bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Role for Interleukin-6 in Host Defense against MurineChlamydia trachomatisInfection
Authors: Williams Dwight M. , Grubbs Barry G. , Darville Toni , Kelly Kathleen , Rank Roger G. 
Published: March 2020

ABSTRACTInterleukin-6-deficient (IL-6−/−) knockout mice had significantly increasedChlamydia trachomatislevels in lung tissue and increased mortality compared to B6129F2/J controls early after intranasal infection. Gamma interferon production and chlamydia-specific antibody levels were consistent with a decreased but reversible Th1-like response in IL-6−/−mice. IL-6 is needed for an optimal early host response to this infection.
Construction of a Stable Attenuated
Shigella sonnei
Δ
virG
Vaccine Strain, WRSS1, and Protective Efficacy and Immunogenicity in the Guinea Pig Keratoconjunctivitis Model
Authors: Hartman Antoinette B. , Venkatesan Malabi M. 
Published: March 2020

ABSTRACT

Construction of a stable
Shigella sonnei
vaccine has been complicated by the instability of the virulence phenotype caused by the spontaneous loss of the invasion plasmid. To select a suitable candidate for vaccine construction, 16
S. sonnei
strains were screened for stability of the virulence phenotype. A stable strain,
S. sonnei
Mosely, was selected for further work. pΔvirG2, a deletion derivative of the
virG
gene in the
sacB
suicide vector pCVD442, was used to generate an
S. sonnei virG
deletion strain, WRSS1, which was invasive in HeLa cells but negative in the Sereny test. WRSS1 was found to be both immunogenic and protective in the guinea pig keratoconjunctivitis model.
NF-κB1 (p50) Is Upregulated in Lipopolysaccharide Tolerance and Can Block Tumor Necrosis Factor Gene Expression
Authors: Kastenbauer Stefan , Ziegler-Heitbrock H. W. Löms 
Published: March 2020

ABSTRACTMonocytes respond to lipopolysaccharide (LPS) stimulation with a rapid expression of the tumor necrosis factor (TNF) gene. Upon repeated LPS stimulation there is, however, little production of TNF mRNA and protein; i.e., the cells are tolerant to LPS. Analysis of NF-κB proteins in gel shift assays demonstrated that the DNA binding activity that is induced by LPS stimulation in tolerant cells consists mainly of p50-p50 homodimers. Since p50 can bind to DNA but lacks a transactivation domain, this may explain the blockade of TNF gene expression. We now show that in the monocytic cell line Mono Mac 6, this inability to respond can be largely ascribed to NF-κB, since a reporter construct directed by a trimeric NF-κB motif is strongly transactivated by LPS stimulation of naive cells whereas LPS-tolerant cells exhibit only low activity. Also, Western blot analyses of proteins extracted from purified nuclei showed mobilization of threefold-higher levels of p50 protein in tolerant compared to naive cells, while mobilization of p65 was unaltered. Overexpression of p50 in HEK 293 cells resulted in a strong reduction of p65-driven TNF promoter activity at the levels of both luciferase mRNA and protein. These data support the concept that an upregulation of p50 is instrumental in LPS tolerance in human monocytes.
Interleukin-10 and Antigen-Presenting Cells Actively Suppress Th1 Cells in BALB/c Mice Infected with the Filarial ParasiteBrugia pahangi
Authors: Osborne Julie , Devaney Eileen 
Published: March 2020

ABSTRACTInfection with the third-stage larvae (L3) of the filarial nematodeBrugiaresults in a Th2-biased immune response in mice and humans. Previously we have shown that the production of interleukin 4 (IL-4) is critical for down-regulating polyclonal Th1 responses in L3-infected mice. However, the in vitro neutralization of IL-4 did not fully recover the defective polyclonal Th1 responses, nor did it result in the production of any antigen (Ag)-specific Th1 cytokines, suggesting that perhaps infection with L3 does not result in priming of Th1 cells in vivo. In this study, we analyzed the role of IL-10 and Ag-presenting cells (APCs) in the spleen as additional factors controlling the Th2 bias in infected mice. Our data show that IL-10 and APCs also contribute to the suppression of mitogen-driven Th1 responses of spleen cells from infected mice. In addition, the neutralization of IL-10 or the replacement of the resident APC population from spleen cell cultures resulted in the production of Ag-specific Th1 cytokines. Irradiated spleen cells from either L3-infected or uninfected mice were able to restore Ag-specific Th1 responses in vitro. Therefore, it appears thatBrugia-reactive Th1 cells are primed following infection with L3, but are actively suppressed in vivo by a mechanism that involves IL-10 and the resident APC population, but not IL-4. These results indicate that a complex interplay of cytokines and cell populations underscores the Th2-polarized response in L3-infected mice.
Lipoteichoic Acid Acts as an Antagonist and an Agonist of Lipopolysaccharide on Human Gingival Fibroblasts and Monocytes in a CD14-Dependent Manner
Authors: Sugawara Shunji , Arakaki Rieko , Rikiishi Hidemi , Takada Haruhiko 
Published: March 2020

ABSTRACTCD14 has been implicated as a receptor of lipoteichoic acid (LTA) and other bacterial components as well as lipopolysaccharide (LPS). Since the structures of LTAs from various gram-positive bacteria are heterogeneous, we analyzed the effects of LTAs on the secretion of interleukin-8 (IL-8) by high- and low-CD14-expressing (CD14highand CD14low) human gingival fibroblasts (HGF). WhileBacillus subtilisLTA had an IL-8-inducing effect on CD14highHGF which was considerably weaker than that of LPS,Streptococcus sanguisandStreptococcus mutansLTAs had practically no effect on the cells.B. subtilisLTA had only a weak effect on CD14lowHGF, as did LPS.S. sanguisandS. mutansLTAs at a 1,000-fold excess each completely inhibited the IL-8-inducing activities of both LPS and a synthetic lipid A on CD14highHGF. The effect of LPS was also inhibited by the presence of an LPS antagonist, synthetic lipid A precursor IVA(LA-14-PP), with a 100-fold higher potency thanS. sanguisandS. mutansLTAs and by anti-CD14 monoclonal antibody (MAb).S. sanguisandS. mutansLTAs, LA-14-PP, and anti-CD14 MAb had no significant effect on phorbol myristate acetate-stimulated IL-8 secretion by HGF. These LTAs also inhibited the IL-8-inducing activity ofB. subtilisLTA on CD14highHGF, as did LA-14-PP and anti-CD14 MAb. The antagonistic and agonistic functions of LTAs were also observed with human monocytes. Binding of fluorolabeled LPS to human monocytes was inhibited byS. sanguisLTA, although the inhibition was 100 times weaker than that of LPS itself, and anti-CD14 MAb inhibited fluorolabeled LPS andS. sanguisLTA binding. Binding of LTAs to CD14 was also observed with nondenaturing polyacrylamide gel electrophoresis. These results indicate that LTAs act as antagonists or agonists via a CD14-dependent mechanism, probably due to the heterogeneous structure of LTAs, and that an antagonistic LTA might be a useful agent for suppressing the periodontal disease caused by gram-negative bacteria.
Immunization of Mice with DNA-Based Pfs25 Elicits Potent Malaria Transmission-Blocking Antibodies
Authors: Lobo Cheryl Ann , Dhar Ravi , Kumar Nirbhay 
Published: March 2020

ABSTRACTImmunological intervention, in addition to vector control and malaria chemotherapy, will be needed to stop the resurgence of malaria, a disease with a devastating impact on the health of 300 to 500 million people annually. We have pursued a vaccination strategy, based on DNA immunization in mice with genes encoding two antigens present on the sexual stages ofPlasmodium falciparum, Pfs25 and Pfg27, to induce biologically important antibodies that can block development of the parasite in theAnophelesmosquito and thus transmission of the disease. DNA encoding Pfs25 when administered by the intramuscular route, either alone or with DNA encoding Pfg27, had the most potent transmission-blocking effects, resulting in up to a 97% decrease in oocyst numbers in mosquito midguts and a 75% decrease in rate of infection. Immunization with DNA encoding a Pfg27-Pfs25 fusion protein was less effective and DNA encoding Pfg27 elicited antibodies in sera that had only modest effects on the infectivity of the parasite. These results show for the first time that DNA vaccination can result in potent transmission-blocking antibodies in mice and suggest that the Pfs25 gene should be included as part of a multicomponent DNA vaccine.
A Novel 62-Kilodalton Egg Antigen fromSchistosoma mansoniInduces a Potent CD4+T Helper Cell Response in the C57BL/6 Mouse
Authors: Asahi Hiroko , Hernandez Hector J. , Stadecker Miguel J. 
Published: March 2020

ABSTRACTIn infection withSchistosoma mansoni, hepatic granuloma formation is mediated by CD4+T helper (Th) cells sensitized to schistosomal egg antigens. There is considerable variation among infected individuals with respect to both severity of disease and the T-cell response to egg antigens. In the BL/6 mouse, the egg granulomas are relatively small and the relevant sensitizing egg antigens are largely unknown. We investigated the CD4+Th cell response of infected BL/6 mice to egg antigens fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and found a prominent lymphoproliferative response to be directed against a 62-kDa component. With the aid of a specific T-cell hybridoma, 4E6, the 62-kDa antigen was isolated; following partial digestion with endoproteinase Glu-C, an internal amino acid sequence was found to be identical with one present in the enzyme phosphoenolpyruvate carboxykinase (PEPCK) of the organismsCaenorhabditis elegansandTreponema pallidumand to differ by one residue from PEPCK of various other species. In CD4+Th cells from 7.5- 8.5-week-infected BL/6 mice, the purified 62-kDa molecule elicited a potent proliferative response which, based on cytokine analysis, was of a mixed Th-1 and Th-2 type. Our results reveal a novel egg antigen of particular prominence in the BL/6 mouse and suggest that the immune response in schistosomiasis is a product of sensitization to egg antigens that may vary considerably in immunogenicity from strain to strain.
Identification and Characterization of thecpsLocus ofStreptococcus suisSerotype 2: the Capsule Protects against Phagocytosis and Is an Important Virulence Factor
Authors: Smith Hilde E. , Damman Marloes , van der Velde Joeke , Wagenaar Frans , Wisselink Henk J. , Stockhofe-Zurwieden Norbert , Smits Mari A. 
Published: March 2020

ABSTRACTTo study the role of the capsule ofStreptococcus suisserotype 2 in virulence, we generated two isogenic mutants disturbed in capsule production. For that purpose, we first cloned and characterized a major part of the capsular polysaccharide biosynthesis (cps) locus ofS. suisserotype 2. Based on the established sequence, 14 open reading frames (ORFs), designated Orf2Z, Orf2Y, Orf2X, and Cps2A to Cps2K, were identified. Twelve ORFs belonged to a single transcriptional unit. The gene products of 11 of these ORFs showed similarity to proteins involved in polysaccharide biosynthesis of other gram-positive microorganisms. Nonencapsulated isogenic mutants were generated in thecps2Bandcps2EFgenes by insertional mutagenesis. In contrast to the wild-typeS. suisserotype 2 strain, the nonencapsulated strains were highly sensitive to ingestion by porcine alveolar lung macrophages in vitro. More importantly, the nonencapsulated mutant strains were completely avirulent in young germfree pigs after intranasal inoculation. These observations indicate that the capsule ofS. suisserotype 2 plays an essential role in the pathogenesis ofS. suisserotype 2 infections.
Anion-Coordinating Residues at Binding Site 1 Are Essential for the Biological Activity of the Diphtheria Toxin Repressor
Authors: Goranson-Siekierke Joanne , Pohl Ehmke , Hol Wim G. J. , Holmes Randall K. 
Published: March 2020

ABSTRACTThe homodimeric diphtheria toxin repressor (DtxR) uses Fe2+as a corepressor, binds to iron-regulated promoters, and negatively regulates the syntheses of diphtheria toxin, corynebacterial siderophore, and several otherCorynebacterium diphtheriaeproducts. The crystal structure of DtxR shows that the second domain of each monomer has two binding sites for Fe2+or certain other divalent metal ions. In addition, site 1 binds a sulfate or phosphate anion, suggesting that phosphate may function intracellularly as a co-corepressor. The effects of alanine substitutions for selected residues in sites 1 and 2 were determined by measuring the β-galactosidase activities of atoxoperator/promoter-lacZreporter construct inEscherichia colistrains expressing each DtxR variant. Our studies demonstrated that single alanine substitutions for the anion-binding residues in site 1 (R80A, S126A, or N130A) caused severely decreased DtxR activity, similar to the effects of alanine substitutions for metal-binding residues in site 2 (C102A, E105A, or H106A) and greater than the effects of alanine substitutions for metal-binding residues in site 1 (H79A, E83A, or H98A) reported previously by other investigators. Various combinations of alanine substitutions for site 1 and site 2 residues were also analyzed to further elucidate the roles of these cation- and anion-binding ligands in DtxR activity. Furthermore, the interaction between residue E20 in the DNA binding domain and R80 in anion/cation binding site 1 was analyzed, and the E20A variant of DtxR was shown to have a phenotype indistinguishable from that of the R80A variant. Our data demonstrated for the first time that the anion-binding residues R80, S126, and N130 at site 1 are essential for DtxR activity. The data also showed that the interaction of E20 in domain 1 with R80 in domain 2, first revealed by X-ray crystallography in apo-DtxR and holo-DtxR, is a structural feature of DtxR that is important for its repressor activity.
Targeted Disruption of Fibronectin-Integrin Interactions in Human Gingival Fibroblasts by the RI Protease of
Porphyromonas gingivalis
W50
Authors: Scragg M. A. , Cannon S. J. , Rangarajan M. , Williams D. M. , Curtis M. A. 
Published: March 2020

ABSTRACT

Cell surface integrins mediate interactions between cells and their extracellular matrix and are frequently exploited by a range of bacterial pathogens to facilitate adherence and/or invasion. In this study we examined the effects of
Porphyromonas gingivalis
proteases on human gingival fibroblast (HGF) integrins and their fibronectin matrix. Culture supernatant from the virulent strain W50 caused considerably greater loss of the β
1
integrin subunit from HGF in vitro than did that of the beige-pigmented strain W50/BE1. Prior treatment of the W50 culture supernatant with the protease inhibitor Nα-
p
-tosyl-
l
-lysine chloromethyl ketone (TLCK) blocked its effects on cultured cells, indicating that this process is proteolytically mediated. Purified arginine-specific proteases from
P. gingivalis
W50 were able to mimic the effects of the whole-culture supernatant on loss of β
1
integrin expression. However purified RI, an α/β heterodimer in which the catalytic chain is associated with an adhesin chain, was 12 times more active than RIA, the catalytic monomer, in causing loss of the α
5
β
1
integrin (fibronectin receptor) from HGF. No effect was observed on the α
V
β
3
integrin (vitronectin receptor). The sites of action of RI and RIA were investigated in cells exposed to proteases pretreated with TLCK to inactivate the catalytic component. Use of both monoclonal antibody 1A1, which recognizes only the adhesin chain of RI, and a rabbit antibody against
P. gingivalis
whole cells indicated localization of RI on the fibroblasts in a clear, linear pattern typical of that seen with fibronectin and α
5
β
1
integrin. Exact colocalization of RI with fibronectin and its α
5
β
1
receptor was confirmed by double labeling and multiple-exposure photomicroscopy. In contrast, RIA bound to fibroblasts in a weak, patchy manner, showing only fine linear or granular staining. It is concluded that the adhesin component of RI targets the
P. gingivalis
arginine-protease to sites of fibronectin deposition on HGF, contributing to the rapid loss of both fibronectin and its main α
5
β
1
integrin receptor. Given the importance of integrin-ligand interactions in fibroblast function, their targeted disruption by RI may represent a novel mechanism of damage in periodontal disease.
Examination of
Listeria monocytogenes
Intracellular Gene Expression by Using the Green Fluorescent Protein of
Aequorea victoria
Authors: Freitag Nancy E. , Jacobs Kathleen E. 
Published: March 2020

ABSTRACT

The ActA protein of
Listeria monocytogenes
is an essential virulence factor and is required for intracellular bacterial motility and cell-to-cell spread.
plcB
, cotranscribed with
actA
, encodes a broad-specificity phospholipase C that contributes to lysis of host cell vacuoles and cell-to-cell spread. Construction of a transcriptional fusion between
actA-plcB
and the green fluorescent protein gene of
Aequorea victoria
has facilitated the detailed examination of patterns of
actA/plcB
expression within infected tissue culture cells.
actA/plcB
expression began approximately 30 min postinfection and was dependent upon entry of
L. monocytogenes
into the host cytosol.
L. monocytogenes Δhly
mutants, which are unable to escape from host cell vacuoles, did not express
actA/plcB
at detectable levels within infected tissue culture cells; however, complementation of the
hly
defect allowed entry of the bacteria into the host cytoplasm and subsequent
actA/plcB
expression. These results emphasize the ability of
L. monocytogenes
to sense the different host cell compartment environments encountered during the course of infection and to regulate virulence gene expression in response.
Oligomerization of Anthrax Toxin Protective Antigen and Binding of Lethal Factor during Endocytic Uptake into Mammalian Cells
Authors: Singh Yogendra , Klimpel Kurt R. , Goel Seema , Swain Prabodha K. , Leppla Stephen H. 
Published: March 2020

ABSTRACT
The protective antigen (PA) protein of anthrax toxin binds to a cellular receptor and is cleaved by cell surface furin to produce a 63-kDa fragment (PA63). The receptor-bound PA63 oligomerizes to a heptamer and acts to translocate the catalytic moieties of the toxin, lethal factor (LF) and edema factor (EF), from endosomes to the cytosol. In this report, we used nondenaturing gel electrophoresis to show that each PA63 subunit in the heptamer can bind one LF molecule. Studies using PA immobilized on a plastic surface showed that monomeric PA63 is also able to bind LF. The internalization of PA and LF by cells was studied with radiolabeled and biotinylated proteins. Uptake was relatively slow, with a half-time of 30 min. The number of moles of LF internalized was nearly equal to the number of moles of PA subunit internalized. The essential role of PA oligomerization in LF translocation was shown with PA protein cleaved at residues 313-314. The oligomers formed by these proteins during uptake into cells were not as stable when subjected to heat and detergent as were those formed by native PA. The results show that the structure of the toxin proteins and the kinetics of proteolytic activation, LF binding, and internalization are balanced in a way that allows each PA63 subunit to internalize an LF molecule. This set of proteins has evolved to achieve highly efficient internalization and membrane translocation of the catalytic components, LF and EF.
Capsular Sialic Acid Limits C5a Production on Type III Group B Streptococci
Authors: Takahashi Shinji , Aoyagi Youko , Adderson Elisabeth E. , Okuwaki Yoshiyuki , Bohnsack John F. 
Published: March 2020

ABSTRACTThe majority of type III group B streptococcus (GBS) human neonatal infections are caused by a genetically related subgroup called III-3. We have proposed that a bacterial enzyme, C5a-ase, contributes to the pathogenesis of neonatal infections with GBS by rapidly inactivating C5a, a potent pro-inflammatory molecule, but many III-3 strains do not express C5a-ase. The amount of C5a produced in serum following incubation with representative type III strains was quantitated in order to better understand the relationship between C5a production and C5a-ase expression. C5a production following incubation of bacteria with serum depleted of antibody to the bacterial surface was inversely proportional to the sialic acid content of the bacterial capsule, with the more heavily sialylated III-3 strains generating less C5a than the less-virulent, less-sialylated III-2 strains. The amount of C5a produced correlated significantly with C3 deposition on each bacterial strain. Repletion with type-specific antibody caused increased C3b deposition and C5a production through alternative pathway activation, but C5a was functionally inactivated by strains that expressed C5a-ase. The increased virulence of III-3 strains compared to that of III-2 strains results at least partially from the higher sialic acid content of III-3 strains, which inhibits both opsonophagocytic killing and C5a production in the absence of type-specific antibody. We propose that C5a-ase is not necessary for III-3 strains to cause invasive disease because the high sialic acid content of III-3 strains inhibits C5a production.
Humoral Immunity to Commensal Oral Bacteria in Human Infants: Salivary Secretory Immunoglobulin A Antibodies Reactive with
Streptococcus mitis
biovar 1,
Streptococcus oralis
,
Streptococcus mutans
, and
Enterococcus faecalis
during the First Two Years of Life
Authors: Cole Michael F. , Bryan Stacey , Evans Mishell K. , Pearce Cheryl L. , Sheridan Michael J. , Sura Patricia A. , Wientzen Raoul L. , Bowden George H. W. 
Published: March 2020

ABSTRACT

Secretory immunoglobulin A (SIgA) antibodies reactive with the pioneer oral streptococci
Streptococcus mitis
biovar 1 and
Streptococcus oralis
, the late oral colonizer
Streptococcus mutans
, and the pioneer enteric bacterium
Enterococcus faecalis
in saliva samples from 10 human infants from birth to age 2 years were analyzed. Low levels of salivary SIgA1 and SIgA2 antibodies reactive with whole cells of all four species were detected within the first month after birth, even though
S. mutans
and
E. faecalis
were not recovered from the mouths of the infants during the study period. Although there was a fivefold increase in the concentration of SIgA between birth and age 2 years, there were no differences between the concentrations of SIgA1 and SIgA2 antibodies reactive with the four species over this time period. When the concentrations of SIgA1 and SIgA2 antibodies reactive with all four species were normalized to the concentrations of SIgA1 and SIgA2 in saliva, SIgA1 and SIgA2 antibodies reactive with these bacteria showed a significant decrease from birth to 2 years of age. Adsorption of each infant’s saliva with cells of one species produced a dramatic reduction of antibodies recognizing the other three species. Sequential adsorption of saliva samples removed all SIgA antibody to the bacteria, indicating that the SIgA antibodies were directed to antigens shared by all four species. The induction by the host of a limited immune response to common antigens that are likely not involved in adherence may be among the mechanisms that commensal streptococci employ to persist in the oral cavity.