bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative Roles of Complement Factor 3 and Mannose-Binding Lectin in Host Defense against Infection
Authors: Takahashi Kazue , Shi Lei , Gowda Lakshmi D. , Ezekowitz R. Alan B. 
Published: November 2005

ABSTRACTStaphylococcus aureusis a major cause of severe nosocomial and community-acquired infections. Phagocytes and humoral molecules, including complement, have been proposed to cooperate in host defense against gram-positive bacteria. Circumstantial evidence indicates a role for complement, but this has not been formally defined. Complement activation is initiated by the classical, alternative, or lectin pathway, with the latter requiring mannose-binding lectin (MBL, also known as mannose-binding protein). MBL is an oligomeric serum protein that recognizes carbohydrates decorating a broad range of infectious agents, includingS. aureus. We previously reported that MBL null mice were highly susceptible toS. aureusinfection, confirming that MBL plays a key role in first-line host defense. In this study, we evaluated the relative roles of C3 and MBL againstS. aureusinfection by generating MBL × C3 null mice to compare with C3 single null mice. C3 deficiency alone significantly reduced survival to 19% from 97% of wild-type mice (P< 0.0001). Surprisingly, an additional MBL deficiency reduced the survival further to 7% (P< 0.0001). However, the MBL deficiency alone had a smaller though significant effect on survival, which was 77% (P= 0.018 versus wild-type mice). These results confirm an essential function for complement in host resistance againstS. aureusinfection but also identify an MBL-dependent mechanism that is C3 independent.
Anaplasma phagocytophilumDelay of Neutrophil Apoptosis through the p38 Mitogen-Activated Protein Kinase Signal Pathway
Authors: Choi Kyoung-Seong , Park Joon Tae , Dumler J. Stephen 
Published: November 2005

ABSTRACTHuman granulocytic anaplasmosis is caused by the obligate intracellular bacteriumAnaplasma phagocytophilum. The bacterium avoids host innate defenses in part by infecting, surviving in, and propagating in neutrophils, as well as by inhibiting neutrophil apoptosis. However, the mechanisms ofA. phagocytophilumsurvival in neutrophils and the inhibition of spontaneous apoptosis are not well understood. In this study, we demonstrated that antiapoptotic Mcl-1 protein (Bcl-2 family) expression is maintained and that inhibition of procaspase-3 processing occurs inA. phagocytophilum-infected human neutrophils. An evaluation of p38 mitogen-activated protein kinase (MAPK) showed evidence of increased phosphorylation with infection. Moreover, antagonism of p38 MAPK by the inhibitor SB203580 reversed apoptosis inhibition in live or heat-killedA. phagocytophilum-infected neutrophils. A role for the autocrine or paracrine production of antiapoptotic interleukin 8 (IL-8) expressed withA. phagocytophiluminfection was excluded by the use of IL-8-, IL-8R1 (CXCR1)-, and IL-8R2 (CXCR2)-blocking antibodies. As previously demonstrated, the antiapoptotic effect was initially mediated by exposure toA. phagocytophilumcomponents in heat-killed bacteria. However, an important role for active infection is demonstrated by the additional delay in apoptosis with intracellular growth and the refractory abrogation of this response by the p38 MAPK inhibitor 3 to 6 h after neutrophil infection. These results suggest that the initial activation of the p38 MAPK pathway leading toA. phagocytophilum-delayed neutrophil apoptosis is bypassed with active intracellular infection. Moreover, active intracellular infection contributes more to the overall delay in apoptosis than do components of heat-killedA. phagocytophilumalone.
Cryptococcus neoformans
Gene Involved in Mammalian Pathogenesis Identified by a
Caenorhabditis elegans
Progeny-Based Approach
Authors: Tang Robin J. , Breger Julia , Idnurm Alexander , Gerik Kimberly J. , Lodge Jennifer K. , Heitman Joseph , Calderwood Stephen B. , Mylonakis Eleftherios 
Published: November 2005

ABSTRACT

Caenorhabditis elegans
can serve as a substitute host for the study of microbial pathogenesis. We found that mutations in genes of the fungal pathogen
Cryptococcus neoformans
involved in mammalian virulence allow
C. elegans
to produce greater numbers of progeny than when exposed to wild-type fungus. We used this property to screen a library of
C. neoformans
mutants for strains that permit larger
C. elegans
brood sizes. In this screen, we identified a gene homologous to
Saccharomyces cerevisiae ROM2. C. neoformans rom2
mutation resulted in a defect in mating and growth defects at elevated temperature or in the presence of cell wall or hyperosmolar stresses. An effect of the
C. neoformans rom2
mutation in virulence was confirmed in a murine inhalation infection model. We propose that a screen for progeny-permissive mutants of microorganisms can serve as a high-throughput method for identifying novel loci related to mammalian pathogenesis.
Roles of Specific Amino Acids in the N Terminus of
Pseudomonas aeruginosa
Flagellin and of Flagellin Glycosylation in the Innate Immune Response
Authors: Verma Amrisha , Arora Shiwani K. , Kuravi Sudha K. , Ramphal Reuben 
Published: November 2005

ABSTRACT

The Toll-like receptor 5 (TLR5) binding site has been predicted to be in the N terminus of the flagellin molecule. In order to better define the interaction between the N-terminal amino acids of
Pseudomonas aeruginosa
flagellin and TLR5, site-specific mutations were generated between residues 88 and 97 of
P. aeruginosa
PAK flagellin as well as outside of this region. The mutant flagellins were expressed in
Escherichia coli
BL21(plysS), purified by affinity chromatography, and passed through a polymyxin B column to remove contaminating lipopolysaccharide (LPS). Their ability to stimulate interleukin-8 (IL-8) release from A549 cells was examined. The cloned mutated genes were used to complement a PAK
fliC
mutant in order to test for effects on motility and on IL-8 release by purified flagellar preparations. All the mutations, single or double, in the predicted TLR5 binding region reduced IL-8 signaling to less than 95% of the wild-type flagellin levels, but the single mutation outside the binding region had no effect. Changes made at two amino acid sites resulted in loss/reduction of motility; however, changes made at single sites, i.e., Q83A, L88A, R90A, M91A, L94A, and Q97A, had no effect on motility. The mutated genes encoding two of the motile but poorly signaling flagellins had no compensatory mutations to allow motility. Thus, while it is speculated that pathogen-associated molecular patterns (PAMPs) have evolved in locations that are essential to maintain function, it appears that there is tolerance for at least single amino acid changes in the PAMP of
P. aeruginosa
flagellin. The purpose of flagellin glycosylation in
P. aeruginosa
is unknown. In order to examine its role, if any, in signaling an inflammatory response, we used whole flagella from the motile chromosomal mutant strains PAK
rfbC
and PAO1
rfbC
, which are defective in flagellin glycosylation. IL-8 release from A549 cells stimulated with nonglycosylated flagellar preparations (having less then 1 picogram of LPS/μg) was significantly reduced compared to their respective wild-type flagellar preparations, indicating a role of flagellar glycosylation in the proinflammatory action of
Pseudomonas
flagellin. The basis of the latter activity is unknown, since the glycosylation sites are found in the D3 domain of flagellins and the TLR5 binding site is located in the D1 domain. Thus,
P. aeruginosa
flagellin has evolved additional flagellar signaling mechanisms over that described for
Salmonella
flagellin.
Induction of Protective Serum Meningococcal Bactericidal and Diphtheria-Neutralizing Antibodies and Mucosal Immunoglobulin A in Volunteers by Nasal Insufflations of theNeisseria meningitidisSerogroup C Polysaccharide-CRM197 Conjugate Vaccine Mixed with Chitosan
Authors: Huo Zhiming , Sinha Ruchi , McNeela Edel A. , Borrow Ray , Giemza Rafaela , Cosgrove Catherine , Heath Paul T. , Mills Kingston H. G. , Rappuoli Rino , Griffin George E. , Lewis David J. M. 
Published: November 2005

ABSTRACTThirty-six healthy volunteers received either a single intramuscular injection ofNeisseria meningitidisserogroup C polysaccharide (MCP)-CRM197 conjugate vaccine in alum or two nasal insufflations 28 days apart of the same vaccine powder, without alum, mixed with chitosan. Nasal immunization was well tolerated, with fewer symptoms reported than after intramuscular injection. The geometric mean concentrations of MCP-specific immunoglobulin G (IgG) after one nasal immunization were 3.25 μg/ml in naïve subjects and 14.4 μg/ml in subjects previously immunized parenterally, compared with 4.30 μg/ml in naïve subjects immunized intramuscularly. The geometric mean titer of serum bactericidal antibody (SBA) rose 24-fold after two nasal immunizations in naïve subjects and was comparable to parenteral immunization (1,080 versus 1,625). All subjects achieved SBA titers associated with protection after two nasal immunizations: even those with titers of <8 at entry. A single nasal immunization boosted the SBA titer to ≥128 in 96% of previously immunized subjects, and two immunizations achieved this level in 92% of naive subjects. MCP-specific IgG levels were ∼70% IgG2 and ∼20% IgG1 after nasal or intramuscular immunization. Increases in CRM197-specific IgG and diphtheria toxin-neutralizing activity were observed after nasal or intramuscular immunization, with balanced IgG1/IgG2 and higher IgG4. Significant MCP-specific secretory IgA was detected in nasal wash only after nasal immunization and predominantly on the immunized side. Simple nasal insufflation of existing MCP-CRM197 conjugate vaccines in chitosan offers an inexpensive but effective needle-free prime and boost against serogroup CN. meningitidisand diphtheria.
NoncapsulatedKlebsiella pneumoniaeBearing Mannose-Containing O Antigens Is Rapidly Eradicated from Mouse Lung and Triggers Cytokine Production by Macrophages following Opsonization with Surfactant Protein D
Authors: Kostina Elena , Ofek Itzhak , Crouch Erika , Friedman Rotem , Sirota Lea , Klinger Gil , Sahly Hany , Keisari Yona 
Published: November 2005

ABSTRACTTo better understand the relationship between the surface polysaccharides of pulmonary pathogens and components of the lung innate immune system, we employed selected serotypes ofKlebsiella pneumoniaeexpressing distinct capsular polysaccharides and/or O antigen in a murine model ofK. pneumoniaeinfection. In addition, we examined the effect of surfactant protein D (SP-D) on the cytokine response of human monocyte-derived macrophages to these serotypes in vitro. Noncapsulated mannose-containing O3 serotypes (K50/n and K55/n), which react efficiently with SP-D in vitro, triggered high levels of interleukin-1β (IL-1β) and IL-6 production. In vivo, they were more efficiently cleared from the lungs of mice but not from macrophage-depleted mice. They also were more efficiently internalized by alveolar macrophages in vivo. In contrast, galactose-containing O1 serotypes (K2/n and K21a/n), which interact poorly with SP-D, exhibited significantly lower cytokine production and less efficient pulmonary clearance and were ineffectively internalized by alveolar macrophages. These findings are consistent with in vitro results showing that production of IL-1β and IL-6 mRNA and IL-6 protein by human macrophages exposed to mannose-bearingKlebsiellaO serotypes is significantly increased by SP-D. Thus, survival of inhaled bacteria in the lung depends partially on the lipopolysaccharide structure of the bacteria and their interactions with innate immunity components. We speculate that an imbalance of host SP-D and therefore cytokine levels may result in high susceptibility of the host to the pathogen.
Protective Immunity to the Larval Stages ofOnchocerca volvulusIs Dependent on Toll-Like Receptor 4
Authors: Kerepesi Laura A. , Leon Ofra , Lustigman Sarah , Abraham David 
Published: November 2005

ABSTRACTToll-like receptor 4 (TLR4) has been shown to be important for the induction of Th2-dependent immune responses in mice. Protective immunity against larvalOnchocerca volvulusin mice depends on the development of a Th2 immune response mediated by both interleukin-4 (IL-4) and IL-5. In addition,O. volvuluscontains the rickettsial endosymbiontWolbachia, which has molecules with lipopolysaccharide-like activities that also signal through TLR4. We therefore hypothesized that protective immunity toO. volvuluswould not develop in C3H/HeJ mice which have a mutation in theTlr4gene (TLR4 mutant), either because of a decreased Th2 response to the larvae or because of the absence of a response toWolbachia.TLR4-mutant mice were immunized againstO. volvuluswith irradiated third-stage larvae, and it was observed that Th2 responses were elevated based on increased IL-5 production, total immunoglobulin E (IgE) levels, antigen-specific IgG1 response, and eosinophil recruitment. Protective immunity, however, did not develop in the TLR4-mutant mice. The Th1 response, as measured by gamma interferon production from spleen cells, was comparable in both wild-type and TLR4-mutant mice. Furthermore, antibody responses toWolbachiawere absent in both wild-type and TLR4-mutant mice. Therefore, the defect in the development of a protective immune response againstO. volvulusin TLR4-mutant mice is not due to loss of Th2 immunity or the response toWolbachiabut is due to an unidentified TLR4-dependent larval killing mechanism.
Shiga Toxin 2 and Lipopolysaccharide Induce Human Microvascular Endothelial Cells To Release Chemokines and Factors That Stimulate Platelet Function
Authors: Guessous Fadila , Marcinkiewicz Marek , Polanowska-Grabowska Renata , Kongkhum Sudawadee , Heatherly Daniel , Obrig Tom , Gear Adrian R. L. 
Published: November 2005

ABSTRACT

Shiga toxins (Stxs) produced by
Shigella dysenteriae
type 1 and enterohemorrhagic
Escherichia coli
are the most common cause of hemolytic-uremic syndrome (HUS). It is well established that vascular endothelial cells, mainly those located in the renal microvasculature, are targets for Stxs. The aim of the present research was to evaluate whether
E. coli
-derived Shiga toxin 2 (Stx2) incubated with human microvascular endothelial cells (HMEC-1) induces release of chemokines and other factors that might stimulate platelet function. HMEC-1 were exposed for 24 h in vitro to Stx2, lipopolysaccharide (LPS), or the Stx2-LPS combination, and chemokine production was assessed by immunoassay. More interleukin-8 was released than stromal cell-derived factor 1α (SDF-1α) or SDF-1β and RANTES. The Stx2-LPS combination potentiated chemokine release, but Stx2 alone caused more release of SDF-1α at 24 h than LPS or Stx2-LPS did. In the presence of low ADP levels, HMEC-1 supernatants activated platelet function assessed by classical aggregometry, single-particle counting, granule secretion, P-selectin exposure, and the formation of platelet-monocyte aggregates. Supernatants from HMEC-1 exposed only to Stx2 exhibited enhanced exposure of platelet P-selectin and platelet-THP-1 cell interactions. Blockade of platelet cyclooxygenase by indomethacin prevented functional activation. The chemokine RANTES enhanced platelet aggregation induced by SDF-1α, macrophage-derived chemokine, or thymus and activation-regulated chemokine in the presence of very low ADP levels. These data support the hypothesis that microvascular endothelial cells exposed to
E. coli
O157:H7-derived Stx2 and LPS release chemokines and other factors, which when combined with low levels of primary agonists, such as ADP, cause platelet activation and promote the renal thrombosis associated with HUS.
Specific-Pathogen-Free Pigs as an Animal Model for Studying
Chlamydia trachomatis
Genital Infection
Authors: Vanrompay Daisy , Hoang Thi Q. T. , De Vos Liselotte , Verminnen Kristel , Harkinezhad Taher , Chiers Koen , Morré Servaas A. , Cox Eric 
Published: November 2005

ABSTRACT

The purpose of the present study was to evaluate pigs as a large-animal model for female genital infection with two
Chlamydia trachomatis
human serovar E strains. Sixteen-week-old specific-pathogen-free female pigs (gilts) were intravaginally infected with the trachoma type E reference strain Bour or the urogenital serovar E strain 468. Several conclusions can be drawn from our findings on the pathogenicity of a primary
C. trachomatis
genital infection in gilts. First of all, we demonstrated that the serovar E strains Bour and 468 could ascend in the genital tract of gilts. The serovar E strains could replicate in the superficial columnar cervical epithelium and in the superficial epithelial layer of the uterus, which are known to be the specific target sites for a
C. trachomatis
genital infection in women. Second, inflammation and pathology occurred at the replication sites. Third, the organisms could trigger a humoral immune response, as demonstrated by the presence of immunoglobulin M (IgM), IgG, and IgA in both serum and genital secretion samples. Our findings imply that the pig model might be useful for studying the pathology, pathogenesis, and immune response to a
C. trachomatis
infection of the genital system.
Leishmania pifanoiAmastigotes Avoid Macrophage Production of Superoxide by Inducing Heme Degradation
Authors: Pham Nam-Kha , Mouriz Jennifer , Kima Peter E. 
Published: November 2005

ABSTRACTWhereas infections of macrophages by promastigote forms ofLeishmania mexicana pifanoiinduce the production of superoxide, infections by amastigotes barely induce superoxide production. Several approaches were employed to gain insight into the mechanism by which amastigotes avoid eliciting superoxide production. First, in experiments with nitroblue tetrazolium, we found that 25% of parasitophorous vacuoles (PVs) that harbor promastigotes are positive for the NADPH oxidase complex, in contrast to only 2% of PVs that harbor amastigotes. Second, confocal microscope analyses of infected cells labeled with antibodies to gp91phoxrevealed that this enzyme subunit is found in PVs that harbor amastigotes. Third, in immunoblots of subcellular fractions enriched with PVs from amastigote-infected cells and probed with antibodies to gp91phox, only the 65-kDa premature form of gp91phoxwas found. In contrast, subcellular fractions from macrophages that ingested zymosan particles contained both the 91- and 65-kDa forms of gp91phox. This suggested that only the immature form of gp91phoxis recruited to PVs that harbor amastigotes. Given that gp91phoxmaturation is dependent on the availability of heme, we found that infections byLeishmaniaparasites induce an increase in heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation. Infections by amastigotes performed in the presence of metalloporphyrins, which are inhibitors of HO-1, resulted in superoxide production by infected macrophages. Taken together, we propose thatLeishmaniaamastigotes avoid superoxide production by inducing an increase in heme degradation, which results in blockage of the maturation of gp91phox, which prevents assembly of the NADPH oxidase enzyme complex.
Regulation of Impaired Protein Kinase C Signaling by Chemokines in Murine Macrophages during Visceral Leishmaniasis
Authors: Dey Ranadhir , Sarkar Arup , Majumder Nivedita , Bhattacharyya (Majumdar) Suchandra , Roychoudhury Kaushik , Bhattacharyya Sandip , Roy Syamal , Majumdar Subrata 
Published: November 2005

ABSTRACTThe protein kinase C (PKC) family regulates macrophage function involved in host defense against infection. In the case ofLeishmania donovaniinfection, the impairment of PKC-mediated signaling is one of the crucial events for the establishment of parasite into the macrophages. Earlier reports established that C-C chemokines mediated protection against leishmaniasis via the generation of nitric oxide after 48 h. In this study, we investigated the role of MIP-1α and MCP-1 in the regulation of impaired PKC activity in the early hours (6 h) of infection. These chemokines restored Ca2+-dependent PKC activity and inhibited Ca2+-independent atypical PKC activity inL. donovani-infected macrophages under both in vivo and in vitro conditions. Pretreatment of macrophages with chemokines induced superoxide anion generation by activating NADPH oxidase components in infected cells. Chemokine administration in vitro induced the migration of infected macrophages and triggered the production of reactive oxygen species. In vivo treatment with chemokines significantly restricted the parasitic burden in livers as well as in spleens. Collectively, these results indicate a novel regulatory role of C-C chemokines in controlling the intracellular growth and multiplication ofL. donovani, thereby demonstrating the antileishmanial properties of C-C chemokines in the disease process.
A Mutant ofFrancisella tularensisStrain SCHU S4 Lacking the Ability To Express a 58-Kilodalton Protein Is Attenuated for Virulence and Is an Effective Live Vaccine
Authors: Twine Susan , Byström Mona , Chen Wangxue , Forsman Mats , Golovliov Igor , Johansson Anders , Kelly John , Lindgren Helena , Svensson Kerstin , Zingmark Carl , Conlan Wayne , Sjöstedt Anders 
Published: November 2005

ABSTRACTFrancisella tularensissubsp.tularensis(type A) strain SCHU S4 is a prototypic strain of the pathogen that is highly virulent for humans and other mammals. Its intradermal (i.d.) 50% lethal dose (LD50) for mice is <10 CFU. We discovered a spontaneous mutant, designated FSC043, of SCHU S4 with an i.d. LD50of >108CFU. FSC043 effectively vaccinated mice against challenge with a highly virulent type A strain, and the protective efficacy was at least as good as that ofF. tularensisLVS, an empirically attenuated strain which has been used as an efficacious human vaccine. Comparative proteomics was used to identify two proteins of unknown function that were identified as defective in LVS and FSC043, and deletion mutants of SCHU S4 were created for each of the two encoding genes. One mutant, the ΔFTT0918 strain, failed to express a 58-kDa protein, had an i.d. LD50of ∼105CFU, and was found to be less capable than SCHU S4 of growing in peritoneal mouse macrophages. Mice that recovered from sublethal infection with the ΔFTT0918 mutant survived when challenged 2 months later with >100 LD50s of the highly virulent type A strain FSC033. This is the first report of the generation of defined mutants ofF. tularensissubsp.tularensisand their use as live vaccines.
Mycobacterium-Induced Potentiation of Type 1 Immune Responses and Protection against Malaria Are Host Specific
Authors: Page Kathleen R. , Jedlicka Anne E. , Fakheri Benjamin , Noland Gregory S. , Kesavan Anup K. , Scott Alan L. , Kumar Nirbhay , Manabe Yukari C. 
Published: November 2005

ABSTRACTMalaria and tuberculosis are endemic in many regions of the world, and coinfection with the two pathogens is common. In this study, we examined the effects of long- and short-term infection withMycobacterium tuberculosison the course of a lethal form of murine malaria in resistant (C57BL/6) and susceptible (BALB/c) mice. C57BL/6 mice coinfected withM. tuberculosisCDC1551 andPlasmodium yoelii17XL had a lower peak parasitemia and increased survival compared to mice infected withP. yoelii17XL alone. Splenic microarray analysis demonstrated potentiation of type 1 immune responses in coinfected C57BL/6 mice, which was especially prominent 5 days after infection withP. yoelii17XL. Splenocytes from coinfected C57BL/6 mice produced higher levels of gamma interferon (IFN-γ) and tumor necrosis factor alpha than splenocytes from mice infected with either pathogen alone. Interestingly, mycobacterium-induced protection against lethalP. yoeliiis mouse strain specific. BALB/c mice were significantly more susceptible than C57BL/6 mice to infection withP. yoelii17XL and were not protected against lethal malaria by coinfection withM. tuberculosis. In addition,M. tuberculosisdid not augment IFN-γ responses in BALB/c mice subsequently infected withP. yoelii17XL. These data indicate thatM. tuberculosis-induced potentiation of type 1 immune responses is associated with protection against lethal murine malaria.