bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Infection of Pregnant Ewes with
Chlamydia pecorum
Authors: Philips Helen L. , Clarkson Michael J. 
Published: December 2019

ABSTRACT

Pregnant ewes were infected in midpregnancy with three isolates of
Chlamydia pecorum
derived from the feces of healthy lambs from three different farms. Oral infection, alone or together with
Fasciola hepatica
, did not result in tissue invasion, since all placental and fecal samples were negative for chlamydiae. Intravenous infection resulted in placental infection in 16 of 18 ewes in that chlamydiae were cultured from placentas or vaginal swabs. Two ewes bore dead lambs after a shortened gestation time. The chlamydiae isolated were all
C. pecorum
. There were no significant differences between the weights of the lambs from the infected groups and those from uninfected control ewes. Most ewes showed no serological evidence of infection by the complement fixation test; therefore, it is unlikely that the enteric subtype of
C. pecorum
is responsible for the cross-reactions sometimes seen in flocks being tested for
C. psittaci
infection.
Helicobacter pylori
Disrupts Epithelial Barrier Function in a Process Inhibited by Protein Kinase C Activators
Authors: Terrés A. M. , Pajares J. M. , Hopkins A. M. , Murphy A. , Moran A. , Baird A. W. , Kelleher D. 
Published: December 2019

ABSTRACT

Helicobacter pylori
colonizes the gastric mucosa, and the infection is related to the development of diverse gastric pathologies, possibly by directly or indirectly affecting epithelial-cell function. We analyzed the influence of the bacteria on transepithelial electrical resistance (TER) on a model tight epithelium, T84, grown to confluence in permeable filters.
H. pylori
sonicates produced a dramatic decrease in TER after 1 to 2 h of exposure, while sonicates from other bacteria did not induce a significant reduction of TER. The effect induced by sonicates was mimicked by a water-soluble fraction from the bacterial surface, was not reproducible with isolated lipopolysaccharide, and was concomitant with a significant increase in the paracellular permeability of the marker molecule [
14
C]mannitol. Furthermore,
H. pylori
sonicates also provoked a significant increase in permeability to [
14
C]mannitol across rat gastric mucosa in vitro. The sonicate-induced decrease in TER in T84 monolayers was inhibited by the protein kinase C (PKC) activator phorbol myristate acetate. As PKC is directly involved in tight junction regulation, we suggest that
H. pylori
may induce intracellular signalling events counteracting PKC effects. Following long-term
H. pylori
stimulation, epithelial monolayers regained baseline resistance values slowly after 24 h. The resistance recovery process was inhibited by cycloheximide, indicating its dependency upon protein synthesis. No association between resistance variation and E-cadherin protein levels was observed. These results indicate that
H. pylori
alters in vitro the barrier properties of the epithelium, probably by generating cell signalling events counteracting the normal function of PKC. This increased permeability may provide a potential mechanism by which
H. pylori
antigens can reach the gastric lamina propria, thereby activating the mucosal immune system.
Trypanosoma cruziInfection in Tumor Necrosis Factor Receptor p55-Deficient Mice
Authors: Castaños-Velez Esmeralda , Maerlan Stephanie , Osorio Lyda M. , Åberg Frederik , Biberfeld Peter , Örn Anders , Rottenberg Martín E. 
Published: December 2019

ABSTRACTTumor necrosis factor receptor p55 (TNFRp55) mediates host resistance to several pathogens by allowing microbicidal activities of phagocytes. In the studies reported here, TNFRp55−/−mice infected with the intracellular parasiteTrypanosoma cruzishowed clearly higher parasitemia and cumulative mortality than wild-type (WT) controls did. However, gamma interferon (IFN-γ)-activated macrophages from TNFRp55−/−mice produced control levels of nitric oxide and killed the parasite efficiently in vitro. Trypanocidal mechanisms of nonphagocytic cells (myocardial fibroblasts) from both TNFRp55−/−and WT mice were also activated by IFN-γ in a dose-dependent way. However, IFN-γ-activated TNFRp55−/−nonphagocytes showed less effective killing ofT. cruzithan WT control nonphagocytes, even when interleukin 1β (IL-1β) was added as a costimulator. In vivo,T. cruzi-infected TNFRp55−/−mice and WT mice released similar levels of NO and showed similar levels of IFN-γ mRNA and inducible nitric oxide synthase mRNA in their tissues. Instead, increased susceptibility toT. cruziof TNFRp55−/−mice was associated with reduced levels of parasite-specific immunoglobulin G (IgG) (but not IgM) antibodies during infection, which is probably linked to abnormal B-cell differentiation in secondary lymphoid tissues of the mutant mice. Surprisingly,T. cruzi-infected TNFRp55−/−mice showed increased inflammatory and necrotic lesions in several tissues, especially in skeletal muscles, indicating that TNFRp55 plays an important role in controlling the inflammatory process. Accordingly, levels of Mn2+superoxide dismutase mRNA, a TNF-induced enzyme which protects the cell from the toxic effects of superoxide, were lower in mutant than in WT infected mice.
Formation of Ring-Shaped Structures on Erythrocyte Membranes after Treatment with Botulinolysin, a Thiol-Activated Hemolysin from
Clostridium botulinum
Authors: Sekiya Kachiko , Danbara Hirofumi , Futaesaku Yutaka , Haque Abdul , Sugimoto Nakaba , Matsuda Morihiro 
Published: December 2019

ABSTRACT

Damage to erythrocyte membranes by botulinolysin (BLY) was studied by electron microscopy, which revealed ring-shaped structures with inner diameters and widths of approximately 32 and 6.7 nm, respectively. BLY bound to membranes at 0°C, but subsequent treatment with glutaraldehyde prevented ring formation during further incubation at 37°C. Zn
2+
ions inhibited ring formation but not binding of BLY to membranes.
Molecular Characterization of
Treponema pallidum mcp2
, a Putative Chemotaxis Protein Gene
Authors: Greene Shermalyn R. , Stamm Lola V. 
Published: December 2019

ABSTRACT

The nucleotide sequence of the
Treponema pallidum mcp2
gene was determined.
mcp2
encodes a 45.8-kDa protein whose deduced amino acid sequence has significant homology with the C-terminal region of bacterial methyl-accepting chemotaxis proteins (MCPs). The Mcp2 N terminus lacks the hydrophobic transmembrane regions present in most MCPs. An Mcp2 fusion protein was strongly reactive with antibody (HC23) to the highly conserved domain of MCPs and with rabbit syphilitic serum. Antibody HC23 reacted with six
T. pallidum
proteins, including a 45-kDa protein that may correspond to Mcp2. This protein was present in the aqueous phase from
T. pallidum
cells that were solubilized with Triton X-114 and phase partitioned.
Human Antibody Response toHelicobacter pyloriLipopolysaccharide: Presence of an Immunodominant Epitope in the Polysaccharide Chain of Lipopolysaccharide
Authors: Yokota Shin-ichi , Amano Ken-ichi , Hayashi Shunji , Kubota Toru , Fujii Nobuhiro , Yokochi Takashi 
Published: December 2019

ABSTRACTWe have examined the antibody response toHelicobacter pylorilipopolysaccharides (LPS) in humans. We used sera from patients with gastroduodenal diseases and healthy adults infected or not infected withH. pylori. Data from the experiments for antibody binding to LPS suggested that the polysaccharide chains from manyH. pyloristrains showed high immunogenicity in humans. Sera from most (above 70%)H. pylori-infected individuals contained immunoglobulin G (IgG) antibodies against the polysaccharide region highly immunogenicH. pyloriLPS. The IgG titers of individual serum samples that reacted strongly with highly immunogenic LPS were quite similar (r2= 0.84 to 0.98). The results suggest wide distribution amongH. pyloristrains of a highly antigenic epitope in the polysaccharide moieties of their LPS. Also, the similarity in the titers of individual serum samples against highly immunogenic LPS points to the existence of epitopes sharing a common structural motif. However, some strains showed low antigenicity, even those with polysaccharide-carrying LPS. The dominant subclass of IgG that reacted with the highly immunogenic LPS was IgG2, which was preferentially raised against polysaccharide antigens. Recently, a structure that mimics that of the Lewis antigens was identified in the O-polysaccharide fraction ofH. pyloriLPS; however, no correlation between antigenicity of the polysaccharide chain in humans and the presence of Lewis antigens was found. The IgA and IgM titers againstH. pyloriLPS seemed to be mostly nonspecific and directed against lipid A. In a few cases, however, sera from individuals infected withH. pylorigave strong IgA and IgM titers against the highly immunogenic polysaccharide. In conclusion, the LPS of manyH. pyloristrains possess an antigenic epitope in their polysaccharide regions that is immunogenic in humans. However, our results show that the antigenic epitope is unlikely to be immunologically related to structures mimicking Lewis antigens.
Inhibition of Human Peripheral Blood Mononuclear Cell Proliferation byStreptococcus pyogenesCell Extract Is Associated with Arginine Deiminase Activity
Authors: Degnan B. A. , Palmer J. M. , Robson T. , Jones C. E. D. , Fischer M. , Glanville M. , Mellor G. D. , Diamond A. G. , Kehoe M. A. , Goodacre J. A. 
Published: December 2019

ABSTRACTStreptococcus pyogenes(group AStreptococcus) cell extracts (CE) have a remarkably powerful and dose-dependent inhibitory effect on antigen, superantigen, or mitogen-stimulated human peripheral blood mononuclear cell (PBMC) proliferation in vitro. Purification of the inhibitory component present inS. pyogenestype M5 (Manfredo strain) CE by anion-exchange chromatography followed by gel filtration chromatography showed that the inhibitor had an approximate native molecular mass of 100 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified inhibitory fractions followed by silver staining gave a single band with an approximate molecular mass of 47 kDa, indicating that the inhibitor is composed of two identical subunits. NH2-terminal sequencing of the protein revealed that it was identical to the previously characterized streptococcal acid glycoprotein (SAGP); this protein possesses between 31.5 and 39.0% amino acid identity with arginine deiminase (AD) fromMycoplasma hominis,Mycoplasma arginini,Pseudomonas putida, andPseudomonas aeruginosa. AD enzyme activity was present in unfractionated CE prepared from a range of streptococcal strains, and partially purified inhibitory fractions of Manfredo CE also had high levels of activity. The inhibitory effect of Manfredo CE was overcome by the addition ofl-arginine to proliferation assays in which human PBMC were stimulated with phytohemagglutinin. We conclude that SAGP, or its homolog, possesses AD activity and that the potent inhibition of proliferation of human T cells by streptococcal CE is due to activity of this enzyme.
Effect of Mild Acid Treatment on the Survival, Enteropathogenicity, and Protein Production in
Vibrio parahaemolyticus
Authors: Wong Hin-chung , Peng Po-Yen , Han Jun-Ming , Chang Chia-Yu , Lan Shang-Lun 
Published: December 2019

ABSTRACT

Vibrio parahaemolyticus
is an important food-borne enteropathogen that encounters various adverse conditions in its native environment or during infection. Effects of mild acid treatment on survival under stress conditions, enteropathogenicity, and protein production in this pathogen were investigated. Logarithmically grown cells, at pH 7.5 shifted to pH 5.0 for 30 min, were more resistant to subsequent acid challenge at pH 4.4. A two-phase adaptive procedure (pH 5.8 for 30 min; pH 5.0 for 30 min) was better than a single-phase procedure for enhancing the acid tolerance of this pathogen. The acid-adapted cells were cross-protected against the challenges of low salinity and thermal inactivation. One-dimensional polyacrylamide gel electrophoresis revealed that proteins with molecular masses of 6.4, 9.0, 13.6, 16.3, 18.9, 22.9, 24.4, 28.3, 33.9, 36.9, 41.2, 47.6, 58.1, 65.6, 80.5, 88.2, and 96.9 kDa were induced or significantly enhanced, while proteins of 25.3, 30.1, 30.7, and 91.7 kDa were significantly inhibited. Two-dimensional polyacrylamide gel electrophoresis revealed that 20 species of proteins were induced or significantly enhanced, while 26 species were inhibited. In assays conducted using the suckling mouse model, enteropathogenicity of the acid-adapted cells was significantly enhanced in terms of intestine/body weight ratio and in vivo recovery of infected cells.
Immunological and Molecular Characterization of Three Variant Subtype P1.14 Strains of
Neisseria meningitidis
Authors: Saunders Nancy B. , Brandt Brenda L. , Warren Richard L. , Hansen Brian D. , Zollinger Wendell D. 
Published: December 2019

ABSTRACT

Epidemic outbreaks of group B meningococcal disease exhibit a clonal nature consisting of a common serotype-subtype. Subtype-specific monoclonal antibodies (MAbs) directed toward two variable regions (VR1 and VR2) of the class 1 protein of
Neisseria meningitidis
are used in this classification scheme. A new MAb was developed to classify a nonsubtypeable (NST) strain of
N. meningitidis
, 7967. This MAb bound to both the NST strain and the prototype subtype P1.14 strain, S3446, by dot blot analysis. However, a MAb produced to the prototype P1.14 strain did not bind to strain 7967. Sixteen additional strains were further identified as P1.14 with the prototype MAb; of these, 15 strains bound both MAbs. Differences in the characteristics of binding of both antibodies to the three apparently diverse P1.14 strains were studied further by using outer membrane complex proteins, immobilized peptides, and soluble peptides. Deduced amino acid analysis suggested that both MAbs bind to VR2 and that single amino acid changes within VR2 (KM, NM, or KK) might explain the differences in binding characteristics. These results demonstrated that minor variations which exist within subtype variable regions may be clearly identified only by a combination of molecular and immunologic testing. The impact of subtype variation will become more evident as subtype-specific vaccines are developed and tested for efficacy.
Cloning of the Gene Encoding the 44-Kilodalton Antigen of the Agent of Human Granulocytic Ehrlichiosis and Characterization of the Humoral Response
Authors: Ijdo Jacob W. , Sun Wei , Zhang Yan , Magnarelli Louis A. , Fikrig Erol 
Published: December 2019

ABSTRACTAntibodies in the sera of patients with human granulocytic ehrlichiosis (HGE) commonly recognize a 44-kDa antigen. We cloned the gene encoding the 44-kDa protein of the agent of HGE (aoHGE) by probing an aoHGE lambda ZAP II genomic DNA expression library with sera from aoHGE-infected mice. The gene,hge-44, is part of a multigene family, with sequence similarity to theAnaplasma marginale msp-2genes. RNA-PCR studies confirmed thathge-44is expressed by aoHGE cultured in HL-60 cells and by aoHGE during murine infection. Recombinant HGE-44, expressed and purified as a glutathione transferase fusion protein, was used as the substrate in immunoblots to help diagnose HGE. Antibodies in eight sera from eight patients with HGE and in two sera from two aoHGE-infected mice bound recombinant HGE-44. Antibodies in the sera of healthy individuals or patients withEhrlichia chaffeensisorBorrelia burgdorferiinfection did not recognize HGE-44. We conclude thathge-44is a member of a multigene family and thathge-44is expressed and elicits specific antibodies during infection.
Human and Murine Immune Responses to a NovelLeishmania majorRecombinant Protein Encoded by Members of a Multicopy Gene Family
Authors: Webb John R. , Campos-Neto Antonio , Ovendale Pamela J. , Martin Tricia I. , Stromberg Erika J. , Badaro Roberto , Reed Steven G. 
Published: December 2019

ABSTRACTVaccination of BALB/c mice withLeishmania majorpromastigote culture filtrate proteins plusCorynebacterium parvumconfers resistance to infection withL. major. To define immunogenic components of this protein mixture, we used sera from vaccinated mice to screen anL. majoramastigote cDNA expression library. One of the immunoreactive clones thus obtained encoded a novel protein ofL. majorwith a molecular mass of 22.1 kDa. The predicted amino acid sequence of this clone exhibited significant homology to eukaryotic thiol-specific-antioxidant (TSA) proteins. Therefore, we have designated this proteinL. majorTSA protein. Southern blot hybridization analyses indicate that there are multiple copies of the TSA gene in all species ofLeishmaniaanalyzed. Northern blot analyses demonstrated that the TSA gene is constitutively expressed inL. majorpromastigotes and amastigotes. Recombinant TSA protein containing an amino-terminal six-histidine tag was expressed inEscherichia coliwith the pET17b system and was purified to homogeneity by affinity chromatography. Immunization of BALB/c mice with recombinant TSA protein resulted in the development of strong cellular immune responses and conferred protective immune responses against infection withL. majorwhen the protein was combined with interleukin 12. In addition, recombinant TSA protein elicited in vitro proliferative responses from peripheral blood mononuclear cells of human leishmaniasis patients and significant TSA protein-specific antibody titers were detected in sera of both cutaneous-leishmaniasis and visceral-leishmaniasis patients. Together, these data suggest that the TSA protein may be useful as a component of a subunit vaccine against leishmaniasis.
In Vivo Phase Variation of
Escherichia coli
Type 1 Fimbrial Genes in Women with Urinary Tract Infection
Authors: Lim Jean K. , Gunther Nereus W. , Zhao Hui , Johnson David E. , Keay Susan K. , Mobley Harry L. T. 
Published: December 2019

ABSTRACT

Type 1 fimbriae, expressed by most
Escherichia coli
strains, are thought to attach to human uroepithelium as an initial step in the pathogenesis of urinary tract infections (UTI). Numerous reports using both in vitro and murine models support this role for type 1 fimbriae in colonization. Unfortunately, only a limited number of studies have directly examined the expression of fimbriae in vivo. To determine whether type 1 fimbrial genes are transcribed during an acute UTI, we employed a modification of an established method. The orientation (ON or OFF) of the invertible promoter element, which drives transcription of type 1 fimbrial genes, was determined by PCR amplification using primers that flank the invertible element, followed by
Sna
BI digestion. The orientation of the type 1 fimbrial switch was determined under three experimental conditions. First,
E. coli
strains from different clinical sources (acute pyelonephritis patients, cystitis patients, and fecal controls) were tested under different in vitro culture conditions (agar versus broth; aerated versus static). The genes in the more-virulent strains (those causing acute pyelonephritis) demonstrated a resistance, in aerated broth, to switching from OFF to ON, while those in fecal strains readily switched from OFF to ON. Second, bladder and kidney tissue from CBA mice transurethrally inoculated with
E. coli
CFT073 (an established murine model of ascending UTI) was assayed. The switches directly amplified from infected bladder and kidney tissues were estimated to be 33 and 39% ON, respectively, by using a standard curve. Finally, bacteria present in urine samples collected from women with cystitis were tested for type 1 fimbria switch orientation. For all 11 cases, an average of only 4% of the switches in the bacteria in the urine were ON. In 7 of the 11 cases, we found that all of the visible type 1 fimbrial switches were in the OFF position (upper limit of detection of assay, 98% OFF). Strains recovered from these urine samples, however, were shown after culture in vitro to be capable of switching the fimbrial gene to the ON position and expressing mannose-sensitive hemagglutinin. The results from experimental infections and cases of cystitis in women suggest that type 1 fimbrial genes are transcribed both in the bladder and in the kidney. However, those bacteria found in the urine and not attached to the uroepithelium are not transcriptionally active for type 1 fimbrial genes.
At Least Four Percent of the
Salmonella typhimurium
Genome Is Required for Fatal Infection of Mice
Authors: Bowe Frances , Lipps Craig J. , Tsolis Renee M. , Groisman Eduardo , Heffron Fred , Kusters Johannes G. 
Published: December 2019

ABSTRACT

Salmonella typhimurium
infection of mice is an established model system for studying typhoid fever in humans. Using this model, we identified
S. typhimurium
genes which are absolutely required to cause fatal murine infection by testing independently derived transposon insertion mutants for loss of virulence in vivo. Of the 330 mutants tested intraperitoneally and the 197 mutants tested intragastrically, 12 mutants with 50% lethal doses greater than 1,000 times that of the parental strain were identified. These attenuated mutants were characterized by in vitro assays which correlate with known virulence functions. In addition, the corresponding transposon insertions were mapped within the
S. typhimurium
genome and the nucleotide sequence of the transposon-flanking DNA was obtained.
Salmonella
spp. and related bacteria were probed with flanking DNA for the presence of these genes. All 12 attenuated mutants had insertions in known genes, although the attenuating effects of only two of these were previously described. Furthermore, the proportion of attenuated mutants obtained in this study suggests that mutations in about 4% of the
Salmonella
genome lead to 1,000-fold or greater attenuation in the mouse typhoid model of infection. Most of these genes appear to be required during the early stages of a natural infection.
Inhibition of Binding of Malaria-Infected Erythrocytes by a Tetradecasaccharide Fraction from Chondroitin Sulfate A
Authors: Beeson James G. , Chai Wengang , Rogerson Stephen J. , Lawson Alexander M. , Brown Graham V. 
Published: December 2019

ABSTRACTAdherence of parasite-infected erythrocytes (IEs) to the microvascular endothelium of various organs, a process known as sequestration, is a feature ofPlasmodium falciparummalaria. This event is mediated by specific adhesive interactions between parasite proteins, expressed on the surface of IEs, and host molecules.P. falciparumIEs can bind to purified chondroitin sulfate A (CS-A), to the proteoglycan thrombomodulin through CS-A side chains, and to CS-A present on the surface of brain and lung endothelial cells and placental syncytiotrophoblasts. In order to identify structural characteristics of CS-A important for binding, oligosaccharide fragments ranging in size from 2 to 20 monosaccharide units were isolated from CS-A and CS-C, following controlled chondroitin lyase digestion, and used as competitive inhibitors of IE binding to immobilized ligands. Inhibition of binding to CS-A was highly dependent on molecular size: a CS-A tetradecasaccharide fraction was the minimum length able to almost completely inhibit binding. The effect was dose dependent and similar to that of the parent polysaccharide, and the same degree of inhibition was not found with the CS-C oligosaccharides. There was no effect on binding of IEs to other ligands, e.g., CD36 and intercellular adhesion molecule 1. Hexadeca- and octadecasaccharide fractions of CS-A were required for maximum inhibition of binding to thrombomodulin. Analyses of oligosaccharide fractions and polysaccharides by electrospray mass spectrometry and high-performance liquid chromatography suggest that the differences between the activities of CS-A and CS-C oligosaccharides can be attributed to differences in sulfate content and sulfation pattern and that iduronic acid is not involved in IE binding.