bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of Immunity in Experimental Syphilis with Serum-Mediated Aggregation ofTreponema pallidumRare Outer Membrane Proteins
Authors: Lewinski Michael A. , Miller James N. , Lovett Michael A. , Blanco David R. 
Published: December 2019

ABSTRACTWe have previously shown by freeze-fracture electron microscopy that serum from infection-immune syphilitic rabbits aggregates the low-density membrane-spanningTreponema pallidumrare outer membrane proteins (TROMPs). The purpose of this study was to determine if a relationship could be demonstrated between acquired immunity in experimental rabbit syphilis, serum complement-dependent treponemicidal antibody, and antibody directed against TROMPs as measured by the aggregation of TROMP particles. Three groups ofT. pallidum-infected rabbits were treated curatively with penicillin at 9 days, 30 days, and 6 months postinfection to generate various degrees of immunity to challenge reinfection. Sera from rabbits completely susceptible to localized and disseminated reinfection possessed a low titer of treponemicidal antibody (≤1:1 in killing ≥50% of a treponemal suspension) and showed a correspondingly low level of TROMP aggregation (16.5% of the total number of outer membrane particles counted) similar to normal serum controls (13.4%); the number of particles within these aggregates never exceeded three. Sera from partially immune rabbits, which were susceptible to local reinfection but had no evidence of dissemination, showed an increase in the titer of treponemicidal antibody (1:16) compared to the completely susceptible group (≤1:1). Although no significant increase was observed in the total number of TROMP particles aggregated (18.9%) compared to the number in controls (13.4%), approximately 15% of these aggregates did exhibit a significant increase in the number of particles per aggregate (4 to 5 particles) compared to controls (≤3 particles), indicating a measurable increase in anti-TROMP antibody. Finally, sera from rabbits completely immune to both local and disseminated reinfection possessed both high titers of treponemicidal antibody (1:128) and significant aggregation of TROMP (88.6%); approximately 50% of these aggregates contained four to six particles. The results indicate that complete immunity in experimental rabbit syphilis correlates with antibody that killsT. pallidumand aggregates TROMPs, suggesting that TROMPs are molecules which contribute to the development of acquired immunity.
Enhanced In Vivo Immune Responses to Bacterial Lipopolysaccharide by Exogenous CD40 Stimulation
Authors: Barr Tom A. , Heath Andrew W. 
Published: December 2019

ABSTRACT
The lack of specific T-cell help in immune responses to thymus-independent antigens results in weak, predominantly immunoglobulin M-mediated immunity with little or no memory. In the work presented here we show how the exogenous stimulation of CD40 by monoclonal antibodies can mimic T-cell help, resulting in enhanced immune responses which are protective against bacterial infection.
Development of a System for Expressing Heterologous Genes in the Oral SpirocheteTreponema denticolaand Its Use in Expression of theTreponema pallidum flaAGene
Authors: Chi Bo , Chauhan Sarita , Kuramitsu Howard 
Published: December 2019

ABSTRACTThe present communication describes the construction of a newEscherichia coli-Treponema denticolashuttle vector based on the naturally occurring spirochete plasmid pTS1 and the expression of the heterologousT. pallidum flaAgene from the plasmid inT. denticola. This new shuttle vector system should prove useful in characterizing virulence factors from unculturable pathogenic spirochetes.
Legionella pneumophilaContains a Type II General Secretion Pathway Required for Growth in Amoebae as Well as for Secretion of the Msp Protease
Authors: Hales Laura M. , Shuman Howard A. 
Published: December 2019

ABSTRACTWe report the identification of a set ofLegionella pneumophilagenes that encode products with homology to proteins of the type II general secretion pathway of gram-negative bacteria. A strain containing a deletion-substitution mutation of two of these genes was unable to secrete the Msp protease. This strain was unable to multiply within the free-living amoebaAcanthamoeba castellaniiyet was able to kill HL-60-derived macrophages. Because Msp is not required for growth in amoebae, other proteins which are important for growth in amoebae are likely secreted by this pathway.
Isolation and Characterization of a
sigB
Deletion Mutant of
Staphylococcus aureus
Authors: Nicholas R. O. , Li Tong , McDevitt D. , Marra Andrea , Sucoloski S. , Demarsh P. L. , Gentry D. R. 
Published: December 2019

ABSTRACT

The
sigB
gene of
Staphylococcus aureus
, coding for the alternate sigma factor B, has been deleted by allelic replacement mutagenesis. The mutant grew as well as the parent in vitro, although it was deficient in clumping factor, coagulase, and pigment. In two murine and one rat infection model the mutant showed no reduction in virulence.
Human Monocytic U937 Cells Kill
Salmonella
In Vitro by NO-Independent Mechanisms
Authors: Ekman Päivi , Saarinen Marja , He Qiushui , Virtala Mika , Salmi Marko , Granfors Kaisa 
Published: December 2019

ABSTRACT

Nitric oxide (NO) has a central role in host defense against intracellular microbes. HLA-B27 has been shown to directly modulate host-microbe interaction in vitro, leading to the impaired elimination of
Salmonella
in human monocytic U937 cells. Here, we studied whether impaired elimination of
Salmonella
would result from differences in NO production between HLA-B27- and HLA-A2-transfected U937 cells. Both human monocytic transfectants produced NO equally well and killed
Salmonella
via NO-independent mechanisms.
Anti-CD14 Monoclonal Antibodies Inhibit the Production of Tumor Necrosis Factor Alpha and Interleukin-10 by Human Monocytes Stimulated with Killed and LiveHaemophilus influenzaeorStreptococcus pneumoniaeOrganisms
Authors: van Furth A. Marceline , Verhard-Seijmonsbergen Els M. , Langermans Jan A. M. , van Dissel Jaap T. , van Furth Ralph 
Published: December 2019

ABSTRACTIn previous studies, we have shown that intact, heat-killed, gram-negative bacteria (GNB) and gram-positive bacteria (GPB) can stimulate the production of various proinflammatory and anti-inflammatory cytokines. The objective of the present study was to investigate whether the production of tumor necrosis factor alpha (TNF) and interleukin-10 (IL-10) by human monocytes stimulated by intact heat-killed or liveHaemophilus influenzaeorStreptococcus pneumoniaeis mediated by CD14. Two anti-CD14 monoclonal antibodies (MAbs) were used to study the interaction between human monocytes and bacteria; lipopolysaccharide (LPS) was used to validate the effect of anti-CD14 MAb. MAb 18E12 decreased significantly TNF and IL-10 production upon stimulation with LPS or heat-killed bacteria and TNF production during stimulation by live bacteria. MAb My-4 decreased production of TNF and IL-10 by monocytes stimulated with LPS, IL-10 but not TNF production upon stimulation with heat-killedH. influenzae, and production of neither TNF nor IL-10 upon stimulation withS. pneumoniae. Together, these results led to the conclusion that CD14 is involved in the recognition and stimulation of human monocytes by intact GNB and GPB. Consequentially, the option for adjunctive treatment of severe infections with anti-CD14 MAb is postulated.
Role of Phospholipase D inPasteurella haemolyticaLeukotoxin-Induced Increase in Phospholipase A2Activity in Bovine Neutrophils
Authors: Wang Zuncai , Clarke Cyril R. , Clinkenbeard Kenneth D. 
Published: December 2019

ABSTRACTThe effects ofPasteurella haemolyticaleukotoxin (LKT) on the activity of phospholipase D (PLD) and the regulatory interaction between PLD and phospholipase A2(PLA2) were investigated in assays using isolated bovine neutrophils labeled with tritiated phospholipid substrates of the two enzymes. Exposure of [3H]lysophosphatidylcholine-labeled neutrophils to LKT caused concentration- and time-dependent production of phosphatidic acid (PA), the product of PLD. LKT-induced generation of PA was dependent on extracellular calcium. Both production of PA and metabolism of [3H]-arachidonate ([3H]AA)-labeled phospholipids by PLA2were inhibited when ethanol was used to promote the alternative PLD-mediated transphosphatidylation reaction, resulting in the production of phosphatidylethanol rather than PA. The role of PA in regulation of PLA2activity was then confirmed by means of an add-back experiment, whereby addition of PA in the presence of ethanol restored PLA2-mediated release of radioactivity from neutrophil membranes. Considering the involvement of chemotactic phospholipase products in the pathogenesis of pneumonic pasteurellosis, development and use of anti-inflammatory agents that inhibit LKT-induced activation of PLD and PLA2may improve therapeutic management of the disease.
CTLA-4 Blockade Enhances the Immune Response Induced by Mycobacterial Infection but Does Not Lead to Increased Protection
Authors: Kirman Joanna , McCoy Kathy , Hook Sarah , Prout Melanie , Delahunt Brett , Orme Ian , Frank Anthony , Le Gros Graham 
Published: December 2019

ABSTRACTThe murine immune response to a pulmonary mycobacterial infection is slow to develop, allowing bacterial numbers to increase in the lung for several weeks after infection. We sought to enhance the protective immune response induced duringMycobacterium bovisBCG infection by administering an antibody that blocks the interaction of CTLA-4 with its ligands, CD80 and CD86. We found that injection of anti-CTLA-4 monoclonal antibody (MAb) greatly enhanced and accelerated the immune response, as measured by increased cellularity of the draining mediastinal lymph nodes, and enhanced antigen-inducible proliferation and gamma interferon production by mediastinal lymphocytes in vitro. However, despite the apparently enhanced immune response in the mediastinal lymph node following treatment with anti-CTLA-4 MAb, there was no improvement in clearance of mycobacteria in the lungs, liver, or spleen. Examination of the primary site of infection, the lung, revealed that CTLA-4 blockade had no effect on the number or function of lymphocytes infiltrating the infected lung tissue. Taken together, these data suggest that in vivo CTLA-4 blockade enhances mycobacterial-infection-induced lymphocyte expansion and effector cell cytokine production in the draining lymph node but does not alter the number or function of lymphocytes at the primary site of infection and therefore does not lead to enhanced clearance of the infection.
Variable Carbohydrate Modifications to the Catalytic Chains of the RgpA and RgpB Proteases ofPorphyromonas gingivalisW50
Authors: Curtis Michael A. , Thickett Andrea , Slaney Jennifer M. , Rangarajan Minnie , Aduse-Opoku Joseph , Shepherd Philip , Paramonov Nikolay , Hounsell Elizabeth F. 
Published: December 2019

ABSTRACTProteases ofPorphyromonas gingivalisare considered to be important virulence determinants of this periodontal bacterium. Several biochemical isoforms of arginine-specific proteases are derived fromrgpAandrgpB. HRgpA is a heterodimer composed of the catalytic α chain noncovalently associated with a β adhesin chain derived from the C terminus of the initial full-length translation product. The catalytic α chain is also present as a monomer (RgpA) either free in solution or associated with membranes.rgpBlacks the coding region for the adhesin domain present inrgpAand yields only monomeric forms (RgpB) which again may be soluble or membrane associated. In this study, the catalytic chains of this unusual group of enzymes are shown to be differentially modified by the posttranslational addition of carbohydrate. A monoclonal antibody (MAb 1B5) raised to the monomeric RgpA did not react with the corresponding recombinant RgpA α chain expressed inEscherichia colibut was immunoreactive withP. gingivalislipopolysaccharide. MAb 1B5 also reacted with the membrane-associated forms of RgpA and RgpB but not with the heterodimeric HRgpA and the soluble form of RgpB. RgpA treated with denaturants was capable of binding to MAb 1B5 whereas treatment with periodate abolished this binding, suggesting the presence of carbohydrate residues within the epitope. Chemical deglycosylation abolished immunoreactivity with MAb 1B5 and caused a ∼30% reduction in the size of the membrane-associated enzymes. Monosaccharide analysis of HRgpA and RgpA demonstrated 2.1 and 14.4%, respectively, carbohydrate by weight of protein. Furthermore, distinct differences were detected in their monosaccharide compositions, indicating that these protease isoforms are modified not only to different extents but also with different sugars. The variable nature of these additions may have a significant effect on the structure, stability, and immune recognition of these protease glycoproteins.
Molecular Characterization of the Hemin Uptake Locus (
hmu
) from
Yersinia pestis
and Analysis of
hmu
Mutants for Hemin and Hemoprotein Utilization
Authors: Thompson Jan M. , Jones Heather A. , Perry Robert D. 
Published: December 2019

ABSTRACT

Sequence analysis of the hemin uptake locus (
hmu
) of
Yersinia pestis
revealed five genes,
hmuRSTUV
, required for use of hemin and hemoproteins as iron sources. The translated gene products have homologies with proteins of the hemin transport genes of several gram-negative bacteria. Promoters were identified upstream of
hmuP′R
(p1) and upstream of
hmuS
(p2); p1, which contains a Fur box, is regulated by iron and Fur, while p2 exhibits weak, but constitutive, activity. HmuR, which has homology with TonB-dependent outer membrane (OM) receptors, is localized to the OM of
Y. pestis
and is required for utilizing hemin and all hemoproteins under iron-depleted conditions. The proposed ABC transporter, HmuTUV, is necessary for use of hemin, hemin-albumin, and myoglobin, but not hemoglobin, hemoglobin-haptoglobin, or heme-hemopexin, as iron sources. In the absence of HmuTUV, HmuS, a cytoplasmic protein, is involved in use of hemoglobin and heme-hemopexin. In mice, the 50% lethal doses of
Y. pestis
Δ
hmuP′RSTUV
mutants injected subcutaneously or retro-orbitally did not differ from that of the Hmu
+
parent strain. Thus, the
hmu
system is not essential for infection in mice via these routes. Growth studies showed that a Δ
hmuP′RSTUV
mutant could grow in iron-depleted medium containing high concentrations of hemoglobin, suggesting that an Hmu-independent, lower-affinity hemoglobin uptake system may exist.
Inactivation of the
gbpA
Gene of
Streptococcus mutans
Alters Structural and Functional Aspects of Plaque Biofilm Which Are Compensated by Recombination of the
gtfB
and
gtfC
Genes
Authors: Hazlett Karsten R. O. , Mazurkiewicz Joseph E. , Banas Jeffrey A. 
Published: December 2019

ABSTRACT

Inactivation of the
gbpA
gene of
Streptococcus mutans
increases virulence in a gnotobiotic rat model and also promotes in vivo accumulation of organisms in which
gtfB
and
gtfC
have recombined to reduce virulence (K. R. O. Hazlett, S. M. Michalek, and J. A. Banas, Infect. Immun. 66:2180–2185, 1998). These changes in virulence were hypothesized to result from changes in plaque structure. We have utilized an in vitro plaque model to test the hypothesis that the absence of GbpA alters
S. mutans
plaque structure and that the presence of
gtfBC
recombinant organisms within a
gbpA
background restores a wild-type (wt)-like plaque structure. When grown in the presence of sucrose within hydroxyapatite-coated wells, the wt
S. mutans
plaque consisted primarily of large aggregates which did not completely coat the hydroxyapatite surface, whereas the
gbpA
mutant plaque consisted of a uniform layer of smaller aggregates which almost entirely coated the hydroxyapatite. If 25% of the
gbpA
mutants used as inoculum were also
gtfBC
recombinants (
gbpA
/25%
gtfBC
), a wt-like plaque was formed. These changes in plaque structure correlated with differences in susceptibility to ampicillin;
gbpA
plaque organisms were more susceptible than organisms in either the wt or
gbpA
/25%
gtfBC
plaques. These data allow the conclusion that GbpA contributes to
S. mutans
plaque biofilm development. Since the changes in plaque structure detailed in this report correlate well with previously observed changes in virulence, it seems likely that
S. mutans
biofilm structure influences virulence. A potential model for this influence, which can account for the
gtfBC
recombination compensating
gbpA
inactivation, is that the ratio of glucan to glucan-binding protein is a critical factor in plaque development.
Plasmin-Coated
Borrelia burgdorferi
Degrades Soluble and Insoluble Components of the Mammalian Extracellular Matrix
Authors: Coleman James L. , Roemer Elizabeth J. , Benach Jorge L. 
Published: December 2019

ABSTRACT

Borrelia burgdorferi
, the spirochetal agent of Lyme disease, binds plasminogen in vitro. Exogenously provided urokinase-type plasminogen (PLG) activator (uPA) converts surface-bound PLG to enzymatically active plasmin. In this study, we investigated the capacity of a
B. burgdorferi
human isolate, once complexed with plasmin, to degrade purified extracellular matrix (ECM) components and an interstitial ECM. In a modified enzyme-linked immunosorbent assay using immobilized, soluble ECM components, plasmin-coated
B. burgdorferi
degraded fibronectin, laminin, and vitronectin but not collagen. Incubation of plasmin-coated organisms with biosynthetically radiolabeled native ECM resulted in breakdown of insoluble glycoprotein, other noncollagenous proteins, and collagen, as measured by release of solubilized radioactivity. Radioactive release did not occur with untreated spirochetes or spirochetes treated with uPA or PLG alone. Kinetic and inhibition studies suggested that the breakdown of collagen was indirect and due to prior disruption of supportive ECM proteins.
B. burgdorferi
is an invasive bacterial pathogen that may benefit by use of the host’s plasminogen activation system. The results of this study have identified mechanisms in which the spirochete can use this borrowed proteolytic activity to enhance invasiveness.
Trypanosoma cruziInfects Human Dendritic Cells and Prevents Their Maturation: Inhibition of Cytokines, HLA-DR, And Costimulatory Molecules
Authors: Van Overtvelt Laurence , Vanderheyde Nathalie , Verhasselt Valérie , Ismaili Jamila , De Vos Louis , Goldman Michel , Willems Fabienne , Vray Bernard 
Published: December 2019

ABSTRACTTrypanosoma cruzi, a parasitic protozoan, is the etiological agent of Chagas’ disease. Despite the many immune system disorders recognized in this infection and the crucial role played by dendritic cells (DC) in acquired immune responses, it was not known whether these cells could be infected byT. cruzitrypomastigotes and the consequences of such an infection on their immune functions. We now provide evidence that human monocyte-derived DC can be infected byT. cruziand can support its intracellular multiplication. Interestingly, this infection has functional consequences on immature DC and on their maturation induced by lipopolysaccharide (LPS). First, afterT. cruziinfection, the basal synthesis of interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-α) was impaired. Furthermore, the process of maturation of DC induced by LPS was drastically affected byT. cruziinfection. Indeed, secretion of cytokines such as IL-12, TNF-α, and IL-6, which are released normally at high levels by LPS-activated DC, as well as the up-regulation of HLA-DR and CD40 molecules, was significantly reduced after this infection. The same effects could be induced byT. cruzi-conditioned medium, indicating that at least these inhibitory effects were mediated by soluble factors released byT. cruzi. Taken together, these results provide new insights into a novel efficient mechanism, directly involving the alteration of DC function, which might be used byT. cruzito escape the host immune responses in Chagas’ disease and thus might favor persistent infection.
Cell-Mediated Immune Responses in Four-Year-Old Children after Primary Immunization with Acellular Pertussis Vaccines
Authors: Ausiello Clara M. , Lande Roberto , Urbani Francesca , la Sala Andrea , Stefanelli Paola , Salmaso Stefania , Mastrantonio Paola , Cassone Antonio 
Published: December 2019

ABSTRACT

Cell-mediated immune (CMI) responses to
Bordetella pertussis
antigens (pertussis toxin [PT], pertactin [PRN], and filamentous hemagglutinin [FHA]) were assessed in 48-month-old recipients of acellular pertussis [aP] vaccines (either from Chiron-Biocine [aP-CB] or from SmithKline Beecham [aP-SB]) and compared to CMI responses to the same antigens at 7 months of age, i.e., 1 month after completion of the primary immunization cycle. None of the children enrolled in this study received any booster of pertussis vaccines or was affected by pertussis during the whole follow-up period. Overall, around 75% of 4-year-old children showed a CMI-positive response to at least one
B. pertussis
antigen, independently of the type of aP vaccine received, and the proportion of CMI responders were at least equal at 48 and 7 months of age. However, longitudinal examination of individual responses showed that from 20 (against PT) to 37% (against FHA) of CMI responders after primary immunization became negative at 48 months of age. This loss was more than compensated for by conversion to positive CMI responses, ranging from 36% against FHA to 69% against PRN, in other children who were CMI negative at 7 months of age. In 60 to 80% of these CMI converters, a lack of decline or even marked elevation of antibody (Ab) titers against
B. pertussis
antigens also occurred between 20 and 48 months of age. In particular, the frequency of seropositivity to PRN and FHA (but not to PT) was roughly three times higher in CMI converters than in nonconverters. The acquisition of CMI response to
B. pertussis
antigens in 48-month-old children was not associated with a greater frequency of coughing episodes lasting ≥7 days and was characterized by a prevalent type 1 cytokine profile, with high gamma interferon and low or no production of interleukin-5, reminiscent of cytokine patterns following immunization with whole-cell pertussis vaccine or natural infection. Our data imply that vaccination-induced systemic CMI may wane by 4 years of age but may be acquired or naturally boosted by symptomless or minor clinical infection by
B. pertussis
. This might explain, at least in part, the persistence of protection against typical pertussis in aP vaccine recipients despite a substantial waning of both Ab and CMI responses induced by the primary immunization.