bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interleukin-5 Is Essential for Vaccine-Mediated Immunity but Not Innate Resistance to a Filarial Parasite
Authors: Le Goff Laetitia , Loke P'ng , Ali H. Fahimeda , Taylor David W. , Allen Judith E. 
Published: July 2002

ABSTRACTThe study of protective immune mechanisms effective against filarial nematodes has been hampered by the inability of these important human pathogens to infect laboratory mice. Recently,Litomosoides sigmodontis, a natural parasite of rats, has been developed as a valuable model for the study of filarial infection. BALB/c mice are fully susceptible to infection withL. sigmodontisthird-stage larvae and develop patent infection. In contrast, mice on the C57BL background are resistant, and parasites undergo only a single molt and do not mature to adulthood. We used interleukin-5 (IL-5)-deficient mice on the C57BL/6 background to address the role of IL-5 and eosinophils in the innate resistance of C57BL/6 mice. We found no differences in parasite survival between IL-5-deficient and C57BL/6 mice. However, when these mice were used for the analysis of vaccine-mediated immunity, a critical role for IL-5 was elucidated. Mice genetically deficient in IL-5 were unable to generate a protective immune response when vaccinated with irradiated larvae, whereas C57BL/6 mice were fully protected from challenge infection. These studies help to clarify the highly controversial role of eosinophils in filarial infection.
In Vitro Resistance of
Staphylococcus aureus
to Thrombin-Induced Platelet Microbicidal Protein Is Associated with Alterations in Cytoplasmic Membrane Fluidity
Authors: Bayer Arnold S. , Prasad Rajendra , Chandra Jyotsna , Koul Anjni , Smriti M. , Varma Archana , Skurray Ronald A. , Firth Neville , Brown Melissa H. , Koo Su-Pin , Yeaman Michael R. 
Published: July 2002

ABSTRACT

Platelet microbicidal proteins (PMPs) are small, cationic peptides which possess potent microbicidal activities against common bloodstream pathogens, such as
Staphylococcus aureus
. We previously showed that
S. aureus
strains exhibiting resistance to thrombin-induced PMP (tPMP-1) in vitro have an enhanced capacity to cause human and experimental endocarditis (T. Wu, M. R. Yeaman, and A. S. Bayer, Antimicrob. Agents Chemother. 38:729–732, 1994; A. S. Bayer et al., Antimicrob. Agents Chemother. 42:3169–3172, 1998; V. K. Dhawan et al., Infect. Immun. 65:3293–3299, 1997). However, the mechanisms mediating tPMP-1 resistance in
S. aureus
are not fully delineated. The
S. aureus
cell membrane appears to be a principal target for the action of tPMP-1. To gain insight into the basis of tPMP-1 resistance, we compared several parameters of membrane structure and function in three tPMP-1-resistant (tPMP-1
r
) strains and their genetically related, tPMP-1-susceptible (tPMP-1
s
) counterpart strains. The tPMP-1
r
strains were derived by three distinct methods: transposon mutagenesis, serial passage in the presence of tPMP-1 in vitro, or carriage of a naturally occurring multiresistance plasmid (pSK1). All tPMP-1
r
strains were found to possess elevated levels of longer-chain, unsaturated membrane lipids, in comparison to their tPMP-1
s
counterparts. This was reflected in corresponding differences in cell membrane fluidity in the strain pairs, with tPMP-1
r
strains exhibiting significantly higher degrees of fluidity as assessed by fluorescence polarization. These data provide further support for the concept that specific alterations in the cytoplasmic membrane of
S. aureus
strains are associated with tPMP-1 resistance in vitro.
Synthetic Polysaccharide Type 3-Related Di-, Tri-, and Tetrasaccharide–CRM
197
Conjugates Induce Protection against
Streptococcus pneumoniae
Type 3 in Mice
Authors: Benaissa-Trouw Barry , Lefeber Dirk J. , Kamerling Johannis P. , Vliegenthart Johannes F. G. , Kraaijeveld Kees , Snippe Harm 
Published: July 2002

ABSTRACT

Di-, tri-, and tetrasaccharides, synthesized according to the chemical structure of pneumococcal polysaccharide type 3 (PS3), were coupled to the cross-reactive material (CRM
197
) of modified diphtheria toxin in different molar carbohydrate/protein ratios using the squarate coupling method. To study protective immunity, female BALB/c mice were subcutaneously immunized twice (with a 3-week interval) using the amount of conjugates corresponding to 2.5 μg of oligosaccharide per mouse. The conjugates evoked PS3 binding immunoglobulin G antibodies that lasted for at least 7 weeks after the booster. Immunogenicity was not influenced by the carbohydrate/protein ratio. All mice with PS3-specific antibodies survived the intraperitoneal challenge with
Streptococcus pneumoniae
type 3. Therefore, synthetic oligosaccharide-protein conjugates might have potential as vaccines.
Effect of O Acetylation of
Neisseria meningitidis
Serogroup A Capsular Polysaccharide on Development of Functional Immune Responses
Authors: Berry David S. , Lynn Freyja , Lee Che-Hung , Frasch Carl E. , Bash Margaret C. 
Published: July 2002

ABSTRACT

The importance of O-acetyl groups to the immunogenicity of
Neisseria meningitidis
serogroup A polysaccharide (PS) was examined in studies using human sera and mouse immunization. In 17 of 18 postimmunization human sera, inhibition enzyme-linked immunosorbent assay indicated that the majority of antibodies binding to serogroup A PS were specific for epitopes involving O-acetyl groups. Studies with mice also showed an essential role for O-acetyl groups, where serum bactericidal titers following immunization with de-O-acetylated (de-O-Ac) conjugate vaccine were at least 32-fold lower than those following immunization with O-Ac PS-conjugate vaccine and 4-fold lower than those following immunization with native capsular PS. Inhibition studies using native and de-O-Ac PS confirmed the specificity of murine antibodies to native PS. The dramatic reduction in immunogenicity associated with removal of O-acetyl groups indicates that O acetylation is essential to the immunogenic epitopes of serogroup A PS. Since levels of bactericidal antibodies are correlated with protection against disease, O-acetyl groups appear to be important in protection.
Characterization of a
Bacteroides
Mobilizable Transposon, NBU2, Which Carries a Functional Lincomycin Resistance Gene
Authors: Wang Jun , Shoemaker Nadja B. , Wang Gui-Rong , Salyers Abigail A. 
Published: July 2002

ABSTRACT

The mobilizable
Bacteroides
element NBU2 (11 kbp) was found originally in two
Bacteroides
clinical isolates,
Bacteroides fragilis
ERL and
B. thetaiotaomicron
DOT. At first, NBU2 appeared to be very similar to another mobilizable
Bacteroides
element, NBU1, in a 2.5-kbp internal region, but further examination of the full DNA sequence of NBU2 now reveals that the region of near identity between NBU1 and NBU2 is limited to this small region and that, outside this region, there is little sequence similarity between the two elements. The integrase gene of NBU2,
intN2
, was located at one end of the element. This gene was necessary and sufficient for the integration of NBU2. The integrase of NBU2 has the conserved amino acids (R-H-R-Y) in the C-terminal end that are found in members of the lambda family of site-specific integrases. This was also the only region in which the NBU1 and NBU2 integrases shared any similarity (28% amino acid sequence identity and 49% sequence similarity). Integration of NBU2 was site specific in
Bacteroides
species. Integration occurred in two primary sites in
B. thetaiotaomicron
. Both of these sites were located in the 3′ end of a serine-tRNA gene NBU2 also integrated in
Escherichia coli
, but integration was much less site specific than in
B. thetaiotaomicron
. Analysis of the sequence of NBU2 revealed two potential antibiotic resistance genes. The amino acid sequences of the putative proteins encoded by these genes had similarity to resistances found in gram-positive bacteria. Only one of these genes was expressed in
B. thetaiotaomicron
, the homolog of
linA
, a lincomycin resistance gene from
Staphylococcus aureus
. To determine how widespread elements related to NBU1 and NBU2 are in
Bacteroides
species, we screened 291
Bacteroides
strains. Elements with some sequence similarity to NBU2 and NBU1 were widespread in
Bacteroides
strains, and the presence of

linA
N

in
Bacteroides
strains was highly correlated with the presence of NBU2, suggesting that NBU2 has been responsible for the spread of this gene among
Bacteroides
strains. Our results suggest that the NBU-related elements form a large and heterogeneous family, whose members have similar integration mechanisms but have different target sites and differ in whether they carry resistance genes.
Viability of an
Escherichia coli pgsA
Null Mutant Lacking Detectable Phosphatidylglycerol and Cardiolipin
Authors: Kikuchi Shin , Shibuya Isao , Matsumoto Kouji 
Published: July 2002

ABSTRACT

Phosphatidylglycerol, the most abundant acidic phospholipid in
Escherichia coli
, has been considered to play specific roles in various cellular processes and is believed to be essential for cell viability. It is functionally replaced in some cases by cardiolipin, another abundant acidic phospholipid derived from phosphatidylglycerol. However, we now show that a null
pgsA
mutant is viable, if the major outer membrane lipoprotein is deficient. The
pgsA
gene normally encodes phosphatidylglycerophosphate synthase that catalyzes the committed step in the biosynthesis of these acidic phospholipids. In the mutant, the activity of this enzyme and both phosphatidylglycerol and cardiolipin were not detected (less than 0.01% of total phospholipid, both below the detection limit), although phosphatidic acid, an acidic biosynthetic precursor, accumulated (4.0%). Nonetheless, the null mutant grew almost normally in rich media. In low-osmolarity media and minimal media, however, it could not grow. It did not grow at temperatures over 40°C, explaining the previous inability to construct a null
pgsA
mutant (W. Xia and W. Dowhan, Proc. Natl. Acad. Sci. USA 92:783–787, 1995). Phosphatidylglycerol and cardiolipin are therefore nonessential for cell viability or basic life functions. This notion allows us to formulate a working model that defines the physiological functions of acidic phospholipids in
E. coli
and explains the suppressing effect of lipoprotein deficiency.
Mutational Analysis of Ligand Recognition by Tcp, the Citrate Chemoreceptor of
Salmonella enterica
Serovar Typhimurium
Authors: Iwama Tomonori , Nakao Ko-Ichiro , Nakazato Hiroshi , Yamagata Shuzo , Homma Michio , Kawagishi Ikuro 
Published: July 2002

ABSTRACT
The chemoreceptor Tcp mediates taxis to citrate. To identify citrate-binding residues, we substituted cysteine for seven basic or polar residues that are chosen based on the comparison of Tcp with the well-characterized chemoreceptors. The results suggest that Arg-63, Arg-68, Arg-72, Lys-75, and Tyr-150 (and probably other unidentified residues) are involved in the recognition of citrate.
Identification and Characterization of a Monofunctional Glycosyltransferase from
Staphylococcus aureus
Authors: Wang Q. May , Peery Robert B. , Johnson Robert B. , Alborn William E. , Yeh Wu-Kuang , Skatrud Paul L. 
Published: July 2002

ABSTRACT

A gene (
mgt
) encoding a monofunctional glycosyltransferase (MGT) from
Staphylococcus aureus
has been identified. This first reported gram-positive MGT shared significant homology with several MGTs from gram-negative bacteria and the N-terminal glycosyltransferase domain of class A high-molecular-mass penicillin-binding proteins from different species.
S. aureus
MGT contained an N-terminal hydrophobic domain perhaps involved with membrane association. It was expressed in
Escherichia coli
cells as a truncated protein lacking the hydrophobic domain and purified to homogeneity. Analysis by circular dichroism revealed that secondary structural elements of purified truncated
S. aureus
MGT were consistent with predicted structural elements, indicating that the protein might exhibit the expected folding. In addition, purified
S. aureus
MGT catalyzed incorporation of UDP-
N
-acetylglucosamine into peptidoglycan, proving that it was enzymatically active. MGT activity was inhibited by moenomycin A, and the reaction product was sensitive to lysozyme treatment. Moreover, a protein matching the calculated molecular weight of
S. aureus
MGT was identified from an
S. aureus
cell lysate using antibodies developed against purified MGT. Taken together, our results suggest that this enzyme is natively present in
S. aureus
cells and that it may play a role in bacterial cell wall biosynthesis.
In
Staphylococcus aureus
, Fur Is an Interactive Regulator with PerR, Contributes to Virulence, and Is Necessary for Oxidative Stress Resistance through Positive Regulation of Catalase and Iron Homeostasis
Authors: Horsburgh Malcolm J. , Ingham Eileen , Foster Simon J. 
Published: July 2002

ABSTRACT

The
Staphylococcus aureus
genome encodes three ferric uptake repressor (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of Fur in
S. aureus
, we inactivated the
fur
gene by allelic replacement using a tetracycline resistance cassette, creating strain MJH010 (
fur
). The mutant had a growth defect in rich medium, and this defect was exacerbated in metal-depleted CL medium. This growth defect was partially suppressed by manganous ion, a metal ion with known antioxidant properties. This suggests that the
fur
mutation leads to an oxidative stress condition. Indeed, MJH010 (
fur
) has reduced levels of catalase activity resulting from decreased
katA
transcription. Using a
katA-lacZ
fusion we have determined that Fur functions, either directly or indirectly, as an iron-dependent positive regulator of
katA
expression. Transcription of
katA
is coregulated by Fur and PerR, since in MJH010 (
fur
) transcription was still repressed by manganese while transcription in MJH201 (
fur perR
) was unresponsive to the presence of iron or manganese. Siderophore biosynthesis was repressed by iron in 8325-4 (wild-type) but in MJH010 (
fur
) was constitutive. A number of putative Fur-regulated genes were identified in the incomplete genome databases using known
S. aureus
Fur box sequences. Of those tested, the
sstABCD
and
sirABC
operons and the
fhuD2
and
orf4
genes were found to have Fur-regulated expression. MJH010 (
fur
) was attenuated (
P
< 0.04) in a murine skin abscess model of infection, as was double-mutant MJH201 (
fur perR
) (
P
< 0.03). This demonstrates the importance in vivo of iron homeostasis and oxidative stress resistance regulation in
S. aureus.
New Insight into the Role of the PhaP Phasin of
Ralstonia eutropha
in Promoting Synthesis of Polyhydroxybutyrate
Authors: York Gregory M. , Stubbe JoAnne , Sinskey Anthony J. 
Published: July 2002

ABSTRACT

Phasins are proteins that are proposed to play important roles in polyhydroxyalkanoate synthesis and granule formation. Here the phasin PhaP of
Ralstonia eutropha
has been analyzed with regard to its role in the synthesis of polyhydroxybutyrate (PHB). Purified recombinant PhaP, antibodies against PhaP, and an
R. eutropha phaP
deletion strain have been generated for this analysis. Studies with the
phaP
deletion strain show that PhaP must accumulate to high levels in order to play its normal role in PHB synthesis and that the accumulation of PhaP to low levels is functionally equivalent to the absence of PhaP. PhaP positively affects PHB synthesis under growth conditions which promote production of PHB to low, intermediate, or high levels. The levels of PhaP generally parallel levels of PHB in cells. The results are consistent with models whereby PhaP promotes PHB synthesis by regulating the surface/volume ratio of PHB granules or by interacting with polyhydroxyalkanoate synthase and indicate that PhaP plays an important role in PHB synthesis from the early stages in PHB production and across a range of growth conditions.
Identification of
fur
and
fldA
Homologs and a
Pasteurella multocida tbpA
Homolog in
Histophilus ovis
and Effects of Iron Availability on Their Transcription
Authors: Ekins Andrew , Niven Donald F. 
Published: July 2002

ABSTRACT

tbpA
,
fur
, and
fldA
homologs from two strains (9L and 3384Y) of the sheep pathogen
Histophilus ovis
were sequenced. The predicted TbpA proteins of these strains are homologs of the
Pasteurella multocida
TbpA protein and collectively represent the second example of a new subfamily of TonB-dependent receptors.
tbpA
transcripts were readily detected by reverse transcription (RT)-PCR with RNA isolated from strain 9L grown under iron-restricted conditions in the presence or absence of bovine transferrin (Tf). However, with strain 3384Y and depending on the primer pair,
tbpA
transcripts were detected by RT-PCR predominantly when the RNA was from cells grown under iron-restricted conditions in the presence of bovine Tf. In both strains, the
fldA
homolog was found to be immediately upstream of
fur
and, based on RT-PCR, these genes are transcribed as a single unit; the availability of iron and the presence or absence of bovine Tf in the growth medium had no apparent effect on the relative amounts of the
fldA
-
fur
transcripts.
Ability of Laboratories To Detect Emerging Antimicrobial Resistance: Proficiency Testing and Quality Control Results from the World Health Organization's External Quality Assurance System for Antimicrobial Susceptibility Testing
Authors: Tenover Fred C. , Mohammed M. Jasmine , Stelling John , O'Brien Thomas , Williams Rosamund 
Published: July 2002

ABSTRACT

The accuracy of antimicrobial susceptibility data submitted by microbiology laboratories to national and international surveillance systems has been debated for a number of years. To assess the accuracy of data submitted to the World Health Organization by users of the WHONET software, the Centers for Disease Control and Prevention distributed six bacterial isolates representing key antimicrobial-resistance phenotypes to approximately 130 laboratories, all but one of which were outside of the United States, for antimicrobial susceptibility testing as part of the World Health Organization's External Quality Assurance System for Antimicrobial Susceptibility Testing. Each laboratory also was asked to submit 10 consecutive quality control values for several key organism-drug combinations. Most laboratories were able to detect methicillin (oxacillin) resistance in
Staphylococcus aureus
, high-level vancomycin resistance in
Enterococcus faecium
, and resistance to extended-spectrum cephalosporins in
Klebsiella pneumoniae
. Many laboratories, particularly those using disk diffusion tests, had difficulty in recognizing reduced susceptibility to penicillin in an isolate of
Streptococcus pneumoniae
. The most difficult phenotype for laboratories to detect was reduced susceptibility to vancomycin in an isolate of
Staphylococcus epidermidis
. The proficiency testing challenge also included a request for biochemical identification of a gram-negative bacillus, which most laboratories recognized as
Enterobacter cloacae
. Although only a small subset of laboratories have submitted their quality control data, it is clear that many of these laboratories generate disk diffusion results for oxacillin when testing
S. aureus
ATCC 25923 and
S. pneumoniae
ATCC 49619 that are outside of the acceptable quality control range. The narrow quality control range for vancomycin also proved to be a challenge for many of the laboratories submitting data; approximately 27% of results were out of range. Thus, it is important to establish the proficiency of laboratories submitting data to surveillance systems in which the organisms are tested locally, particularly for penicillin resistance in pneumococci and glycopeptide resistance in staphylococci.
Posttranscriptional Inhibition of Class I Major Histocompatibility Complex Presentation on Hepatocytes and Lymphoid Cells in Chronic Woodchuck Hepatitis Virus Infection
Authors: Michalak Tomasz I. , Hodgson Paul D. , Churchill Norma D. 
Published: July 2002

ABSTRACTWoodchuck hepatitis virus (WHV), similar to human hepatitis B virus, causes acute liver inflammation that can progress to chronic hepatitis and hepatocellular carcinoma. WHV also invades cells of the host lymphatic system, where it persists for life. We report here that acute and chronic hepadnavirus hepatitis is characterized by a profound difference in the expression of class I major histocompatibility complex (MHC) molecules on the surface of infected hepatocytes and, notably, lymphoid cells. While acute WHV infection is accompanied by the enhanced hepatocyte surface presentation of class I MHC antigen and upregulated transcription of the relevant hepatic genes, inhibition of class I antigen display on liver cells is a uniform hallmark of chronic WHV infection. This inhibition in chronic hepatitis occurs despite augmented (as in acute infection) expression of hepatic genes for class I MHC heavy chain, β2-microglobulin, and transporters associated with antigen processing (TAP1 and TAP2). Further, the class I antigen inhibition is not related to the histological severity of hepatocellular injury, the extent of lymphocytic infiltrations, the level of intrahepatic gamma interferon induction, or the hepatic WHV load. Importantly, the antigen expression is also inhibited on organ lymphoid cells of chronically infected hosts. The results obtained in this study demonstrate that the defective presentation of class I MHC molecules on cells supporting persistent WHV replication is due to viral posttranscriptional interference. This event may diminish the susceptibility of infected hepatocytes to virus-specific T-cell-mediated elimination, hinder virus clearance, and deregulate the class I MHC-dependent functions of the host immune system. This multifarious effect could be critical for perpetuation of liver damage and evasion of the antiviral immunological surveillance in chronic infection and therefore could be supportive of hepadnavirus persistence.
The Carboxyl Terminus of v-Abl Protein Can Augment SH2 Domain Function
Authors: Warren David , Heilpern Andrew J. , Berg Kent , Rosenberg Naomi 
Published: July 2002

ABSTRACT
Abelson murine leukemia virus (Ab-MLV) transforms NIH 3T3 and pre-B cells via expression of the v-Abl tyrosine kinase. Although the enzymatic activity of this molecule is absolutely required for transformation, other regions of the protein are also important for this response. Among these are the SH2 domain, involved in phosphotyrosine-dependent protein-protein interactions, and the long carboxyl terminus, which plays an important role in transformation of hematopoietic cells. Important signals are sent from each of these regions, and transformation is most likely orchestrated by the concerted action of these different parts of the protein. To explore this idea, we compared the ability of the v-Src SH2 domain to substitute for that of v-Abl in the full-length P120 v-Abl protein and in P70 v-Abl, a protein that lacks the carboxyl terminus characteristic of Abl family members. Ab-MLV strains expressing P70/S2 failed to transform NIH 3T3 cells and demonstrated a greatly reduced capacity to mediate signaling events associated with the Ras-dependent mitogen-activated protein (MAP) kinase pathway. In contrast, Ab-MLV strains expressing P120/S2 were indistinguishable from P120 with respect to these features. Analyses of additional mutants demonstrated that the last 162 amino acids of the carboxyl terminus were sufficient to restore transformation. These data demonstrate that an SH2 domain with v-Abl substrate specificity is required for NIH 3T3 transformation in the absence of the carboxyl terminus and suggest that cooperativity between the extreme carboxyl terminus and the SH2 domain facilitates the transmission of transforming signals via the MAP kinase pathway.