplasma. Mycoplasma-infected cells secrete HIV-1 at a higher rate, have a slight increase in cell surface expression of gp120 and gp41, and are less sensitive to immunotoxins than uninfected cells. The anti-p17 antibody binds to a protein of M. hyorhinis grown in cell-free culture. The variable expression and size of the protein among strains is typical of the variable lipoprotein (Vlp) system of M. hyorhinis. Confirmation of the reactivity of the antibody with a Vlp was provided by demonstrating its specific binding to recombinant VlpF expressed in E. coli, and to a synthetic peptide representing the carboxy-terminal region of VlpF, but not to other recombinant Vlp products or peptides. This is a true cross-reaction because the antibody also binds to recombinant p17 expressed in E. coli and the binding is inhibited by the VlpF peptide. These analyses highlight the potential of mycoplasma contamination of tissue culture cell lines to cause anomalous results. With regard to HIV-1, mycoplasma infection of cells results in increased rates of virus secretion, and introduces a potential confounding immunologic cross-reaction as well. The existence of a cell surface form of p17 is unlikely.

Glutamate, but not dopamine, stimulates stress-activated protein kinase and AP-1-mediated transcription in striatal neurons.

Drugs that stimulate dopamine and glutamate receptors have been shown to induce the expression of AP-1 proteins (such as c-Fos and c-Jun) in the striatum and to induce binding of these proteins to AP-1 sites on DNA, leading to the hypothesis that AP-1-mediated transcription contributes to the long-term effects of these drugs. To examine this hypothesis, we compared the regulation of AP-1-mediated transcription to the inductions of AP-1-binding activity and genes encoding AP-1 proteins in primary cultures of striatal neurons. Although glutamate, dopamine, and forskolin (an activator of adenylate cyclase) all induce c-fos mRNA and AP-1 binding, we found, surprisingly, that only glutamate induces transcription of a transfected AP-1-driven fusion gene. To explore the basis for this discrepancy, we investigated the possibility that the phosphorylation of c-Jun may also be required for AP-1-mediated transcription in striatal neurons. Glutamate, but neither dopamine nor forskolin, raises the levels of phosphorylated c-Jun as well as the activity of a Jun kinase (SAPK/JNK) in striatal cultures. Both the glutamatergic induction of AP-1-mediated transcription and activation of SAPK/JNK appear to be mediated, at least in part, via NMDA receptors. In striatal neurons, the phosphorylation of AP-1 proteins produced by glutamate may be required to convert AP-1 protein expression and binding to transcriptional activation.

Analysis of the proenkephalin second messenger-inducible enhancer in rat striatal cultures.

We have previously shown that in cell extracts from rat striatum, cyclic AMP response element (CRE) binding protein (CREB), rather than AP-1 proteins, preferentially interacts with the CRE-2 element of the proenkephalin second messenger-inducible enhancer, even under conditions in which AP-1 proteins are highly induced. Here we use primary striatal cultures to permit a more detailed analysis of CRE-2 function and protein binding in relevant neural cell types. By transfection we find that in primary striatal cultures, as in transformed cell lines, the CRE-1 and CRE-2 elements are required for significant induction by cyclic AMP. We report that cyclic AMP induction of the proenkephalin gene in striatal cultures is protein synthesis independent, excluding a role for newly synthesized proteins like c-Fos. We also show that cyclic AMP induces CREB phosphorylation and that phosphorylated CREB interacts strongly with CRE-2 and weakly with CRE-1. The predominant protein bound to CRE-1 is not CREB, however, and remains to be identified. Despite some prior predictions, we do not find a role for c-Fos in cyclic AMP regulation of proenkephalin gene expression in neurons.

Dopamine regulation of transcription factor-target interactions in rat striatum.

Transcriptional regulation is an important mechanism by which neurons adapt to environmental stimuli. The indirect dopamine agonists, amphetamine and cocaine have been shown to induce expression of immediate early genes, such as c-fos, and neuropeptide genes, such as prodynorphin in the rat striatum. Here we show that phosphorylation of transcription factor CREB is a critical early event coupling dopamine stimulation to gene regulation. CREB interacts with functional regulatory elements in both the c-fos and prodynorphin genes, and is phosphorylated in response to dopamine in a D1 dopamine receptor-dependent manner. In addition, we show by intra-striatal injection of antisense oligonucleotides directed against CREB mRNA, that CREB protein is required for c-fos induction by amphetamine.

Neuronal adaptation to amphetamine and dopamine: molecular mechanisms of prodynorphin gene regulation in rat striatum.

Induction of prodynorphin gene expression by psychostimulant drugs may represent a compensatory adaptation to excessive dopamine stimulation and may contribute to the aversive aspects of withdrawal. We therefore investigated the molecular mechanisms by which dopamine psychostimulant drugs induce prodynorphin gene expression in vivo and in rat primary striatal cultures. We demonstrate that three recently described cAMP response elements (CREs), rather than a previously reported noncanonical AP-1 site, are critical for dopamine induction of the prodynorphin gene in striatal neurons. CRE-binding protein (CREB) binds to these CREs in striatal cell extracts and is phosphorylated on Ser-133 after dopamine stimulation in a D1 dopamine receptor-dependent manner. Surprisingly, following chronic administration of amphetamine, levels of phosphorylated CREB are increased above basal in rat striatum in vivo, whereas c-fos mRNA is suppressed below basal levels. D1 receptor-mediated CREB phosphorylation appears to mediate adaptations to psychostimulant drugs in the striatum.

Amphetamine regulates gene expression in rat striatum via transcription factor CREB.

Amphetamine is a psychostimulant drug of abuse that can produce long-lived changes in behavior including sensitization and dependence. The neural substrates of these drug effects remain unknown, but based on their prolonged time course, we hypothesize that they involve drug-induced alterations in gene expression. It has recently been demonstrated that amphetamine regulates the expression of several genes, including c-fos, via dopamine D1 receptors in rat striatum. Here we report that amphetamine induces phosphorylation of transcription factor cAMP response element binding protein (CREB) in rat striatum in vivo and that dopamine D1 receptor stimulation induces phosphorylation of CREB within specific complexes bound to cAMP regulatory elements. In addition, we show by antisense injection that CREB is necessary for c-fos induction by amphetamine in vivo. Since CREB has been implicated in the activation of a number of immediate-early genes as well as several neuropeptide genes, CREB phosphorylation may be an important early nuclear event mediating long-term consequences of amphetamine administration.

Interaction of group B streptococcal opacity variants with the host defense system.

Group B streptococci (GBS) demonstrate high-frequency phase variation of colony opacity. Colony opacity is a function of chain length, with opaque colonies consisting of GBS that form longer chains. Because opaque variants do not grow on standard streptococcal media, the role of opacity variation in GBS infection has not been studied. We have isolated stable variants from type III GBS that are either transparent (variants 1.2 and 1.3) or opaque (variants 1.1 and 1.5). In this study, we evaluated the interactions of these variants with different components of the host immune system both in vitro and in vivo. Opaque GBS were less immunogenic than transparent GBS. Opaque GBS were more susceptible to killing by polymorphonuclear neutrophils (PMNs) and could induce a chemiluminescent response of PMNs in the absence of antibody (Ab) or complement. Transparent GBS did not induce neutrophil chemiluminescence in the absence of Ab and complement. However, in the presence of Ab and complement, transparent GBS induced a stronger chemiluminescent response than did opaque GBS. Scanning electron micrographs of PMNs and GBS demonstrated differences in the attachment and engulfment of the different variants by the PMNs as well as different effects of the GBS on the PMNs themselves. Interactions with complement were affected by GBS opacity as well, with opaque variant 1.1 initiating complement activation in the absence of any Ab. The virulence of the GBS opacity variants was studied in vivo by inoculation of graded numbers of GBS into newborn mice. Transparent variants 1.2 and 1.3 were most virulent, with variant 1.1 intermediate and variant 1.5 minimally virulent. However, in mixed infections, variant 1.5 greatly enhanced the virulence of small numbers of transparent GBS. These results indicate that the opacity status of GBS can influence the interaction between the GBS and the host immune system.

Melorheostosis on three-phase bone scintigraphy. Case report.

Melorheostosis is a benign sclerosing bone dysplasia with a very unusual and characteristic roentgenographic appearance. Its scintigraphic appearance also is characteristic, with asymmetric cortical activity that may cross joints to involve contiguous bones. The authors report the appearance of melorheostosis on angiogram and blood pool phases of three-phase bone scintigraphy.

Group B streptococcal opacity variants.

Colony opacity variants were detected for type III group B streptococci (GBS). Transparent colonies predominate in the parent GBS, with occasional colonies having opaque portions. Two stable opaque variants (1.1 and 1.5) were compared with three transparent clones (1.2, 1.3, and 1.4). All grew well on blood agar and on GC medium, but variant 1.1 failed to grow on Todd-Hewitt medium. Scanning and transmission electron microscopy demonstrated that colony opacity correlated with bacterial aggregation status, with opaque variants forming longer and more organized chains. Opaque-transparent switches were observed in both directions for most variants, with transparent to opaque noted most frequently, but 1.5 did not switch at all. Switching of the opacity phenotype was observed both in vitro and in neonatal mice. Relationships between colony opacity and several cell surface phenomena were explored. (i) Opaque variant 1.1 had two surface proteins (46 and 75 kDa) that were either unique or greatly overexpressed. (ii) Variant 1.1 was deficient in type III polysaccharide, while 1.5 lacked group B antigen. Diminished capsular polysaccharide of variant 1.1 was reflected in reduced negative electrophoretic mobility and in increased buoyant density. (iii) Transparent variant colonies growing closest to a penicillin disk were opaque, but colonial variants did not differ in their sensitivity to penicillin. These data indicate that GBS can exist in both opaque and transparent forms, with opaque appearance occurring by multiple routes. Opaque variants grow poorly on Todd-Hewitt medium generally used for isolation of GBS, so any possible relationships between opacity variation and pathogenesis of GBS infection are unknown.

In vitro efficacy of anti-HIV immunotoxins targeted by various antibodies to the envelope protein.

Six different anti-HIV envelope antibodies and one irrelevant control antibody were coupled to ricin A chain and tested for their efficacy in inhibiting HIV tissue culture infections. The anti-HIV antibodies consisted of five monoclonals, three of murine and two of human origin, and one polyclonal preparation prepared by affinity purifying pooled serum antibodies from HIV-infected humans on rgp160. The binding specificity of the antibodies was defined by ELISA by using recombinant envelope proteins and synthetic peptides, and by flow cytometry on HIV-infected cells. The in vitro efficacy of the antibodies was tested by the abilities of the immunotoxins to inhibit protein synthesis in persistently infected cell lines and by their abilities to inhibit HIV production during both acute and persistent infection as measured with an HIV-specific focal immunoassay. The immunotoxins were tested against a panel of distinctly different HIV isolates. The results indicate the following: 1) A mAb to the immunodominant neutralizing loop was highly effective against homologous strains of HIV, but had no activity against heterologous HIV. 2) The efficacy of anti-gp41 mAb varied depending upon the epitope recognized and possibly the affinity of binding to gp41. 3) The polyclonal human anti-gp160 antibodies produced the immunotoxin with the broadest specificity for different HIV strains and the greatest specific activity. This is related to the polyclonal nature of the preparation rather than an increase in relative avidity of the antibody. 4) Activity of an immunotoxin is not a direct function of the binding of the antibody to the surface of infected cells. 5) The ability of an immunotoxin to halt the spread of infection through a tissue culture cell population is dependent upon the ability of the antibody to neutralize the virus as well as the activity of the toxin. Our data suggest that efficacious immunotoxins for the treatment of AIDS may be made with polyclonal anti-envelope antibodies derived from the serum of patients who have been infected with HIV or with appropriately chosen anti-gp41 antibodies.

Bone and gallium scan findings in malignant fibrous histiocytoma. Case report with radiographic and pathologic correlation.

Malignant fibrous histiocytoma (MFH) is the most common soft tissue malignancy in adults. The Ga-67 citrate scan findings of an extremity-located MFH, the most common location of this neoplasm, have never been published in English language journals to the best of the authors' knowledge. Ga-67 citrate and Tc-99m MDP scans of the thigh mass accurately depicted the tumor's local extent, including the presence of central ischemic necrosis within the tumor, and the absence of adjacent osseous involvement and distant metastases, as correlated with computed tomography, angiography, and pathologic examinations.

Plasmid Involvement in Linalool Metabolism by Pseudomonas fluorescens.

A bacterial strain was isolated from a wastewater lagoon and identified as Pseudomonas fluorescens. This isolate was able to utilize linalool as a sole carbon and energy source. The ability was found to be encoded on a 60-megadalton transmissible plasmid, pSRQ60. The plasmid was also mated into a commercial waste treatment strain, which expanded its ability to utilize other isoprenoid compounds.

Cloning and Expression in Escherichia coli of the Polysaccharide Depolymerase Associated with Bacteriophage-Infected Erwinia amylovora.

The bacteriophage-encoded polysaccharide depolymerase produced in Erwinia amylovora has been cloned and expressed in Escherichia coli. The bacteriophage ERA103 genome was observed to consist of five EcoRI fragments, labeled as follows: A, 7.5 kilobases (kb); B, 5.0 kb; C, 2.7 kb; D, 2.1 kb; and E, 1.8 kb. A restriction map for ERA103 was also prepared. Each of the fragments were cloned into the positive-selection vector pOP203(A(2)) and pBR322.

Lipopolysaccharide variation in Coxiella burnetti: intrastrain heterogeneity in structure and antigenicity.

We isolated lipopolysaccharides (LPSs) from phase variants of Coxiella burnetii Nine Mile and compared the isolated LPS and C. burnetii cells by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The LPSs were found to be the predominant component which varied structurally and antigenically between virulent phase I and avirulent phase II. A comparison of techniques historically used to extract the phase I antigenic component revealed that the aqueous phase of phenol-water, trichloroacetic acid, and dimethyl sulfoxide extractions of phase I C. burnettii cells all contained phase I LPS, although the efficiency and specificity of extraction varied. Our studies provide additional evidence that phase variation in C. burnetii is analogous to the smooth-to-rough LPS variation of gram-negative enteric bacteria, with phase I LPS being equivalent to smooth LPS and phase II being equivalent to rough LPS. In addition, we identified a variant with a third LPS chemotype with appears to have a structural complexity intermediate to phase I and II LPSs. All three C. burnetii LPS contain a 2-keto-3-deoxyoctulosonic acid-like substance, heptose, and gel Limulus amoebocyte lysates in subnanogram amounts. The C. burnetii LPSs were nontoxic to chicken embryos at doses of over 80 micrograms per embryo, in contrast to Salmonella typhimurium smooth- and rough-type LPSs, which were toxic in nanogram amounts.