bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of the Complement Classical Pathway (C1q Binding) by MesophilicAeromonas hydrophilaOuter Membrane Protein
Authors: Merino Susana , Nogueras Maria Mercedes , Aguilar Alicia , Rubires Xavier , Albertí Sebastian , Benedí Vicente Javier , Tomás Juan M. 
Published: December 2019

ABSTRACTThe mechanism of killing ofAeromonas hydrophilaserum-sensitive strains in nonimmune serum by the complement classical pathway has been studied. The bacterial cell surface component that binds C1q more efficiently was identified as a major outer membrane protein of 39 kDa, presumably the porin II described by D. Jeanteur, N. Gletsu, F. Pattus, and J. T. Buckley (Mol. Microbiol. 6:3355–3363, 1992), of these microorganisms. We have demonstrated that the purified form of porin II binds C1q and activates the classical pathway in an antibody-independent manner, with the subsequent consumption of C4 and reduction of the serum total hemolytic activity. Activation of the classical pathway has been observed in human nonimmune serum and agammaglobulinemic serum (both depleted of factor D). Binding of C1q to other components of the bacterial outer membrane, in particular to rough lipopolysaccharide, could not be demonstrated. Activation of the classical pathway by this lipopolysaccharide was also much less efficient than activation by the outer membrane protein. The strains possessing O-antigen lipopolysaccharide bind less C1q than the serum-sensitive strains, because the outer membrane protein is less accessible, and are resistant to complement-mediated killing. Finally, a similar or identical outer membrane protein (presumably porin II) that binds C1q was shown to be present in strains from the most common mesophilicAeromonasO serogroups.
Vector Development for the Expression of Foreign Proteins in the Vaccine StrainBrucella abortusS19
Authors: Comerci Diego J. , Pollevick Guido D. , Vigliocco Ana M. , Frasch Alberto C. C. , Ugalde Rodolfo A. 
Published: December 2019

ABSTRACTA vector for the expression of foreign antigens in the vaccine strainBrucella abortusS19 was developed by using a DNA fragment containing the regulatory sequences and the signal peptide of theBrucella bcsp31gene. This fragment was cloned in broad-host-range plasmid pBBR4MCS, resulting in plasmid pBEV. As a reporter protein, a repetitive antigen ofTrypanosoma cruziwas used. The recombinant fusion protein is stably expressed and secreted into theBrucellaperiplasmic space, inducing a good antibody response against theT. cruziantigen. The expression of the repetitive antigen inBrucellaneither altered its growth pattern nor generated a toxic or lethal effect during experimental infection. The application of this strategy for the generation of live recombinant vaccines and the tagging ofB. abortusS19 vaccine is discussed. This is the first time that a recombinant protein has been expressed in the periplasm of brucellae.
Paromomycin and Geneticin Inhibit Intracellular
Cryptosporidium parvum
without Trafficking through the Host Cell Cytoplasm: Implications for Drug Delivery
Authors: Griffiths Jeffrey K. , Balakrishnan Ramaswamy , Widmer Giovanni , Tzipori Saul 
Published: December 2019

ABSTRACT

Cryptosporidium parvum
, which causes intractable diarrhea and lethal wasting in people with AIDS, occupies an unusual intracellular but extracytoplasmic niche. No reliable therapy for cryptosporidiosis exists, though the aminoglycoside paromomycin is somewhat effective. We report that paromomycin and the related compound geneticin manifest their major in vitro anti-
C. parvum
activity against intracellular parasites via a mechanism that does not require drug trafficking through the host cell cytoplasm. We used both normal and transformed aminoglycoside-resistant Caco-2 or MDBK cells in these studies. Timed-exposure experiments demonstrated that these drugs inhibit intracellular but not extracellular parasites. Apical but not basolateral exposure of infected cells to these drugs led to very significant parasite inhibition, indicating an apical topological restriction of action. We estimated intracytoplasmic concentrations of paromomycin, using an intracellular bacterial killing assay, and found that
C. parvum
infection did not lead to increased paromomycin concentrations compared to those in uninfected cells. Global [
3
H]paromomycin uptake by Caco-2 cells was ∼200-fold higher than the estimated intracytoplasmic paromomycin concentration, suggestive of host cell vesicular uptake and concentration (as has been reported with other cell lines). However, preinfection exposure of Caco-2 cells to paromomycin did not result in subsequent inhibition of parasite development, indicating that if exogenous paromomycin enters the infected host cell vesicular compartment, it does not effectively communicate with the parasite. Thus, the apical membranes overlying the parasite and parasitophorous vacuole may be the unsuspected major route of entry for paromomycin and may be of importance in the design and discovery of novel drug therapies for the otherwise untreatable
C. parvum.
Increased Levels of Intracellular Calcium Are Not Required for the Formation of Attaching and Effacing Lesions by Enteropathogenic and Enterohemorrhagic
Escherichia coli
Authors: Bain Christopher , Keller Rogeria , Collington Georgina K. , Trabulsi Luiz R. , Knutton Stuart 
Published: December 2019

ABSTRACT

Elevated concentrations of intracellular calcium ([Ca]
i
) have been implicated as an important signalling event during attaching and effacing (A/E) lesion formation by enteropathogenic
Escherichia coli
(EPEC). The highly localized nature of the cytoskeletal and cell surface alterations occurring during A/E lesion formation suggests that there should be equally localized EPEC-induced signalling events. To analyze further the calcium responses to infection of HEp-2 cells by EPEC, we employed calcium-imaging fluorescence microscopy, which allows both temporal and spatial measurements of [Ca]
i
in live cells. Using this imaging technique, not only were we unable to detect any significant elevation in [Ca]
i
at sites of A/E EPEC adhesion, but, with several different classical EPEC and enterohemorrhagic
E. coli
(EHEC) strains and three different infection procedures, each of which resulted in extensive A/E bacterial adhesion, we were unable to detect any significant alterations in [Ca]
i
in infected cells compared to uninfected cells. In addition, chelation of intracellular free calcium with bis-(aminophenoxy)-ethane-
N
,
N
,
N
′,
N
′-tetraacetic acid (BAPTA) did not, as previously reported, prevent A/E lesion formation. We conclude that increased [Ca]
i
are not required for A/E lesion formation by EPEC and EHEC.
Role of Streptococcal Pyrogenic Exotoxin B in the Mouse Model of Group A Streptococcal Infection
Authors: Kuo Chih-Feng , Wu Jiunn-Jong , Lin Kuei-Yuan , Tsai Pei-Jane , Lee Shiour-Ching , Jin Ying-Tai , Lei Huan-Yao , Lin Yee-Shin 
Published: December 2019

ABSTRACT

Streptococcal pyrogenic exotoxin B (SPE B) is a cysteine protease produced by
Streptococcus pyogenes
. In this study, the differences in virulence between protease-positive clinical isolates and their protease-negative mutants were examined in a mouse model. Isogenic protease-negative mutants were constructed by homologous recombination, using integrational plasmids to disrupt the
speB
gene. These mutants caused less mortality and tissue damage than protease-positive strains when inoculated into BALB/c mice via air pouch, suggesting that SPE B cysteine protease plays an important role in the pathogenesis of
S. pyogenes
infection. Reconstitution of SPE B in the air pouches increased the mortality of mice receiving the
speB
mutant strain. Infiltrated cell numbers in the exudates from the air pouches of mice infected with SPE B-producing
S. pyogenes
were higher than those from mice infected with protease-negative mutants at 12 h. However, despite pretreatment with vinblastine to deplete neutrophils, injection of protease-positive bacteria still resulted in severe tissue injury, indicating that neutrophil infiltration may not be the major factor involved in SPE B-enhanced tissue damage. The role of SPE B was further confirmed by demonstrating that SPE B immunization of mice conferred protection from challenge with a lethal dose of protease-positive bacteria.
Fab-Independent Antiadhesion Effects of Secretory Immunoglobulin A on S-FimbriatedEscherichia coliAre Mediated by Sialyloligosaccharides
Authors: Schroten Horst , Stapper Christoph , Plogmann Ricarda , Köhler Henrik , Hacker Jörg , Hanisch Franz-Georg 
Published: December 2019

ABSTRACTS-fimbriatedEscherichia colistrains cause sepsis and meningitis in newborns and are known to recognize the carbohydrate sequence sialyl-(α2-3)-galactoside. We show that adhesion of cloned S-fimbriatedE. colito human epithelial cells is inhibited Fab independently by sialyloligosaccharides on secretory immunoglobulin A (s-IgA). This indicates an anti-infective function of s-IgA (Fc), particularly in early human milk.
Immunogenicity of Intranasally Administered Meningococcal Native Outer Membrane Vesicles in Mice
Authors: Saunders Nancy B. , Shoemaker David R. , Brandt Brenda L. , Moran E. Ellen , Larsen Thomas , Zollinger Wendell D. 
Published: December 2019

ABSTRACT

Colonization of the human nasopharyngeal region by
Neisseria meningitidis
is believed to lead to natural immunity. Although the presence of bactericidal antibody in serum has been correlated with immunity to meningococcal disease, mucosal immunity at the portal of entry may also play an important role. This study was undertaken to examine in mice the possibility of safely using native outer membrane vesicles (NOMV) not exposed to detergent as an intranasal (i.n.) vaccine. The mucosal and systemic responses of mice to intranasal and intraperitoneal (i.p.) vaccination with NOMV were compared over a range of doses from 0.1 to 20 μg. Intranasal vaccination of mice with NOMV induced a strong systemic bactericidal antibody response, as well as a strong local immunoglobulin A immune response in the lung as determined by assay of lung lavage fluid by enzyme-linked immunosorbent assay and lung antibody secreting cells by enzyme-linked immunospot assay. However, 8- to 10-fold-higher doses of NOMV were required i.n. compared to i.p. to elicit an equivalent bactericidal antibody response in serum. Some NOMV vaccine was aspirated into the lungs of mice during i.n. immunization and resulted in an acute inflammatory response that peaked at 1 to 2 days postimmunization and was cleared by day 7. These results indicate that i.n. delivery of meningococcal NOMV in mice is highly effective in eliciting the production of both a mucosal immune response and a systemic bactericidal antibody response.
Glucose Stimulates Phagocytosis of UnopsonizedPseudomonas aeruginosaby Cultivated Human Alveolar Macrophages
Authors: Wong Simon Y. C. , Guerdoud Lila M. , Cantin André , Speert David P. 
Published: December 2019

ABSTRACTGlucose has previously been shown to increase the in vitro phagocytosis of unopsonizedPseudomonas aeruginosaby freshly explanted murine peritoneal macrophages (PM) and cultivated alveolar macrophages (AM). This study examined the effect of glucose on the same phagocytosis process in human AM in order to determine whether this phenomenon is conserved among species. Freshly explanted human AM phagocytosed unopsonizedP. aeruginosaat a low level (2 bacteria/macrophage/30 min), whereas mouse AM ingested a negligible number ofP. aeruginosa(0.01 bacterium/macrophage/30 min). Glucose had no effect on this or other phagocytic processes in freshly explanted mouse or human AM. However, following in vitro cultivation for 72 h, human AM phagocytosed three to four times more unopsonizedP. aeruginosathan did freshly explanted cells, but only in the presence of glucose. This glucose-inducible phagocytic response had also been observed in cultivated murine AM. Although similar increases were also detected for the phagocytosis of latex particles and complement-coated sheep erythrocytes by cultivated human AM, these processes were not glucose dependent. The lack of response to glucose in freshly explanted mouse AM was attributed to insufficient glucose transport; however, freshly explanted human AM exhibited significant facilitative glucose transport activity that was inhibitable by cytochalasin B and phloretin. Taken together, these results suggest that the process of glucose-inducible phagocytosis of unopsonizedP. aeruginosais conserved among macrophages from different species, including humans, and that AM, but not PM, required cultivation for this glucose effect to occur. Glucose transport by AM appears to be necessary but not sufficient for phagocytosis of unopsonizedP. aeruginosa.
Identification of an Intestinal Neutral Glycosphingolipid as a Phenotype-Specific Receptor for the K88ad Fimbrial Adhesin ofEscherichia coli
Authors: Grange Philippe A. , Erickson Alan K. , Levery Steven B. , Francis David H. 
Published: December 2019

ABSTRACTIn this study, we identified a receptor for the K88ad fimbrial adhesin ofEscherichia coliin neutral glycosphingolipid preparations from intestinal epithelial cells of K88ad-adhesive pigs, which was absent in preparations from K88ad-nonadhesive pigs. Neither K88ab nor K88ac adhesin variants bound to this neutral glycosphingolipid. Because this receptor is an intestinal glycosphingolipid that binds K88ad adhesin, it has been designated IGLad. Carbohydrate compositional analysis of a partially purified preparation of IGLad identified galactose, glucose, andN-acetylglucosamine in a ratio of 1.5:1.0:0.5 as the major monosaccharides. Preliminary characterization experiments using lectins showed that IGLad contains the terminal glycanic structure Galβ1-4GlcNAc. Removal of terminal β-linked galactose residues from IGLad decreased the recognition of IGLad by the K88ad adhesin, indicating that terminal β-linked galactose is an essential component of the K88ad adhesin recognition site on IGLad. Studies with purified glycosphingolipid standards demonstrated that K88ad adhesin binds to neolactotetraosylceramide (nLc4Cer) (Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-1Cer), lactotriosylceramide (GlcNAcβ1-3Galβ1-4Glcβ1-1Cer) and lactotetraosylceramide (Galβ1-3GlcNAcβ1-3Galβ1-4Glcβ1-1Cer). Based on these studies, IGLad appears to be nLc4Cer.
Fimbria-Mediated Enhanced Attachment of NontypeableHaemophilus influenzaeto Respiratory Syncytial Virus-Infected Respiratory Epithelial Cells
Authors: Jiang Zili , Nagata Nobuo , Molina Edgar , Bakaletz Lauren O. , Hawkins Hal , Patel Janak A. 
Published: December 2019

ABSTRACTRespiratory syncytial virus (RSV) infection is known to predispose children to otitis media and sinusitis due to bacteria such as nontypeableHaemophilus influenzae(NTHI). In this study, we investigated the role of NTHI surface outer membrane protein P5-homologous fimbriae (P5-fimbriae) in attachment to RSV-exposed A549 epithelial cells. Analysis by fluorescence flow cytometry showed that a live P5-fimbriated NTHI strain (NTHIF+) attached to a higher proportion of RSV-exposed A549 cells than to control cells (mean, 68% for RSV versus 29% for control;P= 0.008), while attachment of the P5-fimbriae-deficient isogenic mutant strain (NTHIF−) was significantly lower than in control cells and rose only slightly following RSV exposure (mean, 17% for RSV versus 10% for control,P= 0.229). Attachment of NTHIF+did not correlate with the amount of RSV antigen expressed by A549 cells. Furthermore, paraformaldehyde-fixed NTHIF+also demonstrated an enhanced binding to RSV-exposed cells. Observations by transmission electronic microscopy showed that the mean number of bacteria attached per 100 RSV-exposed A549 cells was higher for NTHIF+than NTHIF−(99 versus 18; P < 0.001). No intracellular bacteria were identified. UV-irradiated conditioned supernatants collected from RSV-infected A549 cultures (UV-cRSV) also enhanced the attachment of NTHIF+to A549, suggesting the presence of a preformed soluble mediator(s) in UV-cRSV that enhances the expression of receptors for P5-fimbriae on A549 cells. In summary, RSV infection significantly enhances NTHI attachment to respiratory epithelial cells. P5-fimbria is the critical appendage of NTHI that participates in this attachment. In clinical settings, blocking of the P5-fimbria-mediated attachment of NTHIF+by passive or active immunity may reduce the morbidity due to NTHI during RSV infection.
Interaction of NK Lysin, a Peptide Produced by Cytolytic Lymphocytes, with Endotoxin
Authors: Andersson M. , Girard R. , Cazenave P.-A. 
Published: December 2019

ABSTRACTNK lysin is a 9-kDa polypeptide that was originally isolated from porcine intestinal tissue based on its antibacterial activity. It is produced by cytolytic lymphocytes and is cytolytic against a number of different types of tumor cells. Here we report the binding of NK lysin to lipopolysaccharide (LPS) and its anti-LPS activity. NK lysin binds to matrix-coated LPS fromEscherichia coli,Pseudomonas aeruginosa, and different strains ofSalmonella enterica. Lipid A and polymyxin B inhibited the binding, demonstrating a preferential interaction of NK lysin with the lipid part of LPS. Chromium-labeled lymphoma cells were lysed by NK lysin, and LPS dose-dependently inhibited the cytolysis at equimolar amounts. In the same manner, NK lysin inhibited certain LPS-stimulated effects on mouse bone marrow cells as well as LPS binding to mouse granulocytes. These results suggest that NK lysin may be a another natural LPS-binding protein from lymphocytes that may participate in the endogenous defense response associated with elevated concentrations of LPS.
Compensation for Decreased Expression of B7 Molecules onLeishmania infantum-Infected Canine Macrophages Results in Restoration of Parasite-Specific T-Cell Proliferation and Gamma Interferon Production
Authors: Pinelli Elena , Rutten Victor P. M. G. , Bruysters Martijn , Moore Peter F. , Ruitenberg E. Joost 
Published: December 2019

ABSTRACTInfection of humans and dogs byLeishmania infantummay result in visceral leishmaniasis, which is characterized by impaired T-cell-mediated immune responses to parasite antigens. Dogs are natural hosts ofLeishmaniaparasites and play an important role in the transmission of the parasites to humans. In an effort to characterize the immune response in dogs infected with this intracellular pathogen, we examined how infection withL. infantumaffects canine macrophages and the consequences for T-cell activation in vitro. We showed that the proliferation of T-cell lines to cognate antigen decreases to background levels when infected autologous monocyte-derived macrophages are used as antigen-presenting cells (APC). The observed reduction of antigen-specific T-cell proliferation was shown to be dependent on the parasite load and to require cell-to-cell interaction of T cells with the infected APC. In addition, we observed a decreased expression of costimulatory B7 molecules on infected monocyte-derived macrophages. The expression of other surface molecules involved in T-cell activation, such as major histocompatibility complex class I and class II, on these cells did not change upon infection, whereas the expression of intracellular adhesion molecule 1 was marginally increased. Compensation for the decreased expression of B7 molecules by the addition of B7-transfected cells resulted in the restoration of cell proliferation and gamma interferon (IFN-γ) production by aLeishmania-specific T-cell line. These results showed that for the activation of parasite-specific canine T cells producing IFN-γ, which are most likely involved in protective immunity, sufficient expression of B7 molecules on infected macrophages is required. Provision of costimulatory molecules may be an approach for immunotherapy of leishmaniaisis as well as for vaccine development.
An Extracellular Protease ofStreptococcus gordoniiHydrolyzes Type IV Collagen and Collagen Analogues
Authors: Juarez Zaira E. , Stinson Murray W. 
Published: December 2019

ABSTRACTStreptococcus gordoniiis a frequent cause of infective bacterial endocarditis, but its mechanisms of virulence are not well defined. In this study, streptococcal proteases were recovered from spent chemically defined medium (CDM) and fractionated by ammonium sulfate precipitation and by ion-exchange and gel filtration column chromatography. Three proteases were distinguished by their different solubilities in ammonium sulfate and their specificities for synthetic peptides. One of the enzymes cleaved collagen analogs Gly-Pro 4-methoxy-β-naphthylamide, 2-furanacryloyl-Leu-Gly-Pro-Ala (FALGPA), andp-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg (pZ-peptide) and was released from the streptococci while complexed to peptidoglycan fragments. Treatment of this protease with mutanolysin reduced its 180- to 200-kDa mass to 98 kDa without loss of enzymatic activity. The purified protease cleaved bovine gelatin, human placental type IV collagen, and the Aα chain of fibrinogen but not albumin, fibronectin, laminin, or myosin. Enzyme activity was inhibited by phenylmethylsulfonyl fluoride, indicating that it is a serine-type protease. Maximum production of the 98-kDa protease occurred during growth ofS. gordoniiCH1 in CDM containing 0.075% total amino acids at pH 7.0 with minimal aeration. Higher initial concentrations of amino acids prevented the release of the protease without reducing cell-associated enzyme levels, and the addition of an amino acid mixture to an actively secreting culture stopped further enzyme release. The purified protease was stored frozen at −20°C for several months or heated at 50°C for 10 min without loss of activity. These data indicate thatS. gordoniiproduces an extracellular gelatinase/type IV collagenase during growth in medium containing minimal concentrations of free amino acids. Thus, the extracellular enzyme is a potential virulence factor in the amino acid-stringent, thrombotic, valvular lesions of bacterial endocarditis.
Vibrio anguillarumResistance to Rainbow Trout (Oncorhynchus mykiss) Serum: Role of O-Antigen Structure of Lipopolysaccharide
Authors: Boesen Henriette T. , Pedersen Karl , Larsen Jens L. , Koch Claus , Ellis Anthony E. 
Published: December 2019

ABSTRACTThe sensitivity ofVibrio anguillarumto the bactericidal effect of rainbow trout serum was investigated with different strains of serogroups O1 and O2a, which are the most frequently found serogroups in clinical outbreaks of vibriosis. All of theV. anguillarumstrains were able to activate complement in rainbow trout serum, but smooth strains ofV. anguillarumserogroup O1 were resistant to complement-mediated killing in the absence of specific antibodies. In the case ofV. anguillarumserogroup O2a strains, 80% of the analyzed strains were resistant to rainbow trout serum even when specific antibodies were present. Analysis of the lipopolysaccharide structures of the testedV. anguillarumstrains showed a positive correlation between the O-antigen size of the lipopolysaccharide and resistance to serum killing. The classical complement pathway was responsible for the antibody-dependent serum killing of susceptibleV. anguillarumstrains. When serum-resistantV. anguillarumserogroup O2a strains were grown in glucose-enriched Lennox L broth, they produced lipopolysaccharide molecules with fewer high-molecular-weight O-antigen units than did strains grown in broth without the addition of glucose. Strains grown in glucose-enriched medium became sensitive to rainbow trout serum killing, indicating that the high-molecular-weight O-antigen side chains prevented the activated complement from damaging the bacterium.