bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effective In Vitro Clearance ofPorphyromonas gingivalisby Fcα Receptor I (CD89) on Gingival Crevicular Neutrophils
Authors: Kobayashi Tetsuo , Yamamoto Kouji , Sugita Noriko , van Spriel Annemiek B. , Kaneko Susumu , van de Winkel Jan G. J. , Yoshie Hiromasa 
Published: July 2002

ABSTRACTPorphyromonas gingivalishas been implicated as a causative pathogen in periodontitis. Immunotherapeutic approaches have recently been suggested to aid in the clearance ofP. gingivalisfrom disease sites. Because antibody-Fc receptor (FcR) interactions play a role in the effector functions of polymorphonuclear neutrophils (PMN), we evaluated which FcR on PMN from gingival crevicular fluid (GCF) serves as an optimal target molecule for FcR-directed immunotherapy. GCF PMN and peripheral blood (PB) PMN from adult periodontitis patients were analyzed for their immunoglobulin G (IgG) and IgA FcR (FcγR and FcαR, respectively) expression and function by studying IgG- and IgA-mediated elimination ofP. gingivalis. GCF PMN exhibited higher FcαRI and FcγRI levels and lower FcγRIIa and FcγRIIIb levels than PB PMN. Functional studies revealed that GCF PMN exhibited less of a capacity to phagocytose and kill IgG1-opsonizedP. gingivalisthan PB PMN. IgA1-mediated phagocytosis and killing capacity was, however, comparable between GCF PMN and PB PMN. In summary, these in vitro results document that FcαRI represents a candidate target for FcR-directed immunotherapy for the clearance ofP. gingivalis.
Antigenic Diversity among
Helicobacter pylori
Vacuolating Toxins
Authors: Vinion-Dubiel Arlene D. , McClain Mark S. , Cao Ping , Mernaugh Raymond L. , Cover Timothy L. 
Published: July 2002

ABSTRACT

Helicobacter pylori
vacuolating cytotoxin (VacA) is a secreted protein that induces vacuolation of epithelial cells. To study VacA structure and function, we immunized mice with purified type s1-m1 VacA from
H. pylori
strain 60190 and generated a panel of 10 immunoglobulin G1κ anti-VacA monoclonal antibodies. All of the antibodies reacted with purified native VacA but not with denatured VacA, suggesting that these antibodies react with conformational epitopes. Seven of the antibodies reacted with both native and acid-treated VacA, which suggests that epitopes present on both oligomeric and monomeric forms of the toxin were recognized. Two monoclonal antibodies, both reactive with epitopes formed by amino acids in the carboxy-terminal portion of VacA (amino acids 685 to 821), neutralized the cytotoxic activity of type s1-m1 VacA when toxin and antibody were mixed prior to cell contact but failed to neutralize the cytotoxic activity of type s1-m2 VacA. Only 3 of the 10 antibodies consistently recognized type s1-m1 VacA toxins from multiple
H. pylori
strains, and none of the antibodies recognized type s2-m2 VacA toxins. These results indicate that there is considerable antigenic diversity among VacA toxins produced by different
H. pylori
strains.
Primary and Booster Mucosal Immune Responses to Meningococcal Group A and C Conjugate and Polysaccharide Vaccines Administered to University Students in the United Kingdom
Authors: Zhang Q. , Lakshman R. , Burkinshaw R. , Choo S. , Everard J. , Akhtar S. , Finn A. 
Published: July 2002

ABSTRACTMeningococcal group A+C capsular polysaccharide (PS) conjugate vaccines may prime for serum immunoglobulin G (IgG) memory responses to meningococcal capsular PS. It is not known whether these vaccines induce immunological memory at the mucosal level, which may be important in reducing nasopharyngeal carriage. Mucosal immune responses to meningococcal conjugate and PS vaccines in young adults were investigated. Healthy university students were randomized to receive either a groups A+C meningococcal conjugate vaccine (MACconj,n= 100) or a group A+C meningococcal PS vaccine (MACPS,n= 95). One year after the primary immunization, both groups were randomized again to receive a MACconj or a MACPS booster vaccination. Saliva samples were collected before and 1 month after the primary and booster vaccinations. Anti-meningococcal A (MenA) and C (MenC) PS IgA and IgG antibody levels were measured by a standard enzyme-linked immunosorbent assay. After the primary vaccination, salivary MenA and MenC IgG and MenA IgA concentrations were significantly increased after immunization with both MACconj and MACPS vaccines, but the salivary Men C IgA level was increased only after MACPS vaccine (P< 0.01). IgA responses to both serogroups were greater for MACPS than MACconj vaccine (P< 0.05), whereas no significant differences were seen for IgG responses. MenA IgG titers were higher after the MACPS booster in MACconj-primed subjects than after the MACPS primary vaccination, suggesting the presence of IgG memory. Antibody responses to a dose of either MACPS or MACconj were not significantly reduced in those previously given MACPS compared to the primary responses to those vaccines. Meningococcal A+C conjugate and PS vaccines induce significant mucosal responses in young adults. MACconj priming may induce IgG memory at the mucosal level, which is likely to be a reflection of an anamnestic serum IgG response. No evidence of mucosal hyporesponsiveness was observed after MACPS priming in this study.
In Vitro and In Vivo Assessment ofSalmonella entericaSerovar Typhimurium DT104 Virulence
Authors: Allen Chris A. , Fedorka-Cray Paula J. , Vazquez-Torres Andrés , Suyemoto Mitsu , Altier Craig , Ryder L. Reeni , Fang Ferric C. , Libby Stephen J. 
Published: July 2002

ABSTRACTMultidrug-resistantSalmonella entericaserovar Typhimurium phage type DT104 has become a widespread cause of human and other animal infection worldwide. The severity of clinical illness inS. entericaserovar Typhimurium DT104 outbreaks has led to the suggestion that this strain possesses enhanced virulence. In the present study, in vitro and in vivo virulence-associated phenotypes of several clinical isolates ofS. entericaserovar Typhimurium DT104 were examined and compared toS. entericaserovar Typhimurium ATCC 14028s. The ability of these DT104 isolates to survive within murine peritoneal macrophages, invade cultured epithelial cells, resist antimicrobial actions of reactive oxygen and nitrogen compounds, and cause lethal infection in mice were assessed. Our results failed to demonstrate thatS. entericaserovar Typhimurium DT104 isolates are more virulent thanS. entericaserovar Typhimurium ATCC 14028s.
Contribution of Mn-Cofactored Superoxide Dismutase (SodA) to the Virulence of
Streptococcus agalactiae
Authors: Poyart Claire , Pellegrini Elisabeth , Gaillot Olivier , Boumaila Claire , Baptista Marina , Trieu-Cuot Patrick 
Published: July 2002

ABSTRACT

Superoxide dismutases convert superoxide anions to molecular oxygen and hydrogen peroxide, which, in turn, is metabolized by catalases and/or peroxidases. These enzymes constitute one of the major defense mechanisms of cells against oxidative stress and hence play a role in the pathogenesis of certain bacteria. We previously demonstrated that group B streptococci (GBS) possess a single Mn-cofactored superoxide dismutase (SodA). To analyze the role of this enzyme in the pathogenicity of GBS, we constructed a
sodA
-disrupted mutant of
Streptococcus agalactiae
NEM316 by allelic exchange. This mutant was subsequently
cis
complemented by integration into the chromosome of pAT113/Sp harboring the wild-type
sodA
gene. The SOD specific activity detected by gel analysis in cell extracts confirmed that active SODs were present in the parental and complemented strains but absent in the
sodA
mutant. The growth rates of these strains in standing cultures were comparable, but the
sodA
mutant was extremely susceptible to the oxidative stress generated by addition of paraquat or hydrogen peroxide to the culture medium and exhibited a higher mutation frequency in the presence of rifampin. In mouse bone marrow-derived macrophages, the
sodA
mutant showed an increased susceptibility to bacterial killing by macrophages. In a mouse infection model, after intravenous injection the survival of the
sodA
mutant in the blood and the brain was markedly reduced in comparison to that of the parental and complemented strains whereas only minor effects on survival in the liver and the spleen were observed. These results suggest that SodA plays a role in GBS pathogenesis.
ADP-Ribosylation of Rab5 by ExoS of
Pseudomonas aeruginosa
Affects Endocytosis
Authors: Barbieri Alejandro M. , Sha Qun , Bette-Bobillo Pascale , Stahl Philip D. , Vidal Michel 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
exoenzyme S (ExoS) is an ADP-ribosyltransferase that modifies low-molecular-weight GTPases. Here we studied the effect of Rab5 ADP-ribosylation by ExoS on its cellular function, i.e., regulation of early endocytic events. Coculture of CHO cells with
P. aeruginosa
induced a marked decrease in horseradish peroxidase (HRP) uptake compared to noninfected cells, while coculture with a
P. aeruginosa
mutant strain that fails to produce ExoS did not lead to any change in HRP uptake. Microinjection of recombinant ExoS into
Xenopus
oocytes induced strong inhibition of basal HRP uptake by oocytes. Moreover, coinjection of recombinant ExoS with Rab5 abolished the typical stimulation of HRP uptake obtained after GTPase microinjection. Cytosols prepared from injected oocytes were used in an endosome-endosome fusion assay. Cytosol from ExoS-microinjected oocytes was ineffective in promoting endosome-endosome fusion. However, in these conditions, the addition of Rab5 to the assay led to fusion recovery. Finally, we found that the interaction of Rab5 with EEA1 was markedly diminished after Rab5 ADP-ribosylation by ExoS.
Isolation and Characterization of a Mutant Chinese Hamster Ovary Cell Line That Is Resistant to
Chlamydia trachomatis
Infection at a Novel Step in the Attachment Process
Authors: Carabeo Reynaldo A. , Hackstadt Ted 
Published: July 2002

ABSTRACT

Host factors involved in
Chlamydia trachomatis
pathogenesis were investigated by random chemical mutagenesis of Chinese hamster ovary (CHO-K1) cells followed by selection for clones resistant to chlamydial infection. A clonal mutant cell line, D4.1–3, refractory to infection by the
C. trachomatis
L2 serovar was isolated. The D4.1–3 cell line appears to be lacking in a previously undescribed temperature-dependent and heparin-resistant binding step that occurs subsequent to engagement of cell surface heparan sulfate by L2 elementary bodies. This novel binding step differentiates the lymphogranuloma venereum (LGV) serovar from other serovars and may contribute the different pathologies associated with LGV and non-LGV strains.
Characterization of a Cytotoxic Factor in Culture Filtrates of
Serratia marcescens
Authors: Marty Kent B. , Williams Christopher L. , Guynn Linda J. , Benedik Michael J. , Blanke Steven R. 
Published: July 2002

ABSTRACT

Serratia marcescens
culture filtrates have been reported to be cytotoxic to mammalian cells. Using biochemical and genetic approaches, we have identified a major source of this cytotoxic activity. Both heat and protease treatments abrogated the cytotoxicity of
S. marcescens
culture filtrates towards HeLa cells, suggesting the involvement of one or more protein factors. A screen for in vitro cytotoxic activity revealed that
S. marcescens
mutant strains that are deficient in production of a 56-kDa metalloprotease are significantly less cytotoxic to mammalian cells. Cytotoxicity was significantly reduced when culture filtrates prepared from wild-type strains were pretreated with either EDTA or 1,10-phenanthroline, which are potent inhibitors of the 56-kDa metalloprotease. Furthermore, cytotoxic activity was restored when the same culture filtrates were incubated with zinc divalent cations, which are essential for enzymatic activity of the 56-kDa metalloprotease. Finally, recombinant expression of the
S. marcescens
56-kDa metalloprotease conferred a cytotoxic phenotype on the culture filtrates of a nonpathogenic
Escherichia coli
strain. Collectively, these data suggest that the 56-kDa metalloprotease contributes significantly to the in vitro cytotoxic activity commonly observed in
S. marcescens
culture filtrates.
Extracellular Antigens fromSalmonella enteritidisInduce Effective Immune Response in Mice after Oral Vaccination
Authors: Strindelius Lena , Wikingsson Lena Degling , Sjöholm Ingvar 
Published: July 2002

ABSTRACTWe have studied polyacryl starch microparticles as an adjuvant in oral vaccination in mice. Secreted antigens fromSalmonella entericaserovar Enteritidis were administered covalently conjugated to microparticles, or as free antigens, orally or intramuscularly and evaluated for their immunogenicity and ability to elicit protective immune response against an oral challenge with live serovar Enteritidis. The highest immunoglobulin M (IgM)-plus-IgG titers were obtained in the groups immunized with antigen-conjugated microparticles. The subclass profile switched to a stronger Th1 influence in the oral groups after booster, while the intramuscular group showed a constant Th1/Th2 profile. A strong specific IgA response was seen in feces in the oral groups, which was further confirmed in an enzyme-linked immunospot assay. The delayed-type hypersensitivity test, as a measure of the cellular response, showed a significant increase in ear thickness in all the immunized groups, except for the group that received free antigen orally, compared to the nonimmunized group. The cytokines released from in vitro-stimulated spleens showed a strong gamma interferon response in all immunized groups. A significant reduction in CFU in liver and spleen was seen in the orally immunized groups compared to the nonimmunized group after oral challenge with serovar Enteritidis. Western blotting analysis with both sera and feces revealed that antibodies against three bands, 53, 56, and 60 kDa, dominated the oral groups, and an electrospray-mass spectroscopy analysis of these bands showed amino acid sequences coinciding with those of phase-1 flagellin and hook-associated protein 2.
Role of Pneumococcal Surface Protein C in Nasopharyngeal Carriage and Pneumonia and Its Ability To Elicit Protection against Carriage of
Streptococcus pneumoniae
Authors: Balachandran Priya , Brooks-Walter Alexis , Virolainen-Julkunen Anni , Hollingshead Susan K. , Briles David E. 
Published: July 2002

ABSTRACT

Previous studies suggested that PspC is important in adherence and colonization within the nasopharynx. In this study, we conducted mutational studies to further identify the role PspC plays in the pathogenesis of pneumococci.
pspC
and/or
pspA
was insertionally inactivated in a serotype 2
Streptococcus pneumoniae
strain and in a serotype 19
S. pneumoniae
strain. In the mouse colonization model, pneumococcal strains with mutations in
pspC
were significantly attenuated in their abilities to colonize. In a mouse pneumonia model, strains with mutations in
pspC
were unable to infect or multiply within the lung. Using reverse transcriptase PCR we were able to demonstrate that
pspC
is actively transcribed in vivo, when the bacteria are growing in the nasal cavity and in the lungs. In the bacteremia model, a strain mutated for
pspC
alone behaved like the wild type, but the absence of both
pspC
and
pspA
caused accelerated clearance of the bacteria. Intranasal immunization with PspC with cholera toxin subunit B as an adjuvant protected against intranasal challenge. Evidence was also obtained that revertants that spontaneously acquired PspC expression could multiply and colonize the nasal tissue. This latter finding strongly indicates that pneumococci are actively metabolizing and growing while in the nasopharynx.
Monocyte Differentiation in Localized Juvenile Periodontitis Is Skewed toward the Dendritic Cell Phenotype
Authors: Barbour Suzanne E. , Ishihara Yuichi , Fakher Mohammed , Al-Darmaki Salma , Caven Timothy H. , Shelburne C. P. , Best Al M. , Schenkein Harvey A. , Tew John G. 
Published: July 2002

ABSTRACTSeveral lines of evidence indicate that the monocytes of subjects with localized juvenile periodontitis (LJP) are functionally distinct from cells of age- and race-matched nonperiodontitis (NP) subjects. Among the abnormalities are the propensity to secrete large amounts of prostaglandin E2and the induction of immunoglobulin G2 (IgG2) antibodies. The experiments described here were performed to further characterize the LJP monocytes and to determine if these cells mature differently than NP monocytes. When adherent monocytes from LJP subjects were cultured in the presence of human serum, both macrophages and cells with the morphology of immature monocyte-derived dendritic cells (MDDC) were observed. Within 4 days the prevalence of the immature MDDC was approximately twofold higher in LJP cultures than in NP cultures. In addition to their dendritic morphology, these cells were CD11c+and CD14−or CD14lowand stimulated potent autologous mixed leukocyte reactions, consistent with differentiation to the MDDC phenotype. Like LJP monocytes, cultures of MDDC generated with interleukin-4 and granulocyte-macrophage colony-stimulating factor selectively induced IgG2 in cultures of pokeweed mitogen-stimulated NP leukocytes. Together, these data suggest that the monocytes of LJP subjects have a propensity to differentiate into MDDC and that this differentiation may be related to the high levels of IgG2 that are observed in the sera of LJP subjects. As high levels of circulating IgG2 are correlated with less severe disease, the propensity of LJP monocytes to differentiate into MDDC may have important implications for both the host response against oral pathogens and the progression of LJP.
Identification of a Disulfide Isomerase Protein ofLeishmania majoras a Putative Virulence Factor
Authors: Achour Y. Ben , Chenik M. , Louzir H. , Dellagi K. 
Published: July 2002

ABSTRACTSeveral approaches have been previously used to elucidate the genetic basis ofLeishmaniavirulence. In general, they were based on laboratoryLeishmaniaclones genetically modified or grown in the presence of selecting agents. In a previous study, we demonstrated thatLeishmania majorfreshly isolated from human cutaneous lesions showed significant differences in the severity of the experimental disease induced in BALB/c mice. Here, using the mRNA differential display technique, we analyzed gene expression inL. majorpromastigotes showing different levels of virulence. We have identified a novelLeishmaniagene encoding a 477-amino-acid protein exhibiting two distinct regions that are identical to the putative active-site sequence (CGHC) of the eukaryotic protein disulfide isomerase (PDI). The recombinant protein displayed a specific PDI enzymatic activity. ThisL. majordisulfide isomerase protein (LmPDI) is predominantly expressed, at both the mRNA and protein levels, in highly virulent strains. Specific PDI inhibitors abolished the enzymatic activity of the recombinant protein and profoundly affected parasite growth. These findings suggest that LmPDI may play an important role inLeishmanianatural pathogenicity and may constitute a new target for anti-Leishmaniachemotherapy.
Fluorescence Resonance Energy Transfer Microscopy of the
Helicobacter pylori
Vacuolating Cytotoxin within Mammalian Cells
Authors: Willhite David C. , Ye Dan , Blanke Steven R. 
Published: July 2002

ABSTRACT

The
Helicobacter pylori
vacuolating cytotoxin (VacA) binds and enters mammalian cells to induce cellular vacuolation. To investigate the quaternary structure of VacA within the intracellular environment where toxin cytotoxicity is elaborated, we employed fluorescence resonance energy transfer (FRET) microscopy. HeLa cells coexpressing full-length and truncated forms of VacA fused to cyan fluorescent protein (CFP) or yellow fluorescent protein (YFP) were analyzed for FRET to indicate direct associations. These studies revealed that VacA-CFP and VacA-YFP interact within vacuolated cells, supporting the belief that monomer associations at an intracellular site are important for the toxin's vacuolating activity. In addition, the two fragments of proteolytically nicked VacA, p37 and p58, interact when coexpressed within mammalian cells. Because p37 and p58 function in
trans
when expressed separately within mammalian cells, these data suggest that the mechanism by which these two fragments induce vacuolation requires direct association. FRET microscopy also demonstrated interactions between mutant forms of VacA, as well as wild-type VacA with mutant forms of the toxin within vacuolated cells. Finally, a dominant-negative form of the toxin directly associates with wild-type VacA in cells where vacuolation was not detectable, suggesting that the formation of complexes comprising wild-type and dominant-negative forms of toxin acts to block intracellular toxin function.
Modification of Type IV Pilus-Associated Epithelial Cell Adherence and Multicellular Behavior by the PilU Protein of
Neisseria gonorrhoeae
Authors: Park Hae-Sun Moon , Wolfgang Matthew , Koomey Michael 
Published: July 2002

ABSTRACT

Expression of type IV pili (Tfp) correlates with the ability of
Neisseria gonorrhoeae
to colonize the human host, as well as with adherence to human epithelial tissue, twitching motility, competence for natural transformation, and autoagglutination.
N. gonorrhoeae
PilF (required for Tfp biogenesis) and PilT (required for twitching motility and transformation) share significant identities with members of a family of putative ATPases involved in membrane trafficking of macromolecules. An open reading frame downstream of the
pilT
locus encoding a 408-amino-acid protein with 33% identity with the gonococcal PilT protein and 45% identity with the PilU protein in
Pseudomonas aeruginosa
was characterized, and the corresponding gene was designated
pilU
. Unlike
N. gonorrhoeae pilT
mutants,
pilU
mutants express twitching motility and are competent for DNA transformation. However, loss-of-function mutations in
pilU
increased bacterial adherence to ME-180 human epithelial cells eightfold and disrupted in vitro Tfp-associated autoagglutination. Comparative alignment of
N. gonorrhoeae
PilU with other members of the TrbB-like family of traffic ATPases revealed a conserved carboxy-terminal domain unique to family members which are not essential for Tfp biogenesis but which specifically modify Tfp-associated phenotypes. Studies of the
pilT
-
pilU
locus by using Northern blotting, transcriptional fusions, and reverse transcription-PCR showed that the two genes encoding closely related proteins with dissimilar effects on Tfp phenotypes are transcribed from a single promoter.