bluuebunny/crossref_metadata_2025_split huggingface dataset:
VirulentBrucella abortusPrevents Lysosome Fusion and Is Distributed within Autophagosome-Like Compartments
Authors: Pizarro-Cerdá Javier , Moreno Edgardo , Sanguedolce Veronique , Mege Jean-Louis , Gorvel Jean-Pierre 
Published: December 2019

ABSTRACTVirulent and attenuatedBrucella abortusstrains attach to and penetrate nonprofessional phagocytic HeLa cells. Compared to pathogenicBrucella, the attenuated strain 19 hardly replicates within cells. The majority of the strain 19 bacteria colocalized with the lysosome marker cathepsin D, suggesting thatBrucella-containing phagosomes had fused with lysosomes, in which they may have degraded. The virulent bacteria prevented lysosome-phagosome fusion and were found distributed in the perinuclear region within compartments resembling autophagosomes.
Activity of Protegrins against Yeast-Phase
Candida albicans
Authors: Cho Yoon , Turner Jeffrey S. , Dinh Nhu-Nguyen , Lehrer Robert I. 
Published: December 2019

ABSTRACT

We used a two-stage radial diffusion assay to perform a structure-activity study of the antifungal effects of protegrin-1 (PG-1) on yeast-phase
Candida albicans
. While doing so, we computed MICs from the radial diffusion assay data by three methods and compared the respective values with results from colony count and broth microdilution assays. This allowed us to identify several technical modifications that improved the sensitivity and accuracy of radial diffusion assays. We found that both PG-1 and enantiomeric PG-1 (composed exclusively of
d
-amino acids) were potently fungicidal for yeast-phase
C. albicans
. The protegrins PG-2, -3, and -5, but not PG-4, were as effective as PG-1. At least one intramolecular disulfide bond was required to retain optimal candidacidal activity at physiological NaCl concentrations. Truncated variants of PG-1 that lacked its first four residues showed decreased candidacidal activity, although their activity against bacteria was substantially intact. Altering the β-turn region (residues 9 to 12) of PG-1 or its variants further decreased candidacidal activity. These studies suggest that only 12 residues are needed to endow protegrin molecules with strong antibacterial activity and that at least 4 additional residues are needed to add potent antifungal properties. Thus, the 16-residue protegrin PG-2 likely represents the minimal structure needed for broad-spectrum antimicrobial activity encompassing bacteria and fungi.
The
Vibrio cholerae
Mannose-Sensitive Hemagglutinin Is the Receptor for a Filamentous Bacteriophage from
V. cholerae
O139
Authors: Jouravleva Elena A. , McDonald Gregory A. , Marsh Jane W. , Taylor Ronald K. , Boesman-Finkelstein Mary , Finkelstein Richard A. 
Published: December 2019

ABSTRACT

We previously isolated from a 1994 isolate of
Vibrio cholerae
O139 a filamentous lysogenic bacteriophage, choleraphage 493, which inhibits pre-O139 but not post-O139 El Tor biotype
V. cholerae
strains in plaque assays. We investigated the role of the mannose-sensitive hemagglutinin (MSHA) type IV pilus as a receptor in phage 493 infection. Spontaneous, Tn
5
insertion, and
mshA
deletion mutants are resistant to 493 infection. Susceptibility is restored by
mshA
complementation of deletion mutants. Additionally, the 493 phage titer is reduced by adsorption with MSHA-positive strains but not with a Δ
mshA1
strain. Monoclonal antibody against MSHA inhibits plaque formation. We conclude that MSHA is the receptor for phage 493. The emergence and decline of O139 in India and Bangladesh are correlated with the susceptibility and resistance of El Tor strains to 493. However,
mshA
gene sequences of post-O139 strains are identical to those of susceptible pre-O139 isolates, indicating that phage resistance of El Tor is not due to a change in
mshA
. Classical biotype strains are (with rare exceptions) hemagglutinin negative and resistant to 493 in plaque assays. Nevertheless, they express the
mshA
pilin gene. They can be infected with 493 and produce low levels of phage DNA, like post-O139 El Tor strains. Resistance to 493 in plaque assays is thus not equivalent to resistance to infection. The ability of filamentous phages, such as 493, to transfer large amounts of DNA provides them, additionally, with the potential for quantum leaps in both identity and pathogenicity, such as the conversion of El Tor to O139.
Interleukin-15 Activates Proinflammatory and Antimicrobial Functions in Polymorphonuclear Cells
Authors: Musso Tiziana , Calosso Liliana , Zucca Mario , Millesimo Maura , Puliti Manuela , Bulfone-Paus Silvia , Merlino Chiara , Savoia Dianella , Cavallo Rossana , Ponzi Alessandro Negro , Badolato Raffaele 
Published: December 2019

ABSTRACTInterleukin-15 (IL-15) is a recently discovered cytokine produced by a wide range of different cell types including fibroblasts, keratinocytes, endothelial cells, and macrophages in response to lipopolysaccharide or microbial infection. This suggests that IL-15 may play a crucial role in the activation of phagocytic cells against pathogens. We studied polymorphonuclear leukocyte (PMN) activation by IL-15, evaluated as enhancement of PMN anti-Candidaactivity as well as IL-8 production, following stimulation with the cytokine. The PMN response to IL-15 depends on binding to the IL-15 receptor. Our experiments show that binding of a biotinylated human IL-15–immunoglobulin G2b IgG2b fusion protein was competed by the addition of human recombinant IL-15 (rIL-15) or of human rIL-2, suggesting that IL-15 binding to PMN might involve the IL-2Rβ and IL-2Rγ chains, which have been shown to be constitutively expressed by PMN. In addition, we show by reverse transcription-PCR and by flow cytometry with a specific anti-IL-15Rα chain monoclonal antibody that PMN express the IL-15Rα chain at the mRNA and protein levels. Incubation with IL-15 activated PMN to secrete the chemotactic factor IL-8, and the amount secreted was increased by costimulation with heat-inactivatedCandida albicans. In addition, IL-15 primed the metabolic burst of PMN in response to formyl-methionyl-leucyl-phenylalanine but was not sufficient to trigger the respiratory burst or to increase the production of superoxide in PMN exposed toC. albicans. IL-15 also increased the ability of PMN to phagocytose heat-killedC. albicansorganisms in a dose-dependent manner, without opsonization by antibodies or complement-derived products. In the same concentration range, IL-15 was as effective as gamma interferon (IFN-γ) and IL-2 in increasing theC. albicansgrowth-inhibitory activity of PMN. Taken together, these results suggest that IL-15 is a potent stimulant of both proinflammatory and antifungal activities of PMN, activating several antimicrobial functions of PMN involved in the cellular response againstC. albicans.
Molecular and Immunological Analyses of the
Mycobacterium avium
Homolog of the Immunodominant
Mycobacterium leprae
35-Kilodalton Protein
Authors: Triccas James A. , Winter Nathalie , Roche Paul W. , Gilpin Andrea , Kendrick Kathleen E. , Britton Warwick J. 
Published: December 2019

ABSTRACT

The analysis of host immunity to mycobacteria and the development of discriminatory diagnostic reagents relies on the characterization of conserved and species-specific mycobacterial antigens. In this report, we have characterized the
Mycobacterium avium
homolog of the highly immunogenic
M. leprae
35-kDa protein. The genes encoding these two proteins were well conserved, having 82% DNA identity and 90% identity at the amino acid level. Moreover both proteins, purified from the fast-growing host
M. smegmatis
, formed multimeric complexes of around 1000 kDa in size and were antigenically related as assessed through their recognition by antibodies and T cells from
M. leprae
-infected individuals. The 35-kDa protein exhibited significant sequence identity with proteins from
Streptomyces griseus
and the cyanobacterium
Synechoccocus
sp. strain PCC 7942 that are up-regulated under conditions of nutrient deprivation. The 67% amino acid identity between the
M. avium
35-kDa protein and SrpI of
Synechoccocus
was spread across the sequences of both proteins, while the homologous regions of the 35-kDa protein and the P3 sporulation protein of
S. griseus
were interrupted in the P3 protein by a divergent central region. Assessment by PCR demonstrated that the gene encoding the
M. avium
35-kDa protein was present in all 30
M. avium
clinical isolates tested but absent from
M. intracellulare
,
M. tuberculosis
, or
M. bovis
BCG. Mice infected with
M. avium
, but not
M. bovis
BCG, developed specific immunoglobulin G antibodies to the 35-kDa protein, consistent with the observation that tuberculosis patients do not recognize the antigen. Strong delayed-type hypersensitivity was elicited by the protein in guinea pigs sensitized with
M. avium.
Indications of the Protective Role of Natural Killer Cells in Human Cutaneous Leishmaniasis in an Area of Endemicity
Authors: Maasho Kerima , Sanchez Fabio , Schurr Erwin , Hailu Asrat , Akuffo Hannah 
Published: December 2019

ABSTRACTThe role of natural versus acquired immunity toLeishmania aethiopicainfection in humans is the focus of our studies. We found in previous studies that mononuclear cells from nonexposed healthy Swedish donors responded toLeishmaniaantigen stimulation by proliferation and gamma interferon production. The main cell type responding was CD3−CD16/56+natural killer (NK) cells. These findings led us to suggest that the potential to produce a rapid, nonacquired NK cell response may be a protective phenotype. In order to test this hypothesis, an area in Ethiopia whereLeishmaniais endemic was selected, and peripheral blood mononuclear cells were obtained from individuals who had lived in the area most of their lives but had no evidence of past or present leishmaniasis. Their responses were compared with those of confirmed leishmaniasis patients from the same region with active lesions or cured leishmaniasis lesions. Cells from these donors were stimulated in vitro withL. aethiopicaantigen. Responses were measured by proliferation, cytokine production, and phenotype analysis by fluorescence-activated cell sorting. The association ofNRAMP1alleles with the studied phenotype and susceptibility toL. aethiopica-induced leishmaniasis was also evaluated. The results show thatLeishmaniaantigens can induce NK cell and CD8+-T-cell responses in vitro. This is clearly seen in proliferating cells from the cured (immune) individuals and the apparently protected controls from the area of endemicity. It contrasted with the reactivity of the patients, where some NK proliferation was coupled with enhanced CD4+-T-cell proliferation. We conclude from these observations that NK cells and CD8+cells proliferating in response toLeishmaniastimulation are involved in protection from and healing of (Ethiopian) cutaneous leishmaniasis; however, such mechanisms appear to be unrelated to theNRAMP1host resistance gene.
Identification and Characterization of a 29-Kilodalton Protein fromMycobacterium tuberculosisCulture Filtrate Recognized by Mouse Memory Effector Cells
Authors: Rosenkrands Ida , Rasmussen Peter Birk , Carnio Markus , Jacobsen Susanne , Theisen Michael , Andersen Peter 
Published: December 2019

ABSTRACTCulture filtrate proteins fromMycobacterium tuberculosisinduce protective immunity in various animal models of tuberculosis. Two molecular mass regions (6 to 10 kDa and 24 to 36 kDa) of short-term culture filtrate are preferentially recognized by Th1 cells in animal models as well as by patients with minimal disease. In the present study, the 24- to 36-kDa region has been studied, and the T-cell reactivity has been mapped in detail. Monoclonal antibodies were generated, and one monoclonal antibody, HYB 71-2, with reactivity against a 29-kDa antigen located in the highly reactive region below the antigen 85 complex was selected. The 29-kDa antigen (CFP29) was purified fromM. tuberculosisshort-term culture filtrate by thiophilic adsorption chromatography, anion-exchange chromatography, and gel filtration. In its native form, CFP29 forms a polymer with a high molecular mass. CFP29 was mapped in two-dimensional electrophoresis gels as three distinct spots just below the antigen 85 complex component MPT59. CFP29 is present in both culture filtrate and the membrane fraction fromM. tuberculosis, suggesting that this antigen is released from the envelope to culture filtrate during growth. Determination of the N-terminal amino acid sequence allowed cloning and sequencing of thecfp29gene. The nucleotide sequence showed 62% identity to the bacteriocin Linocin fromBrevibacterium linens. Purified recombinant histidine-tagged CFP29 and native CFP29 had similar T-cell stimulatory properties, and they both elicited the release of high levels of gamma interferon from mouse memory effector cells isolated during the recall of protective immunity to tuberculosis. Interspecies analysis by immunoblotting and PCR demonstrated that CFP29 is widely distributed in mycobacterial species.
Characterization of Mannose Receptor-Dependent Phagocytosis Mediated byMycobacterium tuberculosisLipoarabinomannan
Authors: Kang Byoung K. , Schlesinger Larry S. 
Published: December 2019

ABSTRACTThe macrophage mannose receptor (MR) along with complement receptors mediates phagocytosis of theM. tuberculosisvirulent strains Erdman and H37Rv. We have determined that the terminal mannosyl units of theM. tuberculosissurface lipoglycan, lipoarabinomannan (LAM), from the Erdman strain serve as ligands for the MR. The biology of the MR (receptor binding and trafficking) in response to phagocytic stimuli is not well characterized. This study analyzes the MR-dependent phagocytosis mediated by Erdman LAM presented on a 1-μm-diameter phagocytic particle. Erdman LAM microspheres exhibited a time- and dose-dependent rapid increase in attachment and internalization by human monocyte-derived macrophages (MDMs). In contrast, internalization of LAM microspheres by monocytes was minimal. Microsphere internalization by MDMs was visualized and quantitated by immunofluorescence and confocal and electron microscopy and resembled conventional phagocytosis. Phagocytosis of LAM microspheres by MDMs was energy, cytoskeleton, and calcium dependent and was mannan inhibitable. Trypsin treatment of MDMs at 37°C, which depleted surface and recycling intracellular pools of the MR, reduced the subsequent attachment of LAM microspheres. Trypsin treatment at 4°C allowed for subsequent recovery of LAM microsphere phagocytosis at 37°C by recycled MRs. Pretreatment of MDMs with cycloheximide influenced LAM microsphere phagocytosis to only a small extent, indicating that MR-dependent phagocytosis of the microspheres was occurring primarily by preformed recycled receptors. This study characterizes the requirements for macrophage phagocytosis of a LAM-coated particle mediated by the MR. This model will be useful in further characterization of the intracellular pathway taken by phagocytic particles coated with different LAM types in macrophages following ingestion.
The Abilities of aStaphylococcus epidermidisWild-Type Strain and Its Slime-Negative Mutant To Induce Endocarditis in Rabbits Are Comparable
Authors: Perdreau-Remington Francoise , Sande Merle A. , Peters Georg , Chambers Henry F. 
Published: December 2019

ABSTRACTThe abilities of a parent and mutant pair ofStaphylococcus epidermidisstrains, the slime-producing parent RP62A and its slime-negative mutant, to establish endocarditis in a rabbit model of aortic valve endocarditis and to accumulate and adhere to surfaces in vitro were compared. Vegetation titer and infection rate depended on the presence or absence of a catheter (P= 0.020) and on inoculum size (P< 0.001) but not on the infecting strain. The ability of the parent strain vis-à-vis its mutant to accumulate in vitro on surfaces as demonstrated in a slime test did not correlate with any enhancement in the development of endocarditis in the rabbit model. In vitro initial adherence rates were identical. Both isolates accumulated to the same reduced extent in vitro in the presence of serum, albumin, or gelatin. Adhesion was equally promoted by addition of fibronectin. These data suggest that the in vitro phenomenon of accumulation described as slime production in the absence of serum may not be an important virulence determinant in vivo.
Characterization of Protective Epitopes in a Highly ConservedPlasmodium falciparumAntigenic Protein Containing Repeats of Acidic and Basic Residues
Authors: Sharma Pawan , Kumar Anil , Singh Balwan , Bharadwaj Ashima , Sailaja V. Naga , Adak T. , Kushwaha Ashima , Malhotra Pawan , Chauhan V. S. 
Published: December 2019

ABSTRACTThe delineation of putatively protective and immunogenic epitopes in vaccine candidate proteins constitutes a major research effort towards the development of an effective malaria vaccine. By virtue of its role in the formation of the immune clusters of merozoites, its location on the surface of merozoites, and its highly conserved nature both at the nucleotide sequence level and the amino acid sequence level, the antigen which contains repeats of acidic and basic residues (ABRA) of the human malaria parasitePlasmodium falciparumrepresents such an antigen. Based upon the predicted amino acid sequence of ABRA, we synthesized eight peptides, with six of these (AB-1 to AB-6) ranging from 12 to 18 residues covering the most hydrophilic regions of the protein, and two more peptides (AB-7 and AB-8) representing its repetitive sequences. We found that all eight constructs bound an appreciable amount of antibody in sera from a large proportion ofP. falciparummalaria patients; two of these peptides (AB-1 and AB-3) also elicited a strong proliferation response in peripheral blood mononuclear cells from all 11 human subjects recovering from malaria. When used as carrier-free immunogens, six peptides induced a strong, boostable, immunoglobulin G-type antibody response in rabbits, indicating the presence of both B-cell determinants and T-helper-cell epitopes in these six constructs. These antibodies specifically cross-reacted with the parasite protein(s) in an immunoblot and in an immunofluorescence assay. In another immunoblot, rabbit antipeptide sera also recognized recombinant fragments of ABRA expressed in bacteria. More significantly, rabbit antibodies against two constructs (AB-1 and AB-5) inhibited the merozoite reinvasion of human erythrocytes in vitro up to ∼90%. These results favor further studies so as to determine possible inclusion of these two constructs in a multicomponent subunit vaccine against asexual blood stages ofP. falciparum.
In Vivo Binding of Immunoglobulin M to the Surfaces ofBabesia bigemina-Infected Erythrocytes
Authors: Echaide Ignacio E. , Hines Stephen A. , McElwain Terry F. , Suarez Carlos E. , McGuire Travis C. , Palmer Guy H. 
Published: December 2019

ABSTRACTBabesia bigeminainfection of mature bovine erythrocytes results in new proteins specifically exposed on the parasitized cell surface. Monoclonal antibody (MAb) 64/32 binds a protein, designated p94, onB. bigemina-infected erythrocytes but not on either uninfected orB. bovis-parasitized erythrocytes. However, p94 was not encoded byB. bigeminaand was not a parasite-modified erythrocyte membrane protein. In contrast, we showed that p94 could be eluted from the infected erythrocyte surface and was identified as specifically bound immunoglobulin M (IgM) heavy chain for the following reasons: (i) MAb 64/32 bound a reduced molecule of 94 kDa in both infected erythrocyte lysates and normal bovine serum; (ii) MAb 64/32 bound a 94-kDa molecule in reduced preparations of purified IgM; (iii) an anti-bovine μ heavy-chain MAb, BIg73, reacted specifically with the surface of infected erythrocytes and bound the 94-kDa molecule in lysates of infected erythrocytes, normal bovine serum, and purified IgM; and (iv) immunoprecipitation of infected erythrocyte lysates with MAb 64/32 depleted the 94-kDa antigen bound by anti-μ MAb BIg73 and vice versa. Binding of IgM to the infected erythrocyte surface was detected in vivo early in acute parasitemia and occurred during both the trophozoite and merozoite stages of intraerythrocytic parasitism. The common feature of IgM binding to the parasitized erythrocyte surface among otherwise genetically and antigenically distinctB. bigeminastrains is suggestive of an advantageous role in parasite survival in vivo.
Multiple Adhesive Phenotypes Linked to Rosetting Binding of Erythrocytes inPlasmodium falciparumMalaria
Authors: Fernandez Victor , Treutiger Carl Johan , Nash Gerard B. , Wahlgren Mats 
Published: December 2019

ABSTRACTThe cerebral form of severe malaria is associated with excessive intravascular sequestration ofPlasmodium falciparum-infected erythrocytes (PRBC). Retention and accumulation of PRBC may lead to occlusion of brain microvessels and direct the triggering of acute pathologic changes. Here we report that by selection, cloning, and subcloning, we have identified rareP. falciparumparasites expressing a pan-adhesive phenotype linked to erythrocyte rosetting, a previously identified correlate of cerebral malaria. Rosetting PRBC not only bound uninfected erythrocytes but also formed autoagglutinates, adhered to endothelial cells, and bound to CD36, immunoglobulins, and the blood group A antigen. The linkage of rosetting, autoagglutination, and cytoadherence involved the coexpression on a single PRBC of ligands with multiple specificities and the binding to two or more receptors on erythrocytes and to at least two other cell adhesion molecules, including a new endothelial cell receptor forP. falciparum-infected erythrocytes. Limited proteolysis that differentially cleaved the rosetting ligand PfEMP1 from the PRBC surface abrogated all the binding phenotypes of these parasites, implicating the variant antigen PfEMP1 as a carrier of multiple ligand specificities. The results encourage the further study of pan-adhesion as a potentially important parasite phenotype in the pathogenesis of severeP. falciparummalaria.
Identification and Molecular Analysis oflbpBA, Which Encodes the Two-Component Meningococcal Lactoferrin Receptor
Authors: Lewis L. A. , Rohde K. , Gipson M. , Behrens B. , Gray E. , Toth S. I. , Roe B. A. , Dyer D. W. 
Published: December 2019

ABSTRACTWe identifiedlbpB, encoding the lipoprotein component of the meningococcal lactoferrin receptor. An LbpB mutant was unable to acquire Fe from lactoferrin and exhibits decreased surface binding to lactoferrin. Primer extension and reverse transcription-PCR analysis indicate thatlbpBandlbpAare cotranscribed on a polycistronic Fe-repressible mRNA.
Expression of
Legionella pneumophila
Virulence Traits in Response to Growth Conditions
Authors: Byrne Brenda , Swanson Michele S. 
Published: December 2019

ABSTRACT

In nature,
Legionella pneumophila
replicates exclusively as an intracellular parasite of amoebae, but it also persists in the environment as a free-living microbe. Studies of how this opportunistic pathogen recognizes and responds to distinct extracellular and intracellular environments identified a link between the growth phase and expression of traits previously correlated with virulence. When cultured in broth, only post-exponential-phase
L. pneumophila
was sodium sensitive, cytotoxic, osmotically resistant, competent to evade macrophage lysosomes, infectious, and motile. Likewise, the
L. pneumophila
phenotype changed during growth in macrophages. During the intracellular replication period, this bacterium was sodium resistant and lacked flagella; concomitant with macrophage lysis,
L. pneumophila
became sodium sensitive and flagellated. Expression of the virulent phenotype was a response to starvation, since exponential-phase
L. pneumophila
became cytotoxic, sodium sensitive, and motile after incubation in broth from stationary-phase cultures, except when it was supplemented with amino acids. Together, these data indicate that while nutrients are plentiful, intracellular
L. pneumophila
organisms are dedicated to replication; when amino acids become limiting, the progeny express virulence factors to escape the spent host, to disperse and survive in the aquatic environment, and to reestablish a protected intracellular niche favorable for growth.