bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mycobacterium tuberculosisUptake by Recipient Host Macrophages Is Influenced by Environmental Conditions in the Granuloma of the Infectious Individual and Is Associated with Impaired Production of Interleukin-12 and Tumor Necrosis Factor Alpha
Authors: Li Yong-jun , Petrofsky Mary , Bermudez Luiz E. 
Published: October 2002

ABSTRACTTransmission ofMycobacterium tuberculosisfrom one individual to another usually is associated with episodes of coughing. The bacteria leave the environment of the lung cavity of the infected person and travel in droplets to reach the recipient's respiratory tract. Therefore, at the time that the bacteria encounter alveolar cells (macrophages and epithelial cells) in the new host, they express virulence determinants that are regulated by the environmental conditions in the infected person. To determine if those environmental conditions encountered in the lung cavity (hyperosmolarity, acidic pH, and low oxygen tension, among others) would influence the uptake ofM. tuberculosisby the recipient's alveolar macrophages,M. tuberculosisH37Rv was incubated under several conditions for different periods of time, washed at 4°C, and used to infect human monocyte-derived macrophages. While increased osmolarity had no effect onM. tuberculosisuptake compared to the uptake of bacteria grown on 7H10 Middlebrook medium, both acidic pH and anaerobiosis increased the uptake of the H37Rv strain four- to sixfold. Using anti-CD11b receptor blocking antibodies or mannoside to inhibit the uptake ofM. tuberculosisby macrophages, we determined that while uptake ofM. tuberculosiscultured on 7H10 medium was inhibited 77% ± 6% in the presence of anti-CD11b antibody, the antibody had no effect on the uptake ofM. tuberculosisincubated at pH 6.0 and was associated with 27% inhibition ofM. tuberculosispreviously exposed to anaerobic conditions. The mannose receptor was also not involved with invasion after exposure to acidic conditions, and mannoside resulted in only 32% inhibition of uptake by macrophages ofM. tuberculosisexposed to anaerobiosis. Uptake by macrophages also resulted in the secretion of significantly lower amounts of interleukin-12 and tumor necrosis factor alpha than that by macrophages infected with a strain cultured under laboratory conditions.M. tuberculosiscultured under the pH and oxygen concentration found in the granuloma expresses a large number of proteins that are different from the proteins expressed by bacteria grown under laboratory conditions. The results suggest thatM. tuberculosisin vivo may be adapted to gain access to the intracellular environment in a very efficient fashion and may do so by using different receptors from the complement and mannose receptors.
DNA Sequence and Mutational Analyses of the pVir Plasmid of
Campylobacter jejuni
81-176
Authors: Bacon David J. , Alm Richard A. , Hu Lan , Hickey Thomas E. , Ewing Cheryl P. , Batchelor Roger A. , Trust Trevor J. , Guerry Patricia 
Published: October 2002

ABSTRACT

The circular pVir plasmid of
Campylobacter jejuni
strain 81-176 was determined to be 37,468 nucleotides in length with a G+C content of 26%. A total of 83% of the plasmid represented coding information, and all but 2 of the 54 predicted open reading frames were encoded on the same DNA strand. There were seven genes on the plasmid in a continguous region of 8.9 kb that encoded orthologs of type IV secretion proteins found in
Helicobacter pylori,
including four that have been described previously (D. J. Bacon, R. A. Alm, D. H. Burr, L. Hu, D. J. Kopecko, C. P. Ewing, T. J. Trust, and P. Guerry, Infect. Immun. 68:4384-4390, 2000). There were seven other pVir-encoded proteins that showed significant similarities to proteins encoded by the plasticity zones of either
H. pylori
J99 or 26695. Mutational analyses of 19 plasmid genes identified 5 additional genes that affect in vitro invasion of intestinal epithelial cells. These included one additional gene encoding a component of a type IV secretion system, an ortholog of Cj0041 from the chromosome of
C. jejuni
NCTC 11168, two
Campylobacter
plasmid-specific genes, and an ortholog of HP0996 from the plasticity zone of
H. pylori
26695.
Phage Therapy of Local and Systemic Disease Caused by
Vibrio vulnificus
in Iron-Dextran-Treated Mice
Authors: Cerveny Karen E. , DePaola Angelo , Duckworth Donna H. , Gulig Paul A. 
Published: October 2002

ABSTRACT

Vibrio vulnificus
is a gram-negative bacterium that contaminates filter-feeding shellfish such as oysters. After ingestion of contaminated oysters, predisposed people may experience highly lethal septicemia. Contamination of wounds with the bacteria can result in devastating necrotizing fasciitis, which can progress to septicemia. The extremely rapid progression of these diseases can render antibiotic treatment ineffective, and death is a frequent outcome. In this study, we examined the potential use of bacteriophages as therapeutic agents against
V. vulnificus
in an iron-dextran-treated mouse model of
V. vulnificus
infection. Mice were injected subcutaneously with 10 times the lethal dose of
V. vulnificus
and injected intravenously, either simultaneously or at various times after infection, with phages. Treatment of mice with phages could prevent death; systemic disease, as measured by CFU per gram of liver and body temperature; and local disease, as measured by CFU per gram of lesion material and histopathologic analysis. Two different phages were effective against three different
V. vulnificus
strains with various degrees of virulence, while a third phage that required the presence of seawater to lyse bacteria in vitro was ineffective at treating mice. Optimum protection required that the phages be administered within 3 h of bacterial inoculation at doses as high as 10
8
PFU. One of the protective phages had a half-life in blood of over 2 h. These results demonstrate that bacteriophages have therapeutic potential for both localized and systemic infections caused by
V. vulnificus
in animals. This model should be useful in answering basic questions regarding phage therapy.
Infection withStrongyloides venezuelensisInduces Transient Airway Eosinophilic Inflammation, an Increase in Immunoglobulin E, and Hyperresponsiveness in Rats
Authors: Silveira Micheline R. , Nunes Kênia P. , Cara Denise C. , Souza Danielle G. , Corrêa Ary , Teixeira Mauro M. , Negrão-Corrêa Deborah 
Published: October 2002

ABSTRACTInfection by nematode parasites with a pulmonary migration in their life cycle and allergic asthma are two highly prevalent diseases in humans; therefore, one may expect both may occur concomitantly. There is a predominant and essential role of Th2 lymphocytes in the mechanisms underlying the control of parasite elimination as well as in the pathology observed in the asthmatic lung. The consequences of such situations have been explored, with controversial results, justifying the development of experimental models in which the relationship between allergic airway inflammation and helminth infection might be evaluated. The present work describes the inflammatory, humoral, and functional changes that occur in the lung of rats after single (subcutaneous inoculation of 1,500 L3 larvae) or multiple (five weekly subcutaneous inoculations of 1,500 L3 larvae)Strongyloides venezuelensisinfections. The results show that the migration ofS. venezuelensislarvae through the lungs of infected rats induces a local eosinophilic inflammation process which is mostly focal and parenchymal for rats infected a single time and which is peribronchial after multiple infections. The inflammatory process is accompanied by mucus hypersecretion, thickening of bronchial epithelial and muscle layers, and local increase in immunoglobulin E concentrations that peak after 5 to 7 days and are resolved after 12 days of single or multiple infections. The peak of lung immunopathologic changes observed in infected rats coincides with lung airway hyperresponsiveness (AHR), a key functional alteration in asthma. We propose that this experimental model is ideal to carry out further studies on immunoprotection against nematode infection versus immunopathology of allergic airway inflammation.
Intracellular Growth of
Legionella pneumophila
Gives Rise to a Differentiated Form Dissimilar to Stationary-Phase Forms
Authors: Garduño Rafael A. , Garduño Elizabeth , Hiltz Margot , Hoffman Paul S. 
Published: October 2002

ABSTRACT

When
Legionella pneumophila
grows in HeLa cells, it alternates between a replicative form and a morphologically distinct “cyst-like” form termed MIF (mature intracellular form). MIFs are also formed in natural amoebic hosts and to a lesser extent in macrophages, but they do not develop in vitro. Since MIFs accumulate at the end of each growth cycle, we investigated the possibility that they are in vivo equivalents of stationary-phase (SP) bacteria, which are enriched for virulence traits. By electron microscopy, MIFs appeared as short, stubby rods with an electron-dense, laminar outer membrane layer and a cytoplasm largely occupied by inclusions of poly-β-hydroxybutyrate and laminations of internal membranes originating from the cytoplasmic membrane. These features may be responsible for the bright red appearance of MIFs by light microscopy following staining with the phenolic Giménez stain. In contrast, SP bacteria appeared as dull red rods after Giménez staining and displayed a typical gram-negative cell wall ultrastructure. Outer membranes from MIFs and SP bacteria were equivalent in terms of the content of the peptidoglycan-bound and disulfide bond cross-linked OmpS porin, although additional proteins, including Hsp60 (which acts as an invasin for HeLa cells), were detected only in preparations from MIFs. Proteomic analysis revealed differences between MIFs and SP forms; in particular, MIFs were enriched for an ∼20-kDa protein, a potential marker of development. Compared with SP bacteria, MIFs were 10-fold more infectious by plaque assay, displayed increased resistance to rifampin (3- to 5-fold) and gentamicin (10- to 1,000-fold), resisted detergent-mediated lysis, and tolerated high pH. Finally, MIFs had a very low respiration rate, consistent with a decreased metabolic activity. Collectively, these results suggest that intracellular
L. pneumophila
differentiates into a cyst-like, environmentally resilient, highly infectious, post-SP form that is distinct from in vitro SP bacteria. Therefore, MIFs may represent the transmissible environmental forms associated with Legionnaires' disease.
Candida albicansKilling by RAW 264.7 Mouse Macrophage Cells: Effects ofCandidaGenotype, Infection Ratios, and Gamma Interferon Treatment
Authors: Marcil A. , Harcus D. , Thomas D. Y. , Whiteway M. 
Published: October 2002

ABSTRACTPhagocytic cells such as neutrophils and macrophages are potential components of the immune defense that protects mammals againstCandida albicansinfection. We have tested the interaction between the mouse macrophage cell line RAW 264.7 and a variety of mutant strains ofC. albicans. We used an end point dilution assay to monitor the killing ofC. albicansat low multiplicities of infection (MOIs). Several mutants that show reduced virulence in mouse systemic-infection models show reduced colony formation in the presence of macrophage cells. To permit analysis of the macrophage-Candidainteraction at higher MOIs, we introduced a luciferase reporter gene into wild-type and mutantCandidacells and used loss of the luminescence signal to quantify proliferation. This assay gave results similar to those for the end point dilution assay. Activation of the macrophages with mouse gamma interferon did not enhance anti-Candidaactivity. Continued coculture of theCandidaand macrophage cells eventually led to death of the macrophages, but for the RAW 264.7 cell line this was not due to apoptotic pathways involving caspase-8 or -9 activation. In generalCandidacells defective in the formation of hyphae were both less virulent in animal models and more sensitive to macrophage engulfment and growth inhibition. However the nonvirulent, hypha-defectivecla4mutant line was considerably more resistant to macrophage-mediated inhibition than the wild-type strain. Thus although mutants sensitive to engulfment are typically less virulent in systemic-infection models, sensitivity to phagocytic macrophage cells is not the unique determinant ofC. albicansvirulence.
Shigella flexneri
DegP Facilitates IcsA Surface Expression and Is Required for Efficient Intercellular Spread
Authors: Purdy Georgiana E. , Hong Mei , Payne Shelley M. 
Published: October 2002

ABSTRACT

A
degP
mutant of
Shigella flexneri
was identified in a screen for insertion mutants that invaded cultured cells but did not form wild-type plaques in monolayers. The
degP
mutant SM1100 invaded Henle cells at wild-type levels and induced apoptosis in macrophages but formed smaller plaques than those formed by wild-type
S. flexneri
in confluent monolayers of Henle and Caco-2 cells. The proportion of SM1100 bacteria with IcsA localized to the bacterial pole, a process required for actin polymerization into actin “tails,” was reduced compared to results with wild-type bacteria. The reduction in proper IcsA localization may account for the reduced plaque size of the
degP
mutant. Although DegP is a protease, the protease activity of
S. flexneri
DegP was not required for IcsA localization or the formation of plaques in Henle cell monolayers. DegP was also required for efficient polar IcsA localization in
E. coli
expressing
icsA
. In addition, the growth or survival of SM1100 was compromised compared to that of the wild type at elevated temperatures and in acidic conditions.
Staphylococcus aureus
Aconitase Inactivation Unexpectedly Inhibits Post-Exponential-Phase Growth and Enhances Stationary-Phase Survival
Authors: Somerville Greg A. , Chaussee Michael S. , Morgan Carrie I. , Fitzgerald J. Ross , Dorward David W. , Reitzer Lawrence J. , Musser James M. 
Published: October 2002

ABSTRACT

Staphylococcus aureus
preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon and energy for post-exponential-phase growth and virulence factor production are derived from the catabolism of acetate mediated by the TCA cycle. To test this hypothesis, the aconitase gene was genetically inactivated in a human isolate of
S. aureus
, and the effects on physiology, morphology, virulence factor production, virulence for mice, and stationary-phase survival were examined. TCA cycle inactivation prevented the post-exponential growth phase catabolism of acetate, resulting in premature entry into the stationary phase. This phenotype was accompanied by a significant reduction in the production of several virulence factors and alteration in host-pathogen interaction. Unexpectedly, aconitase inactivation enhanced stationary-phase survival relative to the wild-type strain. Aconitase is an iron-sulfur cluster-containing enzyme that is highly susceptible to oxidative inactivation. We speculate that reversible loss of the iron-sulfur cluster in wild-type organisms is a survival strategy used to circumvent oxidative stress induced during host-pathogen interactions. Taken together, these data demonstrate the importance of the TCA cycle in the life cycle of this medically important pathogen.
Protection against ExperimentalHelicobacter pyloriInfection after Immunization with InactivatedH. pyloriWhole-Cell Vaccines
Authors: Raghavan S. , Hjulström M. , Holmgren J. , Svennerholm A.-M. 
Published: October 2002

ABSTRACTThe protective effect of therapeutic oral immunization with homologous and heterologous formalin-inactivatedHelicobacter pyloricells given together with cholera toxin as an adjuvant was evaluated with C57BL/6 mice infected withH. pyloriSydney strain 1 (SS1). The bacteria used for immunization were strains that were either homologous or heterologous with regard to the O antigen (i.e., the Lewis antigen [Le antigen]) expressed by the lipopolysaccharide of the infectingH. pyloriSS1 strain. We found that repeated oral immunization with inactivatedH. pyloriSS1 cells can significantly inhibit an existing infection (P< 0.001) and that the protection induced by such therapeutic immunization extends to protection against reinfection (P< 0.001). A similar level of protection was also achieved by immunization with another inactivatedH. pyloristrain having the same O antigen (Le antigen) as the infectingH. pyloriSS1 strain. In contrast, immunization with inactivated strains expressing a heterologous O antigen, Lex, provided less protection or no protection. Immunization withH. pylorilysate preparations, on the other hand, resulted in significant comparable protection whether the lysates were prepared from an Lexstrain or an Leystrain. Postimmunization gastritis was seen in mice that were protected after vaccination but not in unimmunized or unprotected mice. In conclusion, therapeutic immunization with inactivatedH. pyloriwhole-cell vaccines may provide strong protection both against experimentalH. pyloriinfection and against later reinfection.
Salmonella enterica
Serovar Typhi Modulates Cell Surface Expression of Its Receptor, the Cystic Fibrosis Transmembrane Conductance Regulator, on the Intestinal Epithelium
Authors: Lyczak Jeffrey B. , Pier Gerald B. 
Published: October 2002

ABSTRACT

The cystic fibrosis transmembrane conductance regulator (CFTR) protein is an epithelial receptor mediating the translocation of
Salmonella enterica
serovar Typhi to the gastric submucosa. Since the level of cell surface CFTR is directly related to the efficiency of serovar Typhi translocation, the goal of this study was to measure CFTR expression by the intestinal epithelium during infection. CFTR protein initially present in the epithelial cell cytoplasm was rapidly trafficked to the plasma membrane following exposure to live serovar Typhi or bacterial extracts. CFTR-dependent bacterial uptake by epithelial cells increased (>100-fold) following CFTR redistribution. The bacterial factor which triggers CFTR redistribution is heat and protease sensitive. These data suggest that serovar Typhi induces intestinal epithelial cells to increase membrane CFTR levels, leading to enhanced bacterial ingestion and submucosal translocation. This could be a key, early step in the infectious process leading to typhoid fever.
Modulation of Inducible Nitric Oxide Synthase Expression by the Attaching and Effacing Bacterial Pathogen
Citrobacter rodentium
in Infected Mice
Authors: Vallance Bruce A. , Deng Wanyin , De Grado Myriam , Chan Crystal , Jacobson Kevan , Finlay B. Brett 
Published: October 2002

ABSTRACT

Citrobacter rodentium
belongs to the attaching and effacing family of enteric bacterial pathogens that includes both enteropathogenic and enterohemorrhagic
Escherichia coli
. These bacteria infect their hosts by colonizing the intestinal mucosal surface and intimately attaching to underlying epithelial cells. The abilities of these pathogens to exploit the cytoskeleton and signaling pathways of host cells are well documented, but their interactions with the host's antimicrobial defenses, such as inducible nitric oxide synthase (iNOS), are poorly understood. To address this issue, we infected mice with
C. rodentium
and found that iNOS mRNA expression in the colon significantly increased during infection. Immunostaining identified epithelial cells as the major source for immunoreactive iNOS. Finding that nitric oxide (NO) donors were bacteriostatic for
C. rodentium
in vitro, we examined whether iNOS expression contributed to host defense by infecting iNOS-deficient mice. Loss of iNOS expression caused a small but significant delay in bacterial clearance without affecting tissue pathology. Finally, immunofluorescence staining was used to determine if iNOS expression was localized to infected cells by staining for the
C. rodentium
virulence factor, translocated intimin receptor (Tir), as well as iNOS. Interestingly, while more than 85% of uninfected epithelial cells expressed iNOS, fewer than 15% of infected (Tir-positive) cells expressed detectable iNOS. These results demonstrate that both iNOS and intestinal epithelial cells play an active role in host defense during
C. rodentium
infection. However, the selective expression of iNOS by uninfected but not infected cells suggests that this pathogen has developed mechanisms to locally limit its exposure to host-derived NO.
ATP and Control of Intracellular Growth of Mycobacteria by T Cells
Authors: Canaday David H. , Beigi Reza , Silver Richard F. , Harding Clifford V. , Boom W. Henry , Dubyak George R. 
Published: October 2002

ABSTRACTExtracellular ATP at millimolar concentrations inhibits growth of mycobacteria in human macrophages. Whether T cells can produce sufficient ATP is unknown. CD4+and CD8+T cells did not release sufficient ATP through either degranulation or lysis of bystander cells to restrict growth ofMycobacterium bovisBCG in monocytes.
Characterization and Immunogenicity of the CagF Protein of thecagPathogenicity Island ofHelicobacter pylori
Authors: Seydel Anke , Tasca Elisabetta , Berti Duccio , Rappuoli Rino , Del Giudice Giuseppe , Montecucco Cesare 
Published: October 2002

ABSTRACTHelicobacter pyloriinfection causes severe gastroduodenal diseases in humans. Its virulence is strongly increased by the presence of thecagpathogenicity island (cagPAI). It has been shown that CagA, a major antigen in humans, is translocated to the host cell via a secretion system encoded by thecagPAI. The roles of many of the proteins encoded within thecagPAI are not known. Here we report on the cloning and expression of CagF, one of those proteins. We show that CagF is associated to the outer membrane ofH. pyloriG27 and that the protein is always expressed with electrophoretic mobility variations among the 20 strains tested here. We have also found that natural infection withH. pyloriis able to induce antibodies against CagF.
Comparative Proteomic Analysis of Extracellular Proteins of
Edwardsiella tarda
Authors: Tan Y. P. , Lin Q. , Wang X. H. , Joshi S. , Hew C. L. , Leung K. Y. 
Published: October 2002

ABSTRACT

A comparison of extracellular proteins of virulent and avirulent
Edwardsiella tarda
strains revealed several major, virulent-strain-specific proteins. Proteomic analysis identified two of the proteins in the virulent strain PPD130/91 as flagellin and SseB, which are virulence factors in bacterial pathogens. PCR amplification and DNA sequencing confirmed the presence of the genes that encode these proteins. Our results clearly demonstrated the potency of the proteomic approach in identifying virulence factors.
Opsonization of
Actinobacillus actinomycetemcomitans
by Immunoglobulin G Antibody Reactive with Phosphorylcholine
Authors: Purkall Donald , Tew John G. , Schenkein Harvey A. 
Published: October 2002

ABSTRACT

We used two strains of
Actinobacillus actinomycetemcomitans
, one bearing phosphorylcholine (PC) (strain D045D-40) and one devoid of PC antigens (strain DB03A-42), as well as a nonencapsulated strain of
Streptococcus pneumoniae
(strain 39937), to examine the opsonic properties of physiological concentrations (⩽30 μg/ml) of purified human anti-PC immunoglobulin G (IgG). Anti-PC bound to both
A. actinomycetemcomitans
DO45D-40 and
S. pneumoniae
39937 and induced superoxide anion production by polymorphonuclear neutrophils; induction of the oxidative burst was inhibited by antibodies to either CD16 or CD32. Thus, anti-PC IgG at concentrations present in most human sera promotes the opsonization of PC-expressing strains of
A. actinomycetemcomitans
in the absence of complement, implying that anti-PC may be a protective antibody against such strains of bacteria.