bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avidity, Potency, and Cross-Reactivity of Monoclonal Antibodies to Pneumococcal Capsular Polysaccharide Serotype 6B
Authors: Sun Yan , Hwang Young-il , Nahm Moon H. 
Published: July 2002

ABSTRACTMany pneumococcal capsular polysaccharides (PSs) are similar in structure, and a pneumococcal antibody often binds to all of the PSs with a similar structure. Yet, these cross-reactive antibodies may bind to the structurally related pneumococcal capsular PSs with an avidity too low to be effective. If memory B cells producing such weakly cross-reactive antibodies are elicited with pneumococcal conjugate vaccines, the memory cells for low-avidity antibodies could compromise the subsequent immune responses to the cross-reactive PS (original antigenic sin). To investigate these issues, we produced 14 hybridomas secreting monoclonal antibodies (MAbs) to the capsular PS ofStreptococcus pneumoniaeserotype 6B by immunizing BALB/c mice with antigens containing 6B PS and studied their epitope, avidity, in vitro opsonizing capacity, in vivo protective capacity, and “antigen binding titer” by enzyme-linked immunosorbent assay (ELISA) of 6A and 6B capsular PSs. Six MAbs bound to the non-cross-reactive 6B-specific epitope, and seven MAbs bound to the cross-reactive epitope present in both 6A and 6B PSs One MAb (Hyp6BM6) revealed a novel epitope. This epitope was found on 6A PS in solution, but not on 6A PS adsorbed onto the plastic surface of the ELISA plates. The avidity of the MAb for 6A or 6B PS ranged from 7.8 × 106M−1to 4.1 × 1011M−1. No MAbs were weakly cross-reactive, since none of the cross-reactive MAbs showed any tendency toward having less avidity to 6A PS (the cross-reactive PS) than to 6B PS. Avidity influenced the results of several antibody assays. When all of the hybridomas were examined, avidity strongly correlated with the titer of a unit amount of MAb to bind antigen-coated ELISA plates (r= 0.91) or to opsonize pneumococci in vitro (r= −0.85). Because both assay results are avidity dependent, the ELISA and the opsonization assay results were strongly correlated (r= 0.91), regardless of avidity. Avidity also correlated with the potency of a MAb to passively protect mice against pneumococcal infections. When only the immunoglobulin G hybridomas were examined, little increase in opsonizing capacity and in vivo protective potency was observed above 109M−1. Taken together, an ELISA measuring antigen binding titer may be an adequate measure of the protective immunity induced with pneumococcal vaccines, and the absence of a partially cross-reactive MAb suggests that antigenic sin may not be significant in responses to vaccines against theS. pneumoniae6B serotype.
Dynamic Changes in Neutrophil Defensins during Endotoxemia
Authors: Klut M. E. , Whalen B. A. , Hogg J. C. 
Published: July 2002

ABSTRACTBacterial endotoxin or lipopolysaccharide (LPS) is an important causative agent of sepsis. This study determines the expression of defensins NP-2 and NP-5 and the function of polymorphonuclear leukocytes (PMN) in rabbits treated with LPS. PMN functional activity was assessed by measuring CD18 expression and H2O2production and by examining the lungs. NP-2 and, to a minor extent, NP-5 of circulating PMN increase during endotoxemia. This early increase is concomitant with neutrophilia and elevated CD18 expression and H2O2production, as well as with enhanced NP-2 immunoreactivity in pulmonary microvessels. A decline in defensins, shortly after the last LPS treatment, is associated with a decrease in the circulating activated PMN and enhanced immunoreactivity in the inflammatory cells, as well as with lung tissue damage. This study shows that LPS-induced changes in the defensins of circulating PMN correlate with the number and activated condition of these cells and suggests that PMN-derived products implement the inflammatory reaction that leads to lung injury and sepsis.
In Vitro and In Vivo Neutralization of the Relapsing Fever AgentBorrelia hermsiiwith Serotype-Specific Immunoglobulin M Antibodies
Authors: Barbour Alan G. , Bundoc Virgilio 
Published: July 2002

ABSTRACTThe antigenic variation of the relapsing fever agentBorrelia hermsiiis associated with changes in the expression of the Vlp and Vsp outer membrane lipoproteins. To investigate whether these serotype-defining proteins are the target of a neutralizing and protective antibody response, monoclonal antibodies were produced from spleens of infected mice just after clearance of serotype 7 cells from the blood. Two immunoglobulin M monoclonal antibodies, H7-7 and H7-12, were studied in detail. Both antibodies specifically agglutinated serotype 7 cells and inhibited their growth in vitro. Administered to mice before or after infection, both antibodies provided protection against infection or substantially reduced the number of spirochetes in the blood of mice after infection. Whereas antibody H7-12 bound to Vlp7 in Western blotting, enzyme-linked immunosorbent assay, and immunoprecipitation assays, as well as to whole cells in other immunoassays, antibody H7-7 only bound to wet, intact cells of serotype 7. Antibody H7-7 selected against cells expressing Vlp7 in vitro and in vivo, an indication that Vlp7 was a conformation-sensitive antigen for the antibody. Vaccination of mice with recombinant Vlp7 with adjuvant elicited antibodies that bound to fixed whole cells of serotype 7 and to Vlp7 in Western blots, but these antibodies did not inhibit the growth of serotype 7 in vitro and did not provide protection against an infectious challenge with serotype 7. The study established that a Vlp protein was the target of a neutralizing antibody response, and it also indicated that the conformation and/or the native topology of Vlp were important for eliciting that immunity.
Down-Regulation of Interleukin-8 Secretion fromMycobacterium tuberculosis-Infected Monocytes by Interleukin-4 and -10 but Not by Interleukin-13
Authors: Ameixa Clara , Friedland Jon S. 
Published: July 2002

ABSTRACTInterleukin-8 (IL-8), a CXC chemokine, has a central role in leukocyte recruitment to areas of granuloma formation in tuberculosis. In the present studies, we investigated the effect of the TH2-derived cytokines IL-4, IL-10, and IL-13 onMycobacterium tuberculosis-induced IL-8 secretion from purified human monocytes. Our results demonstrate that IL-4 and IL-10 have a down-regulatory effect on IL-8 secretion and that this effect is dose dependent. IL-10 has a greater effect than IL-4 on secretion, and autologous IL-10 secreted fromM. tuberculosis-infected monocytes also down-regulates IL-8 secretion. The down-regulatory effect is partly a result of reduced IL-8 mRNA accumulation analyzed by reverse transcription-PCR. When combined, 1 μM IL-4 and IL-10 had an additive effect in decreasing IL-8 secretion and transcription; there was no synergy of action. IL-13 did not have any significant effect on IL-8 gene expression or secretion. The inhibitory effect of IL-10 but not of IL-4 is associated with decreased nuclear binding of the key activating transcription factor NF-κB. We show for the first time thatM. tuberculosiscauses up-regulation of nuclear binding of Oct-1 detected by electromobility gel shift assay. However, neither AP-1 nor Oct-1 nuclear binding was altered by IL-4 or IL-10. In summary, this study demonstrates that type 2 responses have an important role in the regulation ofM. tuberculosis-induced IL-8 expression but that the mechanisms by which the different cytokines act are distinct.
Gut Colonization of Mice withactA-Negative Mutant ofListeria monocytogenesCan Stimulate a Humoral Mucosal Immune Response
Authors: Manohar Muniraj , Baumann Donald O. , Bos Nicolaas A. , Cebra John J. 
Published: July 2002

ABSTRACTWe usedListeria monocytogenes, a gram-positive, facultative intracellular bacterium, to study the gut mucosal immune responses following oral infection. We employed a germfree (GF) mouse model to try to accentuate the development of a humoral mucosal immune response in the gut, and we used oral colonization with one of the mutants,actA-negative (ΔactA)L. monocytogenes, to restrict infection largely to the gut. The ΔactAmutant was able to colonize the intestinal mucosa of formerly GF mice for long periods of time without causing disease while eliciting secretory immunoglobulin A (IgA) responses, as evidenced by gut tissue fragment culture assays. Flow cytometric analyses and immunohistochemical methods showed the development of only minimal germinal center reactions (GCR) in Peyer's patches and more robust GCR in mesenteric lymph nodes. Pronounced increases in total (natural) IgA production occurred in gut tissues by day 7 and were maintained for up to 90 days. Levels of specific IgA were modest in gut tissues on day 14, increased until day 76, and stabilized at day 90. We also observed a significant rise in serum IgA and IgG1 levels following oral infection by listeriae. Upon colonization, the organisms mainly infected the intestines and intestinal lumen, and we only sporadically observed few colony-forming bacteria in the liver and spleen. We observed a marked rise in IgA-secreting cells, including listeria-specific IgA antibody-secreting cells, in the lamina propria of the small intestine by enzyme-linked immunospot assays. To ascertain whether some of the IgA was specific for listeriae, we performed Western blot analysis to test the reactivity of IgA from fragment cultures to antigens in sonicates ofL. monocytogenes. We detected IgA binding to antigenic proteins with molecular masses of 96, 60, 40, and 14 kDa in theListeriasonicates.
Identification of
Listeria monocytogenes
In Vivo-Induced Genes by Fluorescence-Activated Cell Sorting
Authors: Wilson Rebecca L. , Tvinnereim A. R. , Jones Bradley D. , Harty John T. 
Published: July 2002

ABSTRACT

Listeria monocytogenes
is a gram-positive, intracellular, food-borne pathogen capable of causing severe infections in immunocompromised or pregnant individuals, as well as numerous animal species. Genetic analysis of
Listeria
pathogenesis has identified several genes which are crucial for virulence. The transcription of most of these genes has been shown to be induced upon entry of
Listeria
into the host cell. To identify additional genes that are induced in vivo and may be required for
L. monocytogenes
pathogenesis, a fluorescence-activated cell-sorting technique was initiated. Random fragments of the
L. monocytogenes
chromosome were cloned into a plasmid carrying a promoterless green fluorescent protein (GFP) gene, and the plasmids were transformed into the
L. monocytogenes actA
mutant DP-L1942. Fluorescence-activated cell sorting (FACS) was used to isolate
L. monocytogenes
clones that exhibited increased GFP expression within macrophage-like J774 cells but had relatively low levels of GFP expression when the bacteria were extracellular. Using this strategy, several genes were identified, including
actA
, that exhibited such an expression profile. In-frame deletions of two of these genes, one encoding the putative
L. monocytogenes
uracil DNA glycosylase (
ung
) and one encoding a protein with homology to the
Bacillus subtilis
YhdP hemolysin-like protein, were constructed and introduced into the chromosome of wild-type
L. monocytogenes
10403s. The
L. monocytogenes
10403s
ung
deletion mutant was not attenuated for virulence in mice, while the
yhdP
mutant exhibited a three- to sevenfold reduction in virulence.
In Vivo Activation of Dendritic Cells and T Cells duringSalmonella entericaSerovar Typhimurium Infection
Authors: Yrlid Ulf , Svensson Mattias , Håkansson Anders , Chambers Benedict J. , Ljunggren Hans-Gustaf , Wick Mary Jo 
Published: July 2002

ABSTRACTThe present study was initiated to gain insight into the interaction between splenic dendritic cells (DC) andSalmonella entericaserovar Typhimurium in vivo. Splenic phagocytic cell populations associated with green fluorescent protein (GFP)-expressing bacteria and the bacterium-specific T-cell response were evaluated in mice givenS. entericaserovar Typhimurium expressing GFP and ovalbumin. Flow cytometry analysis revealed that GFP-positive splenic DC (CD11c+major histocompatibility complex class II-positive [MHC-II+] cells) were present following bacterial administration, and confocal microscopy showed that GFP-expressing bacteria were contained within CD11c+MHC-II+splenocytes. Furthermore, splenic DC and T cells were activated followingSalmonellainfection. This was shown by increased surface expression of CD86 and CD40 on CD11c+MHC-II+cells and increased CD44 and CD69 expression on CD4+and CD8+T cells.Salmonella-specific gamma interferon (IFN-γ)-producing cells in both of these T-cell subsets, as well as cytolytic effector cells, were also generated in mice given live bacteria. The frequency ofSalmonella-specific CD4+T cells producing IFN-γ was greater than that of specific CD8+T cells producing IFN-γ in the same infected animal. This supports the argument that the predominant source of IFN-γ production by cells of the specific immune response is CD4+T cells. Finally, DC that phagocytosed live or heat-killedSalmonellain vitro primed bacterium-specific IFN-γ-producing CD4+and CD8+T cells as well as cytolytic effector cells following administration into naı̈ve mice. Together these data suggest that DC are involved in priming naı̈ve T cells toSalmonellain vivo.
Discrete Protein Determinant Directs the Species-Specific Adherence of
Porphyromonas gingivalis
to Oral Streptococci
Authors: Demuth Donald R. , Irvine Douglas C. , Costerton J. W. , Cook Guy S. , Lamont Richard J. 
Published: July 2002

ABSTRACT

For pathogens to survive in the human oral cavity, they must identify a suitable niche in the complex multispecies biofilm that exists on oral tissues. The periodontal pathogen
Porphyromonas gingivalis
adheres to
Streptococcus gordonii
by interacting with a specific region of the streptococcal SspB polypeptide, designated BAR. However, it does not adhere to
Streptococcus mutans,
which expresses SpaP, a highly conserved homolog of SspB. Comparison of the predicted secondary structure of BAR with the corresponding region of SpaP suggested that the substitution of Asn for Gly
1182
and Val for Pro
1185
in SspB may confer a unique local structure that is not conserved in SpaP. A synthetic peptide of 26 amino acids that encompassed residues 1167 to 1193 of SspB promoted avid adherence of
P. gingivalis
, whereas a peptide derived from the region corresponding to BAR in SpaP was inactive. Substitution of Gly
1182
and Pro
1185
for Asn
1182
and Val
1185
in SspB by site-specific mutation generated proteins that were predicted to assume an SpaP-like secondary structure, and the purified proteins did not promote
P. gingivalis
adherence. Furthermore,
Enterococcus faecalis
strains expressing the site-specific mutants did not support adherence of
P. gingivalis
cells. In contrast,
P. gingivalis
adhered efficiently to
E. faecalis
strains expressing intact SspB or SspB-SpaP chimeric proteins containing BAR. These results suggest that a region of SspB consisting of 26 amino acids is sufficient to mediate the adherence of
P. gingivalis
to
S. gordonii
and that the species specificity of adherence arises from its interaction with a discrete structural determinant of SspB that is not conserved in SpaP.
dksA
Is Required for Intercellular Spread of
Shigella flexneri
via an RpoS-Independent Mechanism
Authors: Mogull Scott A. , Runyen-Janecky Laura J. , Hong Mei , Payne Shelley M. 
Published: July 2002

ABSTRACT

Pathogenesis of
Shigella flexneri
is dependent on the ability of the bacterium to invade and spread within epithelial cells. In this study, we identified
dksA
as a gene necessary for intercellular spread in, but not invasion of, cultured cells. The
S. flexneri dksA
mutant exhibited sensitivity to acid and oxidative stress, in part due to an effect of DksA on production of RpoS. However, an
S. flexneri rpoS
mutant formed plaques on tissue culture monolayers, thus excluding DksA regulation of RpoS as the mechanism responsible for the inability of the
dksA
mutant to spread intercellularly. Intracellular analysis of the
dksA
mutant indicates that it survived and divided within the Henle cell cytoplasm, but the
dksA
mutant cells were elongated, and some exhibited filamentation in the intracellular environment. Some of the
S. flexneri dksA
mutant cells showed aberrant localization of virulence protein IcsA, which may inhibit spread between epithelial cells.
Effects ofMycobacterium bovisBCG Infection on Regulation ofl-Arginine Uptake and Synthesis of Reactive Nitrogen Intermediates in J774.1 Murine Macrophages
Authors: Peteroy-Kelly Marcy , Venketaraman Vishwanath , Connell Nancy D. 
Published: July 2002

ABSTRACTThe generation of nitric oxide (NO) by activated macrophages is believed to control mycobacterial infection in the murine system. In this study we examined the effect ofMycobacterium bovisBCG infection on thel-arginine-dependent NO pathway in J774.1 murine macrophages. We have confirmed previous results by demonstrating that stimulation of J774.1 with lipopolysaccharide (LPS) and gamma interferon (IFN-γ) results in an increase in the uptake of3H-labeledl-arginine and a concomitant increase in the production of NO. We have also shown that BCG can mimic LPS treatment, leading to enhancedl-[3H]arginine uptake by IFN-γ-stimulated macrophages. Lipoarabinomannan, a component of the BCG cell wall that is structurally similar to LPS, is not responsible for the uptake stimulation in IFN-γ stimulated macrophages. Although we demonstrated that there was a 2.5-fold increase in NO production by macrophages 4 h after LPS–IFN-γ stimulation, BCG infection (with or without IFN-γ stimulation) did not lead to the production of NO by the macrophages by 4 h postinfection. At 24 h postinfection, the infected macrophages that were stimulated with IFN-γ produced amounts of NO similar to those of macrophages stimulated with LPS–IFN-γ. This suggests that there are multiple regulatory pathways involved in the production of NO. Finally, our data suggest that increased expression of the arginine permease, MCAT2B, after 4 h of LPS–IFN-γ treatment or BCG infection–IFN-γ treatment is not sufficient to account for the increases inl-[3H]arginine uptake detected. This suggests that the activity of thel-arginine transporter(s) is also altered in response to macrophage activation.
Analysis of Factors Affecting Surface Expression and Immunogenicity of Recombinant Proteins Expressed by Gram-Positive Commensal Vectors
Authors: Bolken Tové C. , Franke Christine A. , Jones Kevin F. , Bell Richard H. , Swanson Ryan M. , King David S. , Fischetti Vincent A. , Hruby Dennis E. 
Published: July 2002

ABSTRACT

Several key protein structural attributes were altered in an effort to optimize expression and immunogenicity of a foreign protein (M protein from
Streptococcus pyogenes
) exposed on the surface of
Streptococcus gordonii
commensal bacterial vectors: (i) a shorter N-terminal region, (ii) the addition of a 94-amino-acid spacer, and (iii) the addition of extra C-repeat regions (CRR) from the M6 protein. A decrease in the amount of cell surface M6 was observed upon deletion of 10 or more amino acid residues at the N terminus. On the other hand, reactivity of monoclonal antibody to surface M6 increased with the addition of the spacer adjacent to the proline- and glycine-rich region, and an increase in epitope dosage was obtained by adding another CRR immediately downstream of the original CRR. The results obtained should facilitate the design of improved vaccine candidates using this antigen delivery technology.
Demonstration of a Novel Glycolytic Pathway in the Hyperthermophilic Archaeon
Thermococcus zilligii
by
13
C-Labeling Experiments and Nuclear Magnetic Resonance Analysis
Authors: Xavier Karina B. , da Costa Milton S. , Santos Helena 
Published: July 2002

ABSTRACT

The operation of a novel glycolytic pathway was demonstrated in nongrowing cells of
Thermococcus zilligii
by analysis of the isotopic enrichment in the end products derived from fermentation of
13
C-labeled glucose. The new pathway involved the formation of formate, derived from C-1 in glucose, via cleavage of a six-carbon carboxylic acid.
Flavonoid-Induced Expression of a Symbiosis-Related Gene in the Cyanobacterium
Nostoc punctiforme
Authors: Cohen Michael F. , Yamasaki Hideo 
Published: July 2002

ABSTRACT

The flavonoid naringin was found to induce the expression of
hrmA
, a gene with a symbiotic phenotype in the cyanobacterium
Nostoc punctiforme
. A comparative analysis of several flavonoids revealed the 7-
O
-neohesperidoside, 4′-OH, and C-2-C-3 double bond in naringin as structural determinants of its
hrmA
-inducing activity.
Cell-Associated Pheromone Peptide (cCF10) Production and Pheromone Inhibition in
Enterococcus faecalis
Authors: Buttaro B. A. (Leonard) , Antiporta M. H. , Dunny G. M. 
Published: July 2002

ABSTRACT

In
Enterococcus faecalis
, the peptide cCF10 acts as a pheromone, inducing transfer of the conjugative plasmid pCF10 from plasmid-containing donor cells to plasmid-free recipient cells. In these studies, it was found that a substantial amount of cCF10 associates with the envelope of the producing cell. Pheromone activity was detected in both wall and membrane fractions, with the highest activity associated with the wall. Experiments examining the effects of protease inhibitor treatments either prior to or following cell fractionation suggested the presence of a cell envelope-associated pro-cCF10 that can be processed to mature cCF10 by a maturase or protease. A pCF10-encoded membrane protein, PrgY, was shown to prevent self-induction of donor cells by reducing the level of pheromone activity in the cell wall fraction.
Bacillus subtilis comZ
(
yjzA
) Negatively Affects Expression of
comG
but Not
comK
Authors: Ogura Mitsuo , Tanaka Teruo 
Published: July 2002

ABSTRACT

The
yjzA
open reading frame, along with
med
, constitutes an operon. Disruption of
yjzA
caused a five-fold enhancement of
comG
expression, thereby leading to a three-fold-higher transformation efficiency. The expression of
comK
and the other three late competence operons was not affected significantly in the
yjzA
-deficient mutant.