bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Type 1 Fimbriae by Unlinked FimB- and FimE-Like Recombinases in Uropathogenic
Escherichia coli
Strain CFT073
Authors: Bryan Andrew , Roesch Paula , Davis Lindsay , Moritz Rebecca , Pellett Shahaireen , Welch Rodney A. 
Published: January 2006

ABSTRACT

Genomic DNA sequence analysis of the uropathogenic
Escherichia coli
strain CFT073 revealed that besides the
fimB
and
fimE
recombinase genes that control the type 1 pilus
fim
phase switch, there are three additional
fimB
- and
fimE
-like genes:
ipuA
,
ipuB
, and
ipbA
. Alignment of the predicted amino acid sequences showed that the five recombinases range in sequence similarity from 63 to 70%. An epidemiological survey indicates that
ipuA
and
ipuB
are present and linked next to the
dsdCXA
locus in 24 of 67 uropathogenic
E. coli
strains but are found in only 1 of 15 normal human fecal isolates. The
ipbA
sequence located next to the
betABIT
locus was found in 42 of 67 uropathogenic isolates and 8 of 15 of the commensal strains. We show that two of these recombinases, those encoded by
ipuA
and
ipbA
, can function at the type 1 pilus
fim
switch. In a CFT073 deletion mutant lacking all five recombinase genes, recombinant
ipuA
or
ipbA
provided in
trans
inverted the
fim
element from the off state to the on state. When a
fim
OFF CFT073 Δ
fimBE
mutant was used to infect the urinary tracts of mice, a switch to the
fim
on state was detected within 24 h in bacteria recovered from urine, the bladder, and the kidneys. A
fim
OFF CFT073 Δ
fimBE ipuB ipbA
mutant also demonstrated the ability to switch from the
fim
off state to the on state during mouse infection. CFT073 recombinase mutants derived from isolates in either the
fim
on or off state showed a reciprocal relationship for motility. Switches from a nonmotile to a motile phenotype and from a
fim
on to off genotype were observed in
fim
ON CFT073 Δ
fimBE ipuAB ipbA
mutants when
ipuA
or
fimB
was provided in
trans
. Together these results indicate that
ipuA
has
fimB
-like on-to-off and off-to-on
fim
switching activity and that
ipbA
has the ability to switch
fim
from the off to the on orientation.
Identification of Novel γδ T-Cell Subsets following Bacterial Infection in the Absence of Vγ1+T Cells: Homeostatic Control of γδ T-Cell Responses to Pathogen Infection by Vγ1+T Cells
Authors: Newton Darren J. , Andrew Elizabeth M. , Dalton Jane E. , Mears Rainy , Carding Simon R. 
Published: January 2006

ABSTRACTAlthough γδ T cells are a common feature of many pathogen-induced immune responses, the factors that influence, promote, or regulate the response of individual γδ T-cell subsets to infection is unknown. Here we show that in the absence of Vγ1+T cells, novel subsets of γδ T cells, expressing T-cell receptor (TCR)-Vγ chains that normally define TCRγδ+dendritic epidermal T cells (DETCs) (Vγ5+), intestinal intraepithelial lymphocytes (iIELs) (Vγ7+), and lymphocytes associated with the vaginal epithelia (Vγ6+), are recruited to the spleen in response to bacterial infection in TCR-Vγ1−/−mice. By comparison of phenotype and structure of TCR-Vγ chains and/or -Vδ chains expressed by these novel subsets with those of their epithelium-associated counterparts, the Vγ6+T cells elicited in infected Vγ1−/−mice were shown to be identical to those found in the reproductive tract, from where they are presumably recruited in the absence of Vγ1+T cells. By contrast, Vγ5+and Vγ7+T cells found in infected Vγ1−/−mice were distinct from Vγ5+DETCs and Vγ7+iIELs. Functional analyses of the novel γδ T-cell subsets identified for infected Vγ1−/−mice showed that whereas the Vγ5+and Vγ7+subsets may compensate for the absence of Vγ1+T cells by producing similar cytokines, they do not possess cytocidal activity and they cannot replace the macrophage homeostasis function of Vγ1+T cells. Collectively, these findings identify novel subsets of γδ T cells, the recruitment and activity of which is under the control of Vγ1+T cells.
Dendritic Cell Immaturity during Infancy Restricts the Capacity To Express Vaccine-Specific T-Cell Memory
Authors: Upham John W. , Rate Angela , Rowe Julie , Kusel Merci , Sly Peter D. , Holt Patrick G. 
Published: January 2006

ABSTRACTThe capacity of the immune system in infants to develop stable T-cell memory in response to vaccination is attenuated, and the mechanism(s) underlying this developmental deficiency in humans is poorly understood. The present study focuses on the capacity for expression of in vitro recall responses to tetanus and diphtheria antigens in lymphocytes from 12-month-old infants vaccinated during the first 6 months of life. We demonstrate that supplementation of infant lymphocytes with “matured” dendritic cells (DC) cultured from autologous CD14+precursors unmasks previously covert cellular immunity in the form of Th2-skewed cytokine production. Supplementation of adult lymphocytes with comparable prematured autologous DC also boosted vaccine-specific T-cell memory expression, but in contrast to the case for the infants, these cytokine responses were heavily Th1 skewed. Compared to adults, infants had significantly fewer circulating myeloid DC (P< 0.0001) and plasmacytoid DC (P< 0.0001) as a proportion of peripheral blood mononuclear cells. These findings suggest that deficiencies in the numbers of antigen-presenting cells and their functional competence at 12 months of age limit the capacity to express effector memory responses and are potentially a key factor in reduced vaccine responsiveness in infants.
Flagellin Is an Effective Adjuvant for Immunization against Lethal Respiratory Challenge withYersinia pestis
Authors: Honko Anna N. , Sriranganathan Nammalwar , Lees Cynthia J. , Mizel Steven B. 
Published: January 2006

ABSTRACTGram-negative flagellin, a Toll-like receptor 5 (TLR5) agonist, is a potent inducer of innate immune effectors such as cytokines and nitric oxide. In the lung, flagellin induces a localized and transient innate immune response characterized by neutrophil infiltration and the production of cytokines and chemokines. In view of the extraordinary potency of flagellin as an inducer of innate immunity and the contribution of innate responses to the development of adaptive immunity, we evaluated the efficacy of recombinantSalmonellaflagellin as an adjuvant in an acellular plague vaccine. Mice immunized intranasally or intratracheally with the F1 antigen ofYersinia pestisand flagellin exhibited dramatic increases in anti-F1 plasma immunoglobulin G (IgG) titers that remained stable over time. In contrast, control mice had low or undetectable antibody responses. The IgG1/IgG2a ratio of antibody titers against F1 in immunized mice is consistent with a Th2 bias. However, no significant antigen-specific IgE production was detected. Interferons, tumor necrosis factor alpha, and interleukin-6 were not essential for the adjuvant effects of flagellin. Preexisting antiflagellin antibodies had no significant effect on the adjuvant activity of flagellin. Importantly, intranasal immunization with flagellin and the F1 antigen was protective against intranasal challenge with virulentY. pestisCO92, with 93 to 100% survival of immunized mice. Lastly, vaccination of cynomolgus monkeys with flagellin and a fusion of the F1 and V antigens ofY. pestisinduced a robust antigen-specific IgG antibody response.
PsrA Is a Positive Transcriptional Regulator of the Type III Secretion System in
Pseudomonas aeruginosa
Authors: Shen D. K. , Filopon D. , Kuhn L. , Polack B. , Toussaint B. 
Published: January 2006

ABSTRACT

The type III secretion system (TTSS) of
Pseudomonas aeruginosa
is induced in vivo upon contact with eukaryotic cells and in vitro by calcium depletion in culture medium. We have observed a previously identified protein, PsrA, necessary for full activation of TTSS gene expression in
P. aeruginosa
. Electrophoretic mobility shift assays showed that recombinant PsrA could bind to the
exsCEBA
promoter region. A mutant with a deletion in the
psrA
gene was constructed. Using transcriptional fusions, we demonstrated that PsrA is required for the full activation of transcription of the TTSS regulatory operon
exsCEBA
and effector
exoS
, although the deletion mutant still responded to calcium depletion, to serum, and to host cell contact. The
psrA
mutant showed a marked decrease in the secretion of the type III effectors and weak resistance to phagocyte-like PLB-985 cells. The defect in TTSS transcription and secretion in the
psrA
mutant could be complemented by expression in
trans
of
psrA
. PsrA was previously identified as a transcriptional activator of RpoS, a central regulator during stationary phase. We confirmed with our strain that RpoS has a negative effect on TTSS gene expression. Taken altogether, these results suggest that PsrA is a newly identified activator that is involved in the expression of the TTSS by enhancing the
exsCEBA
transcriptional level.
Role of Gluconeogenesis and the Tricarboxylic Acid Cycle in the Virulence of
Salmonella enterica
Serovar Typhimurium in BALB/c Mice
Authors: Tchawa Yimga Merlin , Leatham Mary P. , Allen James H. , Laux David C. , Conway Tyrrell , Cohen Paul S. 
Published: January 2006

ABSTRACT

In
Salmonella enterica
serovar Typhimurium, the Cra protein (
c
atabolite
r
epressor/
a
ctivator) regulates utilization of gluconeogenic carbon sources by activating transcription of genes in the gluconeogenic pathway, the glyoxylate bypass, the tricarboxylic acid (TCA) cycle, and electron transport and repressing genes encoding glycolytic enzymes. A serovar Typhimurium SR-11 Δ
cra
mutant was recently reported to be avirulent in BALB/c mice via the peroral route, suggesting that gluconeogenesis may be required for virulence. In the present study, specific SR-11 genes in the gluconeogenic pathway were deleted (
fbp
,
glpX
,
ppsA
, and
pckA
), and the mutants were tested for virulence in BALB/c mice. The data show that SR-11 does not require gluconeogenesis to retain full virulence and suggest that as yet unidentified sugars are utilized by SR-11 for growth during infection of BALB/c mice. The data also suggest that the TCA cycle operates as a full cycle, i.e., a
sucCD
mutant, which prevents the conversion of succinyl coenzyme A to succinate, and an Δ
sdhCDA
mutant, which blocks the conversion of succinate to fumarate, were both attenuated, whereas both an SR-11 Δ
aspA
mutant and an SR-11 Δ
frdABC
mutant, deficient in the ability to run the reductive branch of the TCA cycle, were fully virulent. Moreover, although it appears that SR-11 replenishes TCA cycle intermediates from substrates present in mouse tissues, fatty acid degradation and the glyoxylate bypass are not required, since an SR-11 Δ
fadD
mutant and an SR-11 Δ
aceA
mutant were both fully virulent.
Genetic and Phenotypic Diversity of Quorum-Sensing Systems in Clinical and Environmental Isolates of
Vibrio cholerae
Authors: Joelsson Adam , Liu Zhi , Zhu Jun 
Published: January 2006

ABSTRACT

Vibrio cholerae
is the causative agent of cholera, a severe and devastating diarrheal disease.
V. cholerae
lives naturally in various aquatic habitats during interepidemic periods. Recent studies reveal that quorum-sensing systems, which exist in many bacteria and help them monitor their population densities and regulate various cellular functions, control
V. cholerae
pathogenesis, biofilm formation, and protease production. In this study we surveyed quorum-sensing systems in 16 geographically diverse
V. cholerae
strains from epidemic-causing O1 and O139 strains as well as non-O1/non-O139 and environmental isolates and discovered an unexpectedly high rate of dysfunctional components. We also found that a functional quorum-sensing system conferred a survival advantage on bacteria in biofilms when the bacteria were exposed to seawater, though quorum sensing was less important to survival in a planktonic state under the same conditions. These findings suggest that variations in quorum-sensing systems are due to environmental selective pressures and might be beneficial to
V. cholerae
's fitness under certain conditions found in its natural reservoirs.
Fas Ligand Deficiency Impairs Host Inflammatory Response against Infection with the SpirocheteBorrelia burgdorferi
Authors: Shi Cuixia , Wolfe Julie , Russell Jennifer Q. , Fortner Karen , Hardin Nicholas , Anguita Juan , Budd Ralph C. 
Published: January 2006

ABSTRACTLyme disease represents a complex response toBorrelia burgdorferithat involves both bacterial factors as well as host responses. This results in an inflammatory reaction at several sites, including the synovial lining of joints. Synovial tissues of inflamed joints contain cells expressing high levels of Fas and Fas ligand (FasL). Although Fas stimulation is typically associated with cell death, it can also transmit stimulatory signals to certain cell types. Among these are dendritic cells and macrophages, which are abundant in inflamed synovium. To better assess the role of FasL in the pathogenesis of Lyme arthritis, we evaluated the response toB. burgdorferiinfection in C3H/HeJgldmice that bear a nonfunctional mutation in FasL. Compared to wild-type C3H+/+mice, C3Hgldmice had a similar bacterial burden and antibody response 2 weeks and 4 weeks following infection, but they manifested a significantly reducedBorrelia-specific cytokine response. In addition, C3Hgldmice developed a greatly reduced incidence and severity of arthritis. The findings document a contribution of FasL to the host inflammatory response toB. burgdorferi.
Conservation and Diversity of HMW1 and HMW2 Adhesin Binding Domains among Invasive Nontypeable
Haemophilus influenzae
Isolates
Authors: Giufrè Maria , Muscillo Michele , Spigaglia Patrizia , Cardines Rita , Mastrantonio Paola , Cerquetti Marina 
Published: January 2006

ABSTRACT

The pathogenesis of nontypeable
Haemophilus influenzae
(NTHi) begins with adhesion to the rhinopharyngeal mucosa. In almost 80% of NTHi clinical isolates, the HMW proteins are the major adhesins. The prototype HMW1 and HMW2 proteins, identified in NTHi strain 12, exhibit different binding specificities. The two binding domains have been localized in regions of maximal sequence dissimilarity (40% identity, 58% similarity). Two areas within these binding domains have been found essential for full level adhesive activity (designated the core-binding domains). To investigate the conservation and diversity of the HMW1 and HMW2 core-binding domains among isolates, PCR and DNA sequencing were used. First, we separately amplified the
hmw1A
-like and
hmw2A
-like structural genes in nine invasive NTHi isolates, discovering two new
hmwA
alleles, whose sequences are herein reported. Then, the
hmw1A-
like and
hmw2A
-like PCR products were used as the template in nested PCR to produce amplicons encompassing the encoding sequences of the two core-binding domains. In-depth sequence analysis was then performed among sequences of each group, with the support of specific computer programs. Overall, extensive sequence diversity among isolates was highlighted. However, similarity plots showed patterns consisting of peaks of relatively high similarity alternating with strongly divergent regions. The phylogenetic tree clearly indicated the HMW1-like and HMW2-like core-binding domain sequences as two clusters. Distinct sets of conserved amino acid motifs were identified within each group of sequences using the MEME/MOTIFSEARCH tool. Since HMW adhesins could represent candidates for future vaccines, identification of specific patterns of conserved motifs in otherwise highly variable regions is of great interest.
Mn
2+
-Dependent Regulation of Multiple Genes in
Streptococcus pneumoniae
through PsaR and the Resultant Impact on Virulence
Authors: Johnston Jason W. , Briles David E. , Myers Lisa E. , Hollingshead Susan K. 
Published: January 2006

ABSTRACT

The concentration of Mn
2+
is 1,000-fold higher in secretions than it is at internal sites of the body, making it a potential signal by which bacteria can sense a shift from a mucosal environment to a more invasive site. PsaR, a metal-dependent regulator in
Streptococcus pneumoniae
, was found to negatively affect the transcription of
psaBCA
,
pcpA
,
rrgA
,
rrgB
,
rrgC
,
srtBCD
, and
rlrA
in the presence of Mn
2+
.
psaBCA
encode an ABC-type transporter for Mn
2+
.
pcpA
,
rrgA
,
rrgB
, and
rrgC
encode several outer surface proteins.
srtBCD
encode a cluster of sortase enzymes, and
rlrA
encodes a transcriptional regulator. Steady-state RNA levels are high under low Mn
2+
concentrations in the wild-type strain and are elevated under both high and low Mn
2+
concentrations in a
psaR
mutant strain. RlrA is an activator of
rrgA
,
rrgB
,
rrgC
, and
srtBCD
(D. Hava and A. Camilli, Mol. Microbiol.
45:
1389-1406, 2002), suggesting that PsaR may indirectly control these genes through
rlrA
, while PsaR-dependent repression of
psaBCA
,
pcpA
, and
rlrA
transcription is direct. The impact of Mn
2+
-dependent regulation on virulence was further examined in mouse models of pneumonia and nasopharyngeal carriage. The abilities of Δ
psaR
,
pcpA
, and Δ
psaR
Δ
pcpA
mutant strains to colonize the lung were reduced compared to those of the wild type, confirming that both PcpA-mediated gene regulation and PsaR-mediated gene regulation are required for full virulence in the establishment of pneumonia. Neither PcpA nor PsaR was found to be required for colonization of the nasopharynx in a carriage model. This is the first demonstration of Mn
2+
acting as a signal for the expression of virulence factors within different host sites.
Tumor Necrosis Factor Alpha and Gamma Interferon, but Not Hemorrhage or Pathogen Burden, Dictate Levels of Protective Fibrin Deposition during Infection
Authors: Mullarky Isis K. , Szaba Frank M. , Berggren Kiera N. , Kummer Lawrence W. , Wilhelm Lindsey B. , Parent Michelle A. , Johnson Lawrence L. , Smiley Stephen T. 
Published: January 2006

ABSTRACTWhile coagulation often causes pathology during infectious disease, we recently demonstrated that fibrin, a product of the coagulation pathway, performs a critical protective function during acute toxoplasmosis (L. L. Johnson, K. N. Berggren, F. M. Szaba, W. Chen, and S. T. Smiley, J. Exp. Med.197:801-806, 2003). Here, we investigate the mechanisms regulating the formation of this protective fibrin. Through comparisons ofToxoplasma-infected wild-type and cytokine-deficient mice we dissociate, for the first time, the relative fibrin-regulating capacities of pathogen products, host cytokines, and infection-stimulated hemorrhage. Remarkably, neither the pathogen burden nor hemorrhage is a primary regulator of fibrin levels. Rather, two type 1 cytokines exert dominant and counterregulatory roles: tumor necrosis factor alpha (TNF-α), acting via the type 1 TNF-α receptor, promotes fibrin deposition, while gamma interferon (IFN-γ), acting via STAT1 and IFN-γ receptors expressed on radioresistant cells, suppresses fibrin deposition. These findings have important clinical implications, as they establish that cytokines known to regulate pathological coagulation also dictate levels of protective fibrin deposition. We present a novel model depicting mechanisms by which the immune system can destroy infected tissue while independently restraining hemorrhage and promoting tissue repair through the deliberate deposition of protective fibrin.
Identification of aNaegleria fowleriMembrane Protein Reactive with Anti-Human CD59 Antibody
Authors: Fritzinger Angela E. , Toney Denise M. , MacLean Rebecca C. , Marciano-Cabral Francine 
Published: January 2006

ABSTRACTNaegleria fowleri, the causative agent of primary amebic meningoencephalitis, is resistant to complement lysis. The presence of a complement regulatory protein on the surface ofN. fowleriwas investigated. Southern blot and Northern blot analyses demonstrated hybridization of a radiolabeled cDNA probe for CD59 to genomic DNA and RNA, respectively, from pathogenicN. fowleri. An 18-kDa immunoreactive protein was detected on the membrane ofN. fowleriby Western immunoblot and immunofluorescence analyses with monoclonal antibodies for human CD59. Complement component C9 immunoprecipitated with theN. fowleri“CD59-like” protein from amebae incubated with normal human serum. In contrast, a gene or protein similar to CD59 was not detected in nonpathogenic, complement-sensitiveN. gruberiamebae. Collectively, our studies suggest that a protein reactive with antibodies to human CD59 is present on the surface ofN. fowleriamebae and may play a role in resistance to lysis by cytolytic proteins.
Pathogenesis of B-Cell Superantigen-Induced Immune Complex-Mediated Inflammation
Authors: Anderson Amy L. , Sporici Romeo , Lambris John , LaRosa David , Levinson Arnold I. 
Published: January 2006

ABSTRACTStaphylococcal protein A (SpA) is representative of a new class of antigens, the B-cell superantigens (SAgs). These antigens bind to the Fab regions of immunoglobulin molecules outside their complementarity-determining regions. SpA, the best-studied B-cell SAg, reacts with the Fabs of most VH3+immunoglobulins, which are expressed on 30 to 60% of human peripheral B cells. Therefore, B-cell SAgs like SpA have great potential to elicit inflammatory responses in vivo. We previously reported that the interaction of SpA with VH3+immunoglobulin molecules leads to activation of the complement cascade and produces a histologic pattern of inflammation in the skin of a rabbit indicative of immune complex injury. To elucidate the cellular and molecular events contributing to this type of unconventional immune complex-mediated inflammation, we established a mouse peritoneal Arthus reaction model. Mice treated intravenously with human polyclonal immunoglobulin G (IgG), followed by intraperitoneal injection of SpA, showed neutrophil influx into the peritoneal cavity with peak numbers appearing at 8 h. This inflammatory reaction was dependent on the interaction of SpA with VH3+IgG. Mast cells, FcγRIII, complement components, and tumor necrosis factor alpha play obligatory roles, and the reaction is associated with the local release of the CXC chemokines macrophage inflammatory protein 2 and KC. The data provide further compelling evidence for the induction of immune complex-mediated injury by a B-cell SAg and highlight important factors contributing to the pathogenesis of this novel type of inflammatory reaction.