PubMed Health⌕ Search

Biomedical subjects

J B Dale

Publications and source records attributed to J B Dale.

At least 19 recordsLinked to original sources
PubMed2002

Hormonal regulation of androgen receptor messenger ribonucleic acid expression in human tooth pulp.

Tooth pulp contains steroid receptors and therefore is likely to respond to steroids. Steroids and cytokines together can alter steroid receptor content in many tissues; thus, similar mechanisms may exist in tooth pulp. In this study, reverse-transcription/polymerase chain-reaction was used to screen human pulp for the mRNAs encoding receptors for androgen (AR), estrogens (ERbeta), and hepatocyte growth factor (HGF: c-Met). AR mRNA content was greater in male pulp vs. female pulp in all age groups. In both genders, AR mRNA content diminished with age. In pulp cell cultures, androstenedione, estradiol-17beta, and HGF each stimulated AR mRNA accumulation. Testosterone inhibited, whereas 5alpha-dihydrotestosterone did not affect, AR mRNA content. ERbeta was not hormonally altered in pulp cell cultures. By showing steroid- and cytokine-orchestrated regulation of AR mRNA in vitro, it is possible that age- and/or pathogen-dependent changes in available steroids and cytokines can affect any androgen-responsiveness of pulp.

Adolescent↗
PubMed2001

Spa contributes to the virulence of type 18 group A streptococci.

Streptococcal protective antigen (Spa) is a newly described surface protein of group A streptococci that was recently shown to evoke protective antibodies (J. B. Dale, E. Y. Chiang, S. Liu, H. S. Courtney, and D. L. Hasty, J. Clin. Investig. 103:1261--1268, 1999). In this study, we have determined the complete sequence of the spa gene from type 18 streptococci. Purified, recombinant Spa protein evoked antibodies that were bactericidal against type 18 streptococci, confirming the presence of protective epitopes. Sera from patients with acute rheumatic fever contained antibodies against recombinant Spa, indicating that the Spa protein is expressed in vivo and is immunogenic in humans. To determine the role of Spa in the virulence of group A streptococci, we created a series of insertional mutants that were (i) Spa negative and M18 positive, (ii) Spa positive and M18 negative, and (iii) Spa negative and M18 negative. The mutants and the parent M18 strain (18-282) were used in assays to determine resistance to phagocytosis, growth in human blood, and mouse virulence. The results show that Spa is a virulence determinant of group A streptococci and that expression of both Spa and M18 is required for optimal virulence of type 18 streptococci.

Amino Acid Sequence↗
PubMed2000

Identification of a gene within a pathogenicity island of enterotoxigenic Escherichia coli H10407 required for maximal secretion of the heat-labile enterotoxin.

Studies of the pathogenesis of enterotoxigenic Escherichia coli (ETEC) have largely centered on extrachromosomal determinants of virulence, in particular the plasmid-encoded heat-labile (LT) and heat-stable enterotoxins and the colonization factor antigens. ETEC causes illnesses that range from mild diarrhea to severe cholera-like disease. These differences in disease severity are not readily accounted for by our current understanding of ETEC pathogenesis. Here we demonstrate that Tia, a putative adhesin of ETEC H10407, is encoded on a large chromosomal element of approximately 46 kb that shares multiple features with previously described E. coli pathogenicity islands. Further analysis of the region downstream from tia revealed the presence of several candidate open reading frames (ORFs) in the same transcriptional orientation as tia. The putative proteins encoded by these ORFs bear multiple motifs associated with bacterial secretion apparatuses. An in-frame deletion in one candidate gene identified here as leoA (labile enterotoxin output) resulted in marked diminution of secretion of the LT enterotoxin and lack of fluid accumulation in a rabbit ileal loop model of infection. Although previous studies have suggested that E. coli lacks the capacity to secrete LT, our studies show that maximal release of LT from the periplasm of H10407 is dependent on one or more elements encoded on a pathogenicity island.

Adhesins, Bacterial↗
PubMed1999

Multivalent group A streptococcal vaccine designed to optimize the immunogenicity of six tandem M protein fragments.

One of the major challenges in the development of group A streptococcal M protein-based vaccines is the multiplicity of M types expressed by these organisms. Previous studies have shown that multivalent vaccines containing as many as eight M protein fragments in tandem were immunogenic and evoked opsonic antibodies. It was also noted that the C-terminal fragments of these hybrid proteins were often not immunogenic or evoked only low levels of opsonic antibodies, suggesting that the C-terminus of the molecule may have been preferentially degraded or altered in vivo. In the present studies, we designed a hexavalent vaccine containing protective M protein peptides from types 24, 5, 6, 19, 1, and 3 group A streptococci. In order to "protect" the carboxy-terminal components, the amino-terminal M24 fragment was reiterated on the carboxy-terminal end of the construct. The hexavalent vaccine was immunogenic in laboratory animals and evoked high titers of antibodies against each of the native M proteins represented in the vaccine and bactericidal antibodies against all six sterotypes of group A streptococci. The vaccine was equally immunogenic when delivered in alum or in complete Freund's adjuvant. None of the immune sera contained antibodies that crossreacted with human heart tissue. Our results show that complex multivalent group A streptococcal vaccines can be designed in such a way that each M protein fragment is immunogenic and evokes protective antibodies.

Alum Compounds↗
PubMed1999

Group A streptococcal vaccines.

The pathogenesis of group A streptococcal infections, and antigens that contribute to protective immune responses are reviewed. Several approaches to vaccine development are discussed. Data are provided from preclinical studies of multivalent M protein-based vaccines that evoke protective antibodies in laboratory animals. Also discussed are future strategies for the development of broadly protective vaccines, and their potential impact on the incidence of streptococcal infections, and acute rheumatic fever.

Animals↗
PubMed1999

Serum opacity factor is a major fibronectin-binding protein and a virulence determinant of M type 2 Streptococcus pyogenes.

Serum opacity factor (SOF) is a fibronectin-binding protein of group A streptococci that opacifies mammalian sera and is expressed by some strains that cause impetigo, pharyngitis and acute glomerulonephritis. Although SOF is expressed by approximately 35% of known serotypes, its role in the pathogenesis of group A streptococcal infections has not been previously investigated. The sof genes from M types 2, 28 and 49 Streptococcus pyogenes were cloned, sequenced, and their deduced amino acid sequences were compared. The gene for FnBA, a fibronectin-binding protein from Streptococcus dysgalactiae, was also cloned and found to express an opacity factor. The leader sequences, the fibronectin-binding domains, and the membrane anchor regions of these proteins were highly conserved. Short spans of conserved sequences were interspersed throughout the remaining parts of the proteins. The sof2 gene was insertionally inactivated in an M type 2 S. pyogenes strain, T2MR. The resultant SOF-negative mutant (YL3) did not express SOF or opacify serum, and exhibited a 71% reduction in binding fibronectin. Complementation of the SOF-negative defect with sof28 in the recombinant strain YL3(pNZ28) fully restored fibronectin-binding activity and the ability to opacify serum. To determine whether sof plays a role in virulence, mice were challenged intraperitoneally with these strains. None of the 10 mice infected with YL3(pNZ28) survived and only 1 out of 15 mice challenged with T2MR survived, whereas 12 out of 15 mice infected with YL3 survived. These data clearly indicate that SOF is a virulence factor, and they provide the first direct evidence that a fibronectin-binding protein contributes to the pathogenesis of group A streptococcal infections in vivo.

Amino Acid Sequence↗
PubMed1999

Comparison of adherence to and penetration of a human laryngeal epithelial cell line by group A streptococci of various M protein types.

Clinically isolated group A streptococci (GAS) of different M protein types were studied using aminoglycoside exclusion and [2,8-3H]adenine radiolabeled GAS assays to compare the abilities of different strains to adhere to and internalize within human laryngeal epithelial (HEp-2) cells. GAS isolated from patients with pharyngitis and GAS isolated from patients with more severe disease, such as necrotizing fasciitis, adhered to and penetrated HEp-2 cells equally well. M3, M4, M6, and M12 strains adhered to and were internalized within HEp-2 cells more than M1 strains. M18 GAS producing hyaluronic acid capsules were less adherent and less invasive than the M3, M4, M6, and M12 strains. An M3-producing GAS strain and its M protein-deficient isogenic strain adhered similarly to HEp-2 cells, but the M protein-deficient strain exhibited greater penetration. Preincubation of HEp-2 cells with an N-terminal synthetic M3 peptide did not alter the adherence or penetration by an M3 strain. In summary, this study demonstrates that GAS from invasive and non-invasive disease adhere to and penetrate HEp-2 cells equally well and that multiple strains of GAS with various M protein types have the ability to adhere to and penetrate HEp-2 cells.

Antigens, Bacterial↗
PubMed1999

New protective antigen of group A streptococci.

It is widely believed that the surface M protein of group A streptococci is the predominant surface protein of these organisms containing opsonic epitopes. In the present study, we identified a new surface protein, distinct from M protein, that evokes protective antibodies. A type 18 M-negative mutant was found to be both resistant to phagocytosis in human blood and virulent in mice. The wild-type strain, but not the M-negative mutant, was opsonized by antisera against purified recombinant M18 protein or a synthetic peptide copying the NH2-terminus of M18. However, antisera raised against a crude pepsin extract of the M-negative mutant opsonized both strains, indicating the presence of a protective antigen in addition to type 18 M protein. This antiserum was used to identify and purify a 24-kDa protein fragment (Spa, streptococcal protective antigen) that evoked antibodies that opsonized the M18 parent and the M-negative mutant. The results of passive mouse protection tests confirmed the presence of protective epitopes within Spa. The deduced amino acid sequence of a 636-bp 5' fragment of the spa18 gene showed no homology with sequences in GenBank. These studies reveal the presence of a new protective antigen of certain strains of group A streptococci that may prove to be an important component of vaccines to prevent streptococcal infections.

Amino Acid Sequence↗
PubMed1998

Opsonic antibodies to the surface M protein of group A streptococci in pooled normal immunoglobulins (IVIG): potential impact on the clinical efficacy of IVIG therapy for severe invasive group A streptococcal infections.

The surface M protein of group A streptococci (GAS) is one of the major virulence factors for this pathogen. Antibodies to the M protein can facilitate opsonophagocytosis by phagocytic cells present in human blood. We investigated whether pooled normal immunoglobulin G (IVIG) contains antibodies that can opsonize and enhance the phagocytosis of type M1 strains of GAS and whether the levels of these antibodies vary for different IVIG preparations. We focused on the presence of anti-M1 antibodies because the M1T1 serotype accounts for the majority of recent invasive GAS clinical isolates in our surveillance studies. The level of anti-M1 antibodies in three commercial IVIG preparations was determined by enzyme-linked immunosorbent assay (ELISA), and the opsonic activity of these antibodies was determined by neutrophil-mediated opsonophagocytosis of a representative M1T1 isolate. High levels of opsonic anti-M1 antibodies were found in all IVIG preparations tested, and there was a good correlation between ELISA titers and opsonophagocytic activity. However, there was no significant difference in the levels of opsonic anti-M1 antibodies among the various IVIG preparations or lots tested. Adsorption of IVIG with M1T1 bacteria removed the anti-M1 opsonic activity, while the level of anti-M3 opsonophagocytosis was unchanged. Plasma was obtained from seven patients with streptococcal toxic shock syndrome who received IVIG therapy, and the level of anti-M1 antibodies was assessed before and after IVIG administration. A significant increase in the level of type M1-specific antibodies was found in the plasma of all patients who received IVIG therapy (P < 0.006). The results reveal another potential mechanism by which IVIG can ameliorate severe invasive group A streptococcal infections.

Animals↗
PubMed1997

Group A and group B streptococcal vaccine development. A round table presentation.

The data presented above provide a broad overview of ongoing work to develop vaccines against group A and group B streptococcal infections. The encouraging results of human trials with conjugate group B polysaccharide vaccines suggest that this approach will lead to a safe and effective method for preventing these devastating infections in newborn infants. The results of preclinical studies of the various strategies to develop group A streptococcal vaccines are also encouraging. Whether one approach will be more advantageous or efficacious than another will need to await clinical trials. Nevertheless, we predict that in the next decade we will make significant strides in preventing streptococcal infections and their complications.

Adhesins, Bacterial↗
PubMed1997

Conversion of M serotype 24 of Streptococcus pyogenes to M serotypes 5 and 18: effect on resistance to phagocytosis and adhesion to host cells.

In this study, we utilized recombinant strains expressing the M5 and M18 proteins and M- mutants of group A streptococci to compare the abilities of these M proteins to confer resistance to phagocytosis and to mediate adhesion to host cells. The data indicate that the M5 and M18 proteins can confer resistance to phagocytosis, that fibrinogen is required for this resistance, and that these M proteins can mediate adhesion to HEp-2 cells.

Antigens, Bacterial↗
PubMed1996

Recombinant, octavalent group A streptococcal M protein vaccine.

One of the major obstacles to the development of group A streptococcal M protein vaccines is the multiplicity of M serotypes expressed by these organisms. In this study, we have constructed a recombinant, hybrid M protein that contains type-specific aminoterminal fragments of eight different M proteins. We show that the purified hybrid recombinant protein is immunogenic in rabbits and evokes antibodies that react with native M proteins from the respective streptococcal serotypes. In addition, the immune sera evoked by the octavalent protein opsonized six of the eight serotypes of streptococci, indicating that the majority of the M protein fragments contained protective epitopes that retained their native conformations in the hybrid protein. None of the antisera raised against the octavalent protein crossreacted with human heart tissue. These studies indicate that multivalent, hybrid M proteins may be used to elicit broadly protective immune responses against multiple serotypes of group A streptococci.

Animals↗
PubMed1996

The reemergence of serious group A streptococcal infections and acute rheumatic fever.

Acute rheumatic fever and life-threatening group A streptococcal infections have reemerged during the past 15 years to once again become a serious health threat in the developed countries of the world. Reports of outbreaks of acute rheumatic fever in many parts of this country and others have shattered the complacency that the health-care community had acquired related to this devastating sequela of streptococcal pharyngitis. Invasive streptococcal infections, often associated with loss of limbs of life despite optimal antibiotic therapy, have underscored the potential virulence of these organisms. A new clinical entity, streptococcal toxic shock syndrome, has emerged as a consequence of the new invasive strains of group A streptococci. In this article, the authors summarize the recent changes in the epidemiology of group A streptococcal infections and rheumatic fever and review the potential reasons for the increased virulence of these organisms. In addition, they discuss prospects for a streptococcal M protein vaccine designed to control these infections and their sequelae.

Anti-Bacterial Agents↗
PubMed1996

Hyaluronate capsule and surface M protein in resistance to opsonization of group A streptococci.

The major virulence determinant of group A streptococci is the ability to resist opsonization and phagocytic ingestion. The present studies were performed to compare the mechanisms of resistance to opsonization of type 18 and type 24 streptococci and to determine the relative roles of M protein-fibrinogen interaction and the hyaluronate capsule in preventing phagocytic ingestion and killing. By use of parent strains and acapsular transposon mutants in the presence and absence of fibrinogen, we show that type 18 and type 24 streptococci rely on somewhat different mechanisms for resistance to opsonization. Type 24 streptococci bound fibrinogen avidly to their surfaces, and encapsulated organisms were completely resistant to opsonization only in the presence of fibrinogen. In contrast, type 18 streptococci bound 10-fold less fibrinogen than type 24 streptococci and were fully resistant to phagocytosis only when they expressed capsule. The general structural characteristics of the amino-terminal halves of type 18 and type 24 M proteins differed in that type 18 M protein contained only one complete B repeat, whereas type 24 M protein contained five complete B repeats, a structural difference which could potentially be related to the differences in fibrinogen binding between the two serotypes. Immunofluorescence assays of complement deposition were used in combination with 125I-C3 binding assays to show that encapsulated type 24 streptococci were fully resistant to opsonization by C3 only in the presence of plasma. Encapsulated and unencapsulated type 18 streptococci were equally opsonized by C3 in either plasma or serum, yet only encapsulated organisms resisted phagocytic killing in blood. The results of this study indicate that opsonization by C3 does not necessarily lead to phagocytic ingestion and that the hyaluronate capsule and M proteins are variably important in resistance to different group A streptococci to opsonization and phagocytic killing.

Antigens, Bacterial↗