bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histoplasma capsulatum
Strain Variation in Both H Antigen Production and β-Glucosidase Activity and Overexpression of
HAG1
from a Telomeric Linear Plasmid
Authors: Fisher Kimber L. , Deepe George S. , Woods Jon P. 
Published: December 2019

ABSTRACT

The H antigen of the dimorphic fungal pathogen
Histoplasma capsulatum
was first described over 40 years ago. It is a secreted glycoprotein that is immunogenic during infection. Recent cloning of the H antigen gene (
HAG1
) indicated sequence homology with genes for fungal β-glucosidases. To understand the biological role of this immunodominant antigen in
H. capsulatum
, enzymatic assays were performed to determine whether
H. capsulatum
contained a β-glucosidase enzyme activity and whether this activity was encoded by the
HAG1
gene. Substrate gels with
H. capsulatum
culture supernatants revealed β-glucosidase activity near the predicted mobility of the H antigen. Quantitative microtiter plate assays revealed marked differences in secreted β-glucosidase activities from three
H. capsulatum
restriction fragment length polymorphism (RFLP) classes, with RFLP class II strains displaying high levels of enzyme activity, in contrast to the low levels of activity exhibited by class I and III strains. Immunoblotting of culture supernatants with an H antigen-specific antiserum demonstrated differences in H protein expression levels between the
H. capsulatum
classes, with a correlation between secreted enzyme activity and H protein levels. We took advantage of these class differences to demonstrate multicopy plasmid H gene overexpression by transformation of an
HAG1
plasmid into
H. capsulatum
. Both a class II strain (G217B
ura5-23
) and a class III strain (G184AS
ura5-11
) transformed with the telomeric overexpression plasmid pMAD401 displayed increased levels of β-glucosidase enzyme activity and H protein expression compared to the levels in control transformants containing only the single genomic copy of
HAG1
. This is the first demonstration of telomeric plasmid-mediated protein overexpression in this pathogenic fungus, and the findings support the identification of the H antigen as a β-glucosidase.
Biased Immunoglobulin G1 Isotype Responses Induced in Cattle with DNA Expressingmsp1a ofAnaplasma marginale
Authors: Arulkanthan Appudurai , Brown Wendy C. , McGuire Travis C. , Knowles Donald P. 
Published: December 2019

ABSTRACTImmunization with the native major surface protein 1 (MSP1) (a heterodimer containing disulfide and noncovalently bonded polypeptides designated MSP1a and MSP1b) of the erythrocytic stage ofAnaplasma marginaleconferred protection against homologous challenge (G. H. Palmer, A. F. Barbet, W. C. Davis, and T. C. McGuire, Science 231:1299–1302, 1986). The MSP1a polypeptide possesses a conserved neutralization-sensitive epitope. In the present study, the immune response to DNA-mediated immunization usingmsp1a was studied. The plasmid pVCL/MSP1a, which encodes the completemsp1a gene ofA. marginaleunder the control of human cytomegalovirus immediate-early enhancer/promoter and intron A, was constructed. The immune responses elicited by immunization with pVCL/MSP1a into cardiotoxin-induced regenerating muscle were evaluated in mice and cattle. Antibody reactive with native MSP1a was detected in pooled sera of immunized BALB/c mice 3 weeks following primary immunization. Two calves seronegative forA. marginalewere immunized four times, at weeks 0, 3, 7, and 13, with pVCL/MSP1a. By 8 weeks, both calves responded to MSP1a with an antibody titer of 1:100, which peaked at 1:1,600 and 1:800 by 16 weeks after the initial immunization. Interestingly, immunoblotting with anti-immunoglobulin G1 (anti-IgG1) and anti-IgG2 specific monoclonal antibodies revealed a restricted IgG1 anti-MSP1a response in both animals. T-lymphocyte lines, established after the fourth immunization, proliferated specifically againstA. marginalehomogenate and purified MSP1 in a dose-dependent manner. These data provide a basis for an immunization strategy to direct bovine immune responses by using DNA vaccine vectors containing single or multiple genes encoding major surface proteins ofA. marginale.
Four Clones of
Borrelia burgdorferi
Sensu Stricto Cause Invasive Infection in Humans
Authors: Seinost Gerald , Dykhuizen Daniel E. , Dattwyler Raymond J. , Golde William T. , Dunn John J. , Wang Ing-Nang , Wormser Gary P. , Schriefer Martin E. , Luft Benjamin J. 
Published: December 2019

ABSTRACT

Lyme disease begins at the site of a tick bite, producing a primary infection with spread of the organism to secondary sites occurring early in the course of infection. A major outer surface protein expressed by the spirochete early in infection is outer surface protein C (OspC). In
Borrelia burgdorferi
sensu stricto, OspC is highly variable. Based on sequence divergence, alleles of
ospC
can be divided into 21 major groups. To assess whether strain differences defined by
ospC
group are linked to invasiveness and pathogenicity, we compared the frequency distributions of major
ospC
groups from ticks, from the primary erythema migrans skin lesion, and from secondary sites, principally from blood and spinal fluid. The frequency distribution of
ospC
groups from ticks is significantly different from that from primary sites, which in turn is significantly different from that from secondary sites. The major groups A, B, I, and K had higher frequencies in the primary sites than in ticks and were the only groups found in secondary sites. We define three categories of major
ospC
groups: one that is common in ticks but very rarely if ever causes human disease, a second that causes only local infection at the tick bite site, and a third that causes systemic disease. The finding that all systemic
B. burgdorferi
sensu stricto infections are associated with four
ospC
groups has importance in the diagnosis, treatment, and prevention of Lyme disease.
Obligatory Role of Gamma Interferon for Host Survival in a Murine Model of Infection withBurkholderia pseudomallei
Authors: Santanirand P. , Harley V. S. , Dance D. A. B. , Drasar B. S. , Bancroft G. J. 
Published: December 2019

ABSTRACTBurkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative bacterium capable of causing either acute lethal sepsis or chronic but eventually fatal disease in infected individuals. However, despite the clinical importance of this infection in areas where it is endemic, there is essentially no information on the mechanisms of protective immunity to the bacterium. We describe here a murine model of either acute or chronic infection withB. pseudomalleiin Taylor Outbred (TO) mice which mimics many features of the human pathology. Intraperitoneal infection of TO mice at doses of >106CFU resulted in acute septic shock and death within 2 days. In contrast, at lower doses mice were able to clear the inoculum from the liver and spleen over a 3- to 4-week period, but persistence of the organism at other sites resulted in a chronic infection of between 2 and 16 months duration which was eventually lethal in all of the animals tested. Resistance to acute infection withB. pseudomalleiwas absolutely dependent upon the production of gamma interferon (IFN-γ) in vivo. Administration of neutralizing monoclonal antibody against IFN-γ lowered the 50% lethal dose from >5 × 105to ca. 2 CFU and was associated with 8,500- and 4,400-fold increases in the bacterial burdens in the liver and spleen, respectively, together with extensive destruction of lymphoid architecture in the latter organ within 48 h. Neutralization of either tumor necrosis factor alpha or interleukin-12 but not granulocyte-macrophage colony-stimulating factor, also increased susceptibility to infection in vivo. Together, these results provide the first evidence of a host protective mechanism againstB. pseudomallei. The rapid production of IFN-γ within the first day of infection determines whether the infection proceeds to an acute lethal outcome or becomes chronic.
Human Monoclonal Immunoglobulin M Antibodies to Ganglioside GM1Show Diverse Cross-Reactivities with Lipopolysaccharides ofCampylobacter jejuniStrains Associated with Guillain-Barré Syndrome
Authors: Prendergast Martina M. , Willison Hugh J. , Moran Anthony P. 
Published: December 2019

ABSTRACTWe examined the reactivity of a panel of anti-GM1immunoglobulin M monoclonal antibodies (MAbs) cloned from multifocal motor neuropathy patients with lipopolysaccharides (LPSs) ofCampylobacter jejunistrains, including serotype O:41 strains associated with Guillain-Barré syndrome. The MAbs reacted with ganglioside GM1to different degrees, and these differences in fine specificities for GM1were reflected in the different degrees of reactivity with each of theC. jejuniLPSs tested. Antibodies could also be discriminated by the varying patterns of inhibition by cholera toxin (a GM1ligand) in LPS binding studies. These results indicate that there is a substantial heterogeneity amongC. jejuniO:41 strains in their expression of GM1-like epitopes and among the fine specificities of different neuropathy-associated anti-GM1antibodies.
Lipopolysaccharide-Induced Tumor Necrosis Factor Alpha Production by Human Monocytes Involves the Raf-1/MEK1-MEK2/ERK1-ERK2 Pathway
Authors: van der Bruggen Tjomme , Nijenhuis Suzanne , van Raaij Estia , Verhoef Jan , Sweder van Asbeck B. 
Published: December 2019

ABSTRACTDuring gram-negative sepsis, human monocytes are triggered to produce large quantities of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) in response to endotoxin (lipopolysaccharide [LPS]). Several studies have identified signal transduction pathways that are activated by LPS, including activation of nuclear factor-κB (NF-κB) and activation of mitogen-activated protein kinases (MAPKs), including ERK1 and ERK2, c-Jun N-terminal kinase, and p38. In this study, the relevance of ERK1 and ERK2 activation for LPS-induced TNF-α production by primary human monocytes has been addressed with PD-098059, which specifically blocks activation of MAPK kinase (MEK) by Raf-1. TNF-α levels in the monocyte culture supernatant, induced by 10 ng of LPS/ml, were reduced by PD-098059 (50 μM). In addition, PD-098059 also reduced TNF-α mRNA expression when cells were stimulated for 1 h with LPS. On the other hand, LPS-induced interleukin-10 (IL-10) levels in the monocyte supernatant were only slightly inhibited by PD-098059. Ro 09-2210, a recently identified MEK inhibitor, completely abrogated TNF-α levels at nanomolar concentrations. IL-10 levels also were strongly reduced. To show the efficacy of PD-098059 and Ro 09-2210, ERK1 and -2 activation was monitored by Western blotting with an antiserum that recognizes the phosphorylated (i.e., activated) forms of ERK1 and ERK2. Addition of LPS to human monocytes resulted in activation of both ERK1 and ERK2 in a time- and concentration (50% effective concentration between 1 and 10 ng of LPS/ml)-dependent manner. Activation of ERK2 was blocked by PD-098059 (50 μM), whereas ERK1 seemed to be less affected. Ro 09-2210 completely prevented LPS-induced ERK1 and ERK2 activation. LPS-induced p38 activation also was prevented by Ro 09-2210. These data further support the view that the ERK signal transduction pathway is causally involved in the synthesis of TNF-α by human monocytes stimulated with LPS.
Cloning, Sequencing, and Role in Virulence of Two Phospholipases (A1 and C) from Mesophilic
Aeromonas
sp. Serogroup O:34
Authors: Merino Susana , Aguilar Alicia , Nogueras Maria Mercedes , Regue Miguel , Swift Simon , Tomás Juan M. 
Published: December 2019

ABSTRACT

Two different representative recombinant clones encoding
Aeromonas hydrophila
lipases were found upon screening on tributyrin (phospholipase A1) and egg yolk agar (lecithinase-phospholipase C) plates of a cosmid-based genomic library of
Aeromonas hydrophila
AH-3 (serogroup O34) introduced into
Escherichia coli
DH5α. Subcloning, nucleotide sequencing, and in vitro-coupled transcription-translation experiments showed that the phospholipase A1 (
pla
) and C (
plc
) genes code for an 83-kDa putative lipoprotein and a 65-kDa protein, respectively. Defined insertion mutants of
A. hydrophila
AH-3 defective in either
pla
or
plc
genes were defective in phospholipase A1 and C activities, respectively. Lecithinase (phospholipase C) was shown to be cytotoxic but nonhemolytic or poorly hemolytic.
A. hydrophila
AH-3
plc
mutants showed a more than 10-fold increase in their 50% lethal dose on fish and mice, and complementation of the
plc
single gene on these mutants abolished this effect, suggesting that Plc protein is a virulence factor in the mesophilic
Aeromonas
sp. serogroup O:34 infection process.
Activation of Phosphotyrosine Phosphatase Activity Attenuates Mitogen-Activated Protein Kinase Signaling and Inhibits c-FOS and Nitric Oxide Synthase Expression in Macrophages Infected withLeishmania donovani
Authors: Nandan Devki , Lo Raymond , Reiner Neil E. 
Published: December 2019

ABSTRACTIntracellular protozoan parasites of the genusLeishmaniaantagonize host defense mechanisms by interfering with cell signaling in macrophages. In this report, the impact ofLeishmania donovanion mitogen-activated protein (MAP) kinases and nitric oxide synthase (NOS) expression in the macrophage cell line RAW 264 was investigated. Overnight infection of cells with leishmania led to a significant decrease in phorbol-12-myristate-13-acetate (PMA)-stimulated MAP kinase activity and inhibited PMA-induced phosphorylation of the MAP kinase substrate and transcription factor Elk-1. Simultaneously, leishmania infection markedly attenuated the induction of c-FOS and inducible nitric oxide synthase (iNOS) expression in response to PMA and gamma interferon (IFN-γ), respectively. These effects correlated with decreased phosphorylation of p44 and p42 MAP kinases on tyrosine residues. Consistent with the latter finding, lysates prepared from leishmania-infected cells contained an activity that dephosphorylated MAP kinase in vitro, suggesting the possibility of a phosphatase acting in vivo. Attenuation of both MAP kinase activity and c-FOS and iNOS expression was reversed by treatment of macrophages with sodium orthovanadate prior to infection. It was also found that the specific activity of the Src homology 2 domain containing tyrosine phosphatase (SHP-1) toward MAP kinase was markedly increased in leishmania-infected cells. These findings indicate that infection withL. donovaniattenuates MAP kinase signaling and c-FOS and iNOS expression in macrophages by activating cellular phosphotyrosine phosphatases. This may represent a novel mechanism of macrophage deactivation during intracellular infection.
Interleukin-1 and Tumor Necrosis Factor Activities Partially Account for Calvarial Bone Resorption Induced by Local Injection of Lipopolysaccharide
Authors: Chiang Cheng-Yang , Kyritsis George , Graves Dana T. , Amar Salomon 
Published: December 2019

ABSTRACTThe present study was undertaken to test the hypothesis that tumor necrosis factor (TNF) and/or interleukin-1 (IL-1) activity mediates lipopolysaccharide (LPS)-induced bone resorption in vivo. To test this hypothesis,Escherichia coliLPS orPorphyromonas gingivalisLPS was injected into the subcutaneous tissues overlying mouse calvariae. Histological sections, prepared from the center of the lesion, were stained for tartrate-resistant acid phosphatase, and histomorphometric analysis was performed to quantify the osteoclast number and the area of bone resorption. In time course experiments using normal mice, a peak of bone resorption occurred 5 days after endotoxin stimulation. In dose-response experiments, IL-1 receptor type 1 deletion (IL-1R−/−), TNF double-receptor p55/p75 deletion (TNF p55−/−/p75−/−), combined TNF p55 and IL-1 receptor type 1 deletion (TNF p55−/−/IL-1R−/−), and IL-1β-converting enzyme-deficient (ICE−/−) mice and the respective wild-type mice were injected with 500, 100, or 20 μg ofP. gingivalisLPS and sacrificed 5 days after LPS injection. At the highest dose (500 μg), significant decreases in osteoclast number occurred in mutant mice compared to wild-type mice: (i) a 64% reduction for the TNF p55−/−/IL-1R−/−mice, (ii) a 57% reduction for the IL-1R−/−mice, (iii) a 41% reduction for the TNF p55−/−/p75−/−mice, and (iv) a 38% reduction for the ICE−/−mice. At the two lower doses, bone resorption was apparent but no significant differences between mutant and wild-type animals were observed. The present data indicate that at higher doses, LPS-induced bone resorption is substantially mediated by IL-1 and TNF receptor signaling. Furthermore, IL-1 receptor signaling appears to be slightly more important than TNF receptor signaling. At lower LPS doses, other pathways leading to osteoclast activity that are independent of TNF and IL-1 are involved.
Staphylococcus schleiferi
subsp.
schleiferi
Expresses a Fibronectin-Binding Protein
Authors: Peacock S. J. , Lina G. , Etienne J. , Foster T. J. 
Published: December 2019

ABSTRACT

Staphylococcus schleiferi
subsp.
schleiferi
is associated with a range of nosocomial infections, but the pathogenic mechanisms by which these occur are poorly understood. This study provides phenotypic and genotypic evidence for the expression of a cell wall-anchored fibronectin-binding protein by this species.
Intranasal Immunization with Heat-Inactivated
Streptococcus pneumoniae
Protects Mice against Systemic Pneumococcal Infection
Authors: Hvalbye Benedicte K. R. , Aaberge Ingeborg S. , Løvik Martinus , Haneberg Bjørn 
Published: December 2019

ABSTRACT

In order to study the mucosal and serum antibody response to polysaccharide-encapsulated bacteria in mice, a preparation of heat-inactivated
Streptococcus pneumoniae
type 4 was administered, with and without cholera toxin, at various mucosal sites. It appeared that intranasal immunization of nonanesthesized animals was superior to either oral, gastric, or colonic-rectal antigen delivery with regard to the induction of serum immunoglobulin G (IgG) and IgA, as well as saliva IgA antibodies specific for pneumococci. The marked IgA antibody response in feces after intranasal, but not after oral or gastric, immunization is suggestive of a cellular link between the nasal induction site and the distant mucosal effector sites. Intranasal immunization also induced antibodies in serum and in mucosal secretions against type-specific capsular polysaccharide. IgA and IgG antibody levels in pulmonary lavage fluids correlated well with saliva IgA and serum IgG antibodies, respectively. Antibody determinations in pulmonary secretions may therefore be redundant in some cases, and the number of experimental animals may be reduced accordingly. After intraperitoneal challenge with type 4 pneumococci, mice immunized intranasally were protected against both systemic infection and death, even without the use of cholera toxin as a mucosal adjuvant. Thus, an efficient intranasal vaccine against invasive pneumococcal disease may be based on a very simple formulation with whole killed pneumococci.
Secretory Leukocyte Protease Inhibitor Interferes with Uptake of Lipopolysaccharide by Macrophages
Authors: Ding Aihao , Thieblemont Nathalie , Zhu Jing , Jin Fenyu , Zhang Jenny , Wright Samuel 
Published: December 2019

ABSTRACTMacrophages are among the most sensitive targets of bacterial endotoxin (LPS), responding to minute amounts of LPS by releasing a battery of inflammatory mediators. Transfection of macrophages with secretory leukocyte protease inhibitor (SLPI) renders these cells refractory to LPS stimulation. Here we show that uptake of LPS from soluble CD14 (sCD14)-LPS complexes by SLPI-overexpressing cells was only 50% of that seen in control cells. SLPI transfectants and mock transfectants did not differ in the surface expression of CD14 or CD18. We show, in addition, that recombinant human SLPI can bind to purified endotoxin in vitro. SLPI caused a decrease in the binding of LPS to sCD14 as assessed both by fluorescence quenching of labeled LPS and by nondenaturing polyacrylamide gel electrophoresis. These results suggest that the inhibitory effect of SLPI on macrophage responses to LPS may, in part, be due to its blockade of LPS transfer to soluble CD14 and its interference with uptake of LPS from LPS-sCD14 complexes by macrophages.
Functional Studies of a Fibrinogen Binding Protein from
Staphylococcus epidermidis
Authors: Pei Lei , Palma Marco , Nilsson Martin , Guss Bengt , Flock Jan-Ingmar 
Published: December 2019

ABSTRACT

A gene encoding a fibrinogen binding protein from
Staphylococcus epidermidis
was previously cloned, and the nucleotide sequence was determined. A portion of the gene encompassing the fibrinogen binding domain has now been subcloned in an expression-fusion vector. The fusion protein can bind to fibrinogen in a capture enzyme-linked immunosorbent assay and can be purified by fibrinogen affinity chromatography. This protein can completely inhibit the adherence of
S. epidermidis
to immobilized fibrinogen, suggesting that the adherence of
S. epidermidis
to fibrinogen is mainly due to this protein. Antibodies against this fibrinogen binding protein were also found to efficiently block the adherence of
S. epidermidis
to immobilized fibrinogen. Despite homology with clumping factors A and B from
S. aureus
(cell surface-associated proteins binding to fibrinogen), binding involved the β chain of fibrinogen rather than the γ chain, as in clumping factor A.
The Autolysin-Encoding Gene (
lytA
) of
Streptococcus pneumoniae
Displays Restricted Allelic Variation despite Localized Recombination Events with Genes of Pneumococcal Bacteriophage Encoding Cell Wall Lytic Enzymes
Authors: Whatmore Adrian M. , Dowson Christopher G. 
Published: December 2019

ABSTRACT

The
lytA
-encoded autolysin (
N
-acetylmuramoyl-
l
-alanine amidase) of
Streptococcus pneumoniae
is believed to play an important role in the pathogenesis of pneumococcal infection and has been identified as a putative vaccine target. Allelic diversity of
lytA
in an extensive collection of clinical isolates was assessed by restriction fragment length polymorphism and confirmatory sequencing studies. Genetic diversity within
lytA
is limited, especially compared to the high levels of diversity seen in other pneumococcal virulence factor genes, although small blocks generating mosaic structure were identified. Sequence comparisons with genes encoding cell wall lytic enzymes of pneumococcal bacteriophage suggest that localized recombination events have occurred between host
lytA
and these bacteriophage genes. These results confirm earlier suggestions that recombination between DNA encoding bacteriophage autolytic enzymes and chromosomally encoded
lytA
might be important in the evolution of
lytA
. The implications of these findings for understanding the evolution of
lytA
and the potential utility of LytA as a vaccine target are discussed.