bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of the Antimicrobial Peptide CRAMP in the Blood-Brain Barrier and Meninges after Meningococcal Infection
Authors: Bergman Peter , Johansson Linda , Wan Hong , Jones Allison , Gallo Richard L. , Gudmundsson Gudmundur H. , Hökfelt Tomas , Jonsson Ann-Beth , Agerberth Birgitta 
Published: November 2006

ABSTRACT

Antimicrobial peptides are present in most living species and constitute important effector molecules of innate immunity. Recently, we and others have detected antimicrobial peptides in the brain. This is an organ that is rarely infected, which has mainly been ascribed to the protective functions of the blood-brain barrier (BBB) and meninges. Since the bactericidal properties of the BBB and meninges are not known, we hypothesized that antimicrobial peptides could play a role in these barriers. We addressed this hypothesis by infecting mice with the neuropathogenic bacterium
Neisseria meningitidis
. Brains were analyzed for expression of the antimicrobial peptide CRAMP by immunohistochemistry in combination with confocal microscopy. After infection, we observed induction of CRAMP in endothelial cells of the BBB and in cells of the meninges. To explore the functional role of CRAMP in meningococcal disease, we infected mice deficient of the CRAMP gene. Even though CRAMP did not appear to protect the brain from invasion of meningococci, CRAMP knockout mice were more susceptible to meningococcal infection than wild-type mice and exhibited increased meningococcal growth in blood, liver, and spleen. Moreover, we could demonstrate that carbonate, a compound that accumulates in the circulation during metabolic acidosis, makes meningococci more susceptible to CRAMP.
CXCL16 Regulates Cell-Mediated Immunity toSalmonella entericaSerovar Enteritidis via Promotion of Gamma Interferon Production
Authors: Fahy Olivier L. , Townley Scott L. , McColl Shaun R. 
Published: November 2006

ABSTRACTCXCL16 is a recently discovered multifaceted chemokine that has been shown not only to recruit activated T lymphocytes but also to play a direct role in the binding and phagocytosis of bacteria by professional antigen-presenting cells. In this study, we investigated the role of CXCL16 in vivo in the regulation of the immune response using a murine model ofSalmonella entericaserovar Enteritidis infection. The expression of CXCL16 was strongly upregulated in the spleens and livers of animals developing an immune response to a primary acute infection but not in the Peyer's patches. Animals developing a secondary response after reexposure to the bacteria displayed a similar pattern of expression. During the primary response, prior treatment with neutralizing antibodies to CXCL16 induced a significant increase in bacterial burden in the spleen and liver. The production of gamma interferon (IFN-γ) by the lymphocytes in the spleen was decreased by anti-CXCL16 treatment. In comparison, during the secondary response, anti-CXCL16 treatment also significantly increased bacterial burden in both the spleen and liver but had no effect on IFN-γ production. No role was found for CXCL16 in the production of antibody against SefA, a major surface antigen ofS. enteritidis. Together, these results demonstrate a role for CXCL16 in the control of bacterial colonization of target organs and, more specifically, in the regulation of the cell-mediated arm of the primary response toS. enteritidis.
CXCL10/Gamma Interferon-Inducible Protein 10-Mediated Protection againstLeishmania amazonensisInfection in Mice
Authors: Vasquez Rene E. , Soong Lynn 
Published: November 2006

ABSTRACTLeishmania amazonensiscan cause progressive disease in most inbred strains of mice. We have previously shown thatL. amazonensis-infected C57BL/6 mice have profound impairments in expression of proinflammatory cytokines and chemokines and in activation of antigen-specific CD4+T cells. These impairments are independent of interleukin-4 (IL-4) but partially due to IL-10 production. The precise mechanism of pathogenesis associated withL. amazonensisinfection remains largely unresolved. Since chemokines are essential mediators of leukocyte recruitment and effector cell function, we hypothesized that these molecules are important for the initiation of early responses locally and for the eventual control of the infection. In this study, we examined the roles of CXCL10/gamma interferon-inducible protein 10 (IP-10) and CCL2/monocyte chemoattractant protein 1 (MCP-1) in the activation of the macrophage effector function in vitro and their efficacy in ameliorating infection in vivo. Bone marrow-derived macrophages of both BALB/c and C57BL/6 mice were treated with increasing concentrations of recombinant chemokines prior to infection with either stationary-phase promastigotes or tissue-derived amastigotes. We found that treatment with IP-10 or MCP-1 significantly reduced parasite burdens, in a dose-dependent manner, and triggered nitric oxide production. When susceptible C57BL/6 mice were injected locally with IP-10 followingL. amazonensisinfection, there was a significant delay in lesion development and a reduction in parasite burdens, accompanied by 7- and 3.5-fold increases in gamma interferon and IL-12 secretion, respectively, in restimulated lymph node cells. This study confirms that IP-10 plays a protective role in promoting the reduction of intracellular parasites and thereby opens new avenues for therapeutic control of nonhealing cutaneous leishmaniasis in the New World.
Helicobacter pylori
VacA Toxin Promotes Bacterial Intracellular Survival in Gastric Epithelial Cells
Authors: Terebiznik M. R. , Vazquez C. L. , Torbicki K. , Banks D. , Wang T. , Hong W. , Blanke S. R. , Colombo M. I. , Jones N. L. 
Published: November 2006

ABSTRACT

Helicobacter pylori
colonizes the gastric epithelium of at least 50% of the world's human population, playing a causative role in the development of chronic gastritis, peptic ulcers, and gastric adenocarcinoma. Current evidence indicates that
H. pylori
can invade epithelial cells in the gastric mucosa. However, relatively little is known about the biology of
H. pylori
invasion and survival in host cells. Here, we analyze both the nature of and the mechanisms responsible for the formation of
H. pylori
's intracellular niche. We show that in AGS cells infected with
H. pylori
, bacterium-containing vacuoles originate through the fusion of late endocytic organelles. This process is mediated by the VacA-dependent retention of the small GTPase Rab7. In addition, functional interactions between Rab7 and its downstream effector, Rab-interacting lysosomal protein (RILP), are necessary for the formation of the bacterial compartment since expression of mutant forms of RILP or Rab7 that fail to bind each other impaired the formation of this unique bacterial niche. Moreover, the VacA-mediated sequestration of active Rab7 disrupts the full maturation of vacuoles as assessed by the lack of both colocalization with cathepsin D and degradation of internalized cargo in the
H. pylori
-containing vacuole. Based on these findings, we propose that the VacA-dependent isolation of the
H. pylori
-containing vacuole from bactericidal components of the lysosomal pathway promotes bacterial survival and contributes to the persistence of infection.
Effect of Different Forms of Adenylate Cyclase Toxin ofBordetella pertussison Protection Afforded by an Acellular Pertussis Vaccine in a Murine Model
Authors: Cheung Gordon Y. C. , Xing Dorothy , Prior Sandra , Corbel Michael J. , Parton Roger , Coote John G. 
Published: November 2006

ABSTRACTFour recombinant forms of the cell-invasive adenylate cyclase toxin (CyaA) ofBordetella pertussiswere compared for the ability to enhance protection againstB. pertussisin mice when coadministered with an acellular pertussis vaccine (ACV). The four forms were as follows: fully functional CyaA, a CyaA form lacking adenylate cyclase enzymatic activity (CyaA*), and the nonacylated forms of these toxins, i.e., proCyaA and proCyaA*, respectively. None of these forms alone conferred significant (P> 0.05) protection againstB. pertussisin a murine intranasal challenge model. Mice immunized with ACV alone showed significant (P< 0.05) reductions in bacterial numbers in the lungs after intranasal challenge compared with those for control mice. When administered with ACV, both CyaA and CyaA* further reduced bacterial numbers in the lungs of mice after intranasal challenge compared with those for ACV-immunized mice, but the enhanced protection was only significant (P< 0.05) with CyaA*. Coadministration of CyaA* with ACV caused a significant (P< 0.05) increase in immunoglobulin G2a antibody levels against pertactin compared with those in mice immunized with ACV alone. Spleen cells from mice immunized with ACV plus CyaA* secreted larger amounts of interleukin-5 (IL-5), IL-6, gamma interferon (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than did cells from mice immunized with ACV plus CyaA or ACV alone after stimulation in vitro with a mixture ofB. pertussisantigens. Spleen cells from mice immunized with ACV plus CyaA* also secreted larger amounts of IFN-γ and GM-CSF than did cells from mice immunized with CyaA* alone after stimulation in vitro with CyaA*. Macrophages from mice immunized with ACV plus CyaA* produced significantly (P< 0.05) higher levels of nitric oxide than did macrophages from mice immunized with CyaA* alone, ACV alone, or ACV plus CyaA after stimulation in vitro with a mixture ofB. pertussisantigens or heat-killedB. pertussiscells. These data suggest that the enhancement of protection provided by CyaA* was due to an augmentation of both Th1 and Th2 immune responses toB. pertussisantigens.
Mycobacterium avium
subsp.
paratuberculosis
PtpA Is an Endogenous Tyrosine Phosphatase Secreted during Infection
Authors: Bach Horacio , Sun Jim , Hmama Zakaria , Av-Gay Yossef 
Published: November 2006

ABSTRACT

Adaptive gene expression in prokaryotes is mediated by protein kinases and phosphatases. These regulatory proteins mediate phosphorylation of histidine or aspartate in two-component systems and serine/threonine or tyrosine in eukaryotic and eukaryote-like protein kinase systems. The genome sequence of
Mycobacterium avium
subsp.
paratuberculosis
, the causative agent of Johne's disease, does not possess a defined tyrosine kinase. Nevertheless, it encodes for protein tyrosine phosphatases. Here, we report that Map1985, is a functional low-molecular tyrosine phosphatase that is secreted intracellularly upon macrophage infection. This finding suggests that Map1985 might contribute to the pathogenesis of
Mycobacterium avium
subsp.
paratuberculosis
by dephosphorylating essential macrophage signaling and/or adaptor molecules.
Mutation of the Maturase Lipoprotein Attenuates the Virulence ofStreptococcus equito a Greater Extent than Does Loss of General Lipoprotein Lipidation
Authors: Hamilton Andrea , Robinson Carl , Sutcliffe Iain C. , Slater Josh , Maskell Duncan J. , Davis-Poynter Nick , Smith Ken , Waller Andrew , Harrington Dean J. 
Published: November 2006

ABSTRACTStreptococcus equiis the causative agent of strangles, a prevalent and highly contagious disease of horses. Despite the animal suffering and economic burden associated with strangles, little is known about the molecular basis ofS. equivirulence. Here we have investigated the contributions of a specific lipoprotein and the general lipoprotein processing pathway to the abilities ofS. equito colonize equine epithelial tissues in vitro and to cause disease in both a mouse model and the natural host in vivo. Colonization of air interface organ cultures after they were inoculated with a mutant strain deficient in the maturase lipoprotein (ΔprtM138-213, with a deletion of nucleotides 138 to 213) was significantly less than that for cultures infected with wild-typeS. equistrain 4047 or a mutant strain that was unable to lipidate preprolipoproteins (Δlgt190-685). Moreover, mucus production was significantly greater in both wild-type-infected and Δlgt190-685-infected organ cultures. Both mutants were significantly attenuated compared with the wild-type strain in a mouse model of strangles, although 2 of 30 mice infected with the Δlgt190-685mutant did still exhibit signs of disease. In contrast, only the ΔprtM138-213mutant was significantly attenuated in a pony infection study, with 0 of 5 infected ponies exhibiting pathological signs of strangles compared with 4 of 4 infected with the wild-type and 3 of 5 infected with the Δlgt190-685mutant. We believe that this is the first study to evaluate the contribution of lipoproteins to the virulence of a gram-positive pathogen in its natural host. These data suggest that the PrtM lipoprotein is a potential vaccine candidate, and further investigation of its activity and its substrate(s) are warranted.
Chlamydial Protease-Like Activity Factor Induces Protective Immunity against Genital Chlamydial Infection in Transgenic Mice That Express the Human HLA-DR4 Allele
Authors: Murthy Ashlesh K. , Cong Yu , Murphey Cathi , Guentzel M. Neal , Forsthuber Thomas G. , Zhong Guangming , Arulanandam Bernard P. 
Published: November 2006

ABSTRACT

There is no licensed vaccine available against
Chlamydia trachomatis
, the leading cause of bacterial sexually transmitted disease. We have found that intranasal immunization with recombinant chlamydial protease-like activity factor (CPAF) induces CD4
+
T-cell- and gamma interferon (IFN-γ)-dependent protective immunity against murine genital chlamydial infection, thus making CPAF a viable vaccine candidate for further characterization. HLA-DR4 is the predominant allele involved in chlamydial antigen presentation to CD4
+
T cells in humans. We used engineered mice that lack endogenous major histocompatibility complex class II (MHC-II) alleles but express a human HLA allele (HLA-DR4 transgenic [tg] mice) to examine primary immune and CPAF-mediated responses against genital
Chlamydia muridarum
challenge. Upon primary bacterial exposure, HLA-DR4 tg mice developed
Chlamydia
-specific IFN-γ and antibody production and resolved the infection within 30 days, similar to challenged conventional C57BL/6 animals. Moreover,
C. muridarum
-challenged HLA-DR4 tg mice exhibited CPAF-specific antibody and IFN-γ production. Upon CPAF-plus-interleukin-12 (IL-12) vaccination, HLA-DR4 tg animals exhibited robust CPAF-specific IFN-γ production and elevated titers of anti-CPAF total antibody and immunoglobulin G2a (IgG2a) and lower titers of IgG2b and IgG1 antibodies. HLA-DR4 tg and C57BL/6 mice vaccinated with CPAF plus IL-12 resolved the primary genital chlamydial infection significantly earlier than mock-immunized animals, whereas similarly vaccinated MHC class II-deficient mice displayed minimal antigen-specific immune responses and failed to resolve the infection even at 30 days postchallenge. Together, these results demonstrate the importance of human HLA-DR4 molecules in the recognition and presentation of CPAF epitopes, leading to the generation of protective antichlamydial immunity and making these mice a valuable model for mapping HLA-DR4-restricted chlamydial epitopes.
A Linear Peptide Containing Minimal T- and B-Cell Epitopes ofPlasmodium falciparumCircumsporozoite Protein Elicits Protection against Transgenic Sporozoite Challenge
Authors: Calvo-Calle J. Mauricio , Oliveira Giane A. , Watta Carol Othoro , Soverow Jonathan , Parra-Lopez Carlos , Nardin Elizabeth H. 
Published: November 2006

ABSTRACTAn effective malaria vaccine is needed to address the public health tragedy resulting from the high levels of morbidity and mortality caused byPlasmodiumparasites. The first protective immune mechanism identified in the irradiated sporozoite vaccine, the “gold standard” for malaria preerythrocytic vaccines, was sporozoite-neutralizing antibody specific for the repeat region of the surface circumsporozoite (CS) protein. Previous phase I studies demonstrated that a branched peptide containing minimal T- and B-cell epitopes ofPlasmodium falciparumCS protein elicited antirepeat antibody and CD4+-T-cell responses comparable to those observed in volunteers immunized with irradiatedP. falciparumsporozoites. The current study compares the immunogenicity of linear versus tetrabranched peptides containing the same minimal T- and B-cell epitopes, T1BT*, comprised of a CS-derived universal Th epitope (T*) synthesized in tandem with the T1 and B repeats ofP. falciparumCS protein. A simple 48-mer linear synthetic peptide was found to elicit antisporozoite antibody and gamma interferon-secreting T-cell responses comparable to the more complex tetrabranched peptides in inbred strains of mice. The linear peptide was also immunogenic in outbred nonhuman primates (Aotus nancymaae), eliciting antibody titers equivalent to those induced by tetrabranched peptides. Importantly, the 48-mer linear peptide administered in adjuvants suitable for human use elicited antibody-mediated protection against challenge with rodent malaria transgenic sporozoites expressingP. falciparumCS repeats. These findings support further evaluation of linear peptides as economical, safe, and readily produced malaria vaccines for the one-third of the world's population at risk of malaria infection.
Limited Cross-Reactivity among Domains of the
Plasmodium falciparum
Clone 3D7 Erythrocyte Membrane Protein 1 Family
Authors: Joergensen Louise , Turner Louise , Magistrado Pamela , Dahlbäck Madeleine A. , Vestergaard Lasse S. , Lusingu John P. , Lemnge Martha , Salanti Ali , Theander Thor G. , Jensen Anja T. R. 
Published: November 2006

ABSTRACT

The
var
gene-encoded
Plasmodium falciparum
erythrocyte membrane protein 1 (PfEMP1) family is responsible for antigenic variation and sequestration of infected erythrocytes during malaria. We have previously grouped the 60 PfEMP1 variants of
P. falciparum
clone 3D7 into groups A and B/A (category A) and groups B, B/C, and C (category non-A). Expression of category A molecules is associated with severe malaria, and that of category non-A molecules is associated with uncomplicated malaria and asymptomatic infection. Here we assessed cross-reactivity among 60 different recombinant PfEMP1 domains derived from clone 3D7 by using a competition enzyme-linked immunosorbent assay and a pool of plasma from 63 malaria-exposed Tanzanian individuals. We conclude that naturally acquired antibodies are largely directed toward epitopes varying between different domains with a few, mainly category A, domains sharing cross-reactive antibody epitopes. Identification of groups of serological cross-reacting molecules is pivotal for the development of vaccines based on PfEMP1.
Helicobacter pylori
HP1512 Is a Nickel-Responsive NikR-Regulated Outer Membrane Protein
Authors: Davis Gregg S. , Flannery Erika L. , Mobley Harry L. T. 
Published: November 2006

ABSTRACT

Helicobacter pylori
is dependent upon the production of the highly abundant and active metalloenzyme urease for colonization of the human stomach. Thus,
H. pylori
has an absolute requirement for the transition metal nickel, a required cofactor for urease. To investigate the contribution of genes that are factors in this process, microarray analysis comparing the transcriptome of wild-type
H. pylori
26695 cultured in brucella broth containing fetal calf serum (BBF) alone or supplemented with 100 μM NiCl
2
suggested that HP1512 is repressed in the presence of 100 μM supplemental nickel. When measured by comparative real-time quantitative PCR (qPCR), HP1512 transcription was reduced 43-fold relative to the value for the wild type when cultured in BBF supplemented with 10 μM NiCl
2
. When grown in unsupplemented BBF, urease activity of an HP1512::
cat
mutant was significantly reduced compared to the wild type, 4.9 ± 0.5 μmol/min/mg of protein (
n
= 7) and 17.1 ± 4.9 μmol/min/mg of protein (
n
= 13), respectively (
P
< 0.0001). In silico analysis of the HP1511-HP1512 (HP1511-1512) intergenic region identified a putative NikR operator upstream of HP1512. Gel shift analysis with purified recombinant NikR verified nickel-dependent binding of
H. pylori
NikR to the HP1511-1512 intergenic region. Furthermore, comparative real-time qPCR of four nickel-related genes suggests that mutation of HP1512 results in reduced intracellular nickel concentration relative to wild-type
H. pylori
26695. Taken together, these data suggest that HP1512 encodes a NikR-nickel-regulated outer membrane protein.
NikR Mediates Nickel-Responsive Transcriptional Repression of the
Helicobacter pylori
Outer Membrane Proteins FecA3 (HP1400) and FrpB4 (HP1512)
Authors: Ernst Florian D. , Stoof Jeroen , Horrevoets Wannie M. , Kuipers Ernst J. , Kusters Johannes G. , van Vliet Arnoud H. M. 
Published: November 2006

ABSTRACT

The transition metal nickel plays an important role in gastric colonization and persistence of the important human pathogen
Helicobacter pylori
, as it is the cofactor of the abundantly produced acid resistance factor urease. Nickel uptake through the inner membrane is mediated by the NixA protein, and the expression of NixA is controlled by the NikR regulatory protein. Here we report that NikR also controls the nickel-responsive expression of the FecA3 (HP1400) and FrpB4 (HP1512) outer membrane proteins (OMPs), as well as the nickel-responsive expression of an ExbB-ExbD-TonB system, which may function in energization of outer membrane transport. Transcription and expression of the
frpB4
and
fecA3
genes were repressed by nickel in wild-type
H. pylori
26695, but they were independent of nickel and derepressed in an isogenic
nikR
mutant. Both the
frpB4
and
fecA3
genes were transcribed from a promoter directly upstream of their start codon. Regulation by NikR was mediated via nickel-dependent binding to specific operators overlapping either the +1 or −10 sequence in the
frpB4
and
fecA3
promoters, respectively, and these operators contained sequences resembling the proposed
H. pylori
NikR recognition sequence (TATWATT-N
11
-AATWATA). Transcription of the HP1339-1340-1341 operon encoding the ExbB2-ExbD2-TonB2 complex was also regulated by nickel and NikR, but not by Fur and iron. In conclusion,
H. pylori
NikR controls nickel-responsive expression of the HP1400 (FecA3) and HP1512 (FrpB4) OMPs. We hypothesize that these two NikR-regulated OMPs may participate in the uptake of complexed nickel ions and that this process is energized by the NikR-regulated ExbB2-ExbD2-TonB2 system, another example of the specific adaptation of
H. pylori
to the gastric lifestyle.