bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Resistance to Thrombin-Induced Platelet Microbicidal Protein Is Associated with Enhanced Progression and Hematogenous Dissemination in Experimental
Staphylococcus aureus
Infective Endocarditis
Authors: Dhawan Vinod K. , Bayer Arnold S. , Yeaman Michael R. 
Published: December 2019

ABSTRACT

We examined the influence of thrombin-induced platelet microbicidal protein 1 (tPMP-1) on the progression and hematogenous dissemination of experimental endocarditis caused by isogenic
Staphylococcus aureus
strains differing in tPMP susceptibility (tPMP
s
) or resistance (tPMP
r
) in vitro. Following simultaneous challenge of animals with both strains, significantly higher tPMP
r
bacterial densities were present in vegetations (
P
< 0.0001), kidneys (
P
< 0.0001), and spleens (
P
< 0.0001) compared with those for the tPMP
s
strain. These data indicate that tPMP-1 limits the intravegetation proliferation and hematogenous dissemination of a tPMP
s
strain in experimental endocarditis, while the tPMP
r
phenotype confers a selective advantage associated with the enhanced progression of this infection.
Protection against Ascending Infection of the Genital Tract byChlamydia trachomatisIs Associated with Recruitment of Major Histocompatibility Complex Class II Antigen-Presenting Cells into Uterine Tissue
Authors: Stagg A. J. , Tuffrey M. , Woods C. , Wunderink E. , Knight S. C. 
Published: December 2019

ABSTRACTA mouse model of ascending infection following intravaginal inoculation with a strain ofChlamydia trachomatisisolated from humans has been used to identify immune mechanisms associated with protection against genital infection. BALB/c and C3H mice differed in their susceptibilities to infection and inflammatory disease. In both mouse strains, ascension of the organism and recruitment of bone marrow-derived mononuclear leukocytes were evident in uterine tissue 1 week postinfection. By 3 weeks the organism had been cleared and inflammation had been resolved in the BALB/c mice, but both persisted in the C3H animals. In athymic nude BALB/c mice both the organism and inflammation persisted, indicating the influence of the hosts’ immune response on the outcome of infection. Both BALB/c and C3H mice had a Th1 response in draining lymph nodes, with predominant production of gamma interferon and tumor necrosis factor alpha, low levels of interleukin-10, and no detectable levels of interleukin-4. However, the composition of the early uterine infiltrate differed in these two mouse strains. Cell surface labeling and analysis of light scatter properties by flow cytometry identified a population of large, CD45+major histocompatibility complex class II mononuclear cells, which were a prominent feature of the infiltrates in BALB/c mice but were present in significantly lower numbers in C3H mice. These cells expressed the costimulatory molecules CD86 and CD40 and stimulated allogeneic T cells, suggesting that these mononuclear cells are a population of antigen-presenting cells and that they may play a role in clearing antigen and protecting against inflammatory disease in BALB/c mice. An additional level of immunological control may thus exist in genital chlamydial infection.
Iron Starvation ofBordetella aviumStimulates Expression of Five Outer Membrane Proteins and Regulates a Gene Involved in Acquiring Iron from Serum
Authors: Connell Terry D. , Dickenson Amy , Martone Andrew J. , Militello Kevin T. , Filiatraut Melanie J. , Hayman Mark L. , Pitula Joseph 
Published: December 2019

ABSTRACTIron starvation ofBordetella aviuminduced expression of five outer membrane proteins with apparent molecular masses of 95, 92, 91.5, 84, and 51 kDa. Iron-responsive outer membrane proteins (FeRPs) of similar sizes were detected in six of six strains ofB. avium, suggesting that the five FeRPs are common constituents of the outer membrane of most, if not all, strains ofB. avium. Iron-regulated genes ofB. aviumwere targeted for mutagenesis with the transposon TnphoA. Two mutants with iron-responsive alkaline phosphatase activities were isolated from the transposon library. The transposon insertion did not alter the iron-regulated expression of the five FeRPs in mutant Pho-6. The mutant Pho-20 exhibited a loss in expression of the 95-kDa FeRP and the 84-kDa FeRP. Both Pho-6 and Pho-20 were able to use free iron as a nutrient source. However, Pho-20 was severely compromised in its ability to use iron present in turkey serum. The data indicated that the mutation in Pho-20 affected expression of one or more components of an uptake machinery that is involved in acquisition of iron from organic ferricomplexes.
The Role of Protegrins and Other Elastase-Activated Polypeptides in the Bactericidal Properties of Porcine Inflammatory Fluids
Authors: Shi Jishu , Ganz Tomas 
Published: December 2019

ABSTRACTThe mammalian host response to infection includes the production and secretion of antimicrobial peptides from phagocytes and epithelial cells. Protegrins, a group of broadly microbicidal peptides isolated originally from porcine neutrophil lysates, were found to be stored as inactive proforms in porcine neutrophil granules but could be activated extracellularly by neutrophil elastase. We assessed the biological role of protegrins and other elastase-activated polypeptides in the microbicidal activity of neutrophil secretions and inflammatory fluids. When stimulated with phorbol myristate acetate (PMA), neutrophils generated stable microbicidal activity against bothEscherichia coliandListeria monocytogenesunder normal-salt conditions and in the presence of 0 to 10% serum. The generation of these antimicrobial substances was dependent on neutrophil elastase, since it was inhibited by 1 mMN-methoxysuccinyl-Ala-Ala-Pro-Val chloromethyl ketone when it was present during activation, but not when this inhibitor was added afterwards. However, elastase-dependent activation of proprotegrins to protegrins in PMA-stimulated neutrophils was not inhibited by the presence of 1 to 2% serum. Porcine neutrophils also released antibacterial activity during phagocytosis of latex beads, and this too was dependent in large part on elastase-activated polypeptides, including protegrins. Moreover, protegrins were found at bactericidal concentrations in cell-free abscess fluid from naturally infected pigs. Taken together, these studies show that protegrins and other elastase-activated polypeptides are important stable antibacterial factors in porcine neutrophil secretions. The potential host defense role of elastase as an activating enzyme for the precursors of microbicidal peptides must be taken into account when therapeutic inhibitors of neutrophil elastase are evaluated for clinical use as anti-inflammatory agents.
An Epitope Delivery System for Use with Recombinant Mycobacteria
Authors: Hetzel Charlotte , Janssen Riny , Ely Sarah J. , Kristensen Nanna M. , Bunting Karen , Cooper Jonathan B. , Lamb Jonathan R. , Young Douglas B. , Thole Jelle E. R. 
Published: December 2019

ABSTRACTWe have developed a novel epitope delivery system based on the insertion of peptides within a permissive loop of a bacterial superoxide dismutase molecule. This system allowed high-level expression of heterologous peptides in two mycobacterial vaccine strains,Mycobacterium bovisbacille Calmette-Guérin (BCG) andMycobacterium vaccae. The broader application of the system was analyzed by preparation of constructs containing peptide epitopes from a range of infectious agents and allergens. We report detailed characterization of the immunogenicity of one such construct, in which an epitope from the Der p1 house dust mite allergen was expressed inM. vaccae. The construct was able to stimulate T-cell hybridomas specific for Der p1, and it induced peptide-specific gamma interferon responses when used to immunize naive mice. This novel expression system demonstrates new possibilities for the use of mycobacteria as vaccine delivery vehicles.
Antibody Responses to Capsular Polysaccharide Backbone and O-Acetate Side Groups of
Streptococcus pneumoniae
Type 9V in Humans and Rhesus Macaques
Authors: McNeely Tessie B. , Staub Joan M. , Rusk Cynthia M. , Blum Michael J. , Donnelly John J. 
Published: December 2019

ABSTRACT

Streptococcus pneumoniae
is responsible for high rates of pneumococcal bacteremia, meningitis, pneumonia, and acute otitis media worldwide. Protection from disease is conferred by antibodies specific for the polysaccharide (Ps) capsule of the bacteria. Of the four types of group 9 pneumococci, types 9N and 9V cause the most disease, and both types are included in the polyvalent pneumococcal vaccine. The type 9V capsule consists of repeating pentasaccharide units linearly arranged, with an average of 1 to 2 mol of O-acetate side chains per mol of repeat units, added in a complex pattern in which not all repeat units are alike. α-GlcA residues may be O-acetylated in the 2 (17%) or 3 (25%) position and β-ManNAc residues may be O-acetylated in the 4 (6%) or 6 (55%) position. Under certain conditions, the O-acetate side chains are subject to oxidation, which results in subsequent de-O-acetylation of a significant number of the repeat units. This de-O-acetylation could adversely affect the efficacy of a vaccine containing the 9V Ps. A study was undertaken to compare the relative contributions of O-acetate and Ps backbone epitopes in the immune response to
S. pneumoniae
9V type-specific Ps. In both an infant rhesus monkey model and humans, antibodies against the non-O-acetylated 9V backbone as well as against O-acetylated 9V Ps were detected. Functional (opsonophagocytic) activity was observed in antisera in which the predominant species of antibody recognized de-O-acetylated 9V Ps. We concluded that the O-acetate side groups, while recognized, are not essential to the ability of the 9V Ps to induce functional antibody responses.
Complex Serology and Immune Response of Mice to Variant High-Molecular-Weight O Polysaccharides Isolated from
Pseudomonas aeruginosa
Serogroup O2 Strains
Authors: Hatano Kazue , Pier Gerald B. 
Published: December 2019

ABSTRACT

The O antigen of the
Pseudomonas aeruginosa
lipopolysaccharide is the optimal target for protective antibodies, but the unusual and complex nature of their sugar substituents has made it difficult to define the range of these structures needed in an effective vaccine. Most clinical isolates of
P. aeruginosa
can be classified into 10 O-antigen serogroups, but slight chemical differences among O polysaccharides within a serogroup give rise to subtype epitopes. These epitopes could impact the reactivity of O-antigen-specific antibodies, as well as the susceptibility of a target strain to protective, opsonic antibodies. To define parameters of serogroup and subtype-epitope immunogenicity, antigenicity, and surface expression on
P. aeruginosa
cells, we prepared high-molecular-weight O-polysaccharide vaccines from strains of
P. aeruginosa
serogroup O2, for which eight structurally variant O antigens expressing six defined subtype epitopes (O2a to O2f) have been identified. A complex pattern of immune responses to these antigens was observed following vaccination of mice. The high-molecular-weight O polysaccharides were generally more immunogenic at low doses (1 and 10 μg) than at a high dose (50 μg) and usually elicited antibodies that opsonized the homologous strain for phagocytic killing. Some of the individual polysaccharides elicited cross-opsonic antibodies to a variable number of strains that express all of the defined serogroup O2 subtype epitopes. Combination into one vaccine of two antigens that individually elicited cross-reactive opsonic antibodies to most members of the O2 serogroup inhibited, instead of enhanced, the production of antibodies broadly reactive with most serogroup O2 subtype strains. Thus, immune responses to
P. aeruginosa
O antigens may be restricted to a limited range of epitopes on structurally complex O antigens, and combining multiple related antigens into a single vaccine formulation may inhibit the production of those antibodies best able to protect against most
P. aeruginosa
strains within a given O-antigen serogroup.
A Live Recombinant Avirulent Oral
Salmonella
Vaccine Expressing Pneumococcal Surface Protein A Induces Protective Responses against
Streptococcus pneumoniae
Authors: Nayak Amiya R. , Tinge Steven A. , Tart Rebecca C. , McDaniel Larry S. , Briles David E. , Curtiss Roy 
Published: December 2019

ABSTRACT

A live oral recombinant
Salmonella
vaccine strain expressing pneumococcal surface protein A (PspA) was developed. The strain was attenuated with Δ
cya Δcrp
mutations. Stable expression of PspA was achieved by the use of the balanced-lethal vector-host system, which employs an
asd
deletion in the host chromosome to impose an obligate requirement for diaminopimelic acid. The chromosomal Δ
asd
mutation was complemented by a plasmid vector possessing the
asd
+
gene. A portion of the
pspA
gene from
Streptococcus pneumoniae
Rx1 was cloned onto a multicopy Asd
+
vector. After oral immunization, the recombinant
Salmonella
-PspA vaccine strain colonized the Peyer’s patches, spleens, and livers of BALB/cByJ and CBA/N mice and stimulated humoral and mucosal antibody responses. Oral immunization of outbred New Zealand White rabbits with the recombinant
Salmonella
strain induced significant anti-PspA immunoglobulin G titers in serum and vaginal secretions. Polyclonal sera from orally immunized mice detected PspA on the
S. pneumoniae
cell surface as revealed by immunofluorescence. Oral immunization of BALB/cJ mice with the PspA-producing
Salmonella
strain elicited antibody to PspA and resistance to challenge by the mouse-virulent human clinical isolate
S. pneumoniae
WU2. Immune sera from orally immunized mice conferred passive protection against otherwise lethal intraperitoneal or intravascular challenge with strain WU2.
Molecular Cloning of a 32-Kilodalton Lipoprotein Component of a Novel Iron-Regulated
Staphylococcus epidermidis
ABC Transporter
Authors: Cockayne Alan , Hill Philip J. , Powell Nick B. L. , Bishop Keith , Sims Cate , Williams Paul 
Published: December 2019

ABSTRACT

Our previous studies identified two iron-regulated cytoplasmic membrane proteins of 32 and 36 kDa expressed by both
Staphylococcus epidermidis
and
Staphylococcus aureus
. In this study we show by Triton X-114 phase partitioning and tritiated palmitic acid labelling that these proteins are lipoproteins which are anchored into the cytoplasmic membrane by their lipid-modified N termini. In common with those of some other gram-positive bacteria, these highly immunogenic lipoproteins were released from the bacterial cell into the culture supernatants, with release being promoted by growth of the bacteria under iron-restricted conditions. Immunoelectron microscopy with a monospecific rabbit antiserum to the 32-kDa
S. epidermidis
lipoprotein showed that the majority of the antigen was distributed throughout the staphylococcal cell wall. Only minor quantities were detected in the cytoplasmic membrane, and exposure of the lipoprotein on the bacterial surface was minimal. A monoclonal antibody raised to the 32-kDa lipoprotein of
S. aureus
was used in immunoblotting studies to investigate the conservation of this antigen among a variety of staphylococci. The monoclonal antibody reacted with polypeptides of 32 kDa in
S. epidermidis
and
S. aureus
and of 40 kDa in
Staphylococcus hominis
. No reactivity was detected with
Staphylococcus lugdunensis
,
Staphylococcus cohni
, or
Staphylococcus haemolyticus
. The gene encoding the 32-kDa lipoprotein from
S. epidermidis
has been isolated from a Lambda Zap II genomic DNA library and found to be a component of an iron-regulated operon encoding a novel ABC-type transporter. The operon contains three genes, designated
sitA
, -
B
, and -
C
, encoding an ATPase, a cytoplasmic membrane protein, and the 32-kDa lipoprotein, respectively. SitC shows significant homology both with a number of bacterial adhesins, including FimA of
Streptococcus parasanguis
and ScaA of
Streptococcus gordonii
, and with lipoproteins of a recently described family of ABC transporters with proven or putative metal ion transport functions. Although the solute specificity of this novel transporter has not yet been determined, we speculate that it may be involved in either siderophore- or transferrin-mediated iron uptake in
S. epidermidis
.
Gelsolin, a Protein That Caps the Barbed Ends and Severs Actin Filaments, Enhances the Actin-Based Motility of
Listeria monocytogenes
in Host Cells
Authors: Laine Roney O. , Phaneuf Katherine L. , Cunningham Casey C. , Kwiatkowski David , Azuma Toshi , Southwick Frederick S. 
Published: December 2019

ABSTRACT

The actin-based motility of
Listeria monocytogenes
requires the addition of actin monomers to the barbed or plus ends of actin filaments. Immunofluorescence micrographs have demonstrated that gelsolin, a protein that both caps barbed ends and severs actin filaments, is concentrated directly behind motile bacteria at the junction between the actin filament rocket tail and the bacterium. In contrast, CapG, a protein that strictly caps actin filaments, fails to localize near intracellular
Listeria
. To explore the effect of increasing concentrations of gelsolin on bacterial motility, NIH 3T3 fibroblasts stably transfected with gelsolin cDNA were infected with
Listeria
. The C5 cell line containing 2.25 times control levels of gelsolin supported significantly higher velocities of bacterial movement than did control fibroblasts (mean ± standard error of the mean, 0.09 ± 0.003 μm/s [
n
= 176] versus 0.05 ± 0.003 μm/s [
n
= 65]). The rate of disassembly of the
Listeria
-induced actin filament rocket tail was found to be independent of gelsolin content. Therefore, if increases in gelsolin content result in increases in
Listeria
-induced rocket tail assembly rates, a positive correlation between gelsolin content and tail length would be expected. BODIPY-phalloidin staining of four different stably transfected NIH 3T3 fibroblast cell lines confirmed this expectation (
r
= 0.92). Rocket tails were significantly longer in cells with a high gelsolin content. Microinjection of gelsolin 1/2 (consisting of the amino-terminal half of native gelsolin) also increased bacterial velocity by more than 2.2 times. Microinjection of CapG had no effect on bacterial movement. Cultured skin fibroblasts derived from gelsolin-null mice were capable of supporting intracellular
Listeria
motility at velocities comparable to those supported by wild-type skin fibroblasts. These experiments demonstrated that the surface of
Listeria
contains a polymerization zone that can block the barbed-end-capping activity of both gelsolin and CapG. The ability of
Listeria
to uncap actin filaments combined with the severing activity of gelsolin can accelerate actin-based motility. However, gelsolin is not absolutely required for the actin-based intracellular movement of
Listeria
because its function can be replaced by other actin regulatory proteins in gelsolin-null cells, demonstrating the functional redundancy of the actin system.
Passive Immunization with Antibodies against Three Distinct Epitopes onPlasmodium yoeliiMerozoite Surface Protein 1 Suppresses Parasitemia
Authors: Spencer Valero Lilian M. , Ogun Solabomi A. , Fleck Suzanne L. , Ling Irene T. , Scott-Finnigan Terry J. , Blackman Michael J. , Holder Anthony A. 
Published: December 2019

ABSTRACTWe have produced monoclonal antibodies againstPlasmodium yoeliimerozoite surface protein 1 (MSP-1) and have assessed their ability to suppress blood stage parasitemia by passive immunization. Six immunoglobulin G antibodies were characterized in detail: three (B6, D3, and F5) were effective in suppressing a lethal blood stage challenge infection, two (B10 and G3) were partially effective, and one (B4) was ineffective. MSP-1 is the precursor to a complex of polypeptides on the merozoite surface; all of the antibodies bound to this precursor and to an ∼42-kDa fragment (MSP-142) that is derived from the C terminus of MSP-1. MSP-142is further cleaved to an N-terminal ∼33-kDa polypeptide (MSP-133) and a C-terminal ∼19-kDa polypeptide (MSP-119) comprised of two epidermal growth factor (EGF)-like modules. D3 reacted with MSP-142but not with either of the constituents MSP-133and MSP-119, B4 recognized an epitope within the N terminus of MSP-133, and B6, B10, F5, and G3 bound to MSP-119. B10 and G3 bound to epitopes that required both C-terminal EGF-like modules for their formation, whereas B6 and F5 bound to epitopes in the first EGF-like module. These results indicate that at least three distinct epitopes onP. yoeliiMSP-1 are recognized by antibodies that suppress parasitemia in vivo.
Phospholipase A of
Yersinia enterocolitica
Contributes to Pathogenesis in a Mouse Model
Authors: Schmiel D. H. , Wagar E. , Karamanou L. , Weeks D. , Miller V. L. 
Published: December 2019

ABSTRACT

Some isolates of
Yersinia enterocolitica
exhibit phospholipase activity, which has been linked to lecithin-dependent hemolysis (M. Tsubokura, K. Otsoki, I. Shimohira, and H. Yamamoto, Infect. Immun. 25:939–942, 1979). A gene encoding
Y. enterocolitica
phospholipase was identified, and analysis of the nucleotide sequence revealed two tandemly transcribed open reading frames. The first,
yplA
, has 74% identity and 85% similarity to the phospholipase A found in
Serratia liquefaciens
. Though the other,
yplB
, was less similar to the downstream accessory protein found in
S. liquefaciens
, the organization in both species is similar. Subsequently, a
yplA
-null
Y. enterocolitica
strain, YEDS10, was constructed and demonstrated to be phospholipase negative by plate and spectrophotometric assays. To ascertain whether the phospholipase has a role in pathogenesis, YEDS10 was tested in the mouse model. In experiments with perorally infected BALB/c mice, fewer YEDS10 organisms were recovered from the mesenteric lymph nodes and Peyer’s patches (PP) than the parental strain at 3 or 5 days postinfection. Furthermore, bowel tissue and PP infected with YEDS10 appeared to be less inflamed than those infected with the parental strain. When extremely high doses of both the parental and YEDS10 strains were given, similar numbers of viable bacteria were recovered from the PP and mesenteric lymph nodes on day 3. However, the numbers of foci and the extent of inflammation and necrosis within them were noticeably less for YEDS10 compared to the parental strain. Together these findings suggest that
Y. enterocolitica
produces a phospholipase A which has a role in pathogenesis.
Use of Monoclonal Antibodies To Identify Phospholipase C as the Enterotoxic Factor of the Bifunctional Hemolysin-Phospholipase C Molecule of
Vibrio cholerae
O139
Authors: Pal Sangita , Datta Archana , Nair G. Balakrish , Guhathakurta Bhakti 
Published: December 2019

ABSTRACT

Two hybrid clones producing monoclonal antibodies (MAbs) raised against the purified enterotoxic hemolysin-phospholipase C (HlyPC) bifunctional molecule of a
Vibrio cholerae
O139 strain were used to study its enterotoxicity in relation to its hemolytic and enzymatic activities. Fab fragments of MAbs from ascites produced by the two hybrids neutralized the hemolytic activity of HlyPC, leaving the enzymatic activity unaffected. In ligated rabbit ileal loop and infant mouse intestine, the Fab fragments of the MAbs were not able to neutralize the enterotoxicity of HlyPC, suggesting that PC rather than Hly is the enterotoxic moiety of the molecule. The enterotoxicity of the purified PC molecule isolated from an Hly
−
spontaneous mutant of the HlyPC-producing parent strain further confirms this contention. The Hly molecule isolated from a PC
−
mutant was not diarrheagenic.