bluuebunny/crossref_metadata_2025_split huggingface dataset:
Counteracting Interactions between Lipopolysaccharide Molecules with Differential Activation of Toll-Like Receptors
Authors: Hajishengallis George , Martin Michael , Schifferle Robert E. , Genco Robert J. 
Published: November 2002

ABSTRACTWe investigated counteracting interactions between the lipopolysaccharides (LPS) fromEscherichia coli(Ec-LPS) andPorphyromonas gingivalis(Pg-LPS), which induce cellular activation through Toll-like receptor 4 (TLR4) and TLR2, respectively. We found that Ec-LPS induced tolerance in THP-1 cells to subsequent tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) induction by Pg-LPS, though the reverse was not true, and looked for explanatory differential effects on the signal transduction pathway. Cells exposed to Pg-LPS, but not to Ec-LPS, displayed persisting expression of IL-1 receptor-associated kinase without apparent degradation, presumably allowing prolonged relay of downstream signals. Accordingly, cells pretreated with Pg-LPS, but not with Ec-LPS, were effectively activated in response to subsequent exposure to either LPS molecule, as evidenced by assessing nuclear factor (NF)-κB activity. In fact, Pg-LPS primed THP-1 cells for enhanced NF-κB activation and TNF-α release upon restimulation with the same LPS. This was a dose-dependent effect and correlated with upregulation of surface TLR2 expression. Furthermore, we observed inhibition of NF-κB-dependent transcription in a reporter cell line pretreated with Ec-LPS and restimulated with Pg-LPS (compared to cells pretreated with medium only and restimulated with Pg-LPS), but not when the reverse treatment was made. Although Pg-LPS could not make cells tolerant to subsequent activation by Ec-LPS, Pg-LPS inhibited Ec-LPS-induced TNF-α and IL-6 release when the two molecules were added simultaneously into THP-1 cell cultures. Pg-LPS also suppressedP. gingivalisFimA protein-induced NF-κB-dependent transcription in the 3E10/huTLR4 reporter cell line, which does not express TLR2. This rules out competition for common signaling intermediates, suggesting that Pg-LPS may block component(s) of the TLR4 receptor complex. Interactions between TLR2 and TLR4 agonists may be important in the regulation of inflammatory reactions.
Fibronectin-Facilitated Invasion of T84 Eukaryotic Cells by
Campylobacter jejuni
Occurs Preferentially at the Basolateral Cell Surface
Authors: Monteville Marshall R. , Konkel Michael E. 
Published: November 2002

ABSTRACT

Previous studies have indicated that the ability to bind to fibronectin is a key feature in successful cell invasion by
Campylobacter jejuni
. Given the spatial distribution of fibronectin and the architecture of the epithelium, this suggests the possibility that
C. jejuni
cell invasion might preferentially occur at the basolateral cell surface. To test this hypothesis, we examined the interaction of
C. jejuni
with T84 human colonic cells. When grown under the appropriate conditions, T84 cells form a polarized cell monolayer.
C. jejuni
translocation of a T84 cell monolayer appeared to occur via a paracellular (extracellular) route as opposed to a transcellular (intracellular) route based on the finding that a
C. jejuni
noninvasive mutant translocated as efficiently as its isogenic parent. Additional studies revealed that two distinct
C. jejuni
wild-type isolates could compete with one another for host cell receptors, whereas a
C. jejuni
fibronectin-binding-deficient mutant could not compete with a wild-type isolate for host cell receptors. Further,
C. jejuni
adherence and internalization were significantly inhibited by antifibronectin antibodies but only when cells were first treated with EGTA to expose basolateral cell surfaces. Together, these results support the theory that
C. jejuni
invasion occurs preferentially at the basolateral surface of eukaryotic cells.
Transgenic Mice Expressing Human Interleukin-10 in the Antigen-Presenting Cell Compartment Show Increased Susceptibility to Infection withMycobacterium aviumAssociated with Decreased Macrophage Effector Function and Apoptosis
Authors: Feng Carl G. , Kullberg Marika C. , Jankovic Dragana , Cheever Allen W. , Caspar Patricia , Coffman Robert L. , Sher Alan 
Published: November 2002

ABSTRACTInterleukin-10 (IL-10) is thought to play an important role in the regulation of microbial immunity. While T-cell-derived IL-10 has been shown to suppress cell-mediated immunity, there has been debate as to whether antigen presenting cell (APC)-derived cytokine can perform the same function in vivo. To assess the influence of APC-produced IL-10 on host resistance to mycobacterial infection, transgenic mice expressing human IL-10 under the control of the major histocompatibility complex class II promoter (hu10Tg) were infected withMycobacterium avium, and bacterial burdens and immune responses were compared with those observed in wild-type (wt) animals. Hu10Tg mice harbored substantially higher numbers ofM. aviumand succumbed 16 to 18 weeks postinfection. The granulomas in infected hu10Tg mice showed marked increases in both acid-fast bacilli and host macrophages. In addition, these animals displayed a dramatic increase in hepatic fibrosis. The increased susceptibility of the hu10Tg mice toM. aviuminfection is independent of T-cell-produced endogenous murine IL-10, since bacterial burdens in mice derived by crossing hu10Tg mice with murine IL-10-deficient mice were not significantly different from those in hu10Tg mice. Importantly, gamma interferon (IFN-γ) responses were not decreased in the infected transgenic animals from those in wt animals, suggesting the normal development of Th1 effector cells. In contrast, mycobacterium-induced macrophage apoptosis as well as production of TNF, nitric oxide, and IL-12p40 were strongly inhibited in hu10Tg mice. Together, these data indicate that APC-derived IL-10 can exert a major inhibitory effect on control of mycobacterial infection by a mechanism involving the suppression of macrophage effector function and apoptosis.
Analysis of Ebh, a 1.1-Megadalton Cell Wall-Associated Fibronectin-Binding Protein of
Staphylococcus aureus
Authors: Clarke Simon R. , Harris Llinos G. , Richards R. Geoff , Foster Simon J. 
Published: November 2002

ABSTRACT

In order for
Staphylococcus aureus
to adhere to host extracellular matrix (ECM) substrates, it elicits a wide range of surface proteins. We have characterized a novel ∼1.1-MDa protein in
S. aureus
, termed Ebh (for ECM-binding protein homologue), which has homology to other ECM-binding proteins. Ebh consists of several domains, including a large central region with 44 imperfect repeats of 126 amino acids. Expression analysis revealed
ebh
to be growth phase regulated and repressed by
agr
. A fragment of the central repeat region of Ebh was cloned, overexpressed, and used in ligand-binding studies to determine Ebh function. The recombinant protein was found to specifically bind human fibronectin. Ebh is produced during human infection since serum samples taken from patients with confirmed
S. aureus
infections were found to contain anti-Ebh antibodies. Localization studies revealed Ebh to be cell envelope associated and is proposed to form a specialized surface structure involved in cellular adhesion.
Innate Immune Responses of Human Neonatal Cells to Bacteria from the Normal Gastrointestinal Flora
Authors: Karlsson Helen , Hessle Christina , Rudin Anna 
Published: November 2002

ABSTRACTThe hygiene hypothesis postulates that the prevalence of allergy has increased due to decreased microbial stimulation early in life, leading to delayed maturation of the immune system. The aim of this study was to examine the cytokine pattern produced from cord blood mononuclear cells relative to adult cells after stimulation with bacterial strains from the normal flora. Mononuclear cells from cord and adult blood samples were stimulated with the following bacteria:Bifidobacterium adolescentis,Enterococcus faecalis,Lactobacillus plantarum,Streptococcus mitis,Corynebacterium minutissimum,Clostridium perfringens,Bacteroides vulgatus,Escherichia coli,Pseudomonas aeruginosa,Veillonella parvula, andNeisseria sicca. The levels of interleukin 12 (IL-12), tumor necrosis factor alpha (TNF-α), IL-10, and IL-6 were measured by enzyme-linked immunosorbent assay. The TNF-α production was also analyzed after blocking CD14, Toll-like receptor 2 (TLR-2), and TLR-4 prior to stimulation with bacteria. The levels of IL-12 and TNF-α were similar in cord and adult cells. Gram-positive bacteria induced considerably higher levels of IL-12 and TNF-α than gram-negative bacteria in both cord and adult cells. The levels of IL-6 were significantly higher in newborns than in adults, whereas the levels of IL-10 were similar in newborns and adults. Gram-negative and gram-positive bacteria induced similar levels of IL-6 and IL-10 in cord cells.L. plantarumbound or signaled through CD14, TLR-2, and TLR-4, whereasE. coliacted mainly through CD14 and TLR-4. These results indicate that the innate immune response in newborns to commensal bacteria is strong and also suggest that different bacterial strains may have differential effects on the maturation of the immune system of infants.
Characterization ofLeishmania donovaniAntigens Encapsulated in Liposomes That Induce Protective Immunity in BALB/c Mice
Authors: Afrin Farhat , Rajesh Ravindran , Anam Khairul , Gopinath Meenakshisundram , Pal Swati , Ali Nahid 
Published: November 2002

ABSTRACTLeishmania donovanipromastigote membrane antigens (LAg) encapsulated in positively charged liposomes have been found to induce very significant levels of protection against experimental visceral leishmaniasis. The protectively immunized animals exhibited profound delayed-type hypersensitivity and antibody responses. The extent of protection induced by the same antigens, however, varied depending on the charge of the vesicles, with maximum induction by positively charged liposomes, followed by neutral liposomes and last negatively charged liposomes. Characterization of LAg and LAg entrapped in liposomes of different charges by Western blot analysis revealed the immunodominance of gp63 in all three vaccine preparations. The strong reactivity of antigens in a restricted antigen profile that included, in addition to gp63, 72-, 52-, 48-, 45-, 39-, and 20-kDa components in neutral and positively charged liposomes contrasted with the reactivity of a greater number of LAg components in negatively charged liposomes. Resistance to visceral leishmaniasis appears to depend on the immunity induced by gp63 and a few select antigens in association with the right liposomes. A striking similarity between the immunogenic profile of partially purified soluble antigens and that of LAg in neutral and positively charged liposomes suggests the potentiality of these antigens in future vaccine studies ofL. donovani.
T-Cell Responses to theMycobacterium tuberculosis-Specific Antigen ESAT-6 in Brazilian Tuberculosis Patients
Authors: Cardoso Fernando L. L. , Antas Paulo R. Z. , Milagres Alexandre S. , Geluk Annemieke , Franken Kees L. M. C. , Oliveira Eliane B. , Teixeira Henrique C. , Nogueira Susie A. , Sarno Euzenir N. , Klatser Paul , Ottenhoff Tom H. M. , Sampaio Elizabeth P. 
Published: November 2002

ABSTRACTTheMycobacterium tuberculosis-specific ESAT-6 antigen induces highly potent T-cell responses and production of gamma interferon (IFN-γ), which play a critical role in protective cell-mediated immunity against tuberculosis (TB). In the present study, IFN-γ secretion by peripheral blood mononuclear cells (PBMCs) in response toM. tuberculosisESAT-6 in Brazilian TB patients was investigated in relation to clinical disease types, such as pleurisy and cavitary pulmonary TB. Leprosy patients, patients with pulmonary diseases other than TB, and healthy donors were assayed as control groups. Sixty percent of the TB patients indeed recognizedM. tuberculosisESAT-6, as did 50% of the leprosy patients and 60% of the non-TB controls. Nevertheless, the levels of IFN-γ in response to the antigen ESAT, but not to antigen 85B (Ag85B) and purified protein derivative (PPD), were significantly lower in controls than in patients with treated TB or pleural or cavitary TB. Moreover, according toMycobacterium bovisBCG vaccination status, only 59% of the vaccinated TB patients responded to ESAT in vitro, whereas 100% of them responded to PPD. Both CD4 and CD8 T cells were able to release IFN-γ in response to ESAT. The present data demonstrate the specificity of ESAT-6 ofM. tuberculosisand its ability to discriminate TB patients from controls, including leprosy patients. However, to obtain specificity, it is necessary to include quantitative IFN-γ production in response to the antigen as well, and this might limit the use of ESAT-6-based immunodiagnosis ofM. tuberculosisinfection in an area of TB endemicity.
Type 1 Immunity Provides Optimal Protection against Both Mucosal and SystemicTrypanosoma cruziChallenges
Authors: Hoft D. F. , Eickhoff C. S. 
Published: November 2002

ABSTRACTChagas' disease results from infection withTrypanosoma cruzi, a protozoan parasite that establishes systemic intracellular infection after mucosal invasion. We hypothesized that ideal vaccines for mucosally invasive, intracellular pathogens likeT. cruzishould induce mucosal type 2 immunity for optimal induction of protective secretory immunoglobulin A (IgA) and systemic type 1 immunity protective against intracellular replication. However, differential mucosal and systemic immune memory could be difficult to induce because of reciprocal inhibitory actions between type 1 and type 2 responses. To test our hypotheses, we investigated the protective effects of type 1 and type 2 biased vaccines against mucosal and systemicT. cruzichallenges. Intranasal vaccinations were given with recombinant interleukin-12 (IL-12)- and IL-4-neutralizing antibody (Ab) for type 1 immune bias, or recombinant IL-4 and gamma interferon-neutralizing Ab for type 2 immune bias. Cytokine RNA and protein studies confirmed that highly polarized memory immune responses were induced by our vaccination protocols. Survival after virulent subcutaneousT. cruzichallenge was used to assess systemic protection. Mucosal protection was assessed by measuring the relative inhibition of parasite replication in mucosal tissues early after oralT. cruzichallenge, using both PCR and quantitative culture techniques. As expected, only type 1 responses protected against systemic challenges (P< 0.01). However, contrary to our original hypothesis, type 1 responses optimally protected against mucosal challenges as well (P< 0.05). Type 1 and type 2 biased vaccines induced similar secretory IgA responses. We conclude that future vaccines forT. cruziand possibly other mucosally invasive, intracellular pathogens should induce both mucosal and systemic type 1 immunity.
Chromosomal DNA Deletions Explain Phenotypic Characteristics of Two Antigenic Variants, Phase II and RSA 514 (Crazy), of theCoxiella burnetiiNine Mile Strain
Authors: Hoover T. A. , Culp D. W. , Vodkin M. H. , Williams J. C. , Thompson H. A. 
Published: November 2002

ABSTRACTAfter repeated passages through embyronated eggs, the Nine Mile strain ofCoxiella burnetiiexhibits antigenic variation, a loss of virulence characteristics, and transition to a truncated lipopolysaccharide (LPS) structure. In two independently derived strains, Nine Mile phase II and RSA 514, these phenotypic changes were accompanied by a large chromosomal deletion (M. H. Vodkin and J. C. Williams, J. Gen. Microbiol.132:2587-2594, 1986). In the work reported here, additional screening of a cosmid bank prepared from the wild-type strain was used to map the deletion termini of both mutant strains and to accumulate all the segments of DNA that comprise the two deletions. The corresponding DNAs were then sequenced and annotated. The Nine Mile phase II deletion was completely nested within the deletion of the RSA 514 strain. Basic alignment and homology studies indicated that a large group of LPS biosynthetic genes, arranged in an apparent O-antigen cluster, was deleted in both variants. Database homologies identified, in particular, mannose pathway genes and genes encoding sugar methylases and nucleotide sugar epimerase-dehydratase proteins. Candidate genes for addition of sugar units to the core oligosaccharide for synthesis of the rare sugar 6-deoxy-3-C-methylgulose (virenose) were identified in the deleted region. Repeats, redundancies, paralogous genes, and two regions with reduced G+C contents were found within the deletions.
Up-Regulation of Th1-Type Responses in Mucosal Leishmaniasis Patients
Authors: Bacellar Olívia , Lessa Hélio , Schriefer Albert , Machado Paulo , Ribeiro de Jesus Amélia , Dutra Walderez O. , Gollob Kenneth J. , Carvalho Edgar M. 
Published: November 2002

ABSTRACTThe cytokine profile produced by peripheral blood mononuclear cells (PBMC) in response to leishmania antigens and the ability of interleukin-10 (IL-10) and transforming growth factor β (TGF-β) to modulate the immune response were evaluated in 21 mucosal leishmaniasis patients. Patients with mucosal disease exhibited increased gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) secretion and decreased IL-10 secretion compared to patients with classical cutaneous leishmaniasis. CD4+Th1 cells were the main source of IFN-γ and TNF-α production in mucosal leishmaniasis patients. Evaluation of cytokine gene expression in PBMC of these patients showed that there was strong up-regulation of IFN-γ transcripts upon stimulation with leishmania antigen, in contrast to the baseline levels of IL-10 mRNA. IL-10 suppressed IFN-γ production by 48% in cell cultures from cutaneous leishmaniasis patients and by 86% in cell cultures from healthy subjects stimulated with purified protein derivative, whereas in similar conditions IL-10 suppressed IFN-γ production by 19% in cell cultures from mucosal leishmaniasis patients stimulated with leishmania antigen. TGF-β suppressed IFN-γ levels to a greater extent in healthy subjects than in mucosal leishmaniasis and cutaneous leishmaniasis patients. These data indicate that a poorly modulated T-cell response in mucosal leishmaniasis patients leads to production of high levels of proinflammatory cytokines, such as IFN-γ and TNF-α, as well as a decreased ability of IL-10 and TGF-β to modulate this response. These abnormalities may be the basis for the pathological findings observed in this disease.
Cloning and Porin Activity of the Major Outer Membrane Protein P1 from
Coxiella burnetii
Authors: Varghees Sunita , Kiss Kati , Frans Giovanni , Braha Orit , Samuel James E. 
Published: November 2002

ABSTRACT

Coxiella burnetii
, the etiological agent of Q fever, is a gram-negative obligate intracellular bacterium. Two striking characteristics of this microorganism are its ability to thrive within a phagolysosome and its ability to persist in the environment outside a host cell. These abilities have been attributed to the existence of
C. burnetii
developmental cycle variants: large-cell variants (LCV), small-cell variants (SCV), and small dense cells (SDC). Variants differ in protein profiles, including differential expression of a major outer membrane protein (MOMP) of
C. burnetii
, designated P1. The ∼29-kDa MOMP is highly expressed in LCV, down-regulated in SCV, and not apparent in SDC. We sought to characterize P1 through purification of native protein for N-terminal analysis, cloning, and functional studies. Highly purified P1, extracted from
C. burnetii
membranes by using the zwitterionic detergent Empigen, allowed the determination of N-terminal and internal peptide sequences. The entire P1 coding locus was cloned by PCR amplification based upon these peptide sequences, followed by inverse PCR. Comparison of the predicted P1 amino acid sequences among the
C. burnetii
isolates Nine Mile, Koka, Scurry, and Kerns indicated a high degree of conservation. Structural prediction suggests that the peptide has a predominantly β-sheet conformation, consistent with bacterial porins. Typical porin characteristics were observed for native P1, including detergent solubilization properties, heat modification of purified protein, and channel formation in a planar lipid bilayer. Characterization of differentially expressed P1 as a porin increases our understanding of the function of morphological variants and their role in pathogenesis.
Decreased Infectivity despite Unaltered C3 Binding by a ΔhbhAMutant ofMycobacterium tuberculosis
Authors: Mueller-Ortiz Stacey L. , Sepulveda Eliud , Olsen Margaret R. , Jagannath Chinnaswamy , Wanger Audrey R. , Norris Steven J. 
Published: November 2002

ABSTRACTHbhA ofMycobacterium tuberculosisis a multifunctional binding protein, binding to both sulfated sugars such as heparin and to human complement component C3. HbhA may therefore interact with host molecules and/or host cells duringM. tuberculosisinfection and play a role in the pathogenesis of this bacterium. The purpose of this study was to use allelic exchange to create anM. tuberculosisstrain deficient in expression of HbhA to determine whether this protein's C3-binding activity plays a role in the pathogenesis ofM. tuberculosis. An in-frame, 576-bp unmarked deletion in thehbhAgene was created usingsacBas a counterselectable marker. Southern blotting and PCR analyses confirmed deletion ofhbhAin the ΔhbhAmutant. The ΔhbhAmutant strain grew at a rate similar to that of the parent in broth culture and in J774.A1 murine macrophage-like cells but was deficient in growth compared to the parent strain in the lungs, liver, and spleen of infected mice. In addition, the ΔhbhAmutation did not reduce binding ofM. tuberculosisto human C3 or to J774.A1 cells in the presence or absence of serum, suggesting that in the absence of HbhA, other molecules serve as C3-binding molecules on theM. tuberculosissurface. Taken together, these data indicate that HbhA is important in the infectivity ofM. tuberculosis, but its ability to bind C3 is not required for mycobacterial adherence to macrophage-like cells. Using the ΔhbhAmutant strain, a secondM. tuberculosisC3-binding protein similar in size to HbhA was identified as HupB, but the role of HupB as a C3-binding protein in intact organisms remains to be determined.