bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lysine Residue 117 of the FasG Adhesin of Enterotoxigenic
Escherichia coli
Is Essential for Binding of 987P Fimbriae to Sulfatide
Authors: Choi Byung-Kwon , Schifferli Dieter M. 
Published: December 2019

ABSTRACT

The FasG subunit of the 987P fimbriae of enterotoxigenic strains of
Escherichia coli
was previously shown to mediate fimbrial binding to a glycoprotein and a sulfatide receptor on intestinal brush borders of piglets. Moreover, the 987P adhesin FasG is required for fimbrial expression, since
fasG
null mutants are nonfimbriated. In this study,
fasG
was modified by site-directed mutagenesis to study its sulfatide binding properties. Twenty single mutants were generated by replacing positively charged lysine (K) or arginine (R) residues with small, nonpolar alanine (A) residues. Reduced levels of binding to sulfatide-containing liposomes correlated with reduced fimbriation and FasG surface display in four
fasG
mutants (R27A, R286A, R226A, and R368). Among the 16 remaining normally fimbriated mutants with wild-type levels of surface-exposed FasG, only one mutant (K117A) did not interact at all with sulfatide-containing liposomes. Four mutants (K117A, R116A, K118A, and R200A) demonstrated reduced binding to such liposomes. Since complete phenotypic dissociation between the structure and specific function of 987P was observed only with mutant K117A, this residue is proposed to play an essential role in the FasG-sulfatide interaction, possibly communicating with the sulfate group of sulfatide by hydrogen bonding and/or salt bridge formation. Residues K17, R116, K118, and R200 may stabilize this interaction.
Protection of Mice against Brucellosis by Vaccination withBrucella melitensisWR201(16MΔpurEK)
Authors: Hoover David L. , Crawford Robert M. , Van De Verg Lillian L. , Izadjoo Mina J. , Bhattacharjee Apurba K. , Paranavitana Chrysanthi M. , Warren Richard L. , Nikolich Mikeljon P. , Hadfield Ted L. 
Published: December 2019

ABSTRACTHuman brucellosis can be acquired from infected animal tissues by ingestion, inhalation, or contamination of the conjunctiva or traumatized skin by infected animal products. A vaccine to protect humans from occupational exposure or from zoonotic infection in areas where the disease is endemic would reduce an important cause of morbidity worldwide. Vaccines currently used in animals are unsuitable for human use. We tested a live, attenuated, purine-auxotrophic mutant strain ofBrucella melitensis, WR201, for its ability to elicit cellular and humoral immune responses and to protect mice against intranasal challenge withB. melitensis16M. Mice inoculated intraperitoneally with WR201 made serum antibody to lipopolysaccharide and non-O-polysaccharide antigens. Splenocytes from immunized animals released interleukin-2 (IL-2), gamma interferon, and IL-10 when cultured withBrucellaantigens. Immunization led to protection from disseminated infection but had only a slight effect on clearance of the challenge inoculum from the lungs. These studies suggest that WR201 should be further investigated as a vaccine to prevent human brucellosis.
Alternative Mechanism of Cholera Toxin Acquisition by
Vibrio cholerae
: Generalized Transduction of CTXΦ by Bacteriophage CP-T1
Authors: Fidelma Boyd E. , Waldor Matthew K. 
Published: December 2019

ABSTRACT

Horizontal transfer of genes encoding virulence factors has played a central role in the evolution of many pathogenic bacteria. The unexpected discovery that the genes encoding cholera toxin (
ctxAB
), the main cause of the profuse secretory diarrhea characteristic of cholera, are encoded on a novel filamentous phage named CTXΦ, has resulted in a renewed interest in the potential mechanisms of transfer of virulence genes among
Vibrio cholerae
. We describe here an alternative mechanism of cholera toxin gene transfer into nontoxigenic
V. cholerae
isolates, including strains that lack both the CTXΦ receptor, the toxin coregulated pilus (TCP), and
attRS
, the chromosomal attachment site for CTXΦ integration. A temperature-sensitive mutant of the
V. cholerae
generalized transducing bacteriophage CP-T1 (CP-T1ts) was used to transfer a genetically marked derivative of the CTX prophage into four nontoxigenic
V. cholerae
strains, including two
V. cholerae
vaccine strains. We demonstrate that CTXΦ transduced by CP-T1ts can replicate and integrate into these nontoxigenic
V. cholerae
strains with high efficiency. In fact, CP-T1ts transduces the CTX prophage preferentially when compared with other chromosomal markers. These results reveal a potential mechanism by which CTXΦ
+
V. cholerae
strains that lack the TCP receptor may have arisen. Finally, these findings indicate an additional pathway for reversion of live-attenuated
V. cholerae
vaccine strains.
Allelic Diversity and Antibody Recognition ofPlasmodium falciparumMerozoite Surface Protein 1 during Hypoendemic Malaria Transmission in the Brazilian Amazon Region
Authors: Da Silveira Lucimeire A. , Dorta Míriam L. , Kimura Emília A. S. , Katzin Alejandro M. , Kawamoto Fumihiko , Tanabe Kazuyuki , Ferreira Marcelo U. 
Published: December 2019

ABSTRACTThe polymorphic merozoite surface protein (MSP-1) ofPlasmodium falciparumis a major asexual blood-stage malaria vaccine candidate. The impact of allelic diversity on recognition of MSP-1 during the immune response remains to be investigated in areas of hypoendemicity such as the Brazilian Amazon region. In this study, PCR was used to type variable regions, blocks 2, 4, and 10, of themsp-1gene and to characterize major gene types (unique combinations of allelic types in variable blocks) inP. falciparumisolates collected across the Amazon basin over a period of 12 years. Twelve of the 24 possible gene types were found among 181 isolates, and 68 (38%) of them had more than one gene type. Temporal, but not spatial, variation was found in the distribution of MSP-1 gene types in the Amazon. Interestingly, some gene types occurred more frequently than expected from random assortment of allelic types in different blocks, as previously found in other areas of endemicity. We also compared the antibody recognition of polymorphic (block 2), dimorphic (block 6), and conserved (block 3) regions of MSP-1 in Amazonian malaria patients and clinically immune Africans, using a panel of recombinant peptides. Results were summarized as follows. (i) All blocks were targeted by naturally acquired cytophilic antibodies of the subclasses IgG1 and IgG3, but the balance between IgG1 and IgG3 depended on the subjects' cumulative exposure to malaria. (ii) The balance between IgG1 and IgG3 subclasses and the duration of antibody responses differed in relation to distinct MSP-1 peptides. (iii) Antibody responses to variable blocks 2 and 6 were predominantly type specific, but variant-specific antibodies that target isolate-specific repetitive motifs within block 2 were more frequent in Amazonian patients than in previously studied African populations.
Citrobacter rodentium espB
Is Necessary for Signal Transduction and for Infection of Laboratory Mice
Authors: Newman Joseph V. , Zabel Brian A. , Jha Sharda S. , Schauer David B. 
Published: December 2019

ABSTRACT

Citrobacter rodentium
is the causative agent of transmissible murine colonic hyperplasia and contains a locus of enterocyte effacement (LEE) similar to that found in enteropathogenic
Escherichia coli
(EPEC). EPEC
espB
is necessary for intimate attachment and signal transduction between EPEC and cultured cell monolayers. Mice challenged with wild-type
C. rodentium
develop a mucosal immunoglobulin A response to EspB. In this study,
C. rodentium espB
has been cloned and its nucleotide sequence has been determined.
C. rodentium espB
was found to have 90% identity to EPEC
espB
. A nonpolar insertion mutation in
C. rodentium espB
was constructed and used to replace the chromosomal wild-type allele. The
C. rodentium espB
mutant exhibited reduced cell association and had no detectable fluorescent actin staining activity on cultured cell monolayers. The
C. rodentium espB
mutant also failed to colonize laboratory mice following experimental inoculation. The
espB
mutation could be complemented with a plasmid-encoded copy of the gene, which restored both cell association and fluorescent actin staining activity, as well as the ability to colonize laboratory mice. These studies indicate that
espB
is necessary for signal transduction and for colonization of laboratory mice by
C. rodentium
.
Identification and Molecular Analysis of the Gene Encoding
Rickettsia typhi
Hemolysin
Authors: Radulovic Suzana , Troyer Jill M. , Beier Magda S. , Lau Audrey O. T. , Azad Abdu F. 
Published: December 2019

ABSTRACT

Rickettsia typhi
, the causative agent of murine typhus, grows directly within the host cell cytoplasm, accumulating a large number of progeny, and eventually lyses the cells. Typhus group rickettsiae (
R. typhi
and
R. prowazekii
) adhere to and lyse human and sheep erythrocytes. However, the molecular mechanism underlying erythrocyte lysis by
R. typhi
has not been defined. Here we describe the cloning and nucleotide sequence analysis of the gene (
tlyC
) encoding a hemolysin from
R. typhi
. DNA sequence analysis of
R. typhi tlyC
revealed an open reading frame of 912 bp, which encodes a protein of 304 amino acids with a predicted molecular mass of 38 kDa. To associate the
R. typhi tlyC
gene product with hemolytic activity, we performed complementation studies with hemolysin-negative
Proteus mirabilis
WPM111 (a HpmA
−
mutant of BA6163) transformed with
R. typhi tlyC
or
R. typhi GFPuv-tlyC
constructs. We demonstrated that the cloned
tlyC
gene conferred a hemolytic phenotype on an otherwise nonhemolytic mutant of
P. mirabilis
. The availability of the cloned
R. typhi tlyC
will permit further characterization and definition of its role in rickettsial virulence.
Isolation, Characterization, cDNA Cloning, and Antimicrobial Properties of Two Distinct Subfamilies of α-Defensins from Rhesus Macaque Leukocytes
Authors: Tang Yi-Quan , Yuan Jun , Miller Christopher J. , Selsted Michael E. 
Published: December 2019

ABSTRACTExperiments to isolate and characterize rhesus macaque myeloid α-defensins (RMADs) were conducted. Seven RMAD peptides were isolated and sequenced, and the cDNAs encoding six of these peptides and one other α-defensin from bone marrow were also characterized. Four of the RMADs were found to be highly similar to human neutrophil α-defensins HNP-1 to HNP-3, while the remaining four peptides were much more similar to human enteric α-defensin HD-5. Two α-defensin pairs differed only by the presence or absence of an additional arginine at the amino termini of their mature peptides, indicative of alternate posttranslational processing. The primary translation products of RMAD-1 to -8 are 94- and 96-amino-acid prepropeptides that are highly similar to those of human α-defensins. Immunolocalization experiments revealed a granular cytoplasmic pattern in the cytoplasms of neutrophils, indistinguishable from the pattern observed after immunostaining of human myeloid α-defensins in polymorphonuclear leukocytes. Each of the purified peptides was tested for its in vitro activities againstStaphylococcus aureus502a,Listeria monocytogenesEGD,Escherichia coliML35, andCryptococcus neoformans271A. Several of the peptides were microbicidal for the gram-positive bacteria andC. neoformansat defensin concentrations in the range of 2 to 5 μM. All of the peptides were bacteriostatic againstE. coli, but none were bactericidal for this organism. This study is the first to characterize the sequences and activities of α-defensins from nonhuman primates, data that should aid in delineating the role of these peptides in rhesus macaque host defense.
Purification and Immunoreactivity of Three Components from the 30/32-Kilodalton Antigen 85 Complex inMycobacterium tuberculosis
Authors: Lim Jae-Hyun , Park Jeong-Kyu , Jo Eun-Kyeong , Song Chang-Hwa , Min Dullei , Song Young-Ja , Kim Hwa-Jung 
Published: December 2019

ABSTRACTThe three proteins of the antigen 85 complex (85A, 85B, and 85C), which are major secretory products ofMycobacterium tuberculosis, were purified to homogeneity in large amounts by a combination of chromatography on hydroxylapatite, DEAE-Sepharose, and DEAE-Sephacel and gel filtration fromM. tuberculosisculture filtrate. Then we examined the immunological reactivity of the three proteins in tuberculosis patients and healthy controls. Antibody responses to the 85B and 85A proteins in patients were significantly greater than responses to the 85C protein. In contrast, all three antigens induced significant lymphoproliferation and gamma interferon production in peripheral blood mononuclear cells from healthy tuberculin reactors.
Anatomic Segmentation of the Intestinal Immune Response in Nonhuman Primates: Differential Distribution of B Cells after Oral and Rectal Immunizations to Sites Defined by Their Source of Vascularization
Authors: Eriksson Kristina , Quiding-Järbrink Marianne , Osek Jacek , Nordström Inger , Hjulström Maria , Holmgren Jan , Czerkinsky Cecil 
Published: December 2019

ABSTRACTWe show that the distribution of specific antibodies and antibody-secreting cells in the intestine after oral and rectal immunizations corresponds to the vascularization and lymph drainage patterns of the gut. Oral immunizations induce antibody responses along the parts of the intestine connected to the superior mesenteric vessels and lymph ducts, whereas rectal immunizations induce antibody responses along the parts of the intestine associated with the inferior mesenteric vessels and ducts.
Essential Functional Role of the Polysaccharide Intercellular Adhesin of
Staphylococcus epidermidis
in Hemagglutination
Authors: Mack Dietrich , Riedewald Joachim , Rohde Holger , Magnus Tim , Feucht Hubert H. , Elsner Holger-A. , Laufs Rainer , Rupp Mark E. 
Published: December 2019

ABSTRACT

Hemagglutination of erythrocytes is a common property of
Staphylococcus epidermidis
strains, which is related to adherence and biofilm formation and may be essential for the pathogenesis of biomaterial-associated infections caused by
S. epidermidis
. In three independent biofilm-producing, hemagglutination-positive
S. epidermidis
isolates, interruption of the
icaADBC
operon essential for polysaccharide intercellular adhesin (PIA) synthesis by Tn
917
insertions led to a hemagglutination-negative phenotype. An immunoglobulin G fraction of antiserum to PIA greatly reduced hemagglutination. Purified PIA led to a 64-fold decrease of hemagglutination titers of these strains; however, it did not mediate hemagglutination by itself. These observations define PIA as the hemagglutinin of
S. epidermidis
or at least as its major functional component.
Enteropathogenic
Escherichia coli
Inhibits Phagocytosis
Authors: Goosney Danika L. , Celli Jean , Kenny Brendan , Finlay B. Brett 
Published: December 2019

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) interacts with intestinal epithelial cells, activating host signaling pathways leading to cytoskeletal rearrangements and ultimately diarrhea. In this study, we demonstrate that EPEC interacts with the macrophage-like cell line J774A.1 to inhibit phagocytosis by these cells. Antiphagocytic activity was also observed in cultured RAW macrophage-like cells upon EPEC infection. The EPEC antiphagocytic phenotype was dependent on the type III secretion pathway of EPEC and its secreted proteins, including EspA, EspB, and EspD. Intimin and Tir mutants displayed intermediate antiphagocytic activity, suggesting that intimate attachment mediated by intimin-Tir binding may also play a role in antiphagocytosis. Tyrosine dephosphorylation of several host proteins was observed following infection with secretion-competent EPEC but not with secretion-deficient mutants. Dephosphorylation was detectable 120 min after infection with EPEC, directly correlating with the onset of the antiphagocytic phenotype. Inhibition of protein tyrosine phosphatases by pervanadate treatment increased the number of intracellular wild-type EPEC organisms to levels seen with secretion-deficient mutants, suggesting that dephosphorylation events are linked to the antiphagocytic phenotype. No tyrosine phosphatase activity was detected with the EPEC-secreted proteins, suggesting that EPEC induces antiphagocytosis via a different mechanism than
Yersinia
species. Taken together, the present findings demonstrate a novel function for EPEC-secreted proteins in triggering macrophage protein tyrosine dephosphorylation and inhibition of phagocytosis.
Therapy with a Combination of Low Doses of Interleukin 12 and Chloroquine Completely Cures Blood-Stage Malaria, Prevents Severe Anemia, and Induces Immunity to Reinfection
Authors: Mohan Karkada , Sam Hakeem , Stevenson Mary M. 
Published: December 2019

ABSTRACTThe immunoregulatory cytokine interleukin 12 (IL-12) induces host resistance against experimental malaria. In this study, we tested the feasibility of using IL-12 in combination with chloroquine (CQ) to rescue susceptible A/J mice from lethal blood-stagePlasmodium chabaudiAS infection. Combined treatment with low doses of CQ and IL-12 resulted in a >15-fold reduction in the parasite load and 100% survival of A/J mice with established infections. Compared to control mice, which succumbed to severe anemia, CQ-plus-IL-12-treated mice had significantly higher early- and late-stage erythroid-cell progenitors in the bone marrow and spleen, resulting in significantly higher hematocrits, erythrocyte counts, and percentages of reticulocytes. Production of parasite-specific gamma interferon (IFN-γ) by splenocytes from these mice was upregulated >20-fold relative to controls in parallel with enhanced IFN-γ mRNA expression. Further, enhanced responsiveness to IL-12 and increased downstream IFN-γ production in CQ-plus-IL-12-treated mice was evident from increased mRNA expression for the β1 and β2 subunits of IL-12 receptor in the splenocytes. Moreover, this combined therapy induced higher levels of anti-malaria antibodies than did CQ alone as well as sterile immunity against reinfection. Because IL-12 can be used at low doses and is effective even in established infections, it may be feasible to use this immunochemotherapeutic approach in human malaria.
Preliminary Assessment of the Safety and Immunogenicity of a New CTXΦ-Negative, Hemagglutinin/Protease-Defective El Tor Strain as a Cholera Vaccine Candidate
Authors: Benítez Jorge A. , García Luis , Silva Anisia , García Hilda , Fando Rafael , Cedré Barbara , Pérez Antonio , Campos Javier , Rodríguez Boris L. , Pérez JoséL. , Valmaseda Tania , Pérez Oliver , Pérez Alberto , Ramírez Margarita , Ledón Talena , Jidy Manuel Díaz , Lastre Miriam , Bravo Laura , Sierra Gustavo 
Published: December 2019

ABSTRACT

Vibrio cholerae
638 (El Tor, Ogawa), a new CTXΦ-negative hemagglutinin/protease-defective strain that is a cholera vaccine candidate, was examined for safety and immunogenicity in healthy adult volunteers. In a double-blind placebo-controlled study, no significant adverse reactions were observed in volunteers ingesting strain 638. Four volunteers of 42 who ingested strain 638 and 1 of 14 who received placebo experienced loose stools. The strain strongly colonized the human small bowel, as evidenced by its isolation from the stools of 37 of 42 volunteers.
V. cholerae
638, at doses ranging from 4 × 10
7
to 2 × 10
9
vibrios, elicited significant serum vibriocidal antibody and anti-Ogawa immunoglobulin A antibody secreting cell responses.
The Link between Phylogeny and Virulence in
Escherichia coli
Extraintestinal Infection
Authors: Picard Bertrand , Garcia José Sevali , Gouriou Stéphanie , Duriez Patrick , Brahimi Naïma , Bingen Edouard , Elion Jacques , Denamur Erick 
Published: December 2019

ABSTRACT

Previous studies suggesting a link between
Escherichia coli
phylogenetic groups and extraintestinal virulence have been hampered by the difficulty in establishing the intrinsic virulence of a bacterial strain. Indeed, unidentified virulence factors do exist, and the susceptibility of the host to infection is highly variable. To overcome these difficulties, we have developed a mouse model of extraintestinal virulence to test the virulence of the strains under normalized conditions. We then assessed the phylogenetic relationships compared to the
E. coli
reference (ECOR) collection, the presence of several known virulence determinants, and the lethality to mice of 82 human adult
E. coli
strains isolated from normal feces and during the course of extraintestinal infections. Commensal strains belong mainly to phylogenetic groups A and B1, are devoid of virulence determinants, and do not kill the mice. Strains exhibiting the same characteristics as the commensal strains can be isolated under pathogenic conditions, thus indicating the role of host-dependent factors, such as susceptibility linked to underlying disease, in the development of infection. Some strains of phylogenetic groups A, B1, and D are able to kill the mice, their virulence being most often correlated with the presence of virulence determinants. Lastly, strains of the B2 phylogenetic group represent a divergent lineage of highly virulent strains which kill the mice at high frequency and possess the highest level of virulence determinants. The observed link between virulence and phylogeny could correspond to the necessity of virulence determinants in a genetic background that is adequate for the emergence of a virulent clone, an expression of the interdependency of pathogenicity and metabolic activities in pathogenic bacteria.
Vaccination against Anthrax with Attenuated Recombinant Strains of
Bacillus anthracis
That Produce Protective Antigen
Authors: Barnard John P. , Friedlander Arthur M. 
Published: December 2019

ABSTRACT

The protective efficacy of several live, recombinant anthrax vaccines given in a single-dose regimen was assessed with Hartley guinea pigs. These live vaccines were created by transforming ΔANR and ΔSterne, two nonencapsulated, nontoxinogenic strains of
Bacillus anthracis
, with four different recombinant plasmids that express the anthrax protective antigen (PA) protein to various degrees. This enabled us to assess the effect of the chromosomal background of the strain, as well as the amount of PA produced, on protective efficacy. There were no significant strain-related effects on PA production in vitro, plasmid stability in vivo, survival of the immunizing strain in the host, or protective efficacy of the immunizing infection. The protective efficacy of the live, recombinant anthrax vaccine strains correlated with the anti-PA antibody titers they elicited in vivo and the level of PA they produced in vitro.