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Biomedical subjects

M D Chapman

Publications and source records attributed to M D Chapman.

At least 127 records · Page 7Linked to original sources
PubMed1991

Asthma in Tanta, Egypt: serologic analysis of total and specific IgE antibody levels and their relationship to parasite infection.

The relationship between asthma, IgE and parasite infection was compared in 68 randomly selected patients with asthma and 37 nonasthmatic controls living in Tanta, Egypt. Sera were assayed for total IgE and for IgE antibodies to inhaled allergens (mite, cat, cockroach, ryegrass, ragweed and 3 fungi) and to parasite antigens (Schistosoma mansoni and Brugia malayi). Parasite infection was determined by microscopic examination of stool specimens. Total IgE levels were significantly higher in patients with asthma (geometric mean 909 IU/ml), than in controls (geometric mean 145 IU/ml, p less than 0.001). The high IgE levels correlated with parasite infection and the presence of IgE antibodies to S. mansoni antigens, which were also elevated compared to controls. The prevalence of allergen-specific IgE antibodies among Egyptian asthmatics was low by comparison with 'Western' asthmatics, but nonetheless higher than among Egyptian controls. A radioallergosorbent test (RAST) values of greater than 40 U/ml to any allergen was found in 19/68 (28%) sera from the asthma group, as compared to only 1/37 (3%) sera from controls (p less than 0.001). The highest RAST values were to dust mite (Dermatophagoides pteronyssinus and D. farinae) allergens, followed by rye grass and ragweed allergens. The results suggest that in this area of Egypt, several factors may influence the development of asthma, including nonspecific activation of IgE and/or inflammatory mechanisms by helminth parasites and sensitisation to environmental allergens.

Adolescent↗
PubMed1991

Airborne cat allergen (Fel d I). Environmental control with the cat in situ.

In a house with a cat furnishings, air-exchange rate, and the cat are all thought to influence airborne cat allergen. We carried out experiments using two separate rooms, modifying the environment, applying different cleaning techniques, and washing the cat, to analyze these sources and to design methods of reducing airborne allergen. Airborne measurements were made with a cascade impactor and a two-site monoclonal antibody-based immunometric assay for cat allergen Fel d I. Within 30 min of entering a 30-m3 clean room the cat itself was found to increase airborne Fel d I by 30 to 90 ng/m3. Following serial weekly washing of the cat this increase was reduced to less than or equal to 7 ng/m3, with a more marked fall in small particles (less than or equal to 2.5 microns diameter) from 9.5 to less than or equal to 0.4 ng/m3. To study the influence of the room design we kept the cat in a room of 33 m3 for 20 h/day and modified the room. This room was studied with or without furnishings and with air-exchange rates of 0.2 or 2.4 air changes per hour. Both low ventilation rate and furnishings increased the level of Fel d I measured 1 h after the cat was removed. However, the most striking finding was that the carpet accumulates cat allergen at approximately 100 times the level for a polished floor, that is, approximately 100 micrograms/day Fel d I compared with approximately 0.5 micrograms/day Fel d I.(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗
PubMed1991

Specific allergens evoking immune reactions in the lung: relationship to asthma.

Over the last 20 yrs our understanding of the relationship of allergens to asthma has changed completely. This is due to several interrelated developments: firstly, it is clear that bronchial hyperreactivity can be increased by allergen exposure and that it is at least in part reversible; secondly, it is now generally accepted that asthma involves inflammation of the bronchi in which eosinophils play an important role; thirdly, there are a large number of studies demonstrating an epidemiological relationship between immediate hypersensitivity to dust mites and asthma; finally, it has been shown that natural exposure to dust mite allergens is very different from bronchial provocation. Together these findings have lead to the view that indoor allergens can play a major role in causing bronchial inflammation with consequent bronchial reactivity and that this is usually not apparent to the patient. Recently three studies in the USA have established that immunoglobulin E (IgE) antibodies to common inhalants can also be important risk factors for acute asthma. In these studies both dust mites and pollens were significant, but cat and cockroach allergy were also important. The results imply that the management of all asthma requires evaluation of the role of immediate hypersensitivity and that treatment of inflammation in the lungs should include both anti-inflammatory drugs and allergen avoidance.

Allergens↗
PubMed1990

Aspergillus fumigatus allergen I, a major IgE-binding protein, is a member of the mitogillin family of cytotoxins.

A major 18-kD IgE-binding protein from Aspergillus fumigatus (Asp fI) has been purified. Partial amino acid sequencing of Asp f I showed extensive sequence homology (95%) between Asp fI and a cytotoxin (mitogillin) produced by A. restrictus. Crossinhibition radioimmunoassay using murine monoclonal antibody and human IgG and IgE antibodies showed that Asp fI and mitogillin were antigenically indistinguishable. Furthermore, both proteins inhibited protein synthesis in vitro by greater than 90%. Asp fI was expressed in A. fumigatus but not in seven other Aspergillus species. The results suggest that Asp fI could play a dual role in the pathogenesis of A. fumigatus-related diseases by promoting colonization through cytotoxic activity and by causing inflammatory reactions involving IgE antibodies.

Allergens↗
PubMed1990

Monoclonal antibodies directed against the galactose-binding lectin of Entamoeba histolytica enhance adherence.

The Entamoeba histolytica galactose-binding lectin is a surface glycoprotein composed of 170- and 35-kDa subunits. Inhibition of this lectin with galactose or anti-170 kDa subunit polyclonal antibody blocks amebic adherence to target cells and colonic mucin glycoproteins. We describe the properties of 10 mAb with specificity for the 170-kDa subunit. Based on competitive binding studies, six nonoverlapping antigenic determinants on the lectin were identified. The effect of the mAb on adherence of amebic trophozoites to both Chinese hamster ovary (CHO) cells and human colonic mucins was measured. Antilectin antibodies directed against epitopes 1 and 2 enhanced adherence, with the number of amebae having at least three adherent CHO cells increasing with the addition of epitope 1 mAb from 26 +/- 9 to 88 +/- 2% and the binding of colonic mucins increasing from 34 +/- 1 to 164 +/- 3 pg/10(5) amebae. Antibody-enhanced adherence remained 90 to 100% galactose inhibitable, occurred at 4 degrees C and was not Fc mediated. Univalent Fab fragments of epitope 1 mAb augmented mucin binding by 238% and CHO cell adherence by 338%. The binding of purified lectin to CHO cells was increased from 1.1 +/- 0.1 to 2.4 +/- 0.3 ng/10(3) CHO cells by mAb directed to epitope 1, demonstrating that enhanced adherence was due to direct activation of the lectin. mAb to epitope 3 bound to the lectin only upon its solubilization from the membrane and had no effect on adherence. Adherence to CHO cells and mucins was inhibited from 50 to 75% by mAb to epitopes 4 and 5; epitope 6 mAb inhibited amebic adherence to CHO cells but not mucins. The pooled sera from 10 patients with amebic liver abscess blocked the binding to the 170-kDa subunit of mAb directed to all six epitopes. Striking individual variations in the effects of immune sera on adherence were observed. Although the sera of all 44 South African patients with amebic liver abscess had high titer anti-lectin antibodies, 16 patients' sera significantly (more than 3 SEM) enhanced adherence whereas 25 patients' sera significantly inhibited adherence. Antilectin antibodies exert profound functional effects on the interaction of E. histolytica with target cells and human colonic mucins. Exploration of the clinical consequences of adherence-enhancing and inhibitory antibody responses may give insight into the role of antilectin antibodies in immunity to invasive amebiasis.

Amebiasis↗
PubMed1990

Conformational stability of B cell epitopes on group I and group II Dermatophagoides spp. allergens. Effect of thermal and chemical denaturation on the binding of murine IgG and human IgE antibodies.

The conformational stability of B cell epitopes on the 25-kDa group I and 14-kDa group II mite allergens was compared by using heat-treated or chemically denatured allergens to inhibit the binding of native 125I allergens to murine mAb or to human IgE antibodies. Structural changes after treatment were assessed by SDS-PAGE and circular dichroism spectroscopy. Heating for 1 h at greater than 75 degrees C, treatment at pH 2.0 or pH 12.0, or with 6M guanidine or 6M urea, reduced the binding of the group I allergens to mAb or IgE antibodies by 10- to 1000-fold. The group II allergens were heat stable and even after prolonged heat treatment (5 h at 75 degrees C or 30 min at 100 degrees C) their antibody binding activity was reduced by less than twofold. The group II allergens were also resistant to pH and to denaturation with 6M guanidine. However, after reduction and alkylation, antibody binding sites on both the group I and group II allergens were destroyed. Reduction of disulfide bonds with 2-ME caused a marked shift in the molecular mass of group I allergens on SDS-PAGE, from 25 kDa to 28-31 kDa. Reduction and alkylation also generated two high m.w. forms of Der p I and Der f I. After heating (100 degrees for 30 min), both Der f I and Der f II retained significant secondary structure, as judged by circular dichroism spectroscopy, but on reduction they showed the typical spectra of fully denatured proteins (greater than 85% random structure). The results show clear differences between the susceptibility of B cell epitopes on the group I and group II allergens to denaturation. Despite these differences in stability, both allergens are equally potent immunogens for IgE antibody responses in man. The results support the view that the physical properties of allergens (low m.w. and solubility), limiting low dose exposure (1 to 10 ng/day), and host genetic and immunoregulatory processes, are more important than gross structural features in the induction and maintenance of IgE antibody responses.

Alkylation↗
PubMed1990

Recent progress in mite allergen immunochemistry.

The successful purification of several mite allergens within the last few years has considerably enhanced our understanding of mite allergen immunochemistry. The role of these glycoproteins in stimulating human IgE ab and their role as immunogens in mice and rabbits has been studied extensively in a number of laboratories worldwide. In particular, purified allergens have facilitated the production of murine IgG Mabs that have been used to purify mite allergens by affinity chromatography; to investigate the diversity of antigenic sites on purified allergens; and to develop Mab based immunoassays for measuring allergen concentrations in dust samples and extracts. Full amino acid sequencing of several mite allergens is now in progress together with efforts to identify antigenically important peptide fragments. Such investigations are aimed to further increase our knowledge of humoral and cellular immune responses at the molecular level. For years, pollen counts have been used to judge airborne pollen allergen levels and to predict, in turn, the severity of symptom days for patients with hay fever. In contrast, simple methods for measuring dust allergens (e.g., mite allergen) have not been available. The development of Mab immunoassays, which can be converted from radiolabeled to enzyme labeled or fluorescence labeled assays, should provide rapid and quantitative measurements of specific mite allergen levels in house dust. Not only can such measurements provide useful clinical information in judging the exposure of patients to mite allergen, but the effectiveness of allergen avoidance regimes can be monitored objectively. By measuring the concentration of specific allergens in extracts, these assays could significantly improve efforts to standardize extracts used for diagnosis and treatment.

Allergens↗
PubMed1990

Pathogenic and nonpathogenic strains of Entamoeba histolytica can be differentiated by monoclonal antibodies to the galactose-specific adherence lectin.

Entamoeba histolytica infection results in either asymptomatic colonization or invasive colitis and liver abscess. E. histolytica isolates from patients with invasive disease have characteristic isoenzyme profiles (pathogenic zymodemes), suggesting a role for parasite factors in determining the severity of infection. A galactose-specific cell surface lectin from a pathogenic zymodeme was shown to mediate in vitro adherence to human colonic mucins and contact-dependent killing of target cells. Six nonoverlapping antigenic determinants were identified on the 170-kilodalton heavy subunit of the pathogenic lectin. Anti-lectin monoclonal antibodies (MAb) directed against epitopes 1 and 2 enhanced adherence whereas MAb to epitopes 3 through 6 either inhibited or had no effect on adherence. We tested 50 pathogenic and nonpathogenic strains for reactivity to these anti-lectin MAb by radioimmunoassay. MAb to epitopes 1 through 6 reacted in the radioimmunoassay with all 16 pathogenic zymodeme strains tested. In contrast, only MAb to epitopes 1 and 2 bound to the lectin from nonpathogenic strains. Western immunoblots with anti-lectin antibodies showed that the 170-kilodalton heavy subunit was present in the nonpathogenic amebae. Adherence of the nonpathogenic SAW 760 strain to human erythrocytes was enhanced by MAb to epitope 1 and blocked by galactose, confirming the presence of a functionally active lectin. A lectin radioimmunoassay based on MAb to epitopes 1 and 3 proved to be a simple and rapid method to distinguish pathogenic from nonpathogenic amebae in culture. Further exploration of the functional consequences of the antigenic differences demonstrated for the lectin may lead to a better understanding of its role in pathogenesis.

Animals↗
PubMed1990

Airborne concentrations and particle size distribution of allergen derived from domestic cats (Felis domesticus). Measurements using cascade impactor, liquid impinger, and a two-site monoclonal antibody assay for Fel d I.

The recent development of a sensitive two-site monoclonal antibody immunoassay for the major cat allergen (Fel d I) has made it possible to make accurate measurements of airborne cat allergen using low volume samplers that do not disturb the room. Houses with cats had from 2 to 20 ng Fel d I/m3 air compared with less than 0.2 ng/m3 in houses without cats. Using a cascade impactor and a multistage liquid impinger, the particle size distribution of airborne Fel d I in nine houses was 75% on particle greater than or equal to 5 microns in diameter and 25% (range, 10 to 62%) on particles less than or equal to 2.5 microns. In a cat vivarium with 12 cats, the air contained 40 ng Fel d I/m3, but less than 2% was detected on particles less than or equal to 2.5 microns. The air exchange rate in the vivarium (approximately 15 changes/h) appears to be the major difference from domestic houses (less than 0.5 changes/h). Repeated studies in one house confirmed a very high proportion (approximately 60%) of Fel d I on small particles. During domestic cleaning, the levels of small particle allergen in this house approached those produced by a nebulizer for bronchial provocation, i.e., 40 ng/m3. These results show unequivocally that significant airborne Fel d I is associated with small particles, which remain airborne for long periods. These findings are strikingly different from previous results obtained with airborne dust mite allergen. The results provide an explanation for the distinctive rapid onset of asthma or rhinitis in patients allergic to cats and a basis for designing a policy to reduce airborne allergen in houses with cats.

Air Conditioning↗
PubMed1989

A two-site monoclonal antibody ELISA for the quantification of the major Dermatophagoides spp. allergens, Der p I and Der f I.

A two-site monoclonal antibody (Mab) ELISA was developed to measure the Group I allergens from Dermatophagoides spp., Der p I from D. pteronyssinus and Der f I from D. farinae. Species-specific Mabs were used to coat microtiter plates which were then incubated with allergen or house dust extracts. Bound allergen was detected using a biotinylated Mab which recognized a common epitope on both Der p I and Der f I, followed by the addition of streptavidin-peroxidase and ABTS/H2O2 substrate. The assay had low non-specific binding (approximately 0.08 absorbance units) and had a sensitivity of 5 ng/nl for aqueous allergen extracts (equivalent to 0.1 microgram allergen/g dust). 53 dust samples were assayed using the Mab ELISA and an RIA previously described using 125I-labelled Mab. The results showed a very good quantitative correlation between the assays (r = 0.96, p less than 0.001 for Der p I; r = 0.92, P less than 0.001 for Der f I). A further 132 dust samples from a different geographical areas were also assayed by both methods and gave correlation coefficients of 0.90 (P less than 0.001) and 0.86 (P less than 0.001) for Der p I and Der f I, respectively. The Mab ELISA will be useful in epidemiological studies of allergic asthma, both in the assessment of levels of dust mite allergen present in houses and the efficacy of allergen avoidance regimes.

Allergens↗
PubMed1989

Subunit structure of the galactose and N-acetyl-D-galactosamine-inhibitable adherence lectin of Entamoeba histolytica.

The galactose and N-acetyl-D-galactosamine-inhibitable adherence lectin of Entamoeba histolytica is a cell surface protein which mediates parasite adherence to human colonic mucus, colonic epithelial cells, and other target cells. The amebic lectin was purified in 100-micrograms quantities from detergent-solubilized trophozoites by monoclonal antibody affinity chromatography. The adherence lectin was purified 500-fold as judged by radioimmunoassay. The nonreduced lectin had a molecular mass of 260 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of pH 6.2. The amebic lectin reduced with beta-mercaptoethanol consisted of 170- and 35-kDa subunits. Both subunits could be labeled on the cell surface with 125I, and both were metabolically labeled with [3H]glucosamine. The amino termini of the subunits had unique amino acid sequences, and polyclonal antisera to the heavy subunit did not cross-react with the light subunit. The yield of phenylthiohydantoin derivatives from the second and third positions in the sequence of the heavy and light subunits gave a molar ratio of one 170- to one 35-kDa subunit. Antibodies directed to the heavy subunit inhibited amebic adherence to Chinese hamster ovary cells by 100%, suggesting that the heavy subunit is predominantly responsible for mediating amebic adherence.

Acetylgalactosamine↗
PubMed1989

The effect of cat removal on allergen content in household-dust samples.

To evaluate the effect of cat removal on cat-allergen content in the home, serial house dust samples were collected from 15 homes during a 9- to 43-week period after cat removal. Samples were obtained with a hand-held vacuum cleaner, and allergen content was quantitated by a radioimmunoassay specific for the major cat allergen, Fe1 d I. Baseline Fe1 d I content ranged from 7.8 Food and Drug Administration units per gram of dust to 436.7 U/gm (median 61.2 U/gm), consistent with levels found in homes with a pet cat. Fe1 d I levels declined gradually in most homes, and by 20 to 24 weeks after cat removal, eight of 15 reached levels consistent with levels found in control homes without cats. In two of those homes, allergen levels fell much more rapidly after aggressive environmental control measures were undertaken. In the other seven homes, however, the decline occurred at a much slower rate, with three homes demonstrating persistent elevations in Fe1 d I content for 20 or more weeks. These data demonstrate that the task of allergen elimination from an indoor environment is extremely difficult, even when the source of a specific allergen can be identified and removed.

Allergens↗
PubMed1989

Epidemiology of acute asthma: IgE antibodies to common inhalant allergens as a risk factor for emergency room visits.

In recent years the morbidity and mortality of asthma has increased, although the etiology is still poorly understood. Most patients with asthma suffer acute attacks that are commonly treated in hospital emergency rooms (ER). In the present study, asthma in adults was studied with acute attacks as a marker for the disease; 102 patients first observed at a university hospital ER with acute airway obstruction were compared to 118 patients observed at the same ER with any diagnosis other than shortness of breath to evaluate allergy as a risk factor for asthma in adults. Sera were assayed for IgE antibody (Ab) to dust mites, cockroach, cat dander, and grass and ragweed pollen. The results demonstrate that in adults younger than 50 years of age, the prevalence of IgE Abs was fourfold greater among subjects with asthma than among control subjects (46/67 versus 12/81; odds ratio, 10.1; 95% confidence interval, 4.9 to 20.7). The population attributable risk for the presence of IgE Ab to one of the five allergens was greater than 50%. Among individuals older than 50 years of age, the prevalence of serum IgE Abs was not significantly increased among patients with acute airway obstruction. In the whole group, the prevalence of IgE Abs to different allergens demonstrated significant seasonal and socioeconomic differences, suggesting that the associated risk is related to exposure to those allergens. The results establish that, with acute attacks of asthma as a marker for adult asthma, the presence of serum IgE Abs to common inhalant allergens is a major risk factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Antigenic and structural analysis of group II allergens (Der f II and Der p II) from house dust mites (Dermatophagoides spp).

Monoclonal antibody affinity chromatography was used to purify two homologous mite allergens, Der f II from Dermatophagoides farinae and Der p II from D. pteronyssinus. They have the same molecular weight (MW) (15 kd) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, they have similar amino acid compositions, and their N-terminal amino acid sequences differ in only four of the first 35 residues. An excellent correlation was observed between IgE antibody to Der f II and Der p II measured in sera from 65 mite-allergic patients (r = 0.94; p less than 0.001) and between quantitative intradermal skin tests to both allergens. A third allergen (Der f III, MW 29 kd) was purified from D. farinae by repeated gel filtration. In sera from 51 mite-allergic patients, IgE antibody to Der f II, Der f III, and previously purified Der f I (MW 24 kd) was detected in 92%, 16%, and 78% of the sera by radioimmunoassay, respectively. Most patients, 41/51 (80%), demonstrated IgE antibody to more than one allergen. With monoclonal antibodies fully cross-reactive with Der f II and Der p II, a two-site immunoassay was developed for measuring absolute quantities (nanograms or micrograms) of these allergens. In extracts rich in mite-fecal material (n = 5), Der f I and Der p I (group I allergens) and Der f II and Der p II (group II allergens) were measured in ratios of 11:1 to 35:1. Lower ratios (1.1:1 to 7:1) were observed in mite body extracts (n = 6). These experiments clearly define a second group of major dust mite allergens that demonstrate extensive structural and antigenic homology.

Allergens↗
PubMed1988

Monoclonal antibodies to the major feline allergen Fel d I. II. Single step affinity purification of Fel d I, N-terminal sequence analysis, and development of a sensitive two-site immunoassay to assess Fel d I exposure.

Two mAb were used to develop new techniques for the purification and quantitation of the major feline salivary allergen, Felis domesticus allergen I (Fel d I). The allergen was purified from aqueous house dust extract with a high Fel d I content by affinity chromatography over a monoclonal immunosorbent and elution with 4 mM HCl, pH 2.5. This single step procedure gave 40 to 50% recovery of 90% pure allergen which, following final purification by size exclusion HPLC, showed a single line on immunodiffusion and crossed immunoelectrophoresis against monospecific anti-Fel d I and polyclonal anti-cat dander antibodies. The m.w. of native Fel d I was 39,000 on size exclusion HPLC, and 17,000 under nonreducing conditions on gel electrophoresis. The N-terminal amino acid sequence (33 residues) showed no homology with other known protein sequences. The combination of the SDS-PAGE and N-terminal sequence data suggests that Fel d I is a non-covalently linked homodimer. A two-site RIA was developed using mAb directed against different epitopes on Fel d I. This assay was species-specific, highly sensitive (0.0004 U/ml), and showed an excellent correlation with a polyclonal inhibition RIA (n = 27, r = 0.93, p less than 0.001). Cat allergen extracts used for immediate skin tests showed marked differences in Fel d I content (from 0.1 to 30 U/ml). Consistently high Fel d I levels were found at monthly intervals in six dust samples from four houses with cats (10 to 100 U/g of dust). Comparisons of Fel d I and mite and pollen allergen levels showed that house dust can contain greater than 100 micrograms/g of either of these allergens and is a potent source of foreign environmental antigens. Monoclonal affinity chromatography provides a major breakthrough in the purification of Fel d I, from a source material that would otherwise have been considered impossible (house dust). The mAb assay for Fel d I is both more sensitive and more easily standardized than existing techniques. These techniques will allow full structural and antigenic analysis of Fel d I and more detailed studies on the relationship between cat antigen exposure and the development of asthma.

Allergens↗