bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Cell Cycle-Specific Growth-Inhibitory Factor Produced byActinobacillus actinomycetemcomitansIs a Cytolethal Distending Toxin
Authors: Sugai Motoyuki , Kawamoto Toru , Pérès Sylvie Y. , Ueno Yoko , Komatsuzawa Hitoshi , Fujiwara Tamaki , Kurihara Hidemi , Suginaka Hidekazu , Oswald Eric 
Published: December 2019

ABSTRACTActinobacillus actinomycetemcomitanshas been shown to produce a soluble cytotoxic factor(s) distinct from leukotoxin. We have identified inA. actinomycetemcomitansY4 a cluster of genes encoding a cytolethal distending toxin (CDT). This new member of the CDT family is similar to the CDT produced byHaemophilus ducreyi. The CDT fromA. actinomycetemcomitanswas produced inEscherichia coliand was able to induce cell distension, growth arrest in G2/M phase, nucleus swelling, and chromatin fragmentation in HeLa cells. The three proteins, CDTA, -B and -C, encoded by thecdtlocus were all required for toxin activity. Antiserum raised against recombinant CDTC completely inhibited the cytotoxic activity of culture supernatant and cell homogenate fractions ofA. actinomycetemcomitansY4. These results strongly suggest that the CDT is responsible for the cytotoxic activity present in the culture supernatant and cell homogenate fractions ofA. actinomycetemcomitansY4. This CDT is a new putative virulence factor ofA. actinomycetemcomitansand may play a role in the pathogenesis of periodontal diseases.
Vaccination with Trypomastigote Surface Antigen 1-Encoding Plasmid DNA Confers Protection against LethalTrypanosoma cruziInfection
Authors: Wizel Benjamin , Garg Nisha , Tarleton Rick L. 
Published: December 2019

ABSTRACTDNA vaccination was evaluated with the experimental murine model ofTrypanosoma cruziinfection as a means to induce antiparasite protective immunity, and the trypomastigote surface antigen 1 (TSA-1), a target of anti-T. cruziantibody and major histocompatibility complex (MHC) class I-restricted CD8+cytotoxic T-lymphocyte (CTL) responses, was used as the model antigen. Following the intramuscular immunization ofH-2bandH-2dmice with a plasmid DNA encoding an N-terminally truncated TSA-1 lacking or containing the C-terminal nonapeptide tandem repeats, the antibody level, CTL response, and protection against challenge withT. cruziwere assessed. InH-2bmice, antiparasite antibodies were induced only by immunization with the DNA construct encoding TSA-1 containing the C-terminal repeats. However, both DNA constructs were efficient in eliciting long-lasting CTL responses against the protectiveH-2Kb-restricted TSA-1515–522epitope. InH-2dmice, inoculation with either of the two TSA-1-expressing vectors effectively generated antiparasite antibodies and primed CTLs that lysedT. cruzi-infected cells in an antigen-specific, MHC class I-restricted, and CD8+-T-cell-dependent manner. When TSA-1 DNA-vaccinated animals were challenged withT. cruzi, 14 of 22 (64%)H-2band 16 of 18 (89%)H-2dmice survived the infection. The ability to induce significant murine anti-T. cruziprotective immunity by immunization with plasmid DNA expressing TSA-1 provides the basis for the application of this technology in the design of optimal DNA multicomponent anti-T. cruzivaccines which may ultimately be used for the prevention or treatment of Chagas’ disease.
Altered Immune Responses in Mice with ConcomitantSchistosoma mansoniandPlasmodium chabaudiInfections
Authors: Helmby Helena , Kullberg Marika , Troye-Blomberg Marita 
Published: December 2019

ABSTRACTMixed parasitic infections are common in many parts of the world. However, little is known about how concurrent infections affect the immunity to and/or pathogenesis of each other. Protection and elimination of blood-stagePlasmodium chabaudi chabaudiAS in resistant mice are characterized by a sequential activation of CD4+Th1 and Th2 cells. The patent egg-laying stage of the murine model ofSchistosoma mansoniis associated with a strong Th2 response to bothSchistosomaand unrelated antigens. In this study, we investigated how infection of mice withS. mansoniwould affect the immune response to and pathogenesis of aP. chabaudiinfection. C57BL/6 mice infected withS. mansonifor 8 weeks were infected with blood-stageP. chabaudi. Malaria parasitemias were significantly higher in these mice than in mice infected withP. chabaudionly. In doubly infected mice, both spleen cell proliferative and Th2 responses toS. mansonisoluble egg antigen (SEA) or anti-CD3 were suppressed up to 1 month after the malaria infection. Findings for SEA-specific immunoglobulin M (IgM) and IgG serum antibody levels were similar. No significant effects were seen onP. chabaudi-induced gamma interferon responses. However, tumor necrosis factor alpha (TNF-α) production was significantly lower in double-infected mice. Thus, a defect in TNF-α production might contribute to the increased malaria parasitemias seen inS. mansoni-P. chabaudi-infected mice. Taken together, our data show that schistosoma and malaria infections profoundly affect each other, findings which might have implications for the development of vaccines.
Resident Enteric Bacteria Are Necessary for Development of Spontaneous Colitis and Immune System Activation in Interleukin-10-Deficient Mice
Authors: Sellon Rance K. , Tonkonogy Susan , Schultz Michael , Dieleman Levinus A. , Grenther Wetonia , Balish Ed , Rennick Donna M. , Sartor R. Balfour 
Published: December 2019

ABSTRACTMice with targeted deletion of the gene for interleukin-10 (IL-10) spontaneously develop enterocolitis when maintained in conventional conditions but develop only colitis when kept in specific-pathogen-free (SPF) environments. This study tested the hypothesis that enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice. IL-10-deficient mice were maintained in either SPF conditions or germfree conditions or were populated with bacteria known to cause colitis in other rodent models. IL-10-deficient mice kept in SPF conditions developed colitis in all segments of the colon (cecum and proximal and distal colon). These mice exhibited immune system activation as evidenced by increased expression of CD44 on CD4+T cells; increased mesenteric lymph node cell numbers; and increased production of immunoglobulin A (IgA), IgG1, and IL-12 p40 from colon fragment cultures. Mice populated with bacterial strains, includingBacteroides vulgatus, known to induce colitis in other rodent models had minimal colitis. Germfree IL-10-deficient mice had no evidence of colitis or immune system activation. We conclude therefore that resident enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice.
Regulation of Protease Expression in
Porphyromonas gingivalis
Authors: Tokuda Masayuki , Chen Wen , Karunakaran Thonthi , Kuramitsu Howard K. 
Published: December 2019

ABSTRACT

Although the strong protease activity of
Porphyromonas gingivalis
appears to be an important virulence property of these organisms, little information is currently available regarding the regulation of expression of the multiple protease genes. Utilizing the
lacZ
reporter gene strategy, the environmental factors which regulate the expression of the Arg-gingipain gene
rgpA
and the
prtT
protease gene were investigated. These two genes are reciprocally regulated since factors which retarded growth (iron depletion and nutrient limitation) appeared to upregulate
rgpA
expression while down-regulating
prtT
expression. However, inactivation of the major
rgpA
gene resulted in increased transcription of the
prtT
and
tpr
protease genes while decreasing expression of the Lys-gingipain
kgp
gene as detected by Northern blot analysis. By contrast, inactivation of the
prtT
gene did not significantly affect
kgp
expression but moderately decreased
rgpA
mRNA levels. These results indicate that the protease genes of
P. gingivalis
are not coordinately regulated and suggest that some of these enzymes play specific roles in the physiology and/or virulence of these organisms.
Staphylococcus aureus
Agr and Sar Global Regulators Influence Internalization and Induction of Apoptosis
Authors: Wesson Carla A. , Liou Linda E. , Todd Kristine M. , Bohach Gregory A. , Trumble William R. , Bayles Kenneth W. 
Published: December 2019

ABSTRACT

Staphylococcus aureus
was recently shown to be internalized by and to induce apoptosis in a bovine mammary epithelial cell line, suggesting that these processes could be involved in staphylococcal pathogenesis or persistence. To examine the role of virulence factor regulators during internalization, mutant
agr
and
sar
strains of
S. aureus
were analyzed for their abilities to enter and induce apoptosis in epithelial cells. Like a previously characterized bovine mastitis isolate, the standard laboratory strain, RN6390 (wild type), entered the epithelial cells and subsequently induced apoptosis. In contrast, the mutant strains RN6911 (
agr
), ALC136 (
sar
), and ALC135 (
agr sar
) were internalized by the cultured cells at levels reproducibly greater than that for RN6390 but failed to induce apoptosis. The internalization of
S. aureus
was affected by growth phase, suggesting a role for
agr
-regulated surface proteins in this process. Furthermore, the ability to induce apoptosis required metabolically active intracellular bacteria. These data indicate that the ability of
S. aureus
to enter mammalian cells and induce apoptosis is dependent on factors regulated by Agr and Sar. Since transcriptional control by these global regulators is mediated by quorum-sensing and environmental factors, staphylococci may have the potential to induce several alternative effects on cells from an intracellular environment. A model for the function of the
agr
locus in the context of internalization, intracellular persistence, and dissemination is proposed.
The p29 and p35 Immunodominant Antigens ofNeospora caninumTachyzoites Are Homologous to the Family of Surface Antigens ofToxoplasma gondii
Authors: Howe Daniel K. , Crawford Amy C. , Lindsay David , Sibley L. David 
Published: December 2019

ABSTRACTNeospora caninumis an apicomplexan parasite that is closely related toToxoplasma gondiiand has been found to be associated with neurological disorders in dogs and congenital infections and abortions in cattle. We have identified two surface proteins of 29 and 35 kDa (designated Ncp29 and Ncp35, respectively) fromN. caninumtachyzoites that are the predominant antigens recognized by antisera fromNeospora-infected animals. Monoclonal antibodies against Ncp29 and Ncp35 were used to analyze several independent and diverseN. caninumisolates; both antigens were recognized in all isolates, suggesting that they are well conserved. Localization studies and surface labeling with biotin demonstrated that Ncp29 and Ncp35 are membrane associated and displayed on the surface of the parasite. After treatment with phosphatidylinositol-specific phospholipase C, parasite lysates were analyzed with antibodies against the cross-reacting determinant of glycosylphosphatidylinositol anchors. Approximately six glycolipid-anchored surface proteins were identified, with the two most prominent corresponding to Ncp29 and Ncp35. Sequence comparisons of Ncp29 and Ncp35 with GenBank indicated that they are most similar to theT. gondiisurface antigen 1 (SAG1) and surface antigen 1-related sequence 2 (SRS2), respectively. Consequently, Ncp29 has been designated NcSAG1 and Ncp35 has been designated NcSRS2. Both NcSAG1 and NcSRS2 contain a tandemly duplicated motif and 12 absolutely conserved cysteines which are also found in all of the SAG and SRS proteins ofT. gondii. Maintenance of these motifs and the 12 cysteine residues suggests that these surface antigens share a similar secondary and tertiary structure that is presumably important for a conserved function that these antigens serve during infection.
Fusion of
Chlamydia trachomatis
-Containing Inclusions Is Inhibited at Low Temperatures and Requires Bacterial Protein Synthesis
Authors: Van Ooij Christiaan , Homola Ellen , Kincaid Eleanor , Engel Joanne 
Published: December 2019

ABSTRACT

The human pathogen
Chlamydia trachomatis
is an obligate intracellular bacterium with a unique developmental cycle. Within the host cell cytoplasm, it resides within a membrane-bound compartment, the inclusion. A distinguishing characteristic of the
C. trachomatis
life cycle is the fusion of the chlamydia-containing inclusions with each other in the host cell cytoplasm. We report that fusion of inclusions does not occur at 32°C in multiple mammalian cell lines and with three different serovars of
C. trachomatis
. The inhibition of fusion was inclusion specific; the fusion with sphingolipid-containing secretory vesicles and the interaction with early endosomes were unaffected by incubation at 32°C. The inhibition of fusion of the inclusions was not primarily the result of delayed maturation of the inclusion, as infectious progeny was produced in host cells incubated at 32°C, and the unfused inclusions remained competent to fuse up to 48 h postinfection. The ability to reverse the inhibition of fusion by shifting the infected cells from 32 to 37°C allowed the measurement of the rate and the time of fusion of the inclusions after entry of the bacteria. Most significantly, we demonstrate that fusion of inclusions with each other requires bacterial protein synthesis and that the required bacterial protein(s) is present, but inactive or not secreted, at 32°C.
A Streptococcal Adhesion System for Salivary Pellicle and Platelets
Authors: Gong Ke , Ouyang T. , Herzberg M. C. 
Published: December 2019

ABSTRACT

A
Streptococcus sanguis
133-79 adhesin identified by the monoclonal antibody 1.1 (MAb 1.1) binds both saliva-coated hydroxylapatite (sHA) and platelets. The complementary binding site(s) for the adhesin was identified by the anti-idiotypical MAb 2.1. To learn if this adhesion system, marked by the antiadhesin MAb 1.1 and anti-binding site MAb 2.1, is commonly used by strains within the sanguis group and other viridans group streptococci, 42 strains from seven species were tested. Strains that bind to both sHA and platelets use the same adhesin and binding site epitopes. Strains that do not adhere to platelets rely on other adhesin specificities to bind to sHA.
Gamma Interferon Production by Cytotoxic T Lymphocytes Is Required for Resolution ofChlamydia trachomatisInfection
Authors: Lampe Mary F. , Wilson Christopher B. , Bevan Michael J. , Starnbach Michael N. 
Published: December 2019

ABSTRACTIn this study, we used mice in which the gene for gamma interferon (IFN-γ) has been disrupted (IFN-γ−/−mice) to study the role of this cytokine in the resolution ofChlamydia trachomatisinfection. We show that IFN-γ−/−mice are impaired in the ability to clear infection withC. trachomatiscompared to IFN-γ+/+control mice. Activated CD8+cytotoxic T lymphocytes (CTL) secrete IFN-γ in response to intracellular infection, and we have shown previously that aChlamydia-specific CTL line can reduceC. trachomatisinfection when adoptively transferred into infected mice. In the present study, we found that when these IFN-γ+/+CTL lines are transferred intoChlamydia-infected IFN-γ−/−mice, the transferred CTL cannot overcome the immune defect seen in the IFN-γ−/−mice. We also show thatChlamydia-specific CTL can be cultured from IFN-γ-deficient mice infected withC. trachomatis; however, the adoptive transfer of IFN-γ−/−CTL into infected IFN-γ+/+mice does not reduce the level of infection. These results suggest that IFN-γ production by CTL is not sufficient to overcome the defect that IFN-γ−/−mice have in the resolution ofChlamydiainfection, yet IFN-γ production by CTL is required for the protective effect seen upon adoptive transfer of CTL into IFN-γ+/+mice.
Deletion of the Major Proteolytic Site of the
Helicobacter pylori
Cytotoxin Does Not Influence Toxin Activity but Favors Assembly of the Toxin into Hexameric Structures
Authors: Burroni Daniela , Lupetti Pietro , Pagliaccia Cristina , Reyrat Jean Marc , Dallai Romano , Rappuoli Rino , Telford John L. 
Published: December 2019

ABSTRACT

The
Helicobacter pylori
cytotoxin is proteolytically cleaved at a flexible hydrophilic loop into two subunits. Deletion of the loop sequences had no effect on biological activity of the toxin in the HeLa cell vacuolation assay but favored the organization of the protein into hexameric rather than heptameric structures.
A Protein (M9) Associated with Monoclonal Antibody-Mediated Agglutination ofMycoplasma gallisepticumIs a Member of the pMGA Family
Authors: Liu Li , Payne D. Michael , van Santen Vicky L. , Dybvig Kevin , Panangala Victor S. 
Published: December 2019

ABSTRACTA 62-kDa cell surface antigen (M9) ofMycoplasma gallisepticumPG31 that mediates antibody-induced agglutination of the organism was purified and subjected to N-terminal amino-acid sequencing. A 999-bp region of the cDNA encoding the M9 protein was generated by reverse transcription-PCR, and its nucleotide sequence was determined. PCR primers based on this sequence were used to screen a genomic DNA library of PG31. A full-length M9 protein-encoding gene was isolated and sequenced, revealing 96% nucleotide identity with thepMGA1.1gene ofM. gallisepticumS6. Sequence analyses of theM9gene and flanking open reading frames that encode other pMGA family members suggest that a tandemly repeated GAA sequence may influencepMGAgene expression.
Brucella abortus
Transits through the Autophagic Pathway and Replicates in the Endoplasmic Reticulum of Nonprofessional Phagocytes
Authors: Pizarro-Cerdá Javier , Méresse Stéphane , Parton Robert G. , van der Goot Gisou , Sola-Landa Alberto , Lopez-Goñi Ignacio , Moreno Edgardo , Gorvel Jean-Pierre 
Published: December 2019

ABSTRACT

Brucella abortus
is an intracellular pathogen that replicates within a membrane-bounded compartment. In this study, we have examined the intracellular pathway of the virulent
B. abortus
strain 2308 (S2308) and the attenuated strain 19 (S19) in HeLa cells. At 10 min after inoculation, both bacterial strains are transiently detected in phagosomes characterized by the presence of early endosomal markers such as the early endosomal antigen 1. At ∼1 h postinoculation, bacteria are located within a compartment positive for the lysosome-associated membrane proteins (LAMPs) and the endoplasmic reticulum (ER) marker sec61β but negative for the mannose 6-phosphate receptors and cathepsin D. Interestingly, this compartment is also positive for the autophagosomal marker monodansylcadaverin, suggesting that S2308 and S19 are located in autophagic vacuoles. At 24 h after inoculation, attenuated S19 is degraded in lysosomes, while virulent S2308 multiplies within a LAMP- and cathepsin D-negative but sec61β- and protein disulfide isomerase-positive compartment. Furthermore, treatment of infected cells with the pore-forming toxin aerolysin from
Aeromonas hydrophila
causes vacuolation of the bacterial replication compartment. These results are compatible with the hypothesis that pathogenic
B. abortus
exploits the autophagic machinery of HeLa cells to establish an intracellular niche favorable for its replication within the ER.
Relationship of Structure and Biological Activity of Monosaccharide Lipid A Analogues to Induction of Nitric Oxide Production by Murine Macrophage RAW264.7 Cells
Authors: Funatogawa Keiji , Matsuura Motohiro , Nakano Masayasu , Kiso Makoto , Hasegawa Akira 
Published: December 2019

ABSTRACTLipid A is the active center of bacterial lipopolysaccharide (LPS), which exhibits diverse biological activities via the production of various mediators. We investigated the production of nitric oxide (NO), one of the mediators, by a murine macrophage cell line, RAW264.7, upon stimulation with a series of monosaccharide lipid A analogues to elucidate the relationship of structure and activity in NO production. The production of other representative mediators, such as tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), was also investigated to compare the structural requirements for the production of these cytokines with those for the production of NO. Structure-activity relationships in NO production correlated well with those in the production of TNF-α and IL-6. Among the lipid A analogues possessing different numbers of acyl groups on a 4-O-phosphono-d-glucosamine backbone, compounds like GLA-60 that possess three tetradecanoyl (C14) groups exhibited stronger activities in the production of the mediators than compounds possessing four or two C14groups. Time course study of the production of these mediators showed that production of NO started and peaked later than those of TNF-α and IL-6. Neither neutralization of TNF-α activity by antibody nor suppression of TNF-α production by pentoxifylline showed a significant suppressive effect on production of NO and IL-6 upon stimulation with LPS or lipid A analogues. Neutralization of IL-6 activity by antibody showed no significant suppressive effect on production of NO and TNF-α. A monosaccharide lipid A analogue (GLA-58) which exhibited no detectable agonistic activity showed a suppressive effect on the production of all three mediators upon stimulation with LPS or lipid A analogues. These results indicate that signals for NO production by LPS agonists in murine macrophages are transduced in good correlation with those for production of TNF-α and IL-6, although they are not transduced via production of those cytokines.
Characterization of Membrane-Associated
Clostridium perfringens
Enterotoxin following Pronase Treatment
Authors: Wieckowski Eva U. , Kokai-Kun John F. , McClane Bruce A. 
Published: December 2019

ABSTRACT

After binding,
Clostridium perfringens
enterotoxin (CPE) initially localizes in a small (∼90-kDa) complex in plasma membranes. This event is followed by formation of a second membrane complex, referred to as large (160-kDa) complex. Contrary to a previous hypothesis proposing that CPE inserts into intestinal brush border membranes (BBMs) when this toxin is localized in the small complex, this study shows that BBMs do not offer CPE localized in the small complex protection from pronase. However, our experiments indicate that BBMs do substantially protect CPE from pronase when this toxin is localized in large complex. Since the onset of CPE-induced permeability alterations closely coincides with large-complex formation, these new results suggest that CPE-induced alterations in permeability may result from pore formation due to the partial membrane insertion of CPE when this toxin is present in large complex.