bluuebunny/crossref_metadata_2025 huggingface dataset:
Visceral Leishmaniasis in Mice Devoid of Tumor Necrosis Factor and Response to Treatment
Authors: Murray Henry W. , Jungbluth Achim , Ritter Erika , Montelibano Christina , Marino Michael W.
Published: July 2002

Tumor necrosis factor (TNF)-deficient mice were challenged withLeishmania donovanito characterize TNF in the response of visceral intracellular infection to antileishmanial chemotherapy. In wild-type controls (i) liver infection peaked at week 2 and resolved, (ii) discrete liver granulomas developed at weeks 2 to 4 and involuted, and (iii) leishmanicidal responses to antimony (Sb), amphotericin B (AmB), and miltefosine were intact. In TNF knockout (KO) mice (i) initial liver infection was unrestrained, plateaued, and then declined somewhat by week 6, (ii) an absent early granulomatous reaction abruptly accelerated with striking tissue inflammation, widespread hepatic necrosis, and 100% mortality by week 10, and (iii) while the initial response to AmB and miltefosine was intact, killing induced by Sb therapy was reduced by >50%. Although initial AmB treatment during weeks 2 to 3 killed 98% of liver parasites, 75% of AmB-treated KO mice subsequently relapsed and died by week 12; however, additional maintenance AmB preserved long-term survival. These results for a model of visceral infection indicate that endogenous TNF is required early on to control intracellularL. donovani, support granuloma development, and mediate optimal initial effects of Sb and prevent relapse after ordinarily curative AmB treatment. A compensatory, TNF-independent antileishmanial mechanism developed in TNF KO mice; however, its effect was uncontrolled fatal inflammation. Chemotherapeutic elimination of the parasite stimulus reversed the hyperinflammatory response and preserved survival.
Salmonella entericaSerovar Typhimurium-Induced Maturation of Bone Marrow-Derived Dendritic Cells
Authors: Svensson Mattias , Johansson Cecilia , Wick Mary Jo
Published: July 2002

Murine bone marrow-derived dendritic cells (DC) can phagocytose and processSalmonella entericaserovar Typhimurium for peptide presentation on major histocompatibility complex class I (MHC-I) and MHC-II molecules. To investigate if a serovar Typhimurium encounter with DC induces maturation and downregulates their ability to present antigens from subsequently encountered bacteria, DC were pulsed with serovar Typhimurium 24 h prior to coincubating withEscherichia coliexpressing the model antigen Crl-OVA. Quantitating presentation of OVA epitopes contained within Crl-OVA showed thatSalmonella-pulsed DC had a reduced capacity to process Crl-OVA-expressingE. colifor OVA(257-264)/Kband OVA(265-277)/I-Abpresentation. In addition, time course studies of DC pulsed with Crl-OVA-expressing serovar Typhimurium showed that OVA(257-264)/Kbcomplexes could stimulate CD8OVA T-hybridoma cells for <24 h following a bacterial pulse, while OVA(265-277)/I-Abcomplexes could stimulate OT4H T-hybridoma cells for >24 but <48 h. ThephoP-phoQvirulence locus of serovar Typhimurium also influenced the ability of DC to process Crl-OVA-expressing serovar Typhimurium for OVA(265-277)/I-Abpresentation but not for OVA(257-264)/Kbpresentation. Furthermore, pulsing of DC with serovar Typhimurium followed by incubation for 24 or 48 h altered surface expression of MHC-I, MHC-II, CD40, CD54, CD80, and CD86, generating a DC population with a uniform, high expression level of these molecules. Finally, neither the serovar TyphimuriumphoP-phoQlocus nor lipopolysaccharides (LPS) containing lipid A modifications purified fromphoPmutant strains had a different effect on DC maturation from that of wild-type serovar Typhimurium or purified wild-type LPS. Thus, these data show thatSalmonellaorSalmonellaLPS induces maturation of DC and that this process is not altered by theSalmonella phoPvirulence locus. However,phoPdid influence OVA(265-277)/I-Abpresentation by DC infected with Crl-OVA-expressing serovar Typhimurium when quantitated after 2 h of bacterial infection.
SclA, a Novel Collagen-Like Surface Protein ofStreptococcus pyogenes
Authors: Rasmussen Magnus , Edén Arvid , Björck Lars
Published: July 2002

Surface proteins ofStreptococcus pyogenesare important virulence factors. Here we describe a novel collagen-like surface protein, designated SclA (streptococcal collagen-like surface protein). ThesclAgene was identified in silico using the Streptococcal Genome Sequencing Project with the recently identified protein GRAB as the probe. SclA has a signal sequence and a cell wall attachment region containing the prototypic LPXTGX motif. The surface-exposed part of SclA contains a unique NH2-terminal domain of 73 amino acids, followed by a collagen-like region. ThesclAgene was found to be positively regulated by Mga, a transcriptional activator of severalS. pyogenesvirulence determinants. A mutant lacking cell wall-associated SclA was constructed and was found to be as effective as wild-type bacteria in platelet aggregation, survival in fresh human blood, and adherence to pharyngeal cells. ThesclAgene was found in all 12S. pyogenesstrains that were investigated using PCR. Sequence analysis revealed that the signal sequence and the cell wall attachment region are highly conserved. The collagen-like domain is variable in its NH2-terminal region and has conserved repeated domains in its COOH-terminal part. SclA proteins from most strains have additional proline-rich repeats spacing the collagen-like domain and the cell wall attachment sequence. The unique NH2-terminal region is hypervariable, but computer predictions indicate a common secondary structure, with two alpha helices connected by a loop region. Immune selection may explain the hypervariability in the NH2-terminal region, whereas the preserved secondary structure implies that this region has a common function. These features and the Mga regulation are shared with the M protein ofS. pyogenes. Moreover, as with the gene encoding the M protein, phylogenetic analysis indicates that horizontal gene transfer has contributed to the evolution ofsclA.
Identification oftgh-2, a Filarial Nematode Homolog ofCaenorhabditis elegans daf-7and Human Transforming Growth Factor β, Expressed in Microfilarial and Adult Stages ofBrugia malayi
Authors: Gomez-Escobar Natalia , Gregory William F. , Maizels Rick M.
Published: July 2002

A novel member of the transforming growth factor β (TGF-β) family has been identified in the filarial nematode parasiteBrugia malayiby searching the recently developed Expressed Sequence Tag (EST) database produced by the Filarial Genome Project. Designatedtgh-2, this new gene shows most similarity to a key product regulating dauer larva formation inCaenorhabditis elegans(DAF-7) and to the human down-modulatory cytokine TGF-β. Homology to DAF-7 extends throughout the length of the 349-amino-acid (aa) protein, which is divided into an N-terminal 237 aa, including a putative signal sequence, a 4-aa basic cleavage site, and a 108-aa C-terminal active domain. Similarity to human TGF-β is restricted to the C-terminal domain, over which there is a 32% identity between TGH-2 and TGF-β1, including every cysteine residue. Expression oftgh-2mRNA has been measured over the filarial life cycle. It is maximal in the microfilarial stage, with lower levels of activity around the time of molting within the mammal, but continues to be expressed by mature adult male and female parasites. Expression in both the microfilaria, which is in a state of arrested development, and the adult, which is terminally differentiated, indicates thattgh-2may play a role other than purely developmental. This is consistent with our observation that TGH-2 is secreted by adult worms in vitro. Recombinant TGH-2 expressed in baculovirus shows a low level of binding to TGF-β-receptor bearing mink lung epithelial cells (MELCs), which is partially inhibited (16 to 39%) with human TGF-β, and activates plasminogen activator inhibitor-1 transcription in MELCs, a marker for TGF-β-mediated transduction. Further tests will be required to establish whether the major role ofB. malayiTGH-2 (Bm-TGH-2) is to modulate the host immune response via the TGF-β pathway.
Micronemal Transport ofPlasmodiumOokinete Chitinases to the Electron-Dense Area of the Apical Complex for Extracellular Secretion
Authors: Langer Rebecca C. , Hayward Rhian E. , Tsuboi Takafumi , Tachibana Mayumi , Torii Motomi , Vinetz Joseph M.
Published: July 2002

Plasmodiumookinetes secrete chitinases to penetrate the acellular, chitin-containing peritrophic matrix of the mosquito midgut en route to invasion of the epithelium. Chitinases are potentially targets that can be used to block malaria transmission. We demonstrate here that chitinases ofPlasmodium falciparumandP. gallinaceumare concentrated at the apical end of ookinetes. The chitinase PgCHT1 ofP. gallinaceumis present within ookinete micronemes and subsequently becomes localized in the electron-dense area of the apical complex. These observations suggest a pathway by which ookinetes secrete proteins extracellularly.
Inhibition of
Chlamydia pneumoniae
Replication in Human Aortic Smooth Muscle Cells by Gamma Interferon-Induced Indoleamine 2,3-Dioxygenase Activity
Authors: Pantoja Laura G. , Miller Richard D. , Ramirez Julio A. , Molestina Robert E. , Summersgill James T.
Published: July 2002

Infection with
Chlamydia pneumoniae
, a human respiratory pathogen, has been implicated as a potential risk factor in atherosclerosis, possibly because the pathogen can exist in a persistent form similar to that described for
Chlamydia trachomatis
. The present study investigated whether gamma interferon (IFN-γ) can induce indoleamine 2,3-dioxygenase (IDO) activity in aortic smooth muscle cells, leading to a marked inhibition of
C. pneumoniae
growth. Our data indicate a stimulation of IDO mRNA expression and dose-dependent enzymatic activity following IFN-γ treatment. IDO-mediated increase in tryptophan catabolism resulted in a dose-dependent marked inhibition of
C. pneumoniae
replication.
The Sequence-Variable, Single-Copy
tprK
Gene of
Treponema pallidum
Nichols Strain UNC and Street Strain 14 Encodes Heterogeneous TprK Proteins
Authors: Stamm Lola V. , Bergen Heather L.
Published: July 2002

Syphilis is a chronic infection with early relapses that are hypothesized to result from the emergence of phenotypic variants of
Treponema pallidum
. Recent studies demonstrated that TprK, a target of protective immunity, is heterogeneous in several
T. pallidum
strains, but not in Nichols strain Seattle (A. Centurion-Lara, C. Godornes, C. Castro, W. C. Van Voorhis, and S. A. Lukehart, Infect. Immun. 68:824–831, 2000). Analysis of PCR-amplified
tprK
from Nichols strain UNC and Street strain 14 treponemes showed that TprK has seven regions of intrastrain heterogeneity resulting from amino acid substitutions, insertions, and deletions. In contrast, analysis of PCR-amplified
tprJ
showed little intrastrain or interstrain heterogeneity. Reverse transcriptase PCR analysis demonstrated that mRNA transcripts representing unique polymorphic TprK proteins are present during syphilitic infection. Southern hybridization confirmed that Nichols strain UNC and Street strain 14 each contain a single copy of
tprK
, indicating that intrastrain heterogeneity is due to the presence of multiple treponemal subpopulations which contain a variant form of
tprK
.
Multiple Mechanisms of Phase Variation of PorA in
Neisseria meningitidis
Authors: van der Ende Arie , Hopman Carla T. P. , Dankert Jacob
Published: July 2002

Previously, we reported that PorA expression in
Neisseria meningitidis
is modulated by variation in the length of the homopolymeric tract of guanidine residues between the −35 and −10 regions of the promoter or by deletion of
porA
. To reveal additional mechanisms of variation in PorA expression, the meningococcal isolates from 41 patients and 19 carriers were studied. In addition, at least 3 meningococcal isolates from different body parts of each of 11 patients were analyzed. Sequence analysis of the
porA
promoter showed that the spacer between the −35 and −10 regions varies in length between 14 and 24 bp. PorA expression was observed in strains with a
porA
promoter spacer of 16 to 24 bp. All but one strain with a
porA
promoter spacer of 16 to 20 bp and undetectable PorA expression have a homopolymeric tract of 8 or 6 instead of 7 adenine residues in the
porA
coding region. The other PorA-negative strain had a single-base-pair deletion in the coding region. The highest level of PorA expression was observed in strains with a promoter spacer of 17 or 18 bp. PorA expression was reduced twofold in strains with a
porA
promoter spacer of 16 or 19 bp. Strains with a 16-bp promoter spacer with substitutions in the polyguanidine tract displayed increased levels of PorA expression compared to strains with a homopolymeric tract of guanidine residues in the
porA
promoter. In conclusion, meningococci display multiple mechanisms for varying PorA expression.
Characterization of Allelic Variation in the
Babesia bovis
Merozoite Surface Antigen 1 (MSA-1) Locus and Identification of a Cross-Reactive Inhibition-Sensitive MSA-1 Epitope
Authors: Suarez Carlos E. , Florin-Christensen Monica , Hines Stephen A. , Palmer Guy H. , Brown Wendy C. , McElwain Terry F.
Published: July 2002

The
Babesia bovis
merozoite surface antigen 1 (MSA-1), a member of the variable merozoite surface antigen (VMSA) family, is an immunodominant glycoprotein which elicits antibodies that inhibit erythrocyte invasion. While antigenic polymorphism is a general feature of
vmsa
genes, the molecular basis and extent of
msa-1
sequence polymorphism have not been well characterized. In this study we defined the
msa-1
locus in the biologically cloned Mexico Mo7 strain of
B. bovis
and identified the sequence differences between MSA-1 antigenically dissimilar strains. We then determined whether sequences conserved between distinct
msa-1
alleles would induce cross-reactive CD4
+
T lymphocytes or inhibitory antibodies. The
msa-1
locus in Mo7 contains a single
msa-1
gene flanked by transcribed genes with no sequence homology to members of the VMSA gene family. Argentina
B. bovis
strains R1A and S2P have
msa-1
genes with amino acid sequences that are 98.8% identical to each other, and antibodies against S2P MSA-1 cross-react with native R1A MSA-1. In contrast, identity between the Argentina and Mexico Mo7
msa-1
alleles is only 52%, with no continuous stretch of identity longer than 16 amino acids. Despite limited sequence conservation, antibodies against R1A MSA-1 were able to inhibit invasion of erythrocytes by Mo7 merozoites. The results indicate that inhibition-sensitive epitopes are conserved despite significant sequence divergence between Mexico and Argentina strain alleles and support a conserved functional role for polymorphic MSA-1 in erythrocyte invasion.
Identification of Genes Present Specifically in a Virulent Strain of
Klebsiella pneumoniae
Authors: Lai Yi-Chyi , Yang Shu-Li , Peng Hwei-Ling , Chang Hwan-You
Published: July 2002

Klebsiella pneumoniae
is a common cause of septicemia and urinary tract infections. The PCR-supported genomic subtractive hybridization was employed to identify genes specifically present in a virulent strain of
K. pneumoniae
. Analysis of 25 subtracted DNA clones has revealed 19 distinct nucleotide sequences. Two of the sequences were found to be the genes encoding the transposase of Tn
3926
and a capsule polysaccharide exporting enzyme. Three sequences displayed moderate homology with
bvgAS
, which encodes a two-component signal transduction system in
Bordetella pertussis
. The rest of the sequences did not exhibit homology with any known genes. The distribution of these novel sequences varied greatly in
K. pneumoniae
clinical isolates, reflecting the heterogeneous nature of the
K. pneumoniae
population.
Identification of Immunodominant Antigens from
Helicobacter pylori
and Evaluation of Their Reactivities with Sera from Patients with Different Gastroduodenal Pathologies
Authors: Kimmel Brigitte , Bosserhoff Armin , Frank Rainer , Gross Roy , Goebel Werner , Beier Dagmar
Published: July 2002

Colonization of the gastric mucosa by
Helicobacter pylori
is the major cause of gastroduodenal pathologies in humans. Studying the outcome of the humoral immune response directed against this gastric pathogen may contribute substantially to vaccine development and to the improvement of diagnostic techniques based on serology. By using two-dimensional gel electrophoresis, 29 proteins from
H. pylori
G27 were identified which strongly react with sera derived from
H. pylori
-infected patients suffering from different gastroduodenal pathologies. These antigens were characterized by mass spectrometry and proved to correspond to products of open reading frames predicted by the
H. pylori
genome sequence. The comparison of the antigenic patterns recognized by these sera revealed no association of specific
H. pylori
antigens with antibodies in patients with particular gastroduodenal pathologies.
Phagocytosed
Bordetella pertussis
Fails To Survive in Human Neutrophils
Authors: Lenz Derrick H. , Weingart Christine L. , Weiss Alison A.
Published: July 2002

Previous studies have reported that phagocytosed
Bordetella pertussis
survives in human neutrophils. This issue has been reexamined. Opsonized or unopsonized bacteria expressing green fluorescent protein (GFP) were incubated with adherent human neutrophils. Phagocytosis was quantified by fluorescence microscopy, and the viability of phagocytosed bacteria was determined by colony counts following treatment with polymyxin B to kill extracellular bacteria. Only 1 to 2% of the phagocytosed bacteria remained viable. Opsonization with heat-inactivated immune serum reduced the amount of attachment and phagocytosis of the bacteria but did not alter survival rates. In contrast to previous reports, these data suggest that phagocytosed
B. pertussis
bacteria are killed by human neutrophils.
Intranasal Immunization withToxoplasma gondiiSAG1 Induces Protective Cells into Both NALT and GALT Compartments
Authors: Velge-Roussel F. , Marcelo P. , Lepage A. C. , Buzoni-Gatel D. , Bout D. T.
Published: July 2002

Intranasal (i.n.) immunization with the SAG1 protein ofToxoplasma gondiiplus cholera toxin (CT) provides protective immunity. The aim of this study was to analyze the cellular activation of several mucosal compartments after i.n. immunization. Cervical and mesenteric lymph node (CLN and MLN, respectively) lymphoid cell and intraepithelial lymphocyte (IEL) passive transfer experiments were performed with CBA/J mice immunized i.n. with SAG1 plus CT. CLN and MLN cells and IEL isolated 42 days after immunization conferred protective immunity on naive recipient mice challenged with strain 76KT. gondii, as assessed by the reduction in the number of brain cysts. There were proliferative specific responses in nose-associated lymphoid tissue and the CLN and MLN cells from mice immunized with SAG1 plus CT, but no cytokine was detectable. Thus, protective immunity is associated with a specific cellular response in the nasal and mesenteric compartments after i.n. immunization.
Comparison of the Roles of Calcineurin in Physiology and Virulence in Serotype D and Serotype A Strains of
Cryptococcus neoformans
Authors: Cruz M. Cristina , Sia Rey A. L. , Olson Michael , Cox Gary M. , Heitman Joseph
Published: July 2002

The calcineurin gene was cloned and disrupted in serotype D strains of
Cryptococcus neoformans
. Serotype A and serotype D calcineurin mutants were inviable at 37°C and avirulent in mice, whereas only serotype A mutants were cation stress sensitive. Thus, calcineurin plays conserved and divergent roles in serotype A and serotype D strains.
Actinobacillus pleuropneumoniaeIron Transport: a Set ofexbBDGenes Is Transcriptionally Linked to thetbpBGene and Required for Utilization of Transferrin-Bound Iron
Authors: Tonpitak Walaiporn , Thiede Svenja , Oswald Winfried , Baltes Nina , Gerlach Gerald-F.
Published: July 2002

Upon iron restriction,Actinobacillus pleuropneumoniaehas been shown to express the transferrin-binding proteins TbpB and TbpA, both of which have been implied to be important virulence factors. In order to identify additional iron-regulated proteins, we cloned and analyzed the region upstream of the transferrin-binding protein genes in anA. pleuropneumoniaeserotype 7 strain. We located immediately upstream of thetbpBgene two open reading frames which were 43% homologous to the neisserial ExbBD protein genes. By raising specific antibodies, we showed that ExbB is expressed under iron-limiting growth conditions only, and RT-PCR analysis revealed that theexbBDgenes and thetbpBgene are transcribed on a single polycistronic mRNA. By constructing an isogenic and nonpolarexbBDmutant, we showed that theexbBDgenes are required byA. pleuropneumoniaefor utilization of transferrin-bound iron. Using PCR and Western blotting, we showed that the genetic organization found inA. pleuropneumoniaeserotype 7 is similar in all 12A. pleuropneumoniaeserotype reference strains.
Influence of theBcgLocus on Natural Resistance to Primary Infection with the Facultative Intracellular BacteriumFrancisella tularensisin Mice
Authors: Kovářová Hana , Hernychová Lenka , Hajdúch Marián , Šírová M. , Macela Aleš
Published: July 2002

The implication of theBcglocus in the control of natural resistance to infection with a live vaccine strain (LVS) of the intracellular pathogenFrancisella tularensiswas studied. Analysis of phenotypic expression of natural resistance and susceptibility was performed using mouse strains congenic at theBcglocus. Comparison of the kinetics of bacterial colonization of spleen showed that B10.A.Bcg(r)mice were extremely susceptible during early phases of primary sublethal infection, while their congenic C57BL/10N [Bcg(s)] counterparts could be classified as resistant toF. tularensisLVS infection according to the 2-log-lower bacterial CFU within the tissue as long as 5 days after infection. Different phenotypes ofBcgcongenic mice were associated with differential expression of the cytokines tumor necrosis factor alpha, interleukin-10, and gamma interferon and production of reactive oxygen intermediates. These results strongly suggest that theBcglocus, which is close or identical to theNramp1gene, controls natural resistance to infection byF. tularensisand that its effect is the opposite of that observed for otherBcg-controlled pathogens.
Lipopolysaccharides ofBrucella abortusandBrucella melitensisInduce Nitric Oxide Synthesis in Rat Peritoneal Macrophages
Authors: López-Urrutia Luis , Alonso Andrés , Nieto Maria Luisa , Bayón Yolanda , Orduña Antonio , Sánchez Crespo Mariano
Published: July 2002

Smooth lipopolysaccharide (S-LPS) and lipid A ofBrucella abortusandBrucella melitensisinduced the production of nitric oxide (NO) by rat adherent peritoneal cells, but they induced lower levels of production of NO thanEscherichia coliLPS. The participation of the inducible isoform of NO synthase (iNOS) was confirmed by the finding of an increased expression of both iNOS mRNA and iNOS protein. These observations might help to explain (i) the acute outcome ofBrucellainfection in rodents, (ii) the low frequency of septic shock in human brucellosis, and (iii) the prolonged intracellular survival ofBrucellain humans.
Comparison of the Immune Profile of Nonhealing Cutaneous Leishmaniasis Patients with Those with Active Lesions and Those Who Have Recovered from Infection
Authors: Ajdary Soheila , Alimohammadian Mohammad H. , Eslami Mohammad B. , Kemp Kaare , Kharazmi Arsalan
Published: July 2002

Th1-type cellular immune responses play a critical role in protection against infection withLeishmaniaparasites, whereas activation of Th2-type cells results in progressive disease. Cutaneous leishmaniasis caused byLeishmania majoris often a self-healing disease; however, persistent nonhealing forms are also known. In the present study, we have described cell-mediated immune responses in nonhealing patients by measuring T-cell proliferation, cytokine production, and phenotypic characterization of these cells. The responses were compared with those of patients with active lesions, patients who had recovered from infection, and healthy controls. Peripheral blood mononuclear cells from patients with active lesions and recovered donors proliferated vigorously and produced Th1-type cytokine when stimulated withL. majorantigens, whereas in nonhealing patients the proliferative responses were significantly lower and showed a Th2-type response toLeishmaniaantigens. Interleukin-10 (IL-10) production was not a feature ofL. majorstimulation. Flow cytometric analysis revealed thatL. majorantigen induced proliferation of the CD4-positive population and that these cells were the major source of gamma interferon and IL-4. These results show a distinct dichotomy in the cytokine response toL. majorinfection.
Immunogenicity and Efficacy inAotusMonkeys of Four RecombinantPlasmodium falciparumVaccines in Multiple Adjuvant Formulations Based on the 19-Kilodalton C Terminus of Merozoite Surface Protein 1
Authors: Kumar Sanjai , Collins William , Egan Andrea , Yadava Anjali , Garraud Olivier , Blackman Michael J. , Patino Jose A. Guevara , Diggs Carter , Kaslow David C.
Published: July 2002

The immunogenicity and protective efficacy of four versions of recombinant C-terminal 19-kDa epidermal growth factor-like region of the major surface protein 1 (rMSP119) ofPlasmodium falciparumwas studied inAotusmonkeys. Vaccination with each of the four rMSP119constructs elicited high levels of antibodies to MSP119but only one construct, the 19-kDa fragment expressed as a secreted fusion protein fromSaccharomyces cerevisiae(yP30P2MSP119), induced a high degree of protective immunity inAotus nancymaiagainst lethalP. falciparumchallenge. Protective formulation required Freund's adjuvant; vaccination with yP30P2MSP119in six other adjuvants that are suitable for human use induced lower levels of antibody response and no protection. These results emphasize the need to continue the search for an adjuvant that is comparable to Freund's adjuvant in potency and is safe for use in humans.
Interaction of HLA and Age on Levels of Antibody toPlasmodium falciparumRhoptry-Associated Proteins 1 and 2
Authors: Johnson Armead , Leke Rose , Harun Lucy , Ginsberg Christina , Ngogang Jeanne , Stowers Anthony , Saul Allan , Quakyi Isabella A.
Published: July 2002

ThePlasmodium falciparumrhoptry-associated proteins 1 and 2 (RAP1 and RAP2) are candidate antigens for a subunit malaria vaccine. The design of the study, which looks at the acquisition of immunity to malaria from childhood to old age, has allowed us to document the interaction of HLA and age on levels of antibody to specific malarial antigens. Antibodies reach maximum levels to RAP1 after the age of 15 but to RAP2 only after the age of 30. The effect of HLA-DRB1 and -DQB1 and age on levels of antibody to rRAP1 and rRAP2 was analyzed with a multiple regression model in which all HLA alleles and age were independent variables. DQB1*0301 and -*03032 showed an age-dependent association with levels of antibody to rRAP1, being significant in children 5 to 15 years (P< 0.001) but not in individuals over 15 years of age. DRB1*03011 showed an age-dependent association with antibody levels to rRAP2; however, this association was in adults over the age of 30 years (P< 0.01) but not in individuals under the age of 30 years. No associations were detected between DRB1 alleles and RAP1 antibody levels or between DQB1 alleles and RAP2 antibody levels. Thus, not only the HLA allele but also the age at which an interaction is manifested varies for different malarial antigens. The interaction may influence either the rate of acquisition of antibody or the final level of antibody acquired by adults.
Adhesion of
Aspergillus
Species to Extracellular Matrix Proteins: Evidence for Involvement of Negatively Charged Carbohydrates on the Conidial Surface
Authors: Wasylnka Julie A. , Moore Margo M.
Published: July 2002

Invasive lung disease caused by
Aspergillus
species is a potentially fatal infection in immunocompromised patients. The adhesion of
Aspergillus fumigatus
conidia to proteins in the basal lamina is thought to be an initial step in the development of invasive aspergillosis. The purpose of this study was to determine the mechanism of adhesion of
A. fumigatus
conidiospores to basal-lamina proteins and to determine whether conidia possess unique adhesins which allow them to colonize the host. We compared conidia from different
Aspergillus
species for the ability to bind to purified fibronectin and intact basal lamina. Adhesion assays using immobilized fibronectin or type II pneumocyte-derived basal lamina showed that
A. fumigatus
conidia bound significantly better than those of other
Aspergillus
species to both fibronectin and intact basal lamina. Neither desialylation nor complete deglycosylation of fibronectin decreased the binding of
A. fumigatus
conidia to fibronectin, suggesting that oligosaccharides on fibronectin were not involved in conidiospore binding. Further evidence for this hypothesis came from experiments using purified fragments of fibronectin;
A. fumigatus
conidia preferentially bound to the nonglycosylated 40-kDa fragment which contains the glycosaminoglycan (GAG) binding domain. Negatively charged carbohydrates, including dextran sulfate and heparin, as well as high-ionic-strength buffers, inhibited binding of
A. fumigatus
conidia to both fibronectin and intact basal lamina, suggesting that negatively charged carbohydrates on the surface of the conidium may bind to the GAG binding domain of fibronectin and other basal-lamina proteins. These data provide evidence for a novel mechanism of conidial attachment whereby adherence to fibronectin and other basal-lamina proteins is mediated via negatively charged carbohydrates on the conidial surface.
Bacterial Cell Wall-Induced Arthritis: Chemical Composition and Tissue Distribution of FourLactobacillusStrains
Authors: Šimelyte Egle , Rimpiläinen Marja , Lehtonen Leena , Zhang Xiang , Toivanen Paavo
Published: July 2002

To study what determines the arthritogenicity of bacterial cell walls, cell wall-induced arthritis in the rat was applied, using four strains ofLactobacillus. Three of the strains used proved to induce chronic arthritis in the rat; all wereLactobacillus casei. The cell wall ofLactobacillus fermentumdid not induce chronic arthritis. All arthritogenic bacterial cell walls had the same peptidoglycan structure, whereas that ofL. fermentumwas different. Likewise, all arthritogenic cell walls were resistant to lysozyme degradation, whereas theL. fermentumcell wall was lysozyme sensitive. Muramic acid was observed in the liver, spleen, and lymph nodes in considerably larger amounts after injection of an arthritogenicL. caseicell wall than following injection of a nonarthritogenicL. fermentumcell wall. TheL. caseicell wall also persisted in the tissues longer than theL. fermentumcell wall. The present results, taken together with those published previously, underline the possibility that the chemical structure of peptidoglycan is important in determining the arthritogenicity of the bacterial cell wall.
Role of Phosphoglucomutase of
Bordetella bronchiseptica
in Lipopolysaccharide Biosynthesis and Virulence
Authors: West Nicholas P. , Jungnitz Heidrun , Fitter John T. , McArthur Jason D. , Guzmán Carlos A. , Walker Mark J.
Published: July 2002

The phosphoglucomutase (PGM)-encoding gene of
Bordetella bronchiseptica
is required for lipopolysaccharide (LPS) biosynthesis. An insertion mutant of the wild-type
B. bronchiseptica
strain BB7865 which disrupted LPS biosynthesis was created and characterized (BB7865
pgm
). Genetic analysis of the mutated gene showed it shares high identity with PGM genes of various bacterial species and forms part of an operon which also encompasses the gene encoding phosphoglucose isomerase. Functional assays for PGM revealed that enzyme activity is expressed in both
bvg
-positive and
bvg
-negative strains of
B. bronchiseptica
and is substantially reduced in BB7865
pgm
. Complementation of the mutated PGM gene with that from BB7865 restored the wild-type condition for all phenotypes tested. The ability of the mutant BB7865
pgm
to survive within J774.A1 cells was significantly reduced at 2 h (40% reduction) and 24 h (56% reduction) postinfection. BB7865
pgm
was also significantly attenuated in its ability to survive in vivo following intranasal infection of mice, being effectively cleared from the lungs within 4 days, whereas the wild-type strain persisted at least 35 days. The activities of superoxide dismutase, urease, and acid phosphatase were unaffected in the PGM-deficient strain. In contrast, the inability to produce wild-type LPS resulted in a reduced bacterial resistance to oxidative stress and a higher susceptibility to the antimicrobial peptide cecropin P.
Failure To Detect Muramic Acid in Normal Rat Tissues but Detection in Cerebrospinal Fluids from Patients with Pneumococcal Meningitis
Authors: Kozar Michael P. , Krahmer Mark T. , Fox Alvin , Gray Barry M.
Published: July 2002

Muramic acid serves as a marker for the presence of bacterial cell wall debris in mammalian tissues. There have been a number of controversial and sometimes conflicting results on assessing the levels of muramic acid in health and disease. The present report is the first to use the state-of-the art technique, gas chromatography-tandem mass spectrometry, to identify and quantify the levels of muramic acid in tissues. Muramic acid was not found in normal rat brain or spleen. However, when tissues were spiked with muramic acid, it was readily identified. The detection limit was <1 ng of muramic acid/100 mg (wet weight) of tissue. The levels of muramic acid reported in diseased human spleen and spleen of arthritic rats, previously injected with bacterial cell walls, were 100- to 1,000-fold higher. In the present study, muramic acid was also readily detected in the cerebrospinal fluid of patients with pneumococcal meningitis (6.8 to 3,900 ng of muramic acid/ml of cerebrospinal fluid). In summary, there can be an enormous difference in the levels of muramic acid found in different mammalian tissues and body fluids in health and disease. This report could have great impact in future studies assessing the role of bacterial cell wall remnants in the pathogenesis of certain human inflammatory diseases.
Decorin-Binding Protein A (DbpA) of
Borrelia burgdorferi
Is Not Protective When Immunized Mice Are Challenged via Tick Infestation and Correlates with the Lack of DbpA Expression by
B. burgdorferi
in Ticks
Authors: Hagman Kayla E. , Yang Xiaofeng , Wikel Stephen K. , Schoeler George B. , Caimano Melissa J. , Radolf Justin D. , Norgard Michael V.
Published: July 2002

Previous studies showed that decorin-binding protein A (DbpA) of
Borrelia burgdorferi
was a protective immunogen in the murine model of Lyme borreliosis when mice were challenged (needle inoculated) intradermally with in vitro-cultivated spirochetes. In the present study, DbpA-immunized C3H/HeJ mice were not protected from infection when infested with
Ixodes scapularis
nymphs harboring virulent
B. burgdorferi
297. This lack of protection correlated with the failure to detect DbpA on
B. burgdorferi
in ticks, suggesting that DbpA is not available as a target for bactericidal antibodies in serum when
B. burgdorferi
-infected ticks take their blood meal from an immunized host. The failure of DbpA immunization to protect tick-challenged mice contradicts the results of earlier needle inoculation vaccination experiments and suggests that DbpA may not be suitable as a Lyme disease vaccine.
Protective Immunity against Congenital Toxoplasmosis with Recombinant SAG1 Protein in a Guinea Pig Model
Authors: Haumont Michèle , Delhaye Louis , Garcia Lida , Jurado Margarita , Mazzu Pasqualina , Daminet Véronique , Verlant Vincent , Bollen Alex , Biemans Ralph , Jacquet Alain
Published: July 2002

Primary infection withToxoplasma gondiiduring pregnancy can induce fetal pathology and abortion in both humans and animals. The present study describes the development of an experimental model of congenital toxoplasmosis in the guinea pig. In this animal model, we evaluated the protective effect of vaccination with a recombinant form of SAG1 against maternofetal transmission of tachyzoites. The presence of parasites in fetuses was determined by nested PCRs and by an in vivo readout after fetal brain homogenate injections in mice. The absence of parasites was demonstrated in 66 to 86% of fetuses derived from adult guinea pigs immunized with SAG1 and challenged with the mildly virulentT. gondiistrain C56. In contrast, more than 80% of fetuses from mock-immunized guinea pigs were infected. The protection was not correlated with titers of antibody to SAG1. Our results indicated that this experimental model constitutes a relevant model for evaluation of vaccine candidates against congenital toxoplasmosis and that SAG1 elicits significant protection against maternofetal transmission.
Toxoids of Streptococcal Pyrogenic Exotoxin A Are Protective in Rabbit Models of Streptococcal Toxic Shock Syndrome
Authors: Roggiani Manuela , Stoehr Jennifer A. , Olmsted Stephen B. , Matsuka Yury V. , Pillai Subramonia , Ohlendorf Douglas H. , Schlievert Patrick M.
Published: July 2002

Streptococcal pyrogenic exotoxins (SPEs) are superantigens that have been implicated in causing streptococcal toxic shock syndrome (STSS). Most notably, SPE serotype A is made by nearly all M-protein serotype 1 and 3 streptococci, the M types most associated with the illness (these strains contain one or more other SPEs, and those proteins are likely also to contribute to disease). We have prepared double-, triple-, and hexa-amino-acid mutants of SPE A by PCR and other mutagenesis procedures. The sites chosen for mutation were solvent-exposed residues thought to be important for T-cell receptor (TCR) or major histocompatibility complex (MHC) class II interaction. These mutants were nonsuperantigenic for human peripheral blood mononuclear cells and rabbit and mouse splenocytes and were nonlethal in two rabbit models of STSS. In addition, these mutants stimulated protective antibody responses. Interestingly, mutants that altered toxin binding to MHC class II were more immunogenic than mutants altering TCR binding. Collectively, these studies indicate that multiple-site mutants of SPE A are toxoids that may have use in protecting against the toxin's effects in STSS.
Silencing and Reactivation of Urease in
Yersinia pestis
Is Determined by One G Residue at a Specific Position in the
ureD
Gene
Authors: Sebbane Florent , Devalckenaere Annie , Foulon Jeannine , Carniel Elisabeth , Simonet Michel
Published: July 2002

Yersinia pestis
, the plague agent, is a naturally nonureolytic microorganism, while all other
Yersinia
species display a potent urease activity. In this report we demonstrate that
Y. pestis
harbors a complete urease locus composed of three structural (
ureABC
) and four accessory (
ureEFGD
) genes. Absence of ureolytic activity is due to the presence of one additional G residue in a poly(G) stretch, which introduces a premature stop codon in
ureD
. The presence of the same additional G in eight other
Y. pestis
isolates indicates that this mutation is species specific. Spontaneous excision of the extra G occurs at a frequency of 10
−4
to 10
−5
and restores a ureolytic phenotype to
Y. pestis
. The virulence of two independent ureolytic clones of
Y. pestis
injected either intravenously, subcutaneously, or intragastrically did not differ from that of the parental strain in the mouse infection model. Coinfection experiments with an equal number of ureolytic and nonureolytic bacteria did not evidence any difference in the ability of the two variants to multiply in vivo and to cause a lethal infection. Altogether our results demonstrate that variation of one extra G residue in
ureD
determines the ureolytic activity of
Y. pestis
but does not affect its virulence for mice or its ability to multiply and disseminate.
Dual Role of theLeishmania majorRibosomal Protein S3a Homologue in Regulation of T- and B-Cell Activation
Authors: Cordeiro-da-Silva Anabela , Borges Margarida Coutinho , Guilvard Eliane , Ouaissi Ali
Published: July 2002

We have recently characterized a novelLeishmania majorgene encoding a polypeptide of 30 kDa that was homologous to mammalian ribosomal protein S3a and was named LmS3a-related protein (LmS3arp). The protein was found to be expressed by all theLeishmaniaspecies so far examined (L. infantum, L. amazonensis, andL. mexicana). In the present study we have extended our approach to the analysis of LmS3arp activity on T- and B-cell functions in a murine model. The results presented in this report show that LmS3arp plays a dual role in the regulation of T- and B-cell reactivity. Indeed, we found that injection of the LmS3arp recombinant protein (rLmS3arp) into BALB/c mice induces preferential activation of B cells, as shown by the following criteria: (i) increased expression of CD69 molecules on immunoglobulin M (IgM)-secreting spleen cells, (ii) a considerable increase of IgM-secreting B cells, and (iii) elevated levels of IgM antibodies in the sera of injected animals. Moreover, the IgM antibodies are not specific to theLeishmaniaantigens but preferentially recognize heterologous antigens like myosin, thyroglobulin, DNA, and keyhole limpet hemocyanin. Furthermore, the strong polyclonal expansion of nonspecific, non-parasite-directed B-cell clones induced by rLmS3arp is concomitant with a marked inhibition of T-cell proliferation. Analysis of cytokine production revealed a significant downregulation of gamma interferon, interleukin-2 (IL-2), and IL-12 secretion. Taken together, our data suggest that rLmS3arp, through direct or indirect action toward B and T cells and cytokine secretion, could participate in the immunoregulatory processes that play a role in the balance of the Th1 and Th2 immune response.
agrExpression Precedes Escape of InternalizedStaphylococcus aureusfrom the Host Endosome
Authors: Qazi Saara N. A. , Counil Emilie , Morrissey Julie , Rees Catherine E. D. , Cockayne Alan , Winzer Klaus , Chan Weng C. , Williams Paul , Hill Philip J.
Published: July 2002

Staphylococcus aureusis a versatile pathogen capable of causing life-threatening infections. Many of its cell wall and exoproduct virulence determinants are controlled via the accessory gene regulator (agr). Although considered primarily as an extracellular pathogen, it is now recognized thatS. aureuscan be internalized by epithelial and endothelial cells. Traditional experimental approaches to investigate bacterial internalization are extremely time-consuming and notoriously irreproducible. We present here a new reporter gene method to assess intracellular growth ofS. aureusin MAC-T cells that utilizes agfp-luxABCDEreporter operon under the control of theBacillus megateriumxylApromoter, which inS. aureusis expressed in a growth-dependent manner. This facilitates assessment of the growth of internalized bacteria in a nondestructive assay. The dualgfp-luxreporter cassette was also evaluated as a reporter ofagrexpression and used to monitor the temporal induction ofagrduring the MAC-T internalization process. The data obtained suggest thatagrinduction occurs prior to endosomal lysis and thatagr-regulated exoproteins appear to be required prior to the release and replication ofS. aureuswithin the infected MAC-T cells.
Characterization of Antiapoptotic Activities ofChlamydia pneumoniaein Human Cells
Authors: Fischer Silke F. , Schwarz Claudia , Vier Juliane , Häcker Georg
Published: July 2002

Chlamydia pneumoniaeis an obligate intracellular bacterium which frequently causes airway infection in humans and has been implicated in atherosclerosis. Here we show that infection withC. pneumoniaeprotects HeLa human epithelioid cells against apoptosis induced by external stimuli. In infected HeLa cells, apoptosis induced by staurosporine and CD95-death-receptor signaling was strongly reduced. Upon treatment with staurosporine, generation of effector caspase activity, processing of caspase-3 and caspase-9 and cytochromecredistribution were all profoundly inhibited in cells infected withC. pneumoniae. Bacterial protein synthesis during early infection was required for this inhibition. Furthermore, cytochromec-induced processing and activation of caspases were inhibited in cytosolic extracts from infected cells, suggesting that aC. pneumoniae-dependent antiapoptotic factor was generated in the cytosol upon infection. Infection withC. pneumoniaefailed to induce significant NF-κB activation in HeLa cells, indicating that no NF-κB-dependent cellular factors were involved in the protection against apoptosis. These results show thatC. pneumoniaeis capable of interfering with the host cell's apoptotic apparatus at probably at least two steps in signal transduction and might explain the propensity of these bacteria to cause chronic infections in humans.
Cure ofHelicobacter pyloriInfection and Resolution of Gastritis by Adoptive Transfer of Splenocytes in Mice
Authors: Eaton Kathryn A. , Mefford Megan E.
Published: July 2002

Vaccination suppressesHelicobacter pyloricolonization but does not cure infection. Furthermore, postvaccination gastritis, likely induced by enhanced host response to residual colonization, may exacerbate disease. The goal of this study was to determine if adoptive transfer of C57BL/6 splenocytes to C57BL/6scid/scid(severe combined immunodeficient [SCID]) mice cures infection without exacerbating gastritis.H. pylori-infected and uninfected C57BL/6 mice and SCID recipients of normal splenocytes were killed at intervals between 5 and 51 weeks after infection. Colonization and gastritis were quantified, humoral immune responses were determined by enzyme-linked immunosorbent assay, and cellular immune responses were determined by delayed-type hypersensitivity response and by a proliferative response of cultured splenocytes toH. pylorisonicate. In infected C57BL/6 mice, gastritis developed gradually and bacterial colonization diminished but persisted throughout the experiment. In contrast, gastritis in infected recipient SCID mice developed rapidly and bacterial colonization decreased precipitously. Gastritis in those mice peaked 9 weeks after adoptive transfer, however, and began to resolve. By 45 weeks after transfer, gastritis had returned to background levels and bacteria were no longer detectable. Resolution of gastritis and elimination of infection were associated with a cellular but not humoral immune response toH. pyloriantigens. These results demonstrate that although the host response fails to clear bacterial colonization in normal mice, enhanced cellular immune responses in recipient SCID mice are capable of clearingH. pyloriinfection and allowing resolution of gastritis. Thus, immune mechanisms of cure exist, and effective and safe vaccination protocols may be feasible.
Macrophage-Derived Cell Lines Do Not Express Proinflammatory Cytokines after Exposure to
Bacillus anthracis
Lethal Toxin
Authors: Erwin James L. , DaSilva Luis M. , Bavari Sina , Little Stephen F. , Friedlander Arthur M. , Chanh Tran C.
Published: July 2002

We present evidence that
Bacillus anthracis
lethal toxin (LT) suppresses rather than induces proinflammatory cytokine production in macrophages. Suppression is observed with extremely low levels of LT and involves inhibition of transcription of cytokine messenger RNA. Thus, LT may contribute to anthrax pathogenesis by suppressing the inflammatory response.