bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antigenic Variation of
Anaplasma Marginale
: Major Surface Protein 2 Diversity during Cyclic Transmission between Ticks and Cattle
Authors: Barbet A. F. , Yi Jooyoung , Lundgren Anna , McEwen B. R. , Blouin E. F. , Kocan K. M. 
Published: July 2002

ABSTRACT

The rickettsial pathogen
Anaplasma marginale
expresses a variable immunodominant outer membrane protein, major surface protein 2 (MSP2), involved in antigenic variation and long-term persistence of the organism in carrier animals. MSP2 contains a central hypervariable region of about 100 amino acids that encodes immunogenic B-cell epitopes that induce variant-specific antibodies during infection. Previously, we have shown that MSP2 is encoded on a polycistronic mRNA transcript in erythrocyte stages of
A. marginale
and defined the structure of the genomic expression site for this transcript. In this study, we show that the same expression site is utilized in stages of
A. marginale
infecting tick salivary glands. We also analyzed the variability of this genomic expression site in Oklahoma strain
A. marginale
transmitted from in vitro cultures to cattle and between cattle and ticks. The structure of the expression site and flanking regions was conserved except for sequence that encoded the MSP2 hypervariable region. At least three different MSP2 variants were encoded in each
A. marginale
population. The major sequence variants did not change on passage of
A. marginale
between culture, acute erythrocyte stage infections, and tick salivary glands but did change during persistent infections of cattle. The variant types found in tick salivary glands most closely resembled those present in bovine blood at the time of acquisition of infection, whether infection was acquired from an acute or from a persistent rickettsemia. These variations in structure of an expression site for a major, immunoprotective outer membrane protein have important implications for vaccine development and for obtaining an improved understanding of the mechanisms of persistence of ehrlichial infections in humans, domestic animals, and reservoir hosts.
Plasmodium falciparum
Homologue of the Genes for
Plasmodium vivax
and
Plasmodium yoelii
Adhesive Proteins, Which Is Transcribed but Not Translated
Authors: Taylor Helen M. , Triglia Tony , Thompson Jenny , Sajid Mohammed , Fowler Ruth , Wickham Mark E. , Cowman Alan F. , Holder Anthony A. 
Published: July 2002

ABSTRACT

The 235-kDa family of rhoptry proteins in
Plasmodium yoelii
and the two reticulocyte binding proteins of
P. vivax
comprise a family of proteins involved in host cell selection and erythrocyte invasion. Here we described a member of the gene family found in
P. falciparum
(
PfRH3
) that is transcribed in its entirety, under stage-specific control, with correct splicing of the intron, but appears not to be translated, probably due to two reading frameshifts at the 5′ end of the gene.
gp96-Peptide Vaccination of Mice against Intracellular Bacteria
Authors: Zügel Ulrich , Sponaas Anne-Marit , Neckermann Jutta , Schoel Bernd , Kaufmann Stefan H. E. 
Published: July 2002

ABSTRACTThis work demonstrates that gp96 preparations isolated from cells infected with intracellular bacteria induce cytotoxic T-lymphocyte responses and confer protection. Our findings extend previous reports on the immunogenicity of gp96-associated peptides to antigens derived from intracellular bacteria. Immunization with gp96 may therefore represent a promising vaccination strategy against bacterial pathogens.
Interleukin-6 Enhances Production of Anti-OspC Immunoglobulin G2b Borreliacidal Antibody
Authors: Remington Monica C. , Munson Erik L. , Callister Steven M. , Molitor Melanie L. , Christopherson John A. , DeCoster David J. , Lovrich Steven D. , Schell Ronald F. 
Published: July 2002

ABSTRACTProtection against infection withBorrelia burgdorferiis dependent primarily on induction of complement-dependent antibody that can kill the spirochete. Measuring the production of sustained high levels of borreliacidal antibody is thus paramount for determining potential vaccine efficacy. We investigated the borreliacidal antibody response in sera and the amount of antibody produced by cultured lymph node cells of C3H/HeJ mice vaccinated with outer surface protein C (OspC). We showed that recombinant OspC was a weak stimulant of borreliacidal antibody production compared to whole cells of OspC-expressingB. burgdorferi. Mice vaccinated withB. burgdorferiin adjuvant produced a high level (titer, 5,120) of anti-OspC borreliacidal antibody, which waned rapidly. Similarly, borreliacidal antibody production by cultured lymph node cells from vaccinated mice peaked soon after vaccination and then decreased. Treatment of lymph node cells with interleukin-6 (IL-6) augmented borreliacidal antibody production, particularly immunoglobulin G2b, whereas treatment with anti-IL-6 inhibited the borreliacidal response. These findings demonstrate a previously unrecognized role for IL-6 in borreliacidal antibody production that may have important implications for vaccine development.
Characterization of a Stress-Induced Alternate Sigma Factor, RpoS, of
Coxiella burnetii
and Its Expression during the Development Cycle
Authors: Seshadri Rekha , Samuel James E. 
Published: July 2002

ABSTRACT

Coxiella burnetii
is an obligate intracellular bacterium that resides in an acidified phagolysosome and has a remarkable ability to persist in the extracellular environment.
C. burnetii
has evolved a developmental cycle that includes at least two morphologic forms, designated large cell variants (LCV) and small cell variants (SCV). Based on differential protein expression, distinct ultrastructures, and different metabolic activities, we speculated that LCV and SCV are similar to typical logarithmic- and stationary-phase growth stages. We hypothesized that the alternate sigma factor, RpoS, a global regulator of genes expressed under stationary-phase, starvation, and stress conditions in many bacteria, regulates differential expression in life cycle variants of
C. burnetii
. To test this hypothesis, we cloned and characterized the major sigma factor, encoded by an
rpoD
homologue, and the stress response sigma factor, encoded by an
rpoS
homologue. The
rpoS
gene was cloned by complementation of an
Escherichia coli rpoS
null mutant containing an RpoS-dependent
lacZ
fusion (
osmY
::
lacZ
). Expression of
C. burnetii rpoS
was regulated by growth phase in
E. coli
(induced upon entry into stationary phase). A glutathione
S
-transferase–RpoS fusion protein was used to develop polyclonal antiserum against
C. burnetii
RpoS. Western blot analysis detected abundant RpoS in LCV but not in SCV. These results suggest that LCV and SCV are not comparable to logarithmic and stationary phases of growth and may represent a novel adaptation for survival in both the phagolysosome and the extracellular environment.
RecombinantActinobacillus actinomycetemcomitansCytolethal Distending Toxin Proteins Are Required To Interact To Inhibit Human Cell Cycle Progression and To Stimulate Human Leukocyte Cytokine Synthesis
Authors: Akifusa Sumio , Poole Stephen , Lewthwaite Jo , Henderson Brian , Nair Sean P. 
Published: July 2002

ABSTRACTIt has recently been discovered thatActinobacillus actinomycetemcomitans, an oral bacterium causing periodontitis, produces cytolethal distending toxin (CDT), a cell cycle-modulating toxin that has three protein subunits: CdtA, CdtB, and CdtC. In this study, we have cloned and expressed each toxin gene fromA. actinomycetemcomitansinEscherichia coliand purified the recombinant Cdt proteins to homogeneity. Individual Cdt proteins failed to induce cell cycle arrest of the human epithelial cell line HEp-2. The only combinations of toxin proteins causing cell cycle arrest were the presence of all three Cdt proteins and the combination of CdtB and CdtC. A similar experimental protocol was used to determine if recombinant Cdt proteins were able to induce human peripheral blood mononuclear cells (PBMCs) to produce cytokines. The individual Cdt proteins were able to induce the synthesis by PBMCs of interleukin-1β (IL-1β), IL-6, and IL-8 but not of tumor necrosis factor alpha, IL-12, or granulocyte-macrophage colony-stimulating factor, with CdtC being the most potent and CdtB being the least potent cytokine inducer. There was evidence of synergism between these Cdt proteins in the stimulation of cytokine production, most markedly with gamma interferon, which required the minimum interaction of CdtB and -C to stimulate production.
Plasmodium knowlesiProvides a Rapid In Vitro and In Vivo Transfection System That Enables Double-Crossover Gene Knockout Studies
Authors: Kocken Clemens H. M. , Ozwara Hastings , van der Wel Annemarie , Beetsma Annette L. , Mwenda Jason M. , Thomas Alan W. 
Published: July 2002

ABSTRACTTransfection technology for malaria parasites provides a valuable tool for analyzing gene function and correlating genotype with phenotype. Transfection models are even more valuable when appropriate animal models are available in addition to complete in vitro systems to be able to fully analyze parasite-host interactions. Here we describe the development of such a model by using the nonhuman primate malariaPlasmodium knowlesi. Blood-stage parasites were adapted to long-term in vitro culture. In vitro-adapted parasites could readapt to in vivo growth and regain wild-type characteristics after a single passage through an intact rhesus monkey.P. knowlesiparasites, either in vitro adapted or in vivo derived, were successfully transfected to generate circumsporozoite protein (CSP) knockout parasites by double-crossover mechanisms. In vitro-transfected and cloned CSP knockout parasites were derived in a time span of only 18 days. Microscopic evaluation of developing oocysts from mosquitoes that had fed on CSP knockout parasites confirmed the impairment of sporozoite formation observed inP. bergheiCSP knockout parasites. TheP. knowlesimodel currently is the only malaria system that combines rapid and precise double-crossover genetic manipulation procedures with complete in vitro as well as in vivo possibilities. This allows for full analysis ofP. knowlesigenotype-phenotype relationships and host-parasite interactions in a system closely related to humans.
Functional Analysis of theHelicobacter pylori cagPathogenicity Island Reveals Both VirD4-CagA-Dependent and VirD4-CagA-Independent Mechanisms
Authors: Selbach Matthias , Moese Stefan , Meyer Thomas F. , Backert Steffen 
Published: July 2002

ABSTRACTThe type IV secretion machinery encoded by thecagpathogenicity island (PAI) ofHelicobacter pylorihas been implicated in a series of host responses during infection. Here, we analyzed the function of 12cagPAI genes from bothcagI andcagII loci, including the completevirB/Dcomplex (virB4, virB7, virB8, virB9, virB10, virB11, andvirD4). We monitored interleukin-8 (IL-8) secretion, CagA translocation and tyrosine phosphorylation, and induction of a scattering (“hummingbird”) phenotype uponH. pyloriinfection of AGS gastric epithelial cells. For the first time, we have complemented individualcagPAI gene knockout mutants with their intact genes expressed from a shuttle vector and showed that complemented CagA and VirD4 restored wild-type function. Our results demonstrate that phenotypic changes and phosphorylation of CagA depended on allvirB/Dgenes and several other genes of thecagPAI. Induction of IL-8 secretion depended largely on the same set of genes but was independent of CagA and VirD4. Thus, CagA translocation and induction of IL-8 secretion are regulated by VirD4-CagA-dependent and VirD4-CagA-independent mechanisms, respectively. The function of VirD4 as a possible adapter protein which guides CagA into the type IV secretion channel is presented in a model.
Deletion of the Two-Component Histidine Kinase Gene (
CHK1
) of
Candida albicans
Contributes to Enhanced Growth Inhibition and Killing by Human Neutrophils In Vitro
Authors: Torosantucci Antonella , Chiani Paola , De Bernardis Flavia , Cassone Antonio , Calera Jose Antonio , Calderone Richard 
Published: July 2002

ABSTRACT

We have observed that human neutrophils (polymorphonuclear leukocytes [PMNs]) have an increased growth-inhibitory and killing effect on a strain of
Candida albicans
with a deletion of
CHK1
, a gene encoding a putative histidine kinase. The PMN effect was not due to increased phagocytosis of the null strain. This observation may partially explain the reduced virulence in a hematogenously disseminated murine model of candidiasis.
Site-Specific Proteolysis of the MALP-404 Lipoprotein Determines the Release of a Soluble Selective Lipoprotein-Associated Motif-Containing Fragment and Alteration of the Surface Phenotype of
Mycoplasma fermentans
Authors: Davis Kelley L. , Wise Kim S. 
Published: July 2002

ABSTRACT

The mature MALP-404 surface lipoprotein of
Mycoplasma fermentans
comprises a membrane-anchored N-terminal lipid-modified region responsible for macrophage activation (P. F. Mühlradt, M. Kieβ, H. Meyer, R. Süβmuth, and G. Jung, J. Exp. Med. 185:1951-1958, 1997) and an external hydrophilic region that contains the selective lipoprotein-associated (SLA) motif defining a family of lipoproteins from diverse but selective prokaryotes, including mycoplasmas (M. J. Calcutt, M. F. Kim, A. B. Karpas, P. F. Mühlradt, and K. S. Wise, Infect. Immun. 67:760-771, 1999). This family generally corresponds to a computationally defined group of orthologs containing the basic membrane protein (BMP) domain. Two discrete lipid-modified forms of the abundant MALP product which vary dramatically in ratio among isolates of
M. fermentans
occur on the mycoplasma surface: (i) MALP-404, the full-length mature product, and (ii) MALP-2, the Toll-like receptor 2-mediated macrophage-activating lipopeptide containing the N-terminal 14 residues of the mature lipoprotein. The role of posttranslational processing in the biogenesis of MALP-2 from the prototype MALP-404 SLA-containing lipoprotein was investigated. Detergent phase fractionation of cell-bound products and N-terminal sequencing of a newly discovered released fragment (RF) demonstrated that MALP-404 was subject to site-specific proteolysis between residues 14 and 15 of the mature lipoprotein, resulting in the cell-bound MALP-2 and soluble RF products. This previously unknown mechanism of posttranslational processing among mycoplasmas suggests that specific cleavage of some surface proteins may confer efficient “secretion” of extracellular products by these organisms, with concurrent changes in the surface phenotype. This newly identified form of variation may have significant implications for host adaptation by mycoplasmas, as well as other pathogens expressing lipoproteins of the SLA (BMP) family.
Protective Immunity againstMycobacterium tuberculosisInduced by Dendritic Cells Pulsed with both CD8+- and CD4+-T-Cell Epitopes from Antigen 85A
Authors: McShane Helen , Behboudi Shahriar , Goonetilleke Nilu , Brookes Roger , Hill Adrian V. S. 
Published: July 2002

ABSTRACTImmunization with DNA followed by modified vaccinia virus Ankara strain, both expressing the antigen 85A, induced both CD4+- and CD8+-T-cell responses in BALB/c mice. Following challenge withMycobacterium tuberculosis, this prime-boost regimen produced protection equivalent to that conferred byMycobacterium bovisBCG. Following immunization with dendritic cells pulsed with an antigen 85A CD4+- or CD8+-restricted epitope, alone or in combination, copresentation of both epitopes on the same dendritic cell was required for protection, demonstrating that induced CD8+T cells can play a protective role against tuberculosis.
Carcinoembryonic Antigen Family Receptor Recognition by Gonococcal Opa Proteins Requires Distinct Combinations of Hypervariable Opa Protein Domains
Authors: Bos Martine P. , Kao David , Hogan Daniel M. , Grant Christopher C. R. , Belland Robert J. 
Published: July 2002

ABSTRACT
Neisserial Opa proteins function as a family of adhesins that bind heparan sulfate proteoglycan (HSPG) or carcinoembryonic antigen family (CEACAM) receptors on human host cells. In order to define the CEACAM binding domain on Opa proteins, we tested the binding properties of a series of gonococcal (strain MS11) recombinants producing mutant and chimeric Opa proteins with alterations in one or more of the four surface-exposed loops. Mutagenesis demonstrated that the semivariable domain, present in the first loop, was completely dispensable for CEACAM binding. In contrast, the two hypervariable (HV) regions present in the second and third loops were essential for binding; deletion of either domain resulted in loss of receptor recognition. Deletion of the fourth loop resulted in a severe decrease in Opa expression at the cell surface and could therefore not be tested for CEACAM binding. Chimeric Opa variants, containing combinations of HV regions derived from different CEACAM binding Opa proteins, lost most of their receptor binding activity. Some chimeric variants gained HSPG binding activity. Together, our results indicate that full recognition of CEACAM receptors by Opa proteins requires a highly coordinate interplay between both HV regions. Furthermore, shuffling of HV regions may result in novel HSPG receptor binding activity.
Local Role for Tumor Necrosis Factor Alpha in the Pulmonary Inflammatory Response toMycobacterium tuberculosisInfection
Authors: Smith Sherilyn , Liggitt Denny , Jeromsky Elizabeth , Tan Xiaoxia , Skerrett Shawn J. , Wilson Christopher B. 
Published: July 2002

ABSTRACTThe local intrapulmonary role of tumor necrosis factor alpha (TNF-α) in a protective host response during acute and chronic infection withMycobacterium tuberculosisis incompletely understood. To directly assess its role in the intrapulmonary immune response, we compared the responses of transgenic mice with a local pulmonary blockade of TNF-α (SPCTNFRIIFc mice) to mice with globally inhibited TNF-α (TNFRKO mice) and mice with normal immune systems (control mice). Consistent with previous reports, 100% of TNFRKO mice died by 28 days after aerosol infection, and these mice had markedly increased numbers of bacteria and widespread tissue necrosis in their lungs compared to controls. The median survival time of the SPCTNFRIIFc mice was 142 days, and 75% died by 180 days. Even though the numbers of bacteria in the lungs of the SPCTNFRIIFc mice were marginally increased compared to controls, these mice had a persistent neutrophilic inflammatory response and increased expression of proinflammatory cytokines (interleukin-1α/β [IL-1α/β], IL-18, gamma interferon, IL-6, and macrophage migration inhibitory factor) and chemokines (eotaxin, macrophage inflammatory protein 1α/β, gamma interferon-inducible protein 10, macrophage chemotaxic protein 1, and TCA-3) in their lungs. These studies with the SPCTNFRIIFc mice provide direct evidence for the local importance of TNF-α in the proper regulation of host defense toM. tuberculosis. The studies also suggest that when the local actions of TNF-α are selectively impaired in the lungs, tissue destruction and death ensue, at least in part, due to persistent expression of proinflammatory mediators that would normally be downregulated.
Genome-Based Identification of Chromosomal Regions Specific for
Salmonella
spp
Authors: Hansen-Wester Imke , Hensel Michael 
Published: July 2002

ABSTRACT

Acquisition of genomic elements by horizontal gene transfer represents an important mechanism in the evolution of bacterial species. Pathogenicity islands are a subset of horizontally acquired elements present in various pathogens. These elements are frequently located adjacent to tRNA genes. We performed a comparative genome analysis of
Salmonella enterica
serovars Typhi and Typhimurium and
Escherichia coli
and scanned tRNA loci for the presence of species-specific, horizontally acquired genomic elements. A large number of species-specific elements were identified. Here, we describe the characteristics of four large chromosomal insertions at tRNA genes of
Salmonella
spp. The tRNA-associated elements harbor various genes previously identified as single virulence genes, indicating that these genes have been acquired with large chromosomal insertions. Southern blot analyses confirmed that the tRNA-associated elements are specific to
Salmonella
and also indicated a heterogeneous distribution within the salmonellae. Systematic scanning for insertions at tRNA genes thus represents a tool for the identification of novel pathogenicity islands.
Construction, Characterization, and Animal Testing of WRSd1, a
Shigella dysenteriae
1 Vaccine
Authors: Venkatesan Malabi M. , Hartman Antoinette B. , Newland John W. , Ivanova Vessela S. , Hale Thomas L. , McDonough Marie , Butterton Joan 
Published: July 2002

ABSTRACT

WRSd1 is a
Shigella dysenteriae
1 vaccine containing deletions of the
virG(icsA)
gene required for intercellular spreading and a 20-kb chromosomal region encompassing the Shiga toxin genes (
stxAB
). WRSd1 was constructed from
S. dysenteriae
1 strain 1617 that was originally isolated during the 1968 to 1969 epidemic of Shiga dysentery in Guatemala. The
virG(icsA)
deletion was constructed from a streptomycin-resistant (Str
r
) mutant of 1617 by a filter mating procedures using a
virG(icsA)
deletion derivative, pΔvirG2. A colony that was invasive for HeLa cells and negative for the
virG(icsA)
gene by Southern blotting was grown anaerobically on plates containing chlorate for selection of resistant colonies that had lost the entire Shiga toxin gene. A
virG(icsA) stxAB
Str
r
mutant selected from the chlorate plates was designated WRSd1. This candidate vaccine was evaluated for safety, immunogenicity, and protective efficacy using the guinea pig keratoconjunctivitis model. WRSd1 was Sereny negative, and two applications of this strain to the cornea elicited a significant protective immune response against the
S. dysenteriae
1 O antigen. Vaccination with WRSd1 conferred protection against challenge with each of three virulent
S. dysenteriae
1 strains. Since a vaccine protecting against multiple
Shigella
species is required for most areas where
Shigella
is endemic, protection studies using a combination vaccine of
Shigella sonnei
vaccine strain WRSS1,
Shigella flexneri
2a vaccine strain SC602, and WRSd1 were also performed. Guinea pigs vaccinated with a mixture of equal amounts of the three vaccine strains were protected against challenge with each of the homologous virulent strains. Unlike WRSS1 and SC602, however, the level of protection afforded by WRSd1 in a combination vaccine was lower than the protection elicited by a pure culture. A current Good Manufacturing Practice product of WRSd1 given intragastrically to rhesus monkeys proved safe and immunogenic.