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V Liebers

Publications and source records attributed to V Liebers.

At least 19 recordsLinked to original sources
PubMed2001

B-cell epitopes of the allergen Chi t 1.01: peptide mapping of epitopes recognized by rabbit, murine, and human antibodies.

BACKGROUND: Chi t 1.01, a hemoglobin of the midge Chironomus thummi thummi, is a widespread environmental and occupational allergen. The aim of the present investigation was to identify and compare peptides involved in B-cell epitopes of Chi t 1.01 recognized by 15 human IgE sera, six murine monoclonal antibodies (mAbs), and a polyclonal rabbit antiserum. METHODS: Synthetic peptides 19-21 amino acids long covering the whole Chi t 1.01-sequence were covalently coupled to activated paper disks as well as adsorbed to wells of immunoplates and used for enzyme-linked immunosorbent assay. For fine epitope mapping, we used overlapping synthetic octapeptides with one amino-acid offset. RESULTS: Peptides containing the amino acids 13-17, 23-29, and 40-50 were recognized by three of the mAbs, while three other mAbs reacting with none of the peptides obviously recognized conformational epitopes. Binding sites for rabbit antibodies and for human IgE antibodies were scattered over the whole molecule. The peptide 80-100 seemed to comprise at least one important IgE epitope. Depending on the method of antigen binding to the solid phase, differing results were obtained. CONCLUSIONS: Several linear epitopes in Chi t 1.01 are recognized by human IgE antibodies, by mAbs, and by polyclonal rabbit antibodies. In addition, the results indicate the presence of conformational epitopes.

Amino Acid Sequence↗
PubMed2001

Does IL-4 play a role in the expansion of V beta 8a T cell receptor-bearing cells?

BACKGROUND: Peripheral blood mononuclear cells (PBMC) of subjects allergic to the insect-derived allergen Chi t 1--9 are characterized by an allergen-induced pronounced proliferation and increased expression of activation markers (CD25, HLA-DR, CD23). T cell lines showed an elevated percentage of V beta 8a-positive cells following stimulation by Chi t 1--9. OBJECTIVE: The aim of the present study was to investigate whether V beta 8a dominance plays an important role in PBMC short-term cultures (24 h) as well. The role of exogenous added cytokines, especially IL-4, has been determined. METHODS: The T cell receptor repertoire was measured with 16 monoclonal antibodies to epitopes on the variable region of the beta chain by flow cytometry. Patients allergic to Chi t 1--9 were compared to nonallergic subjects as well as to subjects with other occupational allergies. In addition, cytokines were determined intracellulary by flow cytometry. Studies were performed with PBMC cultured for 24 h. RESULTS: After cultivation for 24 h without or with different stimuli (cytokines, allergen, phytohaemagglutinin), changes in the T cell receptor profile and the cytokine profile were measurable compared to the baseline value (without cultivation). Stimulation with IL-4 revealed increased percentages of V beta 8a-expressing cells in Chi t 1--9-sensitized patients. This IL-4-induced V beta 8a increase did not occur in PBMC from the two control subject groups (non-allergic and allergic to other allergens than Chi t 1--9). CONCLUSION In conclusion, the dominance of certain T cell receptor types seems to arise due to the exposure to specific allergens and cytokine production. Some T cell receptors are often affected, for example V beta 8a, whereas others only show minor variations. V beta 8a expression obviously plays an important role in Chi t 1-9 allergy.

Allergens↗
PubMed2000

T-cell receptor repertoire expression in workers with occupational asthma due to platinum salt.

There is a high incidence of asthma, rhinitis, conjunctivitis and contact urticaria in workers of precious metal refineries. Symptoms are closely associated with sensitization to halogenated platinum compounds, as assessed by skin-prick test. The aim of the present study was to examine the molecular mechanisms involved by describing the T-cell receptor (TCR) repertoire distribution of peripheral blood mononuclear cells (PBMCs) without and after in vitro stimulation with sodium hexachloroplatinate. PBMCs of 17 sensitized subjects with work-related asthma and a positive skin-prick test result to sodium hexachloroplatinate and of 15 nonexposed subjects were isolated and TCR expression determined by flow cytometry. Furthermore, the sodium hexachloroplatinate-mediated in vitro effects on the frequency of Vbeta-expressing T-cells, the proliferation response and the expression of cell surface molecules like CD71, CD25, CD95 and HLA-DR were studied. CD3-positive lymphocytes of platinum salt-sensitized workers had a significantly higher frequency of Valpha2a+, Vbeta11+ and Vbeta21.3+ T-cells than controls (p<0.01, p<0.01 and p<0.001 respectively). In vitro stimulation of PBMCs from platinum salt-sensitized as well as control subjects with sodium hexachloroplatinate increased the percentage of CD3-positive cells bearing specific TCRs, especially Vbeta5.3, Vbeta6.7, Vbeta8a, Vbeta20 and Vbeta21.3. This effect was time- and dose-dependent. The present results indicate that the frequencies of Valpha2a-, V11 and Vbeta21.3-bearing blood T-cells and platinum salt-induced lymphocyte proliferation are strongly enhanced in subjects who suffer from asthma due to platinum salt. In addition, in vitro stimulation with sodium hexachloroplatinate modulates the frequencies of certain T-cell receptor-bearing T-cells.

Adult↗
PubMed1998

Analysis of T-cell reactive regions and HLA-DR4 binding motifs on the latex allergen Hev b 1 (rubber elongation factor).

BACKGROUND: The rubber elongation factor in Hevea rubber (Hev b 1) is one of the important latex-allergenic proteins inducing the production of specific IgE antibodies in latex-exposed subjects. In addition, Hev b 1 induces lymphocyte proliferation responses. A study about detailed T-cell epitope analysis of major latex allergens has not been published yet. OBJECTIVE: The aim of this study was to define the T-cell reactive regions on the latex allergen Hev b 1. METHODS: Nine overlapping peptides with 19 or 17 amino acid lengths representing the complete sequence of Hev b 1 were used for T-cell epitope mapping. Peripheral blood mononuclear cells (PBMCs) of latex-sensitized patients and healthy subjects were isolated and stimulated with the synthetic peptides to determine the specific proliferation response. The examined patients were sensitized to latex by occupational exposure (n=14) and suffered from rhinitis, conjunctivitis, contact urticaria and/or asthma. Two control groups of non-sensitized subjects were studied, one occupationally exposed to latex (n=4), the other one not exposed to latex (n=4). RESULTS: Positive proliferation response induced by one or more peptides was detected in 10 of the latex-sensitized patients and in two of the latex-exposed non-sensitized subjects. Each patient exhibited an individual epitope reactivity pattern. The whole protein was found to be immunogenic, but the intensity of lymphocyte responses induced by the peptides was different. The majority of the patients' PBMCs (more than 66%) responded to the peptides 31-49 and 91-109. Using the peptide selection of Stille's algorithms, three epitopes were predicted covering region 38-74 and two others covering region 82-104; the two peptides 31-49 and 91-109 are part of these regions. A strong HLA-DR4Dw4 (DRB1*0401)-binding motif according to published DR4w4 binding motifs was predicted in the region of 102-110 including peptide 91-109 to which the majority of tested HLA-DR4-positive patients responded. CONCLUSIONS: Our data indicate that the whole 14 kDa protein Hev b 1 is immunogenic having regions that demonstrate individual and varying PBMC stimulation. Experimental data of T-cell reactive regions based on PBMC-stimulation complement the information on T-cell epitope prediction. In addition, the Hev b 1 molecule contains a HLA-DR4Dw4 (DRB1*0401)-binding motif.

Adult↗
PubMed1998

Exposure-response relationships of occupational inhalative allergens.

Only a few threshold limit values exist at present for allergens in the workplace known to cause bronchial asthma. This contrasts with the great number of occupational asthma cases observed in industrialized countries. Recently published studies provide clear evidence for exposure intensity response relationships of occupational allergens of plant, microbiological, animal or man-made origin. If allergen exposure levels fall short of determined limit values, they are not associated with an increased risk of occupational asthma. Corresponding data are available for wheat flour (1-2.4 mg/m3), fungal alpha-amylase (0.25 ng/m3), natural rubber latex (0.6 ng/m3), western red cedar (0.4 mg/m3) and rat allergens (0.7 microg/m3). It is suggested to stipulate legally binding threshold limit values (TLV/TWA) on this basis in order to induce more effective primary preventive measures. If no reliable data on the health risk of an occupational airborne noxa exist, the lowest reasonably practicable exposure level has to be achieved. Appropriate secondary preventive measures have to be initiated in all workplaces contaminated with airborne allergens. Verified exposure-response relationships provide the basis for risk assessment and for targeted interventions to reduce the incidence of occupational asthma also in consideration of cost benefit aspects. 'Occupational asthma is a disease characterized by variable airflow limitation and/or airway hyperresponsiveness due to causes in a working environment. These causes can give rise to asthma through immunological or non-immunological mechanisms. Up to 15% of all asthma cases are of occupational origin or have at least a significant causal occupational factor. According to the New Zealand part of the European Respiratory Health Survey, an increased risk of asthma prevalence was found for several occupations such as laboratory technicians, food producers, chemical workers, plastic and rubber workers. The Spain part of this study comprising 2646 Spanish subjects showed an asthma risk to be attributed to occupational exposures between 5 and 6.7%. Main asthma-inducing agents in the workplace are flour, grain and feed dust, animal dander/urinary proteins and isocyanates. Further, several inhalative irritants such as chlorine, acid or alkaline aerosols play a pivotal role. Many low molecular weight chemicals have irritative as well as allergenic effects on the airways, e. g. isocyanates and acid anhydrides. In addition to chronic or repetitive exposures, also singular accidental exposure to high concentrations of irritative or toxic airborne substances can cause occupational asthma. This condition is frequently called reactive airways dysfunction.

Allergens↗
PubMed1997

Flow-cytometric analysis of T-cell receptor expression in peripheral blood lymphocytes.

BACKGROUND: Lymphocytes of subjects sensitized to the insect-derived allergen Chi t 1-9 are, in response to the allergen, characterized by an elevated proliferation and increased expression of activation markers such as HLA-DR and CD25 in vitro. A restriction for HLA-DR B1 in monosensitized patients was found. OBJECTIVE: The aim of this study was to investigate whether the response to the allergen Chi t 1-9 involves the preferential cell surface expression of a specific alpha/beta T-cell receptor type. METHODS: The T-cell receptor repertoire was measured with 7 monoclonal antibodies to epitopes on the variable region of the alpha- and beta-chain by flow cytometry. Cell lines of 9 patients were established with Chi t 1-9, 6 with tetanus toxoid and 6 with phytohaemagglutinin in the presence of interleukin 2. In addition, non-stimulated lymphocytes as well as lymphocytes of 5 non-sensitized controls exposed to Chi t 1-9 were examined. RESULTS: Each of the 9 sensitized and 5 control subjects studied showed an individual pattern of lymphocyte expression for each T-cell receptor specificity. However, after stimulation specific to Chi t 1-9 for 2 weeks, a significant increase in V beta 8-expressing cells was measurable only in patients sensitized to Chi t 1-9. The cells of the 5 control subjects showed no significant changes due to the allergen stimulation. CONCLUSION: These data suggest that the expression of certain T-cell receptor types plays an important role in the development of Chi t 1-9 allergy.

Allergens↗
PubMed1996

Lymphocyte proliferation response to extracts from different latex materials and to the purified latex allergen Hev b 1 (rubber elongation factor).

BACKGROUND: Type I allergy to latex is a growing problem, especially among health care workers. A detailed study of the peripheral blood cell responses to latex allergens has not been reported. METHODS: Peripheral blood mononuclear cells of patients and healthy subjects were isolated and stimulated with protein extracts from latex sap and latex gloves and the purified latex allergen Hev b 1 (rubber elongation factor) at different concentrations to determine the antigen-specific proliferation response. The examined patients were sensitized to latex by occupational exposure (n = 23) and had rhinitis, conjunctivitis, contact urticaria, and/or asthma. Two control groups of nonsensitized subjects were studied: one occupationally exposed to latex (n = 8), and the second, not exposed to latex (n = 8). RESULTS: In general, only latex-exposed subjects responded to the different latex antigen preparations. Lymphocyte proliferation responses to latex sap extract were found in 65% of latex-sensitized subjects and in 37.5% of the latex-exposed healthy subjects. Latex glove extract induced a significant proliferative responses in 47.8% of latex-sensitized patients and in 25% of the latex-exposed individuals. Hev b 1 induced lymphocyte proliferation responses in 52% of the latex-sensitized patients and in 25% of the latex-exposed subjects indicating that Hev b 1 is relevant antigen in these latex-sensitized and latex-exposed groups. Peripheral blood mononuclear cells of 39.1% of the latex-sensitized subjects responded to all three allergen preparations (latex sap and latex glove extract, as well as Hev b 1). We could find no correlation between latex-specific IgE level and latex-induced lymphocyte proliferation response. CONCLUSION: Our data indicate that the 14 kd protein Hev b 1 is a relevant allergen in health care workers. It can be detected by specific IgE antibodies to Hev b 1, as well as in lymphocyte proliferation assay. In addition, our study suggests that antigen-specific proliferation response to latex is associated with exposure to latex, but not with the level of specific latex IgE. This may be useful for the evaluation and prediction of latex hypersensitivity development.

Adult↗
PubMed1994

Conformations of peptide fragments comprising the complete sequence of component III of Chi t I and their relationship to T-cell stimulation.

Conformational preferences of synthetic peptides that span the complete sequence of Chironomus thummi hemoglobin (Chi t I) component III were studied by nuclear magnetic resonance (NMR) and CD spectroscopies. The peptides, 19-21 amino acids in length, were studied in water, except for the C-terminal peptide, which was investigated in DMSO-d6. NMR showed that all investigated peptides lacked uniquely folded conformations in water at 4 degrees C and pH 3.0 or at 10 degrees C and pD 6.6 in DMSO. However, some preferential helix-like conformations for the peptides corresponding to the helices of the folded protein could be seen in solution. These peptides showed characteristic interactions for conformations in both the beta- and alpha-regions of phi-psi space, based on strong C alpha H(i)-NH(i + 1) interactions, and on NH-NH, C alpha H(i)-NH-(i + 2), C alpha H(i)-NH(i + 3), and C alpha H(i)-C beta H(i + 3) interactions, respectively. Helical motifs seem not to be the most important factors in determining MHC-binding and/or T-cell recognition. However, there is a tendency that more stabilized secondary structures show higher T-cell stimulation.

Allergens↗
PubMed1994

Analysis of B-cell epitopes in the N-terminal region of Chi t I component III using monoclonal antibodies.

The hemoglobins of the midge Chironomus thummi thummi (Chi t I) are known to cause immediate-type hypersensitivity reactions in humans. Further knowledge of the antigenic sites of such allergens will provide new therapeutic approaches. The aim of our study was to identify and characterize linear B-cell epitopes of the hemoglobin component III of Chi t I (136 amino acid residues). Using the antigenic index algorithm of Jameson and Wolf (Jameson and Wolf (1988) Comput. Appl. Biosci. 4, 181-186), three linear binding sequences of this allergen molecule were predicted. Two mouse monoclonal antibodies (mAbs 3 and 6) raised against purified Chi t I component III were investigated by ELISA for their binding to nine synthetic peptides 19-21 residues in length, covering nearly the whole sequence of component III. MAb 6 recognized only one peptide (11-30) while mAb 3 bound to both N-terminal peptides (1-19 and 11-30), suggesting that the antibody binding site is located in the overlapping region. This assumption could be confirmed in ELISA with solid phase-bound recombinant peptides (RP) as well as in inhibition studies with free tryptic peptides indicating that identification of these linear B-cell epitopes is neither influenced by the method of peptide production nor by the kind of used immunoassay. To define the essential amino acid residues we investigated mAbs with solid phase-bound overlapping octamers. In the case of mAb 3, amino acids experimentally identified as essential for antibody binding (aa 13-17) are identical with those residues predicted as a B-cell epitope with the antigenic index of Jameson and Wolf.

Allergens↗
PubMed1994

Chironomidae hemoglobin allergy in Japanese, Swedish, and German populations.

Hemoglobins of the Diptera (insect) family Chironomidae have been identified as causative allergens in asthmatic patients. In this study, 229 Japanese, 17 Taiwanese, and 92 Swedish sera from atopic patients were tested for antibodies against Chi t I, the hemoglobin from the European midge species Chironomus thummi, and against crude extracts from the Japanese midges Tokunagayusurika akamusi (T. akamusi) and Cricotopus sylvestris (Cr. sylvestris). Nearly 40% of patients showed a positive reaction to Cr. sylvestris extract, which contains no hemoglobin. This result is probably due to the presence of other partially cross-reacting allergens than hemoglobin. Nearly all tested Japanese serum samples showed cross-reactivity between Chi t I and Cr. sylvestris, a finding which is evidence for common epitopes in both midge species. Furthermore, an overall good correlation between the amounts of IgE antibodies against Chi t I and Chi t I component III was found in sera from Swedish, Japanese, and German patients.

Allergens↗
PubMed1994

Allergen-induced expression of cell surface markers on lymphocytes of Chi t I-sensitized patients.

Lymphocyte cultures of persons sensitized to the hemoglobin allergen Chi t I show a highly significant response to the allergen measured in the lymphocyte stimulation assay by (3H)-thymidine uptake. In this study, we investigated by flow cytometry the expression of different cell surface markers on lymphocytes after in vitro stimulation for 7 d with or without the allergen Chi t I. We determined the expression of the low-affinity receptor for IgE (CD23) on lymphocytes of Chi t I-sensitized patients and Chi t I-exposed as well as nonexposed controls. CD23 expression was significantly higher in patients than in nonexposed controls. Exposed but healthy subjects showed intermediate values. We also determined the expression of activation markers CD25 (IL-2 receptor) and HLA-DR on the lymphocytes of patients and nonexposed controls. HLA-DR expression on non-T cells (CD3-) was significantly higher in patients than in controls. HLA-DR on T cells (CD3+), and CD25 as well as CD23 expression, could be significantly enhanced after antigen-specific stimulation in patients but not in controls, whereas alpha/beta-T-cell-receptor expression was significantly reduced in patients. Differences between patients and controls were not observed in response to tetanus toxoid (TT) and phytohemagglutinin (PHA). Our results demonstrate antigen-specific influences on the expression of cell surface molecules. These findings may be valuable diagnostic information.

Allergens↗
PubMed1994

Increased gamma/delta-positive T-cells in blood and bronchoalveolar lavage of patients with sarcoidosis and hypersensitivity pneumonitis.

A small population of T-cells does not express the conventional T-cell receptor (TCR), characterized by the alpha and beta polypeptide chains (alpha/beta TCR) but two polypeptides termed gamma and delta (gamma/delta TCR). Changes in gamma/delta TCR expression may be relevant as the cause or consequence of several diseases. Our study was undertaken to determine and compare the distribution of T-cells expressing gamma/delta TCR in blood and bronchoalveolar lavage (BAL) of patients with sarcoidosis, hypersensitivity pneumonitis (HP), idiopathic pulmonary fibrosis (IPF), and of healthy controls. In addition, the association between gamma/delta TCR of blood T-lymphocytes and accessory molecules was analysed. Using direct immunofluorescence with the anti-gamma/delta TCR and anti-CD3 monoclonal antibodies (MoAbs) followed by flow cytometric analysis, the blood of patients with pulmonary sarcoidosis, HP, IPF and of healthy controls was analysed. To reveal the association between gamma/delta TCR of blood T-lymphocytes and the accessory molecules, expression of CD4, CD8 and CD25 were determined. Calculating the percentage and the total number of CD3+ gamma/delta TCR cells in blood, the data indicated a significant increase of gamma/delta T-cells in individuals with pulmonary sarcoidosis and HP, compared to healthy controls and IPF patients. In sarcoidosis patients with elevated CD3+ gamma/delta TCR levels, significantly lower CD4/CD8 ratios were observed. In addition, our data demonstrate a correlation between the decrease of CD4+ cells in blood and the amplified appearance of gamma/delta TCR expression in sarcoidosis patients, but not in HP patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Epitope mapping with peptides of Chi t I component III and immunomodulation of the Chi t immune response.

BACKGROUND: Hemoglobins of the Diptera family are known as aggressive inhalant allergens. METHODS: The whole sequence of the insect allergen Chi t I component III was studied for T-cell epitope activity in cell cultures of 15 sensitized patients with a panel of 17 overlapping synthetic peptides and 12 peptides obtained by tryptic cleavage. RESULTS: All but one of the peptides tested were found to be immunogenic. The nonstimulatory sequence 102-109 and two other tryptic peptides (69-90 and 110-135) were used in inhibition experiments. The Chi t I-induced proliferation was downregulated by all tested peptides when compared with stimulation with Chi t I alone. CONCLUSIONS: Because stimulation with phytohemagglutinin or tetanus toxoid was not influenced by the above-mentioned peptides, this mechanism seems to be specific for the antigen. Specific immunomodulation with nonstimulating peptides may offer new therapy approaches.

Adjuvants, Immunologic↗
PubMed1993

Humoral immune response to the insect allergen Chi t I in aquarists and fish-food factory workers.

Our examination of 225 subjects who had been exposed to the insect allergen Chi t I involved the degree of allergen exposure, the exposure-associated symptoms, and their relationship to the presence of specific IgE and IgG antibodies as well as sensitization to ubiquitous allergens. It could be shown that specific IgE antibodies found in 34% of these subjects were closely associated with symptoms (P < 0.01), whereas no relationship between IgG antibodies and complaints could be observed. Conjunctivitis (63%) and rhinitis (62%) were predominant, followed by asthma (45%) and urticaria (37%). Antibody levels of patients suffering from asthma were highest. In addition, symptoms were associated with the degree of exposure. While nearly all IgE-sensitized subjects of the medium-, high-, and very high-exposure group were symptomatic, only 57% of the sensitized individuals of the low-exposure group reported complaints. Furthermore, specific IgE antibodies were most frequently present in the groups with medium (46%) and high (54.5%) exposure, whereas IgG antibodies predominated in individuals with very high exposure (69.1%). In the low-exposure group, most subjects (73.6%) had neither IgE nor IgG antibodies. In addition, within Chi t I sensitized subjects, sensitization to common allergens and elevated total IgE levels were more frequently present than within non-Chi t I sensitized individuals, indicating a predisposition to allergy.

Allergens↗