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Biomedical subjects

B O Boehm

Publications and source records attributed to B O Boehm.

At least 73 records · Page 4Linked to original sources
PubMed1994

Sequence homology of the diabetes-associated autoantigen glutamate decarboxylase with coxsackie B4-2C protein and heat shock protein 60 mediates no molecular mimicry of autoantibodies.

Molecular mimicry between viral antigens and host proteins was often suggested to be involved in induction of autoimmune diseases. In type 1 diabetes where pancreatic beta cells are destroyed by autoimmune phenomena, a linear sequence homology between a major autoantigen, glutamate decarboxylase (GAD), and the 2C protein of coxsackie B4 was identified. In addition, a sequence homology between GAD and the mycobacterial heat shock protein 60 was described and the suggestions were made that molecular mimicry between GAD, coxsackievirus B4-2C protein, and/or heat shock protein 60 (hsp60) may be actively involved in an autoimmune reaction towards the pancreatic beta-cells. Our group was the first to isolate human monoclonal autoantibodies to GAD (MICA 1-6) from a patient with newly diagnosed type 1 diabetes. The MICA allowed a detailed characterization of the diabetes associated self-epitopes in GAD and represent a set of GAD autoantibodies present in sera from patients with type 1 diabetes. Using deletion mutants of GAD we demonstrated that the regions of GAD covering the homology sequences to coxsackievirus B4 and to the hsp60 were absolutely required for binding of the MICA to GAD. We now designed an antibody-based analysis to ask whether molecular mimicry between GAD and coxsackie B4-2C or hsp60 is relevant in type 1 diabetes. Since part of the MICA recognize conformational epitopes, they allow to test for conformational molecular mimicry in viruses that have been incriminated in the development of type 1 diabetes. Our data reveal no crossreactivity between the diabetes associated GAD epitopes defined by the MICA and hsp60, rubellavirus, cytomegalovirus, and coxsackie B1-B6 virus antigens. Neither coxsackie B4-specific antibodies in sera from normal individuals nor GAD-positive sera from patients with type 1 diabetes indicated a crossreactivity between coxsackie B4-2C and GAD. Although the regions in GAD homologous to coxsackie B4-2C and hsp60 represented parts of GAD indispensible for binding of diabetes associated autoantibodies they did not mediate a crossreactivity of autoantibodies between GAD and these two proteins. No evidence for molecular mimicry between GAD and a whole panel of foreign antigens was detected by autoantibodies in type 1 diabetes.

Amino Acid Sequence↗
PubMed1994

Typing of the HLA-DRB3 gene by temperature gradient gel electrophoresis. Prediction of the resolution of four allelic fragments by computational simulation of DNA melting.

Four alleles are currently recognised at the HLA-DRB3 locus (DRB3*0101, DRB3*0201, DRB3*0202 and DRB3*0301). We studied whether 271 bp fragments of the polymorphic second exon, which were prepared using the polymerase chain reaction, could be typed using temperature gradient gel electrophoresis. Thermal stability curves for the allelic DNA molecules were calculated by computer simulation and the results were validated experimentally. The DRB3*0201 and DRB3*0202 derived homoduplexes were predicted to have identical thermal stability. Thus, only three denaturation and relative mobility curves were obtained for the four homoduplex fragments DRB3*0101, DRB3*0201, DRB3*0202 and DRB3*0301. Computational analysis predicted that DRB3*0201 and DRB3*0202 could be distinguished by electrophoresis of artificially generated heteroduplexes. When verified experimentally, the results of the theoretical analyses were confirmed. We conclude, that computational simulation of the melting behaviour of DNA molecules permits the resolution of allelic sequences to be predicted by temperature gradient gel electrophoresis. We also demonstrate that temperature gradient gel electrophoresis is a powerful tool for the assessment of HLA genotypes. It may have wide application in transplantation immunology and in the study of disease associations of allelic variation at the HLA loci.

Alleles↗
PubMed1994

Long-term compliance of intensified insulin therapy.

Results of the DCCT trial (N. Engl. J. Med. 329, 977-986) demonstrate that therapy in insulin-dependent diabetes mellitus (IDDM) should aim at near-normoglycemia. For reaching this standard, intensified insulin therapy--either intensified conventional therapy (ICT) or continuous subcutaneous insulin infusion (CSII)--is mandatory. These regimes demand much long-term motivation and discipline from the diabetics. With > 95%, long-term compliance of ICT is good, according to the few published data available and our own experience. For CSII, on the other hand, cumulated studies reveal discontinuation rates ranging from 0% to 36%, averaging 20.4% and being significantly correlated with metabolic control before start of CSII in terms of glycosylated hemoglobin levels (r = 0.66; P < 0.05). The major reasons for discontinuation of CSII were skin problems (22.1%), inconvenience of the pump (21.4%) and lack of metabolic improvement (9.6%). A conclusion drawn from these meta-analytical data is that a stepwise approach to CSII is recommended for increasing compliance. A period of ICT long enough to gain experience with blood glucose self-control and self-adjustment of meal-related insulin should precede CSII. Furthermore, a general increase of CSII among IDDM patients is necessary to come closer to the standard of near-normoglycemia for these diabetics. Therefore, diabetes treatment and education resources must be improved, especially concerning psychosocial problem solving and cooperation between diabetologists and general practitioners.

Biomarkers↗
PubMed1994

Association between antibodies to the MR 67,000 isoform of glutamate decarboxylase (GAD) and type 1 (insulin-dependent) diabetes mellitus with coexisting autoimmune polyendocrine syndrome type II.

By using an immunoprecipitation assay, we analysed reactivity of autoantibodies to human recombinant GAD65 and GAD67 in sera from patients with autoimmune polyendocrine syndrome Type II (APS II) with and without Type 1 (insulin-dependent) diabetes mellitus (IDDM) compared to patients with organ-specific autoimmunity. Overall antibodies to GAD65 were correlated with IDDM in all study groups, whereas GAD67 antibodies were associated with IDDM when APS II coexists. Antibodies to GAD65 and GAD67 were detected in 13 (44.8%) and 7 (24.1%) out of 29 APS II patients with IDDM, but in only 4 (13.8%) and 2 (6.9%) out of 29 APS II patients without IDDM, respectively (p < 0.05). In short-standing IDDM (< 1 year), antibodies to GAD67 were significantly more frequent in patients with APS II (5 of 9 [55.6%] subjects) compared to matched diabetic patients without coexisting polyendocrinopathy (1 of 18 [5.6%] subjects) (p < 0.02). The levels of GAD65 (142 +/- 90 AU) and GAD67 antibodies (178 +/- 95 AU) were significantly higher in patients with polyglandular disease than in patients with isolated IDDM (91 +/- 85 AU and 93 +/- 57 AU) (p < 0.02). Interestingly, all 11 GAD67 antibody positive subjects also had GAD65 antibodies (p < 0.0001), and in 10 of 11 anti-GAD67 positive sera the GAD67 antibodies could be blocked by either GAD67 or GAD65, suggesting the presence of cross-reactive autoantibodies. No correlation was observed between GAD antibodies and age, sex or any particular associated autoimmune disease, besides IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

HLA-DR3 and HLA-DR5 confer risk for autoantibody positivity against the thyroperoxidase (mic-TPO) antigen in healthy blood donors.

The prevalence of circulating autoantibodies against thyroperoxidase (mic-TPO) was determined in 3,000 healthy blood donors (age range: 23 to 60 years) from the Hamburg area. Of the blood donors, 153 (5.1%) were found to have high titer of mic-TPO (> 350 IU/ml). Only two autoantibody positive subjects (0.06%) were chemically hyper- and hypothyroid, respectively. Analysis of HLA-DR specificities revealed that HLA-DR specificities DR3 and DR5 were significantly increased when compared to controls (n = 1,863). Comparison of the autoantibody-positive probands with a group of disease controls, i.e., Graves' patients and patients with lymphocytic thyroiditis, revealed a higher prevalence of HLA-DR3-positive HLA haplotypes in the disease controls when compared to autoantibody positives. Individuals with a mic-TPO level greater than 2,000 IU/ml were almost exclusively found to have one HLA-DR3 or HLA-DR5 positive HLA haplotype. We conclude that a high prevalence of high-titer mic-TPO can be found in healthy blood donors. Circulating signs of thyroid autoimmunity were associated with HLA specificities also found to be associated with autoimmune thyroid diseases.

Adult↗
PubMed1993

Bone metabolism before and after irradiation with ultraviolet light.

The beneficial effects of ultraviolet light on cutaneous vitamin D synthesis, calcium metabolism, and bone formation are well known. Regarding the increasing fear of side effects from ultraviolet B (UV-B), lamps with less energy in the UV-B range have been developed. Two spectra with differences in the emission of UV-B have therefore been evaluated for their influence on calcium metabolism. A group of 24 healthy male volunteers was subdivided into two treatment groups. Group 1 was exposed to lamps with higher energy of total UV-B but less energy at the wavelengths below 300 nm than the lamps used in group 2. All subjects were irradiated ten times within 12 days. Exposure time was 3 min in the first session and time of exposure was increased by 10% in every following irradiation (suberythematous doses only). Before the first irradiation, 3 days after the last exposure, and after 4 more weeks, the serum parameters of bone metabolism were determined by standard laboratory methods. Significantly increased levels of 25-hydroxyvitamin D3 were found in both groups. There was only a slight increase of 1,25-dihydroxyvitamin D3. Parathyroid hormone decreased significantly in group 2 only. The data would suggest beneficial effects on bone metabolism for both regimens. The observed effects were more pronounced when shorter wavelengths (group 2) were applied, although the total energy of UV-B was lower in these lamps.

Adult↗
PubMed1993

The effect of a biphasic desogestrel-containing oral contraceptive on carbohydrate metabolism and various hormonal parameters.

During 6 cycles of treatment of 19 women, the effect of a low-dose biphasic oral contraceptive containing 40 micrograms ethinylestradiol + 25 micrograms desogestrel (7 tablets) and 30 micrograms ethinylestradiol + 125 micrograms desogestrel (15 tablets) on various hormonal parameters and glucose metabolism was compared with the values of the pre- and post-treatment cycle. There was a profound reduction in gonadotropin secretion and ovarian steroid synthesis. The serum levels of testosterone were reduced by 35%, free testosterone by 55%, and DHEA-S by 30%. Cortisol increased by 100%, SHBG by 250%, and TBG by 60%, while FT3 and FT4 were only marginally influenced. Fasting levels of glucose and insulin did not change significantly, but the glucose load revealed a slight impairment of glucose tolerance. Three weeks after termination of pill intake, the various parameters returned to pretreatment levels, except for SHBG and TBG which were still elevated by 20 to 30%. The results demonstrate a marked preponderance of the effect of the estrogen component, a reliable inhibition of ovulation and very good cycle control during treatment with the biphasic formulation.

Adult↗
PubMed1993

Rapid and simple subtyping of the HLA-DRB3 gene in Graves' disease by using temperature-gradient gel electrophoresis.

A HLA-DRB3-subtyping system that uses TGGE for analyzing DRB3 alleles was developed. The polymorphic second exon of the HLA-DRB3 gene was amplified from four homozygous typing cell lines, 223 healthy individuals, and 102 patients with Graves' disease by using the PCR. The PCR products were electrophoresed in a temperature gradient from 35 degrees C to 70 degrees C, and the resulting fragments were visualized by silver staining. Four DRB3 alleles (HLA-DRB3*0101, *0201, *0202, and *0301) were distinguished from one another by the migration of the corresponding homoduplex with the exception that DRB3*0201 was indistinguishable from DRB3*0202. The latter two alleles, however, were resolved by the artificial heteroduplexing approach. Arginine in position 74 of the DRB3 gene product (i.e., HLA-DRB3*0101) was significantly more frequent in Graves' patients than in controls. The relative risk conferred by the presence of the DRB3*0101 was 15.8 (p < or = 0.001). The presence of arginine in position 74 contributed to an etiologic fraction of 75% in our study population. The PCR-TGGE technique is a simple, nonisotopic method, which may be useful in rapid screening of large populations for HLA disease markers.

Alleles↗
PubMed1992

HLA-DRB3 gene alleles in Caucasian patients with Graves' disease.

Graves' disease (GD) is a human leukocyte antigen (HLA) linked organ-specific autoimmune disease. In German GD patients the disease is associated with HLA specificities of the HLA-DRw52 family (HLA-DR3, -DR5, and DR6; HLA-DRB3 positive HLA haplotypes). Recently, a strong association with a HLA-DRB3 restriction fragment length polymorphism gene has been described. To study HLA-DRB3 alleles and their association with the disease, a large cohort of controls (n = 3724) and GD patients (n = 304) was analyzed. HLA-DR allelic combinations revealed an increase in HLA-DR3/DR5 heterozygous patients (relative risk 2.9; P < 0.001). HLA-DRB3 alleles, as defined by DNA typing in HLA-DR matched groups revealed a significant increase in DRB3*0101 homozygosity (relative risk 17.5; P < 0.001) in HLA-DR3 homozygous patients. In GD patients with ophthalmopathy (grade II or higher, according to Werner) DRB3*0101/*0202 heterozygosity revealed an increased relative risk of 5.5 (P < 0.001). Non-HLA-DR3 homozygous, DRB3*0101/*0202 heterozygous patients were at the highest risk for endocrine ophthalmopathy (relative risk 10; P < 0.001). Our data, based on DNA typing methods of HLA-D genes, provide evidence that the susceptibility is strongly associated with HLA-DRB3 genes.

Alleles↗
PubMed1992

Antibodies to the M(r) 64,000 (64K) protein in islet cell antibody positive non-diabetic individuals indicate high risk for impaired beta-cell function.

A prospective study of a normal childhood population identified 44 islet cell antibody positive individuals. These subjects were typed for HLA DR and DQ alleles and investigated for the presence of antibodies to the M(r) 64,000 (64K) islet cell antigen, complement-fixing islet cell antibodies and radiobinding insulin autoantibodies to determine their potency in detecting subjects with impaired Beta-cell function. At initial testing 64K antibodies were found in six of 44 islet cell antibody positive subjects (13.6%). The same sera were also positive for complement-fixing islet cell antibodies and five of them had insulin autoantibodies. During the follow-up at 18 months, islet cell antibodies remained detectable in 50% of the subjects studied. In all six cases who were originally positive, 64K antibodies were persistently detectable, whereas complement-fixing islet cell antibodies became negative in two of six and insulin autoantibodies in one of five individuals. HLA DR4 (p less than 0.005) and absence of asparic acid (Asp) at position 57 of the HLA DQ beta chain (p less than 0.05) were significantly increased in subjects with 64K antibodies compared with control subjects. Of 40 individuals tested in the intravenous glucose tolerance test, three had a first phase insulin response below the first percentile of normal control subjects. Two children developed Type 1 (insulin-dependent) diabetes mellitus after 18 and 26 months, respectively. Each of these subjects was non-Asp homozygous and had persistent islet cell and 64K antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[Gene amplification with PCR and sequence specific HLA oligonucleotide typing].

Genetic polymorphism in the HLA class II region has been identified by the analysis of the polymerase chain reaction (PCR) products using sequence-specific oligonucleotide (SSO). The PCR-SSO method permits precise and direct analysis of allelic variations with as little as 1 microgram of genomic DNA. The standardized, uniform hybridization and critical wash protocol of the Eurotransplant typing kit enables HLA typing independent of gene expression and quality of lymphocytes. One of the advantages of this technique is that the definition of splits is much better than typing by serology.

Base Sequence↗
PubMed1992

[Gene amplification with PCR and sequence-specific HLA oligotyping].

Genetic polymorphism in the HLA-class II region has been identified by the analysis of the polymerase-chain reaction (PCR) products using sequence-specific oligonucleotide (SSO). The PCR-SSO method permits precise and direct analysis of allelic variations with as little as 1 microgram of genomic DNA. The standardized, uniform hybridization and critical wash protocol of the Eurotransplant-typing kit [2] enables HLA-typing independent of gene expression and lymphocytes quality. One of the advantages of this technique is that the definition of subtypes is much better than is typing by serology.

Amino Acid Sequence↗
PubMed1991

Insulin autoantibodies as determined by competitive radiobinding assay are positively correlated with impaired beta-cell function--the Ulm-Frankfurt Population Study.

Out of a random population of 4208 non-diabetic pupils without a family history of Type I diabetes 44 (1.05%) individuals had islet cell antibody (ICA) levels greater or equal to 5 Juvenile Diabetes Foundation (JDF) units. 39 of these ICA-positives could be repeatedly tested for circulating insulin autoantibodies (CIAA) using a competitive radiobinding assay. The results were compared with the insulin responses in the intravenous glucose tolerance tests (IVGTT) and with HLA types. Six pupils were positive for CIAA. All of them had complement-fixing ICA, and 5 of them were HLA-DR4 positive. Three of the 6 showed a first-phase insulin response below the first percentile of normal controls. Our data indicate that in population-based studies CIAA can be considered as a high risk marker for impaired beta-cell function in non-diabetic ICA-positive individuals.

Adolescent↗
PubMed1991

Prevalence of HLA-DQ beta chain non-Asp alleles in type I (insulin-dependent) diabetics with young and older ages of onset.

Particular HLA-DQ beta chain alleles were reported as immunogenetic markers of type I diabetes mellitus with young onset of the disease. In a homogeneous German population, we studied HLA-DR specificities and HLA-DQ beta chain alleles in young-onset (less than 21 years of age; n = 185) and adult-onset (greater than 40 years of age; n = 48) insulin-dependent diabetics. In both cohorts of type I diabetics, the HLA-DR3 and -DR4 specificities were significantly increased. The presence of an HLA haplotype with an amino acid other than aspartic acid at position 57 of the DQ beta chain was significantly associated with type I diabetes in both cohorts (etiologic fraction: 93% and 73%). We conclude that the presence of DNA sequences coding for an amino acid other than aspartic acid at the 57th position of the DQ beta chain provides a molecular risk marker for type I diabetes of both and adult onset.

Adolescent↗
PubMed1991

Aspartic acid at position 57 of the HLA-DQ beta chain is protective against future development of insulin-dependent (type 1) diabetes mellitus.

Insulin-dependent (Type I) diabetes mellitus is a chronic autoimmune disease. From studies in discordant twins and multiplex families a long prediabetic period has been reported. In a population-based program started in 1983, fifteen individuals at possible risk for future Type I diabetes were followed for up to 74 months. Two individuals (13%) developed Type I diabetes. These probands were characterized by the presence of high-level cytoplasmic islet cell antibodies (ICA), complement-fixing ICA, and an impaired first-phase insulin response after intravenous glucose load. Both were homozygous for a high-risk immunogenetic marker of Type I diabetes, i.e., non-Asp at codon 57 of the HLA-DQ beta chain. In all other subjects studied, the immunogenetic marker that confers "dominant resistance", aspartic acid at codon 57, was found. On the basis of our data we conclude that a combination of assays which determine ICA, first-phase insulin release, and HLA-DQB1 polymorphisms will identify individuals with a high probability of developing Type I diabetes at the population level. Conversely, HLA haplotypes positive for aspartic acid seem to confer resistance to the disease.

Adult↗
PubMed1991

No association between islet cell antibodies and Coxsackie B, mumps, rubella and cytomegalovirus antibodies in non-diabetic individuals aged 7-19 years.

Viral antibodies were tested in a cohort of 44 islet-cell antibody-positive individuals age 7-19 years, and 44 of their islet cell antibody-negative age and sex-matched classmates selected from a population study of 4208 pupils who had been screened for islet cell antibodies. Anti-coxsackie B1-5 IgM responses were detected in 14 of 44 (32%) of the islet cell antibody-positive subjects and in 7 of 44 (16%) control subjects. This difference did not reach the level of statistical significance. None of the islet cell antibody-positive subjects had specific IgM antibodies to mumps, rubella, or cytomegalovirus. There was also no increase in the prevalence or the mean titres of anti-mumps-IgG or IgA and anti-cytomegalovirus-IgG in islet cell antibody-positive subjects compared to control subjects. These results do not suggest any association between islet cell antibodies, and possibly insulitis, with recent mumps, rubella or cytomegalovirus infection. Further studies are required to clarify the relationship between islet cell antibodies and coxsackie B virus infections.

Adolescent↗
PubMed1991

The HLA-DQ beta non-Asp-57 allele: a predictor of future insulin-dependent diabetes mellitus in patients with autoimmune Addison's disease.

HLA-DR specificities in 72 Addison's (AD) patients and 808 local controls were compared. We confirmed earlier reports that the HLA-DR3 specificity is significantly increased in AD patients. In our study a relative risk of 3.4 chi 2 = 22.5; pc = 0.01) for the disease was calculated. Analysis of HLA-DQB1 alleles in DR4+ Addison's patients with diabetes mellitus (N = 6) and without IDDM (14 of 18 individuals tested) revealed that the HLA-DQw8 allele (DQB1*0302) was significantly increased in AD patients with IDDM (chi 2 = 13.5; p = 0.001); conversely, a clustering of the HLA-DQw7 allele was detected in DR4+ Addison's patients without IDDM. We thus conclude that particular polymorphic alleles corresponding to non-charged amino acids at position 57 of the HLA-DQ beta-chain [non-Asp-57 alleles] are associated with IDDM also in Addison's patients.

Addison Disease↗