bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of the Alternative Complement Pathway by Fungal Melanins
Authors: Rosas Á. L. , MacGill R. S. , Nosanchuk J. D. , Kozel T. R. , Casadevall A. 
Published: July 2002

ABSTRACTMelanins are complex biological pigments formed by the oxidative polymerization of phenolic and/or indolic compounds. These pigments have been implicated in the pathogenesis of some microbial infections, malignancies, degenerative disorders, and autoimmune diseases. Recent studies have demonstrated that melanins have antigenic and anti-inflammatory properties. These findings led us to further explore the interaction of melanins with the immune system. Melanin particles (“ghosts”) were isolated from in vitro-melanizedCryptococcus neoformanscells andAspergillus nigerconidia and then incubated in normal human serum containing125I-labeled complement C3. The results demonstrated deposition of C3 fragments onto the melanin ghosts as early as 1 min after incubation, with maximum deposition occurring after 12 min forC. neoformans-derived melanin ghosts and after 25 min forA. niger-derived melanin ghosts. The blocking of classical pathway activation did not affect the kinetics or total deposition of C3 onto the melanin ghosts, indicating that melanins activate complement through the alternative pathway. Immunofluorescence analysis of lungs from BALB/c mice injected intratracheally withC. neoformans-derived melanin ghosts demonstrated deposition of C3 fragments onto the ghosts. Small granulomas were also observed surrounding the ghosts. However, melanization of theC. neoformanscell wall did not alter the kinetics or total deposition of C3 fragments onto the fungal cells. The finding that melanin surfaces can activate the complement system suggests a potential mechanism for the pathogenesis of some degenerative and/or autoimmune processes that involve melanized cells as well as another potential role for melanin in the virulence of melanin-producing microorganisms.
Sodium Bicarbonate Enhances the Severity of Infection in Neutropenic Mice Orally Inoculated withListeria monocytogenesEGD
Authors: Czuprynski C. J. , Faith N. G. 
Published: July 2002

ABSTRACTEpidemiological studies have suggested an association between antacid therapy and development of listeriosis in humans. In this study we used a neutropenic mouse model to demonstrate that oral administration of sodium bicarbonate shortly before intragastric (i.g.) inoculation withListeria monocytogenesEGD (serotype 1/2a) significantly increased the severity of the resulting systemic infection. An explanation for this observation is provided by evidence thatL. monocytogenesEGD is rapidly inactivated in synthetic gastric fluid at pH below 5. A second strain ofL. monocytogenes(CM [serotype 1/2b]) exhibited little ability to cause systemic infection following i.g. inoculation and was not significantly enhanced by administration of sodium bicarbonate. Strain CM was readily inactivated in synthetic gastric fluid even at pH 7. These data suggest that gastric acidity and enzymes provide some innate defense against gastrointestinal listeriosis in neutropenic mice.
Human C-Reactive Protein Is Protective against FatalSalmonella entericaSerovar Typhimurium Infection in Transgenic Mice
Authors: Szalai Alexander J. , VanCott J. L. , McGhee Jerry R. , Volanakis John E. , Benjamin William H. 
Published: July 2002

ABSTRACTC-reactive protein (CRP) is an acute-phase protein with a well-known association with infection and other inflammatory conditions. We have shown that expression of human CRP by CRP transgenic (CRPtg) mice is protective against lethal infection byStreptococcus pneumoniae, an effect likely mediated by CRP's ability to bind to this gram-positive pathogen. In the present study we tested whether CRPtg mice are resistant to infection withSalmonella entericaserovar Typhimurium, a gram-negative pathogen that causes the murine equivalent of typhoid fever. CRPtg mice experimentally infected with a virulent Typhimurium strain lived longer and had significantly lower mortality than their non-tg littermates. The greater resistance of CRPtg mice could be attributed to significantly increased early (0 to 4 h) blood clearance of salmonellae and significantly decreased numbers of bacteria in the liver and spleen on day 7 postinfection. In addition, 14 days after infection with an avirulentSalmonellastrain, the serum titer of anti-Salmonellaimmunoglobulin G antibodies was higher in CRPtg than non-tg mice. This study provides unequivocal evidence that CRP plays an important role in vivo in host defense against salmonellae during the early stages of infection. In addition, as the beneficial effect of CRP includes enhancement of the host's humoral immune response, CRP may also contribute indirectly to host defense during later stages of infection.
Pet Toxin from Enteroaggregative
Escherichia coli
Produces Cellular Damage Associated with Fodrin Disruption
Authors: Villaseca Jorge M. , Navarro-García Fernando , Mendoza-Hernández Guillermo , Nataro James P. , Cravioto Alejandro , Eslava Carlos 
Published: July 2002

ABSTRACT

Pet toxin is a serine protease from enteroaggregative
Escherichia coli
which has been described as causing enterotoxic and cytotoxic effects. In this paper we show that Pet produces spectrin and fodrin (nonerythroid spectrin) disruption. Using purified erythrocyte membranes treated with Pet toxin, we observed degradation of α- and β-spectrin chains; this effect was dose and time dependent, and a 120-kDa protein fraction was observed as a breakdown product. Spectrin degradation and production of the 120-kDa subproduct were confirmed using specific antibodies against the α- and β-spectrin chains. The same degradation effect was observed in α-fodrin from epithelial HEp-2 cells, both in purified cell membranes and in cultured cells which had been held in suspension for 36 h; these effects were confirmed using antifodrin rabbit antibodies. The spectrin and fodrin degradation caused by Pet is related to the Pet serine protease motif. Fluorescence and light microscopy of HEp-2 Pet-treated cells showed morphological alterations, which were associated with irregular distribution of fodrin in situ. Spectrin and fodrin degradation by Pet toxin were inhibited by anti-Pet antibodies and by phenylmethylsulfonyl fluoride. A site-directed Pet mutant, which had been shown to abolish the enterotoxic and cytotoxic effects of Pet, was unable to degrade spectrin in erythrocyte membranes or purified spectrin or fodrin in epithelial cell assays. This is a new system of cellular damage identified in bacterial toxins which includes the internalization of the protease, induction of some unknown intermediate signaling steps, and finally the fodrin degradation to destroy the cell.
Hemin-Binding Surface Protein from
Bartonella quintana
Authors: Carroll James A. , Coleman Sherry A. , Smitherman Laura S. , Minnick Michael F. 
Published: July 2002

ABSTRACT

Bartonella quintana
, the agent of trench fever and a cause of endocarditis and bacillary angiomatosis in humans, has the highest reported in vitro hemin requirement for any bacterium. We determined that eight membrane-associated proteins from
B. quintana
bind hemin and that a ∼25-kDa protein (HbpA) was the dominant hemin-binding protein. Like many outer membrane proteins, HbpA partitions to the detergent phase of a Triton X-114 extract of the cell and is heat modifiable, displaying an apparent molecular mass shift from approximately 25 to 30 kDa when solubilized at 100°C. Immunoblots of purified outer and inner membranes and immunoelectron microscopy with whole cells show that HbpA is strictly located in the outer membrane and surface exposed, respectively. The N-terminal sequence of mature HbpA was determined and used to clone the HbpA-encoding gene (
hbpA
) from a lambda genomic library. The
hbpA
gene is 816 bp in length, encoding a predicted immature protein of approximately 29.3 kDa and a mature protein of 27.1 kDa. A Fur box homolog with 53% identity to the
Escherichia coli
Fur consensus is located upstream of
hbpA
and may be involved in regulating expression. BLAST searches indicate that the closest homologs to HbpA include the
Bartonella henselae
phage-associated membrane protein, Pap31 (58.4% identity), and the OMP31 porin from
Brucella melitensis
(31.7% identity). High-stringency Southern blots indicate that all five pathogenic
Bartonella
spp. possess
hbpA
homologs. Recombinant HbpA can bind hemin in vitro; however, it does not confer a hemin-binding phenotype upon
E. coli
. Intact
B. quintana
treated with purified anti-HbpA Fab fragments show a significant (
P
< 0.004) dose-dependent decrease in hemin binding relative to controls, suggesting that HbpA plays an active role in hemin acquisition and therefore pathogenesis. HbpA is the first potential virulence determinant characterized from
B. quintana
.
Emerging Family of Proline-Specific Peptidases of
Porphyromonas gingivalis
: Purification and Characterization of Serine Dipeptidyl Peptidase, a Structural and Functional Homologue of Mammalian Prolyl Dipeptidyl Peptidase IV
Authors: Banbula Agnieszka , Bugno Marcin , Goldstein Jason , Yen Jane , Nelson Daniel , Travis James , Potempa Jan 
Published: July 2002

ABSTRACT

Porphyromonas gingivalis
is an asaccharolytic and anaerobic bacterium that possesses a complex proteolytic system which is essential for its growth and evasion of host defense mechanisms. In this report, we show the purification and characterization of prolyl dipeptidyl peptidase IV (DPPIV) produced by this organism. The enzyme was purified to homogeneity, and its enzymatic activity and biochemical properties were investigated.
P. gingivalis
DPPIV, like its human counterpart, is able to cleave the N terminus of synthetic oligopeptides with sequences analogous to those of interleukins 1β and 2. Additionally, this protease hydrolyzes biologically active peptides including substance P, fibrin inhibitory peptide, and β-casomorphin. Southern blot analysis of genomic DNA isolated from several
P. gingivalis
strains reveal that a single copy of the DPPIV gene was present in all strains tested.
Comparable Endotoxic Properties of Lipopolysaccharides Are Manifest in Diverse Clinical Isolates of Gram-Negative Bacteria
Authors: Luchi Michael , Morrison David C. 
Published: July 2002

ABSTRACTIn general there is a poor correlation between serum lipopolysaccharide (LPS; the biologically active constituent of endotoxin) levels and mortality in septic patients. The objective of this study was to determine if chemical, structural, or biological differences among LPS from different clinical isolates of gram-negative bacteria might explain this discrepancy. LPS preparations were made using the hot phenol-water extraction method from eight clinical isolates of gram-negative bacteria. As a percentage of the total weight of the LPS, the phosphate content ranged from 3.0 to 13.8% (average, 6.7 ± 3.6%), and the 2-keto-3-deoxyoctonate content ranged from 1.9 to 27.4% (average, 8.9 ± 8.5%). These values were not dissimilar to those obtained for a reference endotoxin. In a standard measure of LPS activity, theLimulusamoebocyte lysate assay, there was approximately a twofold difference between the least and most active preparations. The two preparations with the greatest difference in their ability to elicit the secretion of tumor necrosis factor alpha from a mouse peritoneal macrophage cell line were similar in lethality when administered to mice sensitized to the effects of LPS byd(+)-galactosamine. These relatively minor differences in LPS activity seem unlikely to explain the generally observed discrepancy between serum endotoxin levels and mortality in patients with gram-negative sepsis.
Survival of Group BStreptococcusType III in Mononuclear Phagocytes: Differential Regulation of Bacterial Killing in Cord Macrophages by Human Recombinant Gamma Interferon and Granulocyte-Macrophage Colony-Stimulating Factor
Authors: Maródi László , Káposzta Rita , Nemes Éva 
Published: July 2002

ABSTRACTPhagocytic and killing capacities of resident and cytokine-activated human macrophages against group BStreptococcus(GBS) type III were studied. Evidence is presented that monocyte-derived macrophages from cord and adults ingest serum-opsonized GBS but that killing of bacteria was negligible in resident cells. Treatment of adult macrophages with recombinant human gamma interferon (rhIFN-γ; 100 U/ml) or recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF; 200 U/ml) resulted in significant increases of killing of GBS (P< 0.01 for each). The killing capacity of cord macrophages treated with rhGM-CSF was also enhanced compared to that of untreated cells (P< 0.01). However, treatment with rhIFN-γ resulted in only a moderate increase in the capacity of cord macrophages to kill GBS (P> 0.1). These results mirrored the effect of rhIFN-γ on candidacidal capacities of cord and adult macrophages, reported earlier from our laboratory. These data indicate differential modulation of neonatal macrophages by rhGM-CSF and rhIFN-γ. We suggest that administration of rhGM-CSF to neonates with invasive GBS disease may enhance host resistance to these bacteria.
Mucosal Immune Responses to Meningococcal Group C Conjugate and Group A and C Polysaccharide Vaccines in Adolescents
Authors: Zhang Q. , Choo S. , Everard J. , Jennings R. , Finn A. 
Published: July 2002

ABSTRACTPrevious studies in children have shown thatHaemophilus influenzaetype b (Hib) polysaccharide conjugate vaccines can reduce nasopharyngeal carriage ofH. influenzaeand provide herd immunity and suggest that this effect is mediated through mucosal antibodies. As this phenomenon may operate in other invasive bacterial infections which are propagated by nasopharyngeal carriage, mucosal antibody responses to meningococcal C conjugate and A/C polysaccharide vaccines were investigated. A total of 106 school children aged 11 to 17 years were randomized to receive a single dose of either conjugate or polysaccharide vaccine in an observer-blind study. Before and at 1, 6, and 12 months after immunization, samples of unstimulated saliva were collected and assayed by enzyme-linked immunosorbent assay for group C polysaccharide-specific immunoglobulin A (IgA), IgA1, IgA2 and secretory component, IgG antibodies, and total IgG and IgA. A subset of serum samples were also assayed for specific IgA and IgG antibodies. The concentrations of specific IgA and IgG in saliva were expressed both as nanograms per milliliter and as nanograms per microgram of total IgA or IgG. One month after immunization, significant increases in antibody titers (both IgA and IgG) were observed in saliva in both groups. There were significant subsequent falls in antibody titers by 6 months. Anti-meningococcal C-specific secretory component and IgA antibody titers were closely correlated (r= 0.85,P< 0.001), but there was no significant correlation between salivary and serum IgA titers, suggesting that IgA antibodies are locally produced. Significant correlation was found between salivary and serum IgG titers (r= 0.52,P< 0.01), suggesting that salivary IgG may be serum derived. Compared with polysaccharide vaccine, the conjugate vaccine induced significantly higher salivary IgG responses (P< 0.05), although there were no significant differences between salivary IgA responses to the two vaccines. The conjugate vaccine induced greater salivary IgG responses than a polysaccharide vaccine. Both vaccines induced significant salivary IgA antibodies. Further studies are needed to establish the functional significance of these mucosal responses.
Mucosal and Systemic Immune Responses to Chimeric Fimbriae Expressed bySalmonella entericaSerovar Typhimurium Vaccine Strains
Authors: Chen Huaiqing , Schifferli Dieter M. 
Published: July 2002

ABSTRACTRecombinant live oral vaccines expressing pathogen-derived antigens offer a unique set of attractive properties. Among these are the simplicity of administration, the capacity to induce mucosal and systemic immunity, and the advantage of permitting genetic manipulation for optimal antigen presentation. In this study, the benefit of having a heterologous antigen expressed on the surface of a live vector rather than intracellularly was evaluated. Accordingly, the immune response of mice immunized with aSalmonella entericaserovar Typhimurium vaccine strain expressing theEscherichia coli987P fimbrial antigen on its surface (Fas+) was compared with the expression in the periplasmic compartment (Fas−). Orally immunized BALB/c mice showed that 987P fimbriatedSalmonellaserovar Typhimurium CS3263 (aroA asd) with pCS151 (fas+asd+) elicited a significantly higher level of 987P-specific systemic immunoglobulin G (IgG) and mucosal IgA than serovar Typhimurium CS3263 with pCS152 (fasDmutant,asd+) expressing 987P periplasmic antigen. Further studies were aimed at determining whether the 987P fimbriae expressed by serovar Typhimurium χ4550 (cya crp asd) could be used as carriers of foreign epitopes. For this, the vaccine strain was genetically engineered to express chimeric fimbriae carrying the transmissible gastroenteritis virus (TGEV) C (379-388) and A (521-531) epitopes of the spike protein inserted into the 987P major fimbrial subunit FasA. BALB/c mice administered orally serovar Typhimurium χ4550 expressing the chimeric fimbriae from thetetpromoter in pCS154 (fas+asd+) produced systemic antibodies against both fimbria and the TGEV C epitope but not against the TGEV A epitope. To improve the immunogenicity of the chimeric fimbriae, the in vivo induciblenirBpromoter was inserted into pCS154, upstream of thefasgenes, to create pCS155. In comparison with the previously used vaccine, BALB/c mice immunized orally with serovar Typhimurium χ4550/pCS155 demonstrated significantly higher levels of serum IgG and mucosal IgA against 987P fimbria. Moreover, mucosal IgA against the TGEV C epitope was only detected with serovar Typhimurium χ4550/pCS155. The induced antibodies also recognized the epitopes in the context of the full-length TGEV spike protein. Hence, immune responses to heterologous chimeric fimbriae onSalmonellavaccine vectors can be optimized by using promoters known to be activated in vivo.
Cytopathogenic Effect of
Trichomonas vaginalis
on Human Vaginal Epithelial Cells Cultured In Vitro
Authors: Gilbert R. O. , Elia G. , Beach D. H. , Klaessig Suzanne , Singh B. N. 
Published: July 2002

ABSTRACT

In this study we established human vaginal epithelial cells (hVECs) in culture and evaluated their interaction with
Trichomonas vaginalis
parasites to complement previous studies using other cell types. Primary cultures of hVECs were established. Contaminating fibroblasts were separated from epithelial cells by differential trypsinization. Specific antibody staining revealed that over 92% of cells in hVEC monolayers were epithelial cells.
T. vaginalis
adhered to hVECs and produced severe cytotoxic effects resulting in obliteration of the monolayer within 24 h. Adherence and cytotoxicity were not observed when
T. vaginalis
was exposed to human vaginal fibroblasts or bovine vaginal epithelial cells. Likewise, the bovine parasite
Tritrichomonas foetus
had no cytotoxic effects on hVECs. We concluded that the interaction between
T. vaginalis
and hVECs is both cell specific (limited to epithelial cells and not vaginal fibroblasts) and species specific (limited to human vaginal cells and not bovine cells). Pretreatment of
T. vaginalis
with metronidazole or periodate abolished the adhesion of parasites to cell monolayers and the cytotoxic effect, suggesting involvement of carbohydrate-containing molecules in these processes. Different clinical isolates of
T. vaginalis
caused damage to cultured cells at different rates. Parasites separated from the vaginal cell monolayer by a permeable membrane did not produce a cytopathic effect, suggesting contact-dependent cytotoxicity.
The
Entamoeba histolytica
Mitochondrion-Derived Organelle (Crypton) Contains Double-Stranded DNA and Appears To Be Bound by a Double Membrane
Authors: Ghosh Sudip , Field Jessica , Rogers Rick , Hickman Mark , Samuelson John 
Published: July 2002

ABSTRACT
Amebae have an Hsp60-associated, mitochondrion-derived organelle (crypton). In this study, the crypton was stained with multiple DNA-binding fluorochromes and a monoclonal anti-double-stranded DNA antibody. Transmission microscopy of partially purified cryptons revealed organelles bound by a double membrane.
Macrophage Damage byLeishmania amazonensisCytolysin: Evidence of Pore Formation on Cell Membrane
Authors: Noronha Fátima S. M. , Cruz Jader S. , Beirão Paulo S. L. , Horta M. Fátima 
Published: July 2002

ABSTRACTWe have previously shown that both promastigotes and amastigotes ofLeishmania amazonensiscontain a lytic protein that damages erythrocytes and nucleated cells, including macrophages (F. S. M. Noronha, F. J. Ramalho-Pinto, and M. F. Horta, Infect. Immun. 64:3975–3982, 1996). Using the patch-clamp technique, we show here that cell damage by parasite extracts is mediated by the formation of nonselective pores on the target membrane. This demonstrates thatL. amazonensiscytolysin is a pore-forming protein (PFP), here named leishporin. We show that the diameters of the pores formed by parasite extracts are heterogeneous, varying from ∼1.6 to >6.1 nm according to cytolysin concentration or time. We also show that pore formation involves the binding of the PFP to the target cell membrane, a temperature-independent event that is necessary but not sufficient to lyse cells. This is followed by a temperature-dependent step that triggers lysis, probably the insertion and the polymerization of protein subunits in the lipid bilayer. We provide evidence that suggests that polymerization of single subunits must occur for pore formation. We show, in addition, thatL. amazonensisexpresses molecules antigenically homologous to other PFPs.
CTLA-4 Down-Regulates the Protective Anticryptococcal Cell-Mediated Immune Response
Authors: McGaha Tracy , Murphy Juneann W. 
Published: July 2002

ABSTRACTCell-mediated immune (CMI) responses defined by delayed-type hypersensitivity (DTH) reactivity to cryptococcal culture filtrate antigen (CneF) can be either protective or nonprotective against an infection withCryptococcus neoformans. The protective and nonprotective anticryptococcal DTH responses are induced by different immunogens and have differing activated-T-cell profiles. This study examined the effects of blockade of the interaction between cytotoxic T lymphocyte antigen 4 (CTLA-4) and its ligands B7-1 (CD80) and B7-2 (CD86) on the anticryptococcal DTH responses and protection. We found that CTLA-4 blockade at the time of immunization with the immunogen that induces the protective response, CneF, in complete Freund's adjuvant (CFA) or the immunogen that induces the nonprotective response, heat-killed cryptococcal cells (HKC), enhanced anticryptococcal DTH reactivity. In contrast, blocking CTLA-4 after the immune response was induced failed to enhance responses. Blockade of CTLA-4 in an infection model resulted in earlier development of the anticryptococcal CMI response than in control mice. Concomitant with increases in DTH reactivity in mice treated with anti-CTLA-4 Fab fragments at the time of immunization, there were decreases in cryptococcal CFU in lungs, spleens, and brains compared to controls. Blockade of CTLA-4 resulted in long-term protection, as measured by significantly increased survival times, only in mice given the protective immunogen, CneF-CFA. Anti-CTLA-4 treatment did not shift the response induced by the nonprotective immunogen, HKC, to a long-term protective one. Our data indicate that blockade of CTLA-4 interactions with its ligands may be useful in enhancing host defenses againstC. neoformans.