bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytokine Gene Expression in Innately Susceptible BALB/c Mice and Relatively Resistant C57BL/6 Mice during Infection with VirulentBurkholderia pseudomallei
Authors: Ulett Glen C. , Ketheesan Natkunam , Hirst Robert G. 
Published: July 2002

ABSTRACTProduction of cytokines including gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) is an important early-stage host response following infection with intracellular pathogens. Development of immunity to these pathogens is determined to a large extent by the timing and relative level of expression of the cytokines. Numerous studies have shown that early cytokine responses involving interleukin-12 (IL-12) and IFN-γ are important for resistance to intracellular pathogens, whereas responses involving IL-4 and IL-10 increase host susceptibility. These often-indistinct early cytokine responses influence the differentiation of naı̈ve CD4+T helper cells, which later develop into what have commonly been termed Th1- and Th2-type cells. The characterization of CD4+T-helper-cell responses as Th1 or Th2 type is based largely on the cytokine profiles during the specific phase and has been used in recent years to account for the innate resistance and susceptibility of different inbred strains of mice to several intracellular pathogens. Studies investigating cytokine production in terms of CD4+T-helper-cell polarization inBurkholderia pseudomalleiinfection have not been undertaken. In this study, we used semiquantitative reverse transcription-PCR to assess induction of cytokine mRNA in liver and spleen ofB. pseudomallei-susceptible BALB/c and relatively resistant C57BL/6 mice following infection with virulentB. pseudomallei. The levels of mRNA for IFN-γ, TNF-α, IL-1β, IL-6, IL-10, and IL-12 increased in both BALB/c and C57BL/6 mice 24 to 36 h after infection. A comparison of BALB/c and C57BL/6 responses revealed the relative levels of expression of mRNA for several of these cytokines, including IFN-γ, were greater in BALB/c mice, suggesting a role for endotoxic shock and cytokine-mediated immunopathology in the development of acute melioidosis. Early induction of mRNA for the cytokines classically associated with development of Th1- and Th2-type responses was absent or minimal, and induction levels in both strains of mice were similar. During the specific phase, cytokine mRNA profiles occurred as a combination of Th1- and Th2-type patterns. Collectively, these results demonstrate that cytokine mRNA responses in BALB/c and C57BL/6 mice following infection with virulentB. pseudomalleido not develop as polarized Th1- or Th2-type profiles. Considering the role of TNF-α and IFN-γ in the processes of endotoxic shock, these results also indicate that selected cytokines, while important for resistance toB. pseudomalleiinfection, are also potential contributors to immunopathology and the development of acute fulminating disease.
An Immunoglobulin Superfamily-Like Domain Unique to the
Yersinia pseudotuberculosis
Invasin Protein Is Required for Stimulation of Bacterial Uptake via Integrin Receptors
Authors: Dersch Petra , Isberg Ralph R. 
Published: July 2002

ABSTRACT

The binding of the
Yersinia pseudotuberculosis
and
Yersinia enterocolitica
invasin proteins to β
1
integrin receptors allows internalization of these organisms by cultured cells. The C-terminal 192-residue superdomain of the
Y. pseudotuberculosis
invasin is necessary and sufficient for integrin recognition, while a region located outside, and N-terminal to, this superdomain strongly enhances the efficiency of bacterial uptake. Within the enhancer region is a domain called D2 that allows invasin-invasin interaction. To investigate the role of the enhancer region, bacterial cell binding and entry mediated by the
Y. pseudotuberculosis
invasin protein (invasin

pstb

) was compared to that of
Y. enterocolitica
invasin (invasin

ent

), which lacks the D2 self-association domain. Invasin

ent

was shown to be unable to promote self-interaction, using the DNA binding domain of λ repressor as a reporter. Furthermore, two genetically engineered in-frame deletion mutations that removed D2 from invasin

pstb

were significantly less proficient than wild-type invasin

pstb

at promoting uptake, although the amount of surface-exposed invasin as well as the cell binding capacity of the recombinant
Escherichia coli
strains remained similar. Competitive uptake assays showed that
E. coli
cells expressing invasin

pstb

had a significant advantage in the internalization process versus either
E. coli
cells expressing invasin

ent

or the invasin

pstb

derivatives deleted for D2, further demonstrating the importance of invasin self-interaction for the efficiency of invasin-mediated uptake.
Protection against VirulentMycobacterium aviumInfection following DNA Vaccination with the 35-Kilodalton Antigen Is Accompanied by Induction of Gamma Interferon-Secreting CD4+T Cells
Authors: Martin Ela , Kamath Arun T. , Triccas James A. , Britton Warwick J. 
Published: July 2002

ABSTRACTMycobacterium aviumis an opportunistic pathogen that primarily infects immunocompromised individuals, although the frequency ofM. aviuminfection is also increasing in the immunocompetent population. The antigen repertoire ofM. aviumvaries from that ofMycobacterium tuberculosis, with the immunodominant 35-kDa protein being present inM. aviumandMycobacterium lepraebut not in members of theM. tuberculosiscomplex. Here we show that a DNA vector encoding thisM. avium35-kDa antigen (DNA-35) induces protective immunity against virulentM. aviuminfection, and this protective effect persists over 14 weeks of infection. In C57BL/6 mice, DNA vaccines expressing the 35-kDa protein as a cytoplasmic or secreted protein, both induced strong T-cell gamma interferon (IFN-γ) and humoral immune responses. Furthermore, the antibody response was to conformational determinants, confirming that the vector-encoded protein had adopted the native conformation. DNA-35 immunization resulted in an increased activated/memory CD4+T-cell response, with an accumulation of CD4+CD44hiCD45RBloT cells and an increase in antigen-specific IFN-γ production. The protective effect of the DNA-35 vectors againstM. aviuminfection was comparable to that of vaccination withMycobacterium bovisBCG and significantly greater than that for previous treated infection withM. avium. These results illustrate the importance of the 35-kDa protein in the protective response toM. aviuminfection and indicate that DNA vaccination successfully promotes a sustained level of protection during chronicM. aviuminfection.
Adhesion Molecule Deficiencies IncreasePorphyromonas gingivalis-Induced Alveolar Bone Loss in Mice
Authors: Baker Pamela J. , DuFour Lisa , Dixon Mark , Roopenian Derry C. 
Published: July 2002

ABSTRACTAlveolar bone resorption can be induced in specific-pathogen-free mice by oral infection withPorphyromonas gingivalis(P. J. Baker, R. T. Evans, and D. C. Roopenian, Arch. Oral Biol. 39:1035–1040, 1994). Here we used a mouse strain, C57BL/6J, which is relatively resistant toP. gingivalis-induced bone loss to examine whether partial or complete deletion of various adhesion molecules would increase susceptibility. Complete deletion of P-selectin or nearly complete lack of expression of intercellular adhesion molecule 1 (ICAM-1) led to increased susceptibility to bone resorption after oral infection, while a hypomorphic defect in β2-integrins did not. Both the total amount of bone lost and the number of sites at which there was significant loss were increased in mice deficient in either ICAM-1 or P-selectin. Each of the three adhesion molecule deficiencies was sufficient to decreaseP. gingivalis-specific serum immunoglobulin G responses, but lower antibody titers did not lead to increased bone loss in partially β2-integrin-deficient mice. In conclusion, P-selectin and ICAM-1 deficiencies increase susceptibility to and severity of alveolar bone loss afterP. gingivalisinfection. This finding underscores the importance of innate immunity in protection againstP. gingivalis-induced alveolar bone resorption.
Carcinoembryonic Antigen Family Receptor Specificity of
Neisseria meningitidis
Opa Variants Influences Adherence to and Invasion of Proinflammatory Cytokine-Activated Endothelial Cells
Authors: Muenzner Petra , Dehio Christoph , Fujiwara Taku , Achtman Mark , Meyer Thomas F. , Gray-Owen Scott D. 
Published: July 2002

ABSTRACT

The carcinoembryonic antigen (CEA) family member CEACAM1 (previously called biliary glycoprotein or CD66a) was previously shown to function as a receptor that can mediate the binding of Opa protein-expressing
Neisseria meningitidis
to both neutrophils and epithelial cells. Since neutrophils and polarized epithelia have both been shown to coexpress multiple CEACAM receptors, we have now extended this work to characterize the binding specificity of meningococcal Opa proteins with other CEA family members. To do so, we used recombinant
Escherichia coli
expressing nine different Opa variants from three meningococcal strains and stably transfected cell lines expressing single members of the CEACAM family. These infection studies demonstrated that seven of the nine Opa variants bound to at least one CEACAM receptor and that binding to each of these receptors is sufficient to trigger the Opa-dependent bacterial uptake by these cell lines. The other two Opa variants do not appear to bind to either CEACAM receptors or heparan sulfate proteoglycan receptors, which are bound by some gonococcal Opa variants, thus implying a novel class of Opa proteins. We have also extended previous studies by demonstrating induction of CEACAM1 expression after stimulation of human umbilical vein endothelial cells with the proinflammatory cytokine tumor necrosis factor alpha, which is present in high concentrations during meningococcal disease. This induced expression of CEACAM1 leads to an increased Opa-dependent bacterial binding and invasion into the primary endothelia, implying that these interactions may play an important role in the pathogenesis of invasive meningococcal disease.
Correlations between Antibody Immune Responses at Different Mucosal Effector Sites Are Controlled by Antigen Type and Dosage
Authors: Externest Dörthe , Meckelein Barbara , Schmidt M. Alexander , Frey Andreas 
Published: July 2002

ABSTRACTMonitoring specific secretory immunoglobulin A (IgA) responses in the intestines after mucosal immunization or infection is impeded by the fact that sampling of small intestinal secretions requires invasive methods not feasible for routine diagnostics. Since IgA plasma cells generated after intragastric immunization are known to populate remote mucosal sites as well, secretory IgA responses at other mucosal surfaces may correlate to those in the intestines and could serve as proxy measures for IgA secretion in the gut. To evaluate the practicability of this approach, mice were immunized intragastrically with 0.2, 2, and 20 mg of ovalbumin plus 10 μg of cholera toxin, and the antigen-specific local secretory IgA responses in duodenal, ileal, jejunal, rectal, and vaginal secretions, saliva, urine, and feces, as well as serum IgG and IgA responses were analyzed by enzyme-linked immunosorbent assay. Correlation analysis revealed significant relationships between serum IgG and IgA, urinary IgA, salivary IgA, and secretory IgA in duodenal, jejunal, ileal, and rectal secretions for the 0.2-mg but not for the 20-mg ovalbumin dose. Fecal samples were poor predictors for intestinal antiovalbumin IgA responses, and no correlations could be established for cholera toxin, neither between local anti-cholera toxin levels nor to the antiovalbumin responses. Thus, specific IgA in serum, saliva, or urine can serve as a predictor of the release of specific IgA at intestinal surfaces after intragastric immunization, but the lack of correlations for high ovalbumin doses and for cholera toxin indicates a strong dependency on antigen type and dosage for these relationships.
Selection of Recombinant Antibodies Specific for Pathogenic
Streptococcus suis
by Subtractive Phage Display
Authors: de Greeff Astrid , van Alphen Loek , Smith Hilde E. 
Published: July 2002

ABSTRACT

A semisynthetic antibody phage display library was used to select recombinant antibodies directed against surface components of a pathogenic strain of
Streptococcus suis
serotype 2 and against extracellular factor (EF), a protein known to be exclusively associated with pathogenic
S. suis
serotype 2 strains. Three distinct monoclonal phage antibodies directed against conformational epitopes of surface protein components of
S. suis
were selected. In addition, three different monoclonal phage antibodies were isolated that recognized EF. To isolate antibody fragments that recognize epitopes specific for a pathogenic
S. suis
serotype 2 strain, compared to a nonpathogenic serotype 2 strain, we applied a subtractive selection procedure. With this procedure, only one distinct phage antibody was found, and it was shown to be directed against EF. This demonstrates the selectivity of the applied procedure and confirms that EF is indeed differentially expressed by pathogenic and nonpathogenic strains. It also shows that EF is a very dominant antigen in phage antibody selections.
Genetic Locus for Streptolysin S Production by Group A Streptococcus
Authors: Nizet Victor , Beall Bernard , Bast Darrin J. , Datta Vivekananda , Kilburn Laurie , Low Donald E. , De Azavedo Joyce C. S. 
Published: July 2002

ABSTRACT

Group A streptococcus (GAS) is an important human pathogen that causes pharyngitis and invasive infections, including necrotizing fasciitis. Streptolysin S (SLS) is the cytolytic factor that creates the zone of beta-hemolysis surrounding GAS colonies grown on blood agar. We recently reported the discovery of a potential genetic determinant involved in SLS production,
sagA
, encoding a small peptide of 53 amino acids (S. D. Betschel, S. M. Borgia, N. L. Barg, D. E. Low, and J. C. De Azavedo, Infect. Immun. 66:1671–1679, 1998). Using transposon mutagenesis, chromosomal walking steps, and data from the GAS genome sequencing project (
www.genome.ou.edu/strep.html
), we have now identified a contiguous nine-gene locus (
sagA
to
sagI
) involved in SLS production. The
sag
locus is conserved among GAS strains regardless of M protein type. Targeted plasmid integrational mutagenesis of each gene in the
sag
operon resulted in an SLS-negative phenotype. Targeted integrations (i) upstream of the
sagA
promoter and (ii) downstream of a terminator sequence after
sagI
did not affect SLS production, establishing the functional boundaries of the operon. A rho-independent terminator sequence between
sagA
and
sagB
appears to regulate the amount of
sagA
transcript produced versus transcript for the entire operon. Reintroduction of the nine-gene
sag
locus on a plasmid vector restored SLS activity to the nonhemolytic
sagA
knockout mutant. Finally, heterologous expression of the intact
sag
operon conferred the SLS beta-hemolytic phenotype to the nonhemolytic
Lactococcus lactis
. We conclude that gene products of the GAS
sag
operon are both necessary and sufficient for SLS production. Sequence homologies of
sag
operon gene products suggest that SLS is related to the bacteriocin family of microbial toxins.
Nonopsonic Phagocytosis of Zymosan andMycobacterium kansasiiby CR3 (CD11b/CD18) Involves Distinct Molecular Determinants and Is or Is Not Coupled with NADPH Oxidase Activation
Authors: Le Cabec Véronique , Cols Carine , Maridonneau-Parini Isabelle 
Published: July 2002

ABSTRACTComplement receptor type 3 (CR3) was initially described as an opsonic receptor. Subsequently, CR3-mediated lectin-sugar recognition mechanisms have been shown to play a major role in the nonopsonic phagocytosis of several pathogens, among themMycobacterium tuberculosis. Little is known about the binding and signal transduction mechanisms operating during nonopsonic ingestion through CR3 of different microorganisms. In the present study, we used CHO cells stably transfected with CR3 to show that CR3 was able to mediate internalization of zymosan and pathogenic mycobacteria (Mycobacterium kansasiiandMycobacterium avium) but not that of nonpathogenic species (Mycobacterium smegmatisandMycobacterium phlei). A combination of mannan and β-glucan inhibited the phagocytosis of zymosan but had no effect onM. kansasiiingestion. Among six monoclonal antibodies (MAbs) directed against the CD11b subunit of CR3 that decreased zymosan ingestion, only three inhibitedM. kansasiiphagocytosis. In particular, MAbs known to block the CR3 lectin site affected only internalization of zymosan. Using U937 macrophages, we observed that zymosan ingestion through CR3 induced superoxide production measured by cytochromecreduction and by translocation of the NADPH oxidase cytosolic component p47phox to the phagosomal membrane, whereas phagocytosis of viable or heat-killedM. kansasiidid not. Furthermore, lack of superoxide anion production during phagocytosis ofM. kansasiiwas not due to inhibition of NADPH oxidase per se or superoxide anion scavenging. Together, our results indicate that (i) nonopsonic phagocytosis of zymosan andM. kansasiiby CR3 implicates different molecular mechanisms involving multiple and distinct epitopes of CD11b and (ii) CR3 may transduce different cellular responses depending on the sites mediating nonopsonic phagocytosis.
Sunlight-Induced Propagation of the Lysogenic Phage Encoding Cholera Toxin
Authors: Faruque Shah M. , Asadulghani  , Rahman M. Mostafizur , Waldor Matthew K. , Sack David A. 
Published: July 2002

ABSTRACT

In toxigenic
Vibrio cholerae
, the cholera enterotoxin (CT) is encoded by CTXΦ, a lysogenic bacteriophage. The propagation of this filamentous phage can result in the origination of new toxigenic strains. To understand the nature of possible environmental factors associated with the propagation of CTXΦ, we examined the effects of temperature, pH, salinity, and exposure to direct sunlight on the induction of the CTX prophage and studied the transmission of the phage to potential recipient strains. Exposure of cultures of CTXΦ lysogens to direct sunlight resulted in ∼10,000-fold increases in phage titers. Variation in temperature, pH, or salinity of the culture did not have a substantial effect on the induction of the prophage, but these factors influenced the stability of CTXΦ particles. Exposure of mixed cultures of CTXΦ lysogens and potential recipient strains to sunlight significantly increased both the in vitro and in vivo (in rabbit ileal loops) transduction of the recipient strains by CTXΦ. Included in these transduction experiments were two environmental nontoxigenic (CTXΦ
−
) strains of
V. cholerae
O139. These two O139 strains were transduced at high efficiency by CTXΦ, and the phage genome integrated into the O139 host chromosome. The resulting CTXΦ lysogens produced biologically active CT both in vitro and in rabbit ileal loops. This finding suggests a possible mechanism explaining the origination of toxigenic
V. cholerae
O139 strains from nontoxigenic progenitors. This study indicates that sunlight is a significant inducer of the CTX prophage and suggests that sunlight-induced transmission of CTXΦ may constitute part of a natural mechanism for the origination of new toxigenic strains of
V. cholerae
.
Interleukin 18 Restores Defective Th1 Immunity toCandida albicansin Caspase 1-Deficient Mice
Authors: Mencacci Antonella , Bacci Angela , Cenci Elio , Montagnoli Claudia , Fiorucci Sabrina , Casagrande Andrea , Flavell Richard A. , Bistoni Francesco , Romani Luigina 
Published: July 2002

ABSTRACTCaspase 1, formerly designated interleukin 1β (IL-1β)-converting enzyme, processes pro-IL-1β and pro-IL-18 to yield active cytokines that play a pivotal role in inflammation and cell activation. We show here the effect of caspase 1 deficiency on the inflammatory and adaptive immune responses to the fungusCandida albicans. Caspase 1 deficiency did not affect susceptibility to primary systemic infection with the fungus, as revealed by survival and fungal growth. However, Th1-mediated resistance to reinfection was greatly impaired in caspase 1-deficient mice, and this correlated with low-level production of IL-12 and gamma interferon. Early in infection, production of these cytokines and that of tumor necrosis factor alpha, IL-6, and, interestingly, IL-1β occurred normally in caspase 1-deficient mice, while that of IL-18 was severely impaired. Exogenous administration of IL-18, more than IL-12, restored the Th1-mediated resistance to the infection. We conclude that, while caspase 1 is not indispensable for release of mature IL-1β in candidiasis, the caspase 1-dependent production of IL-18 may represent an important and novel pathway for the expression of sustained Th1 reactivity to the fungus.
Group A Streptococcal
rofA
Gene Is Involved in the Control of Several Virulence Genes and Eukaryotic Cell Attachment and Internalization
Authors: Beckert Susanne , Kreikemeyer Bernd , Podbielski Andreas 
Published: July 2002

ABSTRACT

The serotype M6 group A streptococcal RofA regulator was previously shown to exert a direct positive control of protein F1 expression and, concomitantly, fibronectin binding. Using a serotype M6
rofA
mutant, we demonstrate here that this regulator has a potentially indirect negative influence on the expression of the
mga
,
emm
6,
pel-sagA
, and
speA
virulence genes. Additionally, the
rofA
mutant exhibited reduced eukaryotic cell internalization rates in combination with decreased host cell viability.
Critical Role for Tumor Necrosis Factor Alpha in Controlling the Number of Lumenal Pathogenic Bacteria and Immunopathology in Infectious Colitis
Authors: Gonçalves Nathalie S. , Ghaem-Maghami Marjan , Monteleone Giovanni , Frankel Gad , Dougan Gordon , Lewis David J. M. , Simmons Cameron P. , MacDonald Thomas T. 
Published: July 2002

ABSTRACTInfection of mice with the intestinal bacterial pathogenCitrobacter rodentiumresults in colonic mucosal hyperplasia and a local Th1 inflammatory response similar to that seen in mouse models of inflammatory bowel disease. In these latter models, and in patients with Crohn's disease, neutralization of tumor necrosis factor alpha (TNF-α) is of therapeutic benefit. Since there is no information on the role of TNF-α in either immunity to noninvasive bacterial pathogens or on the role of TNF-α in the immunopathology of infectious colitis, we investigatedC. rodentiuminfection in TNFRp55−/−mice. In TNFRp55−/−mice, there were higher colonic bacterial burdens, but the organisms were cleared at the same rate as C57BL/6 mice, showing that TNF-α is not needed for protective antibacterial immunity. The most striking feature of infection in TNFRp55−/−mice, however, was the markedly enhanced pathology, with increased mucosal weight and thickness, increased T-cell infiltrate, and a markedly greater mucosal Th1 response. Interleukin-12 p40 transcripts were markedly elevated inC. rodentium-infected TNFRp55−/−mice, and this was associated with enhanced mucosal STAT4 phosphorylation. TNF-α is not obligatory for protective immunity toC. rodentiumin mice; however, it appears to play some role in downregulating mucosal pathology and Th1 immune responses.