bluuebunny/crossref_metadata_2025_split huggingface dataset:
Listeria monocytogenesVirulence Factors That Stimulate Endothelial Cells
Authors: Drevets Douglas A. 
Published: December 2019

ABSTRACTListeria monocytogenesinfection of endothelial cells upregulates surface expression of adhesion molecules and stimulates neutrophil adhesion to infected cell monolayers. The experiments presented here tested the roles of specific bacterial virulence factors as triggers for this inflammatory phenotype and function. Human umbilical vein endothelial cell (HUVEC) monolayers were infected with wild-typeL. monocytogenesorL. monocytogenesmutants; then surface expression of E-selectin and neutrophil adhesion were measured. The results showed that ΔhlyandprfAmutants were the most crippled, requiring 100-fold more mutant bacteria than wild-type bacteria for analogous stimulation. By comparison,L. monocytogenesmutants with deletions ofactA,inlA,inlB,inlAB,plcA, andplcBresembled their parent strains, and a ΔplcA ΔplcBmutant displayed decreased intracellular growth rate but only a minor decrease in stimulation of E-selectin or neutrophil adhesion. Other experiments showed that cytochalasin D-treated HUVEC monolayers bound bacteria, but internalization and increased surface E-selectin and intercellular adhesion molecule-1 expression were profoundly inhibited. However, cytochalasin D had no effect on the HUVEC response to stimulation with lipopolysaccharide or tumor necrosis factor alpha. These data suggest that listeriolysin O production by infectingL. monocytogenescontributes to increased expression of surface E-selectin and intercellular adhesion molecule-1, but neither it nor intracellular replication are directly responsible for this event. Nonetheless it is possible that listeriolysin O potentiates the effect(s) of an other molecule(s) that directly triggers this response. Additionally, cellular invasion byL. monocytogenesappears to be critical for initiating the HUVEC response, potentially by providing a signal which results in upregulation of the necessary bacterial genes.
Bacterial Cytolysin Perturbs Round Window Membrane Permeability Barrier In Vivo: Possible Cause of Sensorineural Hearing Loss in Acute Otitis Media
Authors: Engel Frank , Blatz Rosemarie , Schliebs Reinhard , Palmer Michael , Bhakdi Sucharit 
Published: December 2019

ABSTRACT
The passage of radioiodinated streptolysin-O (SLO) and albumin through the round window membrane (RWM) was studied in vivo. When applied to the middle ear, SLO became quantitatively entrapped in this compartment and no passage to the cochlea occurred. However, flux of radioiodinated albumin through the toxin-damaged RWM was observed. We propose that the passage of noxious macromolecules, such as proteases, from a purulent middle-ear effusion may be facilitated by pore-forming toxins, resulting in cochlear damage and sensorineural hearing loss.
Immunization of
Aotus
Monkeys with Recombinant
Plasmodium falciparum
Hybrid Proteins Does Not Reproducibly Result in Protection from Malaria Infection
Authors: Kocken Clemens H. M. , Hundt Erika , Knapp Bernhard , Brazel Dieter , Enders Burkhard , Narum David L. , Wubben Jaqueline A. M. , Thomas Alan W. 
Published: December 2019

ABSTRACT

Plasmodium falciparum
antigens SERP, HRPII, MSAI, and 41-3 have shown promise as vaccine components. This study aimed at reproducing and extending previous results using three hybrid molecules. Antibody responses were reproduced in
Aotus
monkeys, but solid protection from a
P. falciparum
blood-stage challenge that showed an unintendedly enhanced pathogenicity was not observed.
Effect of Prior Experimental Human Enteropathogenic
Escherichia coli
Infection on Illness following Homologous and Heterologous Rechallenge
Authors: Donnenberg Michael S. , Tacket Carol O. , Losonsky Genevieve , Frankel Gad , Nataro James P. , Dougan Gordon , Levine Myron M. 
Published: December 2019

ABSTRACT

Two studies of adult volunteers were performed to determine whether prior enteropathogenic
Escherichia coli
(EPEC) infection confers protective immunity against rechallenge. In the first study, a naive control group and volunteers who had previously ingested an O55:H6 strain were fed an O127:H6 strain. In the second study, a control group and volunteers who had previously ingested either the O127:H6 strain or an isogenic
eae
deletion mutant of that strain were challenged with the homologous wild-type strain. There was no significant effect of prior infection on the incidence of diarrhea in either study. However, in the homologous-rechallenge study, disease was significantly milder in the group previously challenged with the wild-type strain. Disease severity was inversely correlated with the level of prechallenge serum immunoglobulin G against the O127 lipopolysaccharide. These studies indicate that prior EPEC infection can reduce disease severity upon homologous challenge. Further studies may require the development of new model systems.
Saccharomyces cerevisiae-Secreted Fusion Proteins Pfs25 and Pfs28 Elicit PotentPlasmodium falciparumTransmission-Blocking Antibodies in Mice
Authors: Gozar Mary Margaret G. , Price Virginia L. , Kaslow David C. 
Published: December 2019

ABSTRACTTransmission-blocking vaccines based on sexual-stage surface antigens ofPlasmodium falciparummay assist in the control of this lethal form of human malaria. Two vaccine candidates, Pfs25 and Pfs28, were produced as single recombinant fusion proteins. The 39-kDa chimeric proteins, having a C-terminal His6tag, were secreted bySaccharomyces cerevisiae, using the prepro-α-factor leader sequence. Pfs25-28 fusion proteins were significantly more potent than either Pfs25 or Pfs28 alone in eliciting antibodies in mice that blocked oocyst development inAnopheles freebornimosquitoes: complete inhibition of oocyst development in the mosquito midgut was achieved with fewer vaccinations, at a lower dose, and for a longer duration than with either Pfs25 or Pfs28 alone. Increased antigen-specific immunoglobulin G titers and highly significant lymphoproliferative stimulation by Pfs28-containing antigens suggest the presence of an immunodominant helper T-cell epitope in the Pfs28 portion of the fusion proteins. This epitope may be responsible for the enhanced humoral response to both Pfs25 and Pfs28 antigens. Protein production of the fusion protein was improved 12-fold by converting Pfs28 codons to yeast-preferred codons (TBV28), using a modifiedADH2promoter and incorporating a (Glu-Ala)2repeat after the Kex2 cleavage site.
Role of
Fusobacterium nucleatum
and Coaggregation in Anaerobe Survival in Planktonic and Biofilm Oral Microbial Communities during Aeration
Authors: Bradshaw David J. , Marsh Philip D. , Watson G. Keith , Allison Clive 
Published: December 2019

ABSTRACT

Coaggregation is a well-characterized phenomenon by which specific pairs of oral bacteria interact physically. The aim of this study was to examine the patterns of coaggregation between obligately anaerobic and oxygen-tolerant species that coexist in a model oral microbial community. Obligate anaerobes other than
Fusobacterium nucleatum
coaggregated only poorly with oxygen-tolerant species. In contrast,
F. nucleatum
was able to coaggregate not only with both oxygen-tolerant and other obligately anaerobic species but also with otherwise-noncoaggregating obligate anaerobe–oxygen-tolerant species pairs. The effects of the presence or absence of
F. nucleatum
on anaerobe survival in both the biofilm and planktonic phases of a complex community of oral bacteria grown in an aerated (gas phase, 200 ml of 5% CO
2
in air · min
−1
) chemostat system were then investigated. In the presence of
F. nucleatum
, anaerobes persisted in high numbers (>10
7
· ml
−1
in the planktonic phase and >10
7
· cm
−2
in 4-day biofilms). In an equivalent culture in the absence of
F. nucleatum
, the numbers of black-pigmented anaerobes (
Porphyromonas gingivalis
and
Prevotella nigrescens
) were significantly reduced (
P
≤ 0.001) in both the planktonic phase and in 4-day biofilms, while the numbers of facultatively anaerobic bacteria increased in these communities. Coaggregation-mediated interactions between
F. nucleatum
and other species facilitated the survival of obligate anaerobes in aerated environments.
An Ex Vivo Study of T Lymphocytes Recovered from the Lungs of I/St Mice Infected with and Susceptible toMycobacterium tuberculosis
Authors: Lyadova Irina , Yeremeev Vladimir , Majorov Konstantin , Nikonenko Boris , Khaidukov Sergei , Kondratieva Tatiana , Kobets Natalia , Apt Alexander 
Published: December 2019

ABSTRACTI/St mice, previously characterized as susceptible toMycobacterium tuberculosisH37Rv, were given 103or 105CFU intravenously. At two time points postinoculation, the cell suspensions that resulted from enzymatic digestion of lungs were enumerated and further characterized phenotypically and functionally. Regarding the T-cell populations recovered at 2 and 5 weeks postinfection, two main results were obtained: (i) the population of CD44−CD45RB+cells disappeared within 2 weeks postinfection, while the number of CD44+CD45RB−/lowcells slowly increased between weeks 2 and 5; (ii) when cocultured with irradiated syngeneic splenocytes, these lung T cells proliferated in the presence of H37Rv sonicate. Using H37Rv sonicate and irradiated syngeneic splenocytes to reactivate lung T cells, we selected five CD3+CD4+CD8−T-cell clones. In addition to the H37Rv sonicate, the five clones react to both a short-term culture filtrate and an affinity-purified 15- to 18-kDa mycobacterial molecule as assessed by the proliferative assay. However, there was a clear difference between T-cell clones with respect to cytokine (gamma interferon [IFN-γ] and interleukin-4 [IL-4] and IL-10) profiles: besides one Th1-like (IFN-γ+IL-4−) clone and one Th0-like (IFN-γ+IL-4+IL-10+) clone, three clones produced predominantly IL-10, with only marginal or no IL-4 and IFN-γ responses. Inhibition of mycobacterial growth by macrophages in the presence of T cells was studied in a coculture in vitro system. It was found that the capacity to enhance antimycobacterial activity of macrophages fully correlated with INF-γ production by individual T-cell clones following genetically restricted recognition of infected macrophages. The possible functional significance of cytokine diversity among T-cell clones is discussed.
Organ-Dependent Variation of Capsule Thickness inCryptococcus neoformansduring Experimental Murine Infection
Authors: Rivera Johanna , Feldmesser Marta , Cammer Michael , Casadevall Arturo 
Published: December 2019

ABSTRACTIn studies of murine infection, the capsule thickness ofCryptococcus neoformansvaried depending on the organ. The relative order of thickness was as follows: lung > brain > in vitro isolates. The differences in capsule thickness suggest that there are organ-related differences in the expression of genes responsible for capsule thickness.
Helicobacter pylori
Containing Only Cytoplasmic Urease Is Susceptible to Acid
Authors: Krishnamurthy Partha , Parlow Mary , Zitzer Jason B. , Vakil Nimish B. , Mobley Harry L. T. , Levy Marilyn , Phadnis Suhas H. , Dunn Bruce E. 
Published: December 2019

ABSTRACT

Helicobacter pylori
, an important etiologic agent in a variety of gastroduodenal diseases, produces large amounts of urease as an essential colonization factor. We have demonstrated previously that urease is located within the cytoplasm and on the surface of
H. pylori
both in vivo and in stationary-phase culture. The purpose of the present study was to assess the relative contributions of cytoplasmic and surface-localized urease to the ability of
H. pylori
to survive exposure to acid in the presence of urea. Toward this end, we compared the acid resistance in vitro of
H. pylori
cells which possessed only cytoplasmic urease to that of bacteria which possessed both cytoplasmic and surface-localized or extracellular urease. Bacteria with only cytoplasmic urease activity were generated by using freshly subcultured bacteria or by treating repeatedly subcultured
H. pylori
with flurofamide (1 μM), a potent, but poorly diffusible urease inhibitor.
H. pylori
with cytoplasmic and surface-located urease activity survived in an acid environment when 5 mM urea was present. In contrast,
H. pylori
with only cytoplasmic urease shows significantly reduced survival when exposed to acid in the presence of 5 mM urea. Similarly,
Escherichia coli
SE5000 expressing
H. pylori
urease and the Ni
2+
transport protein NixA, which expresses cytoplasmic urease activity at levels similar to those in wild-type
H. pylori
, survived minimally when exposed to acid in the presence of 5 to 50 mM urea. We conclude that cytoplasmic urease activity alone is not sufficient (although cytoplasmic urease activity is likely to be necessary) to allow survival of
H. pylori
in acid; the activity of surface-localized urease is essential for resistance of
H. pylori
to acid under the assay conditions used. Therefore, the mechanism whereby urease becomes associated with the surface of
H. pylori
, which involves release of the enzyme from bacteria due to autolysis followed by adsorption of the enzyme to the surface of intact bacteria (“altruistic autolysis”), is essential for survival of
H. pylori
in an acid environment. The ability of
H. pylori
to survive exposure to low pH is likely to depend on a combination of both cytoplasmic and surface-associated urease activities.
Helicobacter hepaticusTriggers Colitis in Specific-Pathogen-Free Interleukin-10 (IL-10)-Deficient Mice through an IL-12- and Gamma Interferon-Dependent Mechanism
Authors: Kullberg Marika C. , Ward Jerrold M. , Gorelick Peter L. , Caspar Patricia , Hieny Sara , Cheever Allen , Jankovic Dragana , Sher Alan 
Published: December 2019

ABSTRACTMice rendered deficient in interleukin-10 (IL-10) by gene targeting (IL-10−/−mice) develop chronic enterocolitis resembling human inflammatory bowel disease (IBD) when maintained in conventional animal facilities. However, they display a minimal and delayed intestinal inflammatory response when reared under specific-pathogen-free (SPF) conditions, suggesting the involvement of a microbial component in pathogenesis. We show here that experimental infection with a single bacterial agent,Helicobacter hepaticus, induces chronic colitis in SPF-reared IL-10−/−mice and that the disease is accompanied by a type 1 cytokine response (gamma interferon [IFN-γ], tumor necrosis factor alpha, and nitric oxide) detected by restimulation of spleen and mesenteric lymph node cells with a solubleH. hepaticusantigen (Ag) preparation. In contrast, wild-type (WT) animals infected with the same bacteria did not develop disease and produced IL-10 as the dominant cytokine in response toHelicobacterAg. StrongH. hepaticus-reactive antibody responses as measured by Ag-specific total immunoglobulin G (IgG), IgG1, IgG2a, IgG2b, IgG3, and IgA were observed in both WT and IL-10−/−mice. In vivo neutralization of IFN-γ or IL-12 resulted in a significant reduction of intestinal inflammation inH. hepaticus-infected IL-10−/−mice, suggesting an important role for these cytokines in the development of colitis in the model. Taken together, these microbial reconstitution experiments formally establish that a defined bacterial agent can serve as the immunological target in the development of large bowel inflammation in IL-10−/−mice and argue that in nonimmunocompromised hosts IL-10 stimulated in response to intestinal flora is important in preventing IBD.
Minimum Chemical Requirements for Adhesin Activity of the Acid-Stable Part of
Candida albicans
Cell Wall Phosphomannoprotein Complex
Authors: Kanbe Toshio , Cutler Jim E. 
Published: December 2019

ABSTRACT

This study was conducted to define adhesive characteristics of the acid-stable moiety of the
Candida albicans
phosphomannoprotein complex (PMPC) on adherence of this fungus to marginal zone macrophages of the mouse spleen. Complete digestion of the acid-stable moiety (Fr.IIS) of the
C. albicans
PMPC with an α-mannosidase or hydrolysis with 0.6 N sulfuric acid destroyed adhesin activity, as determined by the inability of the soluble digests to inhibit yeast cell adherence to the splenic marginal zone. Fr.IIS adhesin activity was decreased following digestion with an α-1,2-specific mannosidase. Oligomannosyls consisting of one to six mannose units, which were isolated from the acid-stable part of the PMPC, did not inhibit yeast cell binding and thus do not function alone as adhesin sites in the PMPC. To gain more insight into the minimum requirements for adhesin activity, PMPCs were isolated from a
Saccharomyces cerevisiae
wild-type strain and from mutant strains
mnn
1,
mnn
2, and
mnn
4; the PMPCs were designated scwt/Fr.II, scmn1/Fr.II, scmn2/Fr.II, and scmn4/Fr.II, respectively.
S. cerevisiae
scmn2/Fr.II lacks oligomannosyl side chain branches from the outer core mannan, and scmn2/Fr.II was the only PMPC without adhesin activity.
S. cerevisiae
scwt/Fr.II, scmn1/Fr.II, and scmn4/Fr.II showed adhesin activities less than that of
C. albicans
Fr.II. These three
S. cerevisiae
PMPCs are generally similar to Fr.IIS, except that the
S. cerevisiae
structure has fewer and shorter side chains. Immunofluorescence microscopy show that the acid-stable part of the PMPC is displayed homogeneously on the
C. albicans
yeast cell surface, which would be expected for a surface adhesin. Our results indicate that both the mannan core and the oligomannosyl side chains are responsible for the adhesin activity of the acid-stable part of the PMPC.
Role of NK Cells in Early Host Response to Chlamydial Genital Infection
Authors: Tseng Chien-Te Kent , Rank Roger G. 
Published: December 2019

ABSTRACTThe cell-mediated immune response has been documented to be the major protective immune mechanism in mice infected genitally with the agent of mouse pneumonitis (MoPn), a biovar ofChlamydia trachomatis. Moreover, there is strong evidence to indicate that gamma interferon (IFN-γ) is a major effector mechanism of the cell-mediated immune response. Previous studies from this laboratory have also reported that the dominant cell population in the genital tract is the CD4 Th1 population. When experiments were performed by the enzyme-linked immunospot assay, high numbers of cells producing IFN-γ were found in the genital tract, concomitant with resolution of the infection; however, in addition, an increase in IFN-γ-producing cells which were CD4−was seen early in the infection. Since natural killer (NK) cells produce IFN-γ and have been found to participate in the early responses in other infections, we hypothesized that NK cells are responsible for early IFN-γ production in the murine chlamydial model. NK cells were quantified by the standard YAC-1 cytotoxicity assay and were found to appear in the genital tract as early as 12 h after intravaginal infection with MoPn. The cells were confirmed to be NK cells by abrogation of YAC-1 cell cytotoxicity by treatment in vitro and in vivo with anti-asialo-GM1. The early IFN-γ response could also be depleted by treatment with anti-asialo-GM1, indicating that NK cells were responsible for the production of this cytokine. Of interest was our observation that depletion of NK cells also exacerbated the course of infection in the mice and elicited a Th2 response, as indicated by a marked increase in immunoglobulin G1 antibody. Thus, these data demonstrate that NK cells are not only responsible for the production of IFN-γ early in the course of chlamydial genital tract infection but are also, via IFN-γ, a significant factor in the development of the Th1 CD4 response and in the control of the infection.
Complementary Recognition of Alternative Pathway Activators by Decay-Accelerating Factor and Factor H
Authors: Kraus Damian , Medof M. Edward , Mold Carolyn 
Published: December 2019

ABSTRACTThe alternative complement pathway (ACP) functions as a surveillance mechanism by which microorganisms are opsonized with C3b in the absence of specific antibodies. The effectiveness of the ACP relies on its ability to distinguish self from non-self. This recognition function is mediated by C3 regulatory proteins including serum factor H, membrane cofactor protein (MCP), and membrane decay-accelerating factor (DAF). H activity against bound C3b can be increased by host components such as sialic acid and decreased by microbial polysaccharides. DAF and MCP may also recognize cell surface changes such as the presence of viral glycoproteins, since some virus-infected and tumor cells activate the ACP. In the present study, liposomes containing wild-type and mutantSalmonella minnesotalipopolysaccharide (LPS) were tested for ACP activation in serum. LPS-containing liposomes with bound C3b were then tested for their susceptibility to C3 convertase regulation by H and membrane DAF and for the sensitivity of their bound C3b to the cofactor activity of H. The results indicate that while the shortest mutant, Re595 LPS, did not induce ACP activation, R7 LPS containing an additional disaccharide did. This activation was poorly regulated by DAF but was inhibited by H. The regulatory activity of H for liposome-bound C3b, however, decreased when LPS of greater polysaccharide size was present in the membrane. In contrast the ACP activation induced by the phospholipid phosphatidylethanolamine was effectively inhibited by DAF but only poorly inhibited by H.
The Spirochete
Borrelia crocidurae
Causes Erythrocyte Rosetting during Relapsing Fever
Authors: Burman Nils , Shamaei-Tousi Alireza , Bergström Sven 
Published: December 2019

ABSTRACT

Several species of the genus
Borrelia
exhibit antigenic variation of variable major proteins on their surface during relapsing fever. We have investigated the African relapsing fever species
Borrelia crocidurae
during infections in mice and compared it with the thoroughly studied North American species
Borrelia hermsii
. A major difference between the two species is that
B. crocidurae
can bind and become completely covered with erythrocytes. In addition,
B. crocidurae
causes a prolonged spirochetemia which coincides with a delayed appearance of antiborrelial antibodies. We show that the antibody response against an unrelated antigen is not delayed and that antibiotic treatment, which dissociates rosettes and inhibits the spirochetes, also leads to an early antibody response. Taken together, the erythrocyte aggregation and prolonged spirochetemia hint at a new mode of immune evasion where erythrocyte-covered spirochetes may avoid contact with the phagocytic cells and B cells of the immune system, thereby delaying the onset of a specific immune response.
Expression and Purification of the Recombinant Lethal Factor of
Bacillus anthracis
Authors: Gupta Pankaj , Batra Smriti , Chopra Arun P. , Singh Yogendra , Bhatnagar Rakesh 
Published: December 2019

ABSTRACT

The structural gene for the 90-kDa lethal factor (LF) isolated from
Bacillus anthracis
was expressed as a fusion protein with six histidine residues in
Escherichia coli
. Expression of LF in
E. coli
under the transcriptional regulation of the T5 promoter yielded a soluble cytosolic protein with an apparent molecular mass of 90 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Recombinant LF reacted with anti-LF antibodies. The protein was purified to homogeneity by nickel nitrilotriacetic acid affinity chromatography and gel filtration on a Sephacryl S-200 column followed by anion exchange on a fast-performance liquid chromatograph with a Resource-Q column. The yield of purified LF from this procedure was 1.5 mg/liter. In solution, trypsin cleaved protective antigen bound to native and recombinant LF with comparable affinities. In macrophage lysis assays, native and recombinant LF exhibited identical potencies. The results suggest that large amounts of biologically active LF can be purified by this procedure.