bluuebunny/crossref_metadata_2025 huggingface dataset:
Assortative Mating as a Mechanism for Rapid Evolution of a Migratory Divide
Authors: Bearhop Stuart , Fiedler Wolfgang , Furness Robert W. , Votier Stephen C. , Waldron Susan , Newton Jason , Bowen Gabriel J. , Berthold Peter , Farnsworth Keith
Published: October 2005

There have been numerous recent observations of changes in the behavior and dynamics of migratory bird populations, but the plasticity of the migratory trait and our inability to track small animals over large distances have hindered investigation of the mechanisms behind migratory change. We used habitat-specific stable isotope signatures to show that recently evolved allopatric wintering populations of European blackcaps
Sylvia atricapilla
pair assortatively on their sympatric breeding grounds. Birds wintering further north also produce larger clutches and fledge more young. These findings describe an important process in the evolution of migratory divides, new migration routes, and wintering quarters. Temporal segregation of breeding is a way in which subpopulations of vertebrates may become isolated in sympatry.
Species Loss and Aboveground Carbon Storage in a Tropical Forest
Authors: Bunker Daniel E. , DeClerck Fabrice , Bradford Jason C. , Colwell Robert K. , Perfecto Ivette , Phillips Oliver L. , Sankaran Mahesh , Naeem Shahid
Published: October 2005

Tropical forest biodiversity is declining, but the resulting effects on key ecosystem services, such as carbon storage and sequestration, remain unknown. We assessed the influence of the loss of tropical tree species on carbon storage by simulating 18 possible extinction scenarios within a well-studied 50-hectare tropical forest plot in Panama, which contains 227 tree species. Among extinction scenarios, aboveground carbon stocks varied by more than 600%, and biological insurance varied by more than 400%. These results indicate that future carbon storage in tropical forests will be influenced strongly by future species composition.
The Onset of Planet Formation in Brown Dwarf Disks
Authors: Apai Dániel , Pascucci Ilaria , Bouwman Jeroen , Natta Antonella , Henning Thomas , Dullemond Cornelis P.
Published: October 2005

The onset of planet formation in protoplanetary disks is marked by the growth and crystallization of sub–micrometer-sized dust grains accompanied by dust settling toward the disk mid-plane. Here, we present infrared spectra of disks around brown dwarfs and brown dwarf candidates. We show that all three processes occur in such cool disks in a way similar or identical to that in disks around low- and intermediate-mass stars. These results indicate that the onset of planet formation extends to disks around brown dwarfs, suggesting that planet formation is a robust process occurring in most young circumstellar disks.
Reciprocal Interference Between Specific CJD and Scrapie Agents in Neural Cell Cultures
Authors: Nishida Noriuki , Katamine Shigeru , Manuelidis Laura
Published: October 2005

Infection of mice with an attenuated Creutzfeldt-Jakob disease agent (SY-CJD) interferes with superinfection by a more virulent human-derived CJD agent (FU-CJD) and does not require pathological prion protein (PrPres). Using a rapid coculture system, we found that a neural cell line free of immune system cells similarly supported substantial CJD agent interference without PrPres. In addition, SY-CJD prevented superinfection by sheep-derived Chandler (Ch) and 22L scrapie agents. However, only 22L and not Ch prevented FU-CJD infection, even though both scrapie strains provoked abundant PrPres. This relationship between particular strains of sheep- and human-derived agents is likely to affect their prevalence and epidemic spread.
LIN-12/Notch Activation Leads to MicroRNA-Mediated Down-Regulation of Vav in
C. elegans
Authors: Yoo Andrew S. , Greenwald Iva
Published: October 2005

Cell-cell interactions and cross-talk between signaling pathways specify
Caenorhabditis elegans
vulval precursor cells (VPCs) to adopt a spatial pattern: a central “1°” VPC, in which epidermal growth factor receptor (EGFR)–mitogen-activated protein kinase (MAPK) activity is high and LIN-12/Notch activity is low, flanked by two “2°” VPCs, in which LIN-12/Notch activity is high and EGFR-MAPK activity is low. Here, we identify a microRNA gene,
mir-61
, as a direct transcriptional target of LIN-12 and show that expression of
mir-61
promotes the 2° fate. We also identify
vav-1
, the ortholog of the Vav oncogene, as a target of
mir-61
, and show that down-regulation of VAV-1 promotes
lin-12
activity in specifying the 2° fate. Our results suggest that
lin-12, mir-61
, and
vav-1
form a feedback loop that helps maximize
lin-12
activity in the presumptive 2° VPCs.
Antibiotic Abscess Penetration: Fosfomycin Levels Measured in Pus and Simulated Concentration-Time Profiles
Authors: Sauermann Robert , Karch Rudolf , Langenberger Herbert , Kettenbach Joachim , Mayer-Helm Bernhard , Petsch Martina , Wagner Claudia , Sautner Thomas , Gattringer Rainer , Karanikas Georgios , Joukhadar Christian
Published: October 2005

The present study was performed to evaluate the ability of fosfomycin, a broad-spectrum antibiotic, to penetrate into abscess fluid. Twelve patients scheduled for surgical or computer tomography-guided abscess drainage received a single intravenous dose of 8 g of fosfomycin. The fosfomycin concentrations in plasma over time and in pus upon drainage were determined. A pharmacokinetic model was developed to estimate the concentration-time profile of fosfomycin in pus. Individual fosfomycin concentrations in abscess fluid at drainage varied substantially, ranging from below the limit of detection up to 168 mg/liter. The fosfomycin concentrations in pus of the study population correlated neither with plasma levels nor with the individual ratios of abscess surface area to volume. This finding was attributed to highly variable abscess permeability. The average concentration in pus was calculated to be 182 ± 64 mg/liter at steady state, exceeding the MIC50/90s of several bacterial species which are commonly involved in abscess formation, such as streptococci, staphylococci, andEscherichia coli. Hereby, the exceptionally long mean half-life of fosfomycin of 32 ± 39 h in abscess fluid may favor its antimicrobial effect because fosfomycin exerts time-dependent killing. After an initial loading dose of 10 to 12 g, fosfomycin should be administered at doses of 8 g three times per day to reach sufficient concentrations in abscess fluid and plasma. Applying this dosing regimen, fosfomycin levels in abscess fluid are expected to be effective after multiple doses in most patients.
Fitness Cost Due to Mutations in the 16S rRNA Associated with Spectinomycin Resistance in
Chlamydia psittaci
6BC
Authors: Binet Rachel , Maurelli Anthony T.
Published: October 2005

The fitness cost of a resistance determinant is the primary parameter that determines its frequency in vivo. As a model for analysis of the impact of drug resistance mutations on the intracellular life cycle of
Chlamydia
spp., we studied the growth of four genetically defined spectinomycin-resistant (Spc
r
) clonal variants of
Chlamydia psittaci
6BC isolated in the plaque assay. The development of each variant was monitored over 46 h postinfection in the absence of drug, either in pure culture or in 1:1 competition with the parent strain. Spc
r
mutations in the 16S rRNA gene at positions 1191 and 1193 were associated with a marked impairment of
C.psittaci
biological fitness, and the bacteria were severely outcompeted by the wild-type parent. In contrast, mutations at position 1192 had minor effects on the bacterial life cycle, allowing the resistant isolates to compete more efficiently with the wild-type strain. Thus, mutations with a wide range of fitness costs can be selected in the plaque assay, providing a new strategy for prediction and monitoring of the emergence of antibiotic resistance in chlamydiae. So far, drug resistance has not been a serious threat for the treatment of chlamydial infections. Tetracycline is an effective antichlamydial drug that targets 16S rRNA. Attempts to isolate spontaneous tetracycline-resistant mutants of
C. psittaci
6BC revealed a frequency <3 × 10
−9
. We suggest that the rarity of genotypic antibiotic resistance among chlamydial clinical isolates reflects the deleterious effects of such mutations on the fitness of these obligate intracellular bacteria in the host.
Novel Acquired Metallo-β-Lactamase Gene,blaSIM-1, in a Class 1 Integron fromAcinetobacter baumanniiClinical Isolates from Korea
Authors: Lee Kyungwon , Yum Jong Hwa , Yong Dongeun , Lee Hyuk Min , Kim Heung Dong , Docquier Jean-Denis , Rossolini Gian Maria , Chong Yunsop
Published: October 2005

Carbapenem resistance mediated by acquired carbapenemase genes has been increasingly reported, particularly for clinical isolates ofPseudomonas aeruginosaandAcinetobacterspp. Of 1,234 nonduplicate isolates of carbapenem-resistantPseudomonasspp. andAcinetobacterspp. isolated at a tertiary-care hospital in Seoul, Korea, 211 (17%) were positive for metallo-β-lactamase (MBL). Of these, 204 (96%) had either theblaIMP-1orblaVIM-2allele. In addition, sevenAcinetobacter baumanniiisolates were found to have a novel MBL gene, which was designatedblaSIM-1. The SIM-1 protein has a pI of 7.2, is a new member of subclass B1, and exhibits 64 to 69% identity with the IMP-type MBLs, which are its closest relatives. All SIM-1-producing isolates exhibited relatively low imipenem and meropenem MICs (8 to 16 μg/ml) and had a multidrug resistance phenotype. Expression of the clonedblaSIM-1gene inEscherichia colirevealed that the encoded enzyme is capable of hydrolyzing a broad array of β-lactams, including penicillins, narrow- to expanded-spectrum cephalosporins, and carbapenems. TheblaSIM-1gene was carried on a gene cassette inserted into a class 1 integron, which included three additional cassettes (arr-3,catB3, andaadA1). The strains were isolated from sputum and urine specimens from patients with pneumonia and urinary tract infections, respectively. All patients had various underlying diseases. Pulsed-field gel electrophoresis of SmaI-digested genomic DNAs showed that the strains belonged to two different clonal lineages, indicating that horizontal transfer of this gene had occurred and suggesting the possibility of further spread of resistance in the future.
Randomized, Placebo-Controlled Trial of Nonpegylated and Pegylated Forms of Recombinant Human Alpha Interferon 2a for Suppression of Dengue Virus Viremia in Rhesus Monkeys
Authors: Ajariyakhajorn C. , Mammen M. P. , Endy T. P. , Gettayacamin M. , Nisalak A. , Nimmannitya S. , Libraty D. H.
Published: October 2005

Dengue fever and dengue hemorrhagic fever are caused by infection with any one of the four dengue viruses (DVs) and are significant public health burdens throughout the tropics. Higher viremia levels are associated with greater dengue disease severity. A therapeutic intervention to suppress viremia early in DV infection could potentially ameliorate severe disease. Recombinant alpha interferon 2a (rIFN-α-2a, Roferon-A) suppressed DV replication in human peripheral blood mononuclear cells in vitro. We therefore examined the effects of rIFN-α-2a and pegylated recombinant IFN-α-2a (PEG-rIFN-α-2a, PEGASYS) on DV serotype 2 (DV-2) viremia in rhesus monkeys. Flavivirus-naïve monkeys were inoculated with DV-2 and randomized to receive a single dose of rIFN-α-2a (10 million international units/m2) versus placebo or PEG-rIFN-α-2a (6 μg/kg) versus placebo 1 day after the onset of viremia. Serial daily viremia levels were measured, and convalescent-phase DV-2 neutralizing antibody titers were determined. Compared to placebo, a single injection of rIFN-α-2a temporarily suppressed DV-2 replication and delayed the time to peak viremia by a median of 3 days. However, measures of total viral burden were not different between the two groups. A single injection of PEG-rIFN-α-2a significantly lowered daily viremia levels and improved virus clearance, starting 48 h after administration. There were no significant differences in DV-2 neutralizing antibody titers between the treatment and placebo groups at 30 and 90 days postinfection. Based on their individual effects, future studies should investigate a combination of rIFN-α-2a and PEG-rIFN-α-2a for suppression of dengue virus viremia and as a potential therapeutic intervention.
Use of Ribotyping To Retrospectively Identify Methicillin-Resistant
Staphylococcus aureus
Isolates from Phase 3 Clinical Trials for Tigecycline That Are Genotypically Related to Community-Associated Isolates
Authors: McAleese Fionnuala , Murphy Ellen , Babinchak Timothy , Singh Guy , Said-Salim Battouli , Kreiswirth Barry , Dunman Paul , O'Connell John , Projan Steven J. , Bradford Patricia A.
Published: October 2005

A retrospective study was performed to identify methicillin-resistant
Staphylococcus aureus
(MRSA) isolates obtained from patients enrolled in phase 3 clinical trials for tigecycline that were genotypically similar to known community-associated MRSA (CA-MRSA) strains. The clinical trials were double-blind comparator studies for complicated skin and skin structure infections or complicated intra-abdominal infections. We obtained 85% of the MRSA isolates from patients with complicated skin and skin structure infections. Using ribotyping, MRSA isolates were compared with well-characterized North American CA-MRSA strains and negative-control hospital-associated (HA) MRSA strains by cluster analysis; 91 of the 173 isolates clustered with two groups of known CA-MRSA strains, 60% of which shared an indistinguishable ribotype. These isolates were subsequently tested for the presence of SCC
mec
type IV and the Panton-Valentine leukocidin (PVL)-encoding genes as well as susceptibility to clindamycin, characteristics that are typically associated with CA-MRSA; 89 of the 91 isolates carried the type IV SCC
mec
element and 76 were also positive for the PVL-encoding genes; 73 of these isolates were susceptible to clindamycin. A similar analysis performed on 26 nonclustering isolates identified only four with these characteristics; 89 of the 91 clustering isolates were inhibited by tigecycline at MICs of ≤0.5 μg/ml. On the basis of clustering information and preliminary genetic characterization, it appears that ribotyping is a useful tool in identifying potential CA-MRSA isolates and 76 MRSA isolates from patients enrolled in the tigecycline phase 3 trials have genetic markers typically associated with CA-MRSA.
Gene Expression Analysis of the Mechanism of Natural Sb(V) Resistance in
Leishmania donovani
Isolates from Nepal
Authors: Decuypere Saskia , Rijal Suman , Yardley Vanessa , De Doncker Simonne , Laurent Thierry , Khanal Basudha , Chappuis François , Dujardin Jean-Claude
Published: October 2005

Control of visceral leishmaniasis (VL) is being challenged by the emergence of natural resistance against the first line of treatment, pentavalent antimonials [Sb(V)]. An insight into the mechanism of natural Sb(V) resistance is required for the development of efficient strategies to monitor the emergence and spreading of Sb(V) resistance in countries where VL is endemic. In this work, we have focused on the mechanism of natural Sb(V) resistance emerging in Nepal, a site where anthroponotic VL is endemic. Based on the current knowledge of Sb(V) metabolism and of the in vitro trivalent antimonial [Sb(III)] models of resistance to
Leishmania
spp., we selected nine genes for a comparative transcriptomic study on natural Sb(V)-resistant and -sensitive
Leishmania donovani
isolates. Differential gene expression patterns were observed for the genes coding for 2-thiol biosynthetic enzymes, gamma-glutamylcysteine synthetase (GCS) and ornithine decarboxylase (ODC), and for the Sb(III) transport protein aquaglyceroporin 1 (AQP1). The results indicate that the mechanism for natural Sb(V) resistance partially differs from the mechanism reported for in vitro Sb(III) resistance. More specifically, we hypothesize that natural Sb(V) resistance results from (i) a changed thiol metabolism, possibly resulting in inhibition of Sb(V) activation in amastigotes, and (ii) decreased uptake of the active drug Sb(III) by amastigotes.
Inhibitory Activities of Epidermal Growth Factor Receptor Tyrosine Kinase-Targeted Dihydroxyisoflavone and Trihydroxydeoxybenzoin Derivatives on
Sarcocystis neurona
,
Neospora caninum
, and
Cryptosporidium parvum
Development
Authors: Gargala G. , Baishanbo A. , Favennec L. , François A. , Ballet J. J. , Rossignol J.-F.
Published: October 2005

Several gene sequences of parasitic protozoa belonging to protein kinase gene families and epidermal growth factor (EGF)-like peptides, which act via binding to receptor tyrosine kinases of the EGF receptor (EGFR) family, appear to mediate host-protozoan interactions. As a clue to EGFR protein tyrosine kinase (PTK) mediation and a novel approach for identifying anticoccidial agents, activities against
Sarcocystis neurona
,
Neospora caninum
, and
Cryptosporidium parvum
grown in BM and HCT-8 cell cultures of 52 EGFR PTK inhibitor isoflavone analogs (dihydroxyisoflavone and trihydroxydeoxybenzoine derivatives) were investigated. Their cytotoxicities against host cells were either absent, mild, or moderate by a nitroblue tetrazolium test. At concentrations ranging from 5 to 10 μg/ml, 20 and 5 analogs, including RM-6427 and RM-6428, exhibited an in vitro inhibitory effect of ≥95% against at least one parasite or against all three, respectively. In immunosuppressed
Cryptosporidium parvum
-infected Mongolian gerbils orally treated with either 200 or 400 mg of agent RM-6427/kg of body weight/day for 8 days, fecal microscopic oocyst shedding was abolished in 6/10 animals (
P
of <0.001 versus untreated controls) and mean shedding was reduced by 90.5% (
P
of <0.0001) and 92.0% (
P
of <0.0001), respectively, higher levels of inhibition than after nitazoxanide (200 mg/kg/day for 8 days) or paromomycin (100 mg/kg/day for 8 days) treatment (55.0%,
P
of <0.001, and 17.5%,
P
of >0.05, respectively). After RM-6427 therapy (200 mg/kg/day for 8 days), the reduction in the ratio of animals with intracellular parasites was nearly significant in ileum (
P
= 0.067) and more marked in the biliary tract (
P
< 0.0013) than after nitazoxanide or paromomycin treatment (0.05 <
P
< 0.004). RM-6428 treatment at a regimen of 400 mg/kg/day for 12 days inhibited oocyst shedding, measured using flow cytometry from day 4 (
P
 < 0.05) to day 12 (
P
< 0.02) of therapy, when 2/15 animals had no shedding (
P
< 0.0001) and 11/15 were free of gut and/or biliary tract parasites (
P
< 0.01). No mucosal alteration was microscopically observed for treated or untreated infected gerbils. To our knowledge, this report is the first to suggest that the isoflavone class of agents has the potential for anticoccidial therapy.
Horizontal Transfer of Iturin A Operon,
itu
, to
Bacillus subtilis
168 and Conversion into an Iturin A Producer
Authors: Tsuge Kenji , Inoue Satoka , Ano Takashi , Itaya Mitsuhiro , Shoda Makoto
Published: October 2005

Iturin A and its derivatives are lipopeptide antibiotics produced by
Bacillus subtilis
and several closely related bacteria. Three
iturin group operons (i.e., iturin A, mycosubtilin, and bacillomycin D) of those antibiotic-producing strains have been cloned and sequenced
thus far, strongly implying the horizontal transfer of these operons. To examine the nature of such horizontal transfer in terms of antibiotic production, a 42-kb region of the
B. subtilis
RB14 genome, which contains a complete 38-kb iturin A operon, was
transferred via competent cell transformation to the genome of a non-iturin A producer,
B. subtilis
168, using a method based on double-crossover homologous recombination with two short landing pad sequences (LPSs) in the genome. The recombinant was positively selected
by confirming the elimination of the
c
I repressor gene, which was localized between the two LPSs and substituted by the transferred
segment. The iturin A operon-transferred strain 168 was then converted into an iturin A producer by the introduction of an
sfp
gene,
which encodes 4′-phosphopantetheinyl transferase and is mutated in strain 168. By inserting the pleiotropic regulator
degQ
, the productivity of iturin A increased sevenfold and was restored to about half that of the donor strain RB14, without the transfer of
additional genes, such as regulatory or self-resistance genes.
Safety and Efficacy of Tigecycline in Treatment of Skin and Skin Structure Infections: Results of a Double-Blind Phase 3 Comparison Study with Vancomycin-Aztreonam
Authors: Breedt Johannes , Teras Jüri , Gardovskis Janis , Maritz Frans Jacobus , Vaasna Tiit , Ross Douglas Patrick , Gioud-Paquet Martine , Dartois Nathalie , Ellis-Grosse Evelyn J. , Loh Evan
Published: October 2005

In a randomized, double-blind, controlled trial, 546 patients with complicated skin and skin structure infections received tigecycline 100 mg/day (a 100-mg initial dose and then 50 mg intravenously twice daily) or the combination of vancomycin 2 g/day (1 g intravenously twice daily) and aztreonam 4 g/day (2 g intravenously twice daily) for up to 14 days. The primary end point was the clinical response in the clinical modified intent-to-treat (c-mITT) and clinically evaluable (CE) populations at the test-of-cure visit 12 to 92 days after the last dose. The microbiologic response at the test-of-cure visit was also assessed. Safety was assessed by physical examination, laboratory results, and adverse event reporting. Five hundred twenty patients were included in the c-mITT population (tigecycline group,n= 261; combination group,n= 259), and 436 were clinically evaluable (tigecycline group,n= 223; combination group,n= 213). The clinical responses in the tigecycline and the combination vancomycin and aztreonam groups were similar in the c-mITT population (84.3% versus 86.9%; difference, −2.6% [95% confidence interval, −9.0, 3.8];P= 0.4755) and the CE population (89.7% versus 94.4%; difference, −4.7% [95% confidence interval, −10.2, 0.8];P= 0.1015). Microbiologic eradication (documented or presumed) occurred in 84.8% of the patients receiving tigecycline and 93.2% of the patients receiving vancomycin and aztreonam (difference, −8.5 [95% confidence interval, −16.0, −1.0];P= 0.0243). The numbers of patients reporting adverse events were similar in the two groups, with increased nausea and vomiting rates in the tigecycline group and an increased incidence of rash and increases in alanine aminotransferase and aspartate aminotransferase levels in the combination vancomycin and aztreonam group. Tigecycline was shown to be safe and effective for the treatment of complicated skin and skin structure infections.
Combination Therapy with Terbinafine and Amphotericin B in a Rabbit Model of Experimental Invasive Aspergillosis
Authors: Kirkpatrick William R. , Vallor Ana C. , McAtee Robert K. , Ryder Neil S. , Fothergill Annette W. , Rinaldi Michael G. , Patterson Thomas F.
Published: October 2005

Antagonistic effects of combination therapy using amphotericin B (AmB) with agents which block ergosterol synthesis are a concern. Terbinafine was evaluated with AmB to assess antagonism or synergy in a rabbit model of invasive aspergillosis. Terbinafine had relatively little activity but did not demonstrate antagonism against AmB in our model.
TLA-2, a Novel Ambler Class A Expanded-Spectrum β-Lactamase
Authors: Girlich Delphine , Poirel Laurent , Schlüter Andreas , Nordmann Patrice
Published: October 2005

β-Lactamase TLA-2 is encoded by a 47-kb plasmid isolated from an unidentified bacterial strain from a wastewater treatment plant. TLA-2 is an Ambler class A β-lactamase that shares 52% amino acid identity with CGA-1 from
Chryseobacterium gleum
and 51% with TLA-1 from
Escherichia coli
. The enzyme hydrolyzes mostly cephalosporins.
mmpL7
Gene of
Mycobacterium tuberculosis
Is Responsible for Isoniazid Efflux in
Mycobacterium smegmatis
Authors: Pasca Maria R. , Guglierame Paola , De Rossi Edda , Zara Francesca , Riccardi Giovanna
Published: October 2005

The
Mycobacterium tuberculosis mmpL7
gene, encoding a hypothetical resistance nodulation division transporter, confers a high resistance level to isoniazid when overexpressed in
Mycobacterium smegmatis
. The resistance level decreased in the presence of the efflux pump inhibitors reserpine and CCCP (carbonyl cyanide
m
-chlorophenylhydrazone). Energy-dependent efflux of isoniazid from
M. smegmatis
cells expressing the
mmpL7
gene was observed.
Analysis of the Contribution of
Salmonella
Pathogenicity Islands 1 and 2 to Enteric Disease Progression Using a Novel Bovine Ileal Loop Model and a Murine Model of Infectious Enterocolitis
Authors: Coombes Brian K. , Coburn Bryan A. , Potter Andrew A. , Gomis Susantha , Mirakhur Kuldip , Li Yuling , Finlay B. Brett
Published: October 2005

We have developed a novel ileal loop model for use in calves to analyze the contribution of
Salmonella enterica
serovar Typhimurium type III secretion systems to disease processes in vivo. Our model involves constructing ileal loops with end-to-end anastamoses to restore the patency of the small intestine, thereby allowing experimental animals to convalesce following surgery for the desired number of days. This model overcomes the time constraint imposed by ligated ileal loop models that have precluded investigation of
Salmonella
virulence factors during later stages of the infection process. Here, we have used this model to examine the enteric disease process at 24 h and 5 days following infection with wild-type
Salmonella
and mutants lacking the virulence-associated
Salmonella
pathogenicity island 1 (SPI-1) or SPI-2 type III secretion systems. We show that SPI-2 mutants are dramatically attenuated at 5 days following infection and report a new phenotype for SPI-1 mutants, which induce intestinal pathology in calves similar to wild-type
Salmonella
in the 5-day ileal loop model. Both of these temporal phenotypes for SPI-1 and SPI-2 mutants were corroborated in a second animal model of enteric disease using streptomycin-pretreated mice. These data delineate novel phenotypes for SPI-1 and SPI-2 mutants in the intestinal phase of bovine and murine salmonellosis and provide working models to further investigate the effector contribution to these pathologies.
Distinct CD4+-T-Cell Responses to Live and Heat-InactivatedAspergillus fumigatusConidia
Authors: Rivera Amariliz , Van Epps Heather L. , Hohl Tobias M. , Rizzuto Gabrielle , Pamer Eric G.
Published: October 2005

Aspergillus fumigatusis an important fungal pathogen that causes invasive pulmonary disease in immunocompromised hosts. Respiratory exposure toA. fumigatusspores also causes allergic bronchopulmonary aspergillosis, a Th2 CD4+-T-cell-mediated disease that accompanies asthma. The microbial factors that influence the differentiation ofA. fumigatus-specific CD4+T lymphocytes into Th1 versus Th2 cells remain incompletely defined. We therefore examined CD4+-T-cell responses of immunologically intact mice to intratracheal challenge with live or heat-inactivatedA. fumigatusspores. Live but not heat-inactivated fungal spores resulted in recruitment of gamma interferon (IFN-γ)-producing, fungus-specific CD4+T cells to lung airways, achievingA. fumigatus-specific frequencies exceeding 5% of total CD4+T cells. While heat-inactivated spores did not induce detectable levels of IFN-γ-producing,A. fumigatus-specific CD4+T cells in the airways, they did prime CD4+T-cell responses in draining lymph nodes that produced greater amounts of interleukin 4 (IL-4) and IL-13 than T cells responding to live conidia. While immunization with live fungal spores induced antibody responses, we found a marked decrease in isotype-switched,A. fumigatus-specific antibodies in sera of mice following immunization with heat-inactivated spores. Our studies demonstrate that robust Th1 T-cell and humoral responses are restricted to challenge with fungal spores that have the potential to germinate and cause invasive infection. How the adaptive immune system distinguishes between metabolically active and inactive fungal spores remains an important question.
Merozoite Surface Antigen 2 Proteins of
Babesia bovis
Vaccine Breakthrough Isolates Contain a Unique Hypervariable Region Composed of Degenerate Repeats
Authors: Berens Shawn J. , Brayton Kelly A. , Molloy John B. , Bock Russell E. , Lew Ala E. , McElwain Terry F.
Published: October 2005

The merozoite surface antigen 2 (MSA-2) proteins of
Babesia bovis
are members of the variable merozoite surface antigen (VMSA) family that have been implicated in erythrocyte invasion and are important targets for antibody-mediated blocking of invasion. Extensive sequence variation in another VMSA member, MSA-1, has been shown in all vaccine breakthrough isolates. To test the hypothesis that the
msa-2
genes of vaccine breakthrough isolates would also encode a diverse set of proteins, the complete
msa-2
locus was characterized from 12 Australian
B. bovis
strains and isolates, including two vaccine strains and eight vaccine breakthrough isolates, and compared to the loci in previously and newly characterized American strains. In contrast to American strains, the
msa-2
loci of all Australian strains and isolates examined contain, in addition to
msa-2c
, only a solitary gene (designated
msa-2a/b
) closely related to American strain
msa-2a
and
msa-2b
. Nevertheless, the proteins encoded by these genes are quite diverse both between and within geographic regions and harbor evidence of genetic exchange among other VMSA family members, including
msa-1
. Moreover, all but one of the Australian breakthrough isolate MSA-2a/b proteins is markedly different from the vaccine strain from which immune escape occurred, consistent with their role in strain-specific protective immunity. The densest distribution of polymorphisms occurs in a hypervariable region (HVR) within the carboxy third of the molecule that is highly proline rich. Variation in length and content of the HVR is primarily attributable to differences in the order and number of degenerate nucleotide repeats encoding three motifs of unknown function.
Hemagglutinin B Is Involved in the Adherence of
Porphyromonas gingivalis
to Human Coronary Artery Endothelial Cells
Authors: Song Hong , Bélanger Myriam , Whitlock Joan , Kozarov Emil , Progulske-Fox Ann
Published: October 2005

Porphyromonas gingivalis
is a periodontopathogen that may play a role in cardiovascular diseases. Hemagglutinins may function as adhesins and are required for virulence of several bacterial pathogens. The aim of this study was to determine the role of hemagglutinin B (HagB) in adherence of
P. gingivalis
to human coronary artery endothelial (HCAE) cells.
P. gingivalis
strain 381, a
P. gingivalis
381 HagB mutant,
Escherichia coli
JM109 expressing HagB (
E. coli
-HagB), and
E. coli
JM109 containing pUC9 (
E. coli
-pUC9) were tested for their ability to attach to HCAE cells. Inhibition assays were performed to determine the ability of purified recombinant HagB (rHagB) as well as antibodies to HagB, including the polyclonal antibody (PAb) A7985 and the monoclonal antibody (MAb) HL1858, to inhibit the attachment of
P. gingivalis
to HCAE cells. As expected, when the attachment of
P. gingivalis
and the HagB mutant were compared, no statistical significance was observed between the two groups (
P
= 0.331), likely due to the expression of the
hagB
homolog
hagC
. However,
E. coli-
HagB adhered significantly better to HCAE cells than did
E. coli-
pUC9, the control strain. In a competition assay, the presence of purified rHagB decreased bacterial adhesion of
P. gingivalis
or
E. coli-
HagB to HCAE cells. The presence of PAb A7985 or MAb HL1858 also significantly decreased attachment of
P. gingivalis
and
E. coli-
HagB to host cells. These results indicate that HagB is involved in the adherence of
P. gingivalis
to human primary endothelial cells.
Cell-Mediated Protection against PulmonaryYersinia pestisInfection
Authors: Parent Michelle A. , Berggren Kiera N. , Kummer Lawrence W. , Wilhelm Lindsey B. , Szaba Frank M. , Mullarky Isis K. , Smiley Stephen T.
Published: October 2005

Pulmonary infection with the bacteriumYersinia pestiscauses pneumonic plague, an often-fatal disease for which no vaccine is presently available. Antibody-mediated humoral immunity can protect mice against pulmonaryY. pestisinfection, an experimental model of pneumonic plague. Little is known about the protective efficacy of cellular immunity. We investigated the cellular immune response toY. pestisin B-cell-deficient μMT mice, which lack the capacity to generate antibody responses. To effectively prime pulmonary cellular immunity, we intranasally vaccinated μMT mice with live replicatingY. pestis. Vaccination dramatically increased survival of μMT mice challenged intranasally with a lethalY. pestisdose and significantly reduced bacterial growth in pulmonary, splenic, and hepatic tissues. Vaccination also increased numbers of pulmonary T cells, and administration of T-cell-depleting monoclonal antibodies at the time of challenge abrogated vaccine-induced survival. Moreover, the transfer ofY. pestis-primed T cells to naive μMT mice protected against lethal intranasal challenge. These findings establish that vaccine-primed cellular immunity can protect against pulmonaryY. pestisinfection and suggest that vaccines promoting both humoral and cellular immunity will most effectively combat pneumonic plague.
Blood Group, Immunity, and Risk of Infection withVibrio choleraein an Area of Endemicity
Authors: Harris Jason B. , Khan Ashraful I. , LaRocque Regina C. , Dorer David J. , Chowdhury Fahima , Faruque Abu S. G. , Sack David A. , Ryan Edward T. , Qadri Firdausi , Calderwood Stephen B.
Published: October 2005

Individuals with blood group O are more susceptible than other individuals to severe cholera, although the mechanism underlying this association is unknown. To assess the respective roles of both intrinsic host factors and adaptive immune responses that might influence susceptibility to infection withVibrio cholerae, we prospectively followed a cohort of household contacts of patients with cholera in Bangladesh. In this study, we made the novel observation that persons with blood group O were less likely than those with other blood groups to become infected withV. choleraeO1 (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.53 to 0.85;P= 0.008). Consistent with prior studies, however, household contacts with blood group O were more likely to develop severe illness if infected withV. choleraeO1 (OR, 2.3; 95% CI, 0.98 to 5.59;P= 0.05). While blood group O protected significantly against infection withV. choleraeO1, there was no evidence of protection againstV. choleraeO139. A multivariate analysis demonstrated that the association between blood group O and protection from infection withV. choleraeO1 was independent of age, gender, and baseline anti-cholera toxin and vibriocidal antibody titers. Based on this epidemiologic evidence, we propose a hypothesis for understanding the association between blood group O and the risk of infection withV. choleraeO1 and O139 as well as the risk of developing severe symptoms once infected.
CD28 Is Required for Optimal Induction, but Not Maintenance, of Vaccine-Induced Immunity toBlastomyces dermatitidis
Authors: Wüthrich Marcel , Warner Tom , Klein Bruce S.
Published: October 2005

Cellular immunity mediated by T lymphocytes, in particular CD4+and CD8+type 1 cells, is the main defense against pathogenic fungi. Here, CD28-deficient (CD28−/−) mice were used to study the role of costimulation for the generation and maintenance of T-cell-mediated, type 1 cytokine-dependent mechanisms of vaccine immunity toBlastomyces dermatitidisinfection. Disruption of CD28 costimulation reduced the number of type 1 CD4 and CD8 cells generated and impaired resistance to infection. Type 1 T-cell subsets generated in vaccinated CD28−/−mice were durable and protected mice for at least 3 months after vaccination. Our findings suggest that CD28 is required for the induction of optimal, protective T-cell responses toB. dermatitidisinfection but may be dispensable for the maintenance of T-cell memory.
Loss of Complement Activation and Leukocyte Adherence asNippostrongylus brasiliensisDevelops within the Murine Host
Authors: Giacomin Paul R. , Wang Hui , Gordon David L. , Botto Marina , Dent Lindsay A.
Published: October 2005

Complement activation and C3 deposition on the surface of parasitic helminths may be important for recruitment of leukocytes and for damage to the target organism via cell-mediated mechanisms. Inhibition of complement activation would therefore be advantageous to parasites, minimizing damage and enhancing migration through tissues. The aim of this study was to determine ex vivo if complement activation by, and leukocyte adherence to, the nematodeNippostrongylus brasiliensischange as the parasite matures and migrates through the murine host. Pathways of activation of complement and the mechanism of adherence of leukocytes were also defined using sera from mice genetically deficient in either C1q, factor B, C1q and factor B, C3, or C4. Substantive deposition of C3 and adherence of eosinophil-rich leukocytes were seen with infective-stage (L3) but not with lung-stage (L4) larvae. Adult intestinal worms had low to intermediate levels of both C3 and leukocyte binding. For L3 and adult worms, complement deposition was principally dependent on the alternative pathway. For lung-stage larvae, the small amount of C3 detected was dependent to similar degrees on both the lectin and alternative pathways. The classical pathway was not involved for any of the life stages of the parasite. These results suggest that in primary infections, the infective stage ofN. brasiliensisis vulnerable to complement-dependent attack by leukocytes. However, within the first 24 h of infection,N. brasiliensisacquires the ability to largely avoid complement-dependent immune responses.
Differential Cytokine Production and Toll-Like Receptor Signaling Pathways by
Candida albicans
Blastoconidia and Hyphae
Authors: van der Graaf Chantal A. A. , Netea Mihai G. , Verschueren Ineke , van der Meer Jos W. M. , Kullberg Bart Jan
Published: October 2005

Toll-like receptors (TLR) are crucial for an efficient antifungal defense. We investigated the differential recognition of blastoconidia and hyphae of
Candida albicans
by TLRs. In contrast to
Candida
blastoconidia, which stimulated large amounts of gamma interferon (IFN-γ), the tissue-invasive
Candida
hyphae did not stimulate any IFN-γ by human peripheral blood mononuclear cells (PBMC) or murine splenic lymphocytes. After stimulation with blastoconidia, the production of IFN-γ was TLR4 dependent, as shown by the significantly decreased IFN-γ production in anti-TLR4-treated PBMC and in splenic lymphocytes from TLR4-defective ScCr mice. In addition, peritoneal macrophages from ScCr mice produced less tumor necrosis factor α (TNF-α) than macrophages of control mice did when stimulated with
Candida
blastoconidia, but not with hyphae, indicating that TLR4-mediated signals are lost during hyphal germination. In contrast, macrophages from TLR2 knockout mice had a decreased production of TNF-α in response to both
Candida
blastoconidia and hyphae.
Candida
hyphae stimulated production of interleukin-10 through TLR2-dependent mechanisms. In conclusion, TLR4 mediates proinflammatory cytokine induction after
Candida
stimulation, whereas
Candida
recognition by TLR2 leads mainly to anti-inflammatory cytokine release. TLR4-mediated proinflammatory signals are lost during germination of
Candida
blastoconidia into hyphae. Phenotypic switching during germination may be an important escape mechanism of
C. albicans
, resulting in counteracting host defense.
MyD88-Dependent Signaling Contributes to Protection following
Bacillus anthracis
Spore Challenge of Mice: Implications for Toll-Like Receptor Signaling
Authors: Hughes Molly A. , Green Candace S. , Lowchyj Lisa , Lee Gloria M. , Grippe Vanessa K. , Smith Michael F. , Huang Li-Yun , Harvill Eric T. , Merkel Tod J.
Published: October 2005

Bacillus anthracis
is a spore-forming, gram-positive organism that is the causative agent of the disease anthrax. Recognition of
Bacillus anthracis
by the host innate immune system likely plays a key protective role following infection. In the present study, we examined the role of TLR2, TLR4, and MyD88 in the response to
B. anthracis.
Heat-killed
Bacillus anthracis
stimulated TLR2, but not TLR4, signaling in HEK293 cells and stimulated tumor necrosis factor alpha (TNF-α) production in C3H/HeN, C3H/HeJ, and C57BL/6J bone marrow-derived macrophages. The ability of heat-killed
B. anthracis
to induce a TNF-α response was preserved in TLR2
−/−
but not in MyD88
−/−
macrophages. In vivo studies revealed that TLR2
−/−
mice and TLR4-deficient mice were resistant to challenge with aerosolized Sterne strain spores but MyD88
−/−
mice were as susceptible as A/J mice. We conclude that, although recognition of
B. anthracis
occurs via TLR2, additional MyD88-dependent pathways contribute to the host innate immune response to anthrax infection.
Comparison of Immune Responses to Gonococcal PorB Delivered as Outer Membrane Vesicles, Recombinant Protein, or Venezuelan Equine Encephalitis Virus Replicon Particles
Authors: Zhu Weiyan , Thomas Christopher E. , Chen Ching-ju , Van Dam Cornelius N. , Johnston Robert E. , Davis Nancy L. , Sparling P. Frederick
Published: October 2005

Porin (PorB) is a major outer membrane protein produced by allNeisseria gonorrhoeaestrains and has been a focus of intense interest as a vaccine candidate. In this study, the immunogenicity of PorB in mice was investigated after several immunization regimens. Outer membrane vesicles (OMV), recombinant renatured PorB (rrPorB), and PorB-expressing Venezuelan equine encephalitis (VEE) virus replicon particles (PorB VRP) were delivered intranasally (i.n.) or subcutaneously (s.c.) into the dorsal area or the hind footpad in three-dose schedules; the PorB VRP-immunized mice were given a single additional booster dose of rrPorB in Ribi adjuvant. Different delivery systems and administration routes induced different immune responses. Mice immunized s.c. with rrPorB in Ribi had the highest levels of PorB-specific serum immunoglobulin G (IgG) by enzyme-linked immunosorbent assay. Surprisingly, there was an apparent Th1 bias, based on IgG1/IgG2a ratios, after immunization with rrPorB in Ribi in the footpad while the same vaccine given in the dorsal area gave a strongly Th2-biased response. PorB VRP-immunized mice produced a consistent Th1 response with a high gamma interferon response in stimulated splenic lymphocytes and very low IgG1/IgG2a ratios. Immunization by OMV delivered i.n. was the only regimen that resulted in a serum bactericidal response, and it generated an excellent mucosal IgA response. Serum from mice immunized with rrPorB preferentially recognized the surface of whole gonococci expressing a homologous PorB, whereas serum from PorB VRP-immunized mice had relatively low whole-cell binding activity but recognized both heterologous and homologous PorB equally. The data resulting from this direct comparison suggested that important aspects of the immune response can be manipulated by altering the form of the antigen and its delivery. This information coupled with an understanding of protective antigonococcal immune responses will enable the design of the optimal vaccine forN. gonorrhoeae.
Additive Effect on Intracellular Growth byLegionella pneumophilaIcm/Dot Proteins Containing a Lipobox Motif
Authors: Yerushalmi Gal , Zusman Tal , Segal Gil
Published: October 2005

Legionella pneumophila, the causative agent of Legionnaires' disease, utilizes a type IVB secretion system to subvert its host cells and grow intracellularly. This type IV secretion system is composed of 25icm(ordot) genes that probably constitute parts of a secretion complex as well as more than 30 proteins that are translocated via this system into the host cells. Three of the Icm/Dot proteins (DotD, DotC, and IcmN) contain a lipobox motif at their N terminals and are predicted to be lipoproteins. Two of these lipoproteins (DotD and DotC) were found to be essential for intracellular growth in both HL-60-derived human macrophages and in the protozoan hostAcanthamoeba castellanii, while the third lipoprotein (IcmN) was found to be partially required for intracellular growth only inA. castellanii. Mutation analysis of the lipobox cysteine residue, which was shown previously to be indispensable for the lipobox function, indicated that both DotC and DotD are partially functional without this conserved residue. Cysteine mutations in both DotC and DotD or in DotC together with anicmNdeletion or in DotD together with anicmNdeletion were found to be additive, indicating that each of these lipoproteins performs its function independently from the others. Analysis of the transcriptional regulation of both thedotDCoperon and theicmNgene revealed that both had higher levels of expression at stationary phase which were partially dependent on the LetA regulator. Our results indicate that the lipoproteins of theL. pneumophila icm(ordot) system are essential components of the secretion system and that they perform their functions independently.
Variations inHelicobacter pyloriLipopolysaccharide To Evade the Innate Immune Component Surfactant Protein D
Authors: Khamri Wafa , Moran Anthony P. , Worku Mulugeta L. , Karim Q. Najma , Walker Marjorie M. , Annuk Heidi , Ferris John A. , Appelmelk Ben J. , Eggleton Paul , Reid Kenneth B. M. , Thursz Mark R.
Published: October 2005

Helicobacter pyloriis a common and persistent human pathogen of the gastric mucosa. Surfactant protein D (SP-D), a component of innate immunity, is expressed in the human gastric mucosa and is capable of aggregatingH. pylori. Wide variation in the SP-D binding affinity toH. pylorihas been observed in clinical isolates and laboratory-adapted strains. The aim of this study was to reveal potential mechanisms responsible for evading SP-D binding and establishing persistent infection. An escape variant, J178V, was generated in vitro, and the lipopolysaccharide (LPS) structure of the variant was compared to that of the parental strain, J178. The genetic basis for structural variation was explored by sequencing LPS biosynthesis genes. SP-D binding to clinical isolates was demonstrated by fluorescence-activated cell sorter analyses. Here, we show thatH. pylorievades SP-D binding through phase variation in lipopolysaccharide. This phenomenon is linked to changes in the fucosylation of the O chain, which was concomitant with slipped-strand mispairing in a poly(C) tract of the fucosyltransferase A (fucT1) gene. SP-D binding organisms are predominant in mucus in vivo (P= 0.02), suggesting that SP-D facilitates physical elimination. Phase variation to evade SP-D contributes to the persistence of this common gastric pathogen.
Vaginal Epithelial Cell Anti-
Candida albicans
Activity Is Associated with Protection against Symptomatic Vaginal Candidiasis
Authors: Barousse Melissa M. , Espinosa Terri , Dunlap Kathleen , Fidel Paul L.
Published: October 2005

Vaginal epithelial cell (VEC) anti-
Candida albicans
activity, despite being measured in vitro, is considered an innate host defense mechanism. This was supported further by the fact that women protected from symptomatic infection following a live intravaginal
Candida
challenge had increased VEC anti-
Candida
activity compared to those who acquired a symptomatic infection.