bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Anthrax Lethal Factor-Neutralizing Monoclonal Antibody Protects Rats before and after Challenge with Anthrax Toxin
Authors: Lim Nam-Kyu , Kim Jung-Hwan , Oh Mee Sook , Lee Sangyoon , Kim Se-Yeon , Kim Keun-Soo , Kang Hyun-jung , Hong Hyo Jeong , Inn Kyung-Soo 
Published: September 2005

ABSTRACT

Lethal factor (LF) is a component of anthrax lethal toxin (LeTx). We generated anti-LF murine monoclonal antibodies (MAbs) that show LeTx-neutralizing activity in vitro and in vivo. Anti-LF MAbs were generated by immunization with recombinant LF, and the MAbs showing LeTx-neutralizing activity in vitro were selected. Two MAbs with the highest affinities, 5B13B1 (dissociation constant [

K
d

], 2.62 nM) and 3C16C3 (

K
d

, 8.18 nM), were shown to recognize the same or closely overlapping epitopes on domain III of LF. The 50% inhibitory concentration of 5B13B1 (0.21 μg/ml) was approximately one-third that of 3C16C3 (0.63 μg/ml) in the in vitro LeTx-neutralization assay. The 5B13B1 antibody, which had the highest neutralizing activity, provided perfect protection against LeTx challenge in an in vivo LeTx neutralization assay using Fisher 344 rats. In addition, the antibody showed pre- and postexposure prophylactic effects in the animal experiments. This is the first report that an MAb binding to domain III of LF has neutralizing activity against LeTx. The 5B13B1 antibody may be useful in prophylaxis against anthrax poisoning.
Transfection ofTrypanosoma cruziwith Host CD40 Ligand Results in Improved Control of Parasite Infection
Authors: Chamekh Mustapha , Vercruysse Vincent , Habib Mohammed , Lorent Maxime , Goldman Michel , Allaoui Abdelmounaïm , Vray Bernard 
Published: September 2005

ABSTRACTWe have previously shown that infection byTrypanosoma cruzi, a parasitic protozoan, is reduced by injection of CD40 ligand (CD40L)-transfected 3T3 fibroblasts (D. Chaussabel, F. Jacobs, J. de Jonge, M. de Veerman, Y. Carlier, K. Thielemans, M. Goldman, and B. Vray, Infect. Immun.67:1929-1934, 1999). This prompted us to transfectT. cruziwith the murine CD40L gene and to study the consequences of this transfection on the course of infection. For this, epimastigotes (Y strain) were electroporated with the pTEX vector alone or the pTEX-CD40L construct, and transfected cells were selected for their resistance to Geneticin G418. Then strain Y-, pTEX-, and pTEX-CD40L-transfected epimastigotes were transformed by metacyclogenesis into mammalian infective forms called Y, YpTEX, and YpTEX-CD40L trypomastigotes. Transfection of the CD40L gene and expression of the CD40L protein were assessed by reverse transcription-PCR and Western blot analysis. The three strains of parasites were infective in vitro for mouse peritoneal macrophages. When organisms were inoculated into mice, a very low level of parasitemia and no mortality were seen with the YpTEX-CD40L strain compared to the Y and YpTEX strains. Furthermore, the proliferative capacity and the secretion of gamma interferon were both preserved in spleen cells (SCs) from YpTEX-CD40L-infected mice but not with SCs from Y- and YpTEX-infected mice. These results suggest that the CD40L produced by transfectedT. cruziis involved in the modulation of an antiparasite immune response. Moreover, mice surviving YpTEX-CD40L infection resisted a challenge infection with the wild-type strain. Taken together, our data demonstrate the feasibility of generating aT. cruzistrain expressing a bioactive host costimulatory molecule that counteracts the immunodeficiency induced by the parasite during infection and enhances protective immunity against a challenge infection.
Role of NADase in Virulence in Experimental Invasive Group A Streptococcal Infection
Authors: Bricker Angela L. , Carey Vincent J. , Wessels Michael R. 
Published: September 2005

ABSTRACT

Group A streptococci (GAS) produce several exoproteins that are thought to contribute to the pathogenesis of human infection. Two such proteins, streptolysin O (SLO) and NAD
+
-glycohydrolase (NADase), have been shown to interact functionally as a compound signaling toxin. When GAS are bound to the surface of epithelial cells in vitro, SLO forms pores in the cell membrane and delivers NADase to the epithelial cell cytoplasm. In vitro, intoxication of keratinocytes with NADase is associated with cytotoxic effects and induction of apoptosis; however, the importance of NADase during infection of an animal host has not been established. We employed isogenic GAS mutants to assess the contribution of NADase activity to GAS virulence in vivo using mouse models of invasive soft-tissue infection and septicemia. In both models, mutant GAS that lacked NADase activity were significantly attenuated for virulence compared with the isogenic wild-type parent, confirming an important role for NADase in the infection of a host animal. A double mutant lacking SLO and NADase activity had an intermediate virulence phenotype, consistent with the hypothesis that SLO evokes a protective innate immune response. We conclude that NADase and SLO together enhance GAS virulence in vivo.
Markers for Host-Induced Gene Expression inTrichophytonDermatophytosis
Authors: Kaufman Gil , Berdicevsky Israela , Woodfolk Judith A. , Horwitz Benjamin A. 
Published: September 2005

ABSTRACTDermatophytes are adapted to infect keratinized tissues by their ability to utilize keratin as a nutrient source. Although there have been numerous reports that dermatophytes likeTrichophytonsp. secrete proteolytic enzymes, virtually nothing is known about the patterns of gene expression in the host or even when the organisms are cultured on protein substrates in the absence of a host. We characterized the expression of an aminopeptidase gene, theTrichophyton mentagrophyteshomolog of theTrichophyton rubrumTri r 4 gene. TheT. rubrumgene was originally isolated based on the ability of the protein encoded by it to induce immediate and delayed-type hypersensitivity in skin tests.T. mentagrophytesTri m 4 is closely related to Tri r 4 (almost 94% identity at the protein level). Tri m 4 resembles other protease-encoding genes thought to be virulence factors (for example, DPP V ofAspergillus fumigatus). The Tri m 4 protein was detected immunochemically both in fungal extracts and in the culture medium. Expression of the Tri m 4 gene was induced severalfold whenT. mentagrophyteswas grown on keratin and elastin. Ex vivo, strong induction was observed after culture on blood plasma, but the use of homogenized skin did not result in a significant increase in Tri m 4 transcript levels. In order to identify additional genes encoding putative virulence factors, differential cDNA screening was performed. By this method, a fungal thioredoxin and a cellulase homolog were identified, and both genes were found to be strongly induced by skin extracellular matrix proteins. Induction by superficial (keratin) and deep (elastin) skin elements suggests that the products of these genes may be important in both superficial and deep dermatophytosis, and models for their function are proposed. Upregulation of several newly identifiedT. mentagrophytesgenes on protein substrates suggests that these genes encode proteins which are relevant to the dermatophyte-skin interaction.
Identification of Immunogenic and Serum Binding Proteins of
Staphylococcus epidermidis
Authors: Sellman Bret R. , Howell Alan P. , Kelly-Boyd Cari , Baker Steve M. 
Published: September 2005

ABSTRACT

Staphylococcus epidermidis
is a commensal of human skin and a leading cause of nosocomial bloodstream infections. Limited information is available about
S. epidermidis
proteins that are expressed upon transition to the bloodstream or those involved in host-pathogen interactions. A cell surface fraction from
S. epidermidis
0-47 grown in rabbit serum to mimic environmental signals encountered during a bloodstream infection was separated by two-dimensional (2D) gel electrophoresis. Following 2D separation, the proteins were transferred to nitrocellulose and detected with either pooled sera generated in rabbits immunized with live
S. epidermidis
0-47 or with biotin-labeled serum proteins eluted from the surface of bacteria grown in rabbit serum. Twenty-nine immunoreactive or serum binding proteins of
S. epidermidis
were identified by mass spectrometry. Twenty-seven of the corresponding genes were expressed in
Escherichia coli
, and the purified recombinant proteins were used to immunize mice. In a preliminary screen, 12 of the 27 recombinant proteins induced a response that reduced the number of bacteria recovered from the spleen or bloodstream of infected mice. In subsequent vaccination studies, 5 of the 12 proteins resulted in a statistically significant reduction in the number of bacteria. The identification of five candidate vaccine antigens from the initial screen of only 29 proteins demonstrates the utility of this approach.
Human Antibody Response to Outer Membrane Protein G1a, a Lipoprotein of
Moraxella catarrhalis
Authors: Adlowitz Diana G. , Sethi Sanjay , Cullen Paul , Adler Ben , Murphy Timothy F. 
Published: September 2005

ABSTRACT

Moraxella catarrhalis
is an important cause of respiratory infections in adults with chronic obstructive pulmonary disease (COPD) and of otitis media in children. Outer membrane protein (OMP) G1a is an ∼29-kDa surface lipoprotein and is a potential vaccine candidate. The gene that encodes OMP G1a was expressed and purified using a novel plasmid vector. [
3
H]palmitic acid labeling demonstrated that both native and recombinant OMP G1a contain covalently bound palmitic acid. To assess the expression of OMP G1a during human infection, paired sera and sputum supernatants from adults with COPD followed prospectively were studied by enzyme-linked immunosorbent assays with recombinant lipidated OMP G1a to detect antibodies made specifically during carriage of
M. catarrhalis
. Overall, 23% of patients developed either a serum immunoglobulin G (IgG) response (9%) or sputum IgA response (21%) to OMP G1a, following 100 episodes of acquisition and clearance of
M. catarrhalis
. Patients developed antibody responses at similar rates following episodes of clinical exacerbation compared to asymptomatic colonization. Serum IgG antibodies following natural infection were directed predominantly at OMP G1a epitopes that are not exposed on the bacterial surface. These data show that OMP G1a is expressed during infection of the human respiratory tract and is a target of systemic and mucosal antibodies. These observations indicate that OMP G1a, a highly conserved surface protein, should be evaluated further as a vaccine candidate.
Protection against Hemorrhagic Colitis in an Animal Model by Oral Immunization with Isogeneic Rabbit Enteropathogenic
Escherichia coli
Attenuated by Truncating Intimin
Authors: Agin Tonia S. , Zhu Chengru , Johnson Laura A. , Thate Timothy E. , Yang Zhuolu , Boedeker Edgar C. 
Published: September 2005

ABSTRACT

Strains of Shiga toxin (Stx)-producing
Escherichia coli
, also called enterohemorrhagic
E. coli
(EHEC), are important food-borne pathogens for humans. Most EHEC strains intimately adhere to the intestinal mucosa in a characteristic attaching and effacing (A/E) pattern, which is mediated by the bacterial adhesin intimin. Subsequent release of Stx1 and/or Stx2 leads to the frequent development of hemorrhagic colitis and, less commonly, to hemolytic-uremic syndrome. The aim of the present study was to develop an attenuated A/E
E. coli
strain for use as a vaccine against EHEC infection encoding a truncated intimin lacking adhesive capacity, but which would still express somatic antigens, other products of the locus of enterocyte effacement pathogenicity island, and an immunogenic remnant of the intimin molecule. A single-nucleotide deletion was generated in the
eae
gene in the prototype rabbit A/E
E. coli
strain RDEC-1 (O15:H−), which resulted in truncation of intimin by 81 C-terminal residues (860 to 939 amino acids) containing a disulfide loop. Inoculation of rabbits with large doses of the truncated intimin mutant (RDEC-1Δeae
860-939
) was well tolerated, as observed by the absence of clinical signs of disease or evidence of intestinal A/E lesions. The efficacy of RDEC-1Δeae
860-939
as a vaccine was evaluated by orogastric inoculation of rabbits with RDEC-1Δeae
860-939
followed by challenge with the virulent strain RDEC-H19A, an Stx1-producing derivative of wild-type RDEC-1 capable of inducing hemorrhagic colitis in rabbits. Following RDEC-H19A challenge, nonimmunized control rabbits exhibited characteristic weight loss with watery to bloody diarrhea and demonstrated intimate bacterial attachment, effacement of microvilli, submucosal edema, mucosal heterophile infiltrates, and Shiga toxin-induced vascular lesions. In contrast, the RDEC-1Δeae
860-939
-immunized rabbits showed no clinical signs of disease, maintained normal weight gain, had reduced fecal shedding of challenge organisms, and showed an absence of gross or microscopic lesions in the intestinal mucosa. Serum antibodies specific to intimin were detected among rabbits immunized with RDEC-1Δeae
860-939
, indicating that truncation of the intimin functional domain not only attenuated bacterial virulence, but also retained at least some of the immunogenicity of native intimin. Although it is not possible to gauge the exact contribution of residual intimin immunity to protection, this attenuation strategy for A/E
E. coli
strains shows promise for the development of effective vaccines to prevent EHEC infection in humans and animals.
Expression of the
Rickettsia prowazekii pld
or
tlyC
Gene in
Salmonella enterica
Serovar Typhimurium Mediates Phagosomal Escape
Authors: Whitworth Ted , Popov Vsevolod L. , Yu Xue-Jie , Walker David H. , Bouyer Donald H. 
Published: September 2005

ABSTRACT

Members of the genus
Rickettsia
possess the ability to invade host cells and promptly escape from phagosomal vacuoles into the host cell cytosol, thereby avoiding destruction within the endosomal pathway. The mechanism underlying rickettsial phagosomal escape remains unknown, although the genomic sequences of several rickettsial species have allowed for the identification of four genes with potential membranolytic activities (
tlyA
,
tlyC
,
pat1
, and
pld
). This study was undertaken to determine which of the selected genes of
Rickettsia prowazekii
mediate the escape process. Quantitative ultrastructural analyses indicated that the period of active phagosomal escape was between 30 and 50 min postinfection. Reverse transcriptase PCR analyses determined that
tlyC
and
pld
were transcribed during the period of active phagosomal escape but that
tlyA
and
pat1
were not. The functionality of both
tlyC
and
pld
was determined by complementation studies of
Salmonella
, which replicates within endosomes. Complementation of
Salmonella
organisms with either
tlyC
or
pld
resulted in the escape of transformants from endosomal vacuoles into the host cell cytosol demonstrated by quantitative ultrastructural analyses. These data suggest a role for
tlyC
and
pld
in the process of phagosomal escape by
R. prowazekii
.
Hyperinfectivity of Human-Passaged
Vibrio cholerae
Can Be Modeled by Growth in the Infant Mouse
Authors: Alam Ashfaqul , LaRocque Regina C. , Harris Jason B. , Vanderspurt Cecily , Ryan Edward T. , Qadri Firdausi , Calderwood Stephen B. 
Published: September 2005

ABSTRACT

It has previously been shown that passage of
Vibrio cholerae
through the human intestine imparts a transient hyperinfectious phenotype that may contribute to the epidemic spread of cholera. The mechanism underlying this human-passaged hyperinfectivity is incompletely understood, in part due to inherent difficulties in recovering and studying organisms that are freshly passed in human stool. Here, we demonstrate that passage of
V. cholerae
through the infant mouse intestine leads to an equivalent degree of hyperinfectivity as passage through the human host. We have used this infant mouse model of host-passaged hyperinfectivity to characterize the timing and the anatomic location of the competitive advantage of mouse-passaged
V. cholerae
as well as the contribution of three type IV pili to the phenotype.
Identification of a Novel Sialic Acid Transporter in
Haemophilus ducreyi
Authors: Post Deborah M. B. , Mungur Rachna , Gibson Bradford W. , Munson Robert S. 
Published: September 2005

ABSTRACT

Haemophilus ducreyi
, the causative agent of chancroid, produces a lipooligosaccharide (LOS) which terminates in
N
-acetyllactosamine. This glycoform can be further extended by the addition of a single sialic acid residue to the terminal galactose moiety.
H. ducreyi
does not synthesize sialic acid, which must be acquired from the host during infection or from the culture medium when the bacteria are grown in vitro. However,
H. ducreyi
does not have genes that are highly homologous to the genes encoding known bacterial sialic acid transporters. In this study, we identified the sialic acid transporter by screening strains in a library of random transposon mutants for those mutants that were unable to add sialic acid to
N
-acetyllactosamine-containing LOS. Mutants that reacted with the monoclonal antibody 3F11, which recognizes the terminal lactosamine structure, and lacked reactivity with the lectin
Maackia amurensis
agglutinin, which recognizes α2,3-linked sialic acid, were further characterized to demonstrate that they produced a
N
-acetyllactosamine-containing LOS by silver-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometric analyses. The genes interrupted in these mutants were mapped to a four-gene cluster with similarity to genes encoding bacterial ABC transporters. Uptake assays using radiolabeled sialic acid confirmed that the mutants were unable to transport sialic acid. This study is the first report of bacteria using an ABC transporter for sialic acid uptake.
NK Cells in Gamma-Interferon-Deficient Mice Suppress Lung Innate Immunity againstMycoplasmaspp
Authors: Woolard Matthew D. , Hudig Dorothy , Tabor Leslie , Ivey James A. , Simecka Jerry W. 
Published: September 2005

ABSTRACTThe purpose of this study was to examine the 100-fold difference in mycoplasma levels in lungs of gamma interferon knockout (IFN-γ−/−) mice compared to those seen with wild-type BALB/c mice at 3 days postinfection. NK cells secreted IFN-γ; however, their cytotoxic granule extracts failed to kill mycoplasma. We found a conundrum: the clearance of organisms was as effective in NK-depleted IFN-γ−/−animals as in wild-type mice (with both IFN-γ and NK cells). NK+IFN-γ−/−animals had high mycoplasma burdens, but, after NK-like cell depletion, mycoplasma numbers were controlled. Essentially, IFN-γ was important in animals with NK-like cells and unimportant in animals without NK cells, suggesting that IFN-γ counters deleterious effects of NK-like cells. Impairment of innate immunity in IFN-γ−/−mice was not due to NK-like cell killing of macrophages. The increased levels of inflammatory cytokines and neutrophils in lung fluids of NK+IFN-γ−/−mice were reduced after NK cell depletion. In summary, in the murine model that resembles chronic human disease, innate immunity to mycoplasma requires IFN-γ when there are NK-like cells and the positive effects of IFN-γ counteract negative effects of NK-like cells. When imbalanced, NK-like cells promote disease. Thus, it was not the lack of IFN-γ but the presence of a previously unrecognized NK-like cell-suppressive activity that contributed to the higher mycoplasma numbers. It appears that pulmonary NK cells may contribute to the immunosuppressive environment of the lung, but when needed, these dampening effects can be counterbalanced by IFN-γ. Furthermore, there may be instances where perturbation of this regulatory balance contributes to the susceptibility to and severity of disease.
Comparative Opsonic and Protective Activities of
Staphylococcus aureus
Conjugate Vaccines Containing Native or Deacetylated Staphylococcal Poly-
N
-Acetyl-β-(1-6)-Glucosamine
Authors: Maira-Litrán Tomás , Kropec Andrea , Goldmann Donald A. , Pier Gerald B. 
Published: September 2005

ABSTRACT

Staphylococcus aureus
and
Staphylococcus epidermidis
both synthesize the surface polysaccharide poly-
N
-acetyl-β-(1-6)-glucosamine (PNAG), which is produced in vitro with a high level (>90%) of the amino groups substituted by acetate. Here, we examined the role of the acetate substituents of PNAG in generating opsonic and protective antibodies. PNAG and a deacetylated form of the antigen (dPNAG; 15% acetylation) were conjugated to the carrier protein diphtheria toxoid (DT) and used to immunize animals. Mice responded in a dose-dependent fashion to both conjugate vaccines, with maximum antibody titers observed at the highest dose and 4 weeks after the last of three weekly immunizations. PNAG-DT and dPNAG-DT vaccines were also very immunogenic in rabbits. Antibodies raised to the conjugate vaccines in rabbits mediated the opsonic killing of various staphylococcal strains, but the specificity of the opsonic killing was primarily to dPNAG, as this antigen inhibited the killing of
S. aureus
strains by both PNAG- and dPNAG-specific antibodies. Passive immunization of mice with anti-dPNAG-DT rabbit sera showed significant levels of clearance of
S. aureus
from the blood (54 to 91%) compared to control mice immunized with normal rabbit sera, whereas PNAG-specific antibodies were ineffective at clearing
S. aureus
. Passive immunization of mice with a goat antiserum raised to the dPNAG-DT vaccine protected against a lethal dose of three different
S. aureus
strains. Overall, these data show that immunization of animals with a conjugate vaccine of dPNAG elicit antibodies that mediated opsonic killing and protected against
S. aureus
infection, including capsular polysaccharide types 5 and 8 and an untypable strain.
Successful Selection of Cross-Protective Vaccine Candidates for
Ornithobacterium rhinotracheale
Infection
Authors: Schuijffel D. F. , van Empel P. C. M. , Pennings A. M. M. A. , van Putten J. P. M. , Nuijten P. J. M. 
Published: September 2005

ABSTRACT

Ornithobacterium rhinotracheale
is a bacterial pathogen known for causing respiratory disease in poultry. In this study, we demonstrate for the first time that cross-protective immunity against different
O. rhinotracheale
serotypes can be induced by live vaccination. Sera from these live-vaccinated and cross-protected birds were used to identify new vaccine targets by screening an
O. rhinotracheale
expression library. Out of 20,000 screened plaques, a total of 30 cross-reactive clones were selected for further analysis. Western blot analysis and DNA sequencing identified eight different open reading frames. The genes encoding the eight cross-reactive antigens were amplified, cloned in an expression vector, and expressed in
Escherichia coli
. Purified recombinant proteins with a molecular mass ranging from 35.9 kDa to 62.9 kDa were mixed and tested as a subunit vaccine for (cross-)protection against challenge with homologous and heterologous
O. rhinotracheale
serotypes in chickens. Subunit vaccination resulted in the production of antibodies reactive to the recombinant proteins on Western blot, and this eight-valent vaccine conferred both homologous and heterologous protection against
O. rhinotracheale
challenge in chickens.