bluuebunny/crossref_metadata_2025_split huggingface dataset:
Listeria monocytogenes-Infected Phagocytes Can Initiate Central Nervous System Infection in Mice
Authors: Drevets Douglas A. , Jelinek Todd A. , Freitag Nancy E. 
Published: July 2002

ABSTRACTListeria monocytogenes-infected phagocytes are present in the bloodstream of experimentally infected mice, but whether they play a role in central nervous system (CNS) invasion is unclear. To test whether bacteria within infected leukocytes could establish CNS infection, experimentally infected mice were treated with gentamicin delivered by surgically implanted osmotic pumps. Bacterial inhibitory titers in serum and plasma ranged from 1:16 to 1:256, and essentially all viable bacteria in the bloodstream of treated mice were leukocyte associated. Nevertheless, CNS infection developed in gentamicin-treated animals infected intraperitoneally or by gastric lavage, suggesting that intracellular bacteria could be responsible for neuroinvasion. This was supported by data showing that 43.5% of bacteria found with blood leukocytes were intracellular and some colocalized with F-actin, indicating productive intracellular parasitism. Experiments using anL. monocytogenesstrain containing a chromosomalactA-gfpuv-plcBtranscriptional fusion showed that blood leukocytes were associated with intracellular and extracellularly bound green fluorescent protein-expressing (GFP+) bacteria. Treatment with gentamicin decreased the numbers of extracellularly bound GFP+bacteria significantly but did not affect the numbers of intracellular GFP+bacteria, suggesting that the latter were the result of intercellular spread of GFP+bacteria to leukocytes. These data demonstrate that infected leukocytes and the intracellularL. monocytogenesharbored within them play key roles in neuroinvasion. Moreover, they suggest that phagocytes recruited to infected organs such as the liver or spleen are themselves parasitized by intercellular spread ofL. monocytogenesand then reenter the bloodstream and contribute to the systemic dissemination of bacteria.
Salivary Histatin 5 Is an Inhibitor of Both Host and Bacterial Enzymes Implicated in Periodontal Disease
Authors: Gusman Heloisa , Travis James , Helmerhorst Eva J. , Potempa Jan , Troxler Robert F. , Oppenheim Frank G. 
Published: July 2002

ABSTRACT

One of the salient features of periodontitis and gingivitis is the increase in the levels of bacterial and host-derived proteolytic enzymes in oral inflammatory exudates. This study evaluated the potential of histatin 5, a 24-residue histidine-rich salivary antimicrobial protein, to inhibit these enzymes. Using biotinylated gelatin as a substrate, histatin 5 was found to inhibit the activity of the host matrix metalloproteinases MMP-2 and MMP-9 with 50% inhibitory concentrations (IC
50
s) of 0.57 and 0.25 μM, respectively. To localize the domain responsible for this inhibition, three peptides containing different regions of histatin 5 were synthesized and tested as inhibitors of MMP-9. Peptides comprising residues 1 to 14 and residues 4 to 15 of histatin 5 showed much lower inhibitory activities (IC
50
, 21.4 and 20.5 μM, respectively), while a peptide comprising residues 9 to 22 showed identical activity to histatin 5 against MMP-9. These results point to a functional domain localized in the C-terminal part of histatin 5. To evaluate the effect of histatin 5 on bacterial proteases, a detailed characterization of histatin 5 inhibition of gingipains from
Porphyromonas gingivalis
was carried out using purified Arg- and Lys-specific enzymes. Kinetic analysis of the inhibition of the Arg-gingipain revealed that histatin 5 is a competitive inhibitor, affecting only the

K
m

with a

K
i

of 15 μM. In contrast, inhibition of Lys-gingipain affected both the

K
m

and
V
max
, suggesting that both competitive and noncompetitive competitive processes underlie this inhibition. The inhibitory activity of histatin 5 against host and bacterial proteases at physiological concentrations points to a new potential biological function of histatin in the oral cavity.
Immunomodulatory Role of Interleukin-10 in Visceral Leishmaniasis: Defective Activation of Protein Kinase C-Mediated Signal Transduction Events
Authors: Bhattacharyya Sandip , Ghosh Sanjukta , Jhonson Patti L. , Bhattacharya Syamal K. , Majumdar Subrata 
Published: July 2002

ABSTRACTLeishmania donovani, an intracellular protozoan parasite, challenges host defense mechanisms by impairing the signal transduction of macrophages. In this study we investigated whether interleukin-10 (IL-10)-mediated alteration of signaling events in a murine model of visceral leishmaniasis is associated with macrophage deactivation. Primary in vitro cultures of macrophages infected with leishmanial parasites markedly elevated the endogenous release of IL-10. Treatment with eitherL. donovanior recombinant IL-10 (rIL-10) inhibited both the activity and expression of the Ca2+-dependent protein kinase C (PKC) isoform. However, preincubation with neutralizing anti-IL-10 monoclonal antibody (MAb) restored the PKC activity in the parasitized macrophage. Furthermore, we observed that coincubation of macrophages with rIL-10 andL. donovaniincreased the intracellular parasite burden, which was abrogated by anti-IL-10 MAb. Consistent with these observations, generation of superoxide (O2−) and nitric oxide and the release of murine tumor necrosis factor-α were attenuated in response toL. donovanior rIL-10 treatment. On the other hand, preincubation of the infected macrophages with neutralizing anti-IL-10 MAb significantly blocked the inhibition of nitric oxide and murine tumor necrosis factor-α release by the infected macrophages. These findings imply that infection withL. donovaniinduces endogenous secretion of murine IL-10, which in turn facilitates the intracellular survival of the protozoan and orchestrates several immunomodulatory roles via selective impairment of PKC-mediated signal transduction.
Epitope Mapping oftrans-Sialidase fromTrypanosoma cruziReveals the Presence of Several Cross-Reactive Determinants
Authors: Pitcovsky Tamara A. , Mucci Juan , Alvarez Paula , Leguizamón M. Susana , Burrone Oscar , Alzari Pedro M. , Campetella Oscar 
Published: July 2002

ABSTRACTTrypanosoma cruzi, the agent of Chagas' disease, expressestrans-sialidase, a unique enzyme activity that enables the parasite to invade host cells by transferring sialyl residues from host glyconjugates to the parasite's surface acceptor molecules. The enzyme is also shed into the surrounding environment, causing apoptosis in cells from the immune system. During infections, an antibody response against the catalytic region of thetrans-sialidase that is coincident with the control of the parasitemia and survival of the host is observed. This low-titer humoral response is characterized by its persistence for many years in benznidazole-treated patients. Here we analyzed the antigenic structure of the molecule by phage-displayed peptide combinatorial libraries and SPOT synthesis. Several epitopes were defined and located on the three-dimensional model of the enzyme. Unexpectedly, cross-reaction was found among several epitopes distributed in different locations displaying nonconsensus sequences. This finding was confirmed by the reactivity of three monoclonal antibodies able to recognize non-sequence-related peptides that together constitute the surface surrounding the catalytic site of the enzyme. The presence of cross-reacting epitopes within a single molecule suggests a mechanism developed to avoid a strong humoral response by displaying an undefined target to the immune system.
Membrane-Associated Proteins of a Lipopolysaccharide-Deficient Mutant ofNeisseria meningitidisActivate the Inflammatory Response through Toll-Like Receptor 2
Authors: Ingalls Robin R. , Lien Egil , Golenbock Douglas T. 
Published: July 2002

ABSTRACTThe recent isolation of a lipopolysaccharide (LPS)-deficient mutant ofNeisseria meningitidishas allowed us to explore the roles of other gram-negative cell wall components in the host response to infection. The experiments in this study were designed to examine the ability of this mutant strain to activate cells. Although it was clearly less potent than the parental strain, we found the LPS-deficient mutant to be a capable inducer of the inflammatory response in monocytic cells, inducing a response similar to that seen withStaphylococcus aureus. Cellular activation by the LPS mutant was related to expression of CD14, a high-affinity receptor for LPS and other microbial products, as well as Toll-like receptor 2, a member of the Toll family of receptors recently implicated in host responses to gram-positive bacteria. In contrast to the parental strain, the synthetic LPS antagonist E5564 did not inhibit the LPS-deficient mutant. We conclude that even in the absence of LPS, the gram-negative cell wall remains a potent inflammatory stimulant, utilizing signaling pathways independent of those involved in LPS signaling.
Gamma Interferon-Producing CD4+T Lymphocytes in the Lung Correlate with Resistance to Infection withMycobacterium tuberculosis
Authors: Chackerian Alissa A. , Perera Thushara V. , Behar Samuel M. 
Published: July 2002

ABSTRACTThe human immune system efficiently limits the replication ofMycobacterium tuberculosisin most infected individuals. Only 5 to 10% of infected people develop clinical tuberculosis, a sign of the inability of the immune system to control the infection. We have studied the C3H/HeJ (C3H) and C57BL/6 (B6) inbred mouse strains, which differ in their susceptibility to tuberculosis, in order to ascertain the immunological determinants of a successful immune response againstM. tuberculosisand to establish a system to identify genes that influence susceptibility to tuberculosis. We found that the resistant B6 mice were able to control infection in both the lung and spleen, while susceptible C3H mice were incapable of limiting bacteria growth, especially in the lung, and succumbed to infection within 4 weeks. We determined that the susceptibility of C3H mice was independent of the Toll-like receptor 4 (tlr4) genetic locus and allelic major histocompatibility complex differences. Although the splenic immune responses were similar in the two mouse strains, the local immune responses in the lungs of the infected mice differed greatly. The pulmonary immune response in resistant B6 mice was characterized by an early influx of both CD4+and CD8+lymphocytes that produced gamma interferon (IFN-γ). In contrast, the immune response of C3H mice in the lung was characterized by a delayed and decreased influx of lymphocytes, which produced little IFN-γ. These results suggest an important role for the early appearance of IFN-γ-producing lymphocytes in the lung in resistance to infection withM. tuberculosis.
Intracellular
Actinobacillus actinomycetemcomitans
and
Porphyromonas gingivalis
in Buccal Epithelial Cells Collected from Human Subjects
Authors: Rudney Joel D. , Chen Ruoqiong , Sedgewick Gerald J. 
Published: July 2002

ABSTRACT

The mouth may provide an accessible model for studying bacterial interactions with human cells in vivo. Using fluorescent in situ hybridization and laser scanning confocal microscopy, we found that human buccal epithelial cells from 23 of 24 subjects were infected with intracellular bacteria, including the periodontal pathogens
Actinobacillus actinomycetemcomitans
and
Porphyromonas gingivalis
, as well as other species which have yet to be identified. Buccal cell invasion may allow fastidious anaerobes to establish themselves in aerobic sites that otherwise present an unfavorable environment. Exfoliated buccal epithelial cells might provide a protected route for bacterial transmission between different oral sites within and between hosts.
C-Terminal Invariable Domain of VlsE Is Immunodominant but Its Antigenicity Is Scarcely Conserved among Strains of Lyme Disease Spirochetes
Authors: Liang Fang Ting , Bowers Lisa C. , Philipp Mario T. 
Published: July 2002

ABSTRACTVlsE, the variable surface antigen ofBorrelia burgdorferi, contains two invariable domains located at the amino and carboxyl terminal ends, respectively, and a central variable domain. In this study, both immunogenicity and antigenic conservation of the C-terminal invariable domain were assessed. Mouse antiserum to a 51-mer synthetic peptide (Ct) which reproduced the entire sequence of the C-terminal invariable domain of VlsE fromB. burgdorferistrain B31 was reacted on immunoblots with whole-cell lysates extracted from spirochetes of 12 strains from theB. burgdorferisensu lato species complex. The antiserum recognized only VlsE from strain B31, indicating that epitopes of this domain differed among these strains. When Ct was used as enzyme-linked immunosorbent assay (ELISA) antigen, all of the seven monkeys and six mice that were infected with B31 spirochetes produced a strong antibody response to this peptide, indicating that the C-terminal invariable domain is immunodominant. None of 12 monkeys and only 11 of 26 mice that were infected with strains other than B31 produced a detectable anti-Ct response, indicating a limited antigenic conservation of this domain among these strains. Twenty-six of 33 dogs that were experimentally infected by tick inoculation were positive by the Ct ELISA, while only 5 of 18 serum samples from dogs clinically diagnosed with Lyme disease contained detectable anti-Ct antibody. Fifty-seven of 64 serum specimens that were collected from American patients with Lyme disease were positive by the Ct ELISA, while only 12 of 21 European samples contained detectable anti-Ct antibody. In contrast, antibody to the more conserved invariable region IR6of VlsE was present in all of these dog and human serum samples.
Specificity of the Protective Antibody Response to Apical Membrane Antigen 1
Authors: Hodder Anthony N. , Crewther Pauline E. , Anders Robin F. 
Published: July 2002

ABSTRACT

Apical membrane antigen 1 (AMA1) is considered one of the leading candidates for inclusion in a vaccine against blood stages of
Plasmodium falciparum
. Although the
ama1
gene is relatively conserved compared to those for some other potential vaccine components, numerous point mutations have resulted in amino acid substitutions at many sites in the polypeptide. The polymorphisms in AMA1 have been attributed to the diversifying selection pressure of the protective immune responses. It was therefore of interest to investigate the impact of sequence diversity in
P. falciparum
AMA1 on the ability of anti-AMA1 antibodies to inhibit the invasion of erythrocytes in vitro by
P. falciparum
merozoites. For these studies, we used antibodies to recombinant
P. falciparum
3D7 AMA1 ectodomain, which was prepared for testing in early clinical trials. Antibodies were raised in rabbits to the antigen formulated in Montanide ISA720, and human antibodies to AMA1 were isolated by affinity purification from the plasma of adults living in regions of Papua New Guinea where malaria is endemic. Both rabbit and human anti-AMA1 antibodies were found to be strongly inhibitory to the invasion of erythrocytes by merozoites from both the homologous and two heterologous lines of
P. falciparum
. The inhibitory antibodies targeted both conserved and strain-specific epitopes within the ectodomain of AMA1; however, it appears that the majority of these antibodies reacted with strain-specific epitopes in domain I, the N-terminal disulfide-bonded domain, which is the most polymorphic region of AMA1.
Amebic Infection in the Human Colon Induces Cyclooxygenase-2
Authors: Stenson William F. , Zhang Zhi , Riehl Terrence , Stanley Samuel L. 
Published: July 2002

ABSTRACTWe sought to determine if infection of the colon withEntamoeba histolyticainduces the expression of cyclooxygenase-2 and, if it does, to determine the contribution of prostaglandins produced through cyclooxygenase-2 to the host response to amebic infection. Human fetal intestinal xenografts were implanted subcutaneously in mice with severe combined immunodeficiency and allowed to grow; the xenografts were then infected withE. histolyticatrophozoites. Infection withE. histolyticaresulted in the expression of cyclooxygenase-2 in epithelial cells and lamina propria macrophages. Infection withE. histolyticaincreased prostaglandin E2(PGE2) levels 10-fold in the xenografts and resulted in neutrophil infiltration, as manifested by an 18-fold increase in myeloperoxidase activity. Amebic infection also induced an 18-fold increase in interleukin 8 (IL-8) production and a >100-fold increase in epithelial permeability. Treatment of the host mouse with indomethacin, an inhibitor of cyclooxygenase-1 and cyclooxygenase-2, or with NS-398, a selective inhibitor of cyclooxygenase-2, resulted in (i) decreased PGE2levels, (ii) a decrease in neutrophil infiltration, (iii) a decrease in IL-8 production, and (iv) a decrease in the enhanced epithelial permeability seen with amebic infection. These results indicate that amebic infection in the colon induces the expression of cyclooxygenase-2 in epithelial cells and macrophages. Moreover, prostaglandins produced through cyclooxygenase-2 participate in the mediation of the neutrophil response to infection and enhance epithelial permeability.
Tumor Necrosis Factor-Dependent Adhesions as a Major Protective Mechanism Early in Septic Peritonitis in Mice
Authors: Echtenacher Bernd , Weigl Karin , Lehn Norbert , Männel Daniela N. 
Published: July 2002

ABSTRACTThe occurrence of peritoneal adhesions in surgical patients is positively correlated with tumor necrosis factor (TNF) levels. In a model of septic peritonitis—cecal ligation and puncture—TNF neutralization prevented formation of peritoneal adhesions and increased mortality, most likely because localization of the septic focus was prevented. To discriminate between the coagulation-independent protective TNF effect and a potential protective procoagulant TNF effect, formation of peritoneal adhesions after CLP was inhibited with heparin, hirudin, or urokinase. Each treatment increased mortality and increased the number of bacteria in the peritoneal lavage fluid, kidney, and liver to various degrees. Under these experimental conditions, antibiotics prevented death. In coagulation-compromised mice, lethality was further enhanced by additional TNF neutralization. These findings demonstrate that peritoneal adhesions early in septic peritonitis are an important mechanism of innate immunity that prevents increased spread of bacteria and reduces mortality.
Differential Induction of Gamma Interferon inLegionella pneumophila- Infected Macrophages from BALB/c and A/J Mice
Authors: Salins Sheldon , Newton Catherine , Widen Ray , Klein Thomas W. , Friedman Herman 
Published: July 2002

ABSTRACTGamma interferon (IFN-γ), a pleiotropic cytokine, is now known to be produced by macrophages as well as by NK cells, γδ cells, and activated T cells. The autocrine biological functions of IFN-γ on the macrophage include the upregulation of major histocompatibility complex MHC class II and the activation to an antiviral state. In this study, the production of IFN-γ by macrophages was demonstrated to correspond to antibacterial activity.Legionella pneumophilareplicates intracellularly in thioglycolate (TG)-elicited macrophages (TG-macrophages) from A/J mice, while TG-macrophages from BALB/c mice restrict bacterial growth after an initial period of growth. BALB/c TG-macrophages were shown to express IFN-γ mRNA at 24 and 28 h, which corresponded to the initiation of anti-L. pneumophilaactivity. Moreover, IFN-γneutralization by antibody treatment of the cultures resulted in increasedL. pneumophilagrowth in the macrophages. In contrast, no IFN-γ mRNA was expressed in TG-macrophages from A/J mice, whereL. pneumophilagrew unrestricted. As would be expected, IFN-γ treatment decreased bacterial growth. An IFN-γ-mediated antibacterial activity was, however, inducible in A/J macrophages by the addition of interleukin-12 followingL. pneumophilainfection. Thus, autocrine IFN-γ is involved in anti-L. pneumophilaactivity associated with different growth patterns and appears to be important during intracellular infection.
Identification of
Legionella pneumophila rcp
, a
pagP
-Like Gene That Confers Resistance to Cationic Antimicrobial Peptides and Promotes Intracellular Infection
Authors: Robey Marianne , O'Connell William , Cianciotto Nicholas P. 
Published: July 2002

ABSTRACT

In the course of characterizing a locus involved in heme utilization, we identified a
Legionella pneumophila
gene predicted to encode a protein with homology to the product of the
Salmonella enterica
serovar Typhimurium
pagP
gene. In
Salmonella, pagP
increases resistance to the bactericidal effects of cationic antimicrobial peptides (CAMPs). Mutants with insertions in the
L. pneumophila pagP
-like gene were generated and showed decreased resistance to different structural classes of CAMPs compared to the wild type; hence, this gene was designated
rcp
for resistance to cationic antimicrobial peptides. Furthermore,
Legionella
CAMP resistance was induced by growth in low-magnesium medium. To determine whether
rcp
had any role in intracellular survival, mutants were tested in the two most relevant host cells for Legionnaires' disease, i.e., amoebae and macrophages. These mutants exhibited a 1,000-fold-decreased recovery during a
Hartmannella vermiformis
coculture. Complementation of the infectivity defect could be achieved by introduction of a plasmid containing the intact
rcp
gene. Mutations in
rcp
consistently reduced both the numbers of bacteria recovered during intracellular infection and their cytopathic capacity for U937 macrophages. The
rcp
mutant was also more defective for lung colonization of A/J mice. Growth of
rcp
mutants in buffered yeast extract broth was identical to that of the wild type, indicating that the observed differences in numbers of bacteria recovered from host cells were not due to a generalized growth defect. However, in low-Mg
2+
medium, the
rcp
mutant was impaired in stationary-phase survival. This is the first demonstration of a
pagP
-like gene, involved in resistance to CAMPs, being required for intracellular infection and virulence.
Expression of aMycobacterium tuberculosisArabinomannan Antigen In Vitro and In Vivo
Authors: Schwebach J. Reid , Casadevall Arturo , Schneerson Rachel , Dai Zhongdong , Wang Xiaojuan , Robbins John B. , Glatman-Freedman Aharona 
Published: July 2002

ABSTRACTThe outermost layer ofMycobacterium tuberculosiscontains two major polysaccharides, arabinomannan (AM) and glucan (GC). We studied the in vitro and in vivo expression of anM. tuberculosisAM antigen using monoclonal antibody (MAb) 9d8 (2a), an isotype-switched variant of the immunoglobulin G3 (IgG3) MAb 9d8. MAb 9d8 had been previously shown to bindM. tuberculosisAM and theM. tuberculosissurface. Our in vitro experiments showed that MAb 9d8(2a) bound strongly to whole-cellM. tuberculosisErdman but not to the CDC 1551 strain grown in medium for an extended period. However, AM antigen was detected in the culture supernatant of both strains, and its concentration increased in a time-dependent manner. The detection of AM antigen from both strains was decreased in the presence of Tween 80. In mice infected withM. tuberculosisErdman, AM antigen accumulated in organ homogenates concomitant to an increase in bacterial organ burden and an increase in IgG and IgM titer to AM. These results (i) indicate that the surface expression of AM during in vitro growth changes with culture age, is strain dependent, and is affected by the presence of Tween 80 in the culture media; (ii) show that AM is produced by bacteria growth in vivo; and (iii) demonstrate that the amount of in vivo-detected AM can be dependent on the number of bacteria in the infected organ.