The (alpha2-->8)-linked polysialic acid capsule and lipooligosaccharide structure both contribute to the ability of serogroup B Neisseria meningitidis to resist the bactericidal activity of normal human serum

The molecular basis for the resistance of serogroup B Neisseria meningitidis to the bactericidal activity of normal human sera (NHS) was examined with a NHS-resistant, invasive serogroup B meningococcal isolate and genetically and structurally defined capsule-, lipooligosaccharide (LOS)-, and sialylation-altered mutants of the wild-type strain. Expression of the (alpha2-->8)-linked polysialic acid serogroup B capsule was essential for meningococcal resistance to NHS. The very NHS-sensitive phenotype of acapsular mutants (99.9 to 100% killed in 10, 25, and 50% NHS) was not rescued by complete LOS sialylation or changes in LOS structure. However, expression of the capsule was necessary but not sufficient for a fully NHS-resistant phenotype. In an encapsulated background, loss of LOS sialylation by interrupting the alpha2,3 sialyltransferase gene, lst, increased sensitivity to 50% NHS. In contrast, replacement of the lacto-N-neotetraose alpha-chain (Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc) with glucose extensions (GlcN) in a galE mutant resulted in a strain resistant to killing by 50% NHS at all time points. Encapsulated meningococci expressing a Hep2(GlcNAc)-->KDO2-->lipid A LOS without an alpha-chain demonstrated enhanced sensitivity to 50% NHS (98% killed at 30 min) mediated through the antibody-dependent classical complement pathway. Encapsulated LOS mutants expressing truncated Hep2-->KDO2-->lipid A and KDO2-->lipid A structures were also sensitive to 50% NHS (98 to 100% killed at 30 min) but, unlike the wild-type strain and mutants with larger oligosaccharide structures, they were killed by hypogammaglobulinemic sera. These data indicate that encapsulation is essential but that the LOS structure contributes to the ability of serogroup B N. meningitidis to resist the bactericidal activity of NHS.     

Adherence of Streptococcus pneumoniae to human bronchial epithelial cells (BEAS-2B)

Pneumococcal adherence to alveolar epithelial cells and nasopharyngeal epithelial cells has been well characterized. However, the interaction of Streptococcus pneumoniae with bronchial epithelial cells has not been studied. We have now shown that pneumococci bind specifically to a human bronchial epithelial cell line (BEAS-2B cells). Pneumococci adhered to BEAS-2B cells in a time- and dose-dependent manner. These results suggest that the bronchial epithelium may serve as an additional site of attachment for pneumococci and demonstrate the utility of the BEAS-2B cell line for studying mechanisms of pneumococcal infection.     

Characterization of a sialyltransferase-deficient mutant of Neisseria gonorrhoeae strain F62: instability of transposon Tn1545 delta3 in gonococci and evidence that multiple genetic loci are essential for lipooligosaccharide sialylation

Neisseria gonorrhoeae strain JB1 was previously shown to be defective in the sialylation of lipoologosaccharide (LOS) by exogenous CMP-NANA. The LOS components synthesized by the mutant now have been shown by mass spectrometry to be similar to those in the parental strain, F62, and to include the 4.5 kDa widely conserved lacto-N-neotetraose component that can be sialylated. The same two LOS components could be sialylated on the surface of the mutant and parental strains. One major component was sialylatable after chemical extraction of the LOS from either strain. These data confirm that the mutant, JB1, retains the ability to synthesize the LOS target required for the conversion by sialylation of serum-sensitive gonococci to serum resistance. A single base frame-shift mutation was found in the lst gene from the mutant, resulting in the replacement of the final 61 amino acids at the C-terminus of the sialyltransferase by four residues. Seventeen independent clones of the lst gene were isolated from the parental strain, but none of them complemented the sialyltransferase defect of the mutant and no sialyltransferase activity expressed from the clones could be detected in Escherichia coli. Although the data suggest that the mutant might be defective in genes at more than one chromosomal locus and that multiple loci are essential for sialyltransferase synthesis and activity, the alternative possibility, that DNA adjacent to the lst gene encodes a product which is toxic to E. coli, cannot be excluded. The site of insertion of the transposon Tn1545-Delta3 in strain JB1 was cloned and sequenced. The transposon is located in an intergenic region adjacent to genes for a putative ATP-dependent transport protein, but encoding no recognizable function relevant to LOS sialylation. Evidence that transposon Tn1545-Delta3 is unstable in gonococci is presented.     

Structure of a neutralizing antibody bound monovalently to human rhinovirus 2

The structure of a complex between human rhinovirus 2 (HRV2) and the Fab fragment of neutralizing monoclonal antibody (MAb) 3B10 has been determined to 25-A resolution by cryoelectron microscopy and three-dimensional reconstruction techniques. The footprint of 3B10 on HRV2 is very similar to that of neutralizing MAb 8F5, which binds bivalently across the icosahedral twofold axis. However, the 3B10 Fab fragment (Fab-3B10) is bound in an orientation, inclined at approximately 45 degrees to the surface of the virus capsid, which is compatible only with monovalent binding of the antibody. The canyon around the fivefold axis is not directly obstructed by the bound Fab. The X-ray structures of a closely related HRV (HRV1A) and a Fab fragment were fitted to the density maps of the HRV2-Fab-3B10 complex obtained by cryoelectron microscope techniques. The footprint of 3B10 on the viral surface is largely on VP2 but also covers the VP3 loop centered on residue 3064 and the VP1 loop centered on residue 1267. MAb 3B10 can interact directly with VP2 residue 2164, the site of an escape mutation on VP2, and with VP1 residues 1264 to 1267, the site of a deletion escape mutation. Deletion of these residues shortens the VP1 loop, moving it away from the MAb binding site. All structural and biochemical evidence indicates that MAb 3B10 binds to a conformation epitope on HRV2.     

Monoclonal antibody to the type II Fc receptor for human IgG blocks potentiation of monocyte and neutrophil IgG-induced respiratory burst activation by aggregated C-reactive protein

The acute phase protein, CRP, when heat-aggregated (Agg-CRP), binds to human monocytes and neutrophils and potentiates the respiratory burst stimulated by heat-aggregated IgG (Agg-IgG). Earlier data from our laboratory and others have indicated that CRP binds to phagocytic cells at membrane sites associated with IgG Fc receptors. The present study utilized monoclonal antibodies (MAb) to determine whether the Agg-CRP potentiation of oxidative metabolism could be linked to activation through Fc gamma RI, Fc gamma RII, or Fc gamma RIII. Preincubation of monocytes with MAb 32.2, which recognizes an Fc gamma RI epitope distinct from its IgG binding site, had only a minimal (20%) inhibitory effect on Agg-IgG-induced luminol chemiluminescence (CL) and exerted no significant effect on its enhancement by Agg-CRP. MAb 10.1, which blocks IgG binding to Fc gamma RI, reduced Agg-IgG-induced monocyte CL by 40%, but did not alter the Agg-CRP-mediated enhancement. In contrast, exposure to MAb IV.3, which binds to Fc gamma RII on monocytes and neutrophils and blocks IgG binding to this receptor, resulted in a greater than 70%, inhibition of Agg-IgG-induced CL and also significantly suppressed the enhancement by Agg-CRP. MAb Leu-11b, which reacts with Fc gamma RIII on neutrophils, reduced Agg-IgG-induced CL by 70% but did not suppress the Agg-CRP potentiation. Preincubation of monocytes and neutrophils with anti-Leu-M1, anti-CR1, or anti-CR3 failed to block Agg-IgG-induced CL or its enhancement by Agg-CRP. Although the potentiating effect of Agg-CRP on Agg-IgG-elicited CL was blocked by MAb IV.3, this antibody failed to reduce binding of Agg-CRP to either monocytes or neutrophils. These results indicate that, although Agg-CRP does not bind to phagocytic cells at the IgG-binding determinant of Fc gamma RII, it alters Agg-IgG-induced cell activation through this receptor.     

Immune regulation by the ST6Gal sialyltransferase

The ST6Gal sialyltransferase controls production of the Siaalpha2-6Galbeta1-4GlcNAc (Sia6LacNAc) trisaccharide, which is the ligand for the lectin CD22. Binding of CD22 to Sia6LacNAc is implicated in regulating lymphocyte adhesion and activation. We have investigated mice that lack ST6Gal and report that they are viable, yet exhibit hallmarks of severe immunosuppression unlike CD22-deficient mice. Notably, Sia6LacNAc-deficient mice display reduced serum IgM levels, impaired B cell proliferation in response to IgM and CD40 crosslinking, and attenuated antibody production to T-independent and T-dependent antigens. Deficiency of ST6Gal was further found to alter phosphotyrosine accumulation during signal transduction from the B lymphocyte antigen receptor. These studies reveal that the ST6Gal sialyltransferase and corresponding production of the Sia6LacNAc oligosaccharide are essential in promoting B lymphocyte activation and immune function.     

In vivo evidence that the stromelysin-3 metalloproteinase contributes in a paracrine manner to epithelial cell malignancy

Stromelysin-3 (ST3; Basset, P., J.P. Bellocq, C. Wolf, I. Stoll, P. Hutin, J.M. Limacher, O.L. Podhajcer, M.P. Chenard, M.C. Rio, P. Chambon. 1990. Nature. 348:699-704) is a matrix metalloproteinase (MMP) expressed in mesenchymal cells located close to epithelial cells, during physiological and pathological tissue remodeling processes. In human carcinomas, high ST3 levels are associated with a poor clinical outcome, suggesting that ST3 plays a role during malignant processes. In this study we report the ST3 gene inactivation by homologous recombination. Although ST3 null mice (ST3-/-) were fertile and did not exhibit obvious alterations in appearance and behavior, the lack of ST3 altered malignant processes. Thus, the suppression of ST3 results in a decreased 7, 12-dimethylbenzanthracene-induced tumorigenesis in ST3-/- mice. Moreover, ST3-/- fibroblasts have lost the capacity to promote implantation of MCF7 human malignant epithelial cells in nude mice (P < 0.008). Finally, we show that this ST3 paracrine function requires extracellular matrix (ECM)-associated growth factors. Altogether, these findings give evidence that ST3 promotes, in a paracrine manner, homing of malignant epithelial cells, a key process for both primary tumors and metastases. Therefore, ST3 represents an appropriate target for specific MMP inhibitor(s) in future therapeutical approaches directed against the stromal compartment of human carcinomas.     

Mouse beta-galactoside alpha 2,3-sialyltransferases: comparison of in vitro substrate specificities and tissue specific expression

Four types of beta-galactoside alpha 2,3-sialyltransferase (ST3Gal I-IV) have been cloned from several animals, but some contradictory observations regarding their substrate specificities and expression have been reported. Therefore, it is necessary to concurrently analyze the substrate specificities of the four enzymes, of which the source should be one animal. Accordingly, the acceptor substrate specificities and gene expression of mST3Gal I-IV were analyzed. Since we had already cloned ST3Gal I and II, as previously reported (Lee, Y.-C. et al., Eur. J. Biochem., 216, 377-385 (1993); J. Biol. Chem., 269, 10028-10033 (1994)), the cDNAs of ST3Gal III and IV were cloned from mouse cDNA libraries. Each of the four enzymes was expressed in COS-7 cells as a recombinant enzyme fused with protein A, and applied on an IgG-Sepharose gel to eliminate endogenous sialyltransferase activity. ST3Gal I and II showed the highest activity toward Gal beta 1, 3 GalNAc (type III), very low activity toward Gal beta 1,3GlcNAc (type I), but none toward Gal beta 1,4GlcNAc (type II). ST3Gal III and IV exhibited high activity toward the type I and II disaccharides, but very low activity toward the type III one. On the other hand, asialo-GM1 (Gg4Cer) was as good a substrate for ST3Gal I and II as the type III disaccharide, though ST3Gal III and IV hardly utilized glycolipids as substrates, as indicated by in vitro experiments. Northern blot analysis revealed that enzymes of the ST3Gal-family are expressed mainly in a tissue-specific manner. The ST3Gal I gene was strongly expressed in spleen and salivary gland, and weakly in brain, liver, heart, kidney, and thymus. The ST3Gal II gene was strongly expressed in brain, and weakly in colon, thymus, salivary gland, and testis, and developmentally expressed in liver, heart, kidney, and spleen. The ST3Gal III and IV genes were expressed in a wide variety of tissues. These differences in tissue specific expression suggest the expression of each ST3Gal influences the distribution of sialyl-glycoconjugates in vivo.     

Inhibitory monoclonal antibody to human cytochrome P450 2B6

The human cytochrome P450 2B6 metabolizes, among numerous other substrates, diazepam, 7-ethoxycoumarin, testosterone, and phenanthrene. A recombinant baculovirus containing the human 2B6 cDNA was constructed and used to express 2B6 in Sf9 insect cells. The 2B6 was present at 1.8 +/- 0.4% of the total cellular protein and was purified to a specific content of 13.3 nmol/mg protein. Mice were immunized with the purified 2B6, and a total of 811 hybridomas were obtained from the fusion of NS-1 myeloma cells and spleen cells of the immunized mice. Monoclonal antibodies (MAbs) from 24 of the hybrids exhibited immunobinding to 2B6 as determined by ELISA. One of the MAbs, 49-10-20, showed a strong immunoblotting activity and was highly inhibitory to 2B6 enzyme activity. MAb 49-10-20 inhibited cDNA-expressed 2B6-catalyzed metabolism of diazepam, phenanthrene, 7-ethoxycoumarin, and testosterone by 90-91%. MAb 49-10-20 showed extremely high specificity for 2B6 and did not bind to 17 other human and rodent P450s or inhibit the metabolism of phenanthrene catalyzed by human 1A2, 2A6, 2C8, 2C9, 2D6, 2E1, 3A4, and 3A5. MAb 49-10-20 was used to determine the contribution of 2B6 to the metabolism of phenanthrene and diazepam in human liver. In ten liver samples, MAb 49-10-20 inhibited phenanthrene metabolism variably by a wide range of 8-42% and diazepam demethylation by 1-23%. The degree of inhibition by the 2B6 specific MAb 49-10-20 defines the contribution of 2B6 to phenanthrene and diazepam metabolism in each human liver. This technique using inhibitory MAb 49-10-20 determines the contribution of 2B6 to the metabolism of its substrates in a human tissue containing multiple P450s. This study is a prototype for the use of specific and highly inhibitory MAbs to determine individual P450 function.     

Preparation of an activity-inhibiting monoclonal antibody against human placental aromatase cytochrome P450

We produced a murine monoclonal antibody (MAb) to human placental aromatase cytochrome P450. This MAb, designated MAb3-2C2, was selected on its ability to suppress aromatase activity. The specificity of this MAb was assessed by selective immunoprecipitation of 125I-labeled aromatase cytochrome P450 as well as by the identification of a 55-kDa protein, which was enriched and purified by immunoaffinity chromatography on a MAb-coupled Sepharose 4B column. The MAb was able to suppress both human placental and ovarian microsomal aromatase. Species differences of aromatase were recognized by MAb3-2C2 on the basis of differential immunosuppression of aromatase activity. The antibody had no effect on non-aromatase cytochrome P450s. MAb3-2C2 gave negative results with human placental aromatase P450 in the Western blot analysis. The data presented indicate that MAb3-2C2 is specific for aromatase cytochrome P450 and that its epitope is located in a fragile tertiary conformation of the enzyme, thus making it capable of sensitively affecting catalysis.     

Monosialogangliosides of human myelogenous leukemia HL60 cells and normal human leukocytes. 2. Characterization of E-selectin binding fractions, and structural requirements for physiological binding to E-selectin

E-selectin binding gangliosides were isolated from myelogenous leukemia HL60 cells, and the E-selectin binding pattern was compared with that of human neutrophils as described in the preceding paper in this issue. The binding fractions were identified as monosialogangliosides having a series of unbranched polylactosamine cores. Structures of fractions 12-3, 13-1, 13-2, and 14, which showed clear binding to E-selectin under the conditions described in the preceding paper, were characterized by functional group analysis by application of monoclonal antibodies, 1H-NMR, FAB-MS, and electrospray mass spectrometry with collision-induced dissociation of permethylated fractions. Fractions 12-3, 13-1, and 13-2 were characterized by the presence of a major ganglioside with the following structure: NeuAc alpha 2-->3Gal beta 1-->4 GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3) GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3)-GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->4 Glc beta Cer. Fractions 12-3 and 13-2 contained, in addition, small quantities (10-15%) of extended SLex with internally fucosylated structures: NeuAc alpha 2-->3 Gal beta 1-->4-(Fuc alpha 1-->3) GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3) GlcNAc beta 1-->3 Gal beta 1-->4 (+/- Fuc alpha 1-->3)GlcNA c beta 1-->3 Gal beta beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->Glc Beta Cer. Fraction 13-1, showing stronger E-selectin binding activity than 12-3 and 13-2, contained only a trace quantity (< 1%) of SLex. Fraction 14, which also showed clear binding to E-selectin, was characterized by the presence of the following structures, in addition to two internally monofucosylated structures (XX and XXI, Table 2, text): NeuAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3Gal beta 1-->4 GlcNAc beta 1-->3 Gal beta 1-->4 GlcNAc beta 1-->3 Gal beta 1-->4 Glc beta Cer; andNeuAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4 (Fuc alpha 1--3)-GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1--4Glc beta Cer. SLex determinant was completely absent. Thus, the E-selectin binding epitope in HL60 cells is carried by unbranched terminally alpha 2-->3 sialylated polylactosamine having at least 10 monosaccharide units (4 N-acetyllactosamine units) with internal multiple fucosylation at GlcNAc. These structures are hereby collectively called "myeloglycan". Monosialogangliosides from normal human neutrophils showed an essentially identical pattern of gangliosides with selectin binding property. Myeloglycan, rather than SLex, provides a major physiological epitope in E-selectin-dependent binding of leukocytes and HL60 cells.     

Generation of neutralizing human monoclonal antibodies against parvovirus B19 proteins

Infections caused by human parvovirus B19 are known to be controlled mainly by neutralizing antibodies. To analyze the immune reaction against parvovirus B19 proteins, four cell lines secreting human immunoglobulin G monoclonal antibodies (MAbs) were generated from two healthy donors and one human immunodeficiency virus type 1-seropositive individual with high serum titers against parvovirus. One MAb is specific for nonstructural protein NS1 (MAb 1424), two MAbs are specific for the unique region of minor capsid protein VP1 (MAbs 1418-1 and 1418-16), and one MAb is directed to major capsid protein VP2 (MAb 860-55D). Two MAbs, 1418-1 and 1418-16, which were generated from the same individual have identity in the cDNA sequences encoding the variable domains, with the exception of four base pairs resulting in only one amino acid change in the light chain. The NS1- and VP1-specific MAbs interact with linear epitopes, whereas the recognized epitope in VP2 is conformational. The MAbs specific for the structural proteins display strong virus-neutralizing activity. The VP1- and VP2-specific MAbs have the capacity to neutralize 50% of infectious parvovirus B19 in vitro at 0.08 and 0.73 microgram/ml, respectively, demonstrating the importance of such antibodies in the clearance of B19 viremia. The NS1-specific MAb mediated weak neutralizing activity and required 47.7 micrograms/ml for 50% neutralization. The human MAbs with potent neutralizing activity could be used for immunotherapy of chronically B19 virus-infected individuals and acutely infected pregnant women. Furthermore, the knowledge gained regarding epitopes which induce strongly neutralizing antibodies may be important for vaccine development.     

Fibronectin of human liver sinusoids binds hepatitis B virus: identification by an anti-idiotypic antibody bearing the internal image of the pre-S2 domain

Anti-idiotypic antibodies (anti-Ids) have been successfully used to characterize and isolate receptors of several cell ligands. To prepare an immunological probe for identification of cellular components interacting with the hepatitis B virus (HBV), polyclonal antisera against a panel of five HBV-specific monoclonal antibodies (MAbs) were produced in syngeneic BALB/c mice. MAbs to HBV used for immunization (Ab1) recognized biologically important and potentially neutralizing epitopes, located in the pre-S1, pre-S2, or S region-encoded domains of HBV proteins. All the anti-Ids (Ab2) were specific to idiotopes of the homologous Ab1 and inhibited their interaction with the corresponding viral epitopes, suggesting that they recognized unique determinants on the paratope of each immunizing Ab1. Therefore, all five generated polyclonal anti-Ids were of the Ab2 beta type and could represent internal images of viral epitopes. Ab2 raised against the pre-S2 region-specific MAb F124 bound to the extracellular matrix fibronectin of human liver sinusoids. Immunohistochemical studies demonstrated the attachment of viral and recombinant (S, M) hepatitis B surface antigen particles with the pre-S2 region-encoded epitopes to the fibronectin of human liver sinusoids. In contrast, recombinant (S, L*) hepatitis B surface antigen particles, in which the epitope recognized by F124 MAb was not expressed, did not show any binding capacity. These findings suggest that human liver fibronectin may bind HBV in vivo by the pre-S2 region-encoded epitopes in a species-restricted manner. Furthermore, binding of the circulating virus to liver sinusoids could facilitate its subsequent uptake by hepatocytes.     

Synergistic neutralization of a chimeric SIV/HIV type 1 virus with combinations of human anti-HIV type 1 envelope monoclonal antibodies or hyperimmune globulins

A panel of 14 human IgG monoclonal antibodies (MAbs) specific for envelope antigens of the human immunodeficiency virus type 1 (HIV-1), 2 high-titer human anti-HIV-1 immunoglobulin (HIVIG) preparations, and 15 combinations of MAbs or MAb/HIVIG were tested for their ability to neutralize infection of cultured human T cells (MT-2) with a chimeric simian immunodeficiency virus (SHIV-vpu+), which expressed HIV-1 IIIB envelope antigens. Eleven MAbs and both HIVIGs were neutralizing. When used alone, the anti-CD4-binding site MAb b12, the anti-gp41 MAb 2F5, and the anti-gp120 MAb 2G12 were the most potent. When combination regimens involving two MAbs targeting different epitopes were tested, synergy was seen in all paired MAbs, except for one combination that revealed additive effects. The lowest effective antibody concentration for 50% viral neutralization (EC50) and EC90 were achieved with combinations of MAbs b12, 2F5, 2G12, and the anti-V3 MAb 694/98D. Depending on the combination regimen, the concentration of MAbs required to reach 90% virus neutralization was reduced approximately 2- to 25-fold as compared to the dose requirement of individual MAbs to produce the same effect. Synergy of the combination regimens implies that combinations of antibodies may have a role in passive immunoprophylaxis against HIV-1. The ability of SHIV to replicate in rhesus macaques will allow us to test such approaches in vivo.     

Involvement of CD44 in matrix metalloproteinase-2 regulation in human melanoma cells

CD44 is a family of cell-surface-adhesion proteins that are thought to play an important role in cancer invasion and metastasis. However, the specific mechanisms by which CD44 expression modulates invasion or metastasis are not well understood. In the current study, we have demonstrated that treatment of human melanoma cells with a CD44 MAb, F10-44-2, induces up-regulation of matrix metalloproteinase-2 (MMP-2) protein and mRNA. Moreover, treatment of melanoma cells with MAb F10-44-2 enhances their migration through gelatin-coated membranes and invasion through reconstituted basement membranes. Treatment of melanoma cells with several known CD44 ligands, including hyaluronate, extracellular-matrix proteins, and osteopontin, did not induce MMP-2 production. CD44 binding by F10-44-2 MAb results in induction of MMP-2 expression, which is associated with enhanced cell migration and invasion. These findings have several implications for investigations into tumor metastasis, development, and lymphocyte function.     

Activation of complement by mannose-binding lectin on isogenic mutants of Neisseria meningitidis serogroup B

Mannose-binding lectin (MBL) is a serum protein that has been demonstrated to activate the classical complement pathway and to function directly as an opsonin. Although MBL deficiency is associated with a common opsonic defect and a predisposition to infection, the role of the protein in bacterial infection remains unclear. We have investigated MBL binding to Neisseria meningitidis serogroup B1940 and three isogenic mutants, and the subsequent activation of the two major isoforms of C4 (C4A and C4B) by an associated serine protease, MASP. The mutants lacked expression of the capsular polysaccharide (siaD-), the lipo-oligosaccharide (LOS) outer core that prevented LOS sialylation (cpsD-), or both capsule and LOS outer core (cps-). Using flow cytometry, it was possible to detect strong MBL binding to the cps- and cpsD- mutants over a wide range of concentrations. In contrast, minimal or no MBL binding was detected on the parent organism, with binding to siaD- only at higher MBL concentrations. C4 was activated and bound by mutants that had previously bound MBL/MASP, but there was no significant difference in the amounts of C4A and C4B bound. When sialic acid residues were removed from the parent organism by neuraminidase treatment, the binding of both MBL and C4 increased significantly. Our results suggest that MBL may bind to and activate complement on these encapsulated organisms, and the major determinants of these effects are the LOS structure and sialylation.     

Neutrophil recruitment by human IL-17 via C-X-C chemokine release in the airways

IL-17 is a recently discovered cytokine that can be released from activated human CD4+ T lymphocytes. This study assessed the proinflammatory effects of human (h) IL-17 in the airways. In vitro, hIL-17 increased the release of IL-8 in human bronchial epithelial and venous endothelial cells, in a time- and concentration-dependent fashion. This effect of hIL-17 was inhibited by cotreatment with an anti-hIL-17 Ab and was potentiated by hTNF-alpha. In addition, hIL-17 increased the expression of hIL-8 mRNA in bronchial epithelial cells. Conditioned medium from hIL-17-treated bronchial epithelial cells increased human neutrophil migration in vitro. This effect was blocked by an anti-hIL-8 Ab. In vivo, intratracheal instillation of hIL-17 selectively recruited neutrophils into rat airways. This recruitment of neutrophils into the airways was inhibited by an anti-hIL-17 Ab and accompanied by increased levels of rat macrophage inflammatory protein-2 (rMIP-2) in bronchoalveolar lavage (BAL) fluid. The BAL neutrophilia was also blocked by an anti-rMIP-2 Ab. The effect of hIL-17 on the release of hIL-8 and rMIP-2 was also inhibited by glucocorticoids, in vitro and in vivo, respectively. These data demonstrate that hIL-17 can specifically and selectively recruit neutrophils into the airways via the release of C-X-C chemokines from bronchial epithelial cells and suggest a novel mechanism linking the activation of T-lymphocytes to recruitment of neutrophils into the airways.