bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deletion of the Gene Encoding p60 inListeria monocytogenesLeads to Abnormal Cell Division and Loss of Actin-Based Motility
Authors: Pilgrim Sabine , Kolb-Mäurer Annette , Gentschev Ivaylo , Goebel Werner , Kuhn Michael 
Published: May 2003

ABSTRACTProtein p60 encoded by theiapgene is regarded as an essential gene product ofListeria monocytogenes. Here we report, however, the successful construction of a viableiapdeletion mutant ofL. monocytogenesEGD. The mutant, which produces no p60, shows abnormal septum formation and tends to form short filaments and hooked forms during logarithmic growth. These abnormal bacterial cells break into almost normal sized single bacteria in the late-stationary-growth phase. Theiapmutant is strongly attenuated in a mouse model after intravenous injection, demonstrating the importance of p60 during infection, and the invasiveness of the Δiapmutant for 3T6 fibroblasts and Caco-2 epithelial cells is slightly reduced. Upon uptake by epithelial cells and macrophages, theiapmutant escapes from the phagosome into the cytosol with the same efficiency as the wild-type strain, and the mutant bacteria also grow intracellularly at a rate similar to that of the wild-type strain. Intracellular movement and cell-to-cell spread are drastically reduced in various cell lines, since theiap-negative bacteria fail to induce the formation of actin tails. However, the bacteria are covered with actin filaments. Most intracellular bacteria show a nonpolar and uneven distribution of ActA around the cell, in contrast to that for the wild-type strain, where ActA is concentrated at the old pole. In aniap+revertant strain that produces wild-type levels of p60, intracellular movement, cell-to-cell spread, and polar distribution of ActA are fully restored. In vitro analysis of ActA distribution on the filaments of the Δiapstrain shows that the loss of bacterial septum formation leads to ActA accumulation at the presumed division sites. In the light of data presented here and elswhere, we propose to renameiap(invasion-associated protein)cwhA(cell wall hydrolase A).
Genetic Diversity and Antigenic Polymorphism in
Plasmodium falciparum
: Extensive Serological Cross-Reactivity between Allelic Variants of Merozoite Surface Protein 2
Authors: Franks Simon , Baton Luke , Tetteh Kevin , Tongren Eric , Dewin David , Akanmori Bartholomew D. , Koram Kojo A. , Ranford-Cartwright Lisa , Riley Eleanor M. 
Published: May 2003

ABSTRACT

Diversity in the surface antigens of malaria parasites is generally assumed to be a mechanism for immune evasion, but there is little direct evidence that this leads to evasion of protective immunity. Here we show that alleles of the highly polymorphic merozoite surface protein 2 (MSP-2) can be grouped (within the known dimorphic families) into distinct serogroups; variants within a serogroup show extensive serological cross-reactivity. Cross-reactive epitopes are immunodominant, and responses to them may be boosted at the expense of responses to novel epitopes (original antigenic sin). The data imply that immune selection explains only some of the diversity in the
msp-2
gene and that MSP-2 vaccines may need to include only a subset of the known variants in order to induce pan-reactive antibodies.
Helicobacter pylori
Activates Toll-Like Receptor 4 Expression in Gastrointestinal Epithelial Cells
Authors: Su Bin , Ceponis Peter J. M. , Lebel Sylvie , Huynh Hien , Sherman Philip M. 
Published: May 2003

ABSTRACT

Helicobacter pylori
activates the transcription factor NF-κB, leading to proinflammatory cytokine production by gastric epithelial cells. However, the receptors for the initial bacterial interaction with host cells which activate downstream signaling events have not been completely defined. Recently, it has been shown that microbial components activate Toll-like receptors (TLRs), thereby leading to AP-1- and NF-κB-dependent transcription and resulting in the production of proinflammatory cytokines. The aim of this study was to determine whether
H. pylori
activates TLR4. Reverse transcription-PCR showed that both type I and type II
H. pylori
clinical isolates induced TLR4 mRNA expression in AGS cells compared with that by uninfected controls.
H. pylori
upregulated TLR4 protein expression in two gastric epithelial cell lines (AGS and MKN45) and one intestinal epithelial cell line (T84). Monoclonal TLR4 antibody inhibited lipopolysaccharide-induced interleukin-8 secretion from THP-1 macrophages but not from gastric epithelial cells infected with
H. pylori
.
H. pylori
demonstrated increased adherence to CHO TLR4-transfected cells compared with that to both CHO TLR2-transfected and nontransfected CHO cells (
P
< 0.01). These results indicate that
H. pylori
activates TLR4 expression in epithelial cells and that TLR4 can serve as a receptor for
H. pylori
binding.
Gamma Interferon Augments the Intracellular Pathway for Lipopolysaccharide (LPS) Recognition in Human Intestinal Epithelial Cells through Coordinated Up-Regulation of LPS Uptake and Expression of the Intracellular Toll-Like Receptor 4-MD-2 Complex
Authors: Suzuki Manabu , Hisamatsu Tadakazu , Podolsky Daniel K. 
Published: May 2003

ABSTRACTAlthough some intestinal epithelial cell lines are known to respond to lipopolysaccharide (LPS), understanding of the relationship between LPS responsiveness and the expression of LPS receptors or factors regulating LPS responsiveness of intestinal epithelial cell lines is incomplete. In this study, we demonstrate that commonly studied human intestinal epithelial cell lines can be classified into at least three different types on the basis of LPS responsiveness, Toll-like receptor-4 (TLR4) expression, and the effects of gamma interferon (IFN-γ) on LPS responsiveness. The first phenotype, which includes the HCT-116 and Caco-2 cell lines, is characterized by relative hyporesponsiveness to LPS and diminished expression of TLR4 protein. In these cells, IFN-γ does not induce LPS responsiveness. The second phenotype, which includes cell line SW480, exhibits a highly LPS-responsive phenotype and surface expression of TLR4 protein even in unprimed conditions. These lines are functionally similar to cells of monocytic lineage. In the third phenotype, which includes the HT-29 and Colo205 cell lines, TLR4 protein is largely present in the cytoplasmic fraction and the cells are hyporesponsive to LPS in an unprimed condition. However, priming of these cells with IFN-γ can induce LPS responsiveness through augmentation of LPS uptake and expression of MD-2 mRNA and intracellular TLR4 proteins. Finally, these findings suggest that the Th1 cytokine IFN-γ modulates LPS responsiveness through several mechanisms in intestinal epithelial cells and that these cells may comprise different subpopulations with distinct roles in innate immune responses.
The
rovA
Mutant of
Yersinia enterocolitica
Displays Differential Degrees of Virulence Depending on the Route of Infection
Authors: Dube Peter H. , Handley Scott A. , Revell Paula A. , Miller Virginia L. 
Published: May 2003

ABSTRACT

Yersinia enterocolitica
is an invasive enteric pathogen that causes significant inflammatory disease. Recently, we identified and characterized a global regulator of virulence (
rovA
). When mice are infected orally with the
rovA
mutant they are attenuated by 50% lethal dose (LD
50
) analysis and have altered kinetics of infection. Most significantly, mice orally infected with the
rovA
mutant have greatly reduced inflammation in the Peyer's patches compared to those infected with wild-type
Y. enterocolitica.
However, we present data here indicating that when the
rovA
mutant bacteria are delivered intraperitoneally (i.p.), they are significantly more virulent than when delivered orally. The i.p. LD
50
for the
rovA
mutant is only 10-fold higher than that of the wild-type
Y. enterocolitica
, and there are significant inflammatory responses to the
rovA
mutant that are evident in the liver and spleen. Altogether, these data suggest that the RovA regulon may be required for the early events of the infection that occur in the Peyer's patches. Furthermore, these data suggest that the RovA regulon may be dispensable for
Y. enterocolitica
systemic disease and inflammatory responses if the Peyer's patches are bypassed.
CD40 Contributes to Lethality in Acute Sepsis: In Vivo Role for CD40 in Innate Immunity
Authors: Gold Jeffrey A. , Parsey Merdad , Hoshino Yoshihiko , Hoshino Satomi , Nolan Anna , Yee Herman , Tse Doris B. , Weiden Michael D. 
Published: May 2003

ABSTRACTSepsis induces an early inflammatory cascade initiated by the innate immune response. This often results in the development of multisystem organ failure. We examined the role of CD40, a costimulatory molecule that is integral in adaptive immunity, by using a murine model of polymicrobial sepsis. CD40 knockout (KO) mice had delayed death and improved survival after cecal ligation and puncture (CLP). In addition, they had less remote organ injury as manifested by reduced pulmonary capillary leakage. The improvements in survival and remote organ dysfunction in CD40 KO mice were associated with reduced interleukin-6 (IL-6) and IL-10 levels in serum and bronchoalveolar lavage fluid compared to the levels in wild-type (WT) controls. Furthermore, in contrast to WT mice, CD40 KO mice had no induction of the Th1 cytokines IL-12 and gamma interferon in serum or lungs after CLP. The alterations in cytokine production in CD40 KO mice were associated with similar changes in transcription factor activity. After CLP, CD40 KO mice had attenuated activation of nuclear factor κB and signal transducer and activator of transcription 3 in both the lung and the liver. Finally, WT mice had increased expression of CD40 on their alveolar macrophages. These data highlight the importance of CD40 activation in the innate immune response during polymicrobial sepsis and the subsequent development of remote organ dysfunction.
pH-Regulated Gene Expression of the Gastric PathogenHelicobacter pylori
Authors: Merrell D. Scott , Goodrich Maria L. , Otto Glen , Tompkins Lucy S. , Falkow Stanley 
Published: May 2003

ABSTRACTColonization by the gastric pathogenHelicobacter pylorihas been shown to be intricately linked to the development of gastritis, ulcers, and gastric malignancy. Little is known about mechanisms employed by the bacterium that help it adapt to the hostile environment of the human stomach. In an effort to extend our knowledge of these mechanisms, we utilized spotted-DNA microarrays to characterize the response ofH. pylorito low pH. Expression of approximately 7% of the bacterial genome was reproducibly altered by shift to low pH. Analysis of the differentially expressed genes led to the discovery that acid exposure leads to profound changes in motility ofH. pylori, as a larger percentage of acid-exposed bacterial cells displayed motility and moved at significantly higher speeds. In contrast to previous publications, we found that expression of the bacterial virulence genecagAwas strongly repressed by acid exposure. Furthermore, this transcriptional repression was reflected at the level of protein accumulation in theH. pyloricell.
Drosophila melanogaster
Is a Genetically Tractable Model Host for
Mycobacterium marinum
Authors: Dionne Marc S. , Ghori Nafisa , Schneider David S. 
Published: May 2003

ABSTRACT

Mycobacterium marinum
is a pathogenic mycobacterial species that is closely related to
Mycobacterium tuberculosis
and causes tuberculosis-like disease in fish and frogs. We infected the fruit fly
Drosophila melanogaster
with
M. marinum
. This bacterium caused a lethal infection in the fly, with a 50% lethal dose (LD
50
) of 5 CFU. Death was accompanied by widespread tissue damage.
M. marinum
initially proliferated inside the phagocytes of the fly; later in infection, bacteria were found both inside and outside host cells. Intracellular
M. marinum
blocked vacuolar acidification and failed to colocalize with dead
Escherichia coli
, similar to infections of mouse macrophages.
M. marinum
lacking the
mag24
gene were less virulent, as determined both by LD
50
and by death kinetics. Finally, in contrast to all other bacteria examined, mycobacteria failed to elicit the production of antimicrobial peptides in
Drosophila
. We believe that this system should be a useful genetically tractable model for mycobacterial infection.
Catalases of
Aspergillus fumigatus
Authors: Paris Sophie , Wysong Deborah , Debeaupuis Jean-Paul , Shibuya Kazutoshi , Philippe Bruno , Diamond Richard D. , Latgé Jean-Paul 
Published: May 2003

ABSTRACT

Upon infection of a host, the pathogenic fungus
Aspergillus fumigatus
is attacked by the reactive oxygen species produced by phagocytic cells. Detoxification of hydrogen peroxide by catalases was proposed as a way to overcome this host response.
A. fumigatus
produces three active catalases; one is produced by conidia, and two are produced by mycelia. The mycelial catalase Cat1p was studied previously. Here we characterized the two other catalases, their genes, and the phenotypes of gene-disrupted mutants. CatAp, a spore-specific monofunctional catalase, is resistant to heat, metal ions, and detergent. This enzyme is a dimeric protein with 84.5-kDa subunits. The 749-amino-acid polypeptide exhibits high levels of similarity to the
Aspergillus nidulans
CatA catalase and to bacterial catalase HPII of
Escherichia coli
. In spite of increased sensitivity to H
2
O
2
, killing of Δ
catA
conidia by alveolar macrophages and virulence in animals were similar to the killing of conidia by alveolar macrophages and virulence in animals observed for the wild type. In contrast to the Cat1p and CatAp catalases, the mycelial Cat2p enzyme is a bifunctional catalase-peroxidase and is sensitive to heat, metal ions, and detergent. This enzyme, an 82-kDa monomer, is homologous to catalase-peroxidases of several fungi and bacteria. Surprisingly, mycelium of the double Δ
cat1
Δ
cat2
mutant with no catalase activity exhibited only slightly increased sensitivity to H
2
O
2
and was as sensitive to killing by polymorphonuclear neutrophils as mycelium of the wild-type strain. However, this mutant exhibited delayed infection in the rat model of aspergillosis compared to infection by the wild-type strain. These results indicate that conidial catalase is not a virulence factor and that mycelial catalases transiently protect the fungus from the host.
Interleukin-12 p40 Secretion by Cutaneous CD11c+and F4/80+Cells Is a Major Feature of the Innate Immune Response in Mice That Develop Th1-Mediated Protective Immunity toSchistosomamansoni
Authors: Hogg Karen G. , Kumkate Supeecha , Anderson Sonia , Mountford Adrian P. 
Published: May 2003

ABSTRACTRadiation-attenuated (RA) schistosome larvae are potent stimulators of innate immune responses at the skin site of exposure (pinna) that are likely to be important factors in the development of Th1-mediated protective immunity. In addition to causing an influx of neutrophils, macrophages, and dendritic cells (DCs) into the dermis, RA larvae induced a cascade of chemokine and cytokine secretion following in vitro culture of pinna biopsy samples. While macrophage inflammatory protein 1α and interleukin-1β (IL-1β) were produced transiently within the first few days, the Th1-promoting cytokines IL-12 and IL-18 were secreted at high levels until at least day 14. Assay of C3H/HeJ mice confirmed that IL-12 secretion was not due to lipopolysaccharide contaminants binding Toll-like receptor 4. Significantly, IL-12 p40 secretion was sustained in pinnae from vaccinated mice but not in those from nonprotected infected mice. In contrast, IL-10 was produced from both vaccinated and infected mice. This cytokine regulates IL-12-associated dermal inflammation, since in vaccinated IL-10−/−mice, pinna thickness was greatly increased concurrent with elevated levels of IL-12 p40. A significant number of IL-12 p40+cells were detected as emigrants from in vitro-cultured pinnae, and most were within a population of rare large granular cells that were Ia+, consistent with their being antigen-presenting cells. Labeling of IL-12+cells for CD11c, CD205, CD8α, CD11b, and F4/80 indicated that the majority were myeloid DCs, although a proportion were CD11c−F4/80+, suggesting that macrophages were an additional source of IL-12 in the skin.
Helicobacter-Induced Chronic Active Lymphoid Aggregates Have Characteristics of Tertiary Lymphoid Tissue
Authors: Shomer Nirah H. , Fox James G. , Juedes Amy E. , Ruddle Nancy H. 
Published: May 2003

ABSTRACTSusceptible strains of mice that are naturally or experimentally infected with murine intestinal helicobacter species develop hepatic inflammatory lesions that have previously been described as chronic active hepatitis. The inflammatory infiltrates in some models of chronic autoimmunity or inflammation resemble tertiary lymphoid organs hypothesized to arise by a process termed lymphoid organ neogenesis. To determine whether hepatic inflammation caused by infection with helicobacter could give rise to tertiary lymphoid organs, we used fluorescence-activated cell sorting, immunohistochemistry, and in situ hybridization techniques to identify specific components characteristic of lymphoid organs in liver tissue sections and liver cell suspensions from helicobacter-infected mice. Small venules (high endothelial venules [HEVs]) in inflammatory lesions inHelicobacterspecies-infected livers were positive for peripheral node addressin. Mucosal addressin cell adhesion molecule also stained HEVs and cells with a staining pattern consistent with scattered stromal cells. The chemokines SLC (CCL 21) and BLC (CXCL13) were present, as were B220-positive B cells and T cells. The latter included a naïve (CD45lo-CD62Lhi) population. These findings suggest that helicobacter-induced chronic active hepatitis arises through the process of lymphoid organ neogenesis.
Intracellular Replication of
Mycobacterium marinum
within
Dictyostelium discoideum
: Efficient Replication in the Absence of Host Coronin
Authors: Solomon Jonathan M. , Leung Grace S. , Isberg Ralph R. 
Published: May 2003

ABSTRACT

Mycobacterium marinum
causes tuberculosis-like disease in fish and amphibians and has been used as a model mycobacterial species because of its rapid growth and less stringent containment requirements relative to other mycobacterial species. We demonstrate here that
M. marinum
grows within
Dictyostelium discoideum
cells, allowing the genetic analysis of host factors that may modulate the replication of mycobacterial species. Intracellular growth of
M. marinum
was shown to mimic the properties previously observed for growth within cultured phagocytes. A defined bacterial mutant defective for growth within phagocytic cells was shown to be similarly defective for growth within
D. discoideum
. To test the role of host coronin, which was previously hypothesized to positively modulate mycobacterial growth within mouse macrophages, a defined
D. discoideum
coronin mutant was analyzed. Surprisingly, the absence of coronin resulted in enhanced intracellular replication of
M. marinum
relative to the control wild-type strain. Consistent with previous observations, some phagosomes showed persistence of coronin about the surface of the compartment, but colocalization of the protein was far from uniform. We conclude that in
D. discoideum
factors other than coronin support intracellular replication of
M. marinum
.
Analysis of the OspE Determinants Involved in Binding of Factor H and OspE-Targeting Antibodies Elicited during
Borrelia
burgdorferi
Infection in Mice
Authors: Metts Michael S. , McDowell John V. , Theisen Michael , Hansen Paul Robert , Marconi Richard Thomas 
Published: May 2003

ABSTRACT

Immune evasion by Lyme spirochetes is a multifactorial process involving numerous mechanisms. The OspE protein family undergoes antigenic variation during infection and binds factor H (fH) and possibly FHL-1/reconectin. In
Borrelia burgdorferi
B31MI, the OspE family consists of three paralogs: BBL39 (ErpA), BBP38, and BBN38 (ErpP). BBL39 and BBP38 are identical and therefore are referred to here as BBL39. The goals of this study were to assess the specificity of the antibody (Ab) response to the OspE paralogs and to identify the domains or determinants of OspE that are required for the binding of fH and OspE-targeting Abs that develop during infection. Here we demonstrate that at least some of the anti-OspE Abs produced during infection are paralog specific and that Ab binding requires conformational determinants whose formation requires both the N- and C-terminal domains of OspE. The binding of fH to OspE was also found to be dependent on conformational determinants. It is also demonstrated here that all of the OspE paralogs expressed by
B. burgdorferi
B31MI are capable of binding fH. The binding of fH to members of the OspF protein family was also assessed. In contrast to an earlier report, no binding of BBO39 or BBR42 to human fH was detected. Lastly, a series of competitive binding enzyme-linked immunosorbent assay analyses, designed to determine if fH and infection serum Abs bind to the same sites on OspE, revealed that these ligands interact with different regions of OspE.
Comprehensive Analysis of the Factor H Binding Capabilities of
Borrelia
Species Associated with Lyme Disease: Delineation of Two Distinct Classes of Factor H Binding Proteins
Authors: McDowell John V. , Wolfgang Jill , Tran Emily , Metts Michael S. , Hamilton Duncan , Marconi Richard T. 
Published: May 2003

ABSTRACT

Some Lyme disease spirochete isolates can bind complement regulatory protein factor H (fH), a process that may allow evasion of complement-mediated killing. Here we demonstrate significant differences in the fH binding capabilities of species of the
Borrelia
burgdorferi
sensu lato complex. The percentages of
B
.
burgdorferi
,
B
.
afzelii
, and
B
.
garinii
bacteria that bound fH in either enzyme-linked immunosorbent assays or affinity ligand binding immunoblot assays were 100, 83, and 29%, respectively. The fH binding protein profiles were examined and found to exhibit variability among isolates and to form two distinct classes. Differences in fH binding ability may contribute to the differences in pathogenesis and clinical course observed upon infection with different species of the
B
.
burgdorferi
sensu lato complex.
A Dominant Role for Extracellular Glutathione
S
-Transferase from
Onchocerca volvulus
Is the Production of Prostaglandin D
2
Authors: Sommer Alexandra , Rickert Rainer , Fischer Peter , Steinhart Hans , Walter Rolf D. , Liebau Eva 
Published: May 2003

ABSTRACT

The extracellular glutathione
S
-transferase from the filarial parasite
Onchocerca volvulus
(
Ov
-GST1) is a glutathione-dependent prostaglandin D synthase.
Ov
-GST1, located in the outer hypodermal lamellae and in parts of the cuticle, produces prostaglandin D
2
directly at the parasite-host interface.
Ov
-GST1 therefore has the potential to participate in the modulation of the host immune response by contributing to the production of prostanoids; this supports the predominant hypothesis that parasite-derived eicosanoids influence host inflammatory and immune cells.