bluuebunny/crossref_metadata_2025_split huggingface dataset:
RgpA-Kgp Peptide-Based Immunogens Provide Protection againstPorphyromonas gingivalisChallenge in a Murine Lesion Model
Authors: O'Brien-Simpson Neil M. , Paolini Rita A. , Reynolds Eric C. 
Published: July 2002

ABSTRACTPorphyromonas gingivalis, a gram-negative bacterium, has been linked to the onset and progression of periodontitis, a chronic inflammatory disease of the supporting tissues of the teeth. A major virulence factor ofP. gingivalisis an extracellular complex of Arg- and Lys-specific proteinases and adhesins designated the RgpA-Kgp complex (formerly the PrtR-PrtK complex). In this study we show that the RgpA-Kgp complex, when used as an immunogen with incomplete Freund adjuvant (IFA), protects against challenge with invasive and noninvasive strains ofP. gingivalisin the murine lesion model. We identified a variety of peptide vaccine candidates from the RgpA and Kgp polyprotein sequences that involved the putative active site histidine of both proteinases and five repeat motifs in the adhesin domains of both polyproteins implicated in aggregation and binding to host substrates, designated adhesin-binding motif (ABM) peptides. These peptides were synthesized using standard, solid-phase protocols for 9-fluorenylmethoxy carbonyl chemistry withS-acetylmercaptoacetic acid (SAMA) as the N-terminal residue. The SAMA-peptides were then conjugated to diphtheria toxoid and used with IFA to immunize BALB/c mice. Both active-site peptides and three of the five ABM peptides gave protection (P< 0.005) against challenge withP. gingivalisin the murine lesion model. The three ABM peptide sequences that conferred protection exist within a 100-residue span in the RgpA44 and Kgp39 adhesins of the RgpA-Kgp complex. Protective anti-RgpA-Kgp complex mouse antisera recognized the RgpA27, Kgp39, and RgpA44 adhesins in an immunoblot. Epitope mapping of the RgpA27 adhesin using the protective anti-RgpA-Kgp antisera identified a major protective epitope that mapped immediately N terminal to one of the protective ABM peptides in the 100-residue span in RgpA44 and Kgp39. This identified protective epitope contains clusters of basic residues spatially surrounded by hydrophobic amino acids, a finding which is characteristic of a heparin binding motif.
Invasion of Human Epithelial Cells by
Pseudomonas aeruginosa
Involves Src-Like Tyrosine Kinases p60Src and p59Fyn
Authors: Esen Meral , Grassmé Heike , Riethmüller Joachim , Riehle Andrea , Fassbender Klaus , Gulbins Erich 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
plays a major role in respiratory tract infections or sepsis in patients with cystic fibrosis or upon suppression of the immune system. Several
P. aeruginosa
strains have been shown to be internalized by human epithelial cells; however, the molecular mechanisms of the invasion process are poorly characterized. Here, we show that the internalization of
P. aeruginosa
into human epithelial cells results in and requires activation of the Src-like tyrosine kinases p59Fyn and p60Src and the consequent tyrosine phosphorylation of several eukaryotic proteins. The significance of Src-like tyrosine kinase activation is shown by an almost complete blockade of
P. aeruginosa
internalization, but not adhesion, upon inhibition of Src-like tyrosine kinases. Likewise, inhibition of
P. aeruginosa
binding to CFTR, which has been shown to block
P. aeruginosa
internalization, prevents Src and Fyn activation, supporting a pivotal role of Src-like tyrosine kinases for invasion by
P. aeruginosa.
Dendritic Cells Phagocytose and Are Activated byTreponema pallidum
Authors: Bouis Deborah A. , Popova Taissia G. , Takashima Akira , Norgard Michael V. 
Published: July 2002

ABSTRACTCell-mediated immune processes play a prominent role in the clinical manifestations of syphilis, a sexually transmitted disease of humans caused by spirochetal bacteriumTreponema pallidum. The immune cell type that initiates the early immune response toT. pallidumthus far has not been identified. However, dendritic cells (DCs) are the first immune-competent cells to encounter antigens within skin or mucous membranes, the principal sites of early syphilitic infection. In the present study, immature DC line XS52, derived from murine skin, was utilized to examineT. pallidum-DC interactions and subsequent DC activation (maturation). Electron microscopy revealed thatT. pallidumwas engulfed by DCs via both coiling and conventional phagocytosis and was delivered to membrane-bound vacuoles. The XS52 DC line expressed surface CD14 and mRNA for Toll-like receptors 2 and 4, molecules comprising important signaling components for immune cell activation by bacterial modulins. BothT. pallidumand a synthetic lipopeptide (corresponding to the 47-kDa major membrane lipoprotein) activated the XS52 DC line, as indicated by the secretion of interleukin-12 (IL-12), IL-1β, tumor necrosis factor alpha, and IL-6 and elevated surface expression of CD54. The combined data support the contention that DCs stimulated byT. pallidumand/or its proinflammatory membrane lipoproteins are involved in driving the cellular immune processes that typify syphilis.
Characterization of the Enzymatic Component of the ADP-Ribosyltransferase Toxin CDTa from
Clostridium difficile
Authors: Gülke Irene , Pfeifer Gunther , Liese Jan , Fritz Michaela , Hofmann Fred , Aktories Klaus , Barth Holger 
Published: July 2002

ABSTRACT

Certain strains of
Clostridium difficile
produce the ADP-ribosyltransferase CDT, which is a binary actin ADP-ribosylating toxin. The toxin consists of the binding component CDTb, which mediates receptor binding and cellular uptake, and the enzyme component CDTa. Here we studied the enzyme component (CDTa) of the toxin using the binding component of
Clostridium perfringens
iota toxin (Ib), which is interchangeable with CDTb as a transport component. Ib was used because CDTb was not expressed as a recombinant protein in
Escherichia coli
. Similar to iota toxin, CDTa ADP-ribosylates nonmuscle and skeletal muscle actin. The N-terminal part of CDTa (CDTa
1–240
) competes with full-length CDTa for binding to the iota toxin binding component. The C-terminal part (CDTa
244–263
) harbors the enzyme activity but was much less active than the full-length CDTa. Changes of Glu428 and Glu430 to glutamine, Ser388 to alanine, and Arg345 to lysine blocked ADP-ribosyltransferase activity. Comparison of CDTa with
C. perfringens
iota toxin and
Clostridium botulinum
C2 toxin revealed full enzyme activity of the fragment Ia
208–413
but loss of activity of several N-terminally deleted C2I proteins including C2I
103–431
, C2I
190–431
, and C2I
30–431
. The data indicate that CDTa belongs to the iota toxin subfamily of binary actin ADP-ribosylating toxins with respect to interaction with the binding component and substrate specificity. It shares typical conserved amino acid residues with iota toxin and C2 toxin that are suggested to be involved in NAD-binding and/or catalytic activity. The enzyme components of CDT, iota toxin, and C2 toxin differ with respect to the minimal structural requirement for full enzyme activity.
Regulation of Expression of Major Histocompatibility Antigens by Bovine Macrophages Infected withMycobacterium aviumsubsp.paratuberculosisorMycobacterium aviumsubsp.avium
Authors: Weiss Douglas J. , Evanson Oral A. , McClenahan David J. , Abrahamsen Mitchell S. , Walcheck Bruce K. 
Published: July 2002

ABSTRACTMycobacterium aviumsubsp.paratuberculosisandMycobacterium aviumsubsp.aviumare antigenically and genetically very similar organisms; however, they differ markedly in their virulence for cattle. We evaluated the capacity of bovine macrophages infected withM. aviumsubsp.paratuberculosisorM. aviumsubsp.aviumto express major histocompatibility complex (MHC) class I and class II antigens on their surface and to interact with primed autologous lymphocytes. Our results indicate that infection of bovine macrophages withM. aviumsubsp.paratuberculosispromoted the downregulation of MHC class I and class II molecules on the macrophage surface within 24 and 12 h, respectively. Alternatively, MHC class II expression byM. aviumsubsp.avium-infected macrophages was not detected until 24 h after infection, and the magnitude of the decrease was smaller. Decreased MHC class I expression byM. aviumsubsp.avium-infected macrophages was not detected. UnlikeM. aviumsubsp.paratuberculosis-infected macrophages,M. aviumsubsp.avium-infected macrophages upregulated MHC class I and class II expression after activation by gamma interferon or tumor necrosis factor alpha. Further,M. aviumsubsp.avium-infected macrophages were lysed by primed autologous lymphocytes, whereasM. aviumsubsp.paratuberculosis-infected macrophages were not. Overall, the results support the hypothesis that the difference in the virulence ofM. aviumsubsp.paratuberculosisandM. aviumsubsp.aviumfor cattle is dependent on a difference in the capacity of the organisms to suppress mycobacterial antigen presentation to T lymphocytes.
Role of T Cells and Gamma Interferon during Induction of Hypersensitivity to Lipopolysaccharide by Toxic Shock Syndrome Toxin 1 in Mice
Authors: Dinges Martin M. , Schlievert Patrick M. 
Published: July 2002

ABSTRACTThe superantigenic function of toxic shock syndrome toxin 1 (TSST-1) is generally regarded as an important determinant of its lethal effects in humans or experimental animals. This study examined the role of superantigenicity in a BALB/c mouse model of lethal TSST-1-induced hypersensitivity to lipopolysaccharide (LPS). In this model, TSST-1 greatly potentiated both LPS-induced lethality, as well as LPS-induced serum tumor necrosis factor alpha (TNF-α) activity. Although BALB/c-SCID mice were resistant to these LPS enhancement effects of TSST-1, BALB/c-SCID mice reconstituted with T cells were completely susceptible to the enhancement effect of TSST-1 on LPS-induced serum TNF-α. Mice pretreated with cyclosporine (Cs) or neutralizing antibodies against gamma interferon (IFN-γ) did not develop lethal LPS hypersensitivity when injected with TSST-1, and these agents reduced the enhancement effect of TSST-1 on LPS-induced serum TNF-α by 99 and 85%, respectively. Cs pretreatment also completely inhibited the known capacity of TSST-1 to amplify LPS-induced levels of IFN-γ in serum. In contrast, mice given Cs after a priming injection of TSST-1, but before LPS, still exhibited lethal hypersensitivity to LPS. Cs given after TSST-1 also did not inhibit enhancement of LPS-induced serum TNF-α by TSST-1 but inhibited the enhancement effect of TSST-1 on LPS-induced serum IFN-γ by 50%. These experiments support the theory that TSST-1-induced hypersensitivity to LPS is mediated primarily by IFN-γ derived from superantigen-activated T cells.
Nme
SI Restriction-Modification System Identified by Representational Difference Analysis of a Hypervirulent
Neisseria meningitidis
Strain
Authors: Bart Aldert , Pannekoek Yvonne , Dankert Jacob , van der Ende Arie 
Published: July 2002

ABSTRACT

Neisseria meningitidis
is a gram-negative bacterium that may cause meningitis, sepsis, or both. The increase in the incidence of meningococcal disease in various countries in the past 2 decades is mainly due the genotypically related lineage III meningococci. The chromosomal DNA differences between lineage III strains and non-lineage III strains were identified using representational difference analysis. Thus, a 1.8-kb locus that is specific for lineage III meningococci was identified. The locus contains three open reading frames encoding the
Nme
SI restriction-modification system. The methyltransferase gene was cloned and expressed in
Escherichia coli
. Site AGTACT was found to be modified by the enzyme. In conclusion, lineage III strains differ from endemic strains by the presence of a specific restriction-modification system. This restriction-modification system may contribute to the clonal and hypervirulent character of lineage III strains by influencing horizontal gene transfer and transcription.
Acapsular
Pasteurella multocida
B:2 Can Stimulate Protective Immunity against Pasteurellosis
Authors: Boyce John D. , Adler Ben 
Published: July 2002

ABSTRACT

We have previously shown that a
Pasteurella multocida cexA
mutant (PBA875) was impaired in capsule export and highly attenuated in virulence for mice (J. D. Boyce and B. Adler, Infect. Immun. 68:3463–3468, 2000). In this study we show that immunization with high, but not low, doses of PBA875 can confer significant protection against wild-type challenge. We have also constructed a genetically defined acapsular
P. multocida
strain (AL18) by inactivation of
bcbH
, a gene predicted to be involved in polysaccharide biosynthesis. AL18 failed to produce immunoreactive polysaccharide as determined by immunofluorescence and Western immunoblot. Immunization of mice with live AL18 conferred significant protection against wild-type challenge, while immunization with similar doses of either killed wild-type or killed AL18 failed to confer protection.
Chemokine-Dependent Neutrophil Recruitment in a Murine Model ofLegionellaPneumonia: Potential Role of Neutrophils as Immunoregulatory Cells
Authors: Tateda Kazuhiro , Moore Thomas A. , Newstead Michael W. , Tsai Wan C. , Zeng Xianying , Deng Jane C. , Chen Gina , Reddy Raju , Yamaguchi Keizo , Standiford Theodore J. 
Published: July 2002

ABSTRACTThe roles of CXC chemokine-mediated host responses were examined with an A/J mouse model ofLegionella pneumophilapneumonia. After intratracheal inoculation of 106CFU ofL. pneumophila, the bacterial numbers in the lungs increased 10-fold by day 2; this increase was accompanied by the massive accumulation of neutrophils. Reverse transcription-PCR data demonstrated the up-regulation of CXC chemokines, such as keratinocyte-derived chemokine, macrophage inflammatory protein 2 (MIP-2), and lipopolysaccharide-induced CXC chemokine (LIX). Consistent with these data, increased levels of KC, MIP-2, and LIX proteins were observed in the lungs and peaked at days 1, 2, and 2, respectively. Although the administration of anti-KC or anti–MIP-2 antibody resulted in an approximately 20% decrease in neutrophil recruitment on day 2, no increase in mortality was observed. In contrast, the blockade of CXC chemokine receptor 2 (CXCR2), a receptor for CXC chemokines, including KC and MIP-2, strikingly enhanced mortality; this effect coincided with a 67% decrease in neutrophil recruitment. Interestingly, anti-CXCR2 antibody did not affect bacterial burden by day 2, even in the presence of a lethal challenge of bacteria. Moreover, a significant decrease in interleukin-12 (IL-12) levels, in contrast to the increases in KC, MIP-2, and LIX levels, was demonstrated for CXCR2-blocked mice. These data indicated that CXCR2-mediated neutrophil accumulation may play a crucial role in host defense againstL. pneumophilapneumonia in mice. The increase in lethality without a change in early bacterial clearance suggested that neutrophils may exert their protective effect not through direct killing but through more immunomodulatory actions inL. pneumophilapneumonia. We speculate that a decrease in the levels of the protective cytokine IL-12 may explain, at least in part, the high mortality in the setting of reduced neutrophil recruitment.
Fibronectin Attachment Protein Homologue Mediates Fibronectin Binding by
Mycobacterium avium
subsp.
paratuberculosis
Authors: Secott T. E. , Lin T. L. , Wu C. C. 
Published: July 2002

ABSTRACT

Attachment of
Mycobacterium avium
subsp.
paratuberculosis
to host tissue and penetration of mucosal surfaces are pivotal events in the pathogenesis of Johne's disease. Fibronectin (FN) binding is required for attachment and internalization of several mycobacteria by epithelial cells in vitro. The objective of this study was to further characterize the FN binding activity of
M. avium
subsp.
paratuberculosis
. Although the bacteria bound FN poorly at pH above 7, brief acid pretreatment greatly enhanced FN binding within the pH range (3 to 10) studied. A 4.6-kbp fragment from an
M. avium
subsp.
paratuberculosis
genomic library was found to contain a 1,107-bp open reading frame that shows very high nucleotide sequence identity with that of the FN attachment protein (FAP) gene of
M. avium
subsp.
avium
. Pretreatment of FN with an FN-binding peptide from
M. avium
subsp.
avium
FAP abolished FN binding, indicating that
M. avium
subsp.
paratuberculosis
binds FN in a FAP-dependent manner. Pretreatment of
M. avium
subsp.
paratuberculosis
with anti-FAP immunoglobulin G did not abrogate FN binding; blocking occurred only when anti-FAP was added together with FN. FAP was detected by immunofluorescence only in lipid-extracted
M. avium
subsp.
paratuberculosis
. Western blotting and immunoelectron microscopy revealed that FAP is located near the interior of the cell envelope of
M. avium
subsp.
paratuberculosis
. The results indicate that a FAP homologue mediates the attachment of FN to
M. avium
subsp.
paratuberculosis
. Further, given the subcellular location of FAP, it is considered that this protein operates at the terminus of a coordinated FN binding system in the cell envelope of
M. avium
subsp.
paratuberculosis
.
Activation of Endothelium byBorrelia burgdorferiIn Vitro Enhances Transmigration of Specific Subsets of T Lymphocytes
Authors: Gergel Edna I. , Furie Martha B. 
Published: July 2002

ABSTRACTLyme disease, caused byBorrelia burgdorferi, is characterized by the accumulation of lymphocytes and monocytes in the affected tissue. Endothelial cells line the blood vessel walls and control the trafficking of inflammatory leukocytes from the blood into the surrounding tissues. A model of the blood vessel wall, consisting of human umbilical vein endothelial cells (HUVEC) grown on amniotic connective tissue, was utilized to examine the effects ofB. burgdorferion the transendothelial migration of T lymphocytes. Maximal migration occurred when the HUVEC-amnion cultures were preincubated withB. burgdorferifor 24 h and T lymphocytes were added for an additional 4 h, yielding a two- to fourfold increase compared to migration across unstimulated cultures. The number of T lymphocytes that migrated was proportional to the number added. The anti-inflammatory cytokine interleukin 10 (IL-10), added during activation of the HUVEC, significantly diminished (by an average of 70% ± 21%) the migration of T lymphocytes across endothelium stimulated for 8 or 24 h withB. burgdorferi, but not IL-1. Compared to the initially added population of T lymphocytes, the population that migrated across untreated endothelium or HUVEC activated withB. burgdorferior IL-1 contained a significantly smaller percentage of CD45RA+RO−(naı̈ve) cells and a greater proportion of CD45RA+RO+cells. The migratory population was also enriched for CD8+T lymphocytes when the endothelium was incubated with either control medium orB. burgdorferi, but not IL-1.B. burgdorferithus activates endothelium in a manner that promotes the transmigration of T lymphocytes, and IL-10 inhibits this activation. These data further suggest that endothelium plays an active role in promoting the recruitment of specific subpopulations of T lymphocytes.
Resolution of SecondaryChlamydia trachomatisGenital Tract Infection in Immune Mice with Depletion of Both CD4+and CD8+T cells
Authors: Morrison Sandra G. , Morrison Richard P. 
Published: July 2002

ABSTRACTThe essential role of T cells in the resolution of primary murineChlamydia trachomatisgenital tract infection is inarguable; however, much less is known about the mechanisms that confer resistance to reinfection. We previously established that CD4+T cells and B cells contribute importantly to resistance to reinfection. In our current studies, we demonstrate that immune mice concurrently depleted of both CD4+T cells and CD8+T cells resisted reinfection as well as immunocompetent wild-type mice. The in vivo depletion of CD4+and CD8+T cells resulted in diminished chlamydia-specific delayed-type hypersensitivity responses, but antichlamydial antibody responses were unaffected. Our data indicate that immunity to chlamydial genital tract reinfection does not rely solely upon immune CD4+or CD8+T cells and further substantiate a predominant role for additional effector immune responses, such as B cells, in resistance to chlamydial genital tract reinfection.
Shigella Infection in a SCID Mouse-Human Intestinal Xenograft Model: Role for Neutrophils in Containing Bacterial Dissemination in Human Intestine
Authors: Zhang Zhi , Jin Lingling , Champion Gretchen , Seydel Karl B. , Stanley Samuel L. 
Published: July 2002

ABSTRACT
Shigellae infect human intestine and cause intense inflammation and destruction of colonic and rectal mucosa. To model the interactions of shigella with human intestine in vivo, we have studied shigella infection in human intestinal xenografts in severe combined immunodeficient mice (SCID-HU-INT mice). Inoculation of shigella into human intestinal xenografts caused severe inflammation and mucosal damage, which was apparent as soon as 4 h following infection. Shigella infection was associated with human intestinal production of interleukin-1B (IL-1B) and IL-8 and a marked neutrophil influx into the graft. Depletion of neutrophils from SCID-HU-INT mice reduced inflammation in the human intestinal xenograft in response to shigella infection but failed to significantly alter tissue damage. However, the number of intracellular bacteria was more than 20-fold higher in the human intestinal xenografts from neutrophil-depleted SCID-HU-INT mice. Infection of human intestinal xenografts with an attenuated vaccine strain of shigella (CVD1203) induced lower levels of IL-1B and IL-8 than wild-type shigella and caused only moderate damage to the intestinal permeability barrier. Our studies establish the SCID-HU-INT mouse as a viable model for studying the interactions between shigella and human intestine and indicate that neutrophils are important for controlling the invasion of human intestine by shigella.
Dissociation of Infectivity and Pathogenicity in
Borrelia burgdorferi
Authors: Thomas Venetta , Anguita Juan , Samanta Swapna , Rosa Patricia A. , Stewart Philip , Barthold Stephen W. , Fikrig Erol 
Published: July 2002

ABSTRACT

Clonal
Borrelia burgdorferi
N40 (cN40) passaged 75 times in vitro (N40-75) infects mice but does not cause disease. N40-75 passaged 45 times further in vitro (N40-120) was no longer infectious and lacked genes encoded on linear plasmids 38 and 28-1, among other differences. These data suggest that
B. burgdorferi
cN40, N40-75, and N40-120 have distinct phenotypes that can be used to dissect the genetic elements responsible for pathogenicity and infectivity.