bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of
bipA
Alleles within and across
Bordetella
Species
Authors: Fuchslocher Bryna , Millar Laura L. , Cotter Peggy A. 
Published: May 2003

ABSTRACT

The
Bordetella
BvgAS signal transduction system controls the expression of at least three phenotypic phases, the Bvg
+
or virulent phase, the Bvg
−
or avirulent phase, and the Bvg
i
or Bvg intermediate phase, which has been hypothesized to be important for transmission.
bipA
, the first identified Bvg
i
-phase gene, encodes a protein with similarity to the well-characterized bacterial adhesins intimin and invasin. Proteins encoded by the
bipA
genes present in
Bordetella pertussis
Tohama I and
Bordetella bronchiseptica
RB50 differ in the number of 90-amino-acid repeats which they possess and in the sequence of the C-terminal domain. To investigate the possibility that
bipA
alleles segregate according to host specificity and to gain insight into the role of BipA and the Bvg
i
phase in the
Bordetella
infectious cycle, we compared
bipA
alleles across members of the
B. bronchiseptica
cluster, which includes both human-infective (
B. pertussis
and
B. parapertussis
hu
) and non-human-infective (
B. bronchiseptica
and
B. parapertussis
ov
) strains.
bipA
genes were present in most, but not all, strains. All
bipA
genes present in
B. bronchiseptica
strains were identical to
bipA
of RB50 (at least with regard to the DNA sequence of the 3′ C-terminal-domain-encoding region, the number of 90-amino-acid repeats encoded, and expression patterns). Although all
bipA
genes present in the other
Bordetella
strains were identical in the 3′ C-terminal-domain-encoding region to
bipA
of
B. pertussis
Tohama I, they varied in the number of 90-amino-acid repeats that they encoded and in expression level. Notably, the genes present in
B. parapertussis
hu
strains were pseudogenes, and the genes present in
B. parapertussis
ov
strains were expressed at significantly reduced levels compared with the levels in
B. pertussis
and
B. bronchiseptica
strains. Our results indicate that there is a correlation between specific
bipA
alleles and specific hosts. They also support the hypothesis that both horizontal gene transfer and fine-tuning of gene expression patterns contribute to the evolution of host adaptation in lineages of the
B. bronchiseptica
cluster.
Involvement of Beta Interferon in Enhancing Inducible Nitric Oxide Synthase Production and Antimicrobial Activity of
Burkholderia
pseudomallei-
Infected Macrophages
Authors: Utaisincharoen P. , Anuntagool N. , Limposuwan K. , Chaisuriya P. , Sirisinha S. 
Published: May 2003

ABSTRACT

Burkholderia
pseudomallei
is the causative agent of melioidosis, a life-threatening disease that affects both humans and animals. This bacterium is able to survive and multiply inside both phagocytic and nonphagocytic cells. We recently reported that mouse macrophages infected with
B
.
pseudomallei
fail to produce a significant level of inducible nitric oxide synthase (iNOS), a crucial enzyme needed for the cells to control the intracellular growth of this bacterium. In the present study, we extended our investigation to demonstrate that, unlike other gram-negative bacteria that have been investigated,
B
.
pseudomallei
only minimally activates beta interferon (IFN-β) production; this minimal activation leads to a low level of interferon regulating factor 1 (IRF-1) in the macrophages, in parallel with poor iNOS expression. Adding exogenous IFN-β to the system could upregulate IRF-1 production, which in turn could enhance iNOS expression in the
B
.
pseudomallei
-infected macrophages and lead to suppression of the intracellular growth of this bacterium. Taken together, these results imply that the failure of macrophages to successfully control the growth and survival of intracellular
B
.
pseudomallei
is related, at least in part, to the defective production of IFN-β, which modulates the ability of macrophages to synthesize iNOS.
Stimulation of Hematopoiesis by the Fms-Like Tyrosine Kinase 3 Ligand Restores Bacterial Induction of Th1 Cytokines in Thermally Injured Mice
Authors: Toliver-Kinsky Tracy E. , Lin Cheng Y. , Herndon David N. , Sherwood Edward R. 
Published: May 2003

ABSTRACTPatients with large burn injuries are susceptible to opportunistic infections due to impaired functions of multiple effector cells of innate immunity and acquired immunity, including macrophages, dendritic cells (DC), natural killer (NK) cells, and T cells. The ability of a host to produce Th1 cytokines, such as gamma interferon (IFN-γ) and interleukin-12 (IL-12), upon infectious challenge is also impaired after burn injury. Stimulation of hematopoiesis, to regenerate new immune cells, may be an effective strategy for improving resistance to infections after severe burn trauma. Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that stimulates the expansion and differentiation of NK cells and DC. Using a mouse model, we tested the hypothesis that Flt3L treatments after burn injury stimulate the production of functional effector cells of innate immunity and restore appropriate Th1 cytokine responses toPseudomonas aeruginosa, a common source of pneumonia and wound infections in burn victims. Flt3L increased splenic cellularity in sham (uninjured) and burned mice and increased the numbers of NK cells (DX5+) and DC (CD11c+). In response toP. aeruginosa, significant increases in the serum IFN-γ levels and the numbers of splenic IFN-γ-producing DC, NK cells, and T cells were observed in Flt3L-treated burned mice compared to the values obtained for untreated burned mice. The splenic levels of IL-12 and IL-15 mRNAs and the IL-12 and IL-15 receptors were also increased. In addition, Flt3L treatment restored the ability of splenic cultures prepared from burned mice to produce IFN-γ and IL-12 after in vitro challenge withP. aeruginosa. Flt3L may have potential for restoring NK cell and DC functions and improving immunity after burn injury.
Role of Phosphoglucomutase of
Stenotrophomonas
maltophilia
in Lipopolysaccharide Biosynthesis, Virulence, and Antibiotic Resistance
Authors: McKay Geoffrey A. , Woods Donald E. , MacDonald Kelly L. , Poole Keith 
Published: May 2003

ABSTRACT

A homologue of the
algC
gene, responsible for the production of a phosphoglucomutase (PGM) associated with LPS and alginate biosynthesis in
Pseudomonas
aeruginosa
,
spgM
, was cloned from
Stenotrophomonas
maltophilia
. The
spgM
gene was shown to encode a bifunctional enzyme with both PGM and phosphomannomutase activities. Mutants lacking
spgM
produced less LPS than the SpgM
+
parent strain and had a tendency for shorter O polysaccharide chains. No changes in LPS chemistry were obvious as a result of the loss of
spgM
. Significantly, however,
spgM
mutants displayed a modest increase in susceptibility to several antimicrobial agents and were completely avirulent in an animal model of infection. The latter finding may relate to the resultant serum sensitivity of
spgM
mutants which, unlike the wild-type parent strain, were rapidly killed by human serum. These data highlight the contribution made by LPS to the antimicrobial resistance and virulence of
S
.
maltophilia
.
T-Cell Responses to CD1-Presented Lipid Antigens in Humans with
Mycobacterium tuberculosis
Infection
Authors: Ulrichs Timo , Moody D. Branch , Grant Ethan , Kaufmann Stefan H. E. , Porcelli Steven A. 
Published: May 2003

ABSTRACT

CD1-restricted presentation of lipid or glycolipid antigens derived from
Mycobacterium tuberculosis
has been demonstrated by in vitro experiments using cultured T-cell lines. In the present work, the frequency of T-cell responses to natural mycobacterial lipids was analyzed in ex vivo studies of peripheral blood lymphocytes from human patients with pulmonary tuberculosis, from asymptomatic individuals with known contact with
M. tuberculosis
documented by conversion of their tuberculin skin tests, and from healthy tuberculin skin test-negative individuals or individuals vaccinated with
Mycobacterium bovis
BCG. Proliferation and gamma interferon enzyme-linked immunospot assays using peripheral blood lymphocytes and autologous CD1
+
immature dendritic cells revealed that T cells from asymptomatic
M. tuberculosis-
infected donors responded with significantly greater magnitude and frequency to mycobacterial lipid antigen preparations than lymphocytes from uninfected healthy donors. By use of these methods, lipid-antigen-specific proliferative responses were minimally detectable or absent in blood samples from patients with active tuberculosis prior to chemotherapy but became detectable in blood samples drawn 2 weeks after the start of treatment. Lipid antigen-reactive T cells were detected predominantly in the CD4-enriched T-cell fractions of circulating lymphocytes, and anti-CD1 antibody blocking experiments confirmed the CD1 restriction of these T-cell responses. Our results provide further support for the hypothesis that lipid antigens serve as targets of the recall response to
M. tuberculosis
, and they indicate that CD1-restricted T cells responding to these antigens comprise a significant portion of the circulating pool of
M. tuberculosis-
reactive T cells in healthy individuals with previous exposure to
M. tuberculosis
.
degS
Is Necessary for Virulence and Is among Extraintestinal
Escherichia coli
Genes Induced in Murine Peritonitis
Authors: Redford Peter , Roesch Paula L. , Welch Rodney A. 
Published: May 2003

ABSTRACT

Extraintestinal
Escherichia coli
strains cause meningitis, sepsis, urinary tract infection, and other infections outside the bowel. We examined here extraintestinal
E. coli
strain CFT073 by differential fluorescence induction. Pools of CFT073 clones carrying a CFT073 genomic fragment library in a promoterless
gfp
vector were inoculated intraperitoneally into mice; bacteria were recovered by lavage 6 h later and then subjected to fluorescence-activated cell sorting. Eleven promoters were found to be active in the mouse but not in Luria-Bertani (LB) broth culture. Three are linked to genes for enterobactin, aerobactin, and yersiniabactin. Three others are linked to the metabolic genes
metA
,
gltB
, and
sucA
, and another was linked to
iha
, a possible adhesin. Three lie before open reading frames of unknown function. One promoter is associated with
degS
, an inner membrane protease. Mutants of the in vivo-induced loci were tested in competition with the wild type in mouse peritonitis. Of the mutants tested, only CFT073
degS
was found to be attenuated in peritoneal and in urinary tract infection, with virulence restored by complementation. CFT073
degS
shows growth similar to that of the wild type at 37°C but is impaired at 43°C or in 3% ethanol LB broth at 37°C. Compared to the wild type, the mutant shows similar serum survival, motility, hemolysis, erythrocyte agglutination, and tolerance to oxidative stress. It also has the same lipopolysaccharide appearance on a silver-stained gel. The basis for the virulence attenuation is unclear, but because DegS is needed for σ
E
activity, our findings implicate σ
E
and its regulon in
E. coli
extraintestinal pathogenesis.
T Cells Are Required for Host Protection againstBrugia malayibut Need Not Produce or Respond to Interleukin-4
Authors: Spencer L. , Shultz L. , Rajan T. V. 
Published: May 2003

ABSTRACTT cells are known to be required for host protection in mouse models ofBrugia malayiinfection. Several independent studies in murine models have also highlighted the rapid induction of Th2-like responses after infection withB. malayiorB. pahangi. Previous data from our laboratory have described a significant increase in permissiveness in the absence of interleukin-4 (IL-4), the “prototypical” Th2 cytokine, involved in both the induction and maintenance of Th2 responses. These observations led to our hypothesis that T cells involved in murine host protection would respond to IL-4 signaling and differentiate into cells of the “type 2” phenotype. As such, these cells would presumably also act as major sources of IL-4. To investigate these hypotheses, we performed several adoptive transfers in which we controlled the cell population(s) able to produce or respond to IL-4. We show here that, in contrast to our original hypotheses, IL-4 production and IL-4 receptor expression by T cells are both dispensable for T-cell-mediated host protection. Instead, our data imply that T cells may be required for eosinophil accumulation at the site of infection.
Nonpathogenic
Escherichia coli
Can Contribute to the Production of Shiga Toxin
Authors: Gamage Shantini D. , Strasser Jane E. , Chalk Claudia L. , Weiss Alison A. 
Published: May 2003

ABSTRACT

The food-borne pathogen,
Escherichia coli
O157:H7, has been associated with gastrointestinal disease and the life-threatening sequela hemolytic uremic syndrome. The genes for the virulence factor, Shiga toxin 2 (Stx2), in
E. coli
O157:H7 are encoded on a temperate bacteriophage under the regulation of the late gene promoter. Induction of the phage lytic cycle is required for toxin synthesis and release. We investigated the hypothesis that nonpathogenic
E. coli
could amplify Stx2 production if infected with the toxin-encoding phage. Toxin-encoding phage were incubated with
E. coli
that were either susceptible or resistant to the phage. The addition of phage to phage-susceptible bacteria resulted in up to 40-fold more toxin than a pure culture of lysogens, whereas the addition of phage to phage-resistant bacteria resulted in significantly reduced levels of toxin. Intestinal
E. coli
isolates incubated with Shiga toxin-encoding phage produced variable amounts of toxin. Of 37 isolates, 3 produced significantly more toxin than was present in the inoculum, and 1 fecal isolate appeared to inactivate the toxin. Toxin production in the intestine was assessed in a murine model. Fecal toxin recovery was significantly reduced when phage-resistant
E. coli
was present. These results suggest that the susceptibility of the intestinal flora to the Shiga toxin phage could exert either a protective or an antagonistic influence on the severity of disease by pathogens with phage-encoded Shiga toxin. Toxin production by intestinal flora may represent a novel strategy of pathogenesis.
Relationship of
plcR
-Regulated Factors to
Bacillus
Endophthalmitis Virulence
Authors: Callegan Michelle C. , Kane Scott T. , Cochran D. Clay , Gilmore Michael S. , Gominet Myriam , Lereclus Didier 
Published: May 2003

ABSTRACT

The explosive, destructive course of
Bacillus
endophthalmitis has been attributed to the production of toxins during infection. In this study we analyzed the contribution of toxins controlled by the global regulator
plcR
to the pathogenesis of experimental
Bacillus
endophthalmitis. Isogenic
plcR-
deficient mutants of
Bacillus cereus
and
Bacillus thuringiensis
were constructed by insertional inactivation of
plcR
by the kanamycin resistance cassette,
aphA3
. Rabbit eyes were injected intravitreally with approximately 100 CFU of wild-type
B. cereus
or
B. thuringiensis
or a
plcR
-deficient mutant. The evolution of endophthalmitis resulting from each
plcR
-deficient mutant was considerably slower than that caused by each wild-type strain. Retinal function was not eliminated until 42 h postinfection in rabbits with endophthalmitis caused by the
plcR
-deficient mutants, whereas wild-type infections resulted in a complete loss of retinal function within 18 h. The intraocular inflammatory cell influx and retinal destruction in
plcR
-deficient endophthalmitis approached the severity observed in wild-ype infections, but not until 36 h postinfection. Gross and histological examinations of eyes infected with
plcR
mutants demonstrated that the anterior and posterior segment changes were muted compared to the changes observed in eyes infected with the wild types. The loss of
plcR
-regulated factors significantly attenuated the severity of
Bacillus
endophthalmitis. The results therefore suggest that
plcR
may represent a target for which adjunct therapies could be designed for the prevention of blindness during
Bacillus
endophthalmitis.
Stx2-Specific Human Monoclonal Antibodies Protect Mice against Lethal Infection with
Escherichia coli
Expressing Stx2 Variants
Authors: Sheoran Abhineet S. , Chapman Susan , Singh Pradeep , Donohue-Rolfe Arthur , Tzipori Saul 
Published: May 2003

ABSTRACT

Shiga toxin-producing
Escherichia coli
(STEC) strains are responsible for causing hemolytic-uremic syndrome (HUS), and systemic administration of Shiga toxin (Stx)-specific human monoclonal antibodies (HuMAbs) is considered a promising approach for prevention or treatment of the disease in children. The goal of the present study was to investigate the ability of Stx2-specific HuMAbs to protect against infections with STEC strains that produce Stx2 variants. Dose-response studies on five HuMAbs, using the mouse toxicity model, revealed that only the three directed against the A subunit were protective against Stx2 variants, and 5C12 was the most effective among the three tested. Two HuMAbs directed against the B subunit, while highly effective against Stx2, were ineffective against Stx2 variants. In a streptomycin-treated mouse model, parenteral administration of 5C12 significantly protected mice up to 48 h after oral bacterial challenge. We conclude that 5C12, reactive against the Stx2 A subunit, is an excellent candidate for immunotherapy against HUS and that antibodies directed against the A subunit of Stx2 have broad-spectrum activity that includes Stx2 variants, compared with those directed against the B subunit.
Critical Contribution of CD28-CD80/CD86 Costimulatory Pathway to Protection fromTrypanosoma cruziInfection
Authors: Miyahira Yasushi , Katae Masaharu , Kobayashi Seiki , Takeuchi Tsutomu , Fukuchi Yoshinosuke , Abe Ryo , Okumura Ko , Yagita Hideo , Aoki Takashi 
Published: May 2003

ABSTRACTThe CD28-CD80/CD86-mediated T-cell costimulatory pathway has been variably implicated in infectious immunity. In this study, we investigated the role of this costimulatory pathway in resistance toTrypanosoma cruziinfection by using CD28-deficient mice and blocking antibodies against CD80 and CD86. CD28-deficient mice exhibited markedly exacerbatedT. cruziinfection, as evidenced by unrelenting parasitemia and 100% mortality after infection with doses that are nonlethal in wild-type mice. The blockade of both CD80 and CD86 by administering specific monoclonal antibodies also exacerbatedT. cruziinfection in wild-type mice. Splenocytes fromT. cruzi-infected, CD28-deficient mice exhibited greatly impaired gamma interferon production in response toT. cruziantigen stimulation in vitro compared to those from infected wild-type mice. The induction ofT. cruziantigen-specific CD8+T cells was also impaired inT. cruzi-infected, CD28-deficient mice. In addition to these defects in natural protection againstT. cruziinfection, CD28-deficient mice were also defective in the induction of CD8+-T-cell-mediated protective immunity againstT. cruziinfection by DNA vaccination. These results demonstrate, for the first time, a critical contribution of the CD28-CD80/CD86 costimulatory pathway not only to natural protection against primaryT. cruziinfection but also to DNA vaccine-induced protective immunity to Chagas' disease.
Plasmid Stability during In Vitro Propagation of
Borrelia burgdorferi
Assessed at a Clonal Level
Authors: Grimm Dorothee , Elias Abdallah F. , Tilly Kit , Rosa Patricia A. 
Published: May 2003

ABSTRACT

Borrelia burgdorferi
causes Lyme disease in humans. The genome of the sequenced type strain B31 MI consists of a linear chromosome, 12 linear plasmids, and 9 circular plasmids. Previous studies by other investigators indicated that some of these plasmids are essential for the survival of the spirochetes in vivo but not in vitro. We have studied plasmid stability during in vitro growth at 23 and 35°C, conditions that approximate the temperatures of the tick vector and the mammalian host, respectively. Starting with two clones that have all 21 plasmids, we investigated plasmid maintenance within the population and on a clonal level. After three passages (27 generations), the cultures were no longer homogeneous and some derivative clones had already lost multiple plasmids. Despite this, one of six clones analyzed after 25 passages (225 generations) retained all but one plasmid (cp9) and was able to complete the mouse-tick-mouse infectious cycle. We analyzed protein composition and regulation of gene expression of clones differing in plasmid content after serial passages. All clones tested exhibited temperature-regulated expression of several proteins, including OspC. In addition, analysis of cultures inoculated from frozen stocks suggests that freezing and/or thawing contributes to heterogeneity in the outgrowth population with respect to plasmid content. Our investigations show that in vitro propagation of a clone leads to a heterogeneous population but that virulent clones can persist through extended passage. We therefore conclude that isogenicity of clones must be confirmed irrespective of their in vitro passage history.
TheMycobacterium tuberculosisRecombinant 27-Kilodalton Lipoprotein Induces a Strong Th1-Type Immune Response Deleterious to Protection
Authors: Hovav Avi-Hai , Mullerad Jacob , Davidovitch Liuba , Fishman Yolanta , Bigi Fabiana , Cataldi Angel , Bercovier Herve 
Published: May 2003

ABSTRACTTh1 immune response is essential in the protection against mycobacterial intracellular pathogens. Lipoproteins trigger both humoral and cellular immune responses and may be candidate protective antigens. We studied in BALB/c mice the immunogenicity and the protection offered by the recombinant 27-kDaMycobacterium tuberculosislipoprotein and the corresponding DNA vaccine. Immunization with the 27-kDa antigen resulted in high titers of immunoglobulin G1 (IgG1) and IgG2a with a typical Th1 profile and a strong delayed hypersensitivity response. A strong proliferation response was observed in splenocytes, and significant nitric oxide production and gamma interferon secretion but not interleukin 10 secretion were measured. Based on these criteria, the 27-kDa antigen induced a typical Th1-type immune response thought to be necessary for protection. Surprisingly, in 27-kDa-vaccinated mice (protein or DNA vaccines) challenged byM. tuberculosisH37Rv or BCG strains, there was a significant increase in the numbers of CFU in the spleen compared to that for control groups. Furthermore, the protection provided by BCG or other mycobacterial antigens was completely abolished once the 27-kDa antigen was added to the vaccine preparations. This study indicates that the 27-kDa antigen has an adverse effect on the protection afforded by recognized vaccines. We are currently studying how the 27-kDa antigen modulates the mouse immune response.