bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proteolytic Processing of the
Cryptosporidium
Glycoprotein gp40/15 by Human Furin and by a Parasite-Derived Furin-Like Protease Activity
Authors: Wanyiri Jane W. , O'Connor Roberta , Allison Geneve , Kim Kami , Kane Anne , Qiu Jiazhou , Plaut Andrew G. , Ward Honorine D. 
Published: December 2006

ABSTRACT

The apicomplexan parasite
Cryptosporidium
causes diarrheal disease worldwide. Proteolytic processing of proteins plays a significant role in host cell invasion by apicomplexan parasites. In previous studies, we described gp40/15, a
Cryptosporidium
sp. glycoprotein that is proteolytically cleaved to yield two surface glycopeptides (gp40 and gp15), which are implicated in mediating infection of host cells. In the present study, we showed that biosynthetically labeled gp40/15 is processed in
Cryptosporidium parvum
-infected HCT-8 cells. We identified a putative furin cleavage site RSRR↓ in the deduced amino acid sequence of gp40/15 from
C. parvum
and from all
Cryptosporidium hominis
subtypes except subtype 1e. Both human furin and a protease activity present in a
C. parvum
lysate cleaved recombinant
C. parvum
gp40/15 protein into 2 peptides, identified as gp40 and gp15 by size and by immunoreactivity with specific antibodies.
C. hominis
gp40/15 subtype 1e, in which the RSRR sequence is replaced by ISKR, has an alternative furin cleavage site (KSISKR↓) and was also cleaved by both furin and the
C. parvum
lysate. Site-directed mutagenesis of the
C. parvum
RSRR sequence to ASRR resulted in inhibition of cleavage by furin and the
C. parvum
lysate. Cleavage of recombinant gp40/15 and a synthetic furin substrate by the
C. parvum
lysate was inhibited by serine protease inhibitors, by the specific furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (Dec-RVKR-cmk), and by calcium chelators, suggesting that the parasite expresses a Ca
2+
dependent, furin-like protease activity. The furin inhibitor Dec-RVKR-cmk decreased
C. parvum
infection of HCT-8 cells, suggesting that a furin-like protease activity may be involved in mediating host-parasite interactions.
A Bile Salt Hydrolase of
Brucella abortus
Contributes to the Establishment of a Successful Infection through the Oral Route in Mice
Authors: Delpino M. Victoria , Marchesini María I. , Estein Silvia M. , Comerci Diego J. , Cassataro Juliana , Fossati Carlos A. , Baldi Pablo C. 
Published: December 2006

ABSTRACT

Choloylglycine hydrolase (CGH), a bile salt hydrolase, has been annotated in all the available genomes of
Brucella
species. We obtained the
Brucella
CGH in recombinant form and demonstrated in vitro its capacity to cleave glycocholate into glycine and cholate.
Brucella abortus
2308 (wild type) and its isogenic Δ
cgh
deletion mutant exhibited similar growth rates in tryptic soy broth in the absence of bile. In contrast, the growth of the Δ
cgh
mutant was notably impaired by both 5% and 10% bile. The bile resistance of the complemented mutant was similar to that of the wild-type strain. In mice infected through the intragastric or the intraperitoneal route, splenic infection was significantly lower at 10 and 20 days postinfection in animals infected with the Δ
cgh
mutant than in those infected with the wild-type strain. For both routes, no differences in spleen CFU were found between animals infected with the wild-type strain and those infected with the complemented mutant. Mice immunized intragastrically with recombinant CGH mixed with cholera toxin (CGH+CT) developed a specific mucosal humoral (immunoglobulin G [IgG] and IgA) and cellular (interleukin-2) immune responses. Fifteen days after challenge by the same route with live
B. abortus
2308 cells, splenic CFU counts were 10-fold lower in mice immunized with CGH+CT than in mice immunized with CT or phosphate-buffered saline. This study shows that CGH confers on
Brucella
the ability to resist the antimicrobial action of bile salts. The results also suggest that CGH may contribute to the ability of
Brucella
to infect the host through the oral route.
Analysis ofBartonellaAdhesin A Expression Reveals Differences between VariousB. henselaeStrains
Authors: Riess Tanja , Raddatz Günter , Linke Dirk , Schäfer Andrea , Kempf Volkhard A. J. 
Published: December 2006

ABSTRACTBartonella henselaecauses cat scratch disease and the vasculoproliferative disorders bacillary angiomatosis and peliosis hepatis in humans. One of the best known pathogenicity factors ofB. henselaeisBartonellaadhesin A (BadA), which is modularly constructed, consisting of head, neck/stalk, and membrane anchor domains. BadA is important for the adhesion ofB. henselaeto extracellular-matrix proteins and endothelial cells (ECs). In this study, we analyzed differentB. henselaestrains for BadA expression, autoagglutination, fibronectin (Fn) binding, and adhesion to ECs. We found that theB. henselaestrains Marseille, ATCC 49882, Freiburg 96BK3 (FR96BK3), FR96BK38, and G-5436 express BadA. Remarkably, BadA expression was lacking in aB. henselaeATCC 49882 variant, in strains ATCC 49793 and Berlin-1, and in the majority of bacteria of strain Berlin-2. Adherence ofB. henselaeto ECs and Fn reliably correlated with BadA expression.badAwas present in all tested strains, although the length of the gene varied significantly due to length variations of the stalk region. Sequencing of the promoter, head, and membrane anchor regions revealed only minor differences that did not correlate with BadA expression, apart from strain Berlin-1, in which a 1-bp deletion led to a frameshift in the head region of BadA. Our data suggest that, apart from the identified genetic modifications (frameshift deletion and recombination), other so-far-unknown regulatory mechanisms influence BadA expression. Because of variations between and within differentB. henselaeisolates, BadA expression should be analyzed before performing infection experiments withB. henselae.
Compartmentalization of the Broad-Range Phospholipase C Activity to the Spreading Vacuole Is Critical forListeria monocytogenesVirulence
Authors: Yeung P. S. Marie , Na Yoojin , Kreuder Amanda J. , Marquis Hélène 
Published: December 2006

ABSTRACTListeria monocytogenesis a bacterial pathogen that multiplies in the cytosol of host cells and spreads directly from cell to cell by using an actin-based mechanism of motility. The broad-range phospholipase C (PC-PLC) ofL. monocytogenescontributes to bacterial escape from vacuoles formed upon cell-to-cell spread. PC-PLC is made as an inactive proenzyme whose activation requires cleavage of an N-terminal propeptide. During infection, PC-PLC is activated specifically in acidified vacuoles. To assess the importance of compartmentalizing PC-PLC activity during infection, we created a mutant that makes constitutively active PC-PLC (theplcBΔpro mutant). Results from intracellular growth and cell-to-cell spread assays showed that theplcBΔpro mutant was sensitive to gentamicin, suggesting that unregulated PC-PLC activity causes damage to host cell membranes. This was confirmed by the observation of a twofold increase in staining of live infected cells by a non-membrane-permeant DNA fluorescent dye. However, membrane damage was not sufficient to cause cell lysis and was dependent on bacterial cell-to-cell spread, suggesting that damage was localized to bacterium-containing filopodia. Using an in vivo competitive infection assay, we observed that theplcBΔpro mutant was outcompeted up to 200-fold by the wild-type strain in BALB/c mice. Virulence attenuation was greater when mice were infected orally than when they were infected intravenously, presumably because theplcBΔpro mutant was initially outcompeted in the intestines, reducing the number of mutant bacteria reaching the liver and spleen. Together, these results emphasize the importance forL. monocytogenesvirulence of compartmentalizing the activity of PC-PLC during infection.
Role of Toll-Like Receptor 9 in
Legionella pneumophila
-Induced Interleukin-12 p40 Production in Bone Marrow-Derived Dendritic Cells and Macrophages from Permissive and Nonpermissive Mice
Authors: Newton Cathy A. , Perkins Izabella , Widen Raymond H. , Friedman Herman , Klein Thomas W. 
Published: December 2006

ABSTRACT

The progression of
Legionella pneumophila
infection in macrophages is controlled by the
Lgn1
gene locus, which expresses the nonpermissive phenotype in cells from BALB/c mice but the permissive phenotype in cells from A/J mice. Activation of dendritic cells and macrophages by
L. pneumophila
is mediated by the pathogen recognition receptor Toll-like receptor 2 (TLR2); furthermore,
Legionella
induces innate and adaptive immune cytokines by the MyD88-dependent pathway. TLR9 is coupled to MyD88 and mediates the production of interleukin-12 (IL-12) in dendritic cells infected with other facultatively intracellular pathogens. In the current study,
L. pneumophila
growth in dendritic cells from BALB/c and A/J mice was examined along with the role of TLR9 in the induction of IL-12 in these cells. Dendritic cells from both strains were nonpermissive for
L. pneumophila
intracellular growth, suggesting that the products of the
Lgn1
gene locus that control intracellular growth in macrophages do not control the growth of
Legionella
in dendritic cells. In addition, chloroquine treatment suppressed IL-12 p40 production in response to
Legionella
treatment in dendritic cells and macrophages from BALB/c and A/J mice. Furthermore, the TLR9 inhibitor ODN2088 suppressed the
Legionella
-induced IL-12 production in dendritic cells from both mouse strains. These results suggest that
L. pneumophila
is similar to other intracellular bacteria in that it stimulates the production of immune-transitioning cytokines, such as IL-12, through activation of TLR9 and that this receptor provides a common mechanism for sensing these types of microbes and inducing innate and adaptive immunity.
Role of Complement in Defense of the Middle Ear Revealed by Restoring the Virulence of NontypeableHaemophilus influenzae siaBMutants
Authors: Figueira Marisol A. , Ram Sanjay , Goldstein Richard , Hood Derek W. , Moxon E. Richard , Pelton Stephen I. 
Published: December 2006

ABSTRACTNontypeable (NT)Haemophilus influenzaeis an important cause of otitis media in children. We have shown previously that NTH. influenzaemutants defective in their ability to sialylate lipopolysaccharide (LPS), calledsiaBmutants, show attenuated virulence in a chinchilla model of experimental otitis media (EOM). We show that complement is a key arm of host innate immunity against NTH. influenzae-induced EOM. Depleting complement in chinchillas by use of cobra venom factor (CoVF) rendered two otherwise avirulentsiaBmutants fully virulent and able to cause EOM with severity similar to that of wild-type strains. Clearance of infection caused bysiaBmutants in CoVF-treated animals coincided with reappearance of C3. Wild-type strains were more resistant to direct complement-mediated killing than theirsiaBmutants. The serum-resistant strain bound less C3 and C4 than the serum-sensitive strain. Neither NTH. influenzaestrain tested bound factor H (alternative complement pathway regulator). Selective activation of the alternative pathway resulted in more C3 binding tosiaBmutants. LPS sialylation had a more profound impact on the amount of alternative-pathway-mediated C3 binding (∼5-fold decrease in fluorescence) when LPS was the main C3 target, as occurred on the more serum-resistant strain. In contrast, only an ∼1.5-fold decrease in fluorescence intensity of C3 binding was seen with the serum-sensitive strain, where surface proteins predominantly bound C3. Differences in binding sites for C3 and C4 may account for variations in serum resistance between NTH. influenzaestrains, which in turn may impact their virulence. These data demonstrate a central role for complement in innate immune defenses against NTH. influenzaeinfections and specifically EOM.
Development of a Vaccine against Invasive Pneumococcal Disease Based on Combinations of Virulence Proteins of
Streptococcus pneumoniae
Authors: Ogunniyi Abiodun D. , Grabowicz Marcin , Briles David E. , Cook Jan , Paton James C. 
Published: December 2006

ABSTRACT
Current global efforts are focused on exploring alternative pneumococcal vaccine strategies, aimed at addressing the shortcomings of existing formulations, without compromising efficacy. One such strategy involves the use of one or more pneumococcal protein antigens common to all serotypes, to provide cheap, non-serotype-dependent protection. In this study, we evaluated the protective efficacy of immunization of mice with PdB (a pneumolysin toxoid), PspA, PspC (CbpA), PhtB, and PhtE in an invasive-disease model. The antigens were administered in alum adjuvant, either alone or in various combinations. Protection against intraperitoneal challenge with virulent type 2 and 6A strains was assessed in two murine strains. Our findings show that in some situations, different individual proteins gave the best (and worst) protection. However, in many cases, a synergistic/additive effect was seen by using multiple proteins even where the individual proteins showed little value by themselves. For instance, the median survival times for mice immunized with combinations of PdB and PspA, PdB and PspC, or PspA and PspC were significantly longer than those for mice immunized with any of the single antigens. To date, the combination of PdB, PspA, and PspC offers the best protection.
Cerebrospinal Fluid-Infiltrating CD4+T Cells RecognizeBorrelia burgdorferiLysine-Enriched Protein Domains and Central Nervous System Autoantigens in Early Lyme Encephalitis
Authors: Lünemann Jan D. , Gelderblom Harald , Sospedra Mireia , Quandt Jacqueline A. , Pinilla Clemencia , Marques Adriana , Martin Roland 
Published: December 2006

ABSTRACTNeurological manifestations of Lyme disease are usually accompanied by inflammatory changes in the cerebrospinal fluid (CSF) and the recruitment of activated T cells into the CSF compartment. In order to characterize the phenotype and identify target antigens of CSF-infiltrating T cells in early neuroborreliosis with central nervous system (CNS) involvement, we combined T-cell cloning, functional testing of T-cell responses with positional scanning synthetic combinatorial peptide libraries, and biometric data analysis. We demonstrate that CD4+gamma interferon-producing T cells specifically responding toBorrelia burgdorferilysate were present in the CSF of a patient with acute Lyme encephalitis. Some T-cell clones recognized previously uncharacterizedB. burgdorferiepitopes which show a specific enrichment for lysine, such as the heat shock-induced chaperone HSP90. Degenerate T-cell recognition that included T-cell responses to borrelia-specific and CNS-specific autoantigens derived from the myelin protein 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) could be demonstrated for one representative clone. Our results show that spirochetal antigen-specific and Th1-polarized CD4+lymphocytes infiltrate the CSF during monophasic CNS symptoms of Lyme disease and demonstrate that cross-recognition of CNS antigens byB. burgdorferi-specific T cells is not restricted to chronic and treatment-resistant manifestations.
Quantitative Analysis oftprGene Expression inTreponema pallidumIsolates: Differences among Isolates and Correlation with T-Cell Responsiveness in Experimental Syphilis
Authors: Giacani Lorenzo , Molini Barbara , Godornes Charmie , Barrett Lynn , Van Voorhis Wesley , Centurion-Lara Arturo , Lukehart Sheila A. 
Published: December 2006

ABSTRACTTranscriptional analysis of thetprgenes inTreponema pallidumsubsp.pallidum(referred to here as simplyT. pallidum) has been limited to date, and yet the expression of members of this gene family is likely relevant to the pathogenesis of syphilis. Recently, immunological studies and semiquantitative mRNA analysis led to the hypothesis of the modulation oftprgene transcription during infection and suggested that various strains ofT. pallidummight differentially express these genes. In this study we developed a real-time amplification assay to quantify thetprmRNAs with respect to the 47-kDa lipoprotein message and to compare transcript levels among four different strains ofT. pallidum. In addition, we analyzed the lymphocyte responsiveness pattern toward the Tpr antigens in late experimental syphilis to identifytprgenes that had been expressed during the course of infection. The T-cell response has been implicated in clearance of treponemes from early lesions, and some of the Tprs were identified as strong targets of the cellular immune response. We show that message for many of thetprgenes can be detected in treponemes harvested at the peak of early infection. Interestingly,tprKseems to be preferentially expressed in almost every strain, and it is uniformly the target of the strongest cellular immune response. These studies demonstrate the differential expression of certaintprgenes among strains ofT. pallidum, and further studies are needed to explore the relationship betweentprgene expression and the clinical course of syphilis in infected individuals.
Immune Response, Ciprofloxacin Activity, and Gender Differences after Human Experimental Challenge by Two Strains of Enterotoxigenic
Escherichia coli
Authors: Coster T. S. , Wolf M. K. , Hall E. R. , Cassels F. J. , Taylor D. N. , Liu C. T. , Trespalacios F. C. , DeLorimier A. , Angleberger D. R. , McQueen C. E. 
Published: December 2006

ABSTRACT

In order to test vaccines against enterotoxigenic
Escherichia coli
(ETEC)-induced diarrhea, challenge models are needed. In this study we compared clinical and immunological responses after North American volunteers were orally challenged by two ETEC strains. Groups of approximately eight volunteers received 10
9
or 10
10
CFU of
E. coli
B7A (LT
+
ST
+
CS6
+
) or 10
8
or 10
9
CFU of
E. coli
H10407 (LT
+
ST
+
CFA/I
+
). About 75% of the volunteers developed diarrhea after challenge with 10
10
CFU B7A or either dose of H10407. B7A had a shorter incubation period than H10407 (
P
= 0.001) and caused milder illness; the mean diarrheal output after H10407 challenge was nearly twice that after B7A challenge (
P
= 0.01). Females had more abdominal complaints, and males had a higher incidence of fever. Ciprofloxacin generally diminished or stopped symptoms and shedding by the second day of antibiotic treatment, but four subjects shed for one to four additional days. The immune responses to colonization factors CS6 and colonization factor antigen I (CFA/I) and to heat-labile toxin (LT) were measured. The responses to CFA/I were the most robust responses; all volunteers who received H10407 had serum immunoglobulin A (IgA) and IgG responses, and all but one volunteer had antibody-secreting cell (ASC) responses. One-half the volunteers who received B7A had an ASC response to CS6, and about one-third had serum IgA or IgG responses. Despite the differences in clinical illness and immune responses to colonization factors, the immune responses to LT were similar in all groups and were intermediate between the CFA/I and CS6 responses. These results provide standards for immune responses after ETEC vaccination.
Protective and Immunochemical Activities of Monoclonal Antibodies Reactive with theBacillus anthracisPolypeptide Capsule
Authors: Kozel Thomas R. , Thorkildson Peter , Brandt Suzanne , Welch William H. , Lovchik Julie A. , AuCoin David P. , Vilai Julpohng , Lyons C. Rick 
Published: December 2006

ABSTRACTBacillus anthracisis surrounded by a polypeptide capsule composed of poly-gamma-d-glutamic acid (γDPGA). In a previous study, we reported that a monoclonal antibody (MAb F26G3) reactive with the capsular polypeptide is protective in a murine model of pulmonary anthrax. The present study examined a library of six MAbs generated from mice immunized with γDPGA. Evaluation of MAb binding to the capsule by a capsular “quellung” type reaction showed a striking diversity in capsular effects. Most MAbs produced a rim type reaction that was characterized by a sharp increase followed directly by a decrease in refractive index at the capsular edge. Some MAbs produced a second capsular reaction well beneath the capsular edge, suggesting complexity in capsular architecture. Binding of MAbs to soluble γDPGA was assessed by a fluorescence perturbation assay in which a change in the MAb intrinsic fluorescence produced by ligand binding was used as a reporter for antigen-antibody interaction. The MAbs differed considerably in the complexity of the binding curves. MAbs producing rim type capsule reactions typically produced the more complex binding isotherms. Finally, the protective activity of the MAbs was compared in a murine model of pulmonary anthrax. One MAb was markedly less protective than the remaining five MAbs. Characteristics of the more protective MAbs included a relatively high affinity, an immunoglobulin G3 isotype, and a complex binding isotherm in the fluorescence perturbation assay. Given the relatively monotonous structure of γDPGA, the results demonstrate a striking diversity in the antigen binding behavior of γDPGA antibodies.
Vβ1
+
Jβ1.1
+
/Vα2
+
Jα49
+
CD4
+
T Cells Mediate Resistance against Infection with
Blastomyces dermatitidis
Authors: Wüthrich Marcel , Filutowicz Hanna I. , Allen Holly L. , Deepe George S. , Klein Bruce S. 
Published: December 2006

ABSTRACT

Immunization with a cell wall/membrane (CW/M) and yeast cytosol extract (YCE) crude antigen from
Blastomyces dermatitidis
confers T-cell-mediated resistance against lethal experimental infection in mice. We isolated and characterized T cells that recognize components of these protective antigens and mediate protection. CD4
+
T-cell clones elicited with CW/M antigen adoptively transferred protective immunity when they expressed a Vα2
+
Jα49
+
/Vβ1
+
Jβ1.1
+
heterodimeric T-cell receptor (TCR) and produced high levels of gamma interferon (IFN-γ). In contrast, Vβ8.1/8.2
+
CD4
+
T-cell clones that were reactive against CW/M and YCE antigens and produced little or no IFN-γ either failed to mediate protection or exacerbated the infection depending on the level of interleukin-5 expression. Thus, the outgrowth of protective T-cell clones against immunodominant antigens of
B. dermatitidis
is biased by a combination of the TCR repertoire and Th1 cytokine production.
Temporal Quorum-Sensing Induction Regulates
Vibrio cholerae
Biofilm Architecture
Authors: Liu Zhi , Stirling Fiona R. , Zhu Jun 
Published: December 2006

ABSTRACT

Vibrio cholerae
, the pathogen that causes cholera, also survives in aqueous reservoirs, probably in the form of biofilms. Quorum sensing negatively regulates
V. cholerae
biofilm formation through HapR, whose expression is induced at a high cell density. In this study, we show that the concentration of the quorum-sensing signal molecule CAI-1 is higher in biofilms than in planktonic cultures. By measuring
hapR
expression and activity, we found that the induction of quorum sensing in biofilm-associated cells occurs earlier. We further demonstrate that the timing of
hapR
expression is crucial for biofilm thickness, biofilm detachment rates, and intestinal colonization efficiency. These results suggest that
V. cholerae
is able to regulate its biofilm architecture by temporal induction of quorum-sensing systems.
Fully Virulent
Bacillus anthracis
Does Not Require the Immunodominant Protein BclA for Pathogenesis
Authors: Bozue J. , Cote C. K. , Moody K. L. , Welkos S. L. 
Published: December 2006

ABSTRACT

The BclA protein is the immunodominant epitope on the surface of
Bacillus anthracis
spores; however, its roles in pathogenesis are unclear. We constructed a BclA deletion mutant (
bclA
) of the fully virulent Ames strain. This derivative retained full virulence in several small-animal models of infection despite the
bclA
deletion.