bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Protein Variation by Expression Site Switching in the Relapsing Fever Agent
Borrelia hermsii
Authors: Barbour Alan G. , Carter Carol J. , Sohaskey Charles D. 
Published: July 2002

ABSTRACT

Borrelia hermsii
, an agent of relapsing fever, undergoes antigenic variation of serotype-specifying membrane proteins during mammalian infections. When
B. hermsii
is cultivated in broth medium, one serotype, 33, eventually predominates in the population. Serotype 33 has also been found to be dominant in ticks but not in mammalian hosts. We investigated the biology and genetics of two independently derived clonal populations of serotype 33 of
B. hermsii
. Both isolates infected immunodeficient mice, but serotype 33 cells were limited in number and were only transiently present in the blood. Probes for
vsp33
, which encodes the serotype-specifying Vsp33 outer membrane protein, revealed that the gene was located on a 53-kb linear plasmid and that there was only one locus for the gene in serotype 33. The
vsp33
probe and probes for other variable membrane protein genes showed that expression of Vsp33 was determined at the level of transcription and that when the
vsp33
expression site was active, an expression site for other variable proteins was silent. The study confirmed that serotype 33 is distinct from other serotypes of
B. hermsii
in its biology and demonstrated that
B. hermsii
can change its major surface protein through switching between two expression sites.
Nonpolar Inactivation of the Hypervariable Streptococcal Inhibitor of Complement Gene (
sic
) in Serotype M1
Streptococcus pyogenes
Significantly Decreases Mouse Mucosal Colonization
Authors: Lukomski Slawomir , Hoe Nancy P. , Abdi Iman , Rurangirwa Jacqueline , Kordari Parichher , Liu Mengyao , Dou Shu-Jun , Adams Gerald G. , Musser James M. 
Published: July 2002

ABSTRACT

Group A
Streptococcus
(GAS) is a human pathogen that commonly infects the upper respiratory tract. GAS serotype M1 strains are frequently isolated from human infections and contain the gene encoding the hypervariable streptococcal inhibitor of complement protein (Sic). It was recently shown that Sic variants were rapidly selected on mucosal surfaces in epidemic waves caused by M1 strains, an observation suggesting that Sic participates in host-pathogen interactions on the mucosal surface (N. P. Hoe, K. Nakashima, S. Lukomski, D. Grigsby, M. Liu, P. Kordari, S.-J. Dou, X. Pan, J. Vuopio-Varkila, S. Salmelinna, A. McGeer, D. E. Low, B. Schwartz, A. Schuchat, S. Naidich, D. De Lorenzo, Y.-X. Fu, and J. M. Musser, Nat. Med. 5:924–929, 1999). To test this idea, a new nonpolar mutagenesis method employing a spectinomycin resistance cassette was used to inactivate the
sic
gene in an M1 GAS strain. The isogenic Sic-negative mutant strain was significantly (
P
< 0.019) impaired in ability to colonize the mouse mucosal surface after intranasal infection. These results support the hypothesis that the predominance of M1 strains in human infections is related, in part, to a Sic-mediated enhanced colonization ability.
Mannose-Binding Lectin Binds to a Range of Clinically Relevant Microorganisms and Promotes Complement Deposition
Authors: Neth Olaf , Jack Dominic L. , Dodds Alister W. , Holzel Helen , Klein Nigel J. , Turner Malcolm W. 
Published: July 2002

ABSTRACTMannose-binding lectin (MBL) is a collagenous serum lectin believed to be of importance in innate immunity. Genetically determined low levels of the protein are known to predispose to infections. In this study the binding of purified MBL to pathogens isolated from immunocompromised children was investigated by flow cytometry. DiverseCandidaspecies,Aspergillus fumigatus,Staphylococcus aureus, and beta-hemolytic group A streptococci exhibited strong binding of MBL, whereasEscherichia coli,Klebsiellaspecies, andHaemophilus influenzaetype b were characterized by heterogeneous binding patterns. In contrast, beta-hemolytic group B streptococci,Streptococcus pneumoniae, andStaphylococcus epidermidisshowed low levels of binding. Bound MBL was able to promote C4 deposition in a concentration-dependent manner. We conclude that MBL may be of importance in first-line immune defense against several important pathogens.
Role of Tir and Intimin in the Virulence of Rabbit EnteropathogenicEscherichia coliSerotype O103:H2
Authors: Marchès Olivier , Nougayrède Jean-Philippe , Boullier Séverine , Mainil Jacques , Charlier Gérard , Raymond Isabelle , Pohl Pierre , Boury Michèle , De Rycke Jean , Milon Alain , Oswald Eric 
Published: July 2002

ABSTRACTAttaching and effacing (A/E) rabbit enteropathogenicEscherichia coli(REPEC) strains belonging to serogroup O103 are an important cause of diarrhea in weaned rabbits. Like human EPEC strains, they possess the locus of enterocyte effacement clustering the genes involved in the formation of the A/E lesions. In addition, pathogenic REPEC O103 strains produce an Esp-dependent but Eae (intimin)-independent alteration of the host cell cytoskeleton characterized by the formation of focal adhesion complexes and the reorganization of the actin cytoskeleton into bundles of stress fibers. To investigate the role of intimin and its translocated coreceptor (Tir) in the pathogenicity of REPEC, we have used a newly constructed isogenictirnull mutant together with a previously describedeaenull mutant. When human HeLa epithelial cells were infected, thetirmutant was still able to induce the formation of stress fibers as previously reported for theeaenull mutant. When the rabbit epithelial cell line RK13 was used, REPEC O103 produced a classical fluorescent actin staining (FAS) effect, whereas both theeaeandtirmutants were FAS negative. In a rabbit ligated ileal loop model, neither mutant was able to induce A/E lesions. In contrast to the parental strain, which intimately adhered to the enterocytes and destroyed the brush border microvilli, bacteria of both mutants were clustered in the mucus without reaching and damaging the microvilli. The role of intimin and Tir was then analyzed in vivo by oral inoculation of weaned rabbits. Although both mutants were still present in the intestinal flora of the rabbits 3 weeks after oral inoculation, neither mutant strain induced any clinical signs or significant weight loss in the inoculated rabbits whereas the parental strain caused the death of 90% of the inoculated rabbits. Nevertheless, an inflammatory infiltrate was present in the lamina propria of the rabbits infected with both mutants, with an inflammatory response greater for theeaenull mutant. In conclusion, we have confirmed the role of intimin in virulence, and we have shown, for the first time, that Tir is also a key factor in vivo for pathogenicity.
Cloning and Sequencing of the
Klebsiella pneumoniae
O5
wb
Gene Cluster and Its Role in Pathogenesis
Authors: Merino Susana , Altarriba Maria , Izquierdo Luis , Nogueras María Mercé , Regué Miguel , Tomás Juan M. 
Published: July 2002

ABSTRACT

One representative recombinant clone encoding
Klebsiella pneumoniae
O5-antigen lipopolysaccharide (LPS) was found upon screening for serum resistance in a cosmid-based genomic library of
K. pneumoniae
KT769 (O5:K57) introduced into
Escherichia coli
DH5α. A total of eight open reading frames (
wb
O5
gene cluster) were necessary to produce
K. pneumoniae
O5-antigen LPS in
E. coli
K-12. The enzymatic activities proposed for the
wb
O5
gene cluster are in agreement with the activities proposed for the biosynthesis of
K. pneumoniae
O5-antigen LPS. Using the complete DNA sequence of the
K. pneumoniae wb
O5
gene cluster, we obtained (by single or double recombination) genetically well-characterized mutants devoid only of this O5-antigen LPS. Finally, using these O5
−
mutants and the corresponding wild-type strains or complemented mutants with the
wb
O5
gene cluster (O5
+
strains), we found that the presence of
K. pneumoniae
O5-antigen LPS is essential for some pathogenic features like serum resistance, adhesion to uroepithelial cells, and colonization (experimental infections) of the urinary tract in rats.
Interactions between Periodontal Bacteria and Human Oral Epithelial Cells:
Fusobacterium nucleatum
Adheres to and Invades Epithelial Cells
Authors: Han Yiping W. , Shi Wenyuan , Huang George T.-J. , Kinder Haake Susan , Park No-Hee , Kuramitsu Howard , Genco Robert J. 
Published: July 2002

ABSTRACT

Bacteria are causative agents of periodontal diseases. Interactions between oral bacteria and gingival epithelial cells are essential aspects of periodontal infections. Using an in vitro tissue culture model, a selected group of gram-negative anaerobic bacteria frequently associated with periodontal diseases, including
Bacteroides forsythus
,
Campylobacter curvus
,
Eikenella corrodens
,
Fusobacterium nucleatum
,
Porphyromonas gingivalis
, and
Prevotella intermedia
, were examined for their ability to adhere to and invade primary cultures of human gingival epithelial cells (HGEC). The effects of these bacteria on the production of interleukin-8 (IL-8), a proinflammatory chemokine, were also measured. These studies provided an initial demonstration that
F. nucleatum
adhered to and invaded HGEC and that this was accompanied by high levels of IL-8 secretion from the epithelial cells. The attachment and invasion characteristics of
F. nucleatum
were also tested using KB cells, an oral epithelial cell line. The invasion was verified by transmission electron microscopy and with metabolic inhibitors. Invasion appeared to occur via a “zipping” mechanism and required the involvement of actins, microtubules, signal transduction, protein synthesis, and energy metabolism of the epithelial cell, as well as protein synthesis by
F. nucleatum
. A spontaneous mutant,
lam
, of
F. nucleatum
, isolated as defective in autoagglutination, was unable to attach to or invade HGEC or KB cells, further indicating the requirement of bacterial components in these processes. Sugar inhibition assays indicated that lectin-like interactions were involved in the attachment of
F. nucleatum
to KB cells. Investigation of these new virulence phenotypes should improve our understanding of the role of
F. nucleatum
in periodontal infections.
Bile Mediates Intestinal Pathology in Endotoxemia in Rats
Authors: Jackson Graham D. F. , Dai Yung , Sewell William A. 
Published: July 2002

ABSTRACTIntestinal pathology frequently accompanies experimental endotoxic shock and is mediated by proinflammatory cytokines. Our hypotheses are that hepatobiliary factors operating from the luminal side of the gut make a major contribution to this damage and that tumor necrosis factor alpha (TNF-α) is involved in the pathology. We treated rats with lipopolysaccharide (LPS) intravenously and found that external drainage of bile totally protected the gastrointestinal tract, macroscopically and microscopically, 4 h after LPS administration and dramatically improved survival of the animals for 48 h after LPS administration. The concentration of TNF-α in bile increased markedly after LPS administration and was over 30 times higher in bile than in serum. Tissue damage and the biliary TNF-α response were abrogated when animals were pretreated with gadolinium chloride to eliminate Kupffer cells. TNF-α infusion into the duodenal lumen caused intestinal damage similar to that elicited by intravenous LPS. In rats treated with LPS, survival was significantly increased during the first 36 h in animals given an infusion of anti-TNF-α antibody into the duodenum. These results demonstrate that in endotoxemia, intestinal damage is mediated by factors derived from the bile. The findings indicate that luminally acting TNF-α contributes to the intestinal damage.
Enhancement of Clearance of Bacteria from Murine Lungs by Immunization with Detoxified Lipooligosaccharide fromMoraxella catarrhalisConjugated to Proteins
Authors: Hu Wei-Gang , Chen Jing , Battey James F. , Gu Xin-Xing 
Published: July 2002

ABSTRACTMoraxella catarrhalisstrain 25238 detoxified lipooligosaccharide (dLOS)-protein conjugates induced a significant rise of bactericidal anti-LOS antibodies in animals. This study reports the effect of active or passive immunization with the conjugates or their antiserum on pulmonary clearance ofM. catarrhalisin an aerosol challenge mouse model. Mice were injected subcutaneously with dLOS-tetanus toxoid (dLOS-TT), dLOS–high-molecular-weight proteins (dLOS-HMP) from nontypeableHaemophilus influenzae(NTHi), or nonconjugated materials in Ribi adjuvant and then challenged withM. catarrhalisstrain 25238 or O35E or NTHi strain 12. Immunization with dLOS-TT or dLOS-HMP generated a significant rise of serum anti-LOS immunoglobulin G and 68% and 35 to 41% reductions of bacteria in lungs compared with the control (P< 0.01) following challenge with homologous strain 25238 and heterologous strain O35E, respectively. Serum anti-LOS antibody levels correlated with its bactericidal titers againstM. catarrhalisand bacterial CFU in lungs. Additionally, immunization with dLOS-HMP generated a 54% reduction of NTHi strain 12 compared with the control (P< 0.01). Passive immunization with a rabbit antiserum against dLOS-TT conferred a significant reduction of strain 25238 CFU in lungs in a dose- and time-dependent pattern compared with preimmune serum-treated mice. Kinetic examination of lung tissue sections demonstrated that antiserum-treated mice initiated and offset inflammatory responses more rapidly than preimmune serum-treated mice. These data indicate that LOS antibodies (whether active or passive) play a major role in the enhancement of pulmonary clearance of different test strains ofM. catarrhalisin mice. In addition, dLOS-HMP is a potential candidate for a bivalent vaccine againstM. catarrhalisand NTHi infections.
Enterococcus faecalis
Adhesin, Ace, Mediates Attachment to Extracellular Matrix Proteins Collagen Type IV and Laminin as well as Collagen Type I
Authors: Nallapareddy Sreedhar R. , Qin Xiang , Weinstock George M. , Höök Magnus , Murray Barbara E. 
Published: July 2002

ABSTRACT

Adhesin-mediated binding to extracellular matrix (ECM) proteins is thought to be a crucial step in the pathogenic process of many bacterial infections. We have previously reported conditional adherence of most
Enterococcus faecalis
isolates, after growth at 46°C, to ECM proteins collagen types I and IV and laminin; identified an
E. faecalis
-specific gene,
ace
, whose encoded protein has characteristics of a bacterial adhesin; and implicated Ace in binding to collagen type I. In this study, we constructed an
ace
disruption mutant from
E. faecalis
strain OG1RF that showed marked reduction in adherence to collagen types I and IV and laminin when compared to the parental OG1RF strain after growth at 46°C. Polyclonal immune serum raised against the OG1RF-derived recombinant Ace A domain reacted with a single ∼105-kDa band of mutanolysin extracts from OG1RF grown at 46°C, while no band was detected in extracts from OG1RF grown at 37°C, nor from the OG1RF
ace
mutant grown at 37 or 46°C. IgGs purified from the anti-Ace A immune serum inhibited adherence of 46°C-grown
E. faecalis
OG1RF to immobilized collagen type IV and laminin as well as collagen type I, at a concentration as low as 1 μg/ml, and also inhibited the 46°C-evoked adherence of two clinical isolates tested. We also showed in vitro interaction of collagen type IV with Ace from OG1RF mutanolysin extracts on a far-Western blot. Binding of recombinant Ace A to immobilized collagen types I and IV and laminin was demonstrated in an enzyme-linked immunosorbent assay and was shown to be concentration dependent. These results indicate that Ace A mediates the conditional binding of
E. faecalis
OG1RF to collagen type IV and laminin in addition to collagen type I.
Induction of Immune Response in BALB/c Mice with a DNA Vaccine Encoding Bacterioferritin or P39 ofBrucellaspp
Authors: Al-Mariri Ayman , Tibor Anne , Mertens Pascal , De Bolle Xavier , Michel Patrick , Godfroid Jacques , Walravens Karl , Letesson Jean-Jacques 
Published: July 2002

ABSTRACTIn this study, we evaluated the ability of DNA vaccines encoding the bacterioferritin (BFR) or P39 proteins ofBrucellaspp. to induce cellular and humoral immune responses and to protect BALB/c mice against a challenge withB. abortus544. We constructed eukaryotic expression vectors called pCIBFR and pCIP39, encoding BFR or P39 antigens, respectively, and we verified that these proteins were produced after transfection of COS-7 cells. PCIBFR or pCIP39 was injected intramuscularly three times, at 3-week intervals. pCIP39 induced higher antibody responses than did the DNA vector encoding BFR. Both vectors elicited a T-cell-proliferative response and also induced a strong gamma interferon production upon restimulation with either the specific antigens orBrucellaextract. In this report, we also demonstrat that animals immunized with these plasmids elicited a strong and long-lived memory immune response which persisted at least 3 months after the third vaccination. Furthermore, pCIBFR and pCIP39 induced a typical T-helper 1-dominated immune response in mice, as determined by cytokine or immunoglobulin G isotype analysis. The pCIP39 delivered by intramuscular injection (but not the pCIBFR or control vectors) induced a moderate protection in BALB/c mice challenged withB. abortus544 compared to that observed in positive control mice vaccinated with S19.
Phenotypic and Genomic Analyses of the
Mycobacterium avium
Complex Reveal Differences in Gastrointestinal Invasion and Genomic Composition
Authors: McGarvey Jeffery A. , Bermudez Luiz E. 
Published: July 2002

ABSTRACT

Mycobacterium avium
and
Mycobacterium intracellulare
are closely related organisms and comprise the
Mycobacterium avium
complex. These organisms share many common characteristics, including the ability to cause life-threatening respiratory infections in people with underlying lung pathology or immunological defects and occasionally in those with no known predisposing conditions. However, the ability to invade the mucosa of the gastrointestinal tract and cause disseminated disease in AIDS patients has not been epidemiologically linked to
M. intracellulare
and appears to be unique to
M. avium
. We compared the abilities of
M. avium
and
M. intracellulare
to tolerate the acidic conditions of the stomach, to resist the membrane-disrupting activity of cationic peptides, and to invade intestinal epithelial cells in vitro and in vivo. We observed that
M. avium
and
M. intracellulare
were both tolerant to the acidic conditions encountered in the stomach and resistant to cationic peptides. However, when strains of
M. avium
and
M. intracellulare
were examined for their ability to enter cultured human intestinal cells or mouse intestinal mucosa, we observed that
M. avium
could invade more efficiently than
M. intracellulare
. To elucidate the basis of this pathogenic difference and identify genes involved in the invasion of the intestinal mucosa, we performed chromosomal DNA subtractive hybridization using
M. avium
and
M. intracellulare
chromosomal DNAs. In all, 21 genes that were present in
M. avium
but absent in
M. intracellulare
were identified, including some that may be associated with the ability of
M. avium
to invade the intestinal mucosa.
Virulence Plasmid ofRhodococcus equiContains Inducible Gene Family Encoding Secreted Proteins
Authors: Byrne Barbara A. , Prescott John F. , Palmer Guy H. , Takai Shinji , Nicholson Vivian M. , Alperin Debra C. , Hines Stephen A. 
Published: July 2002

ABSTRACTRhodococcus equicauses severe pyogranulomatous pneumonia in foals. This facultative intracellular pathogen produces similar lesions in immunocompromised humans, particularly in AIDS patients. Virulent strains ofR. equibear a large plasmid that is required for intracellular survival within macrophages and for virulence in foals and mice. Only two plasmid-encoded proteins have been described previously; a 15- to 17-kDa surface protein designated virulence-associated protein A (VapA) and an antigenically related 20-kDa protein (herein designated VapB). These two proteins are not expressed by the sameR. equiisolate. We describe here the substantial similarity between VapA and VapB. Moreover, we identify three additional genes carried on the virulence plasmid,vapC, -D, and -E, that are tandemly arranged downstream ofvapA. These new genes are members of a gene family and encode proteins that are approximately 50% homologous to VapA, VapB, and each other.vapC, -D, and -Eare found only inR. equistrains that express VapA and are highly conserved in VapA-positive isolates from both horses and humans. VapC, -D, and -E are secreted proteins coordinately regulated by temperature with VapA; the proteins are expressed whenR. equiis cultured at 37°C but not at 30°C, a finding that is compatible with a role in virulence. As secreted proteins, VapC, -D, and -E may represent targets for the prevention of rhodococcal pneumonia. An immunologic study using VapA-specific antibodies and recombinant Vap proteins revealed no evidence of cross-reactivity despite extensive sequence similarity over the carboxy terminus of all four proteins.
Familial Correlation of Immunoglobulin G Subclass Responses to
Plasmodium falciparum
Antigens in Burkina Faso
Authors: Aucan Christophe , Traoré Yves , Fumoux Francis , Rihet Pascal 
Published: July 2002

ABSTRACT

Host genes are thought to determine the immune response to malaria infection and the outcome. Cytophilic antibodies have been associated with protection, whereas noncytophilic antibodies against the same epitopes may block the protective activity of the protective ones. To assess the contribution of genetic factors to immunoglobulin G (IgG) subclass responses against conserved epitopes and
Plasmodium falciparum
blood-stage extracts, we analyzed the isotypic distribution of the IgG responses in 366 individuals living in two differently exposed areas in Burkina Faso. We used one-way analysis of variance and pairwise estimators to calculate sib-sib and parent-offspring correlation coefficients, respectively. Familial patterns of inheritance of IgG subclass responses to defined antigens and
P. falciparum
extracts appear to be similar in the two areas. We observed a sibling correlation for the IgG, IgG1, IgG2, IgG3, and IgG4 responses directed against ring-infected-erythrocyte surface antigen, merozoite surface protein 1 (MSP-1), MSP-2, and
P. falciparum
extract. Moreover, a parent-offspring correlation was found for several IgG subclass responses, including the IgG, IgG1, IgG2, IgG3, and IgG4 responses directed against conserved MSP-2 epitopes. Our results indicated that the IgG subclass responses against
P. falciparum
blood-stage antigens are partly influenced by host genetic factors. The localization and identification of these genes may have implications for immunoepidemiology and vaccine development.