bluuebunny/crossref_metadata_2025_split huggingface dataset:
The C-Terminal Region of
Bacteroides fragilis
Toxin Is Essential to Its Biological Activity
Authors: Sears Cynthia L. , Buckwold Simy L. , Shin Jai W. , Franco Augusto A. 
Published: September 2006

ABSTRACT

To evaluate the role of the C-terminal region in
Bacteroides fragilis
toxin (BFT) activity, processing, and secretion, sequential C-terminal truncation and point mutations were created by site-directed mutagenesis. Determination of BFT activity on HT29/C1 cells, cleavage of E-cadherin, and the capacity to induce interleukin-8 secretion by wild-type BFT and C-terminal deletion mutants showed that deletion of only 2 amino acid residues at the C terminus significantly reduced BFT biological activity and deletion of eight or more amino acid residues obliterated BFT biologic activity. Western blot and reverse transcription-PCR analyses indicated that BFT mutants lacking seven or fewer amino acid residues in the C-terminal region are processed and expressed similar to wild-type BFT. However, BFT mutants lacking eight or more amino acids at the C terminus are expressed similar to wild-type BFT but are unstable. We concluded that the C terminus of BFT is not tolerant of modest amino acid deletions, suggesting that it is biologically important for BFT activity.
Neutrophils Do Not Mediate the Pathophysiological Sequelae of
Cryptosporidium parvum
Infection in Neonatal Piglets
Authors: Zadrozny Leah M. , Stauffer Stephen H. , Armstrong Martha U. , Jones Samuel L. , Gookin Jody L. 
Published: September 2006

ABSTRACT

Cryptosporidium parvum
is a minimally invasive protozoal pathogen of intestinal epithelium that results in villus atrophy, mucosal lipid peroxidation, diarrhea, and diminished barrier function. Influx of neutrophils is a consistent feature of human and animal cryptosporidiosis, and yet their contribution to the pathological sequelae of infection has not been investigated. Accordingly, we used an established neonatal piglet model of
C. parvum
infection to examine the role of neutrophils in disease pathogenesis by inhibiting their recruitment and activation in vivo using a monoclonal anti-CD18 antibody. Infected piglets were treated daily with anti-CD18 or isotype control immunoglobulin G and euthanized at peak infection, at which time neutrophil infiltrates, lipid peroxidation, severity of infection, and intestinal barrier function were quantified.
C. parvum
infection resulted in a significant increase in mucosal neutrophil myeloperoxidase activity that was prevented by treatment of piglets with anti-CD18 antibody. Neutrophil recruitment was dependent on mucosal superoxide formation (prevented by treatment of infected piglets with superoxide dismutase). Neutrophils did not contribute to peroxynitrite formation or peroxidative injury of
C. parvum
-infected mucosa and had no impact on the severity of epithelial infection, villus atrophy, or diarrhea. The presence of neutrophils in
C. parvum
-infected mucosa was associated with enhanced barrier function that could not be attributed to mucosal elaboration of prostaglandins or stimulation of their synthesis. These studies are the first to demonstrate that neutrophilic inflammation arising in response to infection by a noninvasive epithelial pathogen results in physiologic rather than pathological effects in vivo.
Identification of OmpU of
Vibrio vulnificus
as a Fibronectin-Binding Protein and Its Role in Bacterial Pathogenesis
Authors: Goo Sung Young , Lee Hyun-Ju , Kim Woo Hwang , Han Kyu-Lee , Park Dae-Kyun , Lee Hyun-Jung , Kim Sung Min , Kim Kun-Soo , Lee Kyu-Ho , Park Soon-Jung 
Published: September 2006

ABSTRACT

Vibrio vulnificus
is a pathogenic bacterium that causes gastroenteritis and primary septicemia. To identify factors involved in microbial adherence to the host cells, we investigated bacterial proteins capable of binding to fibronectin, one of the main components comprised of the extracellular matrix of mammalian cells. A protein of ∼35 kDa was purified from the extracts of
V. vulnificus
by its property to bind to immobilized fibronectin. This protein was identified as OmpU, one of the major outer membrane proteins of
V. vulnificus
. In binding assays using immobilized fibronectin, the number of
ompU
mutant cells bound to fibronectin was only 4% of that of wild-type cells bound to fibronectin. In addition, the exogenous addition of antibodies against OmpU resulted in a decreased ability of wild-type
V. vulnificus
to adhere to fibronectin. The
ompU
mutant was also defective in its adherence to RGD tripeptide (5% of the adherence of the wild type to RGD), cytoadherence to HEp-2 cells (7% of the adherence of the wild type to HEp-2), cytotoxicity to cell cultures (39% of the cytotoxicity of the wild type), and mortality in mice (10-fold increase in the 50% lethal dose). The
ompU
mutant complemented with the intact
ompU
gene restored its abilities for adherence to fibronectin, RGD tripeptide, and HEp-2 cells; cytotoxicity to HEp-2 cells; and mouse lethality. This study indicates that OmpU is an important virulence factor involved in the adherence of
V. vulnificus
to the host cells.
Infection withSyphacia obvelata(Pinworm) Induces Protective Th2 Immune Responses and Influences Ovalbumin-Induced Allergic Reactions
Authors: Michels Chesney , Goyal Prem , Nieuwenhuizen Natalie , Brombacher Frank 
Published: September 2006

ABSTRACTInfections with pinworms are common in rodent animal facilities. In this study, we show the consequence of an outbreak in a transgenic barrier facility of infection bySyphacia obvelata, a murine pinworm gastrointestinal nematode. Immune responses were defined in experimental infection studies with BALB/c mice. Infection withS. obvelatainduced a transient Th2-type immune response with elevated interleukin 4 (IL-4), IL-5, and IL-13 cytokine production and parasite-specific immunoglobulin G1 (IgG1). In contrast, BALB/c mice deficient in IL-13, IL-4/13, or the IL-4 receptor alpha chain showed chronic disease, with a >100-fold higher parasite burden, increased gamma interferon production, parasite-specific IgG2b, and a default Th2 response. Interestingly, infected IL-4−/−BALB/c mice showed only slightly elevated parasite burdens compared to the control mice, suggesting that IL-13 plays the dominant role in the control ofS. obvelata. The influence that pinworm infection has on the allergic response to a dietary antigen was found to be important. Helminth-infected mice immunized against ovalbumin (Ova) elicited more severe anaphylactic shock with reduced Ova-specific IL-4 and IL-5 than did noninfected controls, demonstrating thatS. obvelatainfection is able to influence nonrelated laboratory experiments. The latter outcome highlights the importance of maintaining mice for use as experimental models under pinworm-free conditions.
High-Affinity Interaction between Fibronectin and the Group B Streptococcal C5a Peptidase Is Unaffected by a Naturally Occurring Four-Amino-Acid Deletion That Eliminates Peptidase Activity
Authors: Tamura Glen S. , Hull James R. , Oberg Michael D. , Castner David G. 
Published: September 2006

ABSTRACT

The streptococcal C5a peptidase (ScpB) of group B streptococci (GBS) is found in virtually all clinical GBS isolates and is required for mucosal colonization in a neonatal mouse model. ScpB inhibits neutrophil chemotaxis by enzymatically cleaving the complement component C5a. We previously identified a second function of ScpB as a fibronectin (Fn) adhesin using phage display. However, phage display can identify low-affinity interactions. We therefore measured the affinity of both full-length recombinant ScpB (FL-ScpB) and the 110-amino-acid phage display fragment (Scp-PDF) for immobilized Fn using surface plasmon resonance. The affinity for Fn was very high for both FL-ScpB (equilibrium dissociation constant [

K
D

] = 4.0 nM) and Scp-PDF (

K
D

= 4.4 nM) and is consistent with a biologically significant role for the adhesin activity of ScpB. We also studied the Fn adhesin activity of a common natural variant of ScpB (ScpBΔ) that contains a 4-amino-acid deletion that eliminates peptidase activity. The integrity of
scpB
is otherwise maintained, suggesting that the Fn adhesin activity of ScpB may be responsible for its conservation in these strains. The affinities of both FL-ScpBΔ (

K
D

= 2.4 nM) and ScpBΔ-PDF (

K
D

= 1.4 nM) for Fn are unaffected by the deletion. Complementation in
trans
by both
scpB
and
scpB
Δ corrected the Fn-binding defect of an
scpB
deletion mutant GBS strain to an identical degree. The high affinity of ScpB for Fn and the maintenance of this affinity in ScpBΔ support our hypothesis that the Fn adhesin activity of
scpB
plays a role in virulence.
Chlamydia trachomatis
Infection Induces Cleavage of the Mitotic Cyclin B1
Authors: Balsara Zarine R. , Misaghi Shahram , Lafave James N. , Starnbach Michael N. 
Published: September 2006

ABSTRACT

The obligate intracellular pathogen
Chlamydia trachomatis
interferes with a number of host cell processes, including cytoskeletal organization, vesicular trafficking, and apoptosis. In this study we report that
C. trachomatis
-infected cells proliferate more slowly than uninfected cells, suggesting that
C. trachomatis
may also manipulate the eukaryotic cell cycle. We further demonstrate that
C. trachomatis
infection destabilizes specific cell cycle proteins involved in the G
2
/M transition.
C. trachomatis
-infected cells, compared to uninfected cells, have lower levels of cyclin-dependent kinase 1. Additionally,
C. trachomatis
infection induces an N-terminal truncation of the mitotic cyclin B1. Manipulation of the host cell cycle may represent a strategy used by
C. trachomatis
to ensure a stable environment conducive to bacterial growth and replication.
Rapid Development of a Gamma Interferon-Secreting Glycolipid/CD1d-Specific Vα14+NK1.1−T-Cell Subset after Bacterial Infection
Authors: Emoto Masashi , Yoshizawa Izumi , Emoto Yoshiko , Miamoto Mamiko , Hurwitz Robert , Kaufmann Stefan H. E. 
Published: September 2006

ABSTRACTThe phenotypic and functional changes of glycolipid presented by CD1d(glycolipid/CD1d) specific Vα14+T cells in the liver of mice at early stages of bacterial infection were investigated. AfterListeria monocytogenesinfection or interleukin-12 (IL-12) treatment, α-galactosylceramide/CD1d tetramer-reactive (α-GalCer/CD1d+) T cells coexpressing natural killer (NK) 1.1 marker became undetectable and, concomitantly, cells lacking NK1.1 emerged in both euthymic and thymectomized animals. Depletion of the NK1.1+subpopulation prevented the emergence of α-GalCer/CD1d+NK1.1−T cells. Before infection, NK1.1+, rather than NK1.1−, α-GalCer/CD1d+T cells coexpressing CD4 were responsible for IL-4 production, whereas gamma interferon (IFN-γ) was produced by cells regardless of NK1.1 or CD4 expression. After infection, IL-4-secreting cells became undetectable among α-GalCer/CD1d+T cells, but considerable numbers of IFN-γ-secreting cells were found among NK1.1−, but not NK1.1+, cells lacking CD4. Thus, NK1.1 surface expression and functional activities of Vα14+T cells underwent dramatic changes at early stages of listeriosis, and these alterations progressed in a thymus-independent manner. In mutant mice lacking all α-GalCer/CD1d+T cells listeriosis was ameliorated, suggesting that the subtle contribution of the NK1.1−T-cell subset to antibacterial protection is covered by more profound detrimental effects of the NK1.1+T-cell subset.
Anatomical Route of Invasion and Protective Mucosal Immunity inTrypanosoma cruziConjunctival Infection
Authors: Giddings O. K. , Eickhoff C. S. , Smith T. J. , Bryant L. A. , Hoft D. F. 
Published: September 2006

ABSTRACTTrypanosoma cruziis a protozoan parasite that can initiate mucosal infection after conjunctival exposure. The anatomical route ofT. cruziinvasion and spread after conjunctival parasite contamination remains poorly characterized. In the present work we have identified the sites of initial invasion and replication after contaminative conjunctival challenges withT. cruzimetacyclic trypomastigotes using a combination of immunohistochemical and real-time PCR confirmatory techniques in 56 mice between 3 and 14 days after challenge. Our results demonstrate that the predominant route of infection involves drainage of parasites through the nasolacrimal duct into the nasal cavity. Initial parasite invasion occurs within the ductal and respiratory epithelia. After successive waves of intracellular replication and cell-to-cell spread, parasites drain via local lymphatic channels to lymph nodes and then disseminate through the blood to distant tissues. This model of conjunctival challenge was used to identify immune responses associated with protection against mucosal infection. Preceding mucosal infection induces mucosal immunity, resulting in at least 50-fold reductions in recoverable tissue parasite DNA in immune mice compared to controls 10 days after conjunctival challenge (P< 0.05). Antigen-specific gamma interferon production by T cells was increased at least 100-fold in cells harvested from immune mice (P< 0.05). Mucosal secretions containingT. cruzi-specific secretory immunoglobulin A harvested from immune mice were shown to protect against mucosal parasite infection (P< 0.05), demonstrating that mucosal antibodies can play a role inT. cruziimmunity. This model provides an important tool for detailed studies of mucosal immunity necessary for the development of mucosal vaccines.
Comparison of Protective Efficacy of Subcutaneous versus Intranasal Immunization of Mice with aBrucella melitensisLipopolysaccharide Subunit Vaccine
Authors: Bhattacharjee Apurba K. , Izadjoo Mina J. , Zollinger Wendell D. , Nikolich Mikeljon P. , Hoover David L. 
Published: September 2006

ABSTRACTGroups of mice were immunized either subcutaneously or intranasally with purifiedBrucella melitensislipopolysaccharide (LPS) or with LPS as a noncovalent complex withNeisseria meningitidisgroup B outer membrane protein (LPS-GBOMP). Control mice were inoculated with sterile saline. Two doses of vaccine were given 4 weeks apart. Mice were challenged intranasally with virulentB. melitensisstrain 16M 4 weeks after the second dose of vaccine. Sera, spleens, lungs, and livers of mice were harvested 8 weeks after challenge. The bacterial loads in the organs were determined by culture on brucella agar plates. Protective efficacy was determined by comparing the clearance of bacteria from organs of immunized mice with the clearance of bacteria from organs of control mice. At 8 weeks postchallenge there was significant protection from disseminated infection of spleens and livers of mice intranasally immunized with either vaccine compared to infection of control mice (P< 0.01). There was no significant difference in clearance of bacteria from the lungs of immunized mice and control mice. However, mice immunized subcutaneously with either LPS or LPS-GBOMP vaccine showed significant protection against infection of the spleen (P< 0.001), liver (P< 0.001), and lungs (P< 0.05). These results show that intranasal immunization of mice with either vaccine provided significant protection against disseminated infection of the spleen and liver but subcutaneous immunization of mice with the vaccines conferred significant protection against infection of the spleen, liver, and lungs.
Transcutaneous Immunization with Toxin-Coregulated Pilin A Induces Protective Immunity against
Vibrio cholerae
O1 El Tor Challenge in Mice
Authors: Rollenhagen Julianne E. , Kalsy Anuj , Cerda Francisca , John Manohar , Harris Jason B. , LaRocque Regina C. , Qadri Firdausi , Calderwood Stephen B. , Taylor Ronald K. , Ryan Edward T. 
Published: September 2006

ABSTRACT

Toxin-coregulated pilin A (TcpA) is the main structural subunit of a type IV bundle-forming pilus of
Vibrio cholerae
, the cause of cholera. Toxin-coregulated pilus is involved in formation of microcolonies of
V. cholerae
at the intestinal surface, and strains of
V. cholerae
deficient in TcpA are attenuated and unable to colonize intestinal surfaces. Anti-TcpA immunity is common in humans recovering from cholera in Bangladesh, and immunization against TcpA is protective in murine
V. cholerae
models. To evaluate whether transcutaneously applied TcpA is immunogenic, we transcutaneously immunized mice with 100 μg of TcpA or TcpA with an immunoadjuvant (cholera toxin [CT], 50 μg) on days 0, 19, and 40. Mice immunized with TcpA alone did not develop anti-TcpA responses. Mice that received transcutaneously applied TcpA and CT developed prominent anti-TcpA immunoglobulin G (IgG) serum responses but minimal anti-TcpA IgA. Transcutaneous immunization with CT induced prominent IgG and IgA anti-CT serum responses. In an infant mouse model, offspring born to dams transcutaneously immunized either with TcpA and CT or with CT alone were challenged with 10
6
CFU (one 50% lethal dose) wild-type
V. cholerae
O1 El Tor strain N16961. At 48 h, mice born to females transcutaneously immunized with CT alone had 36% ± 10% (mean ± standard error of the mean) survival, while mice born to females transcutaneously immunized with TcpA and CT had 69% ± 6% survival (
P
< 0.001). Our results suggest that transcutaneous immunization with TcpA and an immunoadjuvant induces protective anti-TcpA immune responses. Anti-TcpA responses may contribute to an optimal cholera vaccine.
Extensive Genotypic Diversity in a Recombining Population of the Apicomplexan ParasiteTheileria parva
Authors: Katzer Frank , Ngugi Daniel , Oura Chris , Bishop Richard P. , Taracha Evans L. N. , Walker Alan R. , McKeever Declan J. 
Published: September 2006

ABSTRACTWe evaluated sexual recombination in the apicomplexan parasiteTheileria parvausing genome-wide marker analysis of haploid sporozoite populations obtained from infectedRhipicephalus appendiculatusticks. Analysis of 231 parasite clones derived by in vitro infection of bovine lymphocytes revealed 48 distinct combinations of 64 polymorphic marker loci. One genotype accounted for more than 75% of the clones, and the population was highly inbred with respect to this. The occurrence of frequent recombination was evident from reassortment of contiguous markers in blocks, with some recombination occurring within blocks. Analysis of four polymorphic loci encoding antigens targeted by protective cytotoxic-T-lymphocyte responses confirmed that these loci reassort, both within and between chromosomes, suggesting that recombination may influence immune recognition. Marker analysis of a panel of 142 clones derived from the population after an additional passage through a calf and the same tick colony revealed 18 genotypes, with the original dominant genotype accounting for 75% of the population and a higher level of inbreeding with respect to it in the remaining clones. Selected marker analysis of genomic DNA from these stabilates and the two preceding generations of the isolate, each derived from distinct tick colonies, revealed shifts in population structure with each generation, suggesting that the tick vector may impose nonrandom selective pressure on the parasite.
Immunogenicity of Duffy Binding-Like Domains That Bind Chondroitin Sulfate A and Protection against Pregnancy-Associated Malaria
Authors: Bir Nivedita , Yazdani Syed Shams , Avril Marion , Layez Corinne , Gysin Jürg , Chitnis Chetan E. 
Published: September 2006

ABSTRACT

Sequestration of
Plasmodium falciparum-
infected erythrocytes in the placenta is implicated in pathological outcomes of pregnancy-associated malaria (PAM).
P. falciparum
isolates that sequester in the placenta primarily bind chondroitin sulfate A (CSA). Following exposure to malaria during pregnancy, women in areas of endemicity develop immunity, and so multigravid women are less susceptible to PAM than primigravidae. Protective immunity to PAM is associated with the development of antibodies that recognize diverse CSA-binding, placental
P. falciparum
isolates. The epitopes recognized by such protective antibodies have not been identified but are likely to lie in conserved Duffy binding-like (DBL) domains, encoded by
var
genes, that bind CSA. Immunization of mice with the CSA-binding DBL3γ domain encoded by
var1CSA
elicits cross-reactive antibodies that recognize diverse CSA-binding
P. falciparum
isolates and block their binding to placental cryosections under flow. However, CSA-binding isolates primarily express
var2CSA
, which does not encode any DBLγ domains. Here, we demonstrate that antibodies raised against DBL3γ encoded by
var1CSA
cross-react with one of the CSA-binding domains, DBL3X, encoded by
var2CSA
. This explains the paradoxical observation made here and earlier that anti-rDBL3γ sera recognize CSA-binding isolates and provides evidence for the presence of conserved, cross-reactive epitopes in diverse CSA-binding DBL domains. Such cross-reactive epitopes within CSA-binding DBL domains can form the basis for a vaccine that provides protection against PAM.
Immunization with Polyamine Transport Protein PotD Protects Mice against Systemic Infection with
Streptococcus pneumoniae
Authors: Shah P. , Swiatlo E. 
Published: September 2006

ABSTRACT

The human pathogen
Streptococcus pneumoniae
contains genes for a putative polyamine ABC transporter which are organized in an operon and designated
potABCD
. Polyamine transport protein D (PotD) is an extracellular protein which binds polyamines and possibly other structurally related molecules. PotD has been shown to contribute to virulence in both a murine sepsis model and a pneumonia model with capsular type 3 pneumococci. The protective efficacy of recombinant PotD was evaluated by active immunization and intravenous challenge with capsular type 3 pneumococci in CBA/N mice. Immunized mice had 91.7% survival following lethal pneumococcal challenge, compared with 100% mortality in the control group. Immunized animals had high-titer anti-PotD antibodies following three immunizations with alum. Protection in a sepsis model was also seen after passive administration of rabbit antiserum raised against PotD (
P
< 0.004). These results suggest that antibodies to PotD confer protection against invasive pneumococcal disease and that this protein should be studied further as a potential vaccine candidate for protection against invasive pneumococcal infections.
Passive Immunization with a Multicomponent Vaccine against Conserved Domains of Apical Membrane Antigen 1 and 235-Kilodalton Rhoptry Proteins Protects Mice againstPlasmodium yoeliiBlood-Stage Challenge Infection
Authors: Narum David L. , Ogun Solabomi A. , Batchelor Adrian H. , Holder Anthony A. 
Published: September 2006

ABSTRACTDuring malaria parasite invasion of red blood cells, merozoite proteins bind receptors on the surface of the erythrocyte. Two candidatePlasmodium yoeliiadhesion proteins are apical membrane antigen 1 (AMA1) and the 235-kDa rhoptry proteins (P235). Previously, we have demonstrated that passive immunization with monoclonal antibodies (MAbs) 45B1 and 25.77 against AMA1 and P235, respectively, protects against a lethal challenge infection withP. yoeliiYM. We show that MAb 45B1 recognizes an epitope located on a conserved surface of PyAMA1, as determined by phage display and analysis of the three-dimensional structure of AMA1, in a region similar to that bound by theP. falciparumAMA1-specific inhibitory antibody 4G2. The epitope recognized by 25.77 could not be assigned. We report here that MAbs 45B1 and 25.77 also protect against challenge with the nonlethal parasite line 17X, in which PyAMA1 has a significantly different amino acid sequence from that in YM. When administered together, the two MAbs acted at least additively in providing protection against challenge with the virulent YM parasite. These results support the concept of developing a multicomponent blood-stage vaccine and the inclusion of polymorphic targets such as AMA1, which these results suggest contain conserved domains recognized by inhibitory antibodies.