bluuebunny/crossref_metadata_2025 huggingface dataset:
The intracellular bacterium Rhodococcus equi requires Mac-1 to bind to mammalian cells
Authors: Hondalus M K , Diamond M S , Rosenthal L A , Springer T A , Mosser D M
Published: January 2020

Rhodococcus equi is a facultative intracellular bacterium of macrophages that causes disease in immunocompromised individuals, particularly those with AIDS. In this report, we demonstrate that R. equi binding to mammalian cells requires complement and is mediated primarily by the leukocyte complement receptor, Mac-1. Bacteria bind to macrophages poorly unless exogenous complement is added to the incubation medium. The addition of fresh nonimmune serum, which contains no detectable antibodies to R. equi, greatly enhances bacterial binding to macrophages, whereas heat inactivation of this serum or immunological depletion of C3 from the serum reduces binding to levels only slightly higher than those of binding under serum-free conditions. Human serum depleted of C2 or C4 is fully opsonic, indicating that complement activation and fixation occur by the alternative pathway. The serum-dependent binding of rhodococci to macrophages is mediated primarily by the macrophage complement receptor type 3, Mac-1 (CD11b/CD18). Bacteria do not bind to fibroblastoid or epithelial cells that lack this receptor. Most of the bacterial binding to macrophages is inhibited by a monoclonal antibody to Mac-1 but is unaffected by a monoclonal antibody to complement receptor type 1. Furthermore, opsonized, but not unopsonized, bacteria bind to purified Mac-1 immobilized on plastic. In addition, in the presence of opsonic complement, rhodococci bind efficiently to fibroblastoid cells transfected with cloned Mac-1 but relatively poorly to cells transfected with the complement receptor type 1. Hence, R. equi fixes complement by activating the alternative complement pathway, and this fixation is a requirement for bacterial adhesion and invasion. Furthermore, complement fixation defines rhodococcal host cell tropism, since R. equi binds specifically and exclusively to cells expressing Mac-1.
Detection of a prfA-independent promoter responsible for listeriolysin gene expression in mutant Listeria monocytogenes strains lacking the PrfA regulator
Authors: Domann E , Wehland J , Niebuhr K , Haffner C , Leimeister-Wächter M , Chakraborty T
Published: January 2020

Expression of listeriolysin, a major virulence factor of pathogenic Listeria monocytogenes, is positively regulated by the pleiotropic virulence regulator PrfA. In this study, we demonstrate that L. monocytogenes strains lacking the prfA regulator gene produce listeriolysin in small, albeit detectable, amounts when analyzed in a hemolysin assay and by immunoblots with listeriolysin-specific monoclonal antibodies. Transcriptional analysis revealed the existence of a PrfA-independent promoter that was responsible for the hemolytic activity expressed by these strains.
Distribution of bacterial endotoxin in human and rabbit blood and effects of stroma-free hemoglobin
Authors: Roth R I , Levin F C , Levin J
Published: January 2020

Bacterial endotoxin (lipopolysaccharide [LPS]) is known to interact with numerous components of blood, including erythrocytes, mononuclear cells, platelets, neutrophils, lipoproteins, and plasma proteins. The relative affinities of LPS for these elements, and the distribution of LPS between them, are unknown. Cross-linked stroma-free hemoglobin (SFH), a potential substitute for erythrocyte transfusion, produces in vivo toxicity in animals consistent with significant LPS contamination. Therefore, we studied the distribution of LPS in human and rabbit blood and examined whether the presence of SFH altered LPS distribution. In either the presence or absence of SFH, LPS was associated predominantly with high-density lipoproteins and apoproteins. There was lesser binding to low- and very-low-density lipoproteins. Examination of the apoprotein pool by column chromatography and density centrifugation demonstrated that LPS in this fraction was predominantly protein bound. Binding of LPS to SFH resulted in dissociation of a portion of the LPS into low-molecular-weight complexes. Cell-bound LPS was only 2 to 16% of the total and was unaffected by SFH. The distribution among blood cells demonstrated predominant binding to platelets in human blood but predominant binding to erythrocytes in rabbit blood. Cellular distribution was not significantly altered by SFH.
A single amino acid change in AngR, a protein encoded by pJM1-like virulence plasmids, results in hyperproduction of anguibactin
Authors: Tolmasky M E , Actis L A , Crosa J H
Published: January 2020

The siderophore anguibactin is produced in vivo in a diffusible form and is an important factor in the virulence of Vibrio anguillarum. The natural isolate V. anguillarum 531A is a hyperproducer of anguibactin when compared with the prototype strain V. anguillarum 775. The angR gene was found to be responsible for this difference in levels of anguibactin produced. Nucleotide sequence analysis showed that the angR531A differed in a single nucleotide from the angR775 present in the prototype plasmid pJM1. This nucleotide substitution resulted in a change in amino acid 267 from His in strain 775 to Asn in strain 531A. This amino acid is located in a region between one of the two helix-turn-helix domains and the neighboring leucine zipper. Mutations to replace His with either Leu or Gln, generated by site-directed mutagenesis, in amino acid 267 resulted in strains for which the MIC of the iron chelator ethylenediamine di(o-hydroxyphenyl) acetic acid were lower than for the proptotype 775 but higher than for iron uptake-deficient strains. In addition to its transcriptional activating function, AngR also complemented a mutation in the Escherichia coli entE gene, which encodes the enterobactin biosynthetic enzyme 2,3-dihydroxybenzoate-AMP ligase. Therefore, AngR may also function in V. anguillarum as an EntE-like enzyme for the biosynthesis of anguibactin.
Immune recognition of polar pili from Pseudomonas aeruginosa O
Authors: Smart W , Sastry P A , Paranchych W , Singh B
Published: January 2020

The B- and T-cell antigenic sites on type O pili from Pseudomonas aeruginosa were determined by using an antipilus antibody competition assay and PAO-immune T-cell blasts in proliferation studies. The citraconylated tryptic digest III region (residues 54 to 120) was determined to be an immunodominant site for both T and B cells on the pilin molecule.
Ehrlichia chaffeensis expresses an immunoreactive protein homologous to the Escherichia coli GroEL protein
Authors: Sumner J W , Sims K G , Jones D C , Anderson B E
Published: January 2020

A clone expressing a 58-kDa protein reactive with human convalescent-phase serum was isolated from a recombinant library of Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis. Sequencing identified two open reading frames, one encoding a 10.3-kDa polypeptide consisting of 94 amino acids and another encoding a 58-kDa polypeptide consisting of 550 amino acids. The sequences of the 10.3- and 58-kDa polypeptides were homologous to those of the Escherichia coli GroES and GroEL heat shock proteins, respectively.
Role of Porphyromonas gingivalis-derived fibroblast-activating factor in bone resorption
Authors: Mihara J , Yoneda T , Holt S C
Published: January 2020

A 24-kDa protein was isolated from the outer membrane vesicles of Porphyromaonas gingivalis W50. This protein, referred to as fibroblast-activating factor (FAF), was examined for its bone-resorptive ability by the rat long-bone assay and the mouse bone marrow cell culture system. FAF resulted in a significant release of 45Ca from cultured bones, as well as the formation of tartrate-resistant acid phosphatase-positive monocytes. These cultures were compared with control cells. FAF therefore might be considered a significant bacterially expressed protein which could affect and modulate the resorption or destruction of tissue and alveolar bone in the local periodontal environment.
The Mycobacterium leprae antigen 85 complex gene family: identification of the genes for the 85A, 85C, and related MPT51 proteins
Authors: Rinke de Wit T F , Bekelie S , Osland A , Wieles B , Janson A A , Thole J E
Published: January 2020

The genes for two novel members (designated 85A and 85C) of the Mycobacterium leprae antigen 85 complex family of proteins and the gene for the closely related M. leprae MPT51 protein were isolated. The complete DNA sequence of the M. leprae 85C gene and partial sequences of the 85A and MPT51 genes are presented. As in M. tuberculosis, the M. leprae 85A, 85C, and previously identified 85B component genes are not closely linked on the genome. However, the MPT51 genes of both species localize close to the respective 85A component genes. Like the 85B component, the M. leprae 85A-MPT51 and 85C antigens are recognized by T cells from healthy contacts and leprosy patients.
Analysis of cytokine mRNA expression in Listeria-resistant C57BL/6 and Listeria-susceptible A/J mice during Listeria monocytogenes infection
Authors: Iizawa Y , Wagner R D , Czuprynski C J
Published: January 2020

This laboratory previously reported that mRNA expression for many cytokines, as determined by reverse transcription-polymerase chain reaction analysis, is induced rapidly in the spleen during murine listeriosis. In the present study, the patterns of cytokine mRNA expression in spleens and livers of Listeria-resistant C57BL/6 and Listeria-susceptible A/J mice were compared. In addition, in situ hybridization was performed to evaluate the distributions of cytokine mRNA-expressing cells in these tissues. Listeria-resistant C57BL/6 mice demonstrated greater expression of gamma interferon (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNAs in the spleen than Listeria-susceptible A/J mice. Greater numbers of cells expressing IFN-gamma and GM-CSF mRNAs were observed by in situ hybridization in the spleens of C57BL/6 mice than in those of A/J mice. C57BL/6 and A/J mice did not differ in their expression of IFN-gamma mRNA in the liver. Nor did C57BL/6 and A/J mice differ in their expression of tumor necrosis factor alpha, interleukin-1 alpha (IL-1 alpha), IL-2, IL-4, or IL-6 mRNA in the liver or spleen, as determined by reverse transcription-polymerase chain reaction and in situ hybridization. These results indicate that the greater resistance of C57BL/6 mice to Listeria monocytogenes infection is associated with greater expression of IFN-gamma and GM-CSF mRNAs in the spleen and GM-CSF mRNA in the liver.
Purification and partial characterization of a product from Yersinia pseudotuberculosis with the ability to activate human T cells
Authors: Miyoshi-Akiyama T , Imanishi K , Uchiyama T
Published: January 2020

We tried to purify a substance exhibiting mitogenicity for human peripheral blood lymphocytes from Yersinia pseudotuberculosis isolated from patients with Y. pseudotuberculosis infection manifesting acute and systemic clinical symptoms. The supernatant of a suspension of the bacteria disrupted by sonication was serially chromatographed on DEAE-Sepharose fast-flow, Sephacryl S-100 HR, and TSK-gel G2000SW high-pressure liquid chromatography columns. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the purified mitogenically active substance migrated as a single band corresponding to a molecular mass of 21 kDa. We designated the purified substance Y. pseudotuberculosis-derived mitogen (YPM). YPM stimulated human peripheral T cells to proliferate and produce interleukin-2 at 0.1 ng/ml or more. YPM-induced T-cell activation required the expression of HLA class II molecules on accessory cells.
2-Deoxy-D-glucose inhibits intracellular multiplication and promotes intracellular killing of Legionella pneumophila in A/J mouse macrophages
Authors: Ogawa M , Yoshida S , Mizuguchi Y
Published: January 2020

Legionella pneumophila can grow intracellularly in A/J mouse macrophages. 2-Deoxy-D-glucose (2dG) (0.1, 1, and 10 mM) inhibited intracellular multiplication and promoted intracellular killing of L. pneumophila dose dependently when it was added to the culture medium of macrophage monolayers, whereas it did not inhibit the bacterial growth in buffered yeast extract broth, which was used for an L. pneumophila culture. The effect of 2dG was reversible because the surviving bacteria resumed intracellular multiplication after the washing away of 2dG from the culture. The effect of 2dG was also competitively inhibited by high concentrations of glucose. The inhibitory effect of 2dG was not attributed to the inhibition of bacterial phagocytosis by macrophages. Furthermore, sodium fluoride (0.1 and 1 mM), cycloheximide (0.1 and 1 microgram/ml), and tunicamycin (1, 2, and 5 micrograms/ml) did not promote the killing of L. pneumophila in macrophages, implying that the inhibitory effect of 2dG cannot be attributed to the inhibition of glycolysis, protein synthesis, and protein glycosylation in macrophages. We suggest that 2dG promotes intracellular killing of L. pneumophila by activating some novel killing mechanism of macrophages.
Depression of liver metabolism and induction of cytokine release by diphtheria and tetanus toxoids and pertussis vaccines: role of Bordetella pertussis cells in toxicity
Authors: Fantuzzi G , Sironi M , Delgado R , Cantoni L , Rizzardini M , Carelli M , Marsili I , Ghiara P , Ghezzi P
Published: January 2020

A 24-h pretreatment of mice with diphtheria and tetanus toxoids and whole-cell pertussis vaccines depressed liver cytochrome P-450 and therefore prolonged hexobarbital-induced sleeping time in mice. The depression of liver drug metabolism by a cellular vaccine containing a mutated pertussis toxin was less marked than that induced by the wild-type vaccines, indicating that the mutated vaccine might have lower toxicity in this regard. The wild-type vaccines decreased microsomal P-450 levels by 50%, while the mutated whole-cell vaccine had a less marked effect (a decrease of 30%), paralleling the results obtained in sleeping time experiments. Furthermore, an acellular mutated vaccine did not affect liver drug metabolism, indicating a role of the whole bacterial cell in this side effect. All the cellular vaccines studied induced high serum interleukin-6 levels; on the other hand, the acellular mutated vaccine induced very low interleukin-6 levels, indicating that the whole bacterial cell is also important for interleukin-6 induction. All vaccines studied were very poor tumor necrosis factor inducers.
Variations in the ospB gene of Borrelia burgdorferi result in differences in monoclonal antibody reactivity and in production of escape variants
Authors: Coleman J L , Rogers R C , Rosa P A , Benach J L
Published: January 2020

An escape variant of Borrelia burgdorferi, selected with a monoclonal antibody to OspB, expressed a truncated form of OspB, the result of point mutations in the ospB gene leading to a premature termination codon. A single amino acid position in the C terminus of OspB was critical for monoclonal antibody recognition. The variations in the ospB gene suggest a mechanism for the evasion of the immune response by these organisms and may also have implications for current diagnostic and vaccine efforts.
Construction of a series of congenic mice with recombinant chromosome 1 regions surrounding the genetic loci for resistance to intracellular parasites (Ity, Lsh, and Bcg), DNA repair responses (Rep-1), and the cytoskeletal protein villin (Vil)
Authors: Mock B A , Holiday D L , Cerretti D P , Darnell S C , O'Brien A D , Potter M
Published: January 2020

The interval of mouse chromosome 1 extending from Idh-1 to Pep-3 harbors the natural resistance gene Ity/Lsh/Bcg; it controls the outcome of infection with Salmonella typhimurium, Leishmania donovani, and several Mycobacterium species. This region also contains a DNA repair gene, Rep-1, which determines the rapidity with which double-strand breaks in chromatin are repaired. BALB/cAnPt and DBA/2N mice differ in their phenotypic expression of these genes. To generate appropriate strains of mice for the study of these genes, a series of 10 C.D2 congenic strains recombinant across a 28-centimorgan interval of mouse chromosome 1 extending from Idh-1 to Pep-3 were derived from crosses of the C.D2-Idh-1 Pep-3 congenic strain back to BALB/cAn. Analyses of these recombinant strains will allow the correlation of biological-immunological phenotypes with defined genetic regions.
ToxR regulates virulence gene expression in non-O1 strains of Vibrio cholerae that cause epidemic cholera
Authors: Waldor M K , Mekalanos J J
Published: January 2020

Vibrio cholerae serogroup O1 has historically been thought to be the exclusive cause of epidemic cholera. O139 is a novel serogroup of V. cholerae which emerged on the Indian subcontinent in the last few months of 1992 and is the first non-O1 serogroup of V. cholerae to cause epidemic cholera. We have investigated the expression of some of the known virulence factors of classical and El Tor O1 strains of V. cholerae in clinical isolates of O139 strains. We show that, in contrast to other non-O1 strains, O139 strains express TcpA, the major subunit of the toxin-coregulated pilus found in O1 strains. As in O1 strains, the expression of cholera toxin and TcpA is coordinately regulated by environmental parameters in O139 strains. Derivatives of O139 strains that contain a toxR null mutation were constructed and used to demonstrate that the expression of cholera toxin, TcpA, and the outer membrane protein OmpU in O139 strains, as in O1 strains, is dependent on ToxR. Two kinds of evidence suggest that O139 strains are closely related to El Tor strains of V. cholerae. First, both O139 and El Tor strains share a restriction fragment length polymorphism for tcpA, which distinguishes El Tor from classical strains of V. cholerae. Second, cholera toxin production in O139 strains is greatly enhanced by culture conditions that have been previously shown to promote production of cholera toxin in El Tor strains and not in classical strains of V. cholerae. Although O139 is a novel serotype of V. cholerae, O139 strains conform to a fundamental theme that has evolved from the study of O1 strains: ToxR mediates coordinate regulation of virulence gene expression.
Staphylococcal glycocalyx activates macrophage prostaglandin E2 and interleukin 1 production and modulates tumor necrosis factor alpha and nitric oxide production
Authors: Stout R D , Li Y , Miller A R , Lambe D W
Published: January 2020

We have examined the effect of staphylococcal glycocalyces on the ability of murine peritoneal macrophages to produce prostaglandin E2 (PGE2) and the inflammatory cytokines interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF-alpha) and to generate nitric oxide. Glycocalyx partially purified under endotoxin-free conditions from defined liquid medium cultures of Staphylococcus lugdunensis or Staphylococcus epidermidis was a strong stimulator of PGE2 and IL-1 production. The addition of 10 to 100 micrograms of glycocalyx per ml induced levels of IL-1 and PGE2 production similar to that induced by 0.1 to 1 micrograms of Escherichia coli lipopolysaccharide (LPS) per ml. In contrast, glycocalyx induced ninefold less TNF-alpha and three- to fourfold less nitrite than LPS. A modulatory effect was suggested by the observation that the amount of TNF-alpha and nitrite generated remained constant whether the macrophages were stimulated with 10 or 100 micrograms of glycocalyx per ml. A selective modulation of macrophage activation was confirmed by the demonstration that costimulation of macrophages with both glycocalyx and LPS resulted in a reduction in TNF-alpha and nitrite generation relative to stimulation with LPS alone even though costimulation had no effect on PGE2 production and increased IL-1 production. Involvement of PGE2 in this modulatory effect was suggested by the ability of indomethacin to augment glycocalyx-stimulated TNF-alpha production and to reverse the inhibitory effect of glycocalyx on LPS induction of TNF-alpha production. However, the inability of indomethacin to reverse the inhibitory effect of glycocalyx on LPS-induced nitric oxide generation suggests that the selective modulation of macrophage function by glycocalyx may be more complex than increased sensitivity to PGE2 feedback inhibition.
Influence of polyclonal immunoglobulins on the polymorphonuclear leukocyte response to lipopolysaccharide of Salmonella enteritidis as measured with luminol-enhanced chemiluminescence
Authors: Wagner D R , Heinrich D
Published: January 2020

In gram-negative sepsis, the activation of polymorphonuclear leukocytes (PMN) by lipopolysaccharide (LPS) and the resulting production of superoxide and other oxygen radicals may be an important cause of tissue damage. A suppression of the PMN response to LPS stimulation would be therapeutically beneficial. The aim of this study was to determine whether different polyclonal immunoglobulins (Igs; 5S-Ig, 7S-Ig, and 19S-Ig) influence the PMN response to LPS of Salmonella enteritidis in vitro. The respiratory burst activity of PMN was measured with luminol-enhanced chemiluminescence. After addition of a 5S-Ig solution containing F(ab')2 fragments of IgG and a 19S-Ig solution containing 12% polyclonal IgM, luminol-enhanced chemiluminescence was reduced by 27% (P < 0.05) and 46% (P < 0.005), respectively. However, after addition of a 7S-Ig solution containing polyclonal IgG, luminol-enhanced chemiluminescence was increased fourfold (P < 0.05). The results suggest that the influence of polyclonal Igs on PMN response to LPS stimulation is dependent on the Ig class, F(ab')2 fragments of IgG and IgM leading to LPS neutralization and IgG leading to the production of potentially toxic oxygen radicals.
Antigen provoking gamma interferon production in response to Mycobacterium bovis BCG and functional difference in T-cell responses to this antigen between viable and killed BCG-immunized mice
Authors: Kawamura I , Yang J , Takaesu Y , Fujita M , Nomoto K , Mitsuyama M
Published: January 2020

It has been shown that gamma interferon (IFN-gamma)-producing CD4+ T cells, which are generated only by immunization with viable bacteria, exert a significant role in protective immunity against mycobacteria in mice. In this study, we have tried to determine the antigen recognized by the T cells in search of a possible protective antigen. T cells from viable Mycobacterium bovis BCG-immunized mice were stimulated with several antigens, and IFN-gamma production was measured. Purified protein derivative and viable and killed BCG lysates caused significant IFN-gamma production, and almost the same level of IFN-gamma activity was detected in both groups stimulated with viable and killed BCG lysates. However, heat shock protein (HSP) 65 and HSP 70 were not a major antigen for IFN-gamma production. The antigen provoking IFN-gamma production is localized mainly in the membrane fraction of BCG cells, and the approximate molecular size was 18 kDa. On the other hand, T cells from killed BCG-immunized mice never responded to this antigen for IFN-gamma production, whereas they could mount a delayed-type hypersensitivity response. These results showed that the antigen provoking IFN-gamma production was present in killed as well as viable BCG. In addition to the antigen presentation by antigen-presenting cells, some kinds of differentiation factor (such as monokines) that are produced only by stimulation with viable cells seemed to be necessary for the development of IFN-gamma-producing T cells.
Identification of an immunoglobulin Fc receptor of Actinobacillus actinomycetemcomitans
Authors: Mintz K P , Fives-Taylor P M
Published: January 2020

Actinobacillus actinomycetemcomitans expresses proteins that bind to the Fc portion of immunoglobulins. The immunoglobulin Fc receptors on the surface of A. actinomycetemcomitans were detected by the binding of biotinylated human or murine Fc molecules to strain SUNY 465 adsorbed to the bottom of microtiter wells. Biotinylated Fc binding was inhibited by unlabeled Fc molecules and human plasma. Fc receptors were identified by the binding of biotinylated Fc molecules to bacterial membrane proteins separated by polyacrylamide gel electrophoresis and transferred to nitrocellulose. Multiple bands were identified, and the major Fc-binding protein was determined to be a heat-modifiable protein. This protein migrated with approximate molecular weights of 25,000 and 32,000 (unheated and heated, respectively). Amino-terminal sequence analysis of this protein revealed a sequence identical to the heat-modifiable protein described for A. actinomycetemcomitans ATCC 43718. This protein sequence exhibits significant homology with the N termini of outer membrane protein A (OmpA) of Escherichia coli and related OmpA-like proteins from other gram-negative bacteria.
Identification of a locus involved in the utilization of iron by Haemophilus influenzae
Authors: Sanders J D , Cope L D , Hansen E J
Published: January 2020

Haemophilus influenzae has an absolute requirement for heme for aerobic growth. This organism can satisfy this requirement by synthesizing heme from iron and protoporphyrin IX (PPIX). H. influenzae type b (Hib) strain DL42 was found to be unable to form single colonies when grown on a medium containing free iron and PPIX in place of heme. In contrast, the nontypeable H. influenzae (NTHI) strain TN106 grew readily on the same medium. A genomic library from NTHI strain TN106 was used to transform Hib strain DL42, and recombinants were selected on a medium containing iron and PPIX in place of heme. A recombinant plasmid with an 11.5-kb NTHI DNA insert was shown to confer on Hib strain DL42 the ability to grow on iron and PPIX. Nucleotide sequence analysis revealed that this NTHI DNA insert contained three genes, designated hitA, hitB, and hitC, which encoded products similar to the SfuABC proteins of Serratia marcescens, which have been shown to constitute a periplasmic binding protein-dependent iron transport system in this enteric organism. The NTHI HitA protein also was 69% identical to the ferric-binding protein of Neisseria gonorrhoeae. Inactivation of the cloned NTHI hitC gene by insertion of an antibiotic resistance cartridge eliminated the ability of the recombinant plasmid to complement the growth deficiency of Hib DL42. Construction of an isogenic NTHI TN106 mutant lacking a functional hitC gene revealed that this mutation prevented this strain from growing on a medium containing iron and PPIX in place of heme. This NTHI hitC mutant was also unable to utilize either iron bound to transferrin or iron chelates. These results suggest that the products encoded by the hitABC genes are essential for the utilization of iron by NTHI.
Biological activities of native and recombinant Borrelia burgdorferi outer surface protein A: dependence on lipid modification
Authors: Weis J J , Ma Y , Erdile L F
Published: January 2020

Borrelia burgdorferi lipoproteins are 50- to 500-fold more active as cytokine inducers and B-cell mitogens than Escherichia coli lipoproteins and synthetic peptides containing the tripalmitoyl-S-glyceryl-cysteine moiety. To investigate the source of this unique potency, we compared native OspA from B. burgdorferi with recombinant lipidated OspA produced in E. coli. As little as 10 ng of either protein per ml stimulated B-cell proliferation and production of cytokines and nitric oxide by macrophages. The two proteins induced comparable antibody responses in mice. Nonlipidated OspA made in E. coli had no stimulatory activity. Thus, lipid modification is essential both in vivo and in vitro for the immunological properties of OspA. The lipid moiety appears equally active whether produced in B. burgdorferi or in E. coli.
Interleukin-10 is expressed by bovine type 1 helper, type 2 helper, and unrestricted parasite-specific T-cell clones and inhibits proliferation of all three subsets in an accessory-cell-dependent manner
Authors: Brown W C , Woods V M , Chitko-McKown C G , Hash S M , Rice-Ficht A C
Published: January 2020

Murine interleukin-10 (IL-10) is produced by type 2 helper (Th2) cells and selectively inhibits cytokine synthesis by type 1 helper (Th1) cells, whereas human IL-10 is produced by and inhibits proliferation and cytokine synthesis by both Th1 and Th2 subsets. This study reports that bovine IL-10 mRNA is expressed by Th0, Th1, and Th2 clones of bovine T cells specific for either Babesia bovis or Fasciola hepatica but not by two CD8+ T-cell clones. The antigen-induced proliferative responses of all three subsets of CD4+ cells were inhibited by human IL-10, and low levels (10 U/ml) of exogenous human IL-2 restored the suppressed response. However, proliferation of one Th1 clone was never inhibited but was enhanced by IL-10. Human IL-10 also inhibited the expression of gamma interferon and IL-4 mRNA in Th0 clones. In the absence of accessory cells (AC), the responses of Th clones to concanavalin A or IL-2 were not inhibited by IL-10, whereas antigen-specific responses of Th1 and Th2 cells were reduced when IL-10-pretreated macrophages were used as AC. Together, our results with bovine T cells support the concept that IL-10 primarily affects AC function and does not directly inhibit CD4+ T cells and demonstrate that the immunoregulatory effects of IL-10 are not selectively directed at Th1 populations, as they are in mice.
Inhibition of bacterial motility with human antiflagellar monoclonal antibodies attenuates Pseudomonas aeruginosa-induced pneumonia in the immunocompetent rat
Authors: Landsperger W J , Kelly-Wintenberg K D , Montie T C , Knight L S , Hansen M B , Huntenburg C C , Schneidkraut M J
Published: January 2020

Two human monoclonal antibodies, directed against the type a and type b flagellar proteins of Pseudomonas aeruginosa, inhibited bacterial motility in vitro specifically and in a concentration-dependent manner. In order to determine if this decreased bacterial motility was associated with a decreased pathogenicity, the ability of these human antiflagellar monoclonal antibodies to attenuate P. aeruginosa-induced pneumonia in the rat was assessed. Incubation of P. aeruginosa with a 1:1 mixture of the human antiflagellar monoclonal antibodies prior to pulmonary instillation significantly (P < 0.05) ameliorated the bacterium-induced decrease in arterial blood oxygen pressure, blunted the increase in respiratory rate, and markedly reduced the area of pulmonary inflammation. Similarly, intravenous administration of the human antiflagellar monoclonal antibodies 1 h after pulmonary instillation of the bacteria also reduced the in vivo pathogenicity of P. aeruginosa. Therefore, human antiflagellar monoclonal antibodies can decrease the in vitro motility of P. aeruginosa and can reduce its in vivo pathogenicity when administered either before or after bacterial challenge.
Activation of human effector cells by different bacterial toxins (leukocidin, alveolysin, and erythrogenic toxin A): generation of interleukin-8
Authors: König B , Köller M , Prevost G , Piemont Y , Alouf J E , Schreiner A , König W
Published: January 2020

We analyzed the transcription and release of interleukin-8 (IL-8) from human polymorphonuclear granulocytes (PMNs) and a lymphocyte-monocyte-basophil (LMB) cell population stimulated for different time periods (30 min to 16 h) with pore-forming bacterial toxins (Panton-Valentine leukocidin [Luk-PV] and alveolysin [Alv]) as well as with the erythrogenic toxin A (ETA) as a superantigen. At high toxin concentrations (500 ng/10(7) cells), Luk-PV and Alv led to a decreased IL-8 generation from LMBs within the first 30 min; with PMNs, a slight increase in IL-8 release was observed. Under these conditions, stimulation with ETA did not lead to an altered cellular IL-8 release. At lower concentrations (5 and 0.5 ng/10(7) cells), all three toxins led to a continuous increase (over 16 h) in IL-8 release and IL-8 mRNA expression of PMNs and LMBs. Preincubation of the cells with the protein tyrosine kinase inhibitors lavendustin A and tyrphostin 25 led to a reduction of the toxin-mediated effects on IL-8 release and IL-8 mRNA expression when Luk-PV and Alv were used as stimuli. In contrast, IL-8 synthesis in cells which were stimulated with ETA was not influenced by protein tyrosine kinase inhibition. From our data, one may suggest that multiple pathways for IL-8 production are operative in human leukocytes.
Salmonella typhimurium invasion of epithelial cells: role of induced host cell tyrosine protein phosphorylation
Authors: Rosenshine I , Ruschkowski S , Foubister V , Finlay B B
Published: January 2020

Salmonella typhimurium invades nonphagocytic epithelial and fibroblast cells via a process resembling phagocytosis. We have compared some phenotypes that are involved in S. typhimurium invasion by using different host cell lines, including HeLa, Henle-407, and A431. Infection with either wild-type S. typhimurium, bacterial culture supernatant, or the noninvasive invA mutant was associated with induction of tyrosine phosphorylation of host cell mitogenic activating protein kinase. However, we did not detect induction of tyrosine phosphorylation of the epidermal growth factor receptor in S. typhimurium-infected cells. Treatment with the tyrosine protein kinase inhibitor genistein did not reduce S. typhimurium invasion into any of these cell lines. These results suggest that S. typhimurium invasion is independent of host cell epidermal growth factor receptor activation.
Evidence for lipopolysaccharide as the predominant proinflammatory mediator in supernatants of antibiotic-treated bacteria
Authors: Leeson M C , Fujihara Y , Morrison D C
Published: January 2020

Lipopolysaccharide (LPS), purified from gram-negative bacteria, is well known to induce proinflammatory responses in monocytes and macrophages, and release of LPS from the microbial surface has been suggested to be an important initiating event in the sepsis syndrome. However, numerous studies have documented that a variety of constituents present in the outer cell membrane of gram-negative bacteria have the capacity to activate cells of the immune system. Given that the majority of immunotherapeutic approaches designed to intervene in gram-negative sepsis have to date targeted the LPS molecule, it would be of value to assess the relative proinflammatory properties of LPS and other gram-negative structures. Experiments were therefore undertaken to assess stimulation of human monocytes by components released from Escherichia coli following bacteriolysis by the cell wall-active antibiotic ceftazidime. As assessed by both induction of procoagulant activity and release of tumor necrosis factor, bacterial culture supernatants contain significant proinflammatory activity. When culture supernatants are fractionated via either velocity sedimentation in sucrose gradients or isopycnic density gradient ultracentrifugation in cesium chloride, the predominant monocyte-stimulating activity is identified in LPS-containing fractions. Further, such activity can be readily abrogated by the addition of polymyxin B. These results provide support for the hypothesis that LPS may be responsible for the majority of the proinflammatory activity released from E. coli following bacteriolysis in vitro.
Inhibition of infection of macrophages with Ehrlichia risticii by cytochalasins, monodansylcadaverine, and taxol
Authors: Rikihisa Y , Zhang Y , Park J
Published: January 2020

The requirement of functions of clathrin, microfilaments, and microtubules in binding, internalization, proliferation, and spreading of Ehrlichia risticii in macrophages was studied. Monodansylcadaverine (MDC), which inhibits clustering and internalization of the ligand-receptor complexes into clathrin-coated vesicles; cytochalasin B or D, which depolymerizes microfilaments; and taxol, which binds and stabilizes polymerized microtubules, were found to prevent ehrlichial infection in murine peritoneal macrophages when they were present throughout the infection period. [35S]methionine-labeled ehrlichial binding to the macrophage was reduced by 0 to 22%; therefore, the binding was not the major point of inhibition. However, MDC, cytochalasin D, and taxol inhibited ehrlichial internalization into macrophages by 80, 58, and 32%, respectively. When MDC, cytochalasin B or D, or taxol was added immediately after internalization of E. risticii (3 h postinfection), ehrlichial replication in P388D1 cells was almost completely prevented. Also, all of these agents almost completely prevented ehrlichial spreading from P388D1 cells to THP-1 human monocytes. These agents were not found to be ehrlichiacidal when approximately 40%-infected P388D1 cells were treated for 2 days, although further intracellular proliferation was prevented. Furthermore, none of these compounds directly inhibited the metabolic activity of E. risticii, since 14CO2 production from L-[14C]glutamine by Percoll density gradient-purified host-cell-free E. risticii was not shown to be impaired. The action of taxol was probably due to impairment of the microtubule function since a microtubule-depolymerizing agent, colchicine, also inhibited intracellular proliferation of E. risticii. Neither reactive oxygen intermediates, nitric oxide, nor tumor necrosis factor alpha appeared to be involved in taxol-induced inhibition of E. risticii in macrophages. Thus, our findings indicate that ehrlichial internalization appears to take place by a mechanism that is more dependent on the functions of clathrin and less dependent on the functions of microfilaments or microtubules. Replication within macrophages and intercellular spreading appear to require clathrin, microfilaments, and microtubules. Consequently, alteration of these structures with inhibitors can result in complete prevention of infection.
Some structures and processes of human epithelial cells involved in uptake of enterohemorrhagic Escherichia coli O157:H7 strains
Authors: Oelschlaeger T A , Barrett T J , Kopecko D J
Published: January 2020

Several enterohemorrhagic Escherichia coli (EHEC) strains of serotype O157:H7 isolated from patients with hemorrhagic colitis, ischemic colitis, or hemolytic uremic syndrome were all found to be able to invade certain human epithelial cell lines in vitro. Their ability to gain entry into epithelial cells was compared with those of known invasive Shigella flexneri and Salmonella typhi strains and the noninvasive E. coli strain HB101 in invasion assays utilizing gentamicin to kill extracellular bacteria. All EHEC strains under investigation were efficiently internalized into T24 bladder and HCT-8 ileocecal cells. In striking contrast to shigellae, the same EHEC strains were not taken up into human embryonic intestinal INT407 cells or HEp-2 cells any more than the noninvasive E. coli strain HB101. The mechanism(s) of EHEC internalization was characterized by comparing the invasion efficiencies in the absence and presence of a variety of inhibitors acting on structures and processes of prokaryotic or eukaryotic cells. Also, wild-type, plasmid-containing EHEC strains were compared with their plasmid-cured isogenic derivative strains to determine if plasmid genes affect invasion ability. Plasmid-cured EHEC invaded as well as wild-type EHEC, indicating that invasion ability is chromosomally encoded. Inhibition of bacterial protein synthesis by simultaneous addition of bacteria and chloramphenicol to the monolayer blocked EHEC uptake dramatically, suggesting the presence of an invasion protein(s) with a short half-life. Studies utilizing inhibitors which act on eukaryotic cells demonstrated a strong dependence on microfilaments in the process of uptake of all EHEC strains into both T24 and HCT-8 cells. In general, depolymerization of microtubules as well as inhibition of receptor-mediated endocytosis reduced the efficiency of EHEC invasion of T24 cells, whereas interference with endosome acidification reduced EHEC entry into only HCT-8 cells. Taxol-induced stabilization of microtubules did not inhibit internalization into T24 cells or into the HCT-8 cell line. In marked contrast, the ability of S. typhi Ty2 to invade either cell line was inhibited only by depolymerization of microfilaments. In addition to the cell line specificity of EHEC invasion, not all EHEC strains displayed uniform behavior in the presence of inhibitors, suggesting the existence of variant uptake pathways in different strains. Most importantly, previous reports of the inability of EHEC to invade INT407 or HEp-2 cell lines support the currently held belief that EHEC strains are noninvasive.(ABSTRACT TRUNCATED AT 400 WORDS)
Subcloning and expression of the Brucella abortus L7/L12 ribosomal gene and T-lymphocyte recognition of the recombinant protein
Authors: Oliveira S C , Splitter G A
Published: January 2020

The Brucella abortus L7/L12 ribosomal gene was amplified by PCR and subcloned into the prokaryotic expression vector pMAL-c2. Escherichia coli DH5 alpha was transformed with the pMAL-L7/L12 construct, and gene expression was induced by IPTG (isopropyl-beta-D-thiogalactopyranoside). The resulting fusion protein was purified by affinity chromatography and confirmed by Western blot (immunoblot) analysis using an anti-maltose-binding protein antibody. Additionally, purified recombinant L7/L12 protein induced T-lymphocyte proliferation of B. abortus-primed bovine peripheral blood mononuclear cells. Phenotypic analysis of the proliferating cell population demonstrated an increase in the percentage of CD4+ T lymphocytes when peripheral blood mononuclear cells were cultured with recombinant L7/L12 compared with cells cultured in medium alone. Subcloning and expression of a B. abortus gene encoding a previously demonstrated immunodominant protein for bovine lymphocytes are important steps in selecting Brucella proteins that have potential as a component of a genetically engineered candidate vaccine.
Nucleotide sequence analysis of genes essential for capsular polysaccharide biosynthesis in Streptococcus pneumoniae type 19F
Authors: Guidolin A , Morona J K , Morona R , Hansman D , Paton J C
Published: January 2020

Previous studies have shown that the capsular polysaccharide synthesis (cps) locus of the type 19F Streptococcus pneumoniae strain SSZ was closely linked to a copy of the insertion sequence IS1202 (J.K. Morona, A. Guidolin, R. Morona, D. Hansman, and J.C. Paton, J. Bacteriol. 176:4437-4443, 1994). In the present study, we used plasmid insertion and rescue and inverse PCR to clone 6,322 bp of flanking DNA upstream of IS1202. Sequence analysis indicated that this region contains six complete open reading frames (ORFs) and one partial ORF that are arranged as a single transcriptional unit. Chromosomal disruption of any of these ORFs in a smooth-type 19F strain leads to a rough (unencapsulated) phenotype, indicating that this operon is essential for capsule production. The ORFs have therefore been designated cps19fA to cps19fG, where cps19fA is the first gene of the type 19F cps locus. Furthermore, many of the gene products from this incomplete operon exhibit strong similarities to proteins known to be involved in the production of capsular polysaccharide, exopolysaccharide, teichoic acid, enterobacterial common antigen, and lipopolysaccharide from numerous other bacterial species. This has allowed us to propose functions for many of the type 19F cps gene products. Southern hybridization studies reveal that cps19fA and cps19fB are conserved among all 12 pneumococcal serotypes tested, whereas genes downstream of cps19fB are conserved among some, but not all, of the serotypes tested.
Increase of gamma/delta T cells in hospital workers who are in close contact with tuberculosis patients
Authors: Ueta C , Tsuyuguchi I , Kawasumi H , Takashima T , Toba H , Kishimoto S
Published: January 2020

gamma/delta T cells are likely to participate in the immune response to tuberculous infection in humans. In this study, we carried out an investigation to characterize the responsiveness of gamma/delta T cells from tuberculous patients and healthy individuals to mycobacterial stimulation in vitro. Healthy subjects were assigned to the following two groups: those who had been exposed to tuberculosis (contacts) and those who had not been exposed (noncontacts). The percent gamma/delta T cells in fresh peripheral blood obtained from health care workers who were tuberculin skin test positive and who had constant contact with patients with active tuberculosis (healthy contacts) was significantly higher, whereas healthy noncontacts showed the normal range of gamma/delta T cells. Patients with active pulmonary tuberculosis also had low levels of gamma/delta T cells. HLA-DR antigen-bearing activated gamma/delta T cells were observed in higher percentages among healthy contacts than among healthy noncontacts or patients with pulmonary tuberculosis. In healthy contacts, gamma/delta T cells increased as a percentage of peripheral blood mononuclear cells after in vitro stimulation with purified protein derivative (PPD) tuberculin compared with the percentage of fresh peripheral blood mononuclear cells that they made up, whereas no such increase was observed in patients with tuberculosis or in healthy noncontacts. Phenotypic analysis of the gamma/delta T cells in healthy contacts, which increased in number in vitro in response to PPD, revealed the preferential outgrowth of CD4+ V gamma 2+ gamma/delta T cells. This expansion of gamma/delta T cells by PPD required accessory cells, and it was inhibited by the addition of an antibody against HLA-DR in culture. Proteolytic digestion of PPD showed that gamma/delta T cells increased in number in response to peptide, but not nonpeptide, components of PPD. These findings suggest that gamma/delta T cells, especially CD4+ V gamma 2+ gamma/delta T cells, may participate in the immune surveillance of tuberculous infections in humans.
Natural variation within the principal adhesion domain of the Plasmodium vivax duffy binding protein
Authors: Tsuboi T , Kappe S H , al-Yaman F , Prickett M D , Alpers M , Adams J H
Published: January 2020

The blood-stage development of malaria parasites is initiated by the invasion of merozoites into susceptible erythrocytes. Specific receptor-ligand interactions must occur for the merozoites to first attach to and then invade erythrocytes. Because the invasion process is essential for the parasite's survival and the merozoite adhesion molecules are exposed on the merozoite surface during invasion, these adhesion molecules are candidates for antibody-dependent malaria vaccines. The Duffy binding protein of Plasmodium vivax belongs to a family of erythrocyte-binding proteins that contain functionally conserved cysteine-rich regions. The amino cysteine-rich regions of these homologous erythrocyte-binding proteins were recently identified for P. vivax, Plasmodium knowlesi, and Plasmodium falciparum as the principal erythrocyte-binding domains (C. Chitnis and L. H. Miller, J. Exp. Med. 180:497-506, 1994, and B. K. L. Sim, C. E. Chitnis, K. Wasniowska, T. J. Hadley, and L. H. Miller, Science 264:1941-1944, 1994). We report that amino acids in this critical ligand domain of the P. vivax Duffy binding protein are hypervariable, but this variability is limited. Hypervariability of the erythrocyte-binding domain suggests that this domain is the target of an effective immune response, but conservation of amino acid substitutions indicates that functional constraints limit this variation. In addition, the amino cysteine-rich region and part of the hydrophilic region immediately following it were the site of repeated homologous recombinations as represented by tandem repeat sequence polymorphisms. Similar polymorphisms have been identified in the same region of the homologous genes of P. falciparum and P. knowlesi, suggesting that there is a common mechanism of recombination or gene conversion that occurs in these Plasmodium genes.