bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Virulence of a
Streptococcus pneumoniae
Neuraminidase-Deficient Mutant in Nasopharyngeal Colonization and Development of Otitis Media in the Chinchilla Model
Authors: Tong H. H. , Blue L. E. , James M. A. , DeMaria T. F. 
Published: July 2002

ABSTRACT

Considerable evidence has implicated
Streptococcus pneumoniae
neuraminidase in the pathogenesis of otitis media (OM); however, its exact role has not been conclusively established. Recently, an
S. pneumoniae
neuraminidase-deficient mutant, ΔNA1, has been constructed by insertion-duplication mutagenesis of the
nanA
gene of
S. pneumoniae
strain D39. The relative ability of ΔNA1 and the D39 parent strain to colonize the nasopharynx and to induce OM subsequent to intranasal inoculation and to survive in the middle ear cleft after direct challenge of the middle ear were evaluated in the chinchilla model. Nasopharyngeal colonization data indicate a significant difference in the ability of the ΔNA1 mutant to colonize as well as to persist in the nasopharynx. The neuraminidase-deficient mutant was eliminated from the nasopharynx 2 weeks earlier than the D39 parent strain. Both the parent and the mutant exhibited similar virulence levels and kinetics during the first week after direct inoculation of the middle ear. The ΔNA1 neuraminidase-deficient mutant, however, was then completely eliminated from the middle ear by day 10 postchallenge, 11 days before the D39 parent strain. Data from this study indicate that products of the
nanA
gene have an impact on the ability of
S. pneumoniae
to colonize and persist in the nasopharynx as well as the middle ear.
Capsular Polysaccharide Is a Major Complement Resistance Factor in Lipopolysaccharide O Side Chain-Deficient
Klebsiella pneumoniae
Clinical Isolates
Authors: Álvarez Dolores , Merino Susana , Tomás Juan M. , Benedí Vicente J. , Albertí Sebastián 
Published: July 2002

ABSTRACT

We have previously demonstrated the existence of
Klebsiella pneumoniae
clinical isolates deficient in the lipopolysaccharide O side chain, the major factor for resistance to complement-mediated killing in this bacterial species. These isolates are complement resistant, and their mechanisms to resist complement were investigated by selecting transposon-generated complement-sensitive mutants. One mutant with a drastically reduced capacity to grow in nonimmune human serum carried the transposon inserted in an open reading frame of a gene cluster involved in capsule synthesis. This mutant produced less capsule, bound more molecules of the complement component C3, and was more sensitive to complement-mediated and opsonophagocytic killings than was the parent strain. Four additional clinical isolates representing four different K serotypes were studied, and results showed that capsular polysaccharide is a major complement resistance factor in these O side chain-deficient isolates.
Borrelia burgdorferiGene Expression In Vivo and Spirochete Pathogenicity
Authors: Anguita Juan , Samanta Swapna , Revilla Beatriz , Suk Kyoungho , Das Subrata , Barthold Stephen W. , Fikrig Erol 
Published: July 2002

ABSTRACTBorrelia burgdorferispirochetes that do not cause arthritis or carditis were developed and used to investigate Lyme disease pathogenesis. A clonal isolate ofB. burgdorferiN40 (cN40), which induces disease in C3H/HeN (C3H) mice, was repeatedly passaged in vitro to generate nonpathogenic spirochetes. The passage 75 isolate (N40-75) was infectious for C3H mice but did not cause arthritis or carditis, and spirochetes were at low levels or absent in the joints or hearts, respectively. N40-75 could, however, cause disease in severe combined immunodeficient (SCID) mice, suggesting that the response in immunocompetent mice prevented effective spirochete dissemination and the subsequent development of arthritis and carditis. Administration of immune sera at 4 days after spirochete challenge aborted N40-75, but not cN40, infection in SCID mice. AB. burgdorferigenomic expression library was differentially probed with sera from cN40- and N40-75-infected mice, to identify genes that may not be effectively expressed by N40-75 in vivo. N40-75 was defective in the up-regulation of several genes that are preferentially expressed during mammalian infection, includingdbpAB,bba64, and genes that map to the cp32 family of plasmids. These data suggest that adaptation and gene expression may be required forB. burgdorferito effectively colonize the host, evade humoral responses, and cause disease.
Activation of Intercellular Adhesion Molecule 1 Expression byHelicobacter pyloriIs Regulated by NF-κB in Gastric Epithelial Cancer Cells
Authors: Mori Naoki , Wada Akihiro , Hirayama Toshiya , Parks Thomas P. , Stratowa Christian , Yamamoto Naoki 
Published: July 2002

ABSTRACTInteractions between leukocytes and epithelial cells may play a key role inHelicobacter pylori-associated gastric mucosal inflammation. This process is mediated by various cell adhesion molecules. The present study examined the molecular mechanisms leading toH. pylori-induced epithelial cell intercellular adhesion molecule-1 (ICAM-1; also called CD54) expression. Coculture of epithelial cells with cytotoxin-associated gene pathogenicity island-positive (cagPAI+)H. pyloristrains, but not with acagPAI−strain orH. pyloriculture supernatants, resulted in upregulation of steady-state mRNA levels and cell surface expression of ICAM-1. Coculture withH. pyloriinduced an increase in luciferase activity in cells which were transfected with a luciferase reporter gene linked to the 5′-flanking region of the ICAM-1 gene.H. pyloriactivated the ICAM-1 promoter via the NF-κB binding site. An inducible nuclear protein complex bound to the ICAM-1 NF-κB site and was identified as the NF-κB p50–p65 heterodimer.H. pyloriinduced the degradation of IκB-α, a major cytoplasmic inhibitor of NF-κB, and stimulated the expression of IκB-α mRNA. Pretreatment of epithelial cells with pyrrolidine dithiocarbamate, which blocks NF-κB activation, inhibitedH. pylori-induced ICAM-1 expression. THP-1 macrophagic cells, peripheral blood mononuclear cells, and purified neutrophils adhered toH. pylori-infected epithelial cells to a greater extent than to uninfected cells. These results show thatH. pyloridirectly induces expression of ICAM-1 on gastric epithelial cells in an NF-κB-dependent manner that may support leukocyte attachment during inflammation.
Specificity of Human Antibodies Reactive with Pneumococcal C Polysaccharide
Authors: Frasch Carl E. , Concepcion Nelydia F. 
Published: July 2002

ABSTRACTAntibodies reactive with C polysaccharide (PS) were found in healthy adults, pneumococcal patients, and vaccinees. These antibodies were not directed to the phosphocholine determinant of the C PS, as they appear to be in mice, since the human antibodies were inhibitable only with C PS. We found another population of phosphocholine-specific antibodies inhibitable only by phosphocholine and related compounds.
Hydroxamate Siderophores of
Histoplasma capsulatum
Authors: Howard Dexter H. , Rafie Ramin , Tiwari Anupama , Faull Kym F. 
Published: July 2002

ABSTRACT

The zoopathogenic fungus
Histoplasma capsulatum
, like other eukaryotic aerobic microorganisms, requires iron for growth. Under conditions of low iron availability, the fungus secretes hydroxamates that function as siderophores (iron chelators). The experiments to be reported were designed to gather further information on the hydroxamate siderophores of
H. capsulatum
. The fungus was grown in a synthetic medium deferrated with the cationic exchange resin Chelex 100. Siderophores were detected after 4 days of incubation at 37°C in media containing 0.3 to 1.0 μM iron. The secretion was suppressed by 10 μM iron. The hydroxamates were purified by reverse-phase and size-exclusion chromatography. On the basis of ions observed during electrospray mass spectroscopy, five hydroxamate siderophores were tentatively identified: dimerum acid, acetyl dimerum acid, coprogen B, methyl coprogen B, and fusarinine (monomeric). A polyclonal antibody to dimerum acid was generated. This reagent cross-reacted with coprogen B and fusarinine. Thus, the antibody detects hydroxamates in all three families of siderophores excreted by
H. capsulatum
.
Ultrastructural Analysis of Developmental Events in
Chlamydia pneumoniae
-Infected Cells
Authors: Wolf Katerina , Fischer Elizabeth , Hackstadt Ted 
Published: July 2002

ABSTRACT

Chlamydia pneumoniae
is an obligate intracellular parasite with a developmental cycle believed to be common to all members of the genus
Chlamydia
. We present a detailed description based on transmission and scanning electron microscopy of temporal events and inclusion structures throughout the
C. pneumoniae
AR-39 developmental cycle.
Bactericidal Activity of Mammalian Cathelicidin-Derived Peptides
Authors: Travis Sue M. , Anderson Norma N. , Forsyth William R. , Espiritu Cesar , Conway Barbara D. , Greenberg E. P. , McCray Paul B. , Lehrer Robert I. , Welsh Michael J. , Tack Brian F. 
Published: July 2002

ABSTRACT

Endogenous antimicrobial peptides of the cathelicidin family contribute to innate immunity. The emergence of widespread antibiotic resistance in many commonly encountered bacteria requires the search for new bactericidal agents with therapeutic potential. Solid-phase synthesis was employed to prepare linear antimicrobial peptides found in cathelicidins of five mammals: human (FALL39/LL37), rabbit (CAP18), mouse (mCRAMP), rat (rCRAMP), and sheep (SMAP29 and SMAP34). These peptides were tested at ionic strengths of 25 and 175 mM against
Pseudomonas aeruginosa
,
Escherichia coli
,
Staphylococcus aureus
, and methicillin-resistant
Staphylococcus aureus
. Each peptide manifested activity against
P. aeruginosa
irrespective of the NaCl concentration. CAP18 and SMAP29 were the most effective peptides of the group against all test organisms under both low- and high-salt conditions. Select peptides of 15 to 21 residues, modeled on CAP18 (37 residues), retained activity against the gram-negative bacteria and methicillin-sensitive
S. aureus
, although the bactericidal activity was reduced compared to that of the parent peptide. In accordance with the behavior of the parent molecule, the truncated peptides adopted an α-helical structure in the presence of trifluoroethanol or lipopolysaccharide. The relationship between the bactericidal activity and several physiochemical properties of the cathelicidins was examined. The activities of the full-length peptides correlated positively with a predicted gradient of hydrophobicity along the peptide backbone and with net positive charge; they correlated inversely with relative abundance of anionic residues. The salt-resistant, antimicrobial properties of CAP18 and SMAP29 suggest that these peptides or congeneric structures have potential for the treatment of bacterial infections in normal and immunocompromised persons and individuals with cystic fibrosis.
In Situ Production of Gamma Interferon, Interleukin-4, and Tumor Necrosis Factor Alpha mRNA in Human Lung Tuberculous Granulomas
Authors: Fenhalls Gael , Wong Anthony , Bezuidenhout Juanita , van Helden Paul , Bardin Philip , Lukey Pauline T. 
Published: July 2002

ABSTRACTHuman tuberculous granulomas from five adults undergoing surgery for hemoptysis were analyzed by nonradioactive in situ hybridization for tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin-4 (IL-4) gene expression. All of the patients produced TNF-α mRNA. Three patients stained positive for both IFN-γ and IL-4 mRNA; the other two stained positive for IFN-γ but not IL-4 mRNA. Heterogeneity between the granulomas was observed in those patients staining positive for both IFN-γ and IL-4 mRNA; these patients exhibited granulomas having IFN-γ and not IL-4 mRNA as well as granulomas positive for both cytokine mRNAs. There was no evidence of caseation in these granulomas, and the cytokine patterns may represent events in the evolution of the granuloma. However, in those granulomas exhibiting caseous necrosis, very little IFN-γ or IL-4 mRNA was observed, implying that progression of the granuloma is accompanied by a down regulation of T-cell responses. TNF-α mRNA expression was highest in patients with both IFN-γ and IL-4 mRNA. Populations of CD68 positive macrophage-like cells within the granulomas produce mRNA for TNF-α, IFN-γ, and IL-4. This implies that macrophages within the tuberculous granuloma may not be dependent on T-cell cytokines for modulation of their function but may be able to regulate their own activation state and that of the surrounding T cells. These findings have implications on the delivery of immunotherapies to patients with tuberculosis.
Synthesis of Polymerized Melanin byCryptococcus neoformansin Infected Rodents
Authors: Rosas Ángel L. , Nosanchuk Joshua D. , Feldmesser Marta , Cox Gary M. , McDade Henry C. , Casadevall Arturo 
Published: July 2002

ABSTRACTThe ability ofCryptococcus neoformansto synthesize polymerized melanin in vitro has been associated with virulence, but it is unclear whether this fungus synthesizes polymerized melanin during infection. To study this question, we used two approaches: one involved the generation of monoclonal antibodies (MAbs) to melanin for use in immunohistochemical studies ofC. neoformans-infected rodents, and the other sought to isolate fungal melanin from infected tissues. Digestion of in vitro-melanizedC. neoformanscells with proteases, denaturant, and hot concentrated acid yields melanin particles that retain the shape of fungal cells and are therefore called melanin ghosts. BALB/c mice were immunized with melanin ghosts, and two immunoglobulin M MAbs to melanin were generated from the spleen of one mouse. Immunofluorescence analyses of lung and brain tissues of rodents infected with wild-type melanin-producing (Mel+)C. neoformansstrains demonstrated binding of the MAbs to the fungal cell wall. No binding was observed when infections were performed with mutant albino (Mel−)C. neoformansstrains. Particles with striking similarity to melanin ghosts were recovered after digestion of lung and brain tissues from Mel+C. neoformans-infected rodents and were reactive with the MAbs to melanin. No particles were recovered from tissues infected with Mel−C. neoformans. A Mel+C. neoformansstrain grown on lung or brain homogenate agar became lightly pigmented and also yielded particles similar to melanin ghosts upon digestion, providing additional evidence that lung and brain tissues contain substrate forC. neoformansmelanization. These results demonstrate thatC. neoformanssynthesizes polymerized melanin during infection, which has important implications for pathogenesis and antifungal drug development.
Receptor Structure for F1C Fimbriae of Uropathogenic
Escherichia coli
Authors: Khan A. Salam , Kniep Bernhard , Oelschlaeger Tobias A. , Van Die Irma , Korhonen Timo , Hacker Jörg 
Published: July 2002

ABSTRACT

F1C fimbriae are correlated with uropathogenic
Escherichia coli
strains. Although F1C fimbriae mediate binding to kidney tubular cells, their receptor is not known. In this paper, we demonstrate for the first time specific carbohydrate residues as receptor structure for F1C-fimbria-expressing
E. coli
. The binding of the F1C fimbriated recombinant
E. coli
strain HB101(pPIL110-54) and purified F1C fimbriae to reference glycolipids of different carbohydrate compositions was evaluated by using thin-layer chromatography (TLC) overlay and solid-phase binding assays. TLC fimbrial overlay analysis revealed the binding ability of purified F1C fimbriae only to glucosylceramide (GlcCer), β1-linked galactosylceramide 2 (GalCer2) with nonhydroxy fatty acids, lactosylceramide, globotriaosylceramide, paragloboside (nLc
4
Cer), lactotriaosylceramide, gangliotriaosylceramide (asialo-GM
2
[GgO
3
Cer]) and gangliotetraosylceramide (asialo-GM
1
[GgO
4
Cer]). The binding of purified F1C fimbriae as well as F1C fimbriated recombinant
E. coli
strain HB101(pPIL110-54) was optimal to microtiter plates coated with asialo-GM
2
(GgO
3
Cer). The bacterial interaction with asialo-GM
1
(GgO
4
Cer) and asialo-GM
2
(GgO
3
Cer) was strongly inhibited only by disaccharide GalNAcβ1-4Galβ linked to bovine serum albumin. We observed no binding to globotetraosylceramide or Forssman antigen (Gb
5
Cer) glycosphingolipids or to sialic-acid-containing gangliosides. It was demonstrated that the presence of a GalCer or GlcCer residue alone is not sufficient for optimal binding, and additional carbohydrate residues are required for high-affinity adherence. Indeed, the binding efficiency of F1C fimbriated recombinant bacteria increased by 19-fold when disaccharide sequence GalNAcβ1-4Galβ is linked to glucosylceramide as in asialo-GM
2
(GgO
3
Cer). Thus, it is suggested that the disaccharide sequence GalNAcβ1-4Galβ of asialo-GM
2
(GgO
3
Cer) which is positioned internally in asialo-GM
1
(GgO
4
Cer) is the high-affinity binding epitope for the F1C fimbriae of uropathogenic
E. coli
.
Gram-Positive Bacteria Are Potent Inducers of Monocytic Interleukin-12 (IL-12) while Gram-Negative Bacteria Preferentially Stimulate IL-10 Production
Authors: Hessle Christina , Andersson Bengt , Wold Agnes E. 
Published: July 2002

ABSTRACTInterleukin-10 (IL-10) and IL-12 are two cytokines secreted by monocytes/macrophages in response to bacterial products which have largely opposite effects on the immune system. IL-12 activates cytotoxicity and gamma interferon (IFN-γ) secretion by T cells and NK cells, whereas IL-10 inhibits these functions. In the present study, the capacities of gram-positive and gram-negative bacteria to induce IL-10 and IL-12 were compared. Monocytes from blood donors were stimulated with UV-killed bacteria from each of seven gram-positive and seven gram-negative bacterial species representing both aerobic and anaerobic commensals and pathogens. Gram-positive bacteria induced much more IL-12 than did gram-negative bacteria (median, 3,500 versus 120 pg/ml at an optimal dose of 25 bacteria/cell;P< 0.001), whereas gram-negative bacteria preferentially stimulated secretion of IL-10 (650 versus 200 pg/ml;P< 0.001). Gram-positive species also induced stronger major histocompatibility complex class II-restricted IFN-γ production in unfractionated blood mononuclear cells than did gram-negative species (12,000 versus 3,600 pg/ml;P< 0.001). The poor IL-12-inducing capacity of gram-negative bacteria was not remediated by addition of blocking anti-IL-10 antibodies to the cultures. No isolated bacterial component could be identified that mimicked the potent induction of IL-12 by whole gram-positive bacteria, whereas purified LPS induced IL-10. The results suggest that gram-positive bacteria induce a cytokine pattern that promotes Th1 effector functions.
Pseudomonas aeruginosa
Cell-to-Cell Signaling Is Required for Virulence in a Model of Acute Pulmonary Infection
Authors: Pearson James P. , Feldman Matthew , Iglewski Barbara H. , Prince Alice 
Published: July 2002

ABSTRACT

Cell-to-cell signaling controls many virulence genes in
Pseudomonas aeruginosa
. We tested the virulence of
las
and
rhl
quorum-sensing mutants in neonatal mice. A
lasI rhlI
double mutant was nearly avirulent, and the respective single mutant strains were reduced in virulence compared with the wild-type strain. Quorum sensing plays a role in
P. aeruginosa
pneumonia in neonatal mice.
Interleukin-10 Gene Therapy-Mediated Amelioration of Bacterial Pneumonia
Authors: Morrison Daniel F. , Foss Dennis L. , Murtaugh Michael P. 
Published: July 2002

ABSTRACTRespiratory infection byActinobacillus pleuropneumoniaecauses a highly pathogenic necrotizing pleuropneumonia with severe edema, hemorrhage and fever. Acute infection is characterized by expression of inflammatory cytokines, including interleukin-1 (IL-1), IL-6 and IL-8. To determine if high level production of inflammatory cytokines contributed to disease pathogenesis, we investigated if inhibiting macrophage activation with adenovirus type 5-expressed IL-10 (Ad-5/IL-10) reduced the severity of acute disease. Porcine tracheal epithelial cells infected with Ad-5/IL-10 produced bioactive human IL-10. When pigs were intratracheally infected withA. pleuropneumoniae, pigs pretreated with Ad-5/IL-10 showed a significant reduction in the amount of lung damage when compared to adenovirus type 5-expressing β-galactosidase (Ad-5/β-Gal)-treated and untreated pigs. In addition, serum zinc levels were unchanged, the lung weight/body weight ratio (an indicator of vascular leakage) was significantly reduced, and lung pathology scores were reduced. Myeloperoxidase activity in lung lavage fluid samples, an indicator of neutrophil invasion, was decreased to levels similar to that seen in pigs not infected withA. pleuropneumoniae. Reduction in inflammatory cytokine levels in lung lavage fluid samples correlated with the clinical observations in that pigs pretreated with Ad-5/IL-10 showed a corresponding reduction of IL-1 and tumor necrosis factor (TNF) compared with untreated and Ad-5/β-Gal-treated pigs. IL-6 levels were unaffected by pretreatment with Ad-5/IL-10, consistent with observations that IL-6 was not derived from alveolar macrophages. Since inflammatory cytokines are expressed at high levels in acute bacterial pleuropneumonia, these results indicate that macrophage activation, involving overproduction of IL-1 and TNF, is a prime factor in infection-related cases of massive lung injury.
MaternalTrypanosoma cruziInfection Upregulates Capacity of Uninfected Neonate Cells To Produce Pro- and Anti-Inflammatory Cytokines
Authors: Vekemans Johan , Truyens Carine , Torrico Faustino , Solano Marco , Torrico Mary-Cruz , Rodriguez Patricia , Alonso-Vega Cristina , Carlier Yves 
Published: July 2002

ABSTRACTThe possibility of maternal in utero modulation of the innate and/or adaptive immune responses of uninfected newborns fromTrypanosoma cruzi-infected mothers was investigated by studying the capacity of their whole blood cells to produce cytokines in response toT. cruzilysate or lipopolysaccharide-plus-phytohemagglutinin (LPS-PHA) stimulation. Cells of such newborns occasionally released gamma interferon (IFN-γ) and no interleukin-2 (IL-2) and IL-4 upon specific stimulation, while their mothers responded by the production of IFN-γ, IL-2, and IL-4. Infection in mothers was also associated with a hyperactivation of maternal cells and also, strikingly, of cells of their uninfected neonates, since their release of proinflammatory (IL-1β, IL-6, and tumor necrosis factor alpha [TNF-α]) as well as of anti-inflammatory (IL-10 and soluble TNF receptor) cytokines or factors was upregulated in the presence of LPS-PHA and/or parasite lysate. These results show thatT. cruziinfection in mothers induces profound perturbations in the cytokine response of their uninfected neonates. Such maternal influence on neonatal innate immunity might contribute to limit the occurrence and severity of congenital infection.