bluuebunny/crossref_metadata_2025_split huggingface dataset:
IpaD Localizes to the Tip of the Type III Secretion System Needle of
Shigella flexneri
Authors: Espina Marianela , Olive Andrew J. , Kenjale Roma , Moore David S. , Ausar S. Fernando , Kaminski Robert W. , Oaks Edwin V. , Middaugh C. Russell , Picking William D. , Picking Wendy L. 
Published: July 2006

ABSTRACT

Shigella flexneri
, the causative agent of shigellosis, is a gram-negative bacterial pathogen that initiates infection by invading cells within the colonic epithelium. Contact with host cell surfaces induces a rapid burst of protein secretion via the
Shigella
type III secretion system (TTSS). The first proteins secreted are IpaD, IpaB, and IpaC, with IpaB and IpaC being inserted into the host cell membrane to form a pore for translocating late effectors into the target cell cytoplasm. The resulting pathogen-host cross talk results in localized actin polymerization, membrane ruffling, and, ultimately, pathogen entry. IpaD is essential for host cell invasion, but its role in this process is just now coming to light. IpaD is a multifunctional protein that controls the secretion and presentation of IpaB and IpaC at the pathogen-host interface. We show here that antibodies recognizing the surface-exposed N terminus of IpaD neutralize
Shigella
's ability to promote pore formation in erythrocyte membranes. We further show that MxiH and IpaD colocalize on the bacterial surface. When TTSS needles were sheared from the
Shigella
surface, IpaD was found at only the needle tips. Consistent with this, IpaD localized to the exposed tips of needles that were still attached to the bacterium. Molecular analyses then showed that the IpaD C terminus is required for this surface localization and function. Furthermore, mutations that prevent IpaD surface localization also eliminate all IpaD-related functions. Thus, this study demonstrates that IpaD localizes to the TTSA needle tip, where it functions to control the secretion and proper insertion of translocators into host cell membranes.
Antibody-Mediated Disease Remission in the Mouse Model of Lyme Borreliosis
Authors: Barthold Stephen W. , Hodzic Emir , Tunev Stefan , Feng Sunlian 
Published: July 2006

ABSTRACTIn the mouse model of Lyme borreliosis, the host immune response during infection withBorrelia burgdorferiresults in the remission of carditis and arthritis, as well as global reduction of spirochete numbers in tissues, without elimination of infection (28). These events were recapitulated by passive transfer of immune serum from infected immunocompetent mice or T-cell-deficient mice to severe combined immunodeficient (SCID) mice. Previous studies have shown that immune serum is reactive against arthritis-related protein (Arp) and that Arp antiserum induces arthritis remission (16). However, although immune serum from T-cell-deficient mice induced disease remission, it was not reactive against Arp, suggesting that antibody to another antigen may be responsible. T-cell-deficient mouse immune serum was reactive to decorin binding protein A (DbpA). Therefore, DbpA antiserum was tested to determine its ability to induce disease remission in SCID mice. Antisera to Arp or DbpA induced both carditis and arthritis remission but did not significantly reduce spirochete numbers in tissues, based upon quantitativeflaBDNA analysis, nor did treatment affect RNA levels of several genes, includingarpanddbpA. Immunohistochemical labeling of spirochetes in hearts and joints during disease remission induced by adoptive transfer of lymphocytes, passive transfer of immune serum, or passive transfer of DbpA antiserum revealed that such treatment resulted in elimination of spirochetes from heart base and synovium but not vascular walls, tendons, or ligaments. These results suggest that Arp and DbpA antibodies may be active as disease-resolving components in immune serum but antibody against other antigens may be involved in reductions of spirochetes in tissues.
Homologous and Cross-Reactive Immune Responses to Enterotoxigenic
Escherichia coli
Colonization Factors in Bangladeshi Children
Authors: Qadri Firdausi , Ahmed Firoz , Ahmed Tanvir , Svennerholm Ann-Mari 
Published: July 2006

ABSTRACT

We have studied homologous (HoM) and cross-reacting (CR) immunoglobulin A (IgA) antibody responses to colonization factors (CFs) in Bangladeshi children with diarrhea due to enterotoxigenic
E. coli
(ETEC) strains of the CF antigen I (CFA/I) group (CFA/I,
n
= 25; coli surface antigen 4 [CS4],
n
= 8; CS14,
n
= 11) and the CS5 group (CS5,
n
= 15; CS7,
n
= 8), respectively. The responses to the HoM, CR, and heterologous (HeT) CF antigens in each group of patient were studied and compared to that seen in healthy children (
n
= 20). In the CFA/I group (CFA/I and CS14), patients responded with antibody-secreting cell (ASC) responses to HoM CFs (geometric mean, 156 to 329 ASCs/10
6
peripheral blood mononuclear cells [PBMCs]) and to CR CFs (≈15 to 38 ASCs/10
6
PBMCs) but least of all to the HeT CS5 antigen (2 to 4 ASCs/10
6
PBMCs). For the CS5 group of patients with ETEC (CS5 and CS7), likewise, responses to HoM CFs (230 to 372 ASCs/10
6
PBMCs) and CR CFs (27 to 676 ASCs/10
6
PBMCs) were seen, along with lower responses to the HeT CFA/I antigen (9 to 38 ASCs/10
6
PBMCs). Both groups of patients responded with CF-specific IgA antibodies to HoM and CR antigens in plasma but responded less to the HeT CFs. The responses in patients were seen very soon after the onset of diarrhea and peaked around 1 week after onset. Vaccinees who had received two doses of the oral, killed whole-cell ETEC vaccine (CF-BS-ETEC) responded with plasma IgA antibodies to CFA/I, a component of the vaccine, but also to the CR CS14 antigen, which was not included in the vaccine, showing that antibody responses can be stimulated by a CFA/I-containing ETEC vaccine to a CR-reacting antigen in individuals in countries where ETEC is endemic.
Maltodextrin Utilization Plays a Key Role in the Ability of Group A
Streptococcus
To Colonize the Oropharynx
Authors: Shelburne Samuel A. , Sumby Paul , Sitkiewicz Izabela , Okorafor Nnaja , Granville Chanel , Patel Payal , Voyich Jovanka , Hull Richard , DeLeo Frank R. , Musser James M. 
Published: July 2006

ABSTRACT

Analysis of multiple group A
Streptococcus
(GAS) genomes shows that genes encoding proteins involved in carbohydrate utilization comprise some 15% of the core GAS genome. Yet there is a limited understanding of how carbohydrate utilization contributes to GAS pathogenesis. Previous genome-wide GAS studies led us to a focused investigation of MalE, a putative maltodextrin-binding protein. Analysis of 28 strains of 22 distinct M protein serotypes showed that MalE is highly conserved among diverse GAS strains.
malE
transcript levels were significantly increased during growth in human saliva compared to growth in a chemically defined glucose-containing medium or a nutrient-rich medium. MalE was accessible to antibody binding, indicating that it is expressed on the GAS cell surface. Moreover, growth in human saliva appeared to increase MalE surface expression compared to growth in a nutrient-rich medium. Analysis of a Δ
malE
isogenic mutant strain revealed decreased growth in human saliva compared to wild-type GAS. Radiolabeled carbohydrate binding assays showed that MalE was required for the binding of maltose but not glucose. The Δ
malE
isogenic mutant strain colonized a lower percentage of GAS-challenged mice compared to wild-type and genetically complemented strains. Furthermore, decreased numbers of CFU were recovered from mice infected with the Δ
malE
strain compared to those infected with wild-type GAS. These data demonstrate that maltodextrin acquisition is likely to be a key factor in the ability of GAS to successfully infect the oropharynx. Further investigation into carbohydrate transport and metabolism pathways may yield novel insights into GAS pathogenesis.
Reduction of the Ganglioside Binding Activity of the Tetanus Toxin H
C
Fragment Destroys Immunogenicity: Implications for Development of Novel Tetanus Vaccines
Authors: Qazi Omar , Sesardic Dorothea , Tierney Robert , Söderbäck Zahra , Crane Dennis , Bolgiano Barbara , Fairweather Neil 
Published: July 2006

ABSTRACT

In this study, the immunogenicities of the nontoxic H
C
fragment of tetanus toxin and derivatives lacking ganglioside binding activity were compared with that of tetanus toxoid after subcutaneous immunization of mice. Wild-type H
C
(H
C
WT) protein and tetanus toxoid both elicited strong antibody responses against toxoid and H
C
antigens and provided complete protection against toxin challenge. Mutants of H
C
containing deletions essential for ganglioside binding elicited lower responses than H
C
WT. H
C
M115, containing two amino acid substitutions within the ganglioside binding site, provided reduced protection against tetanus toxin challenge compared with H
C
WT, consistent with lower anti-H
C
and anti-toxoid antibody titers. Circular-dichroism spectroscopy and intrinsic fluorescence spectroscopy showed minimal structural perturbation in H
C
M115. We conclude that the presence of the ganglioside binding site within H
C
may be essential for induction of a fully protective anti-tetanus response comparable to that induced by tetanus toxoid by subcutaneous injection.
Intranasal Boosting with an Adenovirus-Vectored Vaccine Markedly Enhances Protection by Parenteral
Mycobacterium bovis
BCG Immunization against Pulmonary Tuberculosis
Authors: Santosuosso Michael , McCormick Sarah , Zhang Xizhong , Zganiacz Anna , Xing Zhou 
Published: July 2006

ABSTRACT

Parenterally administered
Mycobacterium bovis
BCG vaccine confers only limited immune protection from pulmonary tuberculosis in humans. There is a need for developing effective boosting vaccination strategies. We examined a heterologous prime-boost regimen utilizing BCG as a prime vaccine and our recently described adenoviral vector expressing Ag85A (AdAg85A) as a boost vaccine. Since we recently demonstrated that a single intranasal but not intramuscular immunization with AdAg85A was able to induce potent protection from pulmonary
Mycobacterium tuberculosis
challenge in a mouse model, we compared the protective effects of parenteral and mucosal booster immunizations following subcutaneous BCG priming. Protection by BCG prime immunization was not effectively boosted by subcutaneous BCG or intramuscular AdAg85A. In contrast, protection by BCG priming was remarkably boosted by intranasal AdAg85A. Such enhanced protection by intranasal AdAg85A was correlated to the numbers of gamma interferon-positive CD4 and CD8 T cells residing in the airway lumen of the lung. Our study demonstrates that intranasal administration of AdAg85A represents an effective way to boost immune protection by parenteral BCG vaccination.
Role and Regulation of the
Shigella flexneri
Sit and MntH Systems
Authors: Runyen-Janecky Laura , Dazenski Ellyn , Hawkins Stephanie , Warner Lisa 
Published: July 2006

ABSTRACT

Shigella flexneri
possesses at least two putative high-affinity manganese acquisition systems, SitABCD and MntH. Mutations in the genes encoding the components of both of these systems were constructed in
S. flexneri
. The
sitA mntH
mutant showed reduced growth, relative to the wild type, in Luria broth (L broth) containing the divalent metal chelator ethylene diamino-
o
-dihydroxyphenyl acetic acid, and the addition of either iron or manganese restored growth to the level of the wild-type strain. Although the
sitA mntH
mutant was not defective in surviving exposure to superoxide generators, it was defective in surviving exposure to hydrogen peroxide. The
sitA mntH
mutant formed wild-type plaques on Henle cell monolayers but had a reduced ability to survive in activated macrophage lines. Expression of the
S. flexneri sit
and
mntH
promoters was higher when
Shigella
was in Henle cells than when it was in L broth. Expression of both the
sit
and
mntH
promoters was repressed by either iron or manganese, and this repression was partially dependent upon Fur and MntR, respectively. The
mntH
promoter, but not the
sit
promoter, exhibited OxyR-dependent induction in the presence of hydrogen peroxide.
Deletion of the Regulatory Subunit of Protein Kinase A in
Aspergillus fumigatus
Alters Morphology, Sensitivity to Oxidative Damage, andVirulence
Authors: Zhao Wei , Panepinto John C. , Fortwendel Jarrod R. , Fox Lauren , Oliver Brian G. , Askew David S. , Rhodes Judith C. 
Published: July 2006

ABSTRACT

Aspergillus
fumigatus
is an important opportunistic fungal pathogen. The
cAMP-dependent protein kinase (PKA) signaling pathway plays an
important role in regulating morphology, growth, and virulence in a
number of fungal pathogens of plants and animals. We have constructed a
mutant of
A. fumigatus
that lacks the regulatory subunit of
PKA,
pkaR
, and analyzed the growth and development,
sensitivity to oxidative damage, and virulence of the mutant, along
with those of the wild type and a complemented mutant. Both growth and
germination rates of the mutant are reduced, and there are
morphological abnormalities in conidiophores, leading to reduced
conidiation. Conidia from the Δ
pkaR
mutant are more
sensitive to killing by hydrogen peroxide, menadione, paraquat, and
diamide. However, the hyphae of the mutant are killed to a greater
extent only by paraquat and diamide, whereas they are less susceptible
to the effects of hydrogen peroxide. In an immunosuppressed mouse
model, intranasally administered conidia of the mutant are
significantly less virulent than those of the wild type or a
complemented mutant. Unregulated PKA signaling is detrimental to the
virulence of
A. fumigatus
, perhaps through the reduced
susceptibility of the mutant to damage by oxidizing agents and reduced
growth
kinetics.
Swapping of Periplasmic Domains between
Brucella suis
VirB8 and a pSB102 VirB8 Homologue Allows Heterologous Complementation
Authors: Patey Gilles , Qi Zhong , Bourg Gisele , Baron Christian , O'Callaghan David 
Published: July 2006

ABSTRACT

A
Brucella suis
mutant with a nonpolar deletion in the
virB8
gene was attenuated in a macrophage infection model. Complementation with the
B. suis
VirB8 protein expressed from the
virB
promoter restored virulence. Expression of TraJ, a VirB8 homologue from plasmid pSB102, did not restore virulence; however, virulence was partially restored by a chimeric protein containing the N terminus of the
B. suis
VirB8 protein and the C-terminal periplasmic domain of TraJ.
Cytotoxic Necrotizing Factor Type 1 Delivered by Outer Membrane Vesicles of Uropathogenic
Escherichia coli
Attenuates Polymorphonuclear Leukocyte Antimicrobial Activity and Chemotaxis
Authors: Davis Jon M. , Carvalho Humberto M. , Rasmussen Susan B. , O'Brien Alison D. 
Published: July 2006

ABSTRACT

Cytotoxic necrotizing factor type 1 (CNF1), a toxin produced by many strains of uropathogenic
Escherichia coli
(UPEC), constitutively activates small GTPases of the Rho family by deamidating a single amino acid within these target proteins. Such activated GTPases not only stimulate actin polymerization within affected cells but also, as we previously reported, decrease membrane fluidity on mouse polymorphonuclear leukocytes (PMNs). In that same investigation we found that this diminished membrane movement impedes the clustering of the complement receptor CD11b/CD18 on PMNs and, in turn, decreases PMN phagocytic capacity and microbicidal activity on PMNs in direct contact with CNF1-expressing UPEC as well as on those in proximity to wild-type UPEC. The latter observation suggested to us that CNF1 is released from neighboring bacteria, although at the time of initiation of the study described here, no specific mechanism for export of CNF1 from UPEC had been described. Here we present evidence that CNF1 is released from the CNF1-expressing UPEC strain CP9 (serotype O4/H5/K54) in a complex with outer membrane vesicles (OMVs) and that these CNF1-bearing vesicles transfer biologically active CNF1 to PMNs and attenuate phagocyte function. Furthermore, we show that CNF1-bearing vesicles act in a dose-dependent fashion on PMNs to inhibit their chemotactic response to formyl-Met-Leu-Phe, while purified CNF1 does not. We conclude that OMVs provide a means for delivery of CNF1 from a UPEC strain to PMNs and thus negatively affect the efficacy of the acute inflammatory response to these organisms.
Construction and Characterization of an Attenuated Purine Auxotroph in aFrancisella tularensisLive Vaccine Strain
Authors: Pechous Roger , Celli Jean , Penoske Renee , Hayes Stanley F. , Frank Dara W. , Zahrt Thomas C. 
Published: July 2006

ABSTRACTFrancisella tularensisis a facultative intracellular pathogen and is the etiological agent of tularemia. It is capable of escaping from the phagosome, replicating to high numbers in the cytosol, and inducing apoptosis in macrophages of a variety of hosts.F. tularensishas received significant attention recently due to its potential use as a bioweapon. Currently, there is no licensed vaccine againstF. tularensis, although a partially protective live vaccine strain (LVS) that is attenuated in humans but remains fully virulent for mice was previously developed. AnF. tularensisLVS mutant deleted in thepurMCDpurine biosynthetic locus was constructed and partially characterized by using an allelic exchange strategy. TheF. tularensisLVS ΔpurMCDmutant was auxotrophic for purines when grown in defined medium and exhibited significant attenuation in virulence when assayed in murine macrophages in vitro or in BALB/c mice. Growth and virulence defects were complemented by the addition of the purine precursor hypoxanthine or by introduction ofpurMCDNintrans. TheF. tularensisLVS ΔpurMCDmutant escaped from the phagosome but failed to replicate in the cytosol or induce apoptotic and cytopathic responses in infected cells. Importantly, mice vaccinated with a low dose of theF. tularensisLVSΔpurMCDmutant were fully protected against subsequent lethal challenge with the LVS parental strain. Collectively, these results suggest thatF. tularensismutants deleted in thepurMCDbiosynthetic locus exhibit characteristics that may warrant further investigation of their use as potential live vaccine candidates.
Filaria-Induced Monocyte Dysfunction and Its Reversal following Treatment
Authors: Semnani Roshanak Tolouei , Keiser Paul B. , Coulibaly Yaya I. , Keita Falaye , Diallo Abdallah A. , Traore Diakaridia , Diallo Dapa A. , Doumbo Ogobara K. , Traore Sekou F. , Kubofcik Joseph , Klion Amy D. , Nutman Thomas B. 
Published: July 2006

ABSTRACTMonocyte dysfunction in filarial infection has been proposed as one mechanism underlying the diminished antigen-specific T-cell response seen in patent lymphatic filariasis. Cytokine/chemokine production and gene expression in monocytes from filaria-infected patients and uninfected healthy donors were assessed unstimulated and in response to stimulation withStaphylococcus aureusCowan I bacteria plus gamma interferon both before and 8 months following treatment. Monocytes from filaria-infected individuals were studded with intracellular microfilarial antigens. Furthermore, monocytes from these individuals were less capable of producing interleukin-8 (IL-8), Exodus II, MIP-1α, MIP-1β, and IL-1α and preferentially expressed genes involved in apoptosis and adhesion compared with monocytes from uninfected donors. Eight months following treatment with a single dose of ivermectin-albendazole, some of these defects were reversed, with monocyte production of IL-8, IL-1α, MIP-1α, and IL-10 being comparable to that seen in the uninfected controls. In addition, a marked increase in mRNA expression of genes associated with protein metabolism, particularly heat shock proteins, was seen compared with pretreatment expression. These data suggest that the function and gene expression of monocytes in filaria-infected patients are altered but that this dysfunction is partially reversible following antifilarial treatment.
Transcriptional Response Patterns ofChlamydophila psittaciin Different In Vitro Models of Persistent Infection
Authors: Goellner Stefanie , Schubert Evelyn , Liebler-Tenorio Elisabeth , Hotzel Helmut , Saluz Hans Peter , Sachse Konrad 
Published: July 2006

ABSTRACTThe obligatory intracellular bacteriumChlamydophila psittaciis the causative agent of psittacosis in birds and humans. The capability of this zoonotic pathogen to develop a persistent phase is likely to play a role in chronicity of infections, as well as in failure of antibiotic therapy and immunoprophylaxis. To elucidate three different in vitro models for transition ofC. psittacito persistence (iron depletion, penicillin G treatment, and gamma interferon [IFN-γ] exposure), a set of 27 genes was examined by mRNA expression analysis using quantitative real-time PCR. While the phenotypical characteristics were the same as in other chlamydiae, i.e., aberrant morphology of reticulate bodies, loss of cultivability, and rescue of infectivity upon removal of inducers, the transcriptional response ofC. psittacito persistence-inducing factors included several new and distinctive features. Consistent downregulation of membrane proteins, chlamydial sigma factors, cell division protein, and reticulate body-elementary body differentiation proteins from 24 h postinfection onward proved to be a general feature ofC. psittacipersistence. However, other genes displayed considerable variations in response patterns from one model to another, which suggests that there is no persistence model per se. In contrast to results forChlamydia trachomatis, late shutdown of essential genes inC. psittaciwas more comprehensive with IFN-γ-induced persistence, which is probably due to the absence of a functional tryptophan synthesis operon.
Immunogenicity ofMycobacterium tuberculosisAntigens inMycobacterium bovisBCG-Vaccinated andM. bovis-Infected Cattle
Authors: Mustafa A. S. , Skeiky Y. A. , Al-Attiyah R. , Alderson M. R. , Hewinson R. G. , Vordermeier H. M. 
Published: July 2006

ABSTRACTThe development of novel vaccine strategies supplementingMycobacterium bovisBCG (BCG) constitutes an urgent research challenge. To identify potential subunit vaccine candidates, we have tested a series of eight recently identifiedMycobacterium tuberculosisantigens inM. bovis-infected and BCG-vaccinated cattle. These antigens were characterized on the basis of their ability to induce in vitro gamma interferon responses in infected or BCG-vaccinated calves. We were able to establish a hierarchy of these antigens based on how frequently they were recognized in both groups of animals. In particular, we were able to prioritize frequently recognized proteins like Rv0287, Rv1174, and Rv1196 for future evaluation as subunit vaccines to be used in BCG-protein heterologous prime-boost vaccination scenarios. In addition, the antigen most dominantly recognized inM. bovis-infected cattle in this study, Rv3616c, was significantly less frequently recognized by BCG vaccinees and could be a target to improve BCG, for example, by increasing its secretion, in a recombinant BCG vaccine.