bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotype Switching Increases Efficacy of Antibody Protection againstCryptococcus neoformansInfection in Mice
Authors: Yuan Rui Rong , Spira Gadi , Oh Jin , Paizi Melia , Casadevall Arturo , Scharff Matthew D. 
Published: December 2019

ABSTRACTThe isotype and epitope specificities of antibodies both contribute to the efficacy of antibodies that mediate immunity toCryptococcus neoformans, but the relationship between these properties is only partially understood. In this study, we analyzed the efficacy of protection of two sets of immunoglobulin G (IgG) isotype switch variants from two IgG3 monoclonal antibodies (MAbs) which are either not protective or disease enhancing, depending on the mouse model used. The two IgG3 MAbs 3E5 and 4H3 have different epitope specificities. Protection experiments were done with A/JCr mice infected intravenously withC. neoformansand administered with 3E5 IgG3 and its IgG1, IgG2a, and IgG2b switch variants. These experiments revealed that IgG1, IgG2b, and IgG2a were each more effective than IgG3. For 4H3 IgG3 and its IgG1 and IgG2b switch variants, the relative efficacy was IgG2b > IgG1 >> IgG3. The combination of 3E5 IgG3 and 4H3 IgG3 was more deleterious than either IgG3 alone. All IgG isotypes were opsonic for mouse bronchoalveolar cells, with the relative efficacy being IgG2b > IgG2a > IgG1 > IgG3. These results (i) confirm that a nonprotective IgG3 MAb can be converted to a protective MAb by isotype switching, (ii) indicate that the efficacy of protection of an IgG1 MAb can be increased by isotype switching to another subclass, (iii) show that protective and nonprotective IgG MAbs are opsonic, and (iv) provide additional evidence for the concept that the efficacy of the antibody response toC. neoformansis dependent on the type of MAb elicited.
Chimeric Clostridial Cytotoxins: Identification of the N-Terminal Region Involved in Protein Substrate Recognition
Authors: Hofmann Fred , Busch Christian , Aktories Klaus 
Published: December 2019

ABSTRACT

Clostridium sordellii
lethal toxin is a member of the family of large clostridial cytotoxins that glucosylate small GTPases. In contrast to
Clostridium difficile
toxins A and B, which exclusively modify Rho subfamily proteins,
C. sordellii
lethal toxin also glucosylates Ras subfamily proteins. By deletion analysis and construction of chimeric fusion proteins of
C. sordellii
lethal toxin and
C. difficile
toxin B, we localized the enzyme activity of the lethal toxin to the N terminus of the holotoxin and identified the region involved in protein substrate specificity. The toxin fragment of the N-terminal 546 amino acid residues of
C. sordellii
lethal toxin glucosylated Rho and Ras subfamily proteins, as the holotoxin did. Deletion of a further 30 amino acid residues from the C terminus of this active fragment drastically reduced glucotransferase activity and blocked glucohydrolase activity. Exchange of amino acid residues 364 through 516 of lethal toxin for those in the active toxin B fragment (1 to 546) allowed glucosylation of Ras subfamily proteins. In contrast, the chimera with amino acids 1 to 364 from toxin B, 365 to 468 from lethal toxin, and 469 to 546 from toxin B exhibited markedly reduced modification of Ras subfamily proteins, whereas modification of Rac and Cdc42 was hardly changed. The data indicate that the region of amino acid residues 364 through 516 primarily defines the substrate specificity of
C. sordellii
lethal toxin.
Biased T-Cell Antigen Receptor Repertoire in Lyme Arthritis
Authors: Roessner Karen , Trivedi Harsh , Gaur Lakshmi , Howard Diantha , Aversa John , Cooper Sheldon M. , Sigal Leonard H. , Budd Ralph C. 
Published: December 2019

ABSTRACTA common concern with many autoimmune diseases of unknown etiology is the extent to which tissue T-lymphocyte infiltrates, versus a nonspecific infiltrate, reflect a response to the causative agent. Lyme arthritis can histologically resemble rheumatoid synovitis, particularly the prominent infiltration by T lymphocytes. This has raised speculation about whether Lyme synovitis represents an ongoing response to the causative spirochete,Borrelia burgdorferi, or rather a self-perpetuating autoimmune reaction. In an effort to answer this question, the present study examined the repertoire of infiltrating T cells in synovial fluid from nine Lyme arthritis patients, before and after stimulation withB. burgdorferi. Using a highly sensitive and consistent quantitative PCR technique, a comparison of the T-cell antigen receptor (TCR) β-chain variable (Vβ) repertoires of the peripheral blood and synovial fluid showed a statistically significant increase in expression of Vβ2 and Vβ6 in the latter. This is remarkably similar to our previous findings in studies of rheumatoid arthritis and to other reports on psoriatic skin lesions. However, stimulation of synovial fluid T cells withB. burgdorferiprovoked active proliferation but not a statistically significant increase in expression of any TCR Vβ, including Vβ2 and Vβ6. Collectively, the findings suggest that the skewing of the TCR repertoire of fresh synovial fluid in Lyme arthritis may represent more a synovium-tropic or nonspecific inflammatory response, similar to that occurring in rheumatoid arthritis or psoriasis, rather than a specificBorreliareaction.
Chemokine Production by a Human Alveolar Epithelial Cell Line in Response toMycobacterium tuberculosis
Authors: Lin Yuanguang , Zhang Ming , Barnes Peter F. 
Published: December 2019

ABSTRACTTo investigate the role of chemokines during the initial local response toMycobacterium tuberculosisin the human lung, we studied chemokine production by the human alveolar epithelial cell line A549 after infection withM. tuberculosis. M. tuberculosis-infected A549 cells produced mRNAs and protein for monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) but not mRNAs for macrophage inflammatory protein 1α (MIP-1α), MIP-1β, and RANTES. Chemokine production in response toM. tuberculosiswas not dependent on production of tumor necrosis factor alpha, IL-1β, or IL-6. Two virulent clinicalM. tuberculosisisolates, the virulent laboratory strain H37Rv, and the avirulent strain H37Ra elicited production of comparable concentrations of MCP-1 and IL-8, whereas killedM. tuberculosisand threeMycobacterium aviumstrains did not. The three virulentM. tuberculosisstrains grew more rapidly than the avirulentM. tuberculosisstrain in the alveolar epithelial cell line, and the threeM. aviumstrains did not grow intracellularly. These findings suggest that intracellular growth is necessary for mycobacteria to elicit production of MCP-1 and IL-8 by alveolar epithelial cells but that virulence and the rate of intracellular growth do not correlate with chemokine production. Alveolar epithelial cells may contribute to the local inflammatory response in human tuberculosis by producing chemokines which attract monocytes, lymphocytes, and polymorphonuclear cells.
SalmonellaFlagellin Induces Tumor Necrosis Factor Alpha in a Human Promonocytic Cell Line
Authors: Ciacci-Woolwine Federica , Blomfield Ian C. , Richardson Stephen H. , Mizel Steven B. 
Published: December 2019

ABSTRACTDuring infection of the gastrointestinal tract, salmonellae induce cytokine production and inflammatory responses which are believed to mediate tissue damage in the host. In a previous study, we reported that salmonellae possess the ability to stimulate tumor necrosis factor alpha (TNF-α) accumulation in primary human monocytes, as well as in the human promonocytic cell line U38. In this model system, cytokine upregulation is not due to lipopolysaccharide but is mediated by a released protein. In the present study, TnphoAtransposon mutagenesis was used to identify the TNF-α-inducing factor. A mutantSalmonellastrain which lacks the ability to induce TNF-α was isolated from a TnphoAlibrary. Genetic analysis of this mutant demonstrated that thehnsgene has been interrupted by transposon insertion. Thehnsgene product is a DNA-binding protein that regulates the expression of a variety of unrelated genes in salmonellae. One of the known targets of histone-like protein H1 isflhDC, the master operon which is absolutely required for flagellar expression. Analysis of other nonflagellated mutantSalmonellastrains revealed a correlation between the ability to induce TNF-α and the expression of the phase 1 filament subunit protein FliC. Complementation experiments demonstrated that FliC is sufficient to restore the ability of nonflagellated mutantSalmonellastrains to upregulate TNF-α, whereas the phase 2 protein FljB appears to complement to a lesser extent. In addition,SalmonellaFliC can confer the TNF-α-inducing phenotype onEscherichia coli, which otherwise lacks the activity. Furthermore, assembly of FliC into complete flagellar structures may not be required for induction of TNF-α.
Human Platelets DamageAspergillus fumigatusHyphae and May Supplement Killing by Neutrophils
Authors: Christin Laurent , Wysong Deborah R. , Meshulam Tova , Hastey Ryan , Simons Elizabeth R. , Diamond Richard D. 
Published: December 2019

ABSTRACTNeutropenia is considered a significant risk factor for invasive aspergillosis but is almost always associated with concurrent thrombocytopenia. Studies determined that platelets, like neutrophils, attached to cell walls of the invasive hyphal form ofAspergillus fumigatus. Organisms were damaged as shown by loss of cell wall integrity in scanning laser confocal microscopy and release of defined hyphal surface glycoproteins. Rapid expression appearance of surface antigen CD63 and release of markers of platelet degranulation confirmed activation during attachment to hyphae. Optimal platelet activation required opsonization of hyphae with fresh or heat-inactivated whole plasma. These effects of opsonization with whole plasma could not be duplicated by pooled human serum, immunoglobulin G, or fibrinogen, whether used separately or combined. Thus, platelets in the presence of whole plasma have the potential to play an important role in normal host defenses against invasive aspergillosis.
Identification of Macrophage-Specific Infectivity Loci (
mil
) of
Legionella pneumophila
That Are Not Required for Infectivity of Protozoa
Authors: Gao Lian-Yong , Harb Omar S. , Kwaik Yousef Abu 
Published: December 2019

ABSTRACT

We have recently shown that many mutants of
Legionella pneumophila
exhibit similar defective phenotypes within both U937 human-derived macrophages and the protozoan host
Acanthamoeba
(L.-Y. Gao, O. S. Harb, and Y. Abu Kwaik, Infect. Immun. 65:4738–4746, 1997). These observations have suggested that many of the mechanisms utilized by
L. pneumophila
to parasitize mammalian and protozoan cells are similar, but our data have not excluded the possibility that there are unique mechanisms utilized by
L. pneumophila
to survive and replicate within macrophages but not protozoa. To examine this possibility, we screened a bank of 5,280 miniTn
10
::kan transposon insertion mutants of
L. pneumophila
for potential mutants that exhibited defective phenotypes of cytopathogenicity and intracellular replication within macrophage-like U937 cells but not within
Acanthamoeba polyphaga
. We identified 32 mutants with various degrees of defects in cytopathogenicity, intracellular survival, and replication within human macrophages, and most of the mutants exhibited wild-type phenotypes within protozoa. Six of the mutants exhibited mild defects in protozoa. The defective loci were designated
mil
(for macrophage-specific infectivity loci). Based on their intracellular growth defects within macrophages, the
mil
mutants were grouped into five phenotypic groups. Groups I to III included the mutants that were severely defective in macrophages, while members of the other two groups exhibited a modestly defective phenotype within macrophages. The growth kinetics of many mutants belonging to groups I to III were also examined, and these were shown to have a similar defective phenotype in peripheral blood monocytes and a wild-type phenotype within another protozoan host,
Hartmannella vermiformis
. Transmission electron microscopy of
A. polyphaga
infected by three of the
mil
mutants belonging to groups I and II showed that they were similar to the parent strain in their capacity to recruit the rough endoplasmic reticulum (RER) around the phagosome. In contrast, infection of macrophages showed that the three mutants failed to recruit the RER around the phagosome during early stages of the infection. None of the
mil
mutants was resistant to NaCl, and the
dot
or
icm
NaCl
r
mutants are severely defective within mammalian and protozoan cells. Our data indicated that in addition to differences in mechanisms of uptake of
L. pneumophila
by macrophages and protozoa, there were also genetic loci required for
L. pneumophila
to parasitize mammalian but not protozoan cells. We hypothesize that
L. pneumophila
has evolved as a protozoan parasite in the environment but has acquired loci specific for intracellular replication within macrophages. Alternatively, ecological coevolution with protozoa has allowed
L. pneumophila
to possess multiple redundant mechanisms to parasitize protozoa and that some of these mechanisms do not function within macrophages.
Regulation of Periodontal Ligament Cell Functions by Interleukin-1β
Authors: Agarwal Sudha , Chandra Charu S. , Piesco Nicholas P. , Langkamp Herman H. , Bowen Lathe , Baran Coskun 
Published: December 2019

ABSTRACT
Periodontal ligament (PDL) cells maintain the attachment of the tooth to alveolar bone. These cells reside at a site in which they are challenged frequently by bacterial products and proinflammatory cytokines, such as interleukin-1β (IL-1β), during infections. In our initial studies we observed that IL-1β down-regulates the osteoblast-like characteristics of PDL cells in vitro. Therefore, we examined the functional significance of the loss of the PDL cell’s osteoblast-like characteristics during inflammation. In this report we show that, during inflammation, IL-1β can modulate the phenotypic characteristics of PDL cells to a more functionally significant lipopolysaccharide (LPS)-responsive phenotype. In a healthy periodontium PDL cells exhibit an osteoblast-like phenotype and are unresponsive to gram-negative bacterial LPS. Treatment of PDL cells with IL-1β inhibits the expression of their osteoblast-like characteristics, as assessed by the failure to express transforming growth factor β1 (TGF-β1) and proteins associated with mineralization, such as alkaline phosphatase and osteocalcin. As a consequence of this IL-1β-induced phenotypic change, PDL cells become responsive to LPS and synthesize proinflammatory cytokines. The IL-1β-induced phenotypic changes in PDL cells were transient, as removal of IL-1β from PDL cell cultures resulted in reacquisition of their osteoblast-like characteristics and lack of LPS responsiveness. The IL-1β-induced phenotypic changes occurred at concentrations that are frequently observed in tissue exudates during periodontal inflammation (0.05 to 5 ng/ml). The results suggest that, during inflammation in vivo, IL-1β may modulate PDL cell functions, allowing PDL cells to participate directly in the disease process by assuming LPS responsiveness at the expense of their normal structural properties and functions.
MP1
Encodes an Abundant and Highly Antigenic Cell Wall Mannoprotein in the Pathogenic Fungus
Penicillium marneffei
Authors: Cao Liang , Chan Che-man , Lee Cindy , Sai-yin Wong Samson , Yuen Kwok-yung 
Published: December 2019

ABSTRACT

We cloned the
MP1
gene, which encodes an abundant antigenic cell wall mannoprotein from the dimorphic pathogenic fungus
Penicillium marneffei. MP1
is a unique gene without homologs in sequence databases. It codes for a protein, Mp1p, of 462 amino acid residues, with a few sequence features that are present in several cell wall proteins of
Saccharomyces cerevisiae
and
Candida albicans
. It contains two putative N glycosylation sites, a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidylinositol attachment signal sequence. Specific anti-Mp1p antibody was generated with recombinant Mp1p protein purified from
Escherichia coli
to allow further characterization of Mp1p. Western blot analysis with anti-Mp1p antibody revealed that Mp1p has predominant bands with molecular masses of 58 and 90 kDa and that it belongs to a group of cell wall proteins that can be readily removed from yeast cell surfaces by glucanase digestion. In addition, Mp1p is an abundant yeast glycoprotein and has high affinity for concanavalin A, a characteristic indicative of a mannoprotein. Furthermore, ultrastructural analysis with immunogold staining indicated that Mp1p is present in the cell walls of the yeast, hyphae, and conidia of
P. marneffei
. Finally, it was observed that infected patients develop a specific antibody response against Mp1p, suggesting that this protein represents a good cell surface target for host humoral immunity.
Glycosphingolipids as Novel Targets for T-Cell Suppression by the B Subunit of Recombinant Heat-Labile Enterotoxin
Authors: Truitt Robert L. , Hanke Carrie , Radke Jay , Mueller Reinhold , Barbieri Joseph T. 
Published: December 2019

ABSTRACTHeat-labile enterotoxin subunit B (LTB) is a noncatalytic protein derived fromEscherichia colithat binds to ganglioside GM1, a glycosphingolipid on the surface of mammalian cells. In this study, the effects of recombinant LTB (rLTB) on murine lymphocytes were examined in vitro. T and B cells readily bound fluorescein isothiocyanate-labeled rLTB. CD8+T cells bound twice as much as CD4+T cells and B cells. Exposure of T-cell subsets and B cells to rLTB abrogated mitogen-driven proliferation. CD8+T cells were more susceptible to rLTB than either CD4+T cells or B cells. There were differences in the sensitivity of lymphocytes from various strains of mice to rLTB. This was attributed to qualitative and quantitative differences in the CD4+T cells. rLTB induced apoptosis in both T-cell subsets, but the level was significantly higher in CD8+T cells. Apoptosis peaked at around 8 h after exposure to rLTB and incubation at 37°C. Binding to ganglioside GM1was essential for suppression, since rLTB/G33D, a mutant which does not bind GM1, failed to inhibit proliferation or induce apoptosis. Naive T cells, which were acutely sensitive to rLTB, became more resistant after activation. Conversely, activated T cells regained their sensitivity to rLTB when they reverted back to a resting state. A 1-h pulse with rLTB was sufficient to inhibit T-cell proliferation and cytotoxic-T-lymphocyte generation in primary mixed lymphocyte reaction cultures. CD8+T cells were preferentially depleted in these cultures. rLTB also induced functional modifications in T cells as indicated by inhibition of gamma interferon secretion after polyclonal activation. Thus, rLTB may have immunomodulatory properties independent of its ability to induce apoptosis.
Molecular Cloning and Characterization of the Genes Coding for the Highly Immunogenic Cluster of 90-Kilodalton Envelope Proteins from theChlamydia psittaciSubtype That Causes Abortion in Sheep
Authors: Longbottom David , Russell Mary , Dunbar Susanna M. , Jones Gareth E. , Herring Alan J. 
Published: December 2019

ABSTRACTProteins present in the outer membrane of chlamydiae that are involved in mucosal epithelial cell infection must clearly be identified and characterized if we are to understand and modify the pathogenic mechanisms utilized by these organisms. We have identified and isolated a family of four genes encoding putative outer membrane proteins (POMPs), a group of proteins of approximately 90 kDa present in the outer membrane of the subtype ofChlamydia psittacithat causes ovine enzootic abortion (strain S26/3). These proteins, although minor components, are major immunogens, as shown by the immunoblotting of chlamydial outer membrane complexes with postabortion sheep sera, and are therefore potential diagnostic and/or protective antigen candidates. Immunoblotting of the expressed amino- and carboxy-terminal halves of one of the POMPs with postabortion sheep sera showed that the major humoral immune response appeared to be directed solely against the amino-terminal half. This result, in combination with the positive immunofluorescence staining of S26/3-infected cells using POMP-specific (specific to the amino-terminal half of the proteins) monoclonal antibodies, suggests the probable surface localization of the POMPs and, more specifically, the surface exposure of the amino-terminal half of these proteins. The fourpompgenes are highly homologous, sharing 82 to 100% similarity with each other (two of the genes are identical). Genes with strong and weak homologies were also detected inC. psittaciavian and feline pneumonitis strains, respectively. Nopomphomologs were found in strains ofC. trachomatisandC. pneumoniae, but this does not preclude their existence. The absence of homology with various subtypes ofC. pecorum, which complicate the diagnosis of the ovine abortion subtype, indicates the possible suitability of the these 90-kDa proteins as serodiagnostic antigens.
Elastase Is the Only Human Neutrophil Granule Protein That Alone Is Responsible for In Vitro Killing of
Borrelia burgdorferi
Authors: Garcia Rodolfo , Gusmani Laura , Murgia Rossella , Guarnaccia Corrado , Cinco Marina , Rottini Giandomenico 
Published: December 2019

ABSTRACT

Phagocytosis of
Borrelia burgdorferi
by human polymorphonuclear leukocytes triggers oxygen-dependent and -independent mechanisms of potentially cidal outcome. Nevertheless, no factor or process has yet been singled out as being borreliacidal. We have studied the
B. burgdorferi
-killing ability of the myeloperoxidase-H
2
O
2
-chloride system and that of primary and secondary granule components in an in vitro assay. We found that neither secondary granule acid extracts nor the chlorinating system could kill these microorganisms, while primary granule extracts were effective. The
Borrelia
-killing factor was purified to homogeneity and demonstrated to be elastase. Its cidal activity was found to be independent of its proteolytic activity.