bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Prevalence of Human Antibodies to Recombinant Duffy Binding-Like α Domains of the
Plasmodium falciparum
-Infected Erythrocyte Membrane Protein 1 in Semi-Immune Adults Compared to That in Nonimmune Children
Authors: Oguariri Raphael M. , Borrmann Steffen , Klinkert Mo-Quen , Kremsner Peter G. , Kun Jürgen F. J. 
Published: July 2002

ABSTRACT

We used a panel of nine fusion proteins that contain different Duffy binding-like α (DBL-α) domains of
Plasmodium falciparum
-infected erythrocyte membrane protein 1 to assess the levels of antibody activity in serum samples obtained from semi-immune or nonimmune individuals from Lambaréné, Gabon. Recognition was measured in terms of either the prevalence or the magnitude of the response. A strong correlation between the immune status of the patients and reactivity with recombinant proteins was observed, which was interpreted as a reflection of the number of infections acquired over time. The antibody responses were predominantly directed toward variable epitopes of the DBL-α domain. Antibody responses could be reduced by preincubation of the sera with various fusion proteins. A portion of individuals who exhibited high-level responses to all fusion proteins also had antibodies which recognized conserved epitopes. The possibility that a synergizing effect of anti-DBL-α domain antibodies could support chemotherapy is discussed.
Antibodies to Loop 6 of the P2 Porin Protein of Nontypeable
Haemophilus influenzae
Are Bactericidal against Multiple Strains
Authors: Neary John M. , Yi Kyungcheol , Karalus Richard J. , Murphy Timothy F. 
Published: July 2002

ABSTRACT

The P2 porin protein is the most abundant protein in the outer membrane of nontypeable
Haemophilus influenzae
(NTHI). Analysis of sequences of P2 from different strains reveals the presence of both heterogeneous and conserved surface-exposed loops of the P2 molecule among strains. The present study was undertaken to test the hypothesis that antibodies to a conserved surface-exposed loop are bactericidal for multiple strains of NTHI and could thus form the basis of vaccines to prevent infection due to NTHI. Polyclonal antiserum to a peptide corresponding to loop 6 was raised and was immunopurified over a loop 6 peptide column. Analysis of the antibodies to whole organisms and peptides corresponding to each of the eight loops of P2 by immunoassays revealed that the antibodies were highly specific for loop 6 of P2. The immunopurified antibodies bound to P2 of 14 of 15 strains in immunoblot assays. These antibodies to loop 6 demonstrated complement-mediated bactericidal killing of 8 of 15 strains. These results support the concept of using conserved regions of the P2 protein as a vaccine antigen.
Cell Vacuolation Caused by
Vibrio cholerae
Hemolysin
Authors: Figueroa-Arredondo Paula , Heuser John E. , Akopyants Natalia S. , Morisaki J. Hiroshi , Giono-Cerezo Silvia , Enrı́quez-Rincón Fernando , Berg Douglas E. 
Published: July 2002

ABSTRACT

Non-O1 strains of
Vibrio cholerae
implicated in gastroenteritis and diarrhea generally lack virulence determinants such as cholera toxin that are characteristic of epidemic strains; the factors that contribute to their virulence are not understood. Here we report that at least one-third of diarrhea-associated nonepidemic
V. cholerae
strains from Mexico cause vacuolation of cultured Vero cells. Detailed analyses indicated that this vacuolation was related to that caused by aerolysin, a pore-forming toxin of
Aeromonas
; it involved primarily the endoplasmic reticulum at early times (∼1 to 4 h after exposure), and resulted in formation of large, acidic, endosome-like multivesicular vacuoles (probably autophagosomes) only at late times (∼16 h). In contrast to vacuolation caused by
Helicobacter pylori
VacA protein, that induced by
V. cholerae
was exacerbated by agents that block vacuolar proton pumping but not by endosome-targeted weak bases. It caused centripetal redistribution of endosomes, reflecting cytoplasmic alkalinization. The gene for
V. cholerae
vacuolating activity was cloned and was found to correspond to
hlyA
, the structural gene for hemolysin. HlyA protein is a pore-forming toxin that causes ion leakage and, ultimately, eukaryotic cell lysis. Thus, a distinct form of cell vacuolation precedes cytolysis at low doses of hemolysin. We propose that this vacuolation, in itself, contributes to the virulence of
V. cholerae
strains, perhaps by perturbing intracellular membrane trafficking or ion exchange in target cells and thereby affecting local intestinal inflammatory or other defense responses.
Expression of
Chlamydia pneumoniae
Polymorphic Membrane Protein Family Genes
Authors: Grimwood Jane , Olinger Lynn , Stephens Richard S. 
Published: July 2002

ABSTRACT

The genome of the obligate intracellular bacterium
Chlamydia pneumoniae
CWL029 encodes a family of 21 proteins with predicted outer membrane localization. These polymorphic membrane proteins (Pmps) are heterogeneous in both amino acid sequence and predicted size but are unified by the conserved amino acid motifs GGAI and FXXN repeated in the N-terminal half of each protein. Reverse transcriptase PCR analysis showed that all
pmp
genes are transcribed. To determine whether all proteins are expressed, specific antisera were generated by immunization with mutually exclusive synthetic peptides representing each of the 21 predicted Pmps. Each antiserum reacted with, and was typically immunospecific for, the corresponding peptide immunogen by enzyme-linked immunosorbent assay. Western blot analyses of purified elementary bodies showed that 11 of the 21 Pmps were detectable. Attempts to demonstrate by Sarykosyl fractionation that the Pmps were localized to the outer membrane revealed that several of the Pmps were unstable and readily degraded. Analyses of additional
C. pneumoniae
strains showed that although some Pmps are conserved, others vary between strains, in both molecular weight and level of expression.
Involvement of CD14 and Toll-Like Receptors in Activation of Human Monocytes byAspergillus fumigatusHyphae
Authors: Wang J. E. , Warris A. , Ellingsen E. A. , Jørgensen P. F. , Flo T. H. , Espevik T. , Solberg R. , Verweij P. E. , Aasen A. O. 
Published: July 2002

ABSTRACTInvasive fungal infections represent an increasing problem associated with high mortality. The present study was undertaken to identify leukocyte subsets that are activated by hyphal fragments in a whole-human-blood model, as well as to examine the involvement of CD14 and Toll-like receptors (TLRs) in activation of monocytes by hyphae. Incubation of whole human blood with hyphal fragments fromAspergillus fumigatusandScedosporium prolificansfor 6 h caused induction of mRNAs for tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and IL-6 in T cells, B cells, and monocytes, but not in granulocytes, as analyzed by reverse transcription-PCR with mRNA isolated from very pure populations of these leukocyte subsets. In primary adherent human monocytes, induction of TNF-α by hyphal fragments was dependent on plasma. Heat treatment of plasma at 56°C for 30 min strongly reduced the ability of plasma to prime for activation. Pretreatment of human monocytes with different concentrations (1, 3, and 10 μg/ml) of monoclonal antibody (MAb) HTA125 (anti-TLR4) or MAb 18D11 (anti-CD14) for 30 min inhibited the release of TNF-α induced by hyphal fragments in a dose-dependent manner. Maximal inhibitions of 35 and 70% were obtained with 10 μg of HTA125 and 18D11 per ml, respectively. In contrast, pretreatment with MAb TL2.1 (anti-TLR2) did not affect signaling induced by hyphae. Pretreatment with the lipid A antagonist B975 blocked lipopolysaccharide signaling but did not inhibit TNF-α production induced by hyphal fragments. Our results suggest that T cells, B cells, and monocytes are involved in the innate immune response to invasive fungal pathogens and that serum components are relevant for activation of monocytes by hyphae. CD14 and TLR4 may be involved in signaling ofAspergillushyphae in monocytes, but further studies to elucidate this issue are warranted.
Mu-Like Prophage in Serogroup B
Neisseria meningitidis
Coding for Surface-Exposed Antigens
Authors: Masignani Vega , Giuliani Marzia Monica , Tettelin Hervé , Comanducci Maurizio , Rappuoli Rino , Scarlato Vincenzo 
Published: July 2002

ABSTRACT

Sequence analysis of the genome of
Neisseria meningititdis
serogroup B revealed the presence of an ∼35-kb region inserted within a putative gene coding for an ABC-type transporter. The region contains 46 open reading frames, 29 of which are colinear and homologous to the genes of
Escherichia coli
Mu phage. Two prophages with similar organizations were also found in serogroup A meningococcus, and one was found in
Haemophilus influenzae
. Early and late phage functions are well preserved in this family of Mu-like prophages. Several regions of atypical nucleotide content were identified. These likely represent genes acquired by horizontal transfer. Three of the acquired genes are shown to code for surface-associated antigens, and the encoded proteins are able to induce bactericidal antibodies.
Antimycobacterial Agent Based on mRNA Encoding Human β-Defensin 2 Enables Primary Macrophages To Restrict Growth ofMycobacterium tuberculosis
Authors: Kisich Kevin O. , Heifets Leonid , Higgins Michael , Diamond Gill 
Published: July 2002

ABSTRACTHuman macrophages are hosts forMycobacterium tuberculosis, the causative agent of tuberculosis, which killed approximately 1.87 million people in 1997. Human alveolar macrophages do not express α- or β-defensins, broad-spectrum antimicrobial peptides which are expressed in macrophages from other species more resistant to infection withM. tuberculosis. It has been previously reported thatM. tuberculosisis susceptible to killing by defensins, which may explain the difference in resistance. Defensin peptides have been suggested as a possible therapeutic strategy for a variety of infectious diseases, but development has been hampered by difficulties in their large-scale production. Here we report the cellular synthesis of human β-defensin 2 via highly efficient mRNA transfection of human macrophages. This enabled mycobactericidal and mycobacteristatic activity by the macrophages. Although human macrophages are difficult to transfect with plasmid vectors, these studies illustrate that primary macrophages are permissive for mRNA transfection, which enabled expression of a potentially therapeutic protein.
Clumping Factor A Mediates Binding of
Staphylococcus aureus
to Human Platelets
Authors: Siboo Ian R. , Cheung Ambrose L. , Bayer Arnold S. , Sullam Paul M. 
Published: July 2002

ABSTRACT

The direct binding of bacteria to platelets may be an important virulence mechanism in the pathogenesis of infective endocarditis. We have previously described
Staphylococcus aureus
strain PS12, a Tn
551
-derived mutant of strain ISP479, with reduced ability to bind human platelets in vitro. When tested in an animal model of endocarditis, the PS12 strain was less virulent than its parental strain, as measured by bacterial densities in endocardial vegetations and incidence of systemic embolization. We have now characterized the gene disrupted in PS12 and its function in platelet binding. DNA sequencing, Southern blotting, and PCR analysis indicate that PS12 contained two Tn
551
insertions within the clumping factor A (ClfA) locus (
clfA
). The first copy was upstream from the
clfA
start codon and appeared to have no effect on ClfA production. The second insertion was within the region encoding the serine aspartate repeat of ClfA and resulted in the production of a truncated ClfA protein that was secreted from the cell. A purified, recombinant form of the ClfA A region, encompassing amino acids 40 through 559, significantly reduced the binding of ISP479C to human platelets by 44% (
P
= 0.0001). Immunoprecipitation of recombinant ClfA that had been incubated with solubilized platelet membranes coprecipitated a 118-kDa platelet membrane protein. This protein does not appear to be glycoprotein IIb. These results indicate that platelet binding by
S. aureus
is mediated in part by the direct binding of ClfA to a novel 118-kDa platelet membrane receptor.
Receptor for Fc on the Surfaces of Schistosomes
Authors: Loukas Alex , Jones Malcolm K. , King Lynette T. , Brindley Paul J. , McManus Donald P. 
Published: July 2002

ABSTRACTSchistosoma mansonimasks its surface with adsorbed host proteins including erythrocyte antigens, immunoglobulins, major histocompatibility complex class I, and β2-microglobulin (β2m), presumably as a means of avoiding host immune responses. How this is accomplished has not been explained. To identify surface receptors for host proteins, we biotinylated the tegument of liveS. mansoniadults and mechanically transformed schistosomula and then removed the parasite surface with detergent. Incubation of biotinylated schistosome surface extracts with human immunoglobulin G (IgG) Fc-Sepharose resulted in purification of a 97-kDa protein that was subsequently identified as paramyosin (Pmy), using antiserum specific for recombinant Pmy. Fc also bound recombinantS. mansoniPmy and nativeS. japonicumPmy. Antiserum to Pmy decreased the binding of Pmy to Fc-Sepharose, and no proteins bound after removal of Pmy from extracts. Fluoresceinated human Fc bound to the surface, vestigial penetration glands, and nascent oral cavity of mechanically transformed schistosomula, and rabbit anti-Pmy Fab fragments ablated the binding of Fc to the schistosome surface. Pmy coprecipitated with host IgG from parasite surface extracts, indicating that complexes formed on the parasite surface as well as in vitro. Binding of Pmy to Fc was not inhibited by soluble protein A, suggesting that Pmy does not bind to the region between the CH2 and CH3 domains used by many other Fc-binding proteins. β2m did not bind to the schistosome Fc receptor (Pmy), a finding that contradicts reports from earlier workers but did bind to a heteromultimer of labeled schistosomula surface proteins. This is the first report of the molecular identity of a schistosome Fc receptor; moreover it demonstrates an additional aspect of the unusual and multifunctional properties of Pmy from schistosomes and other parasitic flatworms.
Antibodies to Variant Antigens on the Surfaces of Infected Erythrocytes Are Associated with Protection from Malaria in Ghanaian Children
Authors: Dodoo Daniel , Staalsoe Trine , Giha Haider , Kurtzhals Jørgen A. L. , Akanmori Bartholomew D. , Koram Kojo , Dunyo Samuel , Nkrumah Francis K. , Hviid Lars , Theander Thor G. 
Published: July 2002

ABSTRACT

Plasmodium falciparum
erythrocyte membrane protein 1 (PfEMP1) is a variant antigen expressed on the surface of infected erythrocytes. Each parasite genome contains about 40 PfEMP1 genes, but only 1 PfEMP1 gene is expressed at a given time. PfEMP1 serves as a parasite-sequestering ligand to endothelial cells and enables the parasites to avoid splenic passage. PfEMP1 antibodies may protect from disease by inhibiting sequestration, thus facilitating the destruction of infected erythrocytes in the spleen. In this study, we have measured antibodies in Ghanaian children to a conserved region of PfEMP1 by enzyme-linked immunosorbent assay and antibodies to variant molecules on erythrocytes infected with field isolates of
P. falciparum
by flow cytometry. Based on close clinical monitoring, the children were grouped into those who did (susceptible) and those who did not (protected) have malaria during the season. The prevalences of antibodies to both the conserved PfEMP1 peptide and the variant epitopes were greater than 50%, and the levels of immunoglobulin G (IgG) correlated with age. The levels of antibodies to both the conserved peptide and the variant epitopes were higher in protected than in susceptible children. After correcting for the effect of age, the levels of IgG to variant antigens on a Sudanese and a Ghanaian parasite isolate remained significantly higher in protected than in susceptible children. Thus, the levels of IgG to variant antigens expressed on the surface of infected erythrocytes correlated with protection from clinical malaria. In contrast, the levels of IgG to a peptide derived from a conserved part of PfEMP1 did not correlate with protection from malaria.
Superoxide Dismutase-Deficient Mutants of
Helicobacter pylori
Are Hypersensitive to Oxidative Stress and Defective in Host Colonization
Authors: Seyler Richard W. , Olson Jonathan W. , Maier Robert J. 
Published: July 2002

ABSTRACT

Superoxide dismutase (SOD) is a nearly ubiquitous enzyme among organisms that are exposed to oxic environments. The single SOD of
Helicobacter pylori
, encoded by the
sodB
gene, has been suspected to be a virulence factor for this pathogenic microaerophile, but mutations in this gene have not been reported previously. We have isolated mutants with interruptions in the
sodB
gene and have characterized them with respect to their response to oxidative stress and ability to colonize the mouse stomach. The
sodB
mutants are devoid of SOD activity, based on activity staining in nondenaturing gels and quantitative assays of cell extracts. Though wild-type
H. pylori
is microaerophilic, the mutants are even more sensitive to O
2
for both growth and viability. While the wild-type strain is routinely grown at 12% O
2
, growth of the mutant strains is severely inhibited at above 5 to 6% O
2
. The effect of O
2
on viability was determined by subjecting nongrowing cells to atmospheric levels of O
2
and plating for survivors at 2-h time intervals. Wild-type cell viability dropped by about 1 order of magnitude after 6 h, while viability of the
sodB
mutant decreased by more than 6 orders of magnitude at the same time point. The mutants are also more sensitive to H
2
O
2
, and this sensitivity is exacerbated by increased O
2
concentrations. Since oxidative stress has been correlated with DNA damage, the frequency of spontaneous mutation to rifampin resistance was studied. The frequency of mutagenesis of an
sodB
mutant strain is about 15-fold greater than that of the wild-type strain. In the mouse colonization model, only 1 out of 23 mice inoculated with an SOD-deficient mutant of a mouse-adapted strain became
H. pylori
positive, while 15 out of 17 mice inoculated with the wild-type strain were shown to harbor the organism. Therefore, SOD is a virulence factor which affects the ability of this organism to colonize the mouse stomach and is important for the growth and survival of
H. pylori
under conditions of oxidative stress.
Growth Phase-Dependent Invasion of
Pseudomonas aeruginosa
and Its Survival within HeLa Cells
Authors: Ha Unhwan , Jin Shouguang 
Published: July 2002

ABSTRACT

Clinical isolates of
Pseudomonas aeruginosa
are classified into invasive and noninvasive (cytolytic) strains. In a noninvasive PA103 background, ExoS and ExoT have recently been shown to function as anti-internalization factors. However, these two factors seemed not to have such a function in an invasive strain PAK background. In this study, using HeLa tissue culture cells, we observed that the internalization of invasive strain PAK is dependent on its growth phases, with the stationary-phase cells internalized about 100-fold more efficiently than the exponential-phase cells. This growth phase-dependent internalization was not observed in the noninvasive PA103 strain. Further analysis of various mutant derivatives of the invasive PAK and the noninvasive PA103 strains demonstrated that ExoS or ExoT that is injected into host cells by a type III secretion machinery functions as an anti-internalization factor in both types of strains. In correlation with the growth phase-dependent internalization, the invasive strain PAK translocates much higher amount of ExoS and ExoT into HeLa cells when it is in an exponential-growth phase than when it is in a stationary-growth phase, whereas the translocation of ExoT by the noninvasive strain PA103 is consistently high regardless of the growth phases, suggesting a difference in the regulatory mechanism of type III secretion between the two types of strains. Consistent with the invasive phenotype of the parent strain, an internalized PAK derivative survived well within the HeLa cells, whereas the viability of internalized PA103 derivative was dramatically decreased and completely cleared within 48 h. These results indicate that the invasive strains of
P. aeruginosa
have evolved the mechanism of intracellular survival, whereas the noninvasive
P. aeruginosa
strains have lost or not acquired the ability to survive within the epithelial cells.
Novel Type of Fimbriae Encoded by the Large Plasmid of Sorbitol-Fermenting Enterohemorrhagic
Escherichia coli
O157:H
−
Authors: Brunder Werner , Khan A. Salam , Hacker Jörg , Karch Helge 
Published: July 2002

ABSTRACT

Sorbitol-fermenting (SF) enterohemorrhagic
Escherichia coli
(EHEC) O157:H
−
have emerged as important causes of diarrheal diseases and the hemolytic-uremic syndrome in Germany. In this study, we characterized a 32-kb fragment of the plasmid of SF EHEC O157:H
−
, pSFO157, which differs markedly from plasmid pO157 of classical non-sorbitol-fermenting EHEC O157:H7. We found a cluster of six genes, termed
sfpA
,
sfpH
,
sfpC
,
sfpD
,
sfpJ,
and
sfpG,
which mediate mannose-resistant hemagglutination and the expression of fimbriae.
sfp
genes are similar to the
pap
genes, encoding P-fimbriae of uropathogenic
E. coli
, but the
sfp
cluster lacks homologues of genes encoding subunits of a tip fibrillum as well as regulatory genes. The major pilin, SfpA, despite its similarity to PapA, does not cluster together with known PapA alleles in a phylogenetic tree but is structurally related to the PmpA pilin of
Proteus mirabilis
. The putative adhesin gene
sfpG
, responsible for the hemagglutination phenotype, shows significant homology neither to
papG
nor to other known sequences. Sfp fimbriae are 3 to 5 nm in diameter, in contrast to P-fimbriae, which are 7 nm in diameter. PCR analyses showed that the
sfp
gene cluster is a characteristic of SF EHEC O157:H
−
strains and is not present in other EHEC isolates, diarrheagenic
E. coli,
or other
Enterobacteriaceae
. The
sfp
gene cluster is flanked by two blocks of insertion sequences and an origin of plasmid replication, indicating that horizontal gene transfer may have contributed to the presence of Sfp fimbriae in SF EHEC O157:H
−
.