bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disruption of Putative Regulatory Loci in
Listeria monocytogenes
Demonstrates a Significant Role for Fur and PerR in Virulence
Authors: Rea Rosemarie B. , Gahan Cormac G. M. , Hill Colin 
Published: January 2004

ABSTRACT

The ability to adapt to adverse environmental conditions encountered in food and during host infection is a sine qua non for a successful
Listeria monocytogenes
infection. This ability is likely to depend on complex regulatory pathways controlled by a number of key regulators. We utilized the pORI19 plasmid integration system to analyze the role of six putative regulatory loci in growth under suboptimal environmental conditions and during murine infection. Disruption of loci encoding a topoisomerase III (
lmo2756
), a putative methyltransferase (
lmo0581
), and a regulator of the MarR family (
lmo1618
) revealed roles for the methyltransferase and the MarR regulator in growth under environmental stress conditions. However, plasmid integration into these loci had no impact on virulence potential in the murine model of infection. Disruption of the alternative sigma factor Sigma-H resulted in a mutant that demonstrated reduced growth potential in minimal medium. Murine studies indicated a minor role for this sigma factor in the infectious process. Strikingly, disruption of both
perR
and
fur
loci resulted in mutants that are significantly affected in virulence for mice, with the
fur
mutant demonstrating the greatest reduction in virulence potential. Both
perR
and
fur
mutants demonstrated increased resistance to hydrogen peroxide and the
fur
mutant was sensitive to low-iron conditions. The virulence defect of both
fur
and
perR
mutants could be rescued by iron-overload after esculetin treatment of mice, suggesting that the in vivo role of these gene products is to procure iron for bacterial growth.
Cytokine Production in Whole Blood Cultures from a Fishing Community in an Area of High Endemicity forSchistosoma mansoniin Uganda: the Differential Effect of Parasite Worm and Egg Antigens
Authors: Joseph Sarah , Jones Frances M. , Kimani Gachuhi , Mwatha Joseph K. , Kamau Timothy , Kazibwe Francis , Kemijumbi Jovanice , Kabatereine Narcis B. , Booth Mark , Kariuki Henry C. , Ouma John H. , Vennervald Birgitte J. , Dunne David W. 
Published: January 2004

ABSTRACTThe human host is continuously exposed to the egg and the adult worm developmental stages ofSchistosoma mansoniduring chronic infections with the parasite. To assess the cytokine responses induced by these different costimulating stages and how they are influenced by host age and infection intensity, whole blood samples from a cross-sectional cohort of 226 members of a Ugandan fishing community who had been resident in an area with high transmission ofS. mansonifor the previous 10 years or from birth were stimulated withS. mansoniegg antigen (SEA) or worm antigen (SWA). SWA-specific gamma interferon (IFN-γ) production increased with age, and the levels of SWA- and SEA-specific interleukin 3 (IL-3) were weakly correlated with schistosome infection intensity. The production of most cytokines was little affected by age or infection intensity but was either SEA or SWA specific. One hundred thirty-two members of the cohort coproduced IL-5 and IL-13 specifically in response to SWA, whereas only 15 produced these cytokines, and at much lower levels, in response to SEA. IL-10, IL-4, and IFN-γ were also produced in response to SWA, whereas the response to SEA consisted almost exclusively of IL-10. Our results suggest that, in contrast to what has been described for the murine model ofS. mansoniand during acute human infections, chronic intense exposure to and infection withS. mansoniin this cohort resulted in very low levels of response to SEA in vitro in the presence of a vigorous and mixed Th1-Th2 response to SWA.
Measurement of Antibody Levels against Region II of the Erythrocyte-Binding Antigen 175 of
Plasmodium falciparum
in an Area of Malaria Holoendemicity in Western Kenya
Authors: Ohas Eunita A. , Adams John H. , Waitumbi John N. , Orago Alloys S. S. , Barbosa Arnoldo , Lanar David E. , Stoute José A. 
Published: January 2004

ABSTRACT

Region II of the 175-kDa erythrocyte-binding antigen (EBA-175RII) of
Plasmodium falciparum
is functionally important in sialic acid-dependent erythrocyte invasion and is considered a prime target for an invasion-blocking vaccine. The objectives of this study were to (i) determine the prevalence of anti-EBA-175RII antibodies in a naturally exposed population, (ii) determine whether naturally acquired antibodies have a functional role by inhibiting binding of EBA-175RII to erythrocytes, and (iii) determine whether antibodies against EBA-175RII correlate with immunity to clinical malaria. We treated 301 lifelong residents of an area of malaria holoendemicity in western Kenya for malaria, monitored them during a high-transmission season, and identified 33 individuals who were asymptomatic despite parasitemia (clinically immune). We also identified 50 clinically susceptible individuals to serve as controls. These 83 individuals were treated and monitored again during the subsequent low-transmission season. Anti-EBA-175RII antibodies were present in 98.7% of the individuals studied. The antibody levels were relatively stable between the beginning and end of the high-transmission season and correlated with the plasma EBA-175RII erythrocyte-binding-inhibitory activity. There was no difference in anti-EBA-175RII levels or plasma EBA-175RII erythrocyte-binding-inhibitory activity between clinically immune and clinically susceptible groups. However, these parameters were higher in nonparasitemic than in parasitemic individuals at enrollment. These results suggest that although antibodies against EBA-175RII may be effective in suppressing some of the wild parasite strains, EBA-175RII is unlikely to be effective as a monovalent vaccine against malaria, perhaps due to allelic heterogeneity and/or presence of sialic acid-independent strains.
Host-Inducible Immunogenic Sphingomyelinase-Like Protein, Lk73.5, ofLeptospira interrogans
Authors: Artiushin S. , Timoney J. F. , Nally J. , Verma A. 
Published: January 2004

ABSTRACTLeptospira interroganscauses a variety of clinical syndromes in animals and humans. Although much information has accumulated on the importance of leptospiral lipopolysaccharide in protective antibody responses, relatively little is known about proteins that participate in immune responses. Identification of those proteins induced only in the host is particularly difficult. Using a novel double-antibody screen designed to identify clones in a gene library ofL. interrogansserovar Pomona expressing host-inducible proteins, we have characterized a gene (lk75.3) encoding a sphingomyelinase-like preprotein of 648 amino acids with cytotoxic activity for equine pulmonary endothelial cells and weak hemolytic activity for equine and rabbit erythrocytes.lk73.5was found as a single gene copy in all serovars ofL. interrogansbut not in otherLeptospiraspp. exceptL. inadai. The open reading frame (ORF) for Lk73.5 is followed by another partially homologous sequence containing an ORF (sph-like 2) for a 28.7-kDa peptide. Lk73.5 and Sph-like 2 share 95.1 and 97.7% amino acid identity with putative sphingomyelinases Sph2 and Sph1 (N terminus) fromL. interrogansserovar Lai (S.-X. Ren, G. Fu, X.-G. Jiangk, R. Zeng, Y.-G. Miao, H. Xu, Y.-X. Zhang, H. Xiong, G. Lu, L.-F. Lu, H.-Q. Jiang, J. Jia, Y.-F. Tu, J.-X. Jiang, W.-Y. Gu, Y.-Q. Zhang, Z. Cai, H.-H. Sheng, H.-F. Yin, Y. Zhang, G.-F. Zhu, M. Wank, H.-L. Huangk, Z. Qian, S.-Y. Wang, Wei Ma, Z.-J. Yao, Y. Shen, B.-Q. Qiang, Q.-C. Xia, X.-K. Guo, A. Danchinq, I. S. Girons, R. L. Somerville, Y.-M. Wen, M.-H. Shik, Z. Chen, J.-G. Xuk, and G.-P. Zhao, Nature422:88-893, 2003). Substantial homologies to sphingomyelinases from other leptospiras and other bacteria are also present. Lk73.5 was not detected in leptospiras cultured at 30 or 37°C. The recombinant protein reacted strongly with sera from recently infected mares but not with sera from horses vaccinated with commercial pentavalent bacterin. The host-inducible immunogenic Lk73.5 should have value in distinguishing vaccine from infection immune response.
Immunogenicity against Human Papillomavirus Type 16 Virus-Like Particles Is Strongly Enhanced by the PhoPcPhenotype inSalmonella entericaSerovar Typhimurium
Authors: Baud David , Benyacoub Jalil , Revaz Véronique , Kok Menno , Ponci Françoise , Bobst Martine , Curtiss Roy , De Grandi Pierre , Nardelli-Haefliger Denise 
Published: January 2004

ABSTRACTRecombinantSalmonellastrains have been widely used to deliver heterologous antigens and induce immune responses in vaccinated animals and humans. It remains to be established, however, how these bacteria mount an immune response; this has prevented the rational design of vaccines. Here we report for the first time that a particular genetic program, PhoPc, is necessary for recombinantSalmonellastrains to induce an antibody response to a heterologous antigen, the human papillomaviruses type 16 (HPV16) virus-like particle (VLP). The PhoPcphenotype results from a point mutation inphoQ, the gene encoding the sensor component of a two-component regulatory system (PhoP-PhoQ) that controls the expression of a number of virulence factors in Salmonellae. To demonstrate that immunogenicity of the viral antigen expressed by the bacterial vector was dependent on the PhoPcphenotype, we have expressed thephoQmutant gene (phoQ24) in two differently attenuatedSalmonella entericaserovar Typhimurium strains. Our data show extrachromosomalphoQ24to be dominant over the chromosomal copy of thephoQgene, conferring the PhoPcphenotype on the recipient strains. In addition, activation of PhoPQ-regulated genes by the plasmid-encoded PhoQ24 did not alter bacterial survival and conferred immunogenicity to the HPV16 VLP expressed in the twoS. entericaserovar Typhimurium backgrounds, inducing the production of HPV-specific antibodies in mice. This strongly suggests that at least one of the PhoP-regulated genes is necessary for mounting an efficient antibody response to HPV16 VLP. This finding sets the stage for further development of aSalmonella-based vaccine against HPV infection and cervical cancer.
Acid-Responsive Gene Induction of Ammonia-Producing Enzymes in
Helicobacter pylori
Is Mediated via a Metal-Responsive Repressor Cascade
Authors: van Vliet Arnoud H. M. , Kuipers Ernst J. , Stoof Jeroen , Poppelaars Sophie W. , Kusters Johannes G. 
Published: January 2004

ABSTRACT

Although the adaptive mechanisms allowing the gastric pathogen
Helicobacter pylori
to survive acid shocks have been well documented, the mechanisms allowing growth at mildly acidic conditions (pH ∼5.5) are still poorly understood. Here we demonstrate that
H. pylori
strain 26695 increases the transcription and activity of its urease, amidase, and formamidase enzymes four- to ninefold in response to growth at pH 5.5. Supplementation of growth medium with NiCl
2
resulted in a similar induction of urease activity (at low NiCl
2
concentration) and amidase activity (at ≥500 μM NiCl
2
) but did not affect formamidase activity. Mutation of the
fur
gene, which encodes an iron-responsive repressor of both amidases, resulted in a constitutively high level of amidase and formamidase activity at either pH but did not affect urease activity at pH 7.0 or pH 5.5. In contrast, mutation of the
nikR
gene, encoding the nickel-responsive activator of urease expression, resulted in a significant reduction of acid-responsive induction of amidase and formamidase activity. Finally, acid-responsive repression of
fur
transcription was absent in the
H. pylori nikR
mutant, whereas transcription of the
nikR
gene itself was increased at pH 5.5 in wild-type
H. pylori
. We hypothesize that
H. pylori
uses a repressor cascade to respond to low pH, with NikR initiating the response directly via the urease operon and indirectly via the members of the Fur regulon.
Role ofToll-Like Receptor 4 in Gram-Positive and Gram-Negative Pneumonia inMice
Authors: Branger Judith , Knapp Sylvia , Weijer Sebastiaan , Leemans Jaklien C. , Pater Jennie M. , Speelman Peter , Florquin Sandrine , van der Poll Tom 
Published: January 2004

ABSTRACTTo determine the role of Toll-like receptor 4 (TLR4) in the immune response to pneumonia, C3H/HeJ mice (which display a mutant nonfunctional TLR4) and C3H/HeN wild-type mice were intranasally infected with eitherStreptococcus pneumoniae(a common gram-positive respiratory pathogen) orKlebsiella pneumoniae(a common gram-negative respiratory pathogen). In cases of pneumococcal pneumonia, TLR4 mutant mice showed a reduced survival only after infection with low-level bacterial doses, which was associated with a higher bacterial burden in their lungs 48 h postinfection. InKlebsiellapneumonia, TLR4 mutant mice demonstrated a shortened survival after infection with either a low- or a high-level bacterial dose together with an enhanced bacterial outgrowth in their lungs. These data suggest that TLR4 contributes to a protective immune response in both pneumococcal andKlebsiellapneumonia and that its role is more important in respiratory tract infection caused by the latter (gram-negative) pathogen.
Immunoglobulin E and Eosinophil-Dependent Protective Immunity to LarvalOnchocerca volvulusin Mice Immunized with Irradiated Larvae
Authors: Abraham David , Leon Ofra , Schnyder-Candrian Silvia , Wang Chun Chi , Galioto Ann Marie , Kerepesi Laura A. , Lee James J. , Lustigman Sara 
Published: January 2004

ABSTRACTMice immunized with irradiatedOnchocerca volvulusthird-stage larvae developed protective immunity. Eosinophil levels were elevated in the parasite microenvironment at the time of larval killing, and measurements of total serum antibody levels revealed an increase in the immunoglobulin E (IgE) level in immunized mice. The goal of the present study was to identify the role of granulocytes and antibodies in the protective immune response to the larval stages ofO. volvulusin mice immunized with irradiated larvae. Immunity did not develop in mice if granulocytes, including both neutrophils and eosinophils, were eliminated, nor did it develop if only eosinophils were eliminated. Moreover, larvae were killed in naïve interleukin-5 transgenic mice, and the killing coincided with an increase in the number of eosinophils and the eosinophil peroxidase (EPO) level in the animals. To determine if EPO was required for protective immunity, mice that were genetically deficient in EPO were immunized, and there were no differences in the rates of parasite recovery in EPO-deficient mice and wild-type mice. Two mouse strains were used to study B-cell function; μMT mice lacked all mature B cells, and Xid mice had deficiencies in the B-1 cell population. Immunity did not develop in the μMT mice but did develop in the Xid mice. Finally, protective immunity was abolished in mice treated to eliminate IgE from the blood. We therefore concluded that IgE and eosinophils are required for adaptive protective immunity to larvalO. volvulusin mice.
Host-Pathogen Interaction during Pneumococcal Infection in Patients with Chronic Obstructive Pulmonary Disease
Authors: Bogaert Debby , van der Valk Paul , Ramdin Reshmi , Sluijter Marcel , Monninkhof Evelyn , Hendrix Ron , de Groot Ronald , Hermans Peter W. M. 
Published: January 2004

ABSTRACT

Acute exacerbation is a frequent complication of chronic obstructive pulmonary disease (COPD). Recent studies suggested a role for bacteria such as
Streptococcus pneumoniae
in the development of acute exacerbation. For this study, we investigated the following in COPD patients: (i) the epidemiology of pneumococcal colonization and infection, (ii) the effect of pneumococcal colonization on the development of exacerbation, and (iii) the immunological response against
S. pneumoniae
. We cultured sputa of 269 COPD patients during a stable state and during exacerbation of COPD and characterized 115 pneumococcal isolates by use of serotyping. Moreover, we studied serum immunoglobulin G (IgG) antibody titers, antibody avidities, and functional antibody titers against the seven conjugate vaccine serotypes in these patients. Colonization with only pneumococci (monocultures) increased the risk of exacerbation, with a hazard ratio of 2.93 (95% confidence interval, 1.41 to 6.07). The most prevalent pneumococcal serotypes found were serotypes 19F, 3, 14, 9L/N/V, 23A/B, and 11. We calculated the theoretical coverage for the 7- and 11-valent pneumococcal vaccines to be 60 and 73%, respectively. All patients had detectable IgG levels against the seven conjugate vaccine serotypes. These antibody titers were significantly lower than those in vaccinated healthy adults. Finally, on average, a 2.5-fold rise in serotype-specific and functional antibodies in
S. pneumoniae
-positive sputum cultures was observed during exacerbation. Our data indicate that pneumococcal colonization in COPD patients is frequently caused by vaccine serotype strains. Moreover, pneumococcal colonization is a risk factor for exacerbation of COPD. Finally, our findings demonstrate that COPD patients are able to mount a significant immune response to pneumococcal infection. COPD patients may therefore benefit from pneumococcal vaccination.
Myd88-Dependent In Vivo Maturation of Splenic Dendritic Cells Induced byLeishmania donovaniand Other Leishmania Species
Authors: De Trez Carl , Brait Maryse , Leo Oberdan , Aebischer Tony , Torrentera Fabiola Aguilar , Carlier Yves , Muraille Eric 
Published: January 2004

ABSTRACTThe usual agent of visceral leishmaniasis in the Old World isLeishmania donovani, which typically produces systemic diseases in humans and mice.L. donovanihas developed efficient strategies to infect and persist in macrophages from spleen and liver. Dendritic cells (DC) are sentinels of the immune system. Following recognition of evolutionary conserved microbial products, DC undergo a maturation process and activate antigen-specific naïve T cells. In the present report we provide new insights into how DC detectLeishmaniain vivo. We demonstrate that in both C57BL/6 and BALB/c mice, systemic injection ofL. donovaniinduced the migration of splenic DC from marginal zones to T-cell areas. During migration, DC upregulated the expression of major histocompatibility complex II and costimulatory receptors (such as CD40, CD80, and CD86).Leishmania-induced maturation requires live parasites and is not restricted toL. donovani, asL. braziliensis,L. major, andL. mexicanainduced a similar process. Using a green fluorescent protein-expressing parasite, we demonstrate that DC undergoing maturation in vivo display no parasite internalization. We also show thatL. donovani-induced DC maturation was partially abolished in MyD88-deficient mice. Taken together, our data suggest thatLeishmania-induced DC maturation results from direct recognition ofLeishmaniaby DC, and not from DC infection, and that MyD88-dependent receptors are implicated in this process.
Candida albicansYeast and Germ Tube Forms Interfere Differently with Human Monocyte Differentiation into Dendritic Cells: a Novel Dimorphism-Dependent Mechanism To Escape the Host's Immune Response
Authors: Torosantucci Antonella , Romagnoli Giulia , Chiani Paola , Stringaro Annarita , Crateri Pasqualina , Mariotti Sabrina , Teloni Raffaela , Arancia Giuseppe , Cassone Antonio , Nisini Roberto 
Published: January 2004

ABSTRACTThe ability ofCandida albicansto convert from the yeast (Y) form to mycelial forms through germ tube (GT) formation is considered a key feature of the transition of the organism from commensalism to virulence. We show here that human monocytes cultured with granulocyte-macrophage colony-stimulating factor and interleukin-4 (IL-4) after phagocytosis of Y forms did not differentiate into dendritic cells (DCs); they retained CD14, did not acquire CD1a, and were unable to express the maturation markers CD83 and CCR7. Moreover, they did not produce IL-12p70 but secreted IL-10. In addition, they spontaneously expressed high levels of tumor necrosis factor alpha (TNF-α), IL-6, and IL-8 mRNA transcripts and were able to induce proliferation of alloreactive memory but not naïve T lymphocytes. Conversely, monocytes that had phagocytosed GT forms differentiated into mature CD83+and CCR7+DCs; however, there was no up-regulation of CD40, CD80, and major histocompatibility complex class II, irrespective of lipopolysaccharide (LPS) treatment. In addition, these cells were unable to produce IL-12 even after LPS stimulation, but they were not functionally exhausted, as shown by their capacity to express TNF-α and IL-8 mRNA transcripts. These cells were able to prime naïve T cells but not to induce their functional polarization into effector cells. These data indicate that phagocytosis of Y and GT forms has profound and distinct effects on the differentiation pathway of monocytes. Thus, the differentiation of human monocytes into DCs appears to be tunable and exploitable byC. albicansto elude immune surveillance.
Identification and Cloning of Immunodominant Antigens ofCoxiella burnetii
Authors: Zhang Guoquan , Kiss Katalin , Seshadri Rekha , Hendrix Laura R. , Samuel James E. 
Published: January 2004

ABSTRACTA sublethal-challenge model was established in BALB/c mice by using protection from the development of severe splenomegaly as an indicator of vaccinogenic activity for evaluation of the protective efficacies of vaccine candidates. To determine the immunodominant antigens as defined by reaction to an infection-derived antibody, mouse sera from different stages of experimental infection with various doses ofCoxiella burnetiiwere tested by immunoblotting. Proteins with molecular masses of 14, 16, 21, 28, 32, 45 to 50, 57, and 60 kDa were recognized as immunodominant antigens. Antibody responses in whole-cell antigen (WCA)-vaccinated mice were compared with those in unvaccinated mice by immunoblotting using two-dimensional gel-separatedC. burnetiiantigens. The results indicated that there were significantly different antibody responses during different stages of vaccination and challenge, suggesting that several specific immunogenic antigens may play critical roles in the protection of mice against challenge. To clone these immunogenic antigens, a genomic DNA library of Nine Mile phase I was screened with convalescent-phase antisera from mice. Eighteen novel immunoreactive proteins with molecular masses ranging from ∼14 to 67 kDa were cloned and identified. Interestingly, several recombinant proteins reacted with sera from both early-stage infected and WCA-vaccinated prechallenged mice. These results suggest that these proteins may play critical roles in the development of protective immunity and that they are logical candidates for vaccine and serodiagnostic reagents.