bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protection of Mice againstPlasmodium yoeliiSporozoite Challenge withP. yoeliiMerozoite Surface Protein 1 DNA Vaccines
Authors: Becker Sylvia I. , Wang Ruobing , Hedstrom Richard C. , Aguiar Joao C. , Jones Trevor R. , Hoffman Stephen L. , Gardner Malcolm J. 
Published: December 2019

ABSTRACTImmunization of mice with DNA vaccines encoding the full-length form and C and N termini ofPlasmodium yoeliimerozoite surface protein 1 provided partial protection against sporozoite challenge and resulted in boosting of antibody titers after challenge. In C57BL/6 mice, two DNA vaccines provided protection comparable to that of recombinant protein consisting of the C terminus in Freund’s adjuvant.
Bartonella henselaeInvasion of Feline Erythrocytes In Vitro
Authors: Mehock Jane R. , Greene Craig E. , Gherardini Frank C. , Hahn Tae-Wook , Krause Duncan C. 
Published: December 2019

ABSTRACTBartonella henselae, the causative agent of cat scratch disease, establishes long-term bacteremia in cats, in which it attaches to and invades feline erythrocytes (RBC). Feline RBC invasion was assessed in vitro, based on gentamicin selection for intracellular bacteria or by laser confocal microscopy and digital sectioning. Invasion rates ranged from 2 to 20% of the inoculum, corresponding to infection of less than 1% of the RBC. Invasion was a slow process, requiring >8 h before significant numbers of intracellular bacteria were detected. Pretreatment of the bacteria with trypsin, or of the RBC with trypsin or neuraminidase, had no effect, but pronase pretreatment of RBC resulted in a slight increase in invasion frequency. The ability to modelB. henselaeinvasion of feline RBC in vitro should permit identification of bacterial surface components involved in this process and elucidate the significance of RBC invasion to transmission and infection in cats.
Inducible Nitric Oxide Synthase-Deficient Mice Develop Enhanced Type 1 Cytokine-Associated Cellular and Humoral Immune Responses after Vaccination with AttenuatedSchistosoma mansoniCercariae but Display Partially Reduced Resistance
Authors: James Stephanie L. , Cheever Allen W. , Caspar Patricia , Wynn Thomas A. 
Published: December 2019

ABSTRACTHigh levels of nitric oxide (NO) are produced by inducible nitric oxide synthase (iNOS) in response to activating signals from Th1-associated cytokines and play an important role in cytotoxicity and cytostasis against many pathogenic microorganisms. In addition to its direct effector function, NO serves as a potent immunoregulatory factor. NO produced by gamma interferon-activated macrophages immobilizes and killsSchistosoma mansonilarvae, and several studies have indicated a role for this pathway in protective immunity against this parasite. The potential regulatory influence of NO in immunity toS. mansoniis less well understood. In this study, we have used iNOS-deficient mice to determine the role of NO in mice vaccinated with irradiated cercariae ofS. mansoni. We show by enzyme-linked immunosorbent assay and reverse transcriptase PCR analysis that vaccinated iNOS-deficient mice develop exacerbated type 1 cytokine responses in the lungs, the site where resistance to infection is primarily manifested. In addition, parasite-specific immunoglobulin G2a (IgG2a) and IgG2b antibody responses were significantly increased in vaccinated iNOS-deficient animals and total IgE antibody levels in serum were decreased relative to those in wild-type controls. Surprisingly, since resistance in this vaccine model is largely Th1 dependent and since Th1-related cellular and humoral immune responses were found to be exacerbated in vaccinated iNOS-deficient mice, vaccine-elicited protective immunity against challenge infection was found to be reduced. These findings demonstrate that iNOS plays a paradoxical role in immunity toS. mansoni, both in the effector mechanism of resistance and in the down regulation of the type 1 cytokine response, which is ultimately required for NO production.
Cytokine mRNA Expression and Proliferative Responses Induced by Pertussis Toxin, Filamentous Hemagglutinin, and Pertactin ofBordetella pertussisin the Peripheral Blood Mononuclear Cells of Infected and Immunized Schoolchildren and Adults
Authors: He Qiushui , Minh Nhu Nguyen Tran , Edelman Kati , Viljanen Matti K. , Arvilommi Heikki , Mertsola Jussi 
Published: December 2019

ABSTRACTPertussis infection is increasingly recognized in older children and adults, indicating the need of booster immunizations in these age groups. We investigated the induction of pertussis-specific immunity in schoolchildren and adults after booster immunization and natural infection. The expression of mRNA of gamma interferon (IFN-γ), interleukin-2 (IL-2), IL-4, and IL-5 in the peripheral blood mononuclear cells (PBMCs) was assayed by reverse transcription-PCR. The PBMCs of 17 children immunized with one dose of an acellular vaccine containing pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) significantly proliferated in vitro after stimulation with the vaccine antigens. The PBMCs of seven infected individuals markedly proliferated in the presence of PT and FHA, but the cells of only two of these subjects responded to PRN. At least one of the antigens induced mRNA for IL-4 and/or IL-5 in the cells of 93% of tested vaccinees and patients, and FHA induced IFN-γ mRNA in the cells of two-thirds of them. Expression of mRNA for IFN-γ correlated with the production of the cytokine protein. Anti-FHA immunoglobulin G antibodies significantly correlated with FHA-induced proliferative responses both before and after immunization. These results show that booster immunization with acellular pertussis vaccine induces both antibody- and cell-mediated immune responses in schoolchildren. Further, booster immunization and natural infection seem to induce the expression of mRNA of T-helper 1 (Th1) and Th2 type cytokines in similar manners. This observation supports the use of acellular pertussis vaccines for booster immunizations of older children, adolescents, and adults.
Characterization of a Neutralizing Monoclonal Antibody Directed at the Lipopolysaccharide of
Chlamydia pneumoniae
Authors: Peterson Ellena M. , de la Maza Luis M. , Brade Lore , Brade Helmut 
Published: December 2019

ABSTRACT

Identification of protective epitopes is one of the first steps in the development of a subunit vaccine. One approach to accomplishing this is to identify structures or epitopes by using monoclonal antibodies (MAb) that can attenuate infectivity in vitro and in vivo. To date attempts to use this approach with
Chlamydia pneumoniae
have failed. This report is the first description of a MAb directed to the lipopolysaccharide (LPS) of
Chlamydia
that neutralizes both in vitro and in vivo the infectivity of
C. pneumoniae
. MAb CP-33, an immunoglobulin G2b (IgG2b), was identified from a fusion using splenocytes from mice immunized with
C. pneumoniae
TW-183. By Western blot analysis, MAb CP-33 exhibited genus-specific reactivity in that it recognized the LPSs of
C. pneumoniae
,
Chlamydia trachomatis
, and
Chlamydia psittaci
. MAb CP-33 did not react with 15 genera of gram-negative and gram-positive bacteria and
Candida albicans
. By using isolated LPS of Re mutants of
Escherichia coli
,
Salmonella enterica
serovar Minnesota, and recombinants expressing the 3-deoxy-
d
-
manno
-oct-2-ulosonic acid (Kdo) transferase gene
kdtA
of
C. trachomatis
, MAb CP-33 was shown to require for binding the presence of the genus-specific trisaccharide epitope αKdo(2→8)αKdo(2→4)αKdo. By employing synthetic oligosaccharides and neoglycoconjugates in an enzyme immunoassay (EIA) and EIA inhibition, it was further shown that MAb CP-33 differed from the extensively investigated prototype chlamydial LPS MAb S25-23. Most likely, MAb CP-33 recognizes a conformational epitope in which the αKdo(2→8)αKdo(2→4)αKdo trisaccharide is an essential structural component. When tested in an in vitro neutralization assay, MAb CP-33 gave a 50% neutralization titer of 8 ng/ml against
C. pneumoniae
TW-183. However, this MAb did not neutralize other
C. pneumoniae
strains,
C. trachomatis
, or
C. psittaci. C. pneumoniae
TW-183 was treated with either MAb CP-33 or a control IgG and then used to inoculate mice by the respiratory route. Five days after inoculation, there was a difference between the mice inoculated with the control IgG-treated inoculum and those inoculated with the MAb CP-33-treated organisms as to the number of mice infected as well as the number of inclusion-forming units recovered from lung cultures (
P
< 0.05). In summary, a
Chlamydia
-specific LPS MAb was able to neutralize in vitro the infectivity of
C. pneumoniae
TW-183.
Transgenic Expression of a Mosquito-Stage Malarial Protein, Pbs21, in Blood Stages of Transformed
Plasmodium berghei
and Induction of an Immune Response upon Infection
Authors: Margos Gabriele , van Dijk Melissa R. , Ramesar Jai , Janse Chris J. , Waters Andrew P. , Sinden Robert E. 
Published: December 2019

ABSTRACT

Pbs21 is a surface protein of the ookinete of
Plasmodium berghei
, which can induce a potent transmission-blocking immune response. Pbs21 is normally expressed only by parasite stages in the mosquito, i.e., female gametes/zygotes, ookinetes, and oocysts. However, the Pbs21 gene is transcribed in female gametocytes which circulate in the bloodstream of the host, where translation of the resulting mRNA is totally repressed. Episomal transfection has been used to investigate whether expression of Pbs21 protein could be achieved in blood stages of the parasite. By using plasmid pMD221, the complete mRNA-encoding region of Pbs21, flanked only by 218 nucleotides (nt) of its promoter region and 438 nt of its 3′ region downstream from the polyadenylation site, was introduced into the blood stages of gametocyte-producing and non-gametocyte-producing clones of
P. berghei
. In both of these transformed parasite lines, Pbs21 protein was expressed in asexual trophozoites, schizonts, and, when present, in both male and female gametocytes. Hence, the flanking regions present are sufficient to allow transcription but lack the elements that exert natural control of sex- and stage-specific transcription. The mRNA and the protein expressed by transformed blood stages were indistinguishable from the wild-type forms by the criteria tested, and the protein was recognized by both conformation-dependent and conformation-independent monoclonal antibodies raised against native Pbs21. In mice infected with transformed non-gametocyte-producing parasites, a Pbs21-specific immune response was induced and characterized with respect to isotype (IgG2a/IgG2b) and quantity (11.5 ± 10 μg/ml) of antibody produced. However, as found in previous studies, these antibody levels were insufficient to inhibit development of the parasites in the mosquito. The ability to express mosquito midgut-stage antigens in blood-stage parasites will facilitate further investigations of molecular and immunological properties of these proteins.
Expression ofToxoplasma gondii-Specific Heat Shock Protein 70 during In Vivo Conversion of Bradyzoites to Tachyzoites
Authors: Silva Neide M. , Gazzinelli Ricardo T. , Silva Deise A. O. , Ferro Eloisa A. V. , Kasper Lloyd H. , Mineo Jose R. 
Published: December 2019

ABSTRACTStage conversion between bradyzoites and tachyzoites was investigated in C57BL/6 mice chronically infected with the ME-49 strain ofToxoplasma gondii. In order to promote bradyzoite-tachyzoite conversion, mice were treated in vivo with neutralizing doses of anti-gamma interferon (IFN-γ) or anti-tumor necrosis factor alpha (TNF-α) antibodies. Expression of parasite-specific antigens SAG-1, SAG-2, and heat shock protein 70 (Hsp-70) was visualized in the central nervous system by immunocytochemistry and measured by photometric assay. The immunosuppressive effect of anti-IFN-γ or anti-TNF-α treatment was immediate, leading to parasite stage conversion as indicated by the increased expression of tachyzoite-specific antigens (SAG-1 and SAG-2) and by rapid parasite replication. We also observed expression of high levels of Hsp-70 during a short period of conversion of bradyzoites to tachyzoites. Our data suggest that Hsp-70 may have an important role in the process of bradyzoite-tachyzoite conversion during the reactivation of chronic toxoplasmosis.
Streptococcal Pyrogenic Exotoxin B Induces Apoptosis and Reduces Phagocytic Activity in U937 Cells
Authors: Kuo Chih-Feng , Wu Jiunn-Jong , Tsai Pei-Jane , Kao Fu-Jen , Lei Huan-Yao , Lin Ming T. , Lin Yee-Shin 
Published: December 2019

ABSTRACTTreatment of U937 human monocyte-like cells withStreptococcus pyogenesled to an induction of apoptosis in these cells. A comparison between the wild-type strain and its isogenic protease-negative mutant indicated that the production of streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease, caused a greater extent of apoptosis in U937 cells. Further study using purified SPE B showed that this protease alone could induce U937 cells to undergo apoptosis, which was characterized by morphologic changes, DNA fragmentation laddering on the gel, and an increase in the percentages of hypodiploid cells. The protease activity of SPE B was required for apoptosis to proceed, since treatment with cysteine protease inhibitor E64 or heat inactivation abrogated this death-inducing effect. The SPE B-induced apoptosis pathway was interleukin-1β converting enzyme (ICE) family protease dependent. Further experiments showed that the phagocytic activity of U937 cells was reduced by SPE B. Treatment with E64 and heat inactivation both abrogated this phagocytosis-inhibitory effect. Taken together, the present data show that SPE B not only possesses the ability to induce apoptosis in monocytic cells but also helps bacteria to resist phagocytosis by host cells.
Expression of Listeriolysin O and ActA by Intracellular and ExtracellularListeria monocytogenes
Authors: Moors Marlena A. , Levitt Brian , Youngman Philip , Portnoy Daniel A. 
Published: December 2019

ABSTRACTListeria monocytogenesrequires listeriolysin O (LLO) and ActA, the products ofhlyandactA, respectively, to establish a productive intracellular infection. LLO is essential for vacuolar lysis and entry into the cytosol, while ActA is required for bacterial spread to adjacent cells. We have used a transcriptional reporter gene system to compare the expression ofactAandhlyduring intracellular growth to that during growth in broth cultures. ThehlyandactAgenes were transcriptionally fused toEscherichia coli lacZandBacillus pumilus cat-86 (cat), and the fusions were integrated in single copies into theL. monocytogeneschromosome. A chloramphenicol resistance assay indicated that thehlyfusion but not theactAfusion was significantly activated in Luria-Bertani (LB) broth, and this finding correlated with LLO and ActA levels detectable in broth cultures. Quantitation of promoter activity on the basis of β-galactosidase activity revealed up to 10-fold-higher level of expression of thehlyfusion relative to theactAfusion in LB broth. In contrast, both fusions were active in the cytosol of J774 cells, and the activity of theactAfusion was approximately 3-fold higher than that of thehlyfusion under these conditions. However, quantitative immunoprecipitation of ActA and LLO from infected J774 cells demonstrated approximately 70-fold more cytosolic ActA than cytosolic LLO. Finally, in comparison to induction in broth cultures,actAwas highly induced (226-fold) andhlywas moderately induced (20-fold) in J774 cells. Collectively, these results indicate thatactAandhlyare differentially regulated in response to the growth environment and that both genes are preferentially expressed during intracellular growth. Further, while the lower level of production of ActA than of LLO in broth can be accounted for by transcriptional regulation, the relative abundance of intracellular ActA compared to that of intracellular LLO is a function of additional, possibly host-mediated, factors.
Gamma Interferon Augments Macrophage Activation by Lipopolysaccharide by Two Distinct Mechanisms, at the Signal Transduction Level and via an Autocrine Mechanism Involving Tumor Necrosis Factor Alpha and Interleukin-1
Authors: Held Thomas K. , Weihua Xiao , Yuan Liang , Kalvakolanu Dhananjaya V. , Cross Alan S. 
Published: December 2019

ABSTRACTWhen given in the presence of gamma interferon (IFN-γ), otherwise nontoxic doses of lipopolysaccharide (LPS or endotoxin) become highly lethal for mice. The mechanisms of this synergistic toxicity are not known. We considered the possibility that an interaction between the LPS-induced NF-κB and IFN-γ-induced JAK-STAT pathways at the pretranscriptional level may enhance the LPS-induced signals. To test this hypothesis, we incubated murine macrophage RAW 264.7 cells with IFN-γ for 2 h before addition of different doses of LPS. Consistent with the synergistic induction of inducible nitric oxide synthase mRNA and nitric oxide production by a combination of LPS and IFN-γ, IFN-γ strongly augmented LPS-induced NF-κB activation and accelerated the binding of NF-κB to DNA to as early as 5 min. In agreement with this, IFN-γ pretreatment promoted rapid degradation of IκB-α but not that of IκB-β. Inhibition of protein synthesis during IFN-γ treatment suppressed LPS-initiated NF-κB binding. A rapidly induced protein appeared to be involved in IFN-γ priming. Preincubation of cells with antibodies to tumor necrosis factor alpha or the interleukin-1 receptor partially reduced the priming effect of IFN-γ. In a complementary manner, LPS enhanced the activation of signal-transducing activator of transcription 1 by IFN-γ. These data suggest novel mechanisms for the synergy between IFN-γ and LPS by which they cross-regulate the signal-transducing molecules. Through this mechanism, IFN-γ may transform a given dose of LPS into a lethal stimulus capable of causing sepsis. It may also serve a beneficial purpose by enabling the host to respond quickly to relatively low doses of LPS and thereby activating antibacterial defenses.
Influence of theSalmonella typhimuriumPathogenicity Island 2 Type III Secretion System on Bacterial Growth in the Mouse
Authors: Shea Jacqueline E. , Beuzon Carmen R. , Gleeson Colin , Mundy Rosanna , Holden David W. 
Published: December 2019

ABSTRACTWe have investigated the in vivo growth kinetics of aSalmonella typhimuriumstrain (P11D10) carrying a mutation inssaJ, aSalmonellapathogenicity island 2 (SPI2) gene encoding a component of a type III secretion system required for systemic growth in mice. Similar numbers of mutant and wild-type cells were recovered from the spleens and livers of BALB/c mice up to 8 h after inoculation by the intraperitoneal route. Thereafter, the numbers of wild-type cells continued to increase logarithmically in these organs, whereas those of P11D10 remained relatively static for several days before being cleared. Gentamicin protection experiments on spleen cell suspensions recovered from infected mice showed that viable intracellular wild-type bacteria accumulated over time but that intracellular P11D10 cells did not. Infection experiments were also performed with wild-type and P11D10 cells carrying the temperature-sensitive plasmid pHSG422 to distinguish between bacterial growth rates and killing in vivo. At 16 h postinoculation there were 10-fold more wild-type cells than mutant cells in the spleens of infected mice, but the numbers of cells of both strains carrying the nonreplicating plasmid were very similar, showing that there was little difference in the degree of killing sustained by the two strains and that the SPI2 secretion system must be required for bacterial replication, rather than survival, in vivo. The SPI2 mutant phenotype in mice is similar to that of strains carrying mutations in theSalmonellavirulence plasmidspvgenes. To determine if these two sets of genes interact together, a double mutant strain carrying SPI2 andspvmutations was constructed and compared with strains carrying single mutations in terms of virulence attenuation. These experiments failed to provide any evidence showing that the SPI2 andspvgene products interact together as part of the same virulence mechanism.
Role of Gamma Interferon inHelicobacter pylori-Induced Gastric Inflammatory Responses in a Mouse Model
Authors: Sawai Naoki , Kita Masakazu , Kodama Tadashi , Tanahashi Toshihito , Yamaoka Yoshio , Tagawa Yoh-ichi , Iwakura Yoichiro , Imanishi Jiro 
Published: December 2019

ABSTRACTThe immune responses toHelicobacter pyloriinfection play important roles in gastroduodenal diseases. The contribution of gamma interferon (IFN-γ) to the immune responses, especially to the induction of gastric inflammation and to protection fromH. pyloriinfection, was investigated with IFN-γ gene knockout (IFN-γ−/−) mice. We first examined the colonizing abilities of eightH. pyloristrains with a short-term infection test in order to selectH. pyloristrains which could colonize the mouse stomach. Only three strains (ATCC 43504, CPY2052, and HPK127) colonized C57BL/6 wild-type mice, although all of the strains except for ATCC 51110 could colonize IFN-γ−/−mice. The number ofH. pyloriorganisms colonizing the stomach in wild-type mice was lower than that in IFN-γ−/−mice. Oral immunization with the CPY2052 sonicate and cholera toxin protected against infection with strain CPY2052 in both types of mouse. These findings suggested that IFN-γ may play a protective role inH. pyloriinfection, although the degree of its protective ability was estimated to be low. In contrast, in a long-term infection test done to examine the contribution of IFN-γ to gastric inflammation, CPY2052-infected wild-type mice developed a severe infiltration of mononuclear cells in the lamina propria and erosions in the gastric epithelium 15 months after infection, whereas CPY2052-infected IFN-γ−/−mice showed no inflammatory symptoms. This result clearly demonstrated that IFN-γ plays an important role in the induction of gastric inflammation caused byH. pyloriinfection.
Saccharomyces boulardii
Protease Inhibits the Effects of
Clostridium difficile
Toxins A and B in Human Colonic Mucosa
Authors: Castagliuolo Ignazio , Riegler Martin F. , Valenick Leyla , LaMont J. Thomas , Pothoulakis Charalabos 
Published: December 2019

ABSTRACT

Saccharomyces boulardii
is a nonpathogenic yeast used in the treatment of
Clostridium difficile
diarrhea and colitis. We have reported that
S. boulardii
inhibits
C. difficile
toxin A enteritis in rats by releasing a 54-kDa protease which digests the toxin A molecule and its brush border membrane (BBM) receptor (I. Castagliuolo, J. T. LaMont, S. T. Nikulasson, and C. Pothoulakis, Infect. Immun. 64:5225–5232, 1996). The aim of this study was to further evaluate the role of
S. boulardii
protease in preventing
C. difficile
toxin A enteritis in rat ileum and determine whether it protects human colonic mucosa from
C. difficile
toxins. A polyclonal rabbit antiserum raised against purified
S. boulardii
serine protease inhibited by 73% the proteolytic activity present in
S. boulardii
conditioned medium in vitro. The anti-protease immunoglobulin G (IgG) prevented the action of
S. boulardii
on toxin A-induced intestinal secretion and mucosal permeability to [
3
H]mannitol in rat ileal loops, while control rabbit IgG had no effect. The anti-protease IgG also prevented the effects of
S. boulardii
protease on digestion of toxins A and B and on binding of [
3
H]toxin A and [
3
H]toxin B to purified human colonic BBM. Purified
S. boulardii
protease reversed toxin A- and toxin B-induced inhibition of protein synthesis in human colonic (HT-29) cells. Furthermore, toxin A- and B-induced drops in transepithelial resistance in human colonic mucosa mounted in Ussing chambers were reversed by 60 and 68%, respectively, by preexposing the toxins to
S. boulardii
protease. We conclude that the protective effects of
S. boulardii
on
C. difficile
-induced inflammatory diarrhea in humans are due, at least in part, to proteolytic digestion of toxin A and B molecules by a secreted protease.