bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Receptor-Mediated Signal Transduction byEscherichia coliType IIa Heat-Labile Enterotoxin in the Polarized Human Intestinal Cell Line T84
Authors: Wimer-Mackin Susan , Holmes Randall K. , Wolf Anne A. , Lencer Wayne I. , Jobling Michael G. 
Published: July 2002

ABSTRACTEscherichia colitype IIa heat-labile enterotoxin (LTIIa) binds in vitro with highest affinity to ganglioside GD1b. It also binds in vitro with lower affinity to several other oligosialogangliosides and to ganglioside GM1, the functional receptor for cholera toxin (CT). In the present study, we characterized receptor-mediated signal transduction by LTIIa in the cultured T84 cell model of human intestinal epithelium. Wild-type LTIIa bound tightly to the apical surface of polarized T84 cell monolayers and elicited a Cl−secretory response. LTIIa activity, unlike CT activity, was not blocked by the B subunit of CT. Furthermore, an LTIIa variant with a T14I substitution in its B subunit, which binds in vitro to ganglioside GM1 but not to ganglioside GD1b, was unable to bind to intact T84 cells and did not elicit a Cl−secretory response. These findings show that ganglioside GM1 on T84 cells is not a functional receptor for LTIIa. The LTIIa receptor on T84 cells was inactivated by treatment with neuraminidase. Furthermore, LTIIa binding was blocked by tetanus toxin C fragment, which binds to gangliosides GD1b and GT1b. These findings support the hypothesis that ganglioside GD1b, or possibly a glycoconjugate with a GD1b-like oligosaccharide, is the functional receptor for LTIIa on T84 cells. The LTIIa-receptor complexes from T84 cells were associated with detergent-insoluble membrane microdomains (lipid rafts), extending the correlation between toxin binding to lipid rafts and toxin function that was previously established for CT. However, the extent of association with lipid rafts and the magnitude of the Cl−secretory response in T84 cells were less for LTIIa than for CT. These properties of LTIIa and the previous finding that enterotoxin LTIIb binds to T84 cells but does not associate with lipid rafts or elicit a Cl−secretory response may explain the low pathogenicity for humans of type II enterotoxin-producing isolates ofE. coli.
Effect of 6-Hydroxydopamine on Host Resistance againstListeria monocytogenesInfection
Authors: Miura Tomisato , Kudo Tsuyoshi , Matsuki Akitomo , Sekikawa Kenji , Tagawa Yoh-Ichi , Iwakura Yoichiro , Nakane Akio 
Published: July 2002

ABSTRACTRecent studies have shown that immunocompetent cells bear receptors of neuropeptides and neurotransmitters and that these ligands play roles in the immune response. In this study, the role of the sympathetic nervous system in host resistance againstListeria monocytogenesinfection was investigated in mice pretreated with 6-hydroxydopamine (6-OHDA), which destroys sympathetic nerve termini. The norepinephrine contents of the plasma and spleens were significantly lower in 6-OHDA-treated mice than in vehicle-treated mice. The 50% lethal dose ofL. monocytogeneswas about 20 times higher for 6-OHDA-treated mice than for vehicle-treated mice. Chemical sympathectomy by 6-OHDA upregulated interleukin-12 (IL-12) and tumor necrosis factor-alpha (TNF-α) production in enriched dendritic cell cultures and gamma interferon (IFN-γ) and TNF-α production in spleen cell cultures, whereas chemical sympathectomy had no apparent effect on phagocytic activities, listericidal activities, and nitric oxide production in peritoneal exudate cells and splenic macrophages. Augmentation of host resistance againstL. monocytogenesinfection by 6-OHDA was abrogated in IFN-γ−/−or TNF-α−/−mice, suggesting that upregulation of IFN-γ, IL-12, and TNF-α production may be involved in 6-OHDA-mediated augmentation of antilisterial resistance. Furthermore, adoptive transfer of spleen cells immune toL. monocytogenesfrom 6-OHDA-treated mice resulted in untreated naive recipients that had a high level of resistance againstL. monocytogenesinfection. These results suggest that the sympathetic nervous system may modulate host resistance againstL. monocytogenesinfection through regulation of production of IFN-γ, IL-12, and TNF-α, which are critical in antilisterial resistance.
Role of Capsule in the Pathogenesis of Fowl Cholera Caused byPasteurella multocidaSerogroup A
Authors: Chung Jing Yeng , Wilkie Ian , Boyce John D. , Townsend Kirsty M. , Frost Alan J. , Ghoddusi Majid , Adler Ben 
Published: July 2002

ABSTRACTWe have constructed a defined acapsular mutant inPasteurella multocidaX-73 (serogroup A:1) by disrupting thehexAgene through the insertion of a tetracycline resistance cassette. The genotype of thehexA::tet(M) strain was confirmed by PCR and Southern hybridization, and the acapsular phenotype of this strain was confirmed by electron microscopy. ThehexA::tet(M) strain was attenuated in both mice and chickens. Complementation of the mutant with an intacthexABfragment restored lethality in mice but not in chickens. In contrast to the results described previously forP. multocidaserogroup B (J. D. Boyce and B. Adler, Infect. Immun. 68:3463–3468, 2000), thehexA::tet(M) strain was sensitive to the bactericidal action of chicken serum, whereas the wild-type and complemented strains were both resistant. Following inoculation into chicken muscle, the bacterial count of thehexA::tet(M) strain decreased significantly, while the wild-type and complemented strains both grew rapidly over 4 h. The capsule is thus an essential virulence determinant in the pathogenesis of fowl cholera.
Mycobacterium bovis
BCG
recA
Deletion Mutant Shows Increased Susceptibility to DNA-Damaging Agents but Wild-Type Survival in a Mouse Infection Model
Authors: Sander Peter , Papavinasasundaram K. G. , Dick Thomas , Stavropoulos Evangelos , Ellrott Kerstin , Springer Burkhard , Colston M. Joseph , Böttger Erik C. 
Published: July 2002

ABSTRACT

Pathogenic microorganisms possess antioxidant defense mechanisms for protection from reactive oxygen metabolites which are generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxifies reactive oxygen species, and DNA repair systems, which repair damage resulting from oxidative stress. To (i) determine the relative importance of the DNA repair system when oxidative stress is encountered by the
Mycobacterium tuberculosis
complex during infection of the host and to (ii) provide improved mycobacterial hosts as live carriers to express foreign antigens, the
recA
locus was inactivated by allelic exchange in
Mycobacterium bovis
BCG. The
recA
mutants are sensitive to DNA-damaging agents and show increased susceptibility to metronidazole, the first lead compound active against the dormant
M. tuberculosis
complex. Surprisingly, the
recA
genotype does not affect the in vitro dormancy response, nor does the defect in the DNA repair system lead to attenuation as determined in a mouse infection model. The
recA
mutants will be a valuable tool for further development of BCG as an antigen delivery system to express foreign antigens and as a source of a genetically stable vaccine against tuberculosis.
Genotypic Variation in the
Bordetella pertussis
Virulence Factors Pertactin and Pertussis Toxin in Historical and Recent Clinical Isolates in the United Kingdom
Authors: Fry Norman K. , Neal Shona , Harrison Timothy G. , Miller Elizabeth , Matthews Ruth , George Robert C. 
Published: July 2002

ABSTRACT

The reemergence of pertussis has been reported in several countries despite high vaccination coverage. Studies in The Netherlands and Finland have investigated polymorphism in the genes coding for two important virulence factors of
Bordetella pertussis
, pertactin and pertussis toxin, and identified the emergence and subsequent dominance in circulating strains of pertactin and toxin variants not found in the whole-cell vaccine (WCV). The study described here investigated whether such variation had occurred in the United Kingdom, which presently has low levels of pertussis. Sequence analysis of the genes for pertactin (
prnA
) and the pertussis toxin S1 subunit (
ptxA
) among isolates of
B. pertussis
from 285 United Kingdom patients, from 1920 to 1999, revealed three
prnA
variants,
prnA
(1),
prnA
(2), and
prnA
(3), and two
ptxA
variants,
ptxA
(1) and
ptxA
(2), showing differences in nucleic acid sequence. The proportion of pertactin gene types not included in the United Kingdom WCV, i.e.,
prnA
(2) and
prnA
(3), has increased in recent years and was found in 21 of 86 (24%) strains from the 1980s and 56 of 105 (53%) strains from the 1990s. To date, the presence of these nonvaccine
prnA
types has not been associated with a resurgence of pertussis in the United Kingdom. The distribution of
prnA
and
ptxA
types in The Netherlands, Finland, and the United Kingdom in the 1990s is distinct. The most striking difference in the United Kingdom isolates is that all 105 of the most recent circulating strains (from 1998 to 1999) are of a pertussis toxin type found in the United Kingdom WCV, i.e.,
ptxA
(1).
DuringTrypanosoma cruziInfection CD1d-Restricted NK T Cells Limit Parasitemia and Augment the Antibody Response to a Glycophosphoinositol-Modified Surface Protein
Authors: Duthie Malcolm S. , Wleklinski-Lee Monika , Smith Sherilyn , Nakayama Toshinori , Taniguchi Masaru , Kahn Stuart J. 
Published: July 2002

ABSTRACTTrypanosoma cruziis a protozoan parasite that chronically infects many mammalian species and in humans causes Chagas’ disease, a chronic inflammatory disease. The parasite expresses glycophosphoinositol (GPI), which potently stimulates interleukin 12 (IL-12) production. DuringT. cruziinfection IL-12, and possibly GPI, might stimulate NK T cells to affect the protective and chronic inflammatory responses. Here we report that duringT. cruziinfection CD1d-restricted NK T cells are stimulated as NK T-cell-deficient mice have greater parasitemia. Furthermore, duringT. cruziinfection the percentages of NK T cells in the liver and spleen become decreased for prolonged periods of time, and in vitro stimulation of NK T cells derived from livers of chronically infected mice, compared to uninfected mice, results in increased gamma interferon and IL-4 secretion. Moreover, in NK T-cell-deficient mice the chronic-phase antibody response to a GPI-modified surface protein is decreased. These results indicate that, during the acute infection, NK T cells limit parasitemia and that, during the chronic phase, NK T cells augment the antibody response. Thus, duringT. cruziinfection the quality of an individual’s NK T-cell response can affect the level of parasitemia and parasite tissue burden, the intensity of the chronic inflammatory responses, and possibly the outcome of Chagas’ disease.
PersistentEhrlichia chaffeensisInfection Occurs in the Absence of Functional Major Histocompatibility Complex Class II Genes
Authors: Ganta Roman Reddy , Wilkerson Melinda J. , Cheng Chuanmin , Rokey Aaron M. , Chapes Stephen K. 
Published: July 2002

ABSTRACTHuman monocytic ehrlichiosis is an emerging tick-borne disease caused by the rickettsiaEhrlichia chaffeensis. We investigated the impact of two genes that control macrophage and T-cell function on murine resistance toE. chaffeensis. Congenic pairs of wild-type and toll-like receptor 4 (tlr4)- or major histocompatibility complex class II (MHC-II)-deficient mice were used for these studies. Wild-type mice cleared the infection within 2 weeks, and the response included macrophage activation and the synthesis ofE. chaffeensis-specific Th1-type immunoglobulin G response. The absence of a functionaltlr4gene depressed nitric oxide and interleukin 6 secretion by macrophages and resulted in short-term persistent infections for ≥30 days. In the absence of MHC-II alleles,E. chaffeensisinfections persisted throughout the entire 3-month evaluation period. Together, these data suggest that macrophage activation and cell-mediated immunity, orchestrated by CD4+T cells, are critical for conferring resistance toE. chaffeensis.
ohr, Encoding an Organic Hydroperoxide Reductase, Is an In Vivo-Induced Gene inActinobacillus pleuropneumoniae
Authors: Shea Robin J. , Mulks Martha H. 
Published: July 2002

ABSTRACTActinobacillus pleuropneumoniaeis the causative agent of porcine pleuropneumonia, a disease characterized by pulmonary necrosis and hemorrhage caused in part by neutrophil degranulation. In an effort to understand the pathogenesis of this disease, we have developed an in vivo expression technology (IVET) system to identify genes that are specifically up-regulated during infection. One of the genes that we have identified as being induced in vivo isohr, encoding organic hydroperoxide reductase, an enzyme that could play a role in detoxification of organic hydroperoxides generated during infection. Among the 12 serotypes ofA.pleuropneumoniae,ohrwas found in only serotypes 1, 9, and 11. This distribution correlated with increased resistance to cumene hydroperoxide, an organic hydroperoxide, but not to hydrogen peroxide or to paraquat, a superoxide generator. Functional assays of Ohr activity demonstrated thatA.pleuropneumoniaeserotype 1 cultures, but not serotype 5 cultures, were able to degrade cumene hydroperoxide. InA.pleuropneumoniaeserotype 1, expression ofohrwas induced by cumene hydroperoxide, but not by either hydrogen peroxide or paraquat. In contrast, anohrgene from serotype 1 cloned intoA.pleuropneumoniaeserotype 5 was not induced by cumene hydroperoxide or by other forms of oxidative stress, suggesting the presence of a serotype-specific positive regulator ofohrinA.pleuropneumoniaeserotype 1.
Protective Immune Responses to the 42-Kilodalton (kDa) Region ofPlasmodium yoeliiMerozoite Surface Protein 1 Are Induced by the C-Terminal 19-kDa Region but Not by the Adjacent 33-kDa Region
Authors: Ahlborg Niklas , Ling Irene T. , Howard Wendy , Holder Anthony A. , Riley Eleanor M. 
Published: July 2002

ABSTRACTVaccination of mice with the 42-kDa region ofPlasmodium yoeliimerozoite surface protein 1 (MSP142) or its 19-kDa C-terminal processing product (MSP119) can elicit protective antibody responses in mice. To investigate if the 33-kDa N-terminal fragment (MSP133) of MSP142also induces protection, the gene segment encoding MSP133was expressed as a glutathioneS-transferase (GST) fusion protein. C57BL/6 and BALB/c mice were immunized with GST-MSP133and subsequently challenged with the lethalP. yoeliiYM blood stage parasite. GST-MSP133failed to induce protection, and all mice developed patent parasitemia at a level similar to that in naive or control (GST-immunized) mice; mice immunized with GST-MSP119were protected, as has been shown previously. Specific prechallenge immunoglobulin G (IgG) antibody responses to MSP1 were analyzed by enzyme-linked immunosorbent assay and immunofluorescence. Despite being unprotected, several mice immunized with MSP133had antibody titers (of all IgG subclasses) that were comparable to or higher than those in mice that were protected following immunization with MSP119. The finding thatP. yoeliiMSP133elicits strong but nonprotective antibody responses may have implications for the design of vaccines for humans based onPlasmodium falciparumorPlasmodium vivaxMSP142.
The Nucleotide Sequence of Shiga Toxin (Stx) 2e-Encoding Phage φP27 Is Not Related to Other Stx Phage Genomes, but the Modular Genetic Structure Is Conserved
Authors: Recktenwald Jürgen , Schmidt Herbert 
Published: July 2002

ABSTRACT

In this study we determined the complete nucleotide sequence of Shiga toxin 2e-encoding bacteriophage φP27, isolated from the Shiga toxin-producing
Escherichia coli
patient isolate 2771/97. φP27 is integrated as a prophage in the chromosomal
yecE
gene. This integration generates identity segments of
attL
and
attR
sites with lengths of 11 nucleotides. The integrated prophage genome has a size of 42,575 bp. We identified 58 open reading frames (ORFs), each with a length of >150 nucleotides. The deduced proteins of 44 ORFs showed significant homologies to other proteins present in sequence databases, whereas 14 putative proteins did not. For 29 proteins, we could deduce a putative function. Most of these are related to the basic phage propagation cycle. The φP27 genome represents a mosaic composed of genetic elements which are obviously derived from related and unrelated phages. We identified five short linker sequences of 22 to 151 bp in the φP27 sequence which have also been detected in a couple of other lambdoid phages. These linkers are located between functional modules in the phage genome and are thought to play a role in genetic recombination. Although the overall DNA sequence of φP27 is not highly related to other known phages, the data obtained demonstrate a typical lambdoid genome structure.
NK T Cells Are a Source of Early Interleukin-4 following Infection with Third-Stage Larvae of the Filarial NematodeBrugia pahangi
Authors: Balmer Paul , Devaney Eileen 
Published: July 2002

ABSTRACTInfection of C57BL/6 mice with the third-stage larvae ofBrugia pahangiresults in a rapid expansion of NK1.1+T cells in the spleen and draining lymph nodes. NK T cells produced interleukin-4 in the spleen within 24 h of infection, and these cells were CD4−.
LACK-Specific CD4
+
T Cells That Induce Gamma Interferon Production in Patients with Localized Cutaneous Leishmaniasis during an Early Stage of Infection
Authors: Bourreau Eliane , Prévot Ghislaine , Gardon Jacques , Pradinaud Roger , Hasagewa Hitoshi , Milon Geneviève , Launois Pascal 
Published: July 2002

ABSTRACT

The profile of cytokines induced by soluble leishmania antigen (SLA) and the
Leishmania
homologue of the mammalian receptor for activated C kinase (LACK), a candidate vaccine against leishmaniasis, and the cellular source of the cytokines produced in response to these antigens were analyzed in patients infected with
Leishmania guyanensis
. Gamma interferon (IFN-γ) and interleukin-10 (IL-10) were produced in response to LACK. Although LACK-specific CD4
+
cells producing IFN-γ were isolated only during the early phase of infection (less than 30 days following the onset of infection), cells producing IL-10 in response to LACK were detected in all patients. CD4
+
T cells producing IFN-γ and IL-13 were produced in response to SLA in all patients. SLA- and LACK-specific T cells are effector memory cells, as they are CD45RA
−
CCR7
−
CD4
+
T cells. CD4
+
T cells producing IFN-γ are CD62L
−
, and CD4
+
T cells producing IL-10 are CD62L
+
, indicating that these cells have different tissue-homing capacities. These findings show that SLA and LACK induce both type 1 (IFN-γ) and type 2 (IL-10 or IL-13) cell responses.
The
Pseudomonas
Quinolone Signal Regulates
rhl
Quorum Sensing in
Pseudomonas aeruginosa
Authors: McKnight Susan L. , Iglewski Barbara H. , Pesci Everett C. 
Published: July 2002

ABSTRACT

The opportunistic pathogen
Pseudomonas aeruginosa
uses intercellular signals to control the density-dependent expression of many virulence factors. The
las
and
rhl
quorum-sensing systems function, respectively, through the autoinducers
N
-(3-oxododecanoyl)-
l
-homoserine lactone and
N
-butyryl-
l
-homoserine lactone (C
4
-HSL), which are known to positively regulate the transcription of the elastase-encoding gene,
lasB
. Recently, we reported that a second type of intercellular signal is involved in
lasB
induction. This signal was identified as 2-heptyl-3-hydroxy-4-quinolone and designated the
Pseudomonas
quinolone signal (PQS). PQS was determined to be part of the quorum-sensing hierarchy since its production and bioactivity depended on the
las
and
rhl
quorum-sensing systems, respectively. In order to define the role of PQS in the
P. aeruginosa
quorum-sensing cascade,
lacZ
gene fusions were used to determine the effect of PQS on the transcription of the quorum-sensing system genes
lasR
,
lasI
,
rhlR
, and
rhlI
. We found that in
P. aeruginosa
, PQS caused a major induction of
rhlI′-lacZ
and had lesser effects on the transcription of
lasR′-lacZ
and
rhlR′-lacZ
. We also observed that the transcription of both
rhlI′-lacZ
and
lasB′-lacZ
was cooperatively effected by C
4
-HSL and PQS. Additionally, we present data indicating that PQS was not produced maximally until cultures reached the late stationary phase of growth. Taken together, our results imply that PQS acts as a link between the
las
and
rhl
quorum-sensing systems and that this signal is not involved in sensing cell density.
Effects of Limited Aeration and of the ArcAB System on Intermediary Pyruvate Catabolism in
Escherichia coli
Authors: Alexeeva Svetlana , de Kort Bart , Sawers Gary , Hellingwerf Klaas J. , de Mattos M. Joost Teixeira 
Published: July 2002

ABSTRACT

The capacity of
Escherichia coli
to adapt its catabolism to prevailing redox conditions resides mainly in three catabolic branch points involving (i) pyruvate formate-lyase (PFL) and the pyruvate dehydrogenase complex (PDHc), (ii) the exclusively fermentative enzymes and those of the Krebs cycle, and (iii) the alternative terminal cytochrome
bd
and cytochrome
bo
oxidases. A quantitative analysis of the relative catabolic fluxes through these pathways is presented for steady-state glucose-limited chemostat cultures with controlled oxygen availability ranging from full aerobiosis to complete anaerobiosis. Remarkably, PFL contributed significantly to the catabolic flux under microaerobic conditions and was found to be active simultaneously with PDHc and cytochrome
bd
oxidase-dependent respiration. The synthesis of PFL and cytochrome
bd
oxidase was found to be maximal in the lower microaerobic range but not in a ΔArcA mutant, and we conclude that the Arc system is more active with respect to regulation of these two positively regulated operons during microaerobiosis than during anaerobiosis.
WhiA, a Protein of Unknown Function Conserved among Gram-Positive Bacteria, Is Essential for Sporulation in
Streptomyces coelicolor
A3(2)
Authors: Aínsa J. A. , Ryding N. J. , Hartley N. , Findlay K. C. , Bruton C. J. , Chater K. F. 
Published: July 2002

ABSTRACT

The
whiA
sporulation gene of
Streptomyces coelicolor
A3(2), which plays a key role in switching aerial hyphae away from continued extension growth and toward sporulation septation, was cloned by complementation of
whiA
mutants. DNA sequencing of the wild-type allele and five
whiA
mutations verified that
whiA
is a gene encoding a protein with homologues in all gram-positive bacteria whose genome sequence is known, whether of high or low G+C content. No function has been attributed to any of these WhiA-like proteins. In most cases, as in
S. coelicolor
, the
whiA
-like gene is downstream of other conserved genes in an operon-like cluster. Phenotypic analysis of a constructed disruption mutant confirmed that
whiA
is essential for sporulation.
whiA
is transcribed from at least two promoters, the most downstream of which is located within the preceding gene and is strongly up-regulated when colonies are undergoing sporulation. The up-regulation depends on a functional
whiA
gene, suggesting positive autoregulation, although it is not known whether this is direct or indirect. Unlike the promoters of some other sporulation-regulatory genes, the
whiA
promoter does not depend on the sporulation-specific ς factor encoded by
whiG
.