bluuebunny/crossref_metadata_2025_split huggingface dataset:
M Protein of the Group AStreptococcusBinds to the Seventh Short Consensus Repeat of Human Complement Factor H
Authors: Blackmore Timothy K. , Fischetti Vincent A. , Sadlon Tania A. , Ward Helena M. , Gordon David L. 
Published: December 2019

ABSTRACTStreptococcus pyogenesevades complement by binding the complement-regulatory protein factor H (fH) via the central conserved C-repeat region of M protein. However, the corresponding binding region within fH has not previously been precisely localized. fH is composed of 20 conserved modules called short consensus repeats (SCRs), each of which contains approximately 60 amino acids. A series of fH truncated and deletion mutants were prepared, and their interaction with M6 protein was examined. The M protein binding site was initially localized to SCRs 6 to 15 as demonstrated by ligand dot blotting, chemical cross-linking, and enzyme-linked immunosorbent assay. SCR 7 was then shown to contain the M protein binding site, as a construct consisting of the first seven SCRs bound M protein but a construct containing the first six SCRs did not bind. In addition, deletion of SCR 7 from full-length fH abolished binding to M protein. SCR 7 is known to contain a heparin binding domain, and binding of fH to M6 protein was almost totally inhibited in the presence of 400 U of heparin per ml. These results localize the M6 protein binding site of fH to SCR 7 and indicate that it is in close proximity to the heparin binding site.
Signal Transduction Pathways Involved in EnterohemorrhagicEscherichia coli-Induced Alterations in T84 Epithelial Permeability
Authors: Philpott Dana J. , McKay Derek M. , Mak Walter , Perdue Mary H. , Sherman Philip M. 
Published: December 2019

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) infection is associated with watery diarrhea and can lead to complications, including hemorrhagic colitis and the hemolytic-uremic syndrome. The mechanisms by which these organisms produce diarrheal disease remain to be elucidated. Changes in T84 epithelial cell electrophysiology were examined following EHEC infection. T84 cell monolayers infected with EHEC O157:H7 displayed a time-dependent decrease in transepithelial resistance. Increases in the transepithelial flux of both [3H]mannitol and51Cr-EDTA accompanied the EHEC-induced decreases in T84 resistance. Altered barrier function induced by EHEC occurred at the level of the tight junction since immunofluorescent staining of the tight-junction-associated protein ZO-1 was disrupted when examined by confocal microscopy. Decreased resistance induced by EHEC involved a protein kinase C (PKC)-dependent pathway as the highly specific PKC inhibitor, CGP41251, abrogated the EHEC-induced drop in resistance. PKC activity was also increased in T84 cells infected with EHEC. Calmodulin and myosin light chain kinase played a role in EHEC-induced resistance changes as inhibition of these effector molecules partially reversed the effects of EHEC on barrier function. These studies demonstrate that intracellular signal transduction pathways activated following EHEC infection link the increases in T84 epithelial permeability induced by this pathogen.
Protective Effects of a Human 18-Kilodalton Cationic Antimicrobial Protein (CAP18)-Derived Peptide against Murine Endotoxemia
Authors: Kirikae Teruo , Hirata Michimasa , Yamasu Hiromi , Kirikae Fumiko , Tamura Hiroshi , Kayama Fumio , Nakatsuka Keisuke , Yokochi Takashi , Nakano Masayasu 
Published: December 2019

ABSTRACTCAP18 (an 18-kDa cationic antimicrobial protein) is a granulocyte-derived protein that can bind lipopolysaccharide (LPS) and inhibit various activities of LPS in vitro. The present study examined the protective effect of a synthetic 27-amino-acid peptide (CAP18109–135) from the LPS-binding domain of CAP18 against antibiotic-induced endotoxin shock, using highly LPS-sensitived-(+)-galactosamine (d-GalN)-sensitized C3H/HeN mice. The antibiotic-induced endotoxin (CAZ-endotoxin) was prepared from the culture filtrate ofPseudomonas aeruginosaPAO1 exposed to ceftazidime (CAZ). Injection of CAP18109–135protected the mice injected with LPS or CAZ-endotoxin from death and lowered their tumor necrosis factor (TNF) levels in serum in a dose-dependent manner. Treatment with CAZ caused death of thed-GalN-sensitizedP. aeruginosaPAO-infected mice within 48 h, while injection with CAP18109–135rescued the mice from death. In the mice rescued from death by injection with CAP18109–135, endotoxin levels in plasma and TNF production by liver tissues were decreased but the numbers of viable infecting bacteria in their blood were not decreased significantly and remained at the levels in CAZ-treated mice. These results indicate that CAP18109–135is capable of preventing antibiotic-induced endotoxic shock in mice with septicemia and that the effect is due to its LPS-neutralizing activity rather than to its antibacterial activity.
Identification of
Salmonella typhimurium
Genes Required for Colonization of the Chicken Alimentary Tract and for Virulence in Newly Hatched Chicks
Authors: Turner Arthur K. , Lovell Margaret A. , Hulme Scott D. , Zhang-Barber Li , Barrow Paul A. 
Published: December 2019

ABSTRACT

From a collection of 2,800 Tn
5
-TC1 transposon mutants of
Salmonella typhimurium
F98, 18 that showed reduced intestinal colonization of 3-week-old chicks were identified. The sites of transposon insertion were determined for most of the mutants and included insertions in the lipopolysaccharide biosynthesis genes
rfaK
,
rfaY
,
rfbK
, and
rfbB
and the genes
dksA
,
clpB
,
hupA
, and
sipC
. In addition, identification was made of an insertion into a novel gene that encodes a protein showing similarity to the IIC component of the mannose class of phosphoenolpyruvate-carbohydrate phosphotransferase systems, which we putatively called
ptsC
. Transduction of most of the transposon mutations to a fresh
S. typhimurium
F98 genetic background and construction of defined mutations in the
rfbK
,
dksA
,
hupA
,
sipC
, and
ptsC
genes of
S. typhimurium
F98 supported the role in colonization of all but the
pts
locus. The virulence of the
rfbK
,
dksA
,
hupA
,
sipC
, and
ptsC
defined mutants and
clpB
and
rfaY
transductants in 1-day-old chicks was tested. All but the
ptsC
and
rfaY
mutants were attenuated for virulence. A number of other phenotypes associated with some of the mutations are described.
Immunohistological Localization of the MrkD Adhesin in the Type 3 Fimbriae of
Klebsiella pneumoniae
Authors: Tarkkanen Ann-Mari , Westerlund-Wikström Benita , Erkkilä Leena , Korhonen Timo K. 
Published: December 2019

ABSTRACT

The adhesive minor protein MrkD of the type 3 fimbria of
Klebsiella pneumoniae
was expressed and purified from
Escherichia coli
as a fusion protein with an N-terminal polyhistidine tail. Polyclonal antibodies raised against MrkD specifically recognized the MrkD peptide in Western blots of fimbrial preparations. Immunoelectron microscopic analyses showed that the anti-MrkD immunoglobulins bound to the tip of the plasmid-encoded variant of the type 3 fimbria of
K. pneumoniae
, whereas no binding to the chromosomally encoded MrkD-deficient type 3 fimbrial variant of
K. pneumoniae
was detected. Immunoglobulins from an antiserum raised against purified type 3 fimbrial filaments bound laterally to both type 3 fimbrial variants. The anti-MrkD antibodies also bound to the tip of a
papG
deletion derivative of the
E. coli
P fimbria complemented with
mrkD
, indicating that MrkD structurally complements a PapG mutation in the P fimbria of
E. coli.
Biophysical Characterization of the Stability of the 150-Kilodalton Botulinum Toxin, the Nontoxic Component, and the 900-Kilodalton Botulinum Toxin Complex Species
Authors: Chen Flora , Kuziemko Geoffrey M. , Stevens Raymond C. 
Published: December 2019

ABSTRACT

Botulinum neurotoxin serotype A is initially released from the bacterium
Clostridium botulinum
as a stable 900-kDa complex. The serotype A 900-kDa complex is one of the forms of the toxin being used as a therapeutic agent for the treatment of various neuromuscular disorders. Previous experiments have demonstrated that the 900-kDa complex form of the toxin protects the toxin from the harsh conditions of the gastrointestinal tract. To provide molecular level details of the stability and equilibrium of the 900-kDa complex, the nontoxic component, and the toxic (botulinum neurotoxin) component, the three species have been investigated with a series of biophysical techniques at the molecular level (dynamic light scattering, proteolysis, circular dichroism, pH incubations, and agglutination assays). These experiments were conducted under harsh conditions which mimic those found along the gastrointestinal tract. Separately, exposure to denaturing and proteolytic conditions degrades both the botulinum neurotoxin and the nontoxic component. In the 900-kDa complex, the botulinum neurotoxin is protected during exposure to the gastrointestinal environment and the nontoxic component is slightly modified. Surprisingly, the toxin protects the ability of the nontoxic component to agglutinate erythrocytes. Contrary to previous reports, the purified 900-kDa complex did not have agglutination ability until after exposure to the proteolytic conditions. These experiments provide new evidence and detail for the theory that the nontoxic component and the toxic component protect one another during exposure to harsh conditions, and a molecular model is presented for the passage of the toxin through the gastrointestinal tract.
Borrelia burgdorferiEscape Mutants That Survive in the Presence of Antiserum to the OspA Vaccine Are Killed When Complement Is Also Present
Authors: Solé Mónica , Bantar Carlos , Indest Karl , Gu Yan , Ramamoorthy Ramesh , Coughlin Richard , Philipp Mario T. 
Published: December 2019

ABSTRACTAs an initial attempt to investigate the possible role of outer surface protein A (OspA) escape mutants ofBorrelia burgdorferiin decreasing the efficacy of the OspA vaccine, mutants of the HB19 strain ofB. burgdorferisensu stricto were selected in vitro from an uncloned, low-passage-number isolate. The antiserum used for selection was obtained from rhesus monkeys that had been given a vaccine of the same formulation and dose, and by the same route of administration, as that given to humans in several trials. All of the mutants selected in liquid medium and subsequently cloned twice in solid medium expressed a single abundant protein of 28 to 34 kDa instead of both OspA and OspB. Depending on the mutant, this protein reacted strongly, weakly, or not detectably with the anti-OspA antibody used for selection. Analysis of theospABlocus of each of four representatives from these three groups of mutants by PCR with oligonucleotide primers that hybridize to flanking regions of theospABoperon, and of the corresponding phenotype with monoclonal antibodies that bind to the amino or carboxyl terminus of the OspA or OspB polypeptide, indicated that in all cases a deletion within the operon had occurred. Spirochetes from the four mutant strains chosen for further analysis could be killed in antibody-dependent, complement-mediated killing assays with the selecting anti-OspA antibody, despite their resistance to killing with this antibody in the absence of complement. Complement-mediated killing occurred at an antibody concentration higher than that required to kill wild-type spirochetes. If anti-OspA antibody acts only within the tick, where complement is probably ineffective due to tick-derived decomplementing factors, then OspA escape mutants, if infectious, could seriously diminish the efficacy of OspA vaccines. On the other hand, if the killing ofB. burgdorferiwith anti-OspA antibody also takes place within the human host, then our results indicate that chimeric/deletion escape mutants will be killed as well.
A Fibrinogen-Binding Protein of
Staphylococcus epidermidis
Authors: Nilsson Martin , Frykberg Lars , Flock Jan-Ingmar , Pei Lei , Lindberg Martin , Guss Bengt 
Published: December 2019

ABSTRACT

The present study reports on fibrinogen (Fg) binding of
Staphylococcus epidermidis
. Adhesion of different
S. epidermidis
strains to immobilized Fg was found to vary significantly between different strains, and the component responsible was found to be proteinaceous in nature. To further characterize the Fg-binding activity, a shotgun phage display library covering the
S. epidermidis
chromosome was constructed. By affinity selection (panning) against immobilized Fg, a phagemid clone, pSEFG1, was isolated, which harbors an insert with an open reading frame of ∼1.7 kilobases. Results from binding and inhibition experiments demonstrated that the insert of pSEFG1 encodes a specific Fg-binding protein. Furthermore, affinity-purified protein encoded by pSEFG1 completely inhibited adhesion of
S. epidermidis
to immobilized Fg. By additional cloning and DNA sequence analyses, the complete gene, termed
fbe
, was found to consist of an open reading frame of 3,276 nucleotides encoding a protein, called Fbe, with a deduced molecular mass of ∼119 kDa. With a second phage display library made from another clinical isolate of
S. epidermidis
, it was possible to localize the Fg-binding region to a 331-amino-acid-long fragment. PCR analysis showed that the
fbe
gene was found in 40 of 43 clinical isolates of
S. epidermidis
. The overall organization of Fbe resembles those of other extracellular surface proteins of staphylococci and streptococci. Sequence comparisons with earlier known proteins revealed that this protein is related to an Fg-binding protein of
Staphylococcus aureus
called clumping factor.
Enhanced Levels of
Staphylococcus aureus
Stress Protein GroEL and DnaK Homologs Early in Infection of Human Epithelial Cells
Authors: Qoronfleh M. Walid , Bortner Carol A. , Schwartzberg Paul , Wilkinson Brian J. 
Published: December 2019

ABSTRACT

Antibodies to
Staphylococcus aureus
heat shock proteins (Hsps) are present in the sera of patients with
S. aureus
endocarditis (M. W. Qoronfleh, W. Weraarchakul, and B. J. Wilkinson, Infect. Immun. 61:1567–1570, 1993). Although these proteins are immunogenic, their role in infection has not been established. We developed a cell culture system as a model to examine the potential involvement of staphylococcal Hsps in the initial events of infection. This study supports a model in which a clinical endocarditis isolate responds to host cell signals by selectively regulating the synthesis of numerous proteins, including the stress proteins Hsp60 (GroEL homolog) and Hsp70 (DnaK homolog) and a unique 58-kDa protein.
Phenotypic Effect of IsogenicuspA1anduspA2Mutations onMoraxella catarrhalis035E
Authors: Aebi Christoph , Lafontaine Eric R. , Cope Leslie D. , Latimer Jo L. , Lumbley Sheryl L. , McCracken George H. , Hansen Eric J. 
Published: December 2019

ABSTRACTThe UspA surface antigen ofMoraxella catarrhaliswas recently shown to be comprised of two different proteins (UspA1 and UspA2) which share an internal region containing 140 amino acids with 93% identity (C. Aebi, I. Maciver, J. L. Latimer, L. D. Cope, M. K. Stevens, S. E. Thomas, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 65:4367–4377, 1997). IsogenicuspA1,uspA2, anduspA1 uspA2mutants were tested in a number of in vitro systems to determine what effect these mutations, either individually or together, might exert on the phenotype ofM. catarrhalis035E. Monoclonal antibodies specific for UspA1 or UspA2 were used in an indirect antibody accessibility assay to prove that both of these proteins were expressed on the surface ofM. catarrhalis. All three mutants grew in vitro at the same rate and did not exhibit autoagglutination or hemagglutination properties that were detectably different from those of the wild-type parent strain. When tested for the ability to adhere to human epithelial cells, the wild-type parent strain and theuspA2mutant readily attached to Chang conjunctival cells. In contrast, theuspA1mutant and theuspA1 uspA2double mutant both attached to these epithelial cells at a level nearly 2 orders of magnitude lower than that obtained with the wild-type parent strain, a result which suggested that expression of UspA1 byM. catarrhalisis essential for attachment to these epithelial cells. Both the wild-type parent strain and theuspA1mutant were resistant to the bactericidal activity of normal human serum, whereas theuspA2mutant and theuspA1 uspA2double mutant were readily killed by this serum. This latter result indicated that the presence of UspA2 is essential for expression of serum resistance byM. catarrhalis.
Immune Responses against Major Outer Membrane Antigens of
Neisseria meningitidis
in Vaccinees and Controls Who Contracted Meningococcal Disease during the Norwegian Serogroup B Protection Trial
Authors: Wedege E. , Høiby E. A. , Rosenqvist E. , Bjune G. 
Published: December 2019

ABSTRACT

Sera from vaccinees and controls who contracted serogroup B meningococcal disease during the blinded and open parts of a two-dose protection trial in Norway were compared for antigen-specific and bactericidal antibodies against vaccine strain 44/76 (B:15:P1.7,16). From 16 of 20 (80%) vaccinees and 26 of 35 (74%) controls, one or more serum samples (
n
= 104) were collected during the acute phase (1 to 4 days), early convalescent phase (5 to 79 days), and late convalescent phase (8 to 31 months) after onset of disease. Binding of immunoglobulin G (IgG) to the major outer membrane antigens (80- and 70-kDa proteins, class 1, 3, and 5 proteins, and lipopolysaccharide [LPS]) on immunoblots was measured by digital image analysis. Specific IgG levels in vaccinees increased from acute to early convalescent phases, followed by a decline, while controls showed a small increase over time. Vaccinees had significantly higher levels than controls against class 1 and 3 porins and LPS in acute sera, against all antigens during early convalescence, and against class 1 and 3 porins in the later sera. Vaccinees who were infected with strains expressing subtype P1.7,16 proteins demonstrated a level of IgG binding to protein P1.7,16 with early-convalescent-phase sera that was fourfold higher than that of those infected with other strains. Bactericidal titers in serum against the vaccine strain were 192-fold higher for vaccinees than those for controls during early convalescence, but similarly low levels were found during late convalescence. A vaccine-induced anamnestic response of specific and functional antibody activities was thus shown, but the decrease in protection over time after vaccination indicated that two vaccine doses did not induce sufficient levels of long-term protective antibodies.
The
inlA
Gene of
Listeria monocytogenes
LO28 Harbors a Nonsense Mutation Resulting in Release of Internalin
Authors: Jonquières Renaud , Bierne Hélène , Mengaud Jérôme , Cossart Pascale 
Published: December 2019

ABSTRACT

Internalin is a surface protein that mediates entry of
Listeria monocytogenes
EGD into epithelial cells expressing the cell adhesion molecule human E-cadherin or its chicken homolog, L-CAM, which act as receptors for internalin. After observing that entry of
L. monocytogenes
LO28 into S180 fibroblasts, in contrast to that of EGD, did not increase after transfection with L-CAM, we examined both the expression and the structure of internalin in strain LO28. We discovered a nonsense mutation in
inlA
which results in a truncated protein released in the culture medium. Mutations leading to release of internalin were also detected in clinical and food isolates. These results question the role of internalin as a virulence factor in murine listeriosis.
Multigene Families Encoding the Major Hemagglutinins in Phylogenetically Distinct Mycoplasmas
Authors: Noormohammadi A. H. , Markham P. F. , Duffy M. F. , Whithear K. G. , Browning G. F. 
Published: December 2019

ABSTRACT

Mycoplasma synoviae
has two major membrane antigens, MSPA and MSPB, both of which are phase variable and which may be coordinately involved in adhesion of the organism to erythrocytes. A single gene (
vlhA
) from
M. synoviae
was characterized, and polypeptides were expressed from nonoverlapping 5′ and 3′ regions in
Escherichia coli
. The expression product of the
vlhA
5′ region reacted with specific reagents against MSPB, while that of the 3′ region reacted with specific reagents against MSPA. Analysis of the predicted amino acid sequence showed a characteristic signal peptidase II cleavage site, and the presence of the acylation site was confirmed by identification of a lipid-associated membrane protein, similar in molecular mass to MSPB, in [
3
H]palmitate-labelled membrane proteins. Further sequence analysis of the
vlhA
gene revealed a high identity with the
Mycoplasma gallisepticum
pMGA1.7 gene, a member of a large translated family. The
vlhA
gene was shown to hybridize to multiple restriction fragments of the
M. synoviae
genome, suggesting that it was also a member of a multigene family. These findings indicate that coordinate phase variation of the two major surface antigens of
M. synoviae
WVU may be due to their expression from the same gene and that homologous gene families encode the major hemagglutinins of two phylogenetically distinct mycoplasmas. The presence of homologous multigene families in such phylogenetically distinct species, but not in the genomes of more closely related species, suggests that the families may have been transferred horizontally.
Interleukin-9 Enhances Resistance to the Intestinal NematodeTrichuris muris
Authors: Faulkner Helen , Renauld J.-C. , Van Snick J. , Grencis R. K. 
Published: December 2019

ABSTRACTUpon infection with the cecum-dwelling nematodeTrichuris muris, the majority of inbred strains of mice launch a Th2-type immune response and in doing so expel the parasite before patency. In contrast, there are a few mouse strains which develop a nonprotective Th1-type response resulting in a chronic infection and the presence of adult worms. Of the Th2 cytokines known to be associated with the resistant phenotype (interleukin-4 [IL-4], IL-5, IL-9, and IL-13), comparatively little is known about the contribution that IL-9 makes towards the protective immune response. In this study we demonstrate that IL-9 is expressed early during the Th2-type response and that its elevation in vivo results in the enhancement of intestinal mastocytosis and the production of both the immunoglobulin E (IgE) and IgG1 isotypes. In addition, elevated IL-9 levels in vivo facilitated the loss ofT. murisfrom the intestine. That IL-9 is important in promoting worm expulsion was also seen following infection of IL-9-transgenic mice, which constitutively overexpress the cytokine. These animals displayed an extremely rapid, but immune mediated, expulsion of the parasite. Also evident in these animals was a pronounced intestinal mastocytosis, which was previously shown by us to be responsible for the expulsion of the related nematodeTrichinella spiralisfrom these animals. Taken together with observations of IL-9 production following infection with other helminths, the results imply that IL-9 contributes to the general mast cell and IgE response characteristic of these infections and, more specifically, enhances resistance toT. muris.