bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antimycobacterial Calixarenes Enhance Innate Defense Mechanisms in Murine Macrophages and Induce Control ofMycobacterium tuberculosisInfection in Mice
Authors: Colston M. Joseph , Hailes Helen C. , Stavropoulos Evangelos , Hervé Anne C. , Hervé Gwenaelle , Goodworth Kerry J. , Hill Alison M. , Jenner Peter , Hart Philip D. , Tascon Ricardo E. 
Published: October 2004

ABSTRACTTuberculosis remains the leading cause of death among infectious diseases, accounting for more than two million deaths annually. The incidence of the disease is increasing globally, partially because of the resurgence of drug-resistant strains ofMycobacterium tuberculosis. Calixarenes are macrocyclic oligomers, some of which are able to modify the growth ofM. tuberculosisin infected cells. Most experimental work has been carried out with Macrocyclon, also known as HOC 12.5EO. In this study, we demonstrate that Macrocyclon is effective in controllingM. tuberculosisinfections, and we provide evidence that its effect is partially mediated by anl-arginine-dependent mechanism of macrophage activation that involves the activity of the inducible nitric oxide synthase. We also show that Macrocyclon is effective in athymic and major histocompatibility complex class II−/−mice and synthesized a number of structurally related calixarenes expressing significant antimycobacterial activity.
Glycosylation of the Major Polar Tube Protein ofEncephalitozoon hellem, a Microsporidian Parasite That Infects Humans
Authors: Xu Yanji , Takvorian Peter M. , Cali Ann , Orr George , Weiss Louis M. 
Published: October 2004

ABSTRACTThe microsporidia are ubiquitous, obligate intracellular eukaryotic spore-forming parasites infecting a wide range of invertebrates and vertebrates, including humans. The defining structure of microsporidia is the polar tube, which forms a hollow tube through which the sporoplasm is transferred to the host cell. Research on the molecular and cellular biology of the polar tube has resulted in the identification of three polar tube proteins: PTP1, PTP2, and PTP3. The major polar tube protein, PTP1, accounts for at least 70% of the mass of the polar tube. In the present study, PTP1 was found to be posttranslationally modified. Concanavalin A (ConA) bound to PTP1 and to the polar tube of several different microsporidia species. Analysis of the glycosylation ofEncephalitozoon hellemPTP1 suggested that it is modified by O-linked mannosylation, and ConA binds to these O-linked mannose residues. Mannose pretreatment of RK13 host cells decreased their infection byE. hellem, consistent with an interaction between the mannosylation of PTP1 and some unknown host cell mannose-binding molecule. A CHO cell line (Lec1) that is unable to synthesize complex-type N-linked oligosaccharides had an increased susceptibility toE. helleminfection compared to wild-type CHO cells. These data suggest that the O-mannosylation of PTP1 may have functional significance for the ability of microsporidia to invade their host cells.
Cytokine Response to Infection with
Bacillus anthracis
Spores
Authors: Pickering Alison K. , Osorio Manuel , Lee Gloria M. , Grippe Vanessa K. , Bray Mechelle , Merkel Tod J. 
Published: October 2004

ABSTRACT

Bacillus anthracis
, the etiological agent of anthrax, is a gram-positive, spore-forming bacterium. The inhalational form of anthrax is the most severe and is associated with rapid progression of the disease and the outcome is frequently fatal. Transfer from the respiratory epithelium to regional lymph nodes appears to be an essential early step in the establishment of infection. This transfer is believed to occur by means of carriage within alveolar macrophages following phagocytosis. Therefore, the ability of
B. anthracis
to transit through the host macrophage or dendritic cell appears to be an early and critical step in
B. anthracis
pathogenesis. In this work, we examined the cytokine responses to spore infection in mouse primary peritoneal macrophages, in primary human dendritic cells, and during a spore aerosol infection model utilizing the susceptible A/J mouse strain. We demonstrated that both mouse peritoneal macrophages and human dendritic cells exhibited significant intracellular bactericidal activity during the first hours following uptake, providing the necessary time to mount a cytokine response prior to cell lysis. Strong tumor necrosis factor (TNF-α) and interleukin-6 (IL-6) responses were seen in mouse peritoneal macrophages. In addition to TNF-α and IL-6, human dendritic cells produced the cytokines IL-1β, IL-8, and IL-12. A mixture of Th1 and Th2 cytokines were detected in sera obtained from infected animals. In this study, we provide further evidence of an acute cytokine response when cells in culture and mice are infected with
B. anthracis
spores.
In Vivo Compartmentalization of Functionally Distinct, Rapidly Responsive Antigen-Specific T-Cell Populations in DNA-Immunized orSalmonella entericaSerovar Typhimurium-Infected Mice
Authors: Kirby Alun C. , Sundquist Malin , Wick Mary Jo 
Published: October 2004

ABSTRACTThe location and functional properties of antigen-specific memory T-cell populations in lymphoid and nonlymphoid compartments following DNA immunization or infection withSalmonellawere investigated. Epitope-specific CD8+-T-cell expansion and retention during the memory phase were analyzed for DNA-immunized mice by use of a 5-h peptide restimulation assay. These data revealed that epitope-specific gamma interferon (IFN-γ)-positive CD8+T cells occur at higher frequencies in the spleen, liver, and blood than in draining or peripheral lymph nodes during the expansion phase. Moreover, this distribution is maintained into long-term memory. The location and function of both CD4+and CD8+Salmonella-specific memory T cells in mice who were given a single dose ofSalmonella entericaserovar Typhimurium was also quantitated by an ex vivo restimulation with bacterial lysate to detect the totalSalmonella-specific memory pool. Mice immunized up to 6 months previously withS. entericaserovar Typhimurium had bacterium-specific CD4+T cells that were capable of producing IFN-γ or tumor necrosis factor alpha (TNF-α) at each site analyzed. Similar findings were observed for CD8+T cells that were capable of producing IFN-γ, while a much lower frequency and more restricted distribution were associated with TNF-α-producing CD8+T cells. This study is the first to assess the frequencies, locations, and functions of both CD4+and CD8+memory T-cell populations in the sameSalmonella-infected individuals and demonstrates the organ-specific functional compartmentalization of memory T cells afterSalmonellainfection.
Novel Human In Vitro System for Evaluating Antimycobacterial Vaccines
Authors: Kampmann Beate , Tena Gwen N. , Mzazi Shumikazi , Eley Brian , Young Douglas B. , Levin Michael 
Published: October 2004

ABSTRACTMajor research efforts are directed towards the development of a better antimycobacterial vaccine. But progress in the field of tuberculosis vaccine development has been hampered by the lack of human in vitro models to assess vaccine immunogenicity and efficacy. New candidate vaccines will have to be evaluated against the existingMycobacterium bovisBCG “gold standard.” It is therefore important to understand the type of immune responses elicited by BCG vaccination to enable comparisons with potential new candidates. We used a novel human in vitro whole-blood model, which measures immune responses to mycobacteria by use of reporter gene-tagged BCG (BCGlux), to study immune responses to BCG vaccination in 50 neonates in a setting in Cape Town, Republic of South Africa, where tuberculosis is endemic. BCG vaccination significantly reduced growth of BCGluxin whole blood (prevaccination median growth ratio [GR], 9.6; range, 1.3 to 24; postvaccination median GR, 3.9; range, 0.6 to 12.2 [P< 0.0001]). Growth of BCGluxwas better restricted in vaccinated infants than in unvaccinated age-matched controls (n= 4). BCG vaccination induced significantly higher gamma interferon production in response to BCGlux(P< 0.0001) and to purified protein derivative (P= 0.0001). No significant changes in either growth of BCGluxor cytokine production occurred in an adult control group (n= 6) over the study period. The whole-blood luminescence model detects changes in cellular immune responses to mycobacteria induced by BCG vaccination. It is therefore a useful new tool in studying the immunogenicity of newly developed vaccine candidates prior to large field trials assessing efficacy.
Gonococcal Porin IB Activates NF-κB in Human Urethral Epithelium and Increases the Expression of Host Antiapoptotic Factors
Authors: Binnicker Matthew J. , Williams Richard D. , Apicella Michael A. 
Published: October 2004

ABSTRACT

Infection of human urethral epithelial cells (UECs) with
Neisseria gonorrhoeae
increases the transcription of several host antiapoptotic genes, including
bfl-1
,
cox-2
, and
c-IAP-2
. In order to identify the bacterial factor(s) responsible for eliciting these changes, the transcriptional status of apoptotic machinery was monitored in UECs challenged with certain gonococcal membrane components. Initially, we observed that infection of UECs with gentamicin-killed gonococci increased the expression of the antiapoptotic Bcl-2 family member,
bfl-1
. This observation indicated that viable, replicating bacteria are not required for induction of antiapoptotic gene expression. Confirming this observation, treatment of UECs with purified gonococcal membrane increased the expression of
bfl-1
,
cox-2
, and
c-IAP-2
. This finding suggested that a factor or multiple factors present in the outer membrane (OM) are responsible for altering UEC antiapoptotic gene expression. Interestingly, treatment of UECs with gonococcal porin IB (PorB IB), a major constituent of the OM, significantly increased the transcription of
bfl-1
,
cox-2
, and
c-IAP-2
. The upregulation of these genes by PorB IB was determined to be dependent on NF-κB activation, as inhibiting NF-κB blocked induced expression of these genes. This work demonstrates the altered expression of host apoptotic factors in response to gonococcal PorB IB and supports a model whereby UEC cell death may be modulated as a potential mechanism of bacterial survival and proliferation.
Identification of a Hemin Utilization Protein of
Moraxella catarrhalis
(HumA)
Authors: Furano Kristin , Campagnari Anthony A. 
Published: October 2004

ABSTRACT

Moraxella catarrhalis
is a major cause of acute otitis media in young children and has also been implicated as an important cause of exacerbations in adults with underlying pulmonary disease. Due to the considerable level of antibiotic resistance and the high degree of carriage rates in young children, it is likely that the incidence of
M. catarrhalis
infections will continue to rise.
M. catarrhalis
is a strict human respiratory pathogen, and this bacterium uses both transferrin and lactoferrin receptors to fulfill the essential iron requirement for survival in vivo. However, these are the only described iron acquisition systems for this organism. In this report we have demonstrated that
M. catarrhalis
can also utilize hemin as a sole source of iron for growth. In addition, we have identified and characterized an outer membrane protein with homology (26 to 28% similarity) to other known hemin binding and uptake proteins in related gram-negative organisms (i.e.,
Bordetella
and
Yersinia
spp.). This newly described
M. catarrhalis
protein, termed HumA, is capable of directly binding to hemin coupled to a solid-phase matrix.
M. catarrhalis
HumA expressed on the surface of an
Escherichia coli hemA
-deficient strain (K-12 EB53) is fully capable of complementing the defect and thus restoring the ability of this strain to grow in the presence of hemin. When
M. catarrhalis
is grown in the presence of hemin, HumA expression is clearly increased as shown by Western blotting with polyclonal antiserum developed against a HumA peptide. In addition, growth analyses revealed that a HumA-deficient mutant of
M. catarrhalis
(7169::
humA
) is restricted for growth in the presence of hemin as the sole iron source compared to the wild-type strain. We conclude that HumA is an essential component of a hemin uptake and utilization system previously undescribed for
M. catarrhalis
, thus providing another mechanism of iron acquisition that may facilitate persistent colonization of the mucosal surface.
RpoS Is Not Central to the General Stress Response inBorrelia burgdorferibut Does Control Expression of One or More Essential Virulence Determinants
Authors: Caimano Melissa J. , Eggers Christian H. , Hazlett Karsten R. O. , Radolf Justin D. 
Published: October 2004

ABSTRACTBorrelia burgdorferi, the Lyme disease spirochete, undergoes dramatic changes in antigenic composition as it cycles between its arthropod and mammalian hosts. A growing body of evidence suggests that these changes reflect, at least in part, the need for spirochetes to adapt to the physiological stresses imposed by abrupt changes in environmental conditions and nutrient availability. In many microorganisms, global responses are mediated by master regulators such as alternative sigma factors, withEscherichia coliRpoS (σS) serving as a prototype. The importance of this transcriptional activator in other bacteria, coupled with the report by Hübner et al. (A. Hübner, X. Yang, D. M. Nolen, T. G. Popova, F. C. Cabello, and M. V. Norgard, Proc. Natl. Acad. Sci. USA98:12724-12729, 2001) demonstrating that the borrelial RpoS ortholog controls expression of OspC and decorin-binding protein A (DbpA), prompted us to examine more closely the roles of RpoS-dependent and -independent differential gene expression in physiological adaptation by the Lyme disease spirochete. We observed thatB. burgdorferi rpoS(rpoSBb) was induced following temperature shift and transcript levels were further enhanced by reduced pH (pH 6.8). Using quantitative real-time reverse transcription-PCR (RT-PCR), we demonstrated that, in contrast to its ortholog (rpoSEc) inEscherichia coli,rpoSBbwas expressed at significant levels inB. burgdorferithroughout all phases of growth following temperature shift. By comparing aB. burgdorferistrain 297rpoSBbmutant to its wild-type counterpart, we determined that RpoSBbwas not required for survival following exposure to a wide range of environmental stresses (i.e., temperature shift, serum starvation, increased osmolality, reactive oxygen intermediates, and increased or reduced oxygen tension), although the mutant was more sensitive to extremes of pH. WhileB. burgdorferistrains lacking RpoS were able to survive within intraperitoneal dialysis membrane chambers at a level equivalent to that of the wild type, they were avirulent in mice. Lastly, RT-PCR analysis of theospE-ospF-elpparalogous lipoprotein families complements earlier findings that many temperature-inducible borrelial loci are controlled in an RpoSBb-independent manner. Together, these data point to fundamental differences between the role(s) of RpoS inB. burgdorferiand that inE. coli. Rather than functioning as a master regulator, RpoSBbappears to serve as a stress-responsive activator of a subset of virulence determinants that, together with the RpoS-independent, differentially expressed regulon, encompass the spirochete's genetic programs required for mammalian host adaptation.
Differential Immune Modulatory Activity of
Pseudomonas aeruginosa
Quorum-Sensing Signal Molecules
Authors: Hooi Doreen S. W. , Bycroft Barrie W. , Chhabra Siri Ram , Williams Paul , Pritchard David I. 
Published: October 2004

ABSTRACT

Pseudomonas aeruginosa
releases a spectrum of well-regulated virulence factors, controlled by intercellular communication (quorum sensing) and mediated through the production of small diffusible quorum-sensing signal molecules (QSSM). We hypothesize that QSSM may in fact serve a dual purpose, also allowing bacterial colonization via their intrinsic immune-modulatory capacity. One class of signal molecule, the
N
-acylhomoserine lactones, has pleiotropic effects on eukaryotic cells, particularly those involved in host immunity. In the present study, we have determined the comparative effects of two chemically distinct and endobronchially detectable QSSM,
N
-(3-oxododecanoyl)-
l
-homoserine lactone (3-oxo-C
12
-HSL) and 2-heptyl-3-hydroxy-4 (1
H
)-quinolone or the
Pseudomonas
quinolone signal (PQS), on human leukocytes exposed to a series of stimuli designed to detect differential immunological activity in vitro. 3-Oxo-C
12
-HSL and PQS displayed differential effects on the release of interleukin-2 (IL-2) when human T cells were activated via the T-cell receptor and CD28 (a costimulatory molecule). 3-Oxo-C
12
-HSL inhibited cell proliferation and IL-2 release; PQS inhibited cell proliferation without affecting IL-2 release. Both molecules inhibited cell proliferation and the release of IL-2 following mitogen stimulation. Furthermore, in the presence of
Escherichia coli
lipopolysaccharide, 3-oxo-C
12
-HSL inhibited tumor necrosis factor alpha release from human monocytes, as reported previously (K. Tateda et al., Infect. Immun. 64:37-43, 1996), whereas PQS did not inhibit in this assay. These data highlight the presence of two differentially active immune modulatory QSSM from
P. aeruginosa
, which are detectable endobronchially and may be active at the host/pathogen interface during infection with
P. aeruginosa
, should the bronchial airway lymphoid tissues prove to be accessible to QSSM.
Antibodies to the N-Terminal Block 2 ofPlasmodium falciparumMerozoite Surface Protein 1 Are Associated with Protection against Clinical Malaria
Authors: Cavanagh David R. , Dodoo Daniel , Hviid Lars , Kurtzhals Jørgen A. L. , Theander Thor G. , Akanmori Bartholomew D. , Polley Spencer , Conway David J. , Koram Kojo , McBride Jana S. 
Published: October 2004

ABSTRACTThis longitudinal prospective study shows that antibodies to the N-terminal block 2 region of thePlasmodium falciparummerozoite surface protein 1 (MSP-1) are associated with protection against clinical malaria in an area of stable but seasonal malaria transmission of Ghana. Antibodies to the block 2 region of MSP-1 were measured in a cohort of 280 children before the beginning of the major malaria transmission season. The cohort was then actively monitored for malaria, clinically and parasitologically, over a period of 17 months. Evidence is presented for an association between antibody responses to block 2 and a significantly reduced risk of subsequent clinical malaria. Furthermore, statistical survival analysis provides new information on the duration of the effect over time. The results support a conclusion that the block 2 region of MSP-1 is a target of protective immunity againstP. falciparumand, thus, a promising new candidate for the development of a malaria vaccine.
Phase I Testing of a Malaria Vaccine Composed of Hepatitis B Virus Core Particles ExpressingPlasmodium falciparumCircumsporozoite Epitopes
Authors: Nardin Elizabeth H. , Oliveira Giane A. , Calvo-Calle J. Mauricio , Wetzel Kristiane , Maier Carolin , Birkett Ashley J. , Sarpotdar Pramod , Corado Michael L. , Thornton George B. , Schmidt Annette 
Published: October 2004

ABSTRACTWe report the first phase I trial to assess the safety and immunogenicity of a malaria vaccine candidate, ICC-1132 (Malarivax), composed of a modified hepatitis B virus core protein (HBc) containing minimal epitopes of thePlasmodium falciparumcircumsporozoite (CS) protein. When expressed inEscherichia coli, the recombinant ICC-1132 protein forms virus-like particles that were found to be highly immunogenic in preclinical studies of mice and monkeys. Twenty healthy adult volunteers received a 20- or a 50-μg dose of alum-adsorbed ICC-1132 administered intramuscularly at 0, 2, and 6 months. The majority of volunteers in the group receiving the 50-μg dose developed antibodies to CS repeats as well as to HBc. Malaria-specific T cells that secreted gamma interferon were also detected after a single immunization with ICC-1132-alum. These studies support ICC-1132 as a promising malaria vaccine candidate for further clinical testing using more-potent adjuvant formulations and confirm the potential of modified HBc virus-like particles as a delivery platform for vaccines against other human pathogens.
The
Streptococcus gordonii
Surface Proteins GspB and Hsa Mediate Binding to Sialylated Carbohydrate Epitopes on the Platelet Membrane Glycoprotein Ibα
Authors: Bensing Barbara A. , López José A. , Sullam Paul M. 
Published: October 2004

ABSTRACT

Platelet binding by
Streptococcus gordonii
strain M99 is dependent on expression of the cell wall-anchored glycoprotein GspB. This large cell surface protein is exported from the M99 cytoplasm via a dedicated transport system that includes SecA2 and SecY2. GspB is highly similar to Hsa, a protein expressed by
S. gordonii
Challis that has been characterized as a sialic acid binding hemagglutinin. In this study, we compared the contribution of GspB and Hsa to the adherence of
S. gordonii
to selected glycoproteins. Our results indicate that GspB can mediate binding to a variety of sialylated glycoproteins. GspB facilitates binding to carbohydrates bearing sialic acid in either α(2-3) or α(2-6) linkages, with a slight preference for α(2-3) linkages. Furthermore, GspB readily mediates binding to sialic acid residues on immobilized glycocalicin, the extracellular portion of the platelet membrane glycoprotein (GP) Ibα (the ligand binding subunit of the platelet von Willebrand factor receptor complex GPIb-IX-V). Although Hsa is required for the binding of
S. gordonii
Challis to sialic acid, most of the Hsa expressed by Challis is retained in the cytoplasm. The deficiency in export is due, at least in part, to a nonsense mutation in
secA2
. Hsa export can be enhanced by complementation with
secA2
from M99, which also results in significantly greater binding to sialylated glycoproteins, including glycocalicin. The combined results indicate that GspB and Hsa contribute similar binding capabilities to M99 and Challis, respectively, but there may be subtle differences in the preferred epitopes to which these adhesins bind.
Association of
iss
and
iucA
, but Not
tsh
, with Plasmid-Mediated Virulence of Avian Pathogenic
Escherichia coli
Authors: Tivendale Kelly A. , Allen Joanne L. , Ginns Carol A. , Crabb Brendan S. , Browning Glenn F. 
Published: October 2004

ABSTRACT

Avian pathogenic
Escherichia coli
(APEC) is an economically important respiratory pathogen of chickens worldwide. Factors previously associated with the virulence of APEC include adhesins, iron-scavenging mechanisms, the production of colicin V (ColV), serum resistance, and temperature-sensitive hemagglutination, but virulence has generally been assessed by parenteral inoculation, which does not replicate the normal respiratory route of infection. A large plasmid, pVM01, is essential for virulence in APEC strain E3 in chickens after aerosol exposure. Here we establish the size of pVM01 to be approximately 160 kb and show that the putative virulence genes
iss
(increased serum survival) and
tsh
(temperature-sensitive hemagglutinin) and the aerobactin operon are on the plasmid. These genes were not clustered on pVM01 but, rather, were each located in quite distinct regions. Examination of APEC strains with defined levels of respiratory pathogenicity after aerosol exposure showed that both the aerobactin operon and
iss
were associated with high levels of virulence in APEC but that the possession of either gene was sufficient for intermediate levels of virulence. In constrast, the presence of
tsh
was not necessary for high levels of virulence. Thus, both the aerobactin operon and
iss
are associated with virulence in APEC after exposure by the natural route of infection. The similarities between APEC and extraintestinal
E. coli
infection in other species suggests that they may be useful models for definition of the role of these virulence genes and of other novel virulence genes that may be located on their virulence plasmids.