bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcellular Passage of
Neisseria gonorrhoeae
Involves Pilus Phase Variation
Authors: Ilver Dag , Källström Helena , Normark Staffan , Jonsson Ann-Beth 
Published: December 2019

ABSTRACT

Piliated and nonpiliated
Neisseria gonorrhoeae
organisms were added on top of confluent layers of HEC-1-B cells, each maintained on a microporous Transwell-COL membrane. The bacteria released into the lower chamber were characterized with respect to the following virulence determinants: pili, which mediate adherence to target host cells; PilE, the major pilus subunit protein; and PilC, which is involved in pilus biogenesis and adherence. Even if >99% of the added bacteria of
N. gonorrhoeae
MS11 were piliated, bacteria recovered on the other side of the cell layer were predominantly nonpiliated. The recovered clones still expressed unassembled PilE protein, but 50% had lost PilC production. Nonpiliated gonococci, in which the 5′ end of
pilE
had been deleted, were released in reduced numbers, and piliated
recA
bacteria added to the cell layer were not released at all, at time points when piliated
recA
+
clones were found at high numbers in the lower chamber. Our data indicate that bacteria producing unassembled PilE protein are selected for during passage through an epithelial cell layer. The finding that the
pilE
gene sequence was altered in the transmigrants suggests that pilin sequence variation is involved in the transcellular passage of
N. gonorrhoeae.
Diffusely Adhering
Escherichia coli
Strains Induce Attaching and Effacing Phenotypes and Secrete Homologs of Esp Proteins
Authors: Beinke Christina , Laarmann Sven , Wachter Clemens , Karch Helge , Greune Lilo , Schmidt M. Alexander 
Published: December 2019

ABSTRACT

Recent epidemiological studies indicate that
Escherichia coli
strains which exhibit the diffuse-adherence phenotype (DAEC strains) represent a potential cause of diarrhea in infants. We investigated the interaction of DAEC strains isolated from diarrhea patients in Brazil and in Germany with epithelial cells in tissue culture. The investigated strains were identified as DAEC strains by (i) their attachment pattern, (ii) presence of genes associated with the Dr family of adhesins, and (iii) lack of genetic markers for other diarrhea-associated
E. coli
categories. Several clinical DAEC isolates were shown to secrete similar patterns of proteins into tissue culture medium. Protein secretion was found to be regulated by environmental parameters, namely, medium, temperature, pH, and iron concentration. DAEC strains secreting these proteins induced accumulation of actin and tyrosine-phosphorylated proteins at sites of bacterial attachment, leading to the formation of pedestals and/or extended surface structures. These changes were phenotypically similar to the attaching and effacing (A/E) lesions observed with enteropathogenic and some enterohemorrhagic
E. coli
strains carrying the locus of enterocyte effacement (LEE) pathogenicity island. Proteins homologous to the EspA, EspB, and EspD proteins, necessary for signal transduction events inducing A/E lesions, were identified by sequence analysis and cross-reaction of specific antibodies. However, initially nonadhering strains secreting these proteins induced signal transduction events only after prolonged infection. These results indicate that secretion of the Esp proteins alone is not sufficient for efficient signal transduction. This study further shows that some DAEC strains are likely to contain a homolog(s) of the LEE locus which may contribute to the pathogenic potential of DAEC.
Partial Purification and Characterization of Biological Effects of a Lipid Toxin Produced byMycobacterium ulcerans
Authors: George Kathleen M. , Barker Lucia P. , Welty Diane M. , Small P. L. C. 
Published: December 2019

ABSTRACTOrganisms in the genusMycobacteriumcause a variety of human diseases. One member of the genus,M. ulcerans, causes a necrotizing skin disease called Buruli ulcer. Buruli ulcer is unique among mycobacterial diseases in that the organisms at the site of infection are extracellular and there is little acute inflammatory response. Previous literature reported the presence of a toxin in the culture supernatant ofM. ulceranswhich causes a cytopathic effect on the mouse fibroblast cell line L929 in which the adherent cells round up and detach from the tissue culture plate. Here we report partial purification of a lipid toxin from the culture supernatant ofM. ulceranswhich is capable of causing the cytopathic effect on L929 cells. We also show that this cytopathic effect is a result of cytoskeletal rearrangement. TheM. ulceranstoxin does not cause cell death but instead arrests cells in the G1phase of the cell cycle.
Expression and Characterization of Group AStreptococcusExtracellular Cysteine Protease Recombinant Mutant Proteins and Documentation of Seroconversion during Human Invasive Disease Episodes
Authors: Gubba Siddeswar , Low Donald E. , Musser James M. 
Published: December 2019

ABSTRACTA recent study with isogenic strains constructed by recombinant DNA strategies unambiguously documented that a highly conserved extracellular cysteine protease expressed byStreptococcus pyogenes(group AStreptococcus[GAS]) is a critical virulence factor in a mouse model of invasive disease (S. Lukomski, S. Sreevatsan, C. Amberg, W. Reichardt, M. Woischnik, A. Podbielski, and J. M. Musser, J. Clin. Invest. 99:2574–2580, 1997). To facilitate further investigations of the streptococcal cysteine protease, recombinant proteins composed of a 40-kDa zymogen containing a C192S amino acid substitution that ablates enzymatic activity, a 28-kDa mature protein with the C192S replacement, and a 12-kDa propeptide were purified fromEscherichia colicontaining His tag expression vectors. The recombinant C192S zymogen retained apparently normal structural integrity, as assessed by the ability of purified wild-type streptococcal cysteine protease to process the 40-kDa molecule to the 28-kDa mature form. All three recombinant purified proteins retained immunologic reactivity with polyclonal and monoclonal antibodies. Humans with a diverse range of invasive disease episodes (erysipelas, cellulitis, pneumonia, bacteremia, septic arthritis, streptococcal toxic shock syndrome, and necrotizing fasciitis) caused by six distinct M types of GAS seroconverted to the streptococcal cysteine protease. These results demonstrate that this GAS protein is expressed in vivo during the course of human infections and thereby provide additional evidence that the cysteine protease participates in host-pathogen interactions in some patients.
Mapping of the T-Cell Epitope in the Major 43-Kilodalton Glycoprotein ofParacoccidioides brasiliensisWhich Induces a Th-1 Response Protective against Fungal Infection in BALB/c Mice
Authors: Taborda Carlos P. , Juliano Maria A. , Puccia Rosana , Franco Marcello , Travassos Luiz R. 
Published: December 2019

ABSTRACTThe 43-kDa glycoprotein ofParacoccidioides brasiliensisis the major diagnostic antigen of paracoccidioidomycosis, the prevalent systemic mycosis of Latin America. Apart from eliciting high antibody titers, gp43 is also immunodominant in delayed-type hypersensitivity reactions in infected animals and humans. The cellular immune response in mice to gp43 administered in complete Freund’s adjuvant involves CD4+Th-1 lymphocytes, secreting gamma interferon (IFN-γ) and interleukin 2 (IL-2) but not IL-4 and IL-10. The T-cell epitope of this antigen was mapped to a 15-amino-acid peptide (P10) based on lymphoproliferations with primed cells from three different haplotypes and on a computer-assisted protein analysis. The structural requirements of the T-cell epitope were determined by assaying a series of P10 analogous and truncated peptides. Only 12-mer or longer sequences were active, confirming presentation by major histocompatibility complex II. The HTLAIR inner core of P10 is the essential domain of the epitope, with various flanking regions possible. Immunization of mice with both gp43 and P10 led to vigorous protection against intratracheal challenge by virulentP. brasiliensis, with a >200-fold decrease in lung CFU and halting of dissemination to the spleen and liver. The protective effect of P10 is mainly attributed to an IFN-γ-mediated cellular immune response. Unlike gp43, which induces an antibody response compatible with both Th-1 and Th-2 activation in infected BALB/c mice, P10 does not induce a humoral response. Protection by gp43 and P10 was characterized by a few well-demarcated lung granulomas with numerous nonviable yeast forms or resolved lesions with no detectable fungal cells.
Comparison of Intranasal and Intramuscular Immunization against Human Immunodeficiency Virus Type 1 with a DNA-Monophosphoryl Lipid A Adjuvant Vaccine
Authors: Sasaki Shin , Hamajima Kenji , Fukushima Jun , Ihata Atsushi , Ishii Norihisa , Gorai Itsuo , Hirahara Fumiki , Mohri Hiroshi , Okuda Kenji 
Published: December 2019

ABSTRACTWe compared immune responses to intranasal and intramuscular DNA vaccinations against human immunodeficiency virus type 1 with monophosphoryl lipid A (MPL) used as an adjuvant. Both routes of vaccination resulted in similar levels of cell-mediated immunity, but the intestinal secretory immunoglobulin A response was higher following intranasal immunization than after intramuscular immunization. MPL demonstrated its adjuvanticity in vaccination by both routes.
Transcriptional Regulation of Endothelial Cell Tissue Factor Expression during
Rickettsia rickettsii
Infection: Involvement of the Transcription Factor NF-κB
Authors: Shi Rui-Jin , Simpson-Haidaris Patricia J. , Lerner Norma B. , Marder Victor J. , Silverman David J. , Sporn Lee Ann 
Published: December 2019

ABSTRACT

The vascular endothelial cell (EC) is a primary target of infection with
Rickettsia rickettsii
, the etiologic agent of Rocky Mountain spotted fever. Changes in gene transcription elicited by intracellular infection, including EC expression of the coagulation pathway initiator known as tissue factor (TF), may contribute to the vascular pathology observed during disease. Nuclear run-on analysis of uninfected and infected, cultured human endothelial cells revealed that the rate of TF mRNA transcription is enhanced more than twofold at 3 h following infection, thus coinciding with increased steady-state levels of TF mRNA. TF mRNA remained relatively unstable during infection, with a half-life of 1.6 h. The eukaryotic protein synthesis inhibitor cycloheximide did not block
R. rickettsii
-induced increase in TF mRNA levels and actually resulted in its superinduction, thus revealing that de novo synthesis of host cell protein was not prerequisite to this transcriptional response. Involvement of the transcription factor NF-κB in
R. rickettsii
-induced TF expression was demonstrated by using two unrelated inhibitors of NF-κB activation. The antioxidant pyrrolidinedithiocarbamate and the proteasome inhibitor
N
-tosyl-
l
-phenylalanine chloromethyl ketone blocked expression of TF mRNA and activity during infection. This study demonstrates that
R. rickettsii
infection results in transcriptional activation of the TF gene and that this response involves activation of the transcription factor NF-κB.
Listeria monocytogenesInvasion of Epithelial Cells Requires the MEK-1/ERK-2 Mitogen-Activated Protein Kinase Pathway
Authors: Tang Patrick , Sutherland Claire L. , Gold Michael R. , Finlay B. Brett 
Published: December 2019

ABSTRACTPD98059, a specific inhibitor of MEK-1 mitogen-activated protein (MAP) kinase kinase, blockedListeria monocytogenesinvasion into HeLa epithelial cells. The effects of PD98059 were reversible, as adherent extracellular bacteria were internalized upon removal of the drug. Previously, we reported thatL. monocytogenescould activate ERK-1 and ERK-2 MAP kinases through the action of listeriolysin O (LLO) on the host cell (P. Tang, I. Rosenshine, P. Cossart, and B. B. Finlay, Infect. Immun. 64:2359–2361, 1996). We have now found that two other MAP kinase pathways, those of p38 MAP kinase and c-Jun N-terminal kinase, are also activated by wild-typeL. monocytogenes. Mutants lacking functional LLO (hlymutants) were still invasive but only activated ERK-2 and only activated it at later (90-min) postinfection times. Two inhibitors ofL. monocytogenesinvasion, cytochalasin D, which disrupts actin polymerization, and wortmannin, which blocks phosphatidylinositol (PI) 3-kinase activity, did not block ERK-2 activation by wild-typeL. monocytogenesandhlymutants. However, genistein, an inhibitor of tyrosine kinases, and PD98059 both blocked invasion and decreased ERK-2 activation. These results suggest that MEK-1 and ERK-2 activities are essential forL. monocytogenesinvasion into host epithelial cells. This is the first report to show that a MAP kinase pathway is required for bacterial invasion.
Identification of Virulence-Associated Characteristics in Clinical Isolates of
Yersinia enterocolitica
Lacking Classical Virulence Markers
Authors: Grant Travis , Bennett-Wood Vicki , Robins-Browne Roy M. 
Published: December 2019

ABSTRACT

Yersinia enterocolitica
is an important enteric pathogen which has well-defined virulence determinants that allow the bacteria to become established in their hosts and overcome host defenses. A number of strains obtained from patients with diarrhea, however, lack these genes. Accordingly, the mechanisms by which they cause disease are uncertain. Most of these isolates belong to biotype 1A. Strains of this biotype are also frequently isolated from a variety of nonclinical sources, such as food, soil, water, and healthy animals, and there is evidence that some of these strains are avirulent. In this study we investigated 111 strains of
Y. enterocolitica
biotype 1A, 79 from symptomatic humans and 32 from nonclinical sources, for virulence-associated characteristics. DNA hybridization studies showed that none of the strains carried sequences homologous with pYV, the ∼70-kb
Yersinia
virulence plasmid. Some strains hybridized with DNA probes for one of the following chromosomal virulence-associated genes:
ail
(7.2%),
myfA
(11.7%),
ystA
(0.9%), and
ystB
(85%). In addition, 33 strains (29.7%) produced an enterotoxin that was reactive in infant mice. However, the frequencies of these virulence-associated properties in clinical and nonclinical isolates were similar. Clinical isolates invaded HEp-2 cells and Chinese hamster ovary cells to a significantly greater extent than nonclinical strains (
P
≤ 0.002). In addition, clinical strains colonized the intestinal tracts of perorally inoculated mice for significantly longer periods than nonclinical isolates (
P
≤ 0.01). Light and electron microscopic examination of tissue culture cells incubated with invasive yersiniae revealed that the bacteria invaded selected cells in large numbers but spared others, suggesting that biotype-1A strains of
Y. enterocolitica
may invade cells by a novel mechanism. These results indicate that some clinical isolates of
Y. enterocolitica
which lack classical virulence markers may be able to cause disease via virulence mechanisms which differ from those previously characterized in enteropathogenic
Yersinia
species.
Characterization of a
Chlamydia psittaci
DNA Binding Protein (EUO) Synthesized during the Early and Middle Phases of the Developmental Cycle
Authors: Zhang Li , Douglas Annemarie L. , Hatch Thomas P. 
Published: December 2019

ABSTRACT

The EUO gene (for early upstream open reading frame) of
Chlamydia psittaci
was previously found to be transcribed better at 1 than at 24 h postinfection. We found that the EUO gene encodes a minor protein that is expressed within 1 h of infection of host cells with
C. psittaci
6BC but that protein quantity peaks during the logarithmic growth phase of reticulate bodies (RBs), declines late in the infection (after 20 h) when RBs reorganize into elementary bodies (EBs), and is absent in infectious EBs. EUO protein lacks homology to known proteins but does contain a putative helix-turn-helix motif. We found that recombinant EUO binds to DNA in vitro with a relatively broad specificity. Using the bp −200 to +67 promoter region of the cysteine-rich envelope protein (
crp
) operon as a model, we show that EUO protein preferentially binds to AT-rich sequences and protects
crp
DNA from DNase I from approximately bp −60 to −9. We also found that native EUO protein in extracts of RBs binds to the promoter region of the
crp
operon, demonstrating that the DNA binding property of EUO protein is not an artifact of recombinant methods. Although EUO protein appears to bind to the
crp
operon with high affinity in vitro (

K
d

of about 15 nM), it is not known whether the protein binds the
crp
DNA in vivo.
Defective Nitric Oxide Effector Functions Lead to Extreme Susceptibility ofTrypanosoma cruzi-Infected Mice Deficient in Gamma Interferon Receptor or Inducible Nitric Oxide Synthase
Authors: Hölscher Christoph , Köhler Gabriele , Müller Uwe , Mossmann Horst , Schaub Günter A. , Brombacher Frank 
Published: December 2019

ABSTRACTTrypanosoma cruzi, the causative agent of Chagas’ disease, induces an innate and adaptive host immune response during the acute phase of infection. These responses were analyzed by comparing mouse lines deficient for the gamma interferon (IFN-γ) receptor (IFN-γR−/−) or deficient for inducible nitric oxide synthase (iNOS−/−). Both lines were highly susceptible, with similar and dramatically increased parasite burdens and severe histopathology and were incapable of surviving even very low doses, exhibiting similar mortality kinetics. This pathophysiological correlation has a common cause, since both mutant mouse strains were unable to respond to infection by producing nitric oxide (NO) with the consequence that mutant macrophages had impaired trypanocidal activities. These in vivo and subsequent in vitro studies further demonstrated that an IFN-γ-dependent pathway of iNOS induction is crucial for efficient NO production and mandatory for resisting acute infection withT. cruzi. Despite this defect, both mutant mouse strains had a rather normal proinflammatory cytokine response (interleukin-12 [IL-12], IFN-γ, IL-6), with the exception of an impaired tumor necrosis factor alpha and IL-1α response in IFN-γR−/−mice, demonstrating that only the latter two cytokines are dependent on IFN-γ activation. Moreover, polarization of T cells in type 1 and type 2 T-helper (Th1/Th2) and cytotoxic T (Tc1/Tc2) cells as well asT. cruzi-specific antibody responses were normal in IFN-γR−/−mice, demonstrating that IFN-γ is not necessary for the promotion of T-cell differentiation andT. cruzi-specific antibody responses.
Mouse β-Defensin 1 Is a Salt-Sensitive Antimicrobial Peptide Present in Epithelia of the Lung and Urogenital Tract
Authors: Bals Robert , Goldman Mitchell J. , Wilson James M. 
Published: December 2019

ABSTRACT
One component of host defense at mucosal surfaces appears to be epithelium-derived peptides with antimicrobial activity called defensins. Human β-defensin 1 (hBD-1) represents the first member of the β-defensin family isolated from humans and has been implicated in the pathogenesis of cystic fibrosis. We describe in this report the isolation and characterization of a murine homolog of hBD-1 called mouse β-defensin 1 (mBD-1). The predicted amino acid sequence shows the hallmark features of other known epithelial β-defensins, including the ordered array of six cysteine residues. Analysis of a genomic clone of mBD-1 revealed two exons separated by a 15-kb intron. By use of fluorescence in situ hybridization, the mBD-1 gene was localized at the proximal portion of chromosome 8, the site where mouse α-defensins are found. Lysates from cells transfected with the mBD-1 cDNA showed antibacterial activity against gram-positive and gram-negative bacteria. mBD-1 transcripts were found in kidney, liver, and female reproductive organ tissues. In the airways, mBD-1 is expressed diffusely throughout the epithelial cells of the large proximal airways with less expression in the small distal airways and no expression in alveolar cells. The present study demonstrates that a β-defensin potentially homologous to human β-defensin 1 is present in the respiratory system and other mucosal surfaces in mice.
Serum Complement Sensitivity as a Key Factor in Lyme Disease Ecology
Authors: Kurtenbach Klaus , Sewell Henna-Sisko , Ogden Nick H. , Randolph Sarah E. , Nuttall Patricia A. 
Published: December 2019

ABSTRACTThe sensitivity ofBorrelia burgdorferisensu lato to animal sera was analyzed. Complement-mediated borreliacidal effects were observed with particular combinations of host serum andBorreliagenospecies. The species-specific pattern of viability and/or lysis is highly consistent with the pattern of reservoir competence of hosts forB. burgdorferisensu lato, suggesting a key role of complement in the global ecology of Lyme borreliosis.
Neither Interleukin-6 nor Inducible Nitric Oxide Synthase Is Required for Clearance ofChlamydia trachomatisfrom the Murine Genital Tract Epithelium
Authors: Perry Linda L. , Feilzer Karen , Caldwell Harlan D. 
Published: December 2019

ABSTRACTFemale mice bearing targeted mutations in the interleukin-6 or inducible nitric oxide synthase locus mounted effective immune responses following vaginal infection withChlamydia trachomatis. Chlamydial clearance rates, local Th1 cytokine production, and host antibody responses were similar to those of immunocompetent control mice. Therefore, neither gene product appears to be critical for the resolution of chlamydial infections of the urogenital epithelium.
A Monoclonal Antibody Generated by Antigen Inoculation via Tick Bite Is Reactive to the
Borrelia burgdorferi
Rev Protein, a Member of the 2.9 Gene Family Locus
Authors: Gilmore Robert D. , Mbow M. Lamine 
Published: December 2019

ABSTRACT

Murine monoclonal antibodies directed against proteins of
Borrelia burgdorferi
B31 (low passage) were generated by the administration of antigen via the bite of borrelia-infected ticks. This strategy was employed as a mechanism to create antibodies against antigens presented by the natural route of tick transmission versus those presented by inoculation with cultured borreliae. One of the resultant antibodies reacted with a 17-kDa antigen from cultured
B. burgdorferi
, as seen by immunoblot analysis. This antibody was used to screen a
B. burgdorferi
genomic DNA lambda vector expression library, and an immunoreactive clone was isolated. DNA sequence analysis of this clone, containing a 2.7-kb insert, revealed several open reading frames. These open reading frames were found to be homologs of genes discovered as a multicopy gene family in the 297 strain of
B. burgdorferi
by Porcella et al. (S. F. Porcella, T. G. Popova, D. R. Akins, M. Li, J. D. Radolf, and M. V. Norgard, J. Bacteriol. 178:3293–3307, 1996). By selectively subcloning genes found in this insert into an
Escherichia coli
plasmid expression vector, the observation was made that the
rev
gene product was the protein reactive with the 17-kDa-specific monoclonal antibody. The
rev
gene product was found to be expressed in low-passage, but not in high-passage,
B. burgdorferi
B31. Correspondingly, the
rev
gene was not present in strain B31 genomic DNA from cultures that had been passaged >50 times. Serum samples from Lyme disease patients demonstrated an antibody response against the Rev protein. The generation of an anti-Rev response in Lyme disease patients, and in mice by tick bite inoculation, provides evidence that the Rev protein is expressed and immunogenic during the course of natural transmission and infection.