bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shiga Toxin-Producing
Escherichia coli
Can Impair T84 Cell Structure and Function without Inducing Attaching/Effacing Lesions
Authors: Li Zhe , Elliott Elizabeth , Payne Jacqueline , Isaacs Jacqui , Gunning Peter , O'loughlin Edward V. 
Published: December 2019

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) intimately adhere to epithelial cells producing cytoskeletal rearrangement with typical attaching and effacing lesions and altered epithelial barrier and transport function. Since EPEC and Shiga toxin-producing
E. coli
(STEC) share similar genes in the “locus for enterocyte effacement” (LEE) thought to cause these changes, it has been assumed that STEC shares similar pathogenic mechanisms with EPEC. The aims of this study were to compare the effects of EPEC and STEC on bacterial-epithelial interactions and to examine changes in epithelial function. T84 monolayers were infected with STEC O157:H7 (wild strain EDL 933 or non-toxin-producing strain 85/170), EPEC (strain E2348/69), or HB101 (nonpathogenic) and studied at various times after infection. EPEC bound more avidly than EDL 933, but both strains exhibited greater binding than HB101. Attaching and effacing lesions and severe disruption to the actin cytoskeleton were observed in EPEC by 3 h postinfection but not in EDL 933 or HB101 at any time point. EPEC and EDL 933 increased monolayer permeability to [
3
H]mannitol 5- to 10-fold. In contrast to EPEC, EDL 933 completely abolished secretagogue-stimulated anion secretion as assessed under voltage clamp conditions in Ussing chambers. Several other STEC strains induced changes similar to those of EDL 933. In conclusion, STEC impairs epithelial barrier function and ion transport without causing major disruption to the actin cytoskeleton. Pathogenic factors other than products of LEE may be operant in STEC.
Increased Interleukin-1 (IL-1) and Imbalance between IL-1 and IL-1 Receptor Antagonist during Acute Inflammation in Experimental Shigellosis
Authors: Arondel Josette , Singer Monique , Matsukawa Akihiro , Zychlinsky Arturo , Sansonetti Philippe J. 
Published: December 2019

ABSTRACTInfection by the enteric bacterial pathogenShigellaresults in intense mucosal inflammation and destruction of the colonic and rectal epithelium in infected humans. Initial bacterial translocation occurs through the follicle-associated epithelium. Previous experiments suggest that interleukin-1 (IL-1) is crucial to trigger inflammation, particularly in the follicular zones. During the first 4 hours of infection in a rabbit ligated-loop model of intestinal invasion, there are two salient characteristics: (i) a high concentration of IL-1α and IL-1β, both in infected Peyer's patch tissue and in the corresponding efferent mesenteric blood, and (ii) a very low level of expression of IL-1 receptor antagonist (IL-1ra). These may reflect a combination of regulation of expression and secretion of IL-1α, IL-1β, and IL-1ra by both resident and recruited phagocytes and the induction of mononuclear phagocyte apoptosis byShigella. This low IL-1ra/IL-1 ratio likely accounts for the rapid, uncontrolled inflammation characteristic of shigellosis.
Enterococcus faecalisBearing Aggregation Substance Is Resistant to Killing by Human Neutrophils despite Phagocytosis and Neutrophil Activation
Authors: Rakita Robert M. , Vanek Natalie N. , Jacques-Palaz Karen , Mee Mee , Mariscalco M. Michele , Dunny Gary M. , Snuggs Mark , Van Winkle W. Barry , Simon Scott I. 
Published: December 2019

ABSTRACTEnterococcus faecalisaggregation substance (AS) mediates efficient bacterium-bacterium contact to facilitate plasmid exchange as part of a bacterial sex pheromone system. We have previously determined that AS promotes direct, opsonin-independent binding ofE. faecalisto human neutrophils (PMNs) via complement receptor type 3 and other receptors on the PMN surface. We have now examined the functional consequences of this bacterium-host cell interaction. AS-bearingE. faecaliswas phagocytosed and internalized by PMNs, as determined by deconvolution fluorescence microscopy. However, these bacteria were not killed by PMNs, and internalized bacteria excluded propidium iodide, indicating intact bacterial membranes. Resistance to killing occurred despite activation of PMNs, as indicated by an increase in both functional and total surface Mac-1 expression, shedding ofl-selectin, and an increase in PMN extracellular superoxide and phagosomal oxidant production. Deconvolution fluorescence microscopy also revealed that phagosomes containing AS-bearing bacteria were markedly larger than phagosomes containing opsonizedE. faecalis, suggesting that some modification of phagosomal maturation may be involved in AS-induced resistance to killing. PMN phagosomal pH was significantly higher after ingestion of nonopsonized AS-bearingE. faecalisthan after that of opsonized bacteria. The novel ability of AS to promote intracellular survival ofE. faecalisinside PMNs suggests that AS may be a virulence factor used by strains ofE. faecalis.
Phenotypic Switching in
Cryptococcus neoformans
Results in Changes in Cellular Morphology and Glucuronoxylomannan Structure
Authors: Fries Bettina C. , Goldman David L. , Cherniak Robert , Ju Rujin , Casadevall Arturo 
Published: December 2019

ABSTRACT

Cryptococcus neoformans
strains exhibit variability in their capsular polysaccharide, cell morphology, karyotype, and virulence, but the relationship between these variables is poorly understood. A hypovirulent
C. neoformans
24067A isolate, which usually produces smooth (SM) colony types, was found to undergo phenotypic switching and to produce wrinkled (WR) and pseudohyphal (PH) colony types at frequencies of approximately 10
−4
to 10
−5
when plated on Sabouraud agar. Cells from these colony types had large polysaccharide capsules and PH morphology, respectively. Scanning electron microscopy showed that different colony types were the result of altered cellular packing in the colony. Phenotypic switching was associated with quantitative and qualitative changes in capsular polysaccharide. Specifically, the glucuronoxylomannan (GXM) of the WR polysaccharide differed in the proportion of structural reporter groups and in increased xylose residue content linked at the 4 to 0 position. The relative virulence of the colony types was WR > PH > SM, as measured by CFU in rat lungs after intratracheal infection. Karyotype instability was observed in strain 24067A and involved primarily two chromosomes. Colonies with an alternative colony type exhibited more karyotype changes, which did not revert to the original karyotype in reverted colonies. In summary, this study revealed that phenotypic switching in
C. neoformans
(i) can produce WR colonies consisting of cells with either large capsule or PH morphology, (ii) is associated with production of structurally different GXM, (iii) is commonly associated with karyotype changes, (iv) can produce cells of PH morphology, and (v) can increase the virulence of a strain. Hence, phenotypic switching is an adaptive mechanism linked to virulence that can generate cell types with very different biological characteristics.
Chlamydia trachomatis(Mouse Pneumonitis Strain) Induces Cardiovascular Pathology following Respiratory Tract Infection
Authors: Fan Yijun , Wang Shuhe , Yang Xi 
Published: December 2019

ABSTRACTChlamydia, especiallyChlamydia pneumoniae, infection is closely associated with human cardiovascular diseases. Thus far, however, few experimental studies have been carried out to investigate whether naturalC. trachomatisinfection can induce cardiovascular pathological changes. In this article, we report that pulmonary infection withC. trachomatismouse pneumonitis strain (MoPn) can induce myocardial and perivascular inflammation and fibrosis in C57BL/6 mice. The pulmonary MoPn infection appeared to be disseminated systemically, because chlamydial antigens were readily detectable in multiple organs including the cardiovascular tissues. In addition, gamma interferon gene knockout mice with a C57BL/6 genetic background showed significant endocarditis and pancarditis characterized by vegetation in aortic valves, interstitial and pericardial inflammatory cellular infiltration, and growth of the organisms in the heart following respiratory tract MoPn infection. The results indicate thatC. trachomatiscan induce cardiovascular diseases following respiratory tract infection and suggest that murine MoPn respiratory tract infection may be a useful experimental model for investigating cardiovascular diseases caused by chlamydial infection.
Natural Immunity toAscaris lumbricoidesAssociated with Immunoglobulin E Antibody to ABA-1 Allergen and Inflammation Indicators in Children
Authors: McSharry Charles , Xia Yu , Holland Celia V. , Kennedy Malcolm W. 
Published: December 2019

ABSTRACTChildren putatively immune to the large roundwormAscaris lumbricoideswere identified in an area of Nigeria where infection is hyperendemic. Immunity was associated with higher levels of serum ferritin, C-reactive protein, and eosinophil cationic protein, indicating ongoing acute phase or inflammatory processes. In contrast, children who were susceptible to the infection had little serological evidence of inflammation despite their high parasite burdens. Immunoglobulin G (IgG) antibody activity in all subclasses was present in high titer in most children but appeared to have no protective function. Despite exceptionally high total IgE levels, there was no evidence that atopic responses to local common allergens was associated with natural immunity toAscaris. Among those individuals who produced IgG antibody to recombinant ABA-1 allergen ofAscaris, the naturally immune group had significantly more IgE antibody to the allergen than did those susceptible to the infection. IgE antibody responses in conjunction with innate inflammatory processes therefore appear to associate with natural immunity to ascariasis.
Deamidation of Cdc42 and Rac by
Escherichia coli
Cytotoxic Necrotizing Factor 1: Activation of c-Jun N-Terminal Kinase in HeLa Cells
Authors: Lerm M. , Selzer J. , Hoffmeyer A. , Rapp U. R. , Aktories K. , Schmidt G. 
Published: December 2019

ABSTRACT

Recently,
Escherichia coli
cytotoxic necrotizing factor 1 (CNF1) was shown to activate the low-molecular-mass GTPase RhoA by deamidation of Gln63, thereby inhibiting intrinsic and GTPase-activating protein (GAP)-stimulated GTPase activities (G. Schmidt, P. Sehr, M. Wilm, J. Selzer, M. Mann, and K. Aktories, Nature 387:725–729, 1997; G. Flatau, E. Lemichez, M. Gauthier, P. Chardin, S. Paris, C. Fiorentini, and P. Boquet, Nature 387:729–733, 1997). Here we report that in addition to RhoA, Cdc42 and Rac also are targets for CNF1 in vitro and in intact cells. Treatment of HeLa cells with CNF1 induced a transient formation of microspikes and formation of membrane ruffles. CNF1 caused a transient 10- to 50-fold increase in the activity of the c-Jun N-terminal kinase. Tryptic peptides of Cdc42 obtained from CNF1-treated cells by immunoprecipitation exhibited an increase in mass of 1 Da compared to control peptides, indicating the deamidation of glutamine 61 by the toxin. The same increase in mass was observed with the respective peptides obtained from CNF1-modified recombinant Cdc42 and Rac1. Modification of recombinant Cdc42 and Rac1 by CNF1 inhibited intrinsic and GAP-stimulated GTPase activities and retarded binding of 2′(3′)- O-(N -methylanthraniloyl)GDP. The data suggest that recombinant as well as cellular Cdc42 and Rac are substrates for CNF1.
Receptor-Dependent Immune Responses in Pigs after Oral Immunization with F4 Fimbriae
Authors: Van den Broeck Wim , Cox Eric , Goddeeris Bruno M. 
Published: December 2019

ABSTRACT

F4 receptor-positive (F4R
+
) and F4 receptor-negative (F4R
−
) pigs were orally vaccinated with purified F4 fimbriae of enterotoxigenic
Escherichia coli
(ETEC). Serum immunoglobulin G (IgG) and IgA responses were readily detected in F4R
+
animals, whereas immune responses were not detected in F4R
−
animals. Even after a subsequent oral infection with virulent F4
+
ETEC and a booster immunization with F4, the F4R
−
animals remained F4 seronegative whereas the unvaccinated F4R
+
pigs exhibited clear IgA and IgG responses. These results clearly demonstrate that F4Rs are a prerequisite for an immune response following oral immunization. Furthermore, indications that oral F4 vaccination can induce mucosal protection were obtained, since the experimental ETEC infection did not induce a systemic booster response or fecal ETEC excretion in orally vaccinated F4R
+
pigs, in contrast to the clear immune response and ETEC excretion of unvaccinated F4R
+
animals. F4-specific IgA antibodies could be found in the feces of the vaccinated F4R
+
pigs. They are secreted at the intestinal mucosal surface and appear to prevent ETEC infection. The F4R-dependent induction of a mucosal immune response can be used as a model to better understand mucosal immunization and mucosal immune responses and can contribute to the development of oral vaccines in veterinary as well as in human medicine.
Serum Antitoxin Antibodies Mediate Systemic and Mucosal Protection from
Clostridium difficile
Disease in Hamsters
Authors: Giannasca Paul J. , Zhang Zhen-xi , Lei Wen-de , Boden James A. , Giel Mary Ann , Monath Thomas P. , Thomas William D. 
Published: December 2019

ABSTRACT

Clostridium difficile
is the bacterial pathogen identified as the cause of pseudomembranous colitis and is principally responsible for nosocomial antibiotic-associated diarrhea and colitis. The pathologic findings associated with this infection are believed to be caused by two large (∼300-kDa) exotoxins, toxins A and B. Because of the mucosal nature of this infection, vaccination strategies aimed at providing prophylactic or therapeutic immune protection have included immunization by mucosal routes. Using the hamster model of
C. difficile
infection, we examined the protective efficacy of inactivated toxin (toxoid) vaccine formulations prepared as either culture filtrate or partially purified toxoid. We compared combination parenteral and mucosal vaccination regimens involving intranasal, intragastric, or rectal routes of immunization and found that rectal immunization in conjunction with intramuscular (i.m.) vaccination provided full protection of hamsters from death and diarrhea while the other mucosal routes did not. Protection was associated with high levels of toxin-neutralizing antibodies in serum. The requirement for adjuvants for protection was assessed by using sequential i.m. and rectal or i.m. vaccination regimens. Unexpectedly, i.m. immunization without adjuvant conferred the highest protection from death and diarrhea; this regimen elicited the highest serum anti-toxin B titers as well as toxin B neutralizing titers. Passive transfer of mouse antitoxin antibodies protected hamsters in a dose-dependent manner, demonstrating the principal role of circulating antitoxin antibodies in immunity from this toxin-mediated mucosal disease. These results suggest that prophylactic parenteral vaccination or intravenous immunotherapy could provide protection from
C. difficile
disease in humans.
TheURA5Gene Is Necessary forHistoplasma capsulatumGrowth during Infection of Mouse and Human Cells
Authors: Retallack Diane M. , Heinecke Elizabeth L. , Gibbons Reta , Deepe George S. , Woods Jon P. 
Published: December 2019

ABSTRACTTheHistoplasma capsulatum URA5gene, which has recently been cloned and disrupted by allelic replacement, encodes orotidine-5′-monophosphate pyrophosphorylase. Inactivation ofURA5by either targeted or UV mutagenesis results in disruption of the pyrimidine biosynthetic pathway and uracil auxotrophy. We examined the effect of uracil auxotrophy due to aura5mutation onH. capsulatumvirulence in both cell culture and whole-animal models. Uracil auxotrophs of twoH. capsulatumrestriction fragment length polymorphism classes were found to be avirulent in cultured murine and human cells, as well as in mice. Moreover, virulence could be restored either by supplying a functionalURA5gene in trans or by supplying exogenous uracil during infection in vitro. These experiments demonstrate that the pyrimidine biosynthetic pathway is essential forH. capsulatumgrowth and virulence.
Protective Immunization with a Novel Membrane Protein ofPlasmodium yoelii-Infected Erythrocytes
Authors: Burns James M. , Adeeku Eric K. , Dunn Patricia D. 
Published: December 2019

ABSTRACTImmunization with a particulate fraction of blood-stage antigens was shown previously to protect mice againstPlasmodium yoeliimalaria. To identify antigens inducing the protective response, sera from immunized mice were used to screen aP. yoeliicDNA expression library. Sequence analysis of one 2.6-kb cDNA clone indicated that the identified gene,pypag-1, encoded a novel plasmodial antigen. Two nonoverlapping regions ofpypag-1were expressed inEscherichia coli. The first recombinant antigen, pAg-1N, contained the N-terminal 337 residues, which included a putative transmembrane domain and a region relatively rich in tryptophan residues. The second recombinant antigen, pAg-1C, contained the remaining C-terminal 211 residues, which included 31 copies of a 5-amino-acid degenerative repeat. Immunoblot studies using rabbit antiserum raised against recombinant pAg-1N showed that the native pypAg-1 protein migrated at approximately 98 kDa, considerably slower than its predicted molecular mass of 66 kDa. Immunofluorescence studies localized the expression of the native pypAg-1 protein both to the cytoplasm and at the surface ofP. yoelii-infected erythrocytes. Immunization with either pAg-1N or pAg-1C induced a four- to sevenfold reduction inP. yoeliiblood-stage parasitemia. As such, pypAg-1 appears to contain at least two distinct protective epitopes. To our knowledge, this is the first characterization of a protective antigen ofP. yoeliithat is associated with the erythrocyte membrane.
Involvement of Mitogen-Activated Protein Kinase Pathways in Interleukin-8 Production by Human Monocytes and Polymorphonuclear Cells Stimulated with Lipopolysaccharide orMycoplasma fermentansMembrane Lipoproteins
Authors: Marie Christelle , Roman-Roman Sergio , Rawadi Georges 
Published: December 2019

ABSTRACTInterleukin-8 (IL-8) is a chemokine that belongs to the α-chemokine or CXC subfamily and is produced by a wide variety of human cells, including monocytes and polymorphonuclear cells (PMN). IL-8 is secreted in response to inflammatory stimuli, notably bacterial products such as lipopolysaccharide (LPS), but little is known about the mechanisms by which these agents mediate IL-8 induction. In this report, we show thatMycoplasma fermentanslipid-associated membrane proteins (LAMPf) induce the production of high levels of IL-8 by THP-1 (human monocyte) cells and PMN at the same extent as LPS. It was previously demonstrated that stimulation of monocytic cells with either LPS or LAMPf led to a series of common downstream signaling events, including the activation of protein tyrosine kinase and of mitogen-activated protein kinase cascades. By using PD-98059 and SB203580, two potent and selective inhibitors of MEK1 (a kinase upstream of ERK1/2) and p38, respectively, we have demonstrated that both ERK1/2 and p38 cascades play a key role in the production of IL-8 by monocytes and PMN stimulated with bacterial fractions.
Differential Posttranslational Processing Confers Intraspecies Variation of a Major Surface Lipoprotein and a Macrophage-Activating Lipopeptide ofMycoplasma fermentans
Authors: Calcutt Michael J. , Kim Mary F. , Karpas Arthur B. , Mühlradt Peter F. , Wise Kim S. 
Published: December 2019

ABSTRACTThemalpgene ofMycoplasma fermentansis shown to occur in single copy but to encode two discrete translated forms of lipid-modified surface protein that can be differentially expressed on isolates within this species: MALP-2, a 14-amino-acid (2-kDa) lipopeptide with potent macrophage-stimulatory activity (P. F. Mühlradt, M. Kiess, H. Meyer, R. Süssmuth, and G. Jung, J. Exp. Med. 185:1951–1958, 1997), and MALP-404, an abundant, full-length (404-amino-acid) surface lipoprotein of 41 kDa, previously designated P41 (K. S. Wise, M. F. Kim, P. M. Theiss, and S.-C. Lo, Infect. Immun. 61:3327–3333, 1993). The sequences, transcripts, and translation products ofmalpwere compared between clonal isolates of strains PG18 (known to express P41) and II-29/1 (known to express high levels of MALP-2). Despite conservedmalpDNA sequences containing full-length open reading frames and expression of full-length monocistronic transcripts in both isolates, Western blotting using a monoclonal antibody (MAb) to the N-terminal MALP-2 peptide revealed marked differences in the protein products expressed. Whereas PG18 expressed abundant MALP-404 with detectable MALP-2, II-29/1 revealed no MALP-404 even in samples containing a large comparative excess of MALP-2. Colony immunoblots with the MAb showed uniform surface expression of MALP-2 in II-29/1 populations. A second MAb to an epitope of MALP-404 outside the MALP-2 sequence predictably failed to stain II-29/1 colonies but uniformly stained PG18 populations. Collectively, these results provide evidence for novel posttranscriptional (probably posttranslational) processing pathways leading to differential intraspecies expression of a major lipoprotein, and a potent macrophage-activating lipopeptide, on the surface ofM. fermentans. In the course of this study, a striking conserved motif (consensus, TD-G--DDKSFNQSAWE--), designated SLA, was identified in MALP-404; this motif is also distributed among selected lipoproteins and species from diverse bacterial genera, includingBacillus,Borrelia,Listeria,Mycoplasma, andTreponema. In addition,malpwas shown to flank a chromosomal polymorphism. In eight isolates ofM. fermentansexamined,malpoccurred upstream of an operon encoding the phase-variable P78 ABC transporter; but, in three of these isolates, a newly discovered insertion sequence, IS1630(of the IS30class), was located between these genes.
Strategy for Cross-Protection amongShigella flexneriSerotypes
Authors: Noriega Fernando R. , Liao Fang Ming , Maneval David R. , Ren Shuxun , Formal Samuel B. , Levine Myron M. 
Published: December 2019

ABSTRACTBased upon the lipopolysaccharide (LPS) structure and antigenicity ofShigellagroup B, a strategy for broad cross-protection against 14Shigella flexneriserotypes was designed. This strategy involves the use of twoS. flexneriserotypes (2a and 3a), which together bear the all of the major antigenic group factors of this group. The novel attenuated strains used in these studies wereS. flexneri2a strain CVD 1207 (ΔguaB-A ΔvirG Δset1 Δsen) andS. flexneri3a strain CVD 1211 (ΔguaB-A ΔvirG Δsen). Guinea pigs were immunized with an equal mixture of these strains and later challenged (Sereny test) with a wild-typeS. flexneriserotype 1a, 1b, 2b, 4b, 5b, Y, or 6 strain of demonstrated virulence in the same model. Guinea pigs that were immunized with these two vaccine strains produced serum and mucosal antibodies that cross-reacted with all theS. flexneriserotypes tested (except ofS. flexneriserotype 6) as assessed by enzyme-linked immunosorbent assay, immunoblotting, and slide agglutination. Furthermore, the combination vaccine conferred significant protection against challenge withS. flexneriserotypes 1b, 2b, 5b, and Y but not with serotypes 1a, 4b, or (as predicted) 6.