bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamma Interferon Influences Intestinal Epithelial Hyperplasia Caused byLawsonia intracellularisInfection in Mice
Authors: Smith David G. E. , Mitchell Suzanne C. , Nash Tony , Rhind Susan 
Published: July 2002

ABSTRACTLawsonia intracellularisis a recently identified bacterial pathogen which causes disease in a broad range of animals. Invasion of intestinal epithelial cells and the resultant hyperplasia of infected cells are central processes in disease pathogenesis. In this study, we aimed to establish whether immunocompetent mice were susceptible to infection and whether gamma interferon (IFN-γ) contributed to the pathogenesis of infection. Wild-type 129-Sv-Ev mice (129 mice) and IFN-γ receptor knockout mice based on the 129 background (IFN-γR−) were challenged orally with approximately 5.5 × 107L. intracellulariscells. Both 129 and IFN-γR−mice became infected, although the extent of infection (as determined by the proportion of infected crypts) was substantially lower in 129 mice than in IFN-γR−mice. Despite these differences, infected crypts showed characteristics typical of proliferative enteropathies of other animals, i.e., intracellular colonization of epithelial cells byL. intracellulariswith resultant epithelial hyperplasia. Infection in 129 mice was cleared between days 21 and 28 postchallenge, whereas infection in IFN-γR−mice was evident in 100% of animals from day 21 onward. Additionally, in IFN-γR−mice the infection was so extensive that fatalities resulted. IFN-γ therefore plays a significant role in limiting intracellular infection and increased cellular proliferation associated withL. intracellularis. L. intracellularisinfection is generally associated with modest cellular infiltration; therefore, further comparative examinations will be necessary to determine pathogenicity factors and define the role of IFN-γ in controlling this infection.
Neutrophils Play a Protective Nonphagocytic Role in SystemicMycobacterium tuberculosisInfection of Mice
Authors: Pedrosa Jorge , Saunders Bernadette M. , Appelberg Rui , Orme Ian M. , Silva Manuel T. , Cooper Andrea M. 
Published: July 2002

ABSTRACTEvidence showing that neutrophils play a protective role in the host response to infection by different intracellular parasites has been published in the past few years. We assessed this issue with regard to the infection of mice withMycobacterium tuberculosis. We found a chronic recruitment of neutrophils to the infection foci, namely, to the peritoneal cavity after intraperitoneal infection and to the spleen and liver after intravenous inoculation of the mycobacteria. However, bacilli were never found associated with the recruited neutrophils but rather were found inside macrophages. The intravenous administration of the antineutrophil monoclonal antibody RB6-8C5 during the first week of infection led to selective and severe neutropenia associated with an enhancement of bacillary growth in the target organs of the mice infected by the intravenous route. The neutropenia-associated exacerbation of infection was most important in the liver, where a bacterial load 10-fold higher than that in nonneutropenic mice was found; the exacerbation in the liver occurred both during and after the neutropenic period. Early in infection byM. tuberculosis, neutropenic mice expressed lower levels of mRNAs for gamma interferon and inducible nitric oxide synthase in the liver compared to nondepleted mice. These results point to a protective role of neutrophils in the host defense mechanisms againstM. tuberculosis, which occurs early in the infection and is not associated with the phagocytic activity of neutrophils but may be of an immunomodulatory nature.
Immunogenicity and Tolerance of a 7-Valent Pneumococcal Conjugate Vaccine in Nonresponders to the 23-Valent Pneumococcal Vaccine
Authors: Zielen S. , Bühring I. , Strnad N. , Reichenbach J. , Hofmann D. 
Published: July 2002

ABSTRACT
There is still a lack of effective vaccination strategies for patients with a deficient antibody response to bacterial polysaccharide antigens. In an open trial, we evaluated the immunogenicity and tolerance of a new 7-valent pneumococcal conjugate vaccine in 22 infection-prone nonresponders to pneumococcal polysaccharide vaccine and 21 controls. In the patient group, nonresponsiveness was confirmed by repeated vaccination with a 23-valent pneumococcal polysaccharide vaccine. The study protocol provided two doses of the pneumococcal conjugate vaccine, given 4 to 6 weeks apart, for both groups. The antibody response was determined before each vaccination and on follow-up by an enzyme-linked immunosorbent assay and compared to the response in a functional opsonophagocytosis assay. Patients showed a significantly lower postvaccination immune response for all serotypes than did controls. The postvaccination response was serotype dependent. A median titer of >1 μg/ml in patients was recorded only for serotypes 4, 9V, 14, and 19F, which are known to be more immunogenic than serotypes 6B, 18C, and 23F. In the patient group, 70% responded to serotype 19F (Pnc 19F), 65% responded to Pnc 14 and 4, 60% responded to Pnc 9V, 55% responded to Pnc 18C, 50% responded to Pnc 23F, and 25% responded to Pnc 6B. In the control group >95% of individuals showed a titer of >1 μg/ml to every serotype. The vaccine was tolerated well, and no major side effects have been reported. The new pneumococcal conjugate vaccine is clearly more immunogenic in previous nonresponders than is the 23-valent pneumococcal vaccine. Immunization with a pneumococcal conjugate vaccine should be considered as a strategy to protect high-risk patients.
The Virulence Regulatory Protein ToxR Mediates Enhanced Bile Resistance in
Vibrio cholerae
and Other Pathogenic
Vibrio
Species
Authors: Provenzano Daniele , Schuhmacher Darren A. , Barker Justin L. , Klose Karl E. 
Published: July 2002

ABSTRACT

The transmembrane regulatory protein ToxR is required for expression of virulence factors in the human diarrheal pathogen
Vibrio cholerae
, including cholera toxin (CT) and the toxin coregulated pilus (TCP). ToxR is necessary for transcription of the gene encoding a second regulatory protein, ToxT, which is the direct transcriptional activator of CT and TCP genes. However, ToxR, independent of ToxT, directly activates and represses transcription of the outer membrane porins OmpU and OmpT, respectively. The genes encoding TCP and CT (and including ToxT) lie on horizontally acquired genetic elements, while the
toxR
,
ompU
, and
ompT
genes are apparently in the ancestral
Vibrio
chromosome. The contribution of ToxR-dependent modulation of outer membrane porins to cholera pathogenesis has remained unknown. We demonstrate that ToxR mediates enhanced bile resistance in a ToxT-independent manner. In both classical and El Tor biotypes of
V. cholerae
, a
toxR
mutant strain has a reduced minimum bactericidal concentration (MBC) of bile, the bile component deoxycholate (DC), and the anionic detergent sodium dodecyl sulfate (SDS) compared to both wild-type and
toxT
mutant strains. Classical and El Tor
toxR
mutant strains also exhibit reduced growth rates at subinhibitory concentrations of DC and SDS. Growth of either
V. cholerae
biotype in subinhibitory concentrations of bile or DC induces increased ToxR-dependent production of a major 38-kDa outer membrane protein, which was confirmed to be OmpU by Western blot. Measurement of transcription of a
ompU
p-
lacZ
fusion in both biotypes reveals stimulation (about two- to threefold) of ToxR-dependent
ompU
transcription by the presence of bile or DC, suggesting that ToxR may respond to the presence of bile. The
toxR
mutant strains of three additional human intestinal pathogenic
Vibrio
species,
V. mimicus
,
V. fluvialis
, and
V. parahaemolyticus
, display lower MBCs of bile, DC, and SDS and have altered outer membrane protein profiles compared to the parental wild-type strains. Our results demonstrate a conserved role for ToxR in the modulation of outer membrane proteins and bile resistance of pathogenic
Vibrio
species and suggest that these ToxR-dependent outer membrane proteins may mediate enhanced resistance to bile. We speculate that ToxR-mediated bile resistance was an early step in the evolution of
V. cholerae
as an intestinal pathogen.
Phase 1 and Phase 2 Studies ofSalmonella entericaSerovar Paratyphi A O-Specific Polysaccharide-Tetanus Toxoid Conjugates in Adults, Teenagers, and 2- to 4-Year-Old Children in Vietnam
Authors: Konadu Edward Y. , Lin Feng-Ying C. , Hó Vô Anh , Thuy Nguyen Thi Thanh , Van Bay Phan , Thanh Tran Cong , Khiem Ha Ba , Trach Dang Duc , Karpas Arthur B. , Li Jianping , Bryla Dolores A. , Robbins John B. , Szu Shousun C. 
Published: July 2002

ABSTRACTSalmonella entericaserovar Paratyphi A O-specific polysaccharide (O-SP) was activated with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate (CDAP) and bound to tetanus toxoid (TT) with adipic acid dihydrazide as a linker (SPA-TT1) or directly (SPA-TT2). In mice, these two conjugates elicited high levels of immunoglobulin G (IgG) anti-lipopolysaccharide (LPS) in serum with bactericidal activity (E. Konadu, J. Shiloach, D. A. Bryla, J. B. Robbins, and S. C. Szu, Infect. Immun. 64:2709–2715, 1996). The safety and immunogenicity of the two conjugates were then evaluated sequentially in Vietnamese adults, teenagers, and 2- to 4-year-old children. None of the vaccinees experienced significant side effects, and all had preexisting LPS antibodies. At 4 weeks after injection, there were significant increases of the geometric mean IgG and IgM anti-LPS levels in the adults and teenagers: both conjugates elicited a greater than fourfold rise in the IgG anti-LPS level in serum in ≥80% of the volunteers. SPA-TT2elicited slightly higher, though not statistically significantly, levels of IgG anti-LPS than did SPA-TT1in these age groups. Accordingly, only SPA-TT2was evaluated in the 2- to 4-year-old children. On a random basis, one or two injections were administered 6 weeks apart to the children. No significant side effects were observed, and the levels of preexisting anti-LPS in serum were similar in children of all ages. A significant rise in the IgG anti-LPS titer was elicited by the first injection (P= 0.0001); a second injection did not elicit a booster response. Representative sera from all groups had bactericidal activity that could be adsorbed byS. entericaserovar Paratyphi A LPS.
The Leptospiral Major Outer Membrane Protein LipL32 Is a Lipoprotein Expressed during Mammalian Infection
Authors: Haake David A. , Chao Garlo , Zuerner Richard L. , Barnett Jeanne K. , Barnett Dean , Mazel Mary , Matsunaga James , Levett Paul N. , Bolin Carole A. 
Published: July 2002

ABSTRACTWe report the cloning of the gene encoding the 32-kDa lipoprotein, designated LipL32, the most prominent protein in the leptospiral protein profile. We obtained the N-terminal amino acid sequence of a staphylococcal V8 proteolytic-digest fragment to design an oligonucleotide probe. A Lambda-Zap II library containingEcoRI fragments ofLeptospira kirschneriDNA was screened, and a 5.0-kb DNA fragment which contained the entire structurallipL32gene was identified. Several lines of evidence indicate that LipL32 is lipid modified in a manner similar to that of other procaryotic lipoproteins. The deduced amino acid sequence of LipL32 would encode a 272-amino-acid polypeptide with a 19-amino-acid signal peptide, followed by a lipoprotein signal peptidase cleavage site. LipL32 is intrinsically labeled during incubation ofL. kirschneriin media containing [3H]palmitate. The linkage of palmitate and the amino-terminal cysteine of LipL32 is acid labile. LipL32 is completely solubilized by Triton X-114 extraction ofL. kirschneri; phase separation results in partitioning of LipL32 exclusively into the hydrophobic, detergent phase, indicating that it is a component of the leptospiral outer membrane. CaCl2(20 mM) must be present during phase separation for recovery of LipL32. LipL32 is expressed not only during cultivation but also during mammalian infection. Immunohistochemistry demonstrated intense LipL32 reactivity withL. kirschneriinfecting proximal tubules of hamster kidneys. LipL32 is also a prominent immunogen during human leptospirosis. The sequence and expression of LipL32 is highly conserved among pathogenicLeptospiraspecies. These findings indicate that LipL32 may be important in the pathogenesis, diagnosis, and prevention of leptospirosis.
RecombinantStaphylococcus aureusExfoliative Toxins Are Not Bacterial Superantigens
Authors: Plano Lisa R. W. , Gutman Delia M. , Woischnik Markus , Collins Carleen M. 
Published: July 2002

ABSTRACTStaphylococcal scalded-skin syndrome is an exfoliative dermatitis characterized by the separation of the epidermis at the stratum granulosum. This disruption is mediated by one of twoStaphylococcus aureusexotoxins, exfoliative toxins A and B (ETA and ETB). Both ETA and ETB have been reported to be bacterial superantigens. A controversy exists, however, as other data indicate that these exotoxins are not superantigens. Here we demonstrate that recombinant exfoliative toxins produced inEscherichia colido not act as T-cell mitogens and thus are not bacterial superantigens. These data fit the clinical profile of the disease, which is not associated with the classic symptoms of a superantigen-mediated syndrome.
Brucella abortusStrain RB51 as a Vector for Heterologous Protein Expression and Induction of Specific Th1 Type Immune Responses
Authors: Vemulapalli Ramesh , He Yongqun , Boyle Stephen M. , Sriranganathan Nammalwar , Schurig Gerhardt G. 
Published: July 2002

ABSTRACTBrucella abortusstrain RB51 is a stable, rough, attenuated mutant widely used as a live vaccine for bovine brucellosis. Our ultimate goal is to develop strain RB51 as a preferential vector for the delivery of protective antigens of other intracellular pathogens to which the induction of a strong Th1 type of immune response is needed for effective protection. As a first step in that direction, we studied the expression of a foreign reporter protein, β-galactosidase ofEscherichia coli, and the 65-kDa heat shock protein (HSP65) ofMycobacterium bovisin strain RB51. We cloned the promoter sequences ofBrucella sodCandgroEgenes in pBBR1MCS to generate plasmids pBBSODpro and pBBgroE, respectively. The genes for β-galactosidase (lacZ) and HSP65 were cloned in these plasmids and used to transform strain RB51. An enzyme assay in the recombinant RB51 strains indicated that the level of β-galactosidase expression is higher under thegroEpromoter than under thesodCpromoter. In strain RB51 containing pBBgroE/lacZ, but not pBBSODpro/lacZ, increased levels of β-galactosidase expression were observed after subjecting the bacteria to heat shock or following internalization into macrophage-like J774A.1 cells. Mice vaccinated with either of the β-galactosidase-expressing recombinant RB51 strains developed specific antibodies of predominantly the immunoglobulin G2a (IgG2a) isotype, and in vitro stimulation of their splenocytes with β-galactosidase induced the secretion of gamma interferon (IFN-γ), but not interleukin-4 (IL-4). A Th1 type of immune response to HSP65, as indicated by the presence of specific serum IgG2a, but not IgG1, antibodies, and IFN-γ, but not IL-4, secretion by the specific-antigen-stimulated splenocytes, was also detected in mice vaccinated with strain RB51 containing pBBgroE/hsp65. Studies with mice indicated that expression of β-galactosidase or HSP65 did not alter either the attenuation characteristics of strain RB51 or its vaccine efficacy againstB. abortus2308 challenge.
Clostridium perfringens
Iota Toxin: Binding Studies and Characterization of Cell Surface Receptor by Fluorescence-Activated Cytometry
Authors: Stiles Bradley G. , Hale Martha L. , Marvaud Jean-Christophe , Popoff Michel R. 
Published: July 2002

ABSTRACT

The binding characteristics of iota toxin, a binary enterotoxin produced by
Clostridium perfringens
type E, were studied by fluorescence-activated cytometry. The proteolytically activated binding component of iota toxin, iota b (Ib), bound to various cell types when incubated at 4, 25, or 37°C for 10 min. The binding of Ib was inhibited by antisera against
C. perfringens
type E or
Clostridium spiroforme
culture supernatants, but not
C. perfringens
types C or D. Pretreatment of Vero cells with glycosidases or lectins did not affect Ib interactions, while pronase effectively prevented Ib binding to the cell surface. The Ib protomer (Ibp) bound to the cell surface, but trypsinization of Ibp was necessary for docking of the ADP-ribosylating component, iota a (Ia). Ia attached to cell-bound Ib within 10 min at 37°C, but surface levels of Ia decreased 90% after 30 min and were undetectable by 60 min. Detectable surface levels of Ib also diminished over time, and Western blot analysis suggested internalization or embedment of Ib into the membrane.
Complementation ofBrucella abortusRB51 with a FunctionalwboAGene Results in O-Antigen Synthesis and Enhanced Vaccine Efficacy but No Change in Rough Phenotype and Attenuation
Authors: Vemulapalli Ramesh , He Yongqun , Buccolo Larissa S. , Boyle Stephen M. , Sriranganathan Nammalwar , Schurig Gerhardt G. 
Published: July 2002

ABSTRACTBrucella abortusRB51 is a stable rough, attenuated mutant vaccine strain derived from the virulent strain 2308. Recently, we demonstrated that thewboAgene in RB51 is disrupted by an IS711element (R. Vemulapalli, J. R. McQuiston, G. G. Schurig, N. Srirauganathan, S. M. Halling, and S. M. Boyle, Clin. Diagn. Lab. Immunol. 6:760–764, 1999). Disruption of thewboAgene in smooth, virulentB. abortus,Brucella melitensis, andBrucella suisresults in rough, attenuated mutants which fail to produce the O polysaccharide (O antigen). In this study, we explored whether thewboAgene disruption is responsible for the rough phenotype of RB51. We complemented RB51 with a functionalwboAgene, and the resulting strain was designated RB51WboA. Colony and Western blot analyses indicated that RB51WboA expressed the O antigen; immunoelectron microscopy revealed that the O antigen was present in the cytoplasm. Crystal violet staining, acryflavin agglutination, and polymyxin B sensitivity studies indicated that RB51WboA had rough phenotypic characteristics similar to those of RB51. Bacterial clearance studies of BALB/c mice indicated no increase in the survival ability of RB51WboA in vivo compared to that of RB51. Vaccination of mice with live RB51WboA induced antibodies to the O antigen which were predominantly of the immunoglobulin G2a (IgG2a) and IgG3 isotypes. After in vitro stimulation of splenocytes with killed bacterial cells, quantitation of gamma interferon in the culture supernatants indicated that RB51WboA immunization induced higher levels of gamma interferon than immunization with RB51. Mice vaccinated with RB51WboA were better protected against a challenge infection with the virulent strain 2308 than those vaccinated with RB51. These studies indicate that in addition to the disruption of thewboAgene there is at least one other mutation in RB51 responsible for its rough phenotype. These studies also suggest that the expressed O antigen in RB51WboA is responsible either directly or indirectly for the observed enhancement in the T-cell response.
Molecular Cloning and Expression of a Gene EncodingCryptosporidium parvumGlycoproteins gp40 and gp15
Authors: Cevallos Ana Maria , Zhang Xiaoping , Waldor Matthew K. , Jaison Smitha , Zhou Xiaoyin , Tzipori Saul , Neutra Marian R. , Ward Honorine D. 
Published: July 2002

ABSTRACTCryptosporidium parvumis a significant cause of diarrheal disease worldwide. The specific molecules that mediateC. parvum-host cell interactions and the molecular mechanisms involved in the pathogenesis of cryptosporidiosis are unknown. In this study we have shown that gp40, a mucin-like glycoprotein, is localized to the surface and apical region of invasive stages of the parasite and is shed from its surface. gp40-specific antibodies neutralize infection in vitro, and native gp40 binds specifically to host cells, implicating this glycoprotein inC. parvumattachment to and invasion of host cells. We have cloned and sequenced a gene designatedCpgp40/15that encodes gp40 as well as gp15, an antigenically distinct, surface glycoprotein also implicated inC. parvum-host cell interactions. Analysis of the deduced amino acid sequence of the 981-bpCpgp40/15revealed the presence of an N-terminal signal peptide, a polyserine domain, multiple predictedO-glycosylation sites, a single potentialN-glycosylation site, and a hydrophobic region at the C terminus, a finding consistent with what is required for the addition of a GPI anchor. There is a single copy ofCpgp40/15in theC. parvumgenome, and this gene does not contain introns. Our data indicate that the twoCpgp40/15-encoded proteins, gp40 and gp15, are products of proteolytic cleavage of a 49-kDa precursor protein which is expressed in intracellular stages of the parasite. The surface localization of gp40 and gp15 and their involvement in the host-parasite interaction suggest that either or both of these glycoproteins may serve as effective targets for specific preventive or therapeutic measures for cryptosporidiosis.
Cloning and Sequence Analysis of a Highly PolymorphicCryptosporidium parvumGene Encoding a 60-Kilodalton Glycoprotein and Characterization of Its 15- and 45-Kilodalton Zoite Surface Antigen Products
Authors: Strong William B. , Gut Jiri , Nelson Richard G. 
Published: July 2002

ABSTRACTThe apicomplexan parasiteCryptosporidium parvumis a major cause of serious diarrheal disease in both humans and animals. No efficacious chemo- or immunotherapies have been identified for cryptosporidiosis, but certain antibodies directed against zoite surface antigens and/or proteins shed by gliding zoites have been shown to neutralize infectivity in vitro and/or to passively protect against, or ameliorate, disease in vivo. We previously used monoclonal antibody 11A5 to identify a 15-kDa surface glycoprotein that was shed behind motile sporozoites and was recognized by several lectins that neutralized parasite infectivity for cultured epithelial cells. Here we report the cloning and sequence analysis of the gene encoding this 11A5 antigen. Surprisingly, the gene encoded a 330-amino-acid, mucin-like glycoprotein that was predicted to contain an N-terminal signal peptide, a homopolymeric tract of serine residues, 36 sites of O-linked glycosylation, and a hydrophobic C-terminal peptide specifying attachment of a glycosylphosphatidylinositol anchor. The single-copy gene lacked introns and was expressed during merogony to produce a 60-kDa precursor which was proteolytically cleaved to 15- and 45-kDa glycoprotein products that both localized to the surface of sporozoites and merozoites. The gp15/45/60 gene displayed a very high degree of sequence diversity amongC. parvumisolates, and the numerous single-nucleotide and single-amino-acid polymorphisms defined five to six allelic classes, each characterized by additional intra-allelic sequence variation. The gp15/45/60 single-nucleotide polymorphisms will prove useful for haplotyping and fingerprinting isolates and for establishing meaningful relationships betweenC. parvumgenotype and phenotype.