bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moesin Functions as a Lipopolysaccharide Receptor on Human Monocytes
Authors: Tohme Ziad N. , Amar Salomon , Van Dyke Thomas E. 
Published: December 2019

ABSTRACTBacterial endotoxin (lipopolysaccharide [LPS]), a glycolipid found in the outer membranes of gram-negative bacteria, induces the secretion of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-1 (IL-1), and IL-6 by monocytes/macrophages. The secretion of these biologically active compounds leads to multiple pathological conditions, such as septic shock. There is substantial evidence that chronic exposure to LPS mediates, at least in part, the tissue destruction associated with gram-negative infection. CD14, a 55-kDa protein, has been identified as an LPS receptor. In conjunction with a serum protein, LPS binding protein (LBP), LPS-CD14 interactions mediate many LPS functions in the inflammatory response. However, CD14 lacks a cytoplasmic domain, or any known signal transduction sequence motif, suggesting the existence of another cell surface domain capable of transducing signals. In this paper, we report a second, CD14-independent LPS binding site, which, based on biological activity, appears to be a functional LPS receptor. Cross-linking experiments were performed to identify LPS binding sites. Two molecules were identified: a 55-kDa protein (CD14) and a second, 78-kDa band. Sequencing of the 78-kDa protein by mass spectroscopic analysis revealed 100% homology with moesin (membrane-organizing extension spike protein). Antibody to CD14 induced partial blocking of the LPS response. However, antimoesin monoclonal antibody completely blocked the LPS-induced TNF-α response in human monocytes, without blocking CD14 binding of LPS. Irrelevant isotype controls had no effect. Additional experiments were performed to evaluate the specificity of the antimoesin blocking. Separate experiments evaluated antimoesin effects on monocyte chemotaxis, IL-1 production in response to IL-1 stimulation, and TNF-α secretion in response toStaphylococcus aureusstimulation. Antimoesin blocked only LPS-mediated events. The data suggest that moesin functions as an independent LPS receptor on human monocytes. The role of moesin in transduction of CD14-mediated signals is discussed.
T-Cell Hyporesponsiveness Induced by Activated Macrophages through Nitric Oxide Production in Mice Infected withMycobacterium tuberculosis
Authors: Nabeshima Shigeki , Nomoto Mari , Matsuzaki Goro , Kishihara Kenji , Taniguchi Hatsumi , Yoshida Shin-ichi , Nomoto Kikuo 
Published: December 2019

ABSTRACTIn active tuberculosis, T-cell response toMycobacterium tuberculosisis known to be reduced. In the course ofMycobacterium tuberculosisinfection in mice, we observed that T-cell proliferation in response toM. tuberculosispurified protein derivative (PPD) reached the maximum level on day 7, then declined to the minimal level on day 14, and persisted at a low level through day 28 postinfection. The frequency of PPD-specific CD4 T cells in the spleen on day 28 decreased to one-sixth on day 7. To further investigate the mechanism of this T-cell hyporesponsiveness, we next analyzed the suppressive activity of spleen macrophages on T-cell function. The nonspecific proliferative response of naive T cells and the PPD-specific proliferative response of T cells were suppressed by day 28 macrophages, but not by day 7 macrophages or naive macrophages. This reduction of proliferative response was restored by addition of nitric oxide synthesis inhibitor, NG-monoethyl-l-arginine monoacetate, but not by monoclonal antibody against interleukin 10 or transforming growth factor β. These data indicate that the macrophages from mice chronically infected withM. tuberculosissuppress T-cell response through production of nitric oxide, suggesting that nitric oxide-induced elimination mediated by activated macrophages may reduce the T-cell response and the number of mycobacterium-specific CD4 T cells in vivo.
Purification, Characterization, and Sequence Analysis of a Potential Virulence Factor from
Porphyromonas gingivalis
, Peptidylarginine Deiminase
Authors: McGraw Walker T. , Potempa Jan , Farley David , Travis James 
Published: December 2019

ABSTRACT

The initiation and progression of adult-onset periodontitis has been associated with infection of the gingival sulcus by
Porphyromonas gingivalis
. This organism utilizes a multitude of virulence factors to evade host defenses as it establishes itself as one of the predominant pathogens in periodontal pockets. A feature common to many other oral pathogens is the production of ammonia due to its protective effect during acidic cleansing cycles in the mouth. Additionally, ammonia production by
P. gingivalis
has been proposed as a virulence factor due to its negative effects on neutrophil function. In this study, we describe the first purification of a peptidylarginine deiminase (PAD) from a prokaryote. PAD exhibits biochemical characteristics and properties that suggest that it may be a virulence agent. PAD deiminates the guanidino group of carboxyl-terminal arginine residues on a variety of peptides, including the vasoregulatory peptide-hormone bradykinin, to yield ammonia and a citrulline residue. The soluble protein has an apparent mass of 46 kDa, while the DNA sequence predicts a full-length protein of 61.7 kDa. PAD is optimally active at 55°C, stable at low pH, and shows the greatest activity above pH 9.0. Interestingly, in the presence of stabilizing factors, PAD is resistant to limited proteolysis and retains significant activity after short-term boiling. We propose that PAD, acting in concert with arginine-specific proteinases from
P. gingivalis
, promotes the growth of the pathogen in the periodontal pocket, initially by enhancing its survivability and then by assisting the organism in its circumvention of host humoral defenses.
Comparative Analysis and Immunological Characterization of theBorreliaBdr Protein Family
Authors: Zückert Wolfram R. , Meyer Jürg , Barbour Alan G. 
Published: December 2019

ABSTRACTMultiple circular and linear plasmids of Lyme disease and relapsing feverBorreliaspirochetes carry genes for members of the Bdr (Borreliadirect repeat) protein family. To define their common and divergent attributes, we first comprehensively compared the known homologs. Bdr proteins with predicted sizes ranging from 10.7 to 30.6 kDa formed five homology groups, based on variable numbers of short direct repeats in a central domain and diverse N- and C-terminal domains. In a further characterization, Western blots were probed with rabbit antisera raised against either of two purified recombinant Bdr proteins fromBorrelia burgdorferiB31. The results showed that antibodies cross-react and several Bdr paralogs 19.5 to 30.5 kDa in size are expressed by cultured strain B31 in a temperature-independent manner. In situ proteolysis, immunofluorescence, and growth inhibition assays indicated that Bdr proteins are not surface exposed. Distinct patterns of cross-reacting proteins of 17.5 to 33 kDa were also detected in otherB. burgdorferi,Borrelia garinii, andBorrelia afzeliistrains as well as in relapsing fever spirochetesBorrelia hermsiiandBorrelia turicatae. Last, we examined whether these proteins are antibody targets during Lyme disease. Analysis of 47 Lyme disease patient sera by immunoblotting and enzyme-linked immunosorbent assays showed that 24 (51%) and 20 (43%), respectively, had detectable antibodies to one or more of the Bdr proteins. Together, these data indicate that Bdr proteins constitute a family of cross-reactiveBorreliaproteins which are expressed in the course of Lyme disease and in vitro.
Role of Hemolysin BL in the Pathogenesis of Extraintestinal
Bacillus cereus
Infection Assessed in an Endophthalmitis Model
Authors: Callegan Michelle C. , Jett Bradley D. , Hancock Lynn E. , Gilmore Michael S. 
Published: December 2019

ABSTRACT

Bacillus cereus
is a rare cause of serious human infection but, paradoxically, causes one of the most severe posttraumatic or endogenous infections of the eye, endophthalmitis, which frequently results in blindness. The virulence of
B. cereus
endophthalmitis historically has been attributed to toxin production. We therefore sought to examine the contribution of the dermonecrotic toxin, hemolysin BL, to the pathogenesis of
B. cereus
infection in an endophthalmitis system that is highly amenable to study. The pathogenesis of infection resulting from intravitreal injection of 10
2
CFU of either a clinical ocular isolate of
B. cereus
producing hemolysin BL (HBL
+
) or an isogenic mutant in this trait (HBL
−
) was assessed bacteriologically and by slit lamp biomicroscopy, electroretinography, histology, and inflammatory cell enumeration. Both HBL
+
and HBL
−
strains evoked severe intraocular inflammatory responses as early as 12 h postinfection, with complete loss of retinal responsiveness by 12 h. The infections caused by both strains spread of the infection to adjacent tissues by 18 h. No significant differences in intraocular bacterial growth (
P
≥ 0.21) or inflammatory changes (
P
≥ 0.21) were observed in eyes infected with either HBL
+
or HBL
−
strains during the course of infection. The level of retinal responsiveness was greater in HBL
−
infected eyes than in HBL
+
-infected eyes at 6 h only (
P
= 0.01). These results indicate that hemolysin BL makes no essential contribution to the severe and rapid course of infection in the endophthalmitis model.
Genomic Loci of the
Porphyromonas gingivalis
Insertion Element IS
1126
Authors: Dong Hong , Chen Tsute , Dewhirst Floyd E. , Fleischmann Robert D. , Fraser Claire M. , Duncan Margaret J. 
Published: December 2019

ABSTRACT

The
Porphyromonas gingivalis
genome contains multiple copies of insertion element IS
1126
. When chromosomal DNA digests of different strains were probed with IS
1126
, between 25 and 35 hybridizing fragments per genome were detected, depending on the strain. Unrelated strains had very different restriction fragment length polymorphism (RFLP) patterns. When different laboratory copies of a specific strain were examined, the IS
1126
RFLP patterns were very similar but small differences were observed, indicating that element-associated changes had occurred during laboratory passage. Within the next year, genome sequencing, assembly, and annotation for
P. gingivalis
W83 will be completed. Because repetitive elements complicate the assembly of randomly sequenced DNA fragments, we isolated and sequenced the flanking regions of IS
1126
copies in strain W83. We also isolated and sequenced the flanking regions of IS
1126
copies in strain ATCC 33277 in order to compare insertion sites in phylogenetically divergent strains. We identified 37 new sequences flanking IS
1126
from strain ATCC 33277 and 30 from strain W83. The insertion element was found between genes except where it transposed into another insertion element. Examination of identifiable flanking genes or open reading frames indicated that the insertion sites were different in the two strains, except that both strains possess an insertion adjacent to the Lys-gingipain gene (J. P. Lewis and F. L. Macrina, Infect. Immun. 66:3035–3042, 1998). Most of the genes or sequences flanking IS
1126
in ATCC 33277 were present in W83 but were contiguous and not insertion element associated. Thus, where genes were identified in both strains, their order was maintained, indicating that the two genomes are organized similarly, but the loci of IS
1126
are different. In both strains, insertion element-associated duplicated target sites were lost from several copies of IS
1126
, providing evidence of homologous recombination between elements. Larger organizational differences between the genomes, such as deletions and inversions, may result from insertion element-mediated recombination events.
Identification and Characterization of TspA, a Major CD4+T-Cell- and B-Cell-StimulatingNeisseria-Specific Antigen
Authors: Kizil Goksel , Todd Ian , Atta Mustafa , Borriello S. Peter , Ait-Tahar Kamel , Ala’Aldeen Dlawer A. A. 
Published: December 2019

ABSTRACTIn search for novel T-cell immunogens involved in protection against invasive meningococcal disease, we screened fractionated proteins ofNeisseria meningitidis(strain SD, B:15:P1.16) by using peripheral blood mononuclear cells (PBMCs) and specific T-cell lines obtained from normal individuals and patients convalescing fromN. meningitidisinfection. Proteins of iron-depleted meningococci produced higher PBMC proliferation indices than proteins of iron-replete organisms, indicating that iron-regulated proteins are T-cell immunogens. Insoluble proteins of the iron-depleted cells, which produced better T-cell stimulation than soluble ones, were fractionated by using sodium dodecyl sulfate-polyacrylamide gels and recovered as five fractions (F1 to F5) corresponding to decreasing molecular weight ranges. The proteins were purified (by elution and precipitation) or electroblotted onto nitrocellulose membranes (dissolved and precipitated) before use in further T-cell proliferation assays. One of the fractions (F1), containing high-molecular-mass proteins (>130 kDa), consistently showed the strongest T-cell proliferation responses in all of the T-cell lines examined. F1 proteins were subdivided into four smaller fractions (F1A to F1D) which were reexamined in T-cell proliferation assays, and F1C induced the strongest responses in patients’ T-cell lines. Rabbit polyclonal antibodies to F1C components were used to screen a genomic expression library ofN. meningitidis. Two major clones (C1 and C24) of recombinant meningococcal DNA were identified and fully sequenced. Sequence analysis showed that C24 (1,874 bp) consisted of a single open reading frame (ORF), which was included in clone C1 (2,778 bp). The strong CD4+T-cell-stimulating effect of the polypeptide product of this ORF (named TspA) was confirmed, using a patient T-cell line. Immunogenicity for B cells was confirmed by showing that convalescent patients’ serum antibodies recognized TspA on Western blots. Additional genetic sequence downstream of C24 was obtained from the meningococcal genomic sequence database (Sanger Centre), enabling the whole gene of 2,761 bp to be reconstructed. The DNA and deduced amino acid sequence data fortspAfailed to show significant homology to any known gene, except for a corresponding (uncharacterized) gene inNeisseria gonorrhoeaegenome sequences, suggesting thattspAis unique to the genusNeisseria. The DNA and deduced amino acid sequence of the second ORF of clone C1 showed significant homology togloA, encoding glyoxalase I enzyme, ofSalmonella typhimuriumandEscherichia coli. Thus, we have identified a novel neisserial protein (TspA) which proved to be a strong CD4+T-cell- and B-cell-stimulating immunogen with potential as a possible vaccine candidate.
Role of CD40 Ligand inMycobacterium aviumInfection
Authors: Hayashi Tomoko , Rao Savita P. , Meylan Pascal R. , Kornbluth Richard S. , Catanzaro Antonino 
Published: December 2019

ABSTRACTMycobacterium aviumis a common opportunistic pathogen in immunocompromised patients such as those infected with human immunodeficiency virus. AlthoughM. aviumis an intracellular organism replicating predominantly in macrophages, disseminatedM. aviuminfection is seen in AIDS patients with CD4+cell counts of <50 cells/μl, suggesting a possible involvement of a T cell-macrophage interaction for the elimination ofM. avium. To determine whether CD40-CD40 ligand (CD40L) interactions play a role inM. aviuminfection, we studied the ability of CD40L to restrictM. aviumreplication in human monocyte-derived macrophages (MDM) in vitro. MDM were infected withM. aviumand cocultured with CD40L-transfected 293 cells for 7 days. Intracellular growth ofM. aviumin these MDM was assessed by colony counting. CD40L-expressing cells inhibited growth ofM. aviumin MDM by 86.5% ± 4.2% compared to MDM cultured with control cells. These findings were verified by assays using purified, soluble recombinant human CD40L (CD40LT). CD40LT (5 μg/ml) inhibited intracellular growth ofM. aviumby 76.9% ± 18.0% compared to cells treated with medium alone. Inhibition by CD40LT was reduced by monoclonal antibodies (MAbs) against CD40 and CD40L. The inhibitory effect of CD40LT was not accompanied by enhancement of interleukin-12 (IL-12) production byM. avium-infected MDM, while CD40L-expressing cells stimulated IL-12 production by these cells. Treatment ofM. avium-infected mice with MAb against murine CD40L resulted in recovery of larger numbers of organisms (0.8 to 1.0 log) from the spleens, livers, and lungs of these animals compared to infected mice which received normal immunoglobulin G. These results indicate that CD40-CD40L signaling may be an important step in host immune response againstM. aviuminfection.
Differential Regulation of Immune Responses by Highly and Weakly VirulentCryptococcus neoformansIsolates
Authors: Blackstock Rebecca , Buchanan Kent L. , Adesina Adekunle M. , Murphy J. W. 
Published: December 2019

ABSTRACTEarly inflammatory responses, delayed-type hypersensitivity (DTH) responses, and cytokine profiles were studied in mice infected by the pulmonary route with either a highly virulent isolate (NU-2) or a weakly virulent isolate (184A) ofCryptococcus neoformans. After infection, NU-2 remained in the lungs and the capsule became more pronounced during the first 24 h, whereas 184A induced an immediate inflammatory reaction and was rapidly cleared from the lungs. Cryptococcal antigen (GXM) appeared in sera early after infection with NU-2 and increased over the entire observation period. There was no detectable GXM in sera from 184A-infected mice. BothC. neoformansisolates induced anticryptococcal cell-mediated immune responses, but the responses had different profiles. DTH in NU-2-infected mice appeared at day 15 after infection and waned by day 21, whereas DTH in 184A-infected mice was present by day 5 and continued to increase. T helper 1 (Th1) cytokines (interleukin 2 [IL-2] and gamma interferon) were made by spleen cells early after infection with either isolate. NU-2-infected mice lost their ability to produce these cytokines, but 184A-infected mice retained it. IL-4, a Th2 cytokine, was not detected in infected mice. The regulatory cytokine IL-10 was made by spleen cells early but not later after infection with the highly virulent isolate and was not produced by spleen cells from 184A-infected mice. IL-10-deficient mice survived an NU-2 infection significantly longer than wild-type mice, suggesting that IL-10 is important in down-regulating the protective immune response. The induction of anergy appears to be responsible for the inability of NU-2-infected mice to control aC. neoformansinfection.
Salmonella typhiFlagella Are Potent Inducers of Proinflammatory Cytokine Secretion by Human Monocytes
Authors: Wyant Timothy L. , Tanner Michael K. , Sztein Marcelo B. 
Published: December 2019

ABSTRACTThe cytokine production patterns of human peripheral blood mononuclear cells (PBMC) in response toSalmonella typhiflagella (STF) were examined in culture supernatants of PBMC stimulated with STF. Consistent with previous findings in volunteers vaccinated witharoC aroDdeletion mutants ofS. typhi, PBMC from volunteers immunized with the licensed live Ty21aS. typhivaccine secreted gamma interferon following exposure to STF. Stimulation with STF induced rapid de novo synthesis of tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β), followed by IL-6 and IL-10. Trypsin treatment of STF abrogated their effects, while polymyxin B had no effect. Intracellular cytokine measurements of STF-stimulated PBMC revealed the existence of monocyte subpopulations that produce only TNF-α, IL-1β or both cytokines. Moreover, STF markedly decreased the percentage of CD14+cells. These data demonstrate that STF are powerful monocyte activators which may have important implications for vaccine development and for understanding the pathogenesis ofS. typhiinfection.
Pseudomonas aeruginosa
Gene Products PilT and PilU Are Required for Cytotoxicity In Vitro and Virulence in a Mouse Model of Acute Pneumonia
Authors: Comolli James C. , Hauser Alan R. , Waite Leslie , Whitchurch Cynthia B. , Mattick John S. , Engel Joanne N. 
Published: December 2019

ABSTRACT

Type IV pili of the opportunistic pathogen
Pseudomonas aeruginosa
mediate twitching motility and act as receptors for bacteriophage infection. They are also important bacterial adhesins, and nonpiliated mutants of
P. aeruginosa
have been shown to cause less epithelial cell damage in vitro and have decreased virulence in animal models. This finding raises the question as to whether the reduction in cytotoxicity and virulence of nonpiliated
P. aeruginosa
mutants are primarily due to defects in cell adhesion or loss of twitching motility, or both. This work describes the role of PilT and PilU, putative nucleotide-binding proteins involved in pili function, in mediating epithelial cell injury in vitro and virulence in vivo. Mutants of
pilT
and
pilU
retain surface pili but have lost twitching motility. In three different epithelial cell lines,
pilT
or
pilU
mutants of the strain PAK caused less cytotoxicity than the wild-type strain but more than isogenic, nonpiliated
pilA
or
rpoN
mutants. The
pilT
and
pilU
mutants also showed reduced association with these same epithelial cell lines compared both to the wild type, and surprisingly, to a
pilA
mutant. In a mouse model of acute pneumonia, the
pilT
and
pilU
mutants showed decreased colonization of the liver but not of the lung relative to the parental strain, though they exhibited no change in the ability to cause mortality. These results demonstrate that pilus function mediated by PilT and PilU is required for in vitro adherence and cytotoxicity toward epithelial cells and is important in virulence in vivo.
The Nature of the Attenuation ofSalmonella typhimuriumStrains Expressing Human Papillomavirus Type 16 Virus-Like Particles Determines the Systemic and Mucosal Antibody Responses in Nasally Immunized Mice
Authors: Benyacoub Jalil , Hopkins Sally , Potts Alexandra , Kelly Sandra , Kraehenbuhl Jean-Pierre , Curtiss Roy , De Grandi Pierre , Nardelli-Haefliger Denise 
Published: December 2019

ABSTRACTWe have recently shown by using a recombinantSalmonella typhimuriumPhoPcstrain in mice the feasibility of using aSalmonella-based vaccine to prevent infection by the genital human papillomavirus type 16 (HPV16). Here, we compare the HPV16-specific antibody responses elicited by nasal immunization with recombinantS. typhimuriumstrains harboring attenuations that, in contrast to PhoPc, are suitable for human use. For this purpose, χ4989 (Δcya Δcrp) and χ4990 [ΔcyaΔ(crp-cdt)] were constructed in the ATCC 14028 genetic background, and comparison was made with the isogenic PhoPcand PhoP−strains. Although the levels of expression of HPV16 virus-like particle (VLP) were similar in all strains, only PhoPcHPV16 induced sustained specific antibody responses after nasal immunization, while all strains induced high antibody responses with a single nasal immunization when an unrelated viral hepatitis B core antigen was expressed. The level of the specific antibody responses induced did not correlate with the number of recombinant bacteria surviving in various organs 2 weeks after immunization. Our data suggest that the immunogenicity of attenuatedSalmonellavaccine strains does not correlate with either the number of persisting bacteria after immunization or the levels of in vitro expression of the antigen carried. Rather, the PhoPcphenotype appears to provide the unique ability inSalmonellato induce immune responses against HPV16 VLPs.