bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloning and Sequencing of the Genes Downstream of thewbfGene Cluster ofVibrio choleraeSerogroup O139 and Analysis of the Junction Genes in Other Serogroups
Authors: Sozhamannan Shanmuga , Deng Ying Kang , Li Manrong , Sulakvelidze Alexander , Kaper James B. , Johnson Judith A. , Nair G. Balkrish , Morris J. Glenn 
Published: December 2019

ABSTRACTThe DNA sequence of the O-antigen biosynthesis cluster (wbf) of a recently emergent pathogen,Vibrio choleraeserogroup O139, has been determined. Here we report the sequence of the genes downstream of the O139wbfXgene and analysis of the genes flanking thewbfgene cluster in other serogroups. The gene downstream ofwbfX, designatedrjg(right junction gene), is predicted to be not required for O-antigen biosynthesis but appears to be a hot spot for DNA rearrangements. Several variants of therjggene (three different insertions and a deletion) have been found in other serogroups. DNA dot blot analysis of 106V. choleraestrains showed the presence of the left and right junction genes,gmhDandrjg, respectively, in all strains. Further, these genes mapped to a single I-CeuI fragment in all 21 strains analyzed by pulsed-field gel electrophoresis, indicating a close linkage. The insertion sequence element IS1358, found in both O1 and O139wb* regions, is present in 61% of the strains tested; interestingly, where present, it is predominantly linked to thewb* region. These results indicated a cassette-like organization of thewb* region, with the conserved genes (gmhDandrjg) flanking the divergent, serogroup-specificwb* genes and IS1358. A similar organization of thewb* region in other serogroups raises the possibility of the emergence of new pathogens by homologous recombination via the junction genes.
Use of In Vivo-Regulated Promoters To Deliver Antigens from Attenuated
Salmonella enterica
var. Typhimurium
Authors: Dunstan Sarah J. , Simmons Cameron P. , Strugnell Richard A. 
Published: December 2019

ABSTRACT

This study describes the construction and analysis of three in vivo-inducible promoter expression plasmids, containing p
nirB
, p
pagC
, and p
katG
, for the delivery of foreign antigens in the Δ
aroAD
mutant of
Salmonella enterica
var. Typhimurium (hereafter referred to as
S. typhimurium
). The reporter genes encoding β-galactosidase and firefly luciferase were used to assess the comparative levels of promoter activity in
S. typhimurium
in vitro in response to different induction stimuli and in vivo in immunized mice. It was determined that the p
pagC
construct directed the expression of more β-galactosidase and luciferase in
S. typhimurium
than the p
nirB
and p
katG
constructs, both in vitro and in vivo. The gene encoding the C fragment of tetanus toxin was expressed in the
aroAD
mutant of
S. typhimurium
(BRD509) under the control of the three promoters. Mice orally immunized with attenuated
S. typhimurium
expressing C fragment under control of the
pagC
promoter [BRD509(pKK/p
pagC
/C frag)] mounted the highest tetanus toxoid-specific serum antibody response. Levels of luciferase expression in vivo and C-fragment expression in vitro from the
pagC
promoter appeared to be equivalent to if not lower than the levels of expression detected with the constitutive
trc
promoter. However, mice immunized with BRD509(pKK/p
pagC
/C frag) induced significantly higher levels of tetanus toxoid-specific antibody than BRD509(pKK/C frag)-immunized mice, suggesting that the specific location of foreign antigen expression may be important for immunogenicity. Mutagenesis of the ribosome binding sites (RBS) in the three promoter/C fragment expression plasmids was also performed. Despite optimization of the RBS in the three different promoter elements, the expression levels in vivo and overall immunogenicity of C fragment when delivered to mice by attenuated
S. typhimurium
were not affected. These studies suggest that in vivo-inducible promoters may give rise to enhanced immunogenicity and increase the efficacy of
S. typhimurium
as a vaccine vector.
Dual Role of Interleukin-10 in Murine Lyme Disease: Regulation of Arthritis Severity and Host Defense
Authors: Brown Jeanette P. , Zachary James F. , Teuscher Cory , Weis Janis J. , Wooten R. Mark 
Published: December 2019

ABSTRACTIn the murine model of Lyme disease, C3H/He mice exhibit severe arthritis while C57BL/6N mice exhibit mild lesions when infected withBorrelia burgdorferi. Joint tissues from these two strains of mice harbor similar concentrations ofB. burgdorferi, suggesting that the difference in disease severity reflects differences in the magnitude of the inflammatory response toB. burgdorferilipoproteins. Stimulation of bone marrow macrophages from C3H/HeN mice with theB. burgdorferilipoprotein OspA resulted in higher-level production of the inflammatory mediators tumor necrosis factor alpha, nitric oxide, and interleukin-6 (IL-6) than that of macrophages from C57BL/6N mice. In contrast, macrophages from C57BL/6N mice consistently produced larger amounts of the anti-inflammatory cytokine IL-10 than did C3H/HeN macrophages. Addition of recombinant IL-10 suppressed the production of inflammatory mediators by macrophages from both strains. IL-10 was found to modulateB. burgdorferi-induced inflammation in vivo, since C57BL/6J mice deficient in IL-10 (IL-10−/−) developed more severe arthritis than wild-type C57BL/6J mice. The increase in arthritis severity was associated with a 10-fold decrease in the number ofB. burgdorferiorganisms present in ankle tissues from IL-10−/−mice. These findings suggest that in C57BL/6 mice, IL-10-dependent regulation of arthritis severity occurs at the expense of effective control of bacterial numbers.
Purification and Characterization of Novel Toxin Produced byVibrio choleraeO1
Authors: Walia Kamini , Ghosh Sujata , Singh Harminder , Nair G. B. , Ghosh Amit , Sahni Girish , Vohra Harpreet , Ganguly Nirmal Kumar 
Published: December 2019

ABSTRACTVibrio choleraeWO7 (serogroup O1) isolated from patients with diarrhea produces an extracellular toxin despite the absence ofctx,zot, andacegenes from its genome. The toxin elongates Chinese hamster ovary cells, produces fluid accumulation in ligated rabbit ileal loops, and agglutinates freshly isolated rabbit erythrocytes. Maximal production of this toxin (WO7 toxin) was seen in AKI medium with the pH adjusted to 8.5 at 37°C under shaking conditions. We purified this toxin to homogeneity by sequential ammonium sulfate precipitation, affinity chromatography using a fetuin-Sepharose CL-4B column, and gel filtration chromatography, which increased the specific activity of the toxin by 1.6 × 106-fold. The toxin is heat labile and sensitive to proteases and has a subunit structure consisting of two subunits with molecular masses of about 58 and 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Agglutination of GM1-coated sheep erythrocytes by toxin suggests that GM1 might be the physiologic receptor for WO7 toxin on the enterocytes. An immunodiffusion test between the antiserum raised against the purified WO7 toxin and the purified toxin gave a well-defined precipitation band. In the immunoblot assay, two bands were observed in the 58- and 40-kDa region. At the same time, antiserum against WO7 toxin failed to show any cross-reactivity with cholera toxin orEscherichia coliheat-labile toxin (LT1) in an immunodiffusion test or immunoblot assay. The enterotoxic activity of WO7 toxin could be inhibited by antiserum against purified WO7 toxin. Our results indicate that WO7 toxin is structurally and functionally distinct from other cholera toxins and that the enterotoxic activities expressed by WO7 toxin appear to contribute to the pathogenesis of disease associated withV. choleraeO1 strains.
Expression of the
soxR
Gene of
Pseudomonas aeruginosa
Is Inducible during Infection of Burn Wounds in Mice and Is Required To Cause Efficient Bacteremia
Authors: Ha Unhwan , Jin Shouguang 
Published: December 2019

ABSTRACT

Burn wounds are prone to infection by
Pseudomonas aeruginosa
, which is an opportunistic pathogen causing various human diseases. During infection, the bacterium senses environmental changes and regulates the expression of genes appropriate for survival. A purine-auxotrophic mutant of
P. aeruginosa
was unable to replicate efficiently on burn wounds, suggesting that burn wounds are purine-deficient environments. An in vivo expression technology based on
purEK
gene expression was applied to the burned mouse infection model to isolate
P. aeruginosa
genes that are specifically induced during infection. Four such in vivo-inducible (
ivi
) genetic loci were identified, including the gene for a superoxide response regulator (
soxR
), the gene for a malate synthase G homologue (
glcG
), an antisense transcript of a putative regulator responding to copper (
copR
), and an uncharacterized genetic locus. SoxR of
Escherichia coli
is known to regulate genes involved in protecting the bacterium against oxidative stress. The expression of
soxR
was proven to be highly inducible during the infection of burned mice and also inducible by treatment with paraquat, which is a redox-cycling reagent generating intracellular superoxide. The SoxR protein functions as an autorepressor in the absence of paraquat, whereas in the presence of paraquat, this autorepression is diminished. Furthermore, a
soxR
null mutant was shown to be much more sensitive than wild-type
P. aeruginosa
to macrophage-mediated killing. In support of this observation, a
soxR
null mutant exhibited a significant delay in causing systemic infections in the burned mice. Since most mortality in burn patients is caused by systemic infection, the defect in the ability to cause efficient bacteremia in burned mice suggests an important role of the
soxR
gene in the infection of burn wounds.
Neutropenia Restores Virulence to an Attenuated Cu,Zn Superoxide Dismutase-Deficient
Haemophilus ducreyi
Strain in the Swine Model of Chancroid
Authors: San Mateo Lani R. , Toffer Kristen L. , Orndorff Paul E. , Kawula Thomas H. 
Published: December 2019

ABSTRACT

Haemophilus ducreyi
causes chancroid, a sexually transmitted cutaneous genital ulcer disease associated with increased heterosexual transmission of human immunodeficiency virus.
H. ducreyi
expresses a periplasmic copper-zinc superoxide dismutase (Cu,Zn SOD) that protects the bacterium from killing by exogenous superoxide in vitro. We hypothesized that the Cu,Zn SOD would protect
H. ducreyi
from immune cell killing, enhance survival, and affect ulcer development in vivo. In order to test this hypothesis and study the role of the Cu,Zn SOD in
H. ducreyi
pathogenesis, we compared a Cu,Zn SOD-deficient
H. ducreyi
strain to its isogenic wild-type parent with respect to survival and ulcer development in immunocompetent and immunosuppressed pigs. The Cu,Zn SOD-deficient strain was recovered from significantly fewer inoculated sites and in significantly lower numbers than the wild-type parent strain or a merodiploid (

sodC
+
sodC

) strain after infection of immunocompetent pigs. In contrast, survival of the wild-type and Cu,Zn SOD-deficient strains was not significantly different in pigs that were rendered neutropenic by treatment with cyclophosphamide. Ulcer severity in pigs was not significantly different between sites inoculated with wild type and sites inoculated with Cu,Zn SOD-deficient
H. ducreyi
. Our data suggest that the periplasmic Cu,Zn SOD is an important virulence determinant in
H. ducreyi
, protecting the bacterium from host immune cell killing and contributing to survival and persistence in the host.
Development of Antibodies against Chondroitin Sulfate A-AdherentPlasmodium falciparumin Pregnant Women
Authors: Maubert Bertrand , Fievet Nadine , Tami Germaine , Cot Michel , Boudin Christian , Deloron Philippe 
Published: December 2019

ABSTRACTIn areas wherePlasmodium falciparumis endemic, pregnant women are at increased risk for malaria, and this risk is greatest during the first pregnancy. The placenta sequesters parasites that are able to cytoadhere to chondroitin sulfate A (CSA), a molecule expressed by the placental syncytiotrophoblast, while parasites from a nonpregnant host do not bind to CSA. Cytoadherence is mediated by the expression of variants of theP. falciparum-erythrocyte membrane protein 1 family. Each member of this molecule family induces antibodies that specifically agglutinate infected erythrocytes and inhibit their cytoadherence ability. We investigated whether the higher susceptibility of primigravidae was related to the lack of immune response towards CSA-binding parasites. In a cross-sectional study, primigravidae delivering with a noninfected placenta were less likely to have antibodies agglutinating CSA-binding parasites than multigravidae (P< 0.01). In contrast, parasites from nonpregnant hosts were as likely to be recognized by the sera from women of various parities. In a longitudinal study, at 6 months of pregnancy, antibodies against CSA-binding parasites were present in 31.8% of primigravidae and in 76.9% of secundigravidae (P= 0.02). The antibodies against CSA-binding parasites inhibited the cytoadherence of a CSA-adherent parasite strain to the human placental trophoblast. Our data support the idea that the higher susceptibility of primiparae is related to a lack of a specific immune response to placental parasites.
Functional Characterization of Type IV Pili Expressed on Diarrhea-Associated Isolates of
Aeromonas
species
Authors: Kirov Sylvia M. , O’Donovan Lisa A. , Sanderson Kevin 
Published: December 2019

ABSTRACT

Our past work has shown that long, flexible type IV pili (single or in bundles) are the predominant pili expressed on fecal isolates of diarrhea-associated species of
Aeromonas
(
Aeromonas veronii
biovar sobria and
A. caviae
). They represent a family of type IV pili which we have designated Bfp (for bundle-forming pili). Reports from Japan suggest that Bfp are intestinal colonization factors. This study presents compelling evidence to support this conclusion.
Aeromonas
bacteria and/or Bfp purified from a strain of
A. veronii
biovar sobria were shown to adhere to epithelial and intestinal cell lines, freshly isolated human enterocytes, and fresh and fixed human and rabbit intestinal tissues, as determined by light and electron microscopy and immunohistochemical detection. Removal of Bfp by mechanical means decreased adhesion to cell lines by up to 80%. Purified Bfp blocked adhesion of the test strain to intestinal cells in a dose-dependent manner. Adhesion was also blocked by the Fab fraction of anti-Bfp immunoglobulin G. Moreover, ultrastructural studies (ruthenium red staining and transmission and scanning electron microscopy) demonstrated for the first time that
Aeromonas
adhesion to human enterocytes is pilus mediated and suggested that Bfp may also promote colonization by forming bacterium-to-bacterium linkages. Bfp-positive isolates examined for type IV pilus-mediated twitching motility in agar and slide culture assays developed for
Pseudomonas aeruginosa
did not, however, exhibit this function.
The Endogenous Balance of Soluble Tumor Necrosis Factor Receptors and Tumor Necrosis Factor Modulates Cachexia and Mortality in Mice Acutely Infected withTrypanosoma cruzi
Authors: Truyens Carine , Torrico Faustino , Lucas Rudolf , De Baetselier Patrick , Buurman Wim A. , Carlier Yves 
Published: December 2019

ABSTRACTTo better understand the role of tumor necrosis factor (TNF) duringTrypanosoma cruziinfection in BALB/c mice, we have investigated the kinetics of circulating tumor necrosis factor (TNF), soluble TNF receptor 1 (sTNR1), and sTNFR2 levels, as well as the interactions between such factors, in relation to parasitemia, cachexia, and mortality of acutely infected animals. Our data show that the parasitemic phase ofT. cruziinfection in mice is associated with high levels of circulating TNF and sTNFR2, resulting in the formation of cytokine-receptor complexes and some degree of neutralization of TNF bioactivity. Although sTNR2 levels always exceeded TNF levels, low sTNFR/TNF circulating ratios were associated with cachexia in all infected mice, whereas the lowest ratios were observed in dying animals harboring the highest parasitemia. We also studied the modulation of sTNFR/TNF ratios induced by anti-TNF antibodies administered to infected animals and their consequences on the outcome of the infection. The injection of anti-TNF monoclonal antibody (MAb) TN3 into infected mice resulted in a paradoxical overproduction of TNF (associated with a higher parasitemia), lowered the sTNFR/TNF circulating ratios, and considerably worsened cachexia and mortality of animals. Another anti-TNF MAb (1F3F3) decreased the in vivo availability of TNF as well as parasite levels and reduced cachexia. Altogether, such results highlight that, besides playing a beneficial role early in infection, TNF also triggers harmful effects in the parasitemic phase, which are limited by the in vivo simultaneous endogenous production of soluble receptors.
Temporal Sequence of Pulmonary and Systemic Inflammatory Responses to Graded Polymicrobial Peritonitis in Mice
Authors: Stamme Cordula , Bundschuh Daniela Sophie , Hartung Thomas , Gebert Ulla , Wollin Lutz , Nüsing Rolf , Wendel Albrecht , Uhlig Stefan 
Published: December 2019

ABSTRACTThe lungs are the remote organ most commonly affected in human peritonitis. The major goals of this study were to define the dose- and time-dependent relationship between graded septic peritonitis and systemic and pulmonary inflammatory responses in mice. BALB/c mice were treated with intraperitoneal polymicrobial inoculi and sacrificed at 3, 12, and 24 h. The treatment protocol resulted in distinct groups of animals with respect to mortality rate, kinetics, and concentrations of a broad spectrum of pro- and anti-inflammatory endogenous mediators, intrapulmonary bacterial accumulation, and static lung compliance. In sublethally infected mice, pulmonary bacterial proliferation was controlled. Levels of monocyte chemoattractant protein-1 (MCP-1), interleukin-10, interleukin-6, granulocyte colony-stimulating factor (G-CSF), and tumor necrosis factor (TNF) in plasma were elevated 3 h after infection exclusively. At 3 h, MCP-1, gamma interferon, and TNF were detected in extracts of pulmonary tissue or in bronchoalveolar lavage (BAL) fluid. Static lung compliance (Cst) was transiently decreased at 12 h. In contrast, in lethally infected mice pulmonary bacterial proliferation was not contained. Concentrations of MCP-1, G-CSF, and TNF in plasma were maximal at 24 h, as were pulmonary MCP-1 levels. Lung myeloperoxidase activity was increased at 3, 12, and 24 h.Cstwas reduced after 3 h and did not reach control values at 24 h. Pulmonary cyclooxygenase-2 mRNA and eicosanoids in BAL fluid and plasma were elevated at 3 and 24 h. This study shows that polymicrobial peritonitis in mice leads to dose-dependent systemic and pulmonary inflammation accompanied by a decrease in lung compliance.
Repeated Administration of Synthetic Oligodeoxynucleotides Expressing CpG Motifs Provides Long-Term Protection against Bacterial Infection
Authors: Klinman Dennis M. , Conover Jackie , Coban Cevahir 
Published: December 2019

ABSTRACTSynthetic oligodeoxynucleotides (ODN) expressing unmethylated CpG motifs stimulate an innate immune response characterized by the production of polyreactive immunoglobulin M antibodies and immunomodulatory cytokines. This immune response has been shown to protect mice from challenge byListeria monocytogenesandFrancisella tularensisfor up to 2 weeks. By repeatedly administering CpG ODN two to four times/month, we found that this protection could be maintained indefinitely. Protection was associated with a significant increase in the number of spleen cells that could be triggered by subsequent pathogen exposure to secrete gamma interferon and interleukin-6 in vivo (P< 0.01). ODN-treated animals remained healthy and developed neither macroscopic nor microscopic evidence of tissue damage or inflammation. Thus, repeated administration of CpG ODN may provide a safe means of conferring long-term protection against infectious pathogens.
Lysogenic Conversion of Environmental
Vibrio mimicus
Strains by CTXΦ
Authors: Faruque Shah M. , Rahman M. Mostafizur , Asadulghani  , Islam K. M. Nasirul , Mekalanos John J. 
Published: December 2019

ABSTRACT

The filamentous bacteriophage CTXΦ, which encodes cholera toxin (CT) in toxigenic
Vibrio cholerae
, is known to propagate by infecting susceptible strains of
V. cholerae
by using the toxin coregulated pilus (TCP) as its receptor and thereby causing the origination of new strains of toxigenic
V. cholerae
from nontoxigenic progenitors. Besides
V. cholerae
,
Vibrio mimicus
strains which are normally TCP negative have also been shown to occasionally produce CT and cause diarrhea in humans. We analyzed nontoxigenic
V. mimicus
strains isolated from surface waters in Bangladesh for susceptibility and lysogenic conversion by CTXΦ and studied the expression of CT in the lysogens by using genetically marked derivatives of the phage. Of 27
V. mimicus
strains analyzed, which were all negative for genes encoding TCP but positive for the regulatory gene
toxR
, 2 strains (7.4%) were infected by CTX-KmΦ, derived from strain SM44(P27459
ctx
::km), and the phage genome integrated into the host chromosome, forming stable lysogens. The lysogens spontaneously produced infectious phage particles in the supernatant fluids of the culture, and high titers of the phage could be achieved when the lysogens were induced with mitomycin C. This is the first demonstration of lysogenic conversion of
V. mimicus
strains by CTXΦ. When a genetically marked derivative of the replicative form of the CTXΦ genome carrying a functional
ctxAB
operon, pMSF9.2, was introduced into nontoxigenic
V. mimicus
strains, the plasmid integrated into the host genome and the strains produced CT both in vitro and inside the intestines of adult rabbits and caused mild-to-severe diarrhea in rabbits. This suggested that in the natural habitat infection of nontoxigenic
V. mimicus
strains by wild-type CTXΦ may lead to the origination of toxigenic
V. mimicus
strains which are capable of producing biologically active CT. The results of this study also supported the existence of a TCP-independent mechanism for infection by CTXΦ and showed that at least one species of
Vibrio
other than
V. cholerae
may contribute to the propagation of the phage.
Interleukin-6 and Interleukin-12 Participate in Induction of a Type 1 Protective T-Cell Response during Vaccination with a Tuberculosis Subunit Vaccine
Authors: Leal Irene S. , Smedegård Birgitte , Andersen Peter , Appelberg Rui 
Published: December 2019

ABSTRACTWe examined the role of cytokines in the development of gamma interferon (IFN-γ)-secreting protective T cells following immunization with a culture filtrate subunit vaccine againstMycobacterium tuberculosiscontaining the adjuvant dimethyldioctadecylammonium bromide (DDA). Depletion of either interleukin-6 (IL-6) or IL-12 with specific neutralizing antibodies during vaccination reduced the priming of T cells for antigen-specific proliferation and IFN-γ secretion. Such reduction was also observed in IL-6 gene-disrupted mice as compared to wild-type animals. IL-6 was found to play a role in the initial differentiation of Th1 cells but not in their expansion. The defect found after IL-6 depletion or in IL-6-knockout mice was compensated by the inclusion of recombinant mouse IL-12 in the vaccine. The induction of protective immunity against an intravenous or an aerosol challenge with live, virulentM. tuberculosiswas markedly reduced by neutralizing either IL-6 or IL-12 during immunization with the vaccine. Likewise, the effects of IL-6 neutralization were partially reversed by including IL-12 in the vaccine. Our data point to an important role of IL-6 and IL-12 in the generation of cell-mediated immunity to tuberculosis.