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D B Young

Publications and source records attributed to D B Young.

At least 145 records · Page 8Linked to original sources
PubMed1988

Orientation of epitopes influences the immunogenicity of synthetic peptide dimers.

The immunogenicity of synthetic peptide dimers based on epitope sequences derived from the mycobacterial 65-kDa antigen and the foot and mouth disease virus (FMDV) VP1 protein was examined in inbred mice. The analysis was directed towards the potential helper role of a T cell stimulatory mycobacterial epitope (65-85) with respect to poorly immunogenic sites either from the same molecule (422-436) or from VP1 (141-160). The 65-85 repeat homodimer induced an antibody response in CBA/ca but not in C57BL/6 mice, both nonresponders to the 65-85 monomer, and amplified the antibody response in BALB/c, monomer-responder mice. Analysis of the immunogenicity of hybrid dimers in BALB/c mice showed that the orientation of peptides within the dimer is critical for the extent of the produced antibody response. Only the 422-436/65-85 but not the 65-85/422-436 induced antibodies binding to the 422-436 sequence which was nonimmunogenic when injected either as a monomer or dimer. Despite the striking difference in immunogenicity, both tested hybrid dimers reacted equally in the solid-phase immunoassay with antisera raised to 65-85-dimer or 422-436/65-85 peptides or with a monoclonal antibody to the 422-436 epitope. The described differences in antibody responsiveness also cannot be attributed merely to the extent of T cell stimulation since the proliferative responses were uniformly expressed for all relevant combinations of peptides. Antisera to 65-85 dimer and 422-436/65-85 hybrid also reacted with the native 65-kDa protein. Furthermore, the production of FMDV-neutralizing antibodies in response to the 141-160 (VP1-derived)/65-85 hybrid peptide in 141-160 nonresponder B10.D2 mice also confirmed the helper activity of the 65-85 epitope. Thus, combining heterologous peptides with the N-terminal of the mycobacterial 65-85 sequence may be generally applicable for the potentiation of peptide vaccines.

Animals↗
PubMed1988

Stress proteins and the immune response to mycobacteria--antigens as virulence factors?

The immune response to mycobacterial infection includes pathogenic as well as protective activities. It is possible that different types of immune responses are associated with recognition of different antigenic determinants. Amongst the antigens which are prominent in antibody and T cell recognition of mycobacteria, we have identified members of highly conserved stress protein families. Mapping of antigenic determinants on stress proteins shows that both species-specific and conserved regions of these proteins can take part in immune recognition. Induction of an immune response to conserved, "self-like", determinants on stress proteins could play a role in the immunopathology associated with chronic mycobacterial infections.

Amino Acid Sequence↗
PubMed1988

Immunoblotting and the immune response to leprosy.

Immunoblotting has provided a powerful and effective approach to dissection of the immune response to mycobacterial antigens in a situation in which the availability of isolated antigenic components is severely limited. The basic approach of blotting on to a solid-phase support has been used in combination with SDS/polyacrylamide-gel electrophoresis, t.l.c., recombinant DNA technology and T-cell cloning in order to carry out a comprehensive analysis of glycolipid and protein antigens involved in the immune response to mycobacterial infection.

Antigens, Bacterial↗
PubMed1988

Verapamil alters the relationship between renal perfusion pressure and glomerular filtration rate and renin release: the mechanism of the antihypertensive effect.

The renal hemodynamic and renin release responses to verapamil were analyzed in order to determine if the antihypertensive action of the calcium entry blocker could be due to its renal effects. Hemodynamic and renin release measurements were compared in a control group of anesthetized rabbits (N = 9) and in a group of rabbits given verapamil (N = 10) (200 micrograms/kg i.v. initially, 4 micrograms/kg/min thereafter) starting 30 min before data collection. Measurements were made over a range of controlled renal perfusion pressure from 100 to 40 mm Hg. The renal blood flow (RBF) at 100 mm Hg of the verapamil-treated group was 18% greater than (p less than 0.02) that of the control group, while the glomerular filtration rate (GFR) was 51% greater than (p less than 0.001) that of the control group. RBF and GFR autoregulation was highly effective in the control group down to 80 mm Hg, but both variables were poorly regulated in the verapamil group. The filtration fraction of the treated group was 36.9 +/- 1.5% versus 28.5 +/- 1.6% in the control group (p less than 0.003) at 100 mm Hg, and the filtration fraction of the treated group remained significantly greater down to 40 mm Hg. Renin release rates of the two groups were similar at the 100 mm Hg pressure level, but the increase in release due to the progressive reduction in perfusion pressure was significantly greater in the treated group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Biological activity of protein antigens isolated from Mycobacterium tuberculosis culture filtrate.

Mycobacterium tuberculosis culture filtrate (MTCF) protein antigens were isolated from mid-logarithmic-phase cultures grown in liquid medium and examined by high-pressure liquid chromatography and Western blot (immunoblot) analysis. A major protein band with a molecular mass of about 68 kilodaltons (kDa) and several fainter bands in the 38- and 24-kDa range were observed. The MTCF protein produced a significant delayed footpad hypersensitivity response in Mycobacterium bovis BCG-vaccinated C57BL/6 mice, comparable to that observed with standard purified protein derivative (PPD). The same proteins induced a blastogenic response in tuberculin-sensitive human peripheral blood monocytes and in T-cell clones developed from these cells. The proliferative responses to the MTCF antigens were equivalent to those observed following stimulation with PPD or M. tuberculosis sonic extracts. However, the MTCF sensitins were not recognized by five monoclonal antibodies directed against killed M. tuberculosis antigens in an enzyme immunoassay, although some response was seen with a monoclonal antibody (ML34) directed against M. leprae antigens. The ability of the MTCF to stimulate T-cell responses both in vivo and in vitro while not being recognized by antibodies directed against dead mycobacterial antigens suggests that they may be of interest as potential protective immunogens.

Animals↗
PubMed1988

Generation and characterization of monoclonal antibodies to 28-, 35-, and 65-kilodalton proteins of Mycobacterium tuberculosis.

Three monoclonal antibodies (H60.15, H61.3, and H105.10) directed to protein antigens of Mycobacterium tuberculosis were obtained and characterized. H60.15 recognizes a protein with a molecular mass of 28 kilodaltons (kDa) with broad cross-reactivity on a panel of 12 species and strains of mycobacteria. H61.3 reacts with a 35-kDa protein present in M. tuberculosis, Mycobacterium bovis BCG, and M. africanum. On the basis of the antigen molecular masses and competition experiments with other monoclonal antibodies, H60.15 and H61.3 seem to be the first described monoclonal antibodies to these M. tuberculosis proteins. H105.10 binds to the cross-reactive 65-kDa protein present in mycobacteria. Epitope mapping of H105.10 was performed by using the M. leprae DNA sublibrary available in bacteriophage lambda gt11 for this antigen and revealed that its epitope resides in the region from amino acids 20 to 54. The 28-, 35-, and 65-kDa antigens isolated by immunoblotting and presented on nitrocellulose to pleural effusion T cells from tuberculosis patients induced a proliferative response, indicating the presence of T-cell epitopes. These observations indicate that two protein antigens should be added to the list of antigens detectable in M. tuberculosis by monoclonal antibodies. The common feature of such proteins, the elicitation of an immune response of limited or broad cross-reactivity for mycobacteria, encourages the search for their role in the pathogenesis of mycobacterioses.

Animals↗
PubMed1988

Specificity of antibodies to immunodominant mycobacterial antigens in pulmonary tuberculosis.

A serological survey was performed in groups of patients with active sputum smear-positive or smear-negative pulmonary tuberculosis, healthy household contacts, and controls. Sera were tested for titers of antibodies which bound to each of five purified mycobacterial antigens by enzyme immunoassay and for competition of binding to single epitopes, using six radiolabeled monoclonal antibodies directed toward corresponding molecules. The evaluation of diagnostic specificity was based on a positive score represented by titers above the cutoff point of 2 standard deviations above the mean titer of a control group. For smear-positive samples, the best sensitivity (83%) was achieved by exclusive use of the 38-kilodalton (kDa) antigen or its corresponding monoclonal antibodies. For smear-negative samples, levels of antibodies binding to the 19-kDa antigen showed a lower sensitivity of 62% compared with the control group or 38% compared with the contact group. Titers of antibody binding to the 14-kDa antigen were raised in Mycobacterium bovis BCG-vaccinated contacts, indicating that the greatest potential of this antigen may be in the detection of infection in a population for which tuberculin testing is unreliable. The results demonstrated the differing antibody responses to each of the tested antigens and distinct associations with the stage of infection or disease.

Antibodies, Bacterial↗
PubMed1988

Long-term hypotensive effect of beta-agonist in conscious dogs.

The purpose of this study was to investigate the arterial pressure response to long-term administration of beta-agonists in the chronically instrumented conscious animal model. Chronically instrumented dogs were given intravenous infusions of ritodrine (2 micrograms.kg-1.min-1) for a period of 2 wk. Several cardiovascular and renal parameters were monitored before, during, and after the ritodrine infusion, and renal function curves were constructed. After the 1st wk of infusion, a new steady state was reestablished, and this was characterized by hypotension, reduced plasma protein concentration, elevated cardiac output, expanded extracellular fluid space, and near normal levels of activity of renin-angiotensin-aldosterone systems. The renal function curve during ritodrine infusion shifted to the left with no change in slope. We propose the following: 1) the persistence of hypotension is most probably related to the resetting of the arterial pressure-kidney blood volume servocontrol mechanisms, and 2) the persistent elevation of cardiac output and reduction in peripheral resistance are most probably related to increased oxygen and nutrient demand during beta-agonist infusions.

Aldosterone↗
PubMed1988

Impaired control of renal hemodynamics and renin release during hyperkalemia in rabbits.

We analyzed the changes in control of renal hemodynamics and renin release resulting from hyperkalemia in the rabbit. Plasma potassium activity was maintained at a controlled elevated level by intravenous infusion of KCl. The potassium activity of the control group (n = 23) averaged 3.20 +/- 0.06 meq/l and that of the hyperkalemic group (n = 13) averaged 5.80 +/- 0.13 meq/l. Renal blood flow (RBF), glomerular filtration rate (GFR), and renin release were measured over a range of renal perfusion pressures achieved by constriction of the suprarenal aorta. The control group's RBF and GFR exhibited excellent autoregulatory capability from 100 to 80 mmHg. However, significant impairment of autoregulation was apparent in the hyperkalemic group. At 100 mmHg, RBF and GFR in the hyperkalemic group averaged 33 and 34% greater, respectively, than those of the control group (P less than 0.005); both variables in the hyperkalemic group were greater than the values of the control group over the autoregulatory range (100-80 mmHg). The renin release values for the two groups were not different at the 100-mmHg pressure level, although renin release of the hyperkalemic group increased to higher levels than those of the control group as perfusion pressure was reduced. At the 70- and 60-mmHg levels renin release from the hyperkalemic group averaged approximately 300% greater than that of the control group (P less than 0.05). However, when expressed as percentage change, the stimulatory effect of hyperkalemia was not apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Quantitative analysis of aldosterone's role in potassium regulation.

Aldosterone is part of a complex system that regulates plasma potassium concentration by affecting the renal excretion of the ion as well as its distribution within the body. Because there are other components of the system, it has been difficult to determine the physiological significance of aldosterone in potassium regulation by attempting to study the hormone's effects in isolation. In this presentation a quantitative analysis of the potassium control system is used to provide information concerning the physiological role of aldosterone in potassium regulation under normal and pathological conditions, as well as during pharmacological interventions.

Aldosterone↗
PubMed1988

The antihypertensive mechanism of verapamil. Alteration of glomerular filtration rate regulation.

The renal hemodynamic and renin release responses to verapamil were analyzed to determine if the antihypertensive action of the calcium entry blocker could be due to its renal effects. Hemodynamic and renin release measurements were compared in a control group of nine anesthetized rabbits and in a group of 10 rabbits given verapamil (200 micrograms/kg i.v. initially, 4 micrograms/kg/min thereafter), starting 30 minutes before data collection. Measurements were made over a range of controlled renal perfusion pressure from 100 to 40 mm Hg. The renal blood flow at 100 mm Hg of the verapamil-treated group was 18% greater (p less than 0.02) than that of the control group, while the glomerular filtration rate was 51% greater (p less than 0.001) than that of the control group. Renal blood flow and glomerular filtration rate autoregulation were highly effective in the control group down to 80 mm Hg, but both variables were poorly regulated in the verapamil-treated group. The filtration fraction of the treated group was 36.9 +/- 1.5% versus 28.5 +/- 1.6% in the control group (p less than 0.003) at 100 mm Hg, and the filtration fraction of the treated group remained significantly greater down to 40 mm Hg. Renin release rates of the two groups were similar at the 100 mm Hg pressure level, but the increase in release due to the progressive reduction in perfusion pressure was significantly greater in the treated group than in the control group. At the 80 mm Hg pressure level, the mean release rate for the treated group was more than three times greater (p less than 0.05) than that of the control group. These findings demonstrate that verapamil is an effective renal vasodilator and that the effect is proportionally greater on the preglomerular than on the postglomerular resistance. This action could be the basis for its antihypertensive efficacy.

Animals↗
PubMed1988

Stress-induced proteins and the immune response to leprosy.

Mycobacterial antigens which play a major role in humoral and cell-mediated immune recognition are related to proteins which are induced in response to stress stimuli. The potential involvement of stress-induced proteins in infectious disease and in autoimmune responses is discussed.

Amino Acid Sequence↗
PubMed1987

Mapping of T cell epitopes using recombinant antigens and synthetic peptides.

Two complementary approaches were used to determine the epitope specificity of clonal and polyclonal human T lymphocytes reactive with the 65-kd antigen of Mycobacterium leprae. A recombinant DNA sublibrary constructed from portions of the 65-kd gene was used to map T cell determinants within amino acid sequences 101-146 and 409-526. Independently, potential T cell epitopes within the protein were predicted based on an empirical analysis of specific patterns in the amino acid sequence. Of six peptides that were predicted and subsequently synthesised, two (112-132 and 437-459) were shown to contain human T cell epitopes. This corroborated and refined the results obtained using the recombinant DNA sublibrary. Both of these regions are identical in M. leprae and M. tuberculosis and are distinct from the known B cell epitopes of the 65-kd protein. This combination of recombinant DNA technology and peptide chemistry may prove valuable in analysis of the cellular immune response to infectious agents.

Amino Acid Sequence↗
PubMed1987

Most Mycobacterium leprae carbohydrate-reactive monoclonal antibodies are directed to lipoarabinomannan.

Each of more than 30 monoclonal antibodies that had been raised against Mycobacterium leprae and previously classified as reactive with carbohydrate was shown to be directed against lipoarabinomannan, a prominent, highly pervasive, myo-inositol-phosphate-containing, cross-reactive antigen within the leprosy bacillus. Some of the antibodies preferentially bound to the lipopolysaccharide of M. leprae rather than to that of Mycobacterium tuberculosis, suggesting the presence of distinguishing structural features. The presence of alkali-labile inositol 1-phosphate in the lipopolysaccharide from M. tuberculosis and its apparent absence from the M. leprae product may account for the difference.

Antibodies, Monoclonal↗
PubMed1987

Screening of a recombinant mycobacterial DNA library with polyclonal antiserum and molecular weight analysis of expressed antigens.

A lambda gt11 expression library containing recombinant DNA from Mycobacterium tuberculosis was screened using hyperimmune anti-M. tuberculosis rabbit serum. The majority (22 of 29) of the recombinant clones selected by using polyclonal serum expressed three antigens that were previously identified by using mouse monoclonal antibodies, thus indicating the immunodominance of these proteins. Western blot analysis of the recombinant clones demonstrated that expression of these antigens is frequently independent of the formation of beta-galactosidase fusion proteins. The molecular weight of each expressed antigen can vary between clones and is not necessarily identical to that found in mycobacterial extracts.

Animals↗
PubMed1987

Analysis of the cardiovascular effects of arginine vasopressin in conscious dogs.

The effects of physiological elevations in arginine vasopressin on the cardiovascular system were studied in a group of nine conscious, chronically instrumented dogs. The animals were studied under normal conditions (plasma vasopressin, 4.1 +/- 0.4 pg/ml), after 24 hours of dehydration (plasma vasopressin, 7.3 +/- 1.5 pg/ml), after a 30-minute vasopressin infusion at 2.6 ng/kg/min (plasma vasopressin, 96.6 +/- 8.1 pg/ml). These increases in vasopressin concentration resulted in no change in arterial pressure and significant changes in the following: a 13 and 29% decrease in resting cardiac output during dehydration and acute infusion, respectively; a 26% reduction in heart rate during acute infusion; a 12 and 54% increase in total peripheral resistance during dehydration and acute infusion; a 16 and 22% reduction in mean circulatory filling pressure during dehydration and chronic vasopressin infusion. In addition, maximum pumping ability of the heart was reduced 16 and 31% during dehydration and acute infusion, respectively. These data suggest that elevations of vasopressin such as those occurring during dehydration or volume depletion potentially may affect cardiovascular performance by three mechanisms: greatly increasing resistance to flow, reducing heart rate, suppressing the pumping ability of the heart.

Animals↗
PubMed1987

A novel approach to the identification of T-cell epitopes in Mycobacterium tuberculosis using human T-lymphocyte clones.

Current approaches to the analysis of antigens involved in the cellular immune response to mycobacterial infection rely on the initial identification and isolation of molecular components using monoclonal antibodies. In order to overcome the constraints of this approach, we have utilized a procedure involving T-cell recognition of antigens fractionated by polyacrylamide gel electrophoresis (SDS-PAGE) and added to proliferation assays after blotting onto nitrocellulose membranes. Analysis of human T-cell responses to Mycobacterium tuberculosis and Mycobacterium bovis BCG by this procedure revealed distinctive patterns of reactivity to different molecular weight components indicative of the selective recognition of immunodominant and species-specific determinants. Human T-cell clones were subsequently derived, and SDS-PAGE immunoblotting was used to identify the antigen recognized by each clone. Three epitopes defined by individual T-cell clones were identified on separate polypeptides with molecular weights 16,000-18,000 (clone P53), 18,000-20,000 (clone P57) and 52,000-55,000 (clone P35). This study demonstrates the potential application of T-cell cloning in conjunction with SDS-PAGE immunoblotting for the dissection and analysis of the cellular immune response to pathogenic agents during human infection.

Antigens, Bacterial↗