bluuebunny/crossref_metadata_2025_split huggingface dataset:
T-Cell-Stimulating Protein A Elicits Immune Responses during Meningococcal Carriage and Human Disease
Authors: Robinson Karen , Wooldridge Karl G. , Wells Damien B. , Hasan Amal , Todd Ian , Robins Adrian , James Richard , Ala'Aldeen Dlawer A. A. 
Published: July 2005

ABSTRACTIn recognition of the need for immunological memory-inducing components for futureNeisseria meningitidisgroup B vaccines, we previously searched the proteome ofN. meningitidisand identified T-cell-stimulating protein A (TspA). This study was designed to confirm the immunogencity of TspA and to examine the subset of T-helper cell responses to the protein in patients and nasopharyngeal carriers. ThetspAgene was reconstructed, cloned, and expressed inEscherichia coli, and the recombinant TspA (rTspA) protein was affinity purified. T-cell proliferative responses to rTspA were detected in the peripheral blood mononuclear cells (PBMCs) of convalescent patients and carriers, confirming that TspA-specific T-cell responses were stimulated by invasive disease and nasopharyngeal colonization. Following stimulation of PBMCs with meningococcal lysate, increased frequencies of both Th1 and Th2 cells were observed, indicating that, as during carriage, invasive meningococcal disease induced an unbiased T-helper subset response. A similar unbiased T-helper response was also detected against rTspA in the PBMCs of convalescent patients. The response of PBMCs from the carriers to TspA stimulation, however, was very weak, and the frequencies of cytokine-positive CD4 cells were not significantly greater than the frequencies in unstimulated control cultures. All of the patients and carriers responded with serum antimeningococcal immunoglobulin G (IgG) antibodies, while four of six samples from patients and 5 of 14 samples from carriers contained detectable anti-rTspA IgG antibodies. Taken together, the results of this study confirmed the immunogenicity of TspA in humans during natural meningococcal infection, and therefore, TspA is worthy of further investigation as a possible T-cell stimulating component of future vaccines.
Protection by Natural Human Immunoglobulin M Antibody to Meningococcal Serogroup B Capsular Polysaccharide in the Infant Rat Protection Assay Is Independent of Complement-Mediated Bacterial Lysis
Authors: Toropainen Maija , Saarinen Leena , Wedege Elisabeth , Bolstad Karin , Michaelsen Terje E. , Aase Audun , Käyhty Helena 
Published: July 2005

ABSTRACTNeisseria meningitidis, an important cause of bacterial meningitis and septicemia worldwide, is associated with high mortality and serious sequelae. Natural immunity against meningococcal disease develops with age, but the specificity and functional activity of natural antibodies associated with protection are poorly understood. We addressed this question by using a selected subset of prevaccination sera (n= 26) with convergent or discrepant serum bactericidal activity (SBA) and infant rat protective activity (IRPA) against the serogroup B meningococcal strain 44/76-SL (B:15:P1.7,16) from Icelandic teenagers (B. A. Perkins et al., J. Infect. Dis. 177:683-691, 1998). The sera were analyzed by opsonophagocytic activity (OPA) assay, immunoblotting, immunoglobulin G (IgG) quantitation against live meningococcal cells by flow cytometry, and enzyme immunosorbent assay (EIA). High levels of SBA and OPA were reflected in distinct IgG binding to major outer membrane proteins and/or lipopolysaccharide in immunoblots. However, we could not detect any specific antibody patterns on blots that could explain IRPA. Only IgM antibody to group B capsular polysaccharide (B-PS), measured by EIA, correlated positively (r= 0.76,P< 0.001) with IRPA. Normal human sera (NHS;n= 20) from healthy Finnish children of different ages (7, 14, and 24 months and 10 years) supported this finding and showed an age-related increase in IRPA that coincided with the acquisition of B-PS specific IgM antibody. The protection was independent of complement-mediated bacterial lysis, as detected by the inability of NHS to augment SBA in the presence of human or infant rat complement and the equal protective activity of NHS in rat strains with fully functional or C6-deficient complement.
Fungal Antigens Expressed during Invasive Aspergillosis
Authors: Denikus Nicole , Orfaniotou Foteini , Wulf Gerald , Lehmann Paul F. , Monod Michel , Reichard Utz 
Published: July 2005

ABSTRACTRabbits that had been infected intravenously with conidiospores ofAspergillus fumigatuswere used as sources of antibody for screening a λ phage cDNA expression library. The cDNA was derived fromA. fumigatusmRNA that had been extracted from newly formed, germling hyphae. Thirty-six antigens were identified using antisera from six rabbits. Though many of these antigens were expected to be intracellular proteins because their genes did not encode a signal sequence, the antisera showed consistently a stronger immunoblot reaction with a cell fraction enriched for the fungal cell wall than with a fraction of predominantly intracellular components. Antibodies to eight antigens, including the glycosylhydrolase Asp f 16, were produced by more than one rabbit. In current vaccine studies, Asp f 16 is the only single antigen which has been reported to be capable of inducing protection against invasive aspergillosis in mice (S. Bozza et al., Microb. Infect.4:1281-1290, 2002). Enolase andAspergillusHSP90 were detected also; their homologues inCandida albicanshave been tested as vaccines and have been reported to provide a partially protective response against invasive candidiasis in mice. TheAspergillusantigens reported here may have value both in diagnostic tests for different forms of aspergillosis and as vaccine candidates for protection against invasive disease.
Conditions Influencing the Efficacy of Vaccination with Live Organisms againstLeishmania majorInfection
Authors: Tabbara Khaled S. , Peters Nathan C. , Afrin Farhat , Mendez Susana , Bertholet Sylvie , Belkaid Yasmine , Sacks David L. 
Published: July 2005

ABSTRACTNumerous experimental vaccines have been developed with the goal of generating long-term cell-mediated immunity to the obligate intracellular parasiteLeishmania major, yet inoculation with live, wild-typeL. majorremains the only successful vaccine in humans. We examined the expression of immunity at the site of secondary, low-dose challenge in the ear dermis to determine the kinetics of parasite clearance and the early events associated with the protection conferred by vaccination with liveL. majororganisms in C57BL/6 mice. Particular attention was given to the route of vaccination. We observed that the rapidity, strength, and durability of the memory response following subcutaneous vaccination with live parasites in the footpad are even greater than previously appreciated. Antigen-specific gamma interferon (IFN-γ)-producing T cells infiltrate the secondary site by 1.5 weeks, and viable parasites are cleared as early as 2.5 weeks following rechallenge, followed by a rapid drop in IFN-γ+CD4+cell numbers in the site. In comparison, intradermal vaccination with live parasites in the ear generates immunity that is delayed in effector cell recruitment to the rechallenge site and in the clearance of parasites from the site. This compromised immunity was associated with a rapid recruitment of interleukin-10 (IL-10)-producing CD4+T cells to the rechallenge site. Treatment with anti-IL-10-receptor or anti-CD25 antibody enhanced early parasite clearance in ear-vaccinated mice, indicating that chronic infection in the skin generates a population of regulatory cells capable of influencing the level of resistance to reinfection. A delicate balance of effector and regulatory T cells may be required to optimize the potency and durability of vaccines againstLeishmaniasisand other intracellular pathogens.
Growth Characteristics of and Virulence Factor Production by Group A
Streptococcus
during Cultivation in Human Saliva
Authors: Shelburne Samuel A. , Granville Chanel , Tokuyama Maria , Sitkiewicz Izabela , Patel Payal , Musser James M. 
Published: July 2005

ABSTRACT

Group A
Streptococcus
(GAS) commonly infects the human oropharynx, but the initial molecular events governing this process are poorly understood. Saliva is a major component of the innate and acquired immune defense in this anatomic site. Although landmark studies were done more than 60 years ago, investigation of GAS-saliva interaction has not been addressed extensively in recent years. Serotype M1 GAS strain MGAS5005 cultured in human saliva grew to ∼10
7
CFU/ml and, remarkably, maintained this density for up to 28 days. Strains of several other M-protein serotypes had similar initial growth patterns but did not maintain as high a CFU count during prolonged culture. As revealed by analysis of the growth of isogenic mutant strains, the ability of GAS to maintain high numbers of CFU/ml during the prolonged stationary phase in saliva was dependent on production of streptococcal inhibitor of complement (Sic) and streptococcal pyrogenic exotoxin B (SpeB). During cultivation in human saliva, GAS had growth-phase-dependent production of multiple proven and putative extracellular virulence factors, including Sic, SpeB, streptococcal pyrogenic exotoxin A, Mac protein, and streptococcal phospholipase A
2
. Our results clearly show that GAS responds in a complex fashion to growth in human saliva, suggesting that the molecular processes that enhance colonization and survival in the upper respiratory tract of humans are well under way before the organism reaches the epithelial cell surface.
Characterization of theHelicobacter pyloriCysteine-Rich Protein A as a T-Helper Cell Type 1 Polarizing Agent
Authors: Deml Ludwig , Aigner Michael , Decker Jochen , Eckhardt Alexander , Schütz Christian , Mittl Peer R. E. , Barabas Sascha , Denk Stefanie , Knoll Gertrud , Lehn Norbert , Schneider-Brachert Wulf 
Published: July 2005

ABSTRACTPredominant T-helper 1 (Th1) responses with increased gamma interferon (IFN-γ) levels have been proposed to play an important role inHelicobacter pylori-induced gastritis and peptic ulceration. However, bacterial factors contributing to the initiation of Th1 polarization ofH. pylori-specific immune responses have not been characterized in detail thus far. We report here on the identification ofHelicobactercysteine-rich protein A (HcpA) as a novel proinflammatory and Th1-promoting protein. The capacity of HcpA to induce immune activation was studied in splenocyte cultures of naiveH. pylori-negative mice. HcpA stimulated the release of high concentrations of the proinflammatory and Th1-promoting cytokines interleukin-6 (IL-6) and IFN-γ, in addition to significant levels of IL-12, tumor necrosis factor alpha, and IL-10. The observed cytokine profile was comparable to that induced by lipopolysaccharide but differed in the kinetics and maximum levels of cytokine production. In addition, HcpA-induced cytokine release resembled that observed upon incubation withH. pyloriexcept for IL-10, which was only moderately released upon HcpA stimulation. Both HcpA- andH. pylori-mediated IFN-γ production was drastically reduced by a neutralizing antibody against IL-12 but not by an anti-IL-2 antibody. Thus, HcpA seems to represent a novel bacterial virulence factor triggering the release of a concerted set of cytokines to instruct the adaptive immune system for the initiation of proinflammatory and Th1-biased immunity.
Influence of Na+, Dicarboxylic Amino Acids, and pH in Modulating the Low-Calcium Response ofYersinia pestis
Authors: Brubaker Robert R. 
Published: July 2005

ABSTRACTThe virulence of yersiniae is promoted in part by shared ≈70-kb plasmids (pCD inYersinia pestisand pYV in enteropathogenicYersinia pseudotuberculosisandYersinia enterocolitica) that mediate a low-calcium response. This phenotype is characterized at 37°C by either bacteriostasis in Ca2+-deficient medium with expression of pCD/pYV-encoded virulence effectors (Yops and LcrV) or vegetative growth and repression of Yops and LcrV with ≥2.5 mM Ca2+(Lcr+). Regulation of Yops and LcrV is well defined but little is known about bacteriostasis other than that Na+plusl-glutamate promotes prompt restriction ofY. pestis. As shown here,l-aspartate substituted forl-glutamate in this context but only Na+exacerbated the nutritional requirement for Ca2+. Bacteriostasis ofY. pestis(but not enteropathogenic yersiniae) was abrupt in Ca2+-deficient medium at neutral to slightly alkaline pH (7.0 to 8.0), although increasing the pH to 8.5 or 9.0, especially with added Na+(but notl-glutamate), facilitated full-scale growth. Addedl-glutamate (but not Na+) favored Ca2+-independent growth at acidic pH (5.0 to 6.5). Yops and LcrV were produced in Ca2+-deficient media at pH 6.5 to 9.0 regardless of the presence of added Na+orl-glutamate, although their expression at alkaline pH was minimal. Resting Ca2+-starved Lcr+cells ofY. pestissupplied withl-glutamate first excreted and then destroyedl-aspartate. These findings indicate that expression of Yops and LcrV is necessary but not sufficient for bacteriostasis of Ca2+-starved yersiniae and suggest that abrupt restriction ofY. pestisrequires Na+and the known absence of aspartate ammonia-lyase in this species.
Identification and Characterization of the Locus for Diffuse Adherence, Which Encodes a Novel Afimbrial Adhesin Found in Atypical EnteropathogenicEscherichia coli
Authors: Scaletsky Isabel C. A. , Michalski Jane , Torres Alfredo G. , Dulguer Michelle V. , Kaper James B. 
Published: July 2005

ABSTRACTThe O26 serogroup of enteropathogenicEscherichia coli(EPEC) is one of the serogroups most frequently implicated in infant diarrhea and is also common among enterohemorrhagicE. coli(EHEC) strains. The most common O26 strains belong to EPEC/EHEC serotype O26:H11 and are generally Shiga toxin (Stx) positive. Stx-negativeE. colistrains that are negative for the EPEC EAF plasmid and bundle-forming pilus (Bfp) are classified as atypical EPEC. Here, we report a novel adhesin present in anstx-negativebfpA-negative atypical EPEC O26:H11 strain isolated from an infant with diarrhea. A cloned 15-kb genomic region from this strain, designated thelocus fordiffuseadherence (lda), confers diffuse adherence on HEp-2 cells when expressed inE. coliK-12. Sequence analysis ofldarevealed a G+C content of 46.8% and 15 open reading frames sharing homology with theE. coliK88faeand CS31Aclpfimbrial operons. Theldaregion is part of a putative 26-kb genomic island inserted into theproPgene of theE. colichromosome. Hybridization studies have demonstrated the prevalence of the minor structural subunit gene,ldaH, acrossE. coliserogroups O5, O26, O111, and O145. A second plasmid-encoded factor that contributed to the Hep-2 adherence of this strain was also identified but was not characterized. Null mutations that abolish adherence to HEp-2 cells can be restored by plasmid complementation. Antiserum raised against the major structural subunit, LdaG, recognizes a 25-kDa protein from crude heat-extracted protein preparations and inhibits the adherence of theE. coliDH5αlda+clone to HEp-2 cells. Electron microscopy revealed a nonfimbrial structure surrounding the bacterial cell.
Pathoadaptive Mutation That Mediates Adherence of Shiga Toxin-Producing
Escherichia coli
O111
Authors: Torres Alfredo G. , Vazquez-Juarez Roberto C. , Tutt Christopher B. , Garcia-Gallegos J. Gerardo 
Published: July 2005

ABSTRACT

The adherence of pathogenic
Escherichia coli
strains to intestinal epithelium is essential for initiation of infection. The
cad
operon encodes the lysine decarboxylase (LDC) system responsible for
metabolizing lysine, and this operon has been proposed as an
antivirulence mechanism in enteroinvasive
E. coli
and
Shigella flexneri
and as a factor mediating
E. coli
O157:H7 adherence. We sought to determine whether the LDC activity was
present in a phylogenetically characterized collection of diarrheagenic
E. coli
(DEC) strains and to establish whether its expression
was associated with their adherence to tissue culture cells. LDC
activity was found in most of the pathogenic
E. coli
strains
tested and was absent from Shiga toxin-producing
E. coli
(STEC) O111 strains (DEC pathotype 8). Analysis of the
cad
region in these O111 strains indicates that the operon has been
rearranged and some of the genes are either missing or disrupted. A
similar rearrangement was found in an
E. coli
O111:H8 strain
recently isolated from an outbreak in Texas. Complementation of the
LDC-negative strains with the
cad
operon in
trans
restored the LDC activity and resulted in a reduction in adherence to
tissue culture cells. Initial analysis of the protein profiles on the
surface of the O111 strains indicates that the LDC activity has an
effect on the expression of the adhesin intimin. Cadaverine had a
slight effect on LDC-negative strain adhesion but none on intimin
expression. Our data suggest that this pathoadaptive mutation is an
important mechanism to control functions potentially implicated in the
pathogenesis of these
organisms.
Species-Specific Inhibition of Cerebral Malaria in Mice Coinfected withPlasmodiumspp
Authors: Voza Tatiana , Vigário Ana M. , Belnoue Elodie , Grüner Anne Charlotte , Deschemin Jean-Christophe , Kayibanda Michèle , Delmas Florian , Janse Chris J. , Franke-Fayard Blandine , Waters Andrew P. , Landau Irène , Snounou Georges , Rénia Laurent 
Published: July 2005

ABSTRACTRecent epidemiological observations suggest that clinical evolution ofPlasmodium falciparuminfections might be influenced by the concurrent presence of anotherPlasmodiumspecies, and such mixed-species infections are now known to occur frequently in residents of most areas of endemicity. We used mice infected withP. bergheiANKA (PbA), a model for cerebral malaria (CM), to investigate the influence of experimental mixed-species infections on the expression of this pathology. Remarkably, the development of CM was completely inhibited by the simultaneous presence ofP. yoelii yoeliibut not that ofP. vinckeior another line ofP. berghei. In the protected coinfected mice, the accumulation of CD8+T cells in the brain vasculature, a pivotal step in CM pathogenesis, was found to be abolished. Protection from CM was further found to be associated with species-specific suppression of PbA multiplication. These observations establish the concept of mixedPlasmodiumspecies infections as potential modulators of pathology and open novel avenues to investigate mechanisms implicated in the pathogenesis of malaria.
Independent Protective Effects for Tumor Necrosis Factor and Lymphotoxin Alpha in the Host Response toListeria monocytogenesInfection
Authors: Roach D. R. , Briscoe H. , Saunders B. M. , Britton W. J. 
Published: July 2005

ABSTRACTAlthough the essential role of tumor necrosis factor (TNF) in resistance toListeria monocytogenesinfection is well established, the roles of the related cytokines lymphotoxin alpha (LTα) and lymphotoxin beta (LTβ) are unknown. Using C57BL/6 mice in which the genes for these cytokines were disrupted, we examined the contributions of TNF, LTα, and LTβ in the host response toListeria. To overcome the lack of peripheral lymph nodes in LTα−/−and LTβ−/−mice, bone marrow chimeras were constructed. TNF−/−and LTα−/−chimeras that lacked both secreted LTα3and membrane-bound LTα1β2and LTα2β1were highly susceptible and succumbed 4.5 and 6 days, respectively, after a low-dose infection (200 CFU). LTβ−/−chimeras, which lacked only membrane-bound LT, controlled the infection in a manner comparable to wild-type (WT) chimeras. TheListeria-specific proliferative and gamma interferon T-cell responses were equivalent in all five groups of infected mice (LTα−/−and LTβ−/−chimeras, WT chimeras, and TNF−/−and WT mice). TNF−/−mice and LTα−/−chimeras, however, failed to generate the discrete foci of lymphocytes and macrophages that are essential for bacterial elimination. Rather, aberrant necrotic lesions comprised predominantly of neutrophils with relatively few lymphocytes and macrophages were observed in the livers and spleens of TNF−/−and LTα−/−chimeras. Therefore, in addition to TNF, soluble LTα3plays a separate essential role in control of listerial infection through control of leukocyte accumulation and organization in infected organs.
The Multifunctional
Staphylococcus aureus
Autolysin Aaa Mediates Adherence to Immobilized Fibrinogen and Fibronectin
Authors: Heilmann Christine , Hartleib Jörg , Hussain Muzaffar S. , Peters Georg 
Published: July 2005

ABSTRACT

Staphylococci can cause a wide spectrum of infections, including endocarditis, osteomyelitis, and sepsis, which is reflected by the numerous virulence factors they produce, among them a recently identified new class of adhesins, namely, the multifunctional autolysins/adhesins. Here we report the identification and molecular characterization of Aaa, a novel autolysin/adhesin from
Staphylococcus aureus
. The gene encoding Aaa was cloned from the clinical isolate
Staphylococcus aureus
4074. DNA sequence analysis revealed that
aaa
encodes a deduced protein of 334 amino acids with a predicted molecular mass of 35.8 kDa. Aaa contains three N-terminal repetitive sequences that comprise features of a peptidoglycan-binding domain, the LysM domain. The expression of
aaa
by
Escherichia coli
and its subsequent characterization revealed that Aaa possesses bacteriolytic activity as well as adhesive properties, such as binding to extracellular matrix proteins. Real-time biomolecular interaction analysis demonstrated that the interaction of Aaa with fibrinogen, fibronectin, and vitronectin is dose dependent and saturable and occurs with a high affinity. Furthermore, we demonstrate that Aaa binds to the Aα and Bβ chains of fragment D of fibrinogen. Immunofluorescence microscopy revealed that Aaa is located at the cell surface. Finally, an
aaa
knockout mutant showed reduced adherence to surface-adsorbed fibrinogen and fibronectin, strongly suggesting a role for Aaa in the colonization of host factor-coated polymer surfaces and/or host tissue.
Effect of Skin Barrier Disruption on Immune Responses to Topically Applied Cross-Reacting Material, CRM197, of Diphtheria Toxin
Authors: Godefroy S. , Peyre M. , Garcia N. , Muller S. , Sesardic D. , Partidos C. D. 
Published: July 2005

ABSTRACTThe high accessibility of the skin and the presence of immunocompetent cells in the epidermis makes this surface an attractive route for needle-free administration of vaccines. However, the lining of the skin by the stratum corneum is a major obstacle to vaccine delivery. In this study we examined the effect of skin barrier disruption on the immune responses to the cross-reacting material CRM197, a nontoxic mutant of diphtheria toxin (DTx) that is considered as a vaccine candidate. Application of CRM197, together with cholera toxin (CT), onto the tape-stripped skin of mice elicited antibody responses that had anti-DTx neutralizing activity. Vaccine delivery onto mildly ablated skin or intact skin did not elicit any detectable anti-CRM197antibodies. Mice immunized with CRM197alone onto the tape-stripped skin mounted a vigorous antigen-specific proliferative response. In contrast, the induction of cellular immunity after CRM197deposition onto mildly ablated or intact skin was adjuvant dependent. Furthermore, epidermal cells were activated and underwent apoptosis that was more pronounced when the stratum corneum was removed by tape stripping. Overall, these findings highlight the potential for transcutaneous delivery of CRM197and establish a correlation between the degree of barrier disruption and levels of antigen-specific immune responses. Moreover, these results provide the first evidence that the development of a transcutaneous immunization strategy for diphtheria, based on simple and practical methods to disrupt the skin barrier, is feasible.