bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Urease Expression in
Actinomyces naeslundii
WVU45
Authors: Morou-Bermudez Evangelia , Burne Robert A. 
Published: July 2002

ABSTRACT

The hydrolysis of urea by ureases of oral bacteria in dental plaque can cause a considerable increase in plaque pH, which can inhibit the development of dental caries. There is also indirect evidence that urea metabolism may promote the formation of calculus and that ammonia release from urea could exacerbate periodontal diseases.
Actinomyces naeslundii
, an early colonizer of the oral cavity and a numerically significant plaque constituent, demonstrates comparatively low levels of urease activity on isolation, so this organism has not been considered a major contributor to total oral urease activity. In this study it was observed that urease activity and urease-specific mRNA levels in
A. naeslundii
WVU45 can increase up to 50-fold during growth under nitrogen-limiting conditions. Using primer extension analysis, a putative, proximal, nitrogen-regulated promoter of the
A. naeslundii
urease gene cluster was identified. The functionality and nitrogen responsiveness of this promoter were confirmed using reporter gene fusions and 5′ deletion analysis. The data indicated that regulation of urease expression by nitrogen availability in
A. naeslundii
may require a positive transcriptional activator. Plaque bacteria may experience nitrogen limitation when carbohydrates are present in excess. Therefore, based on the results of this study and in contrast to previous beliefs, strains of
A. naeslundii
may have the potential to be significant contributors to total plaque ureolysis, particularly during periods when there is an increased risk for caries development.
Identification of a
Porphyromonas gingivalis
Receptor for the
Streptococcus gordonii
SspB Protein
Authors: Chung Whasun O. , Demuth Donald R. , Lamont Richard J. 
Published: July 2002

ABSTRACT

Colonization of the plaque biofilm by the oral pathogen
Porphyromonas gingivalis
is favored by the presence of antecedent organisms such as
Streptococcus gordonii
. Coadhesion between
P. gingivalis
and
S. gordonii
can be mediated by the SspB protein of
S. gordonii
; however, the
P. gingivalis
cognate receptor for this protein has not been identified. In this study, we identified a surface protein of
P. gingivalis
that interacts with the SspB protein. Coprecipitation between
P. gingivalis
outer membrane proteins and purified SspB protein demonstrated that a 100-kDa
P. gingivalis
protein bound to SspB. The 100-kDa protein also bound to an engineered strain of
Enterococcus faecalis
that expresses the SspB protein on the cell surface. Monospecific polyclonal antibodies to the 100-kDa protein inhibited the binding between
P. gingivalis
and
S. gordonii
in a dose-dependent manner up to 86%. Amino acid sequencing of the 100-kDa protein showed homology to a protein previously identified as the
P. gingivalis
minor fimbria. The minor fimbrial protein may exist as a complex with a hemagglutinin-like protein since the genes encoding these proteins are adjacent on the chromosome and are cotranscribed. Thus, the
P. gingivalis
receptor for
S. gordonii
SspB is a 100-kDa protein that structurally may be a minor fimbria-protein complex and functionally effectuates coadhesion.
Neutralizing Antibodies to Adenylate Cyclase Toxin Promote Phagocytosis ofBordetella pertussisby Human Neutrophils
Authors: Weingart Christine L. , Mobberley-Schuman Paula S. , Hewlett Erik L. , Gray Mary C. , Weiss Alison A. 
Published: July 2002

ABSTRACTA previous study showed that opsonization with human immune serum could either promote or antagonize phagocytosis ofBordetella pertussisby human neutrophils depending on whether the bacteria expressed adenylate cyclase toxin. Opsonization of the wild-type strain inhibited phagocytosis relative to unopsonized controls. In contrast, mutants lacking adenylate cyclase toxin were efficiently phagocytosed when opsonized with human immune serum. In this study, we examined opsonization in the presence or absence of monoclonal antibodies to adenylate cyclase toxin. Addition of neutralizing monoclonal antibodies to adenylate cyclase toxin converted a serum that previously inhibited both attachment and phagocytosis of the wild-type strain to one that increased both attachment and phagocytosis compared to the no-serum control. Monoclonal antibodies that recognize the adenylate cyclase toxin but fail to neutralize activity were without effect. These results suggest that adenylate cyclase toxin inhibits both Fc receptor-mediated attachment and phagocytosis ofB. pertussisby neutrophils.
Expression of Chemokine Genes in Murine Macrophages Infected withOrientia tsutsugamushi
Authors: Cho Nam-Hyuk , Seong Seung-Yong , Huh Myung-Suk , Han Tae-Hee , Koh Young-Sang , Choi Myung-Sik , Kim Ik-Sang 
Published: July 2002

ABSTRACTScrub typhus, caused byOrientia tsutsugamushiinfection, is characterized by local as well as systemic inflammatory manifestations. Inflammation is initiated byO. tsutsugamushi-infected macrophages and endothelial cells in the dermis. We investigated the regulation of chemokine induction in macrophage cell line J774A.1 in response toO. tsutsugamushiinfection. The mRNAs for macrophage inflammatory proteins 1α/β (MIP-1α/β), MIP-2, and macrophage chemoattractant protein 1 were induced within 30 min, and their levels showed a transitory peak for 3 to 12 h. However, the lymphotactin, eotaxin, gamma interferon-inducible protein 10, and T-cell activation gene 3 mRNAs were not detected by RNase protection assays. Heat-killedO. tsutsugamushiinduced a similar extent of chemokine responses. Induction of the chemokine genes was not blocked by the eukaryotic protein synthesis inhibitor cycloheximide, suggesting that de novo synthesis of host cell protein is not required for these transcriptional responses. The induction of chemokine mRNAs byO. tsutsugamushiwas blocked by the inhibitors of NF-κB activation. Furthermore,O. tsutsugamushiinduced the nuclear translocation and activation of NF-κB. These results demonstrate that heat-stable molecules ofO. tsutsugamushiinduce a subset of chemokine genes and that induction involves activation of the transcription factor NF-κB.
Use of Lambda Phage S and R Gene Products in an Inducible Lysis System for
Vibrio cholerae
- and
Salmonella enterica
Serovar Typhimurium-Based DNA Vaccine Delivery Systems
Authors: Jain Vivek , Mekalanos John J. 
Published: July 2002

ABSTRACT

Novel methods for adapting DNA vaccine technology to the prevention of mucosal diseases are greatly needed. Here we show that regulated expression of phage lambda lysis genes S and R causes dramatic lysis of both
Vibrio cholerae
and
Salmonella enterica
serovar Typhimurium cells with concomitant release of plasmid DNA into the surrounding media. We also used single and double DNase mutant strains to show that secreted
V. cholerae
DNases can adversely affect the integrity of DNA molecules released upon lysis. These results suggest that incorporation of lambda SR-mediated lysis constructs and DNA stabilizing mutations into candidate live attenuated bacterial vaccines offers a promising approach for the development of effective mucosal DNA delivery vectors for humans.
Genetic Relationships between Clinical Isolates of
Streptococcus pneumoniae
,
Streptococcus oralis
, and
Streptococcus mitis
: Characterization of “Atypical” Pneumococci and Organisms Allied to
S. mitis
Harboring
S. pneumoniae
Virulence Factor-Encoding Genes
Authors: Whatmore Adrian M. , Efstratiou Androulla , Pickerill A. Paul , Broughton Karen , Woodard Geoffrey , Sturgeon Daniel , George Robert , Dowson Christopher G. 
Published: July 2002

ABSTRACT

The oral streptococcal group (mitis phylogenetic group) currently consists of nine recognized species, although the group has been traditionally difficult to classify, with frequent changes in nomenclature over the years. The pneumococcus (
Streptococcus pneumoniae
), an important human pathogen, is traditionally distinguished from the most closely related oral streptococcal species
Streptococcus mitis
and
Streptococcus oralis
on the basis of three differentiating characteristics: optochin susceptibility, bile solubility, and agglutination with antipneumococcal polysaccharide capsule antibodies. However, there are many reports in the literature of pneumococci lacking one or more of these defining characteristics. Sometimes called “atypical” pneumococci, these isolates can be the source of considerable confusion in the clinical laboratory. Little is known to date about the genetic relationships of such organisms with classical
S. pneumoniae
isolates. Here we describe these relationships based on sequence analysis of housekeeping genes in comparison with previously characterized isolates of
S. pneumoniae
,
S. mitis
, and
S. oralis
. While most pneumococci were found to represent a closely related group these studies identified a subgroup of atypical pneumococcal isolates (bile insoluble and/or “acapsular”) distinct from, though most closely related to, the “typical” pneumococcal isolates. However, a large proportion of isolates, found to be atypical on the basis of capsule reaction alone, did group with typical pneumococci, suggesting that they have either lost capsule production or represent as-yet-unrecognized capsular types. In contrast to typical
S. pneumoniae
, isolates phenotypically identified as
S. mitis
and
S. oralis
, which included isolates previously characterized in taxonomic studies, were genetically diverse. While most of the
S. oralis
isolates did fall into a well-separated group,
S. mitis
isolates did not cluster into a well-separated group. During the course of these studies we also identified a number of potentially important pathogenic isolates, which were frequently associated with respiratory disease, that phenotypically and genetically are most closely related to
S. mitis
but which harbor genes encoding the virulence determinants pneumolysin and autolysin classically associated with
S. pneumoniae
.
Colonization of the Respiratory Tract by a Virulent Strain of Avian
Escherichia coli
Requires Carriage of a Conjugative Plasmid
Authors: Ginns C. A. , Benham M. L. , Adams L. M. , Whithear K. G. , Bettelheim K. A. , Crabb B. S. , Browning G. F. 
Published: July 2002

ABSTRACT

The E3 strain of
E. coli
was isolated in an outbreak of respiratory disease in broiler chickens, and experimental aerosol exposure of chickens to this strain induced disease similar to that seen in the field. In order to establish whether the virulent phenotype of this strain was associated with carriage of particular plasmids, four plasmid-cured derivatives, each lacking two or more of the plasmids carried by the wild-type strain, were assessed for virulence. Virulence was found to be associated with one large plasmid, pVM01. Plasmid pVM01 was marked by introduction of the transposon Tn
phoA
, carrying kanamycin resistance, and was then cloned by transformation of
E. coli
strain DH5α. The cloned plasmid was then reintroduced by conjugation into an avirulent plasmid-cured derivative of strain E3 which lacked pVM01. The conjugant was shown to be as virulent as the wild-type strain E3, establishing that this plasmid is required for virulence following aerosol exposure. This virulence plasmid conferred expression of a hydroxamate siderophore, but not colicins, on both strain E3 and strain DH5α. Carriage of this plasmid was required for strain E3 to colonize the respiratory tracts of chickens but was not necessary for colonization of the gastrointestinal tract. However, the virulence plasmid did not confer virulence, or the capacity to colonize the respiratory tract, on strain DH5α. Thus, these studies have established that infection of chickens with
E. coli
strain E3 by the respiratory route is dependent on carriage of a conjugative virulence plasmid, which confers the capacity to colonize specifically the respiratory tract and which also carries genes for expression of a hydroxymate siderophore. These findings will facilitate identification of the specific genes required for virulence in these pathogens.
Roles of the Surface Layer Proteins of
Campylobacter fetus
subsp.
fetus
in Ovine Abortion
Authors: Grogono-Thomas R. , Dworkin J. , Blaser M. J. , Newell D. G. 
Published: July 2002

ABSTRACT

The role of the surface (S)-layer proteins of
Campylobacter fetus
subsp.
fetus
has been investigated using an ovine model of abortion. Wild-type strain 23D induced abortion in up to 90% of pregnant ewes challenged subcutaneously. Isolates recovered from both dams and fetuses expressed S-layer proteins with variable molecular masses. The spontaneous S-layer-negative variant, strain 23B, neither colonized nor caused abortions in pregnant ewes. A series of isogenic
sapA
and
recA
mutants, derived from 23D, also were investigated in this model. A mutant (501 [
sapA recA
+
]) caused abortion in one of five challenged animals and was recovered from the placenta of a second animal. Another mutant (502 [
sapA recA
]) with no S-layer protein expression caused no colonization or abortions in challenged animals but caused abortion when administered intraplacentally. Mutants 600(2) and 600(4), both
recA
, had fixed expression of 97- and 127-kDa S-layer proteins, respectively. Two of the six animals challenged with mutant 600(4) were colonized, but there were no abortions. As expected, all five strains recovered expressed a 127-kDa S-layer protein. In contrast, mutant 600(2) was recovered from the placentas of all five challenged animals and caused abortion in two. Unexpectedly, one of the 16 isolates expressed a 127-kDa rather than a 97-kDa S-layer protein. Thus, these studies indicate that S-layer proteins appear essential for colonization and/or translocation to the placenta but are not required to mediate fetal injury and that S-layer variation may occur in a
recA
strain.
Candida albicansandCandida kruseiDifferentially Induce Human Blood Mononuclear Cell Interleukin-12 and Gamma Interferon Production
Authors: Xiong Jingbo , Kang Kefei , Liu Liming , Yoshida Yuichi , Cooper Kevin D. , Ghannoum Mahmoud A. 
Published: July 2002

ABSTRACTProtection againstCandidainfection involves both innate and acquired immune responses, and cytokines produced by monocytes during the innate response may modify the acquired immune response by T cells. We hypothesized thatCandidaspecies which differ in pathogenicity can differentially induce production of immunoregulatory cytokines by human monocytes, which in turn modify T cells for immune responses toCandida. To test this hypothesis, we examined the effects ofCandida albicansandCandida kruseion immunoregulatory cytokine production by human monocytes and gamma interferon (IFN-γ) production by peripheral blood mononuclear cells (PBMC). Purified monocytes were incubated with live or heat-killed strains ofC. albicansandC. kruseiat the optimalCandida/monocyte ratio of 0.5. Cytokines in the supernatants were measured by enzyme-linked immunosorbent assay. Our data demonstrated that liveC. albicansandC. kruseisignificantly induced interleukin-10 (IL-10), monocyte chemotactic factor 1, IL-1β, and tumor necrosis factor alpha production by monocytes relative to unstimulated monocytes. In contrast, unlikeC. krusei, pathogenic live strains ofC. albicansinduced no or only a minimal level of IL-12. The expression of IL-12 p40 mRNA levels by reverse transcription-PCR corroborated the IL-12 protein (p70) findings. In human PBMC, human blood monocytes were the major source of both IL-10 and IL-12 production in response toC. albicansandC. krusei. Upon activation of T cells in the presence ofCandida-modified monocytes and antigen-presenting cells, IL-12 production by PBMC treated withCandidaorganisms correlated strongly with the level of IFN-γ production by T cells. These results indicate that the virulence ofC. albicansmay be related to its ability to induce the monocytic type II cytokine IL-10, with a selective inhibition of IL-12 production, which may be responsible for the observed lack of T-cell IFN-γ and may restrain an effective type I immune response toCandida.
Deviant Expression of Rab5 on Phagosomes Containing the Intracellular PathogensMycobacterium tuberculosisandLegionella pneumophilaIs Associated with Altered Phagosomal Fate
Authors: Clemens Daniel L. , Lee Bai-Yu , Horwitz Marcus A. 
Published: July 2002

ABSTRACTThe intracellular human pathogensLegionella pneumophilaandMycobacterium tuberculosisreside in altered phagosomes that do not fuse with lysosomes and are only mildly acidified. TheL. pneumophilaphagosome exists completely outside the endolysosomal pathway, and theM. tuberculosisphagosome displays a maturational arrest at an early endosomal stage along this pathway. Rab5 plays a critical role in regulating membrane trafficking involving endosomes and phagosomes. To determine whether an alteration in the function or delivery of Rab5 could play a role in the aberrant development ofL. pneumophilaandM. tuberculosisphagosomes, we have examined the distribution of the small GTPase, Rab5c, in infected HeLa cells overexpressing Rab5c. Both pathogens formed phagosomes in HeLa cells with molecular characteristics similar to their phagosomes in human macrophages and multiplied in these host cells. Phagosomes containing virulent wild-typeL. pneumophilanever acquired immunogold staining for Rab5c, whereas phagosomes containing an avirulent mutantL. pneumophila(which ultimately fused with lysosomes) transiently acquired staining for Rab5c after phagocytosis. In contrast,M. tuberculosisphagosomes exhibited abundant staining for Rab5c throughout its life cycle. To verify that the overexpressed, recombinant Rab5c observed on the bacterial phagosomes was biologically active, we examined the phagosomes in HeLa cells expressing Rab5c Q79L, a fusion-promoting mutant. Such HeLa cells formed giant vacuoles, and after incubation with various particles, the giant vacuoles acquired large numbers of latex beads,M. tuberculosis, and avirulentL. pneumophilabut not wild-typeL. pneumophila, which consistently remained in tight phagosomes that did not fuse with the giant vacuoles. These results indicate that whereas Rab5 is absent from wild-typeL. pneumophilaphagosomes, functional Rab5 persists onM. tuberculosisphagosomes. The absence of Rab5 on theL. pneumophilaphagosome may underlie its lack of interaction with endocytic compartments. The persistence of functional Rab5 on theM. tuberculosisphagosomes may enable the phagosome to retard its own maturation at an early endosomal stage.
Role of Manganese-Containing Superoxide Dismutase in Oxidative Stress and Virulence of
Streptococcus pneumoniae
Authors: Yesilkaya Hasan , Kadioglu Aras , Gingles Neill , Alexander Janet E. , Mitchell Tim J. , Andrew Peter W. 
Published: July 2002

ABSTRACT

Streptococcus pneumoniae
was shown to contain two types of superoxide dismutase, MnSOD and FeSOD. Levels of MnSOD increased during growth in an aerobic environment. The
sodA
gene, encoding MnSOD, of virulent
S. pneumoniae
type 2 strain D39 was inactivated to give mutant D39HY1. Aerobically, D39HY1 had a lower growth rate than the wild type and exhibited susceptibility to the redox-active compound paraquat, but anaerobic growth of D39HY1 was identical to that of the wild type. Virulence studies showed that the median survival time of mice infected intranasally with D39HY1 was significantly longer than that of mice infected with the wild-type pneumococcus. In contrast to the wild type, D39HY1 did not multiply in lungs during the first 24 h but thereafter grew at the same rate as the wild type. Appearance in the bloodstream was also delayed, but growth in the blood was unimpaired by the
sodA
mutation. The pattern of inflammation in lungs infected with D39HY1 differed from that in wild-type-infected mice. After infection with D39HY1, neutrophils were densely packed around bronchioles, in contrast to the wild-type infection, where neutrophils were more diffusely localized.
Role of Gamma Interferon and Interleukin-4 in Host Defense against the Human Filarial ParasiteBrugia malayi
Authors: Babu Subash , Ganley Lisa M. , Klei Thomas R. , Shultz Leonard D. , Rajan T. V. 
Published: July 2002

ABSTRACTWe have investigated the roles of gamma interferon (IFN-γ) and interleukin-4 (IL-4) in host defense againstBrugia malayi. Our data suggest that the lack of either IFN-γ or IL-4 prolongs the time required to achieve sterile immunity, suggesting that both canonical type 1 and type 2 responses are involved in the clearance of infection.
Expression of Interleukin-1β, Tumor Necrosis Factor Alpha, and Interleukin-6 in Human Peripheral Blood Leukocytes Exposed to Human Granulocytic Ehrlichiosis Agent or Recombinant Major Surface Protein P44
Authors: Kim Hyung-Yong , Rikihisa Yasuko 
Published: July 2002

ABSTRACTHuman granulocytic ehrlichiosis (HGE) is an emerging febrile systemic disease caused by the HGE agent, an obligatory intracellular bacterium of granulocytes. The pathogenicity- and immunity-related mechanisms of HGE are unknown. In this study, several cytokines generated in human peripheral blood leukocytes (PBLs) incubated with the HGE agent or a recombinant 44-kDa major surface protein (rP44) of the HGE agent were examined by reverse transcription-PCR and a capture enzyme-linked immunosorbent assay. The HGE agent induced expression of interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and IL-6 mRNAs and proteins in PBLs in a dose-dependent manner to levels as high as those resulting fromEscherichia colilipopolysaccharide stimulation. The kinetics of induction of these three cytokines in PBLs by rP44 and by the HGE agent were similar. Proteinase K treatment of the HGE agent or rP44 eliminated the ability to induce these three cytokines. Induction of these cytokine mRNAs was not dependent on superoxide generation. These results suggest that P44 proteins have a major role in inducing the production of proinflammatory cytokines by PBLs. Expression of IL-8, IL-10, gamma interferon, transforming growth factor β, and IL-2 mRNAs in response to the HGE agent was not remarkable. Among PBLs, neutrophils and lymphocytes expressed IL-1β mRNA but not TNF-α or IL-6 mRNA in response to the HGE agent, whereas monocytes expressed all three of these cytokine mRNAs. These observations suggest that induction of proinflammatory-cytokine gene expression by the major outer membrane protein of the HGE agent in monocytes, which are not the primary host cells of the HGE agent, contributes to HGE pathogenesis and immunomodulation.
Characterization of an Anticryptococcal Protein Isolated from Human Serum
Authors: Sridhar Sridevi , Ahluwalia Mala , Brummer Elmer , Stevens David A. 
Published: July 2002

ABSTRACT

Human serum at low concentrations inhibits the growth of
Cryptococcus neoformans
in vitro. Fractionation of serum yielded a purified inhibitory protein with a molecular mass of ∼81.8 kDa, a pI of ∼6.2, and an amino acid sequence that matched that of human transferrin. The inhibitory activity and that of apotransferrin and 5% human serum were reversed by 10 μM freshly prepared FeCl
3
.
Differential Infectivity and Division ofToxoplasma gondiiin Human Peripheral Blood Leukocytes
Authors: Channon Jacqueline Y. , Seguin Rosanne M. , Kasper Lloyd H. 
Published: July 2002

ABSTRACTWhen tachyzoites were incubated with human peripheral blood leukocytes in vitro, more monocytes and dendritic cells than neutrophils or lymphocytes were infected. Although tachyzoites were able to divide in each of these cell types, monocytes and dendritic cells were more permissive to rapid tachyzoite division than neutrophils or lymphocytes.