Factors associated with the presence of glutamic acid decarboxylase and islet antigen-2 autoantibodies in patients with long-standing type 1 diabetes

AIM

Glutamic acid decarboxylase (GAD) and/or islet antigen-2 (IA-2) autoantibodies (ab) are present in 90% of patients at the onset of type 1 diabetes (T1D). Few studies have shown that they may persist in the long-term. We analysed the frequency of GADab and IA-2ab and the factors associated with their persistency in patients with long-lasting T1D.

METHODS

This cross-sectional study included 430 adult patients with T1D of at least 10-year duration, consecutively seen over one year. GADab and IA-2ab were determined by radio-binding assays. Autoantibodies to thyroperoxydase, gastric parietal cells and transglutaminase were assessed in 418 patients, and HLA DRB1 genotyping in 359. Parameters associated with the persistency of antibodies were studied by multivariate analysis.

RESULTS

Median age at diagnosis of T1D was 12 years, and median diabetes duration was 19 years. Extrapancreatic autoimmunity was present in 38% of the patients, and associated autoimmune diseases in 21%. GADab and/or IA-2ab were found in 56% of the patients, and in 32% in those with more than 25-year diabetes duration. GADab were more frequent than IA-2ab. Female sex, an older age at diagnosis, and a shorter duration of diabetes were independently associated with the presence of ab. The same factors and the DR3 allele were associated with GADab, while only diabetes duration and the DR4 allele were associated with IA-2ab.

CONCLUSION

In a large proportion of the patients with T1D, the long-term persistency of diabetes-associated antibodies allows aetiological diagnosis, even far from the onset of hyperglycaemia.

Adult celiac disease with severe or partial villous atrophy: a comparative study

BACKGROUND AND AIMS

While severe villous atrophy (SVA) is the most typical histological feature in adult celiac disease (ACD), partial villous atrophy (PVA) is now also frequently found. So far, the impact of the severity of villous atrophy on the clinical presentation of ACD has been scarcely investigated. We aimed to compare the clinical, biological and immune features and outcomes in ACD patients presenting with PVA at diagnosis versus patients with SVA.

PATIENTS AND METHODS

Medical files of 48 patients with ACD diagnosed between 1992 and 2003 were retrospectively studied. The diagnosis was based on the presence of intestinal villous atrophy, with increases in intraepithelial lymphocytes and circulating celiac specific antibodies. Villous atrophy was classified as severe (subtotal and total) or partial. Symptoms, biological signs of malabsorption, immune markers, bone mineral density at diagnosis and response to gluten-free diet were recorded.

RESULTS

At diagnosis, ten patients (four M/six F) had PVA and 38 patients (five M/33 F) had SVA, with a median age of 54 and 33 years, respectively (p<0.05). Positivity for specific antibodies, HLA typing and frequency of autoimmune disease at diagnosis were similar in both PVA and SVA patients, as was their response to gluten-free diet. Diarrhea, malabsorption syndrome and osteopenia were independent of the degree of villous atrophy.

CONCLUSION

PVA was observed in 21% of patients with ACD. Except for their older age at diagnosis, patients with PVA presented with similar clinical, biological and immune characteristics and outcomes as did patients with SVA.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

Physiopathologie de la maladie de Behçet

SUBJECT

Pathophysiology of Behçet's disease (BD) is complex. Recent experimental data shed new light on the mechanisms leading to organ lesions.

MAIN ISSUES

Neutrophils and cytotoxic lymphocytes are now recognized as key effector cells in BD. Genetic susceptibility, environmental factors (virus and/or bacterial infections), inflammatory response abnormalities (heat shock proteins, dysregulated NO production) and abnormal immune response play also a major role in BD pathogeny.

PERSPECTIVES

Better understanding of the BD pathophysiology will allow the development of new therapies more specific of BD.

Transient familial haemophagocytic lymphohistiocytosis reactivation post-CD34 haematopoietic stem cell transplantation

Familial haemophagocytic lymphohistiocytosis (FHLH) is a genetic disorder caused by defective lymphocyte cytotoxicity, resulting in impaired lymphocyte homeostasis and macrophage infiltration of solid tissues and bone marrow, with extensive haemophagocytosis. It is invariably fatal unless treated by allogeneic haematopoietic stem cell transplantation (HSCT). In a retrospective analysis of 11 cases of FHLH, transplanted in one centre between January 1999 and December 2003, it was found that host T cell expansion occurred early after HSCT in a setting of a viral infection (cytomegalovirus and Epstein-Barr virus respectively) in two cases who received T cell-depleted HSCT. Transient recurrence of clinical and biological manifestations of FHLH was observed, despite evidence for donor cell engraftment. Secondary development of donor T cells led to stable mixed chimaerism and sustained remission of FHLH. Detection of host-derived T cells soon after HSCT in a patient with FHLH should thus not mistakenly be taken as a manifestation of graft rejection.

Does haploidentical transplantation in children with primary immunodeficiencies have the potential to exploit donor NK cell alloreactivity?

Donor potential to exert NK cell alloreactivity has been shown to confer survival advantage in haploidentical hematopoietic cell transplantation for hematological malignancies. We investigated killer immunoglobulin receptor (KIR) ligand incompatibility in 40 children receiving haploidentical transplantation for primary immunodeficiencies. The conditioning regimen consisted of busulfan and cyclophosphamide. T-cell depletion of the graft used complement-dependent lysis or CD34+ selection. Two patients died in the first month. The remaining 38 patients were divided into those with (n=13) and those without (n=25) donor potential to exert NK cell alloreactivity. Engraftment was similar in the two groups (61.5 and 64%, respectively). The incidence of grade II-IV acute graft-versus-host disease (GVHD) tended to be lower in the group with donor potential to exert NK cell alloreactivity, but the difference was not significant. In conclusion, in this series of patients with primary immunodeficiencies, donor potential to exert NK cell alloreactivity was not associated with significant advantages in engraftment and prevention of acute GVHD.

Impact of HLA matching on outcome of hematopoietic stem cell transplantation in children with inherited diseases: a single-center comparative analysis of genoidentical, haploidentical or unrelated donors

SUMMARY

Hematological inherited diseases can be cured by hematopoietic stem cell transplantation (HSCT) from an human leukocyte antigen (HLA)-identical sibling donor (MSD), but the outcome of unrelated donors (URD) or haploidentical donors (HMD) has been a cause of concern. In all, 94 children affected with inherited diseases underwent HSCT at a single center using MSD (group A, n=31), URD (group B, n=23) or HMD (group C, n=40). There was no difference in the rate of engraftment or in the incidence of grades III-IV acute graft-versus-host disease (GVHD) between the groups. Survival rate was 80.6% in group A, 62.5% in group B and 47.5% in group C (P=0.023). In group B, survival rate was 73.7% in the subgroup with zero or one class I mismatch, and 25% in the subgroup with two or more class I mismatches (P=0.04). In group C, survival rate was 83.3% in the 9/10-identical subgroup, 64.3% in the seven or 8/10 subgroup, and 25% in the five or 6/10 subgroup (P=0.0007). Thus, engraftment, incidence of GVHD and survival are similar in recipients of grafts from MSD, URD with 0-1 class I-mismatch, or HMD with at least 7/10 HLA matches. The low success of HSCT using more disparate donors suggests reserving them for patients with very poor prognosis.

HLA-B phenotype modifies the course of Behçet's disease in Moroccan patients

In Moroccan patients, predisposition to Behçet's disease is associated with HLA-B*51, mostly in males with young age at disease onset. In addition, the disease is associated with B*15 both in females and in males with late disease onset. We analyzed the clinical presentation, the severity and the course of the disease in 86 Moroccan patients according to their HLA-B phenotype. The presence of the B*51 or B*15 did not predispose to a particular clinical manifestation, nor to a more severe presentation of the disease. By contrast, outcome of the disease significantly differed depending on HLA-B phenotype, with an increase of symptoms in most B*51+ patients and in half of B*15 patients, and a remission or a decrease of symptoms in all B*51-B*15- patients. This variable course was mostly observed for ocular lesions, skin lesions, articular symptoms, and neurological symptoms. These data may suggest that treatment should be given early in the course of the disease in B*51 or B*15-positive patients in order to stabilize the inflammatory process.

Histological features and HLA class II alleles in hepatitis C virus chronically infected patients with persistently normal alanine aminotransferase levels

OBJECTIVE

A significant proportion of individuals with chronic hepatitis C virus (HCV) infection have persistently normal alanine aminotransferase (ALT) levels. Although data are controversial, such patients usually have weaker histological damage and a lower progression rate of fibrosis. The aims of this study were: (1) to compare demographic, virological, and histological parameters of HCV patients with normal ALT values with those of HCV patients with elevated ALT levels; and (2) to determine whether HLA class II alleles contribute to the persistence of normal ALT levels in HCV patients.

PATIENTS AND METHODS

Eighty three patients with chronic HCV infection and persistently normal ALT values (group 1) and 233 patients with chronic HCV infection and elevated ALT levels (group 2) were studied. Histological features were expressed using Knodell and Metavir scores. HLA DRB1* and DQB1* genotyping was performed using hybridisation with sequence specific oligonucleotides after genomic amplification. The kappa2 and Fisher's exact tests were used to compare discrete variables and phenotype frequencies between the two groups, and Wilcoxon's test was used for continuous variables. A multivariate logistic regression model was used to determine which variables predicted normal ALT values.

RESULTS

ALT levels were correlated with the severity of liver damage. In group 1, 93% of patients had an F0 or F1 Metavir index of fibrosis compared with 47% of patients in group 2 (p<0.001). A longer duration of infection (p<0.001) and increased DRB1*11 phenotype frequency (pc=0.03) were observed among patients with normal ALT. The two groups did not differ with regard to the mode of contamination or viral genotype. After logistic regression, young age (p=0.0008), female sex (p=0.01), long duration of infection (p=0.0001), and HLA DRB1*11 (p=0.050) were more strongly associated with persistence of normal ALT.

CONCLUSIONS

Our study confirms that patients with chronic hepatitis C and normal ALT levels have less severe liver disease than those with elevated ALT levels. This particular biochemical outcome may be explained, at least in part, by host immunogenetic factors such as the presence of HLA-DRB1*11.

HLA class I polymorphism in a Moroccan population from Casablanca

We have studied the distribution of HLA-A and -B alleles and haplotypes by sequence-specific primer amplification in a sample of 100 unrelated healthy individuals belonging to both Berber and Arabic-speaking groups from the region of Casablanca in Morocco. Among the 17 HLA-A and 23 HLA-B alleles observed, the most frequent were HLA-A2 (21%), -A1 (11%), -A3 (10%), -B44 (11.4%), -B50 (9.9%), -B5(8.5%) and -B35 (6.5%). Six two-locus haplotypes were observed with a frequency above 5%: A2-B50 (9.6%), A23-B44 (7.4%), A2-B15 (6.4%), A68-B39 (5.3%), A1-B51 (5.3%) and A68-B44 (4.3%). Our data confirm that, on the basis of genetic distances, the majority of present-day North Africans from Morocco are closely related to Berbers and also to Iberians. They cluster apart from Middle-Eastern Mediterranean populations, and show greater genetic distances to Eastern and other Mediterranean populations. This study will serve as a reference for further anthropological studies, as well as studies of HLA and disease associations.

Anticardiolipin antibodies in patients with multiple sclerosis do not represent a subgroup of patients according to clinical, familial, and biological characteristics

BACKGROUND

In multiple sclerosis (MS), case control studies have shown that anticardiolipin antibodies (aCL Ab) are more frequent than in the general population and that aCL Ab positivity may be associated with specific clinical characteristics.

OBJECTIVES

To determine whether patients with MS who are positive for aCL Ab have specific characteristics.

METHODS

285 consecutive patients with MS were tested for aCL Ab positivity. Patients also underwent complete autoimmune screening and were systematically evaluated for clinical characteristics and individual or family history of autoimmune disease.

RESULTS

aCL Ab positivity was found in 42 patients (15%). The main isotype was aCL IgM (32 patients, 11%). Demographics and clinical characteristics including sex, age at onset, course of the disease, expanded disability status scale score, and progression index were not different between aCL Ab positive and aCL Ab negative patients. Clinical systems involved at onset or during the course of the disease were not different from what is usually observed in MS. aCL Ab positivity was not associated with an increased frequency of autoimmune disease and was not predictive of a family history of autoimmune disease. Patients positive for aCL IgM were more frequently positive for the presence of non-organ specific antibodies (53% v 39%, respectively, p = 0.02).

CONCLUSIONS

These results do not support the hypothesis that patients with MS with aCL Ab constitute a subgroup of MS according to demographic clinical and familial characteristics. The greater frequency of other antibodies in aCL Ab positive patients suggests that they only reflect a more general autoimmune activation in MS.

CTLA-4/CD 28 region polymorphisms in children from families with autoimmune hepatitis

Susceptibility to autoimmune hepatitis is associated with particular human leucocyte antigen class II alleles. However, non-HLA genetic factors are likely to be required for development of the disease. Among the candidate genes, the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and CD28 genes, located on chromosome 2q33 in humans, encode a cell surface molecule playing a dominant role in the regulation of T-cell activation. The CTLA-4 and CD28 polymorphisms were investigated in children from 32 families with autoimmune hepatitis (AIH). The transmission/disequilibrium test revealed increased transmission of the (AT)8 (dinucleotide repeat) and A (exon 1) alleles of CTLA-4 gene from heterozygous parents to affected offspring (87.5% and 83.5%) with type 1 AIH, compared with unaffected offspring (50.0% for both, p = 0.009 and 0.02, respectively). In contrast, no deviation in transmission for CTLA-4 polymorphisms was found between type 2 AIH patients and unaffected offspring. No evidence for association was found between CD28 gene polymorphism or D2S72 genetic marker and both types of AIH. This study identified the CTLA-4 gene polymorphism as a non-HLA determinant that predisposes to AIH type 1 in children. The genetic heterogeneity seen in the present study provides a new argument in favor of pathogenic differences between type 1 and type 2 AIH.

Family-based association of HLA class II alleles and haplotypes with type I diabetes in Brazilians reveals some characteristics of a highly diversified population

The association of HLA class II haplotypes with type I diabetes was analyzed in 56 Southeastern Brazilian families using affected family-based controls (AFBAC) method. DRB1-DQA1-DQB1 alleles were determined by polymerase chain reaction/sequence-specific primer genotyping. This study first revealed the great haplotype diversity of Brazilians (65 different haplotypes even with incomplete DRB1 subtyping), probably due to the admixture of Africans genes with European and Amerindian genes in this population. The results revealed increased frequencies of the DRB1*03-DQA1*0501-DQB1*02 and DRB1*0401-DQA1*03-DQB1*0302 haplotypes in the patient group The highest risk for type I diabetes was associated with the heterozygote DRB1*03/*04 genotype as largely reported, and DRB1*03/X and DRB1*04/Y genotypes conferred a significant, but much lower disease risk. Protection from type I diabetes revealed some peculiarities in Southeastern Brazilians: a lack of significant protecting effect of the DRB1*1501-DQA1*0102-DQB1*0602 haplotype, and an apparent protection conferred by the DRB1*13-DQB1*0301, DRB1*11-DQB1*0301, and DRB1*01-DQB1*0501 two-locus haplotypes. The risk to type I diabetes in the highly diversified Southeastern Brazilians evidenced specific information to the prediction of the disease in this region of the country.

[T-cell-depleted HLA non-identical bone marrow transplantation in the child: prevention of graft-versus-host reaction by administration of donor T lymphocytes alloreactive against the recipient]

The success of HSCT from HLA partially disparate donors depends on the development of new strategies able to efficiently prevent GVHD and to protect patients from infections and relapse. Using an immunotoxin (IT) directed against the alpha-chain (p55) of the human IL-2r (RFT5-SMPT-dgA), we have previously shown that it is possible to kill mature T cells activated towards a specific HLA complex by a one-way MLR. We designed a clinical trial assessing the effect of infusing increasing doses of T lymphocytes in the setting of children recipients of non HLA genetically identical HSCT. Thirteen patients have been enrolled from September 1998 to April 2000 and fourteen HSCT have been realized in 13 patients (pts). Donors were MUD in 3 cases and familial HLA partially disparate in the remaining cases. Allodepleted donor T cells were injected between day +14 and day +30 provided that ATG was undetectable in the serum and blood PMN counts was > 500/microliter. The mean age of these patients was 17 months (range 1 to 42). Diagnosis included immune deficient and malignant hemopathies. Three patients received 1 x 10(5) allodepleted T cell/kg, 7 patients received 4 x 10(5)/kg and 4 patients received 6 x 10(5)/kg allodepleted T cells. Full inhibition of MLR was achieved in 12 out of 14 cases. In two cases, a residual T cell reactivity to the recipient was observed (4 to 5%) and patients developed grade II aGVHD. aGVHD occurred in 4 out of 11 grafted patients (all grade II). No chronic GVHD has developed, so far. Three patients died from severe VOD or PHT at day +34, day 51 and day +166, while one infected patient by VZV, CMV and EBV before HSCT died 6 months after transplantation from meningoencephalitis and another patient died from relapse at day +291. The patient for which there was no engraftment died at day +48 from staphylococcus infection. Overall survival is 54%, with a median follow up of 8 months; the mean time to reach a blood lymphocyte count > 500 was 41 days, to reach a CD3 count > 300 microliters 63 days (20-111), CD4 > 200 microliters 97 days and positive mitogen-induced proliferation 90 days. In three patients, a tetanus-toxoid positive proliferation was detected before immunization. From this intermediate analysis, we conclude that 1) specific allodepletion is an effective approach to prevent aGVHD in a haploincompatible setting, 2) data on immunological reconstitution suggest that infused T cells do survive and expand. A higher number of patients must be enrolled to determine the optimal number of T cells to infuse.

A dinucleotide repeat polymorphism at the poly(ADP-ribose) polymerase gene is not associated with predisposition to type 1 diabetes in French Caucasians

The poly (ADP-ribose) polymerase (PARP) is a nuclear enzyme that detects and binds DNA strand breaks. Excessive PARP activation leads to the death of mice islet beta-cells by depleting cellular energy reserves. On the other hand, PARP-mutant mice are resistant to streptozotocine-induced diabetes, and in the non-obese diabetic (NOD) mouse model, treatment with nicotinamide, a PARP inhibitor, protects islet cells against cytotoxic actions in vitro and results in a decreased incidence of type 1 diabetes. PARP gene in human is located within a recently identified type 1 diabetes-susceptibility region on chromosome 1q41-42, and contains a polymorphic CA dinucleotide repeat in the promoter region. To consider the putative involvement of PARP polymorphism in predisposition to type 1 diabetes, we performed genotyping for the various alleles of the CA dinucleotide repeat in 158 unrelated French Caucasian patients with type 1 diabetes and 193 ethnically-matched healthy controls. We found no significant difference of PARP alleles distribution between patients and controls, even after stratification of the patients according to HLA class II genotype or to age at disease onset. Our results suggest that this PARP polymorphism does not influence susceptibility to type 1 diabetes in French Caucasians.

Influence of HLA-DR phenotype on the risk of hepatitis C virus-associated mixed cryoglobulinemia

OBJECTIVE

Circumstances predisposing hepatitis C virus (HCV)-infected patients to develop mixed cryoglobulinemia (MC), which may manifest as a small-vessel systemic vasculitis (MC vasculitis), remain unclear. Previous studies have failed to demonstrate a clear role of either viral factors (genotype, viral load) or host factors (lymphocytes or immunoglobulin subsets). This study was undertaken to examine a possible role of HLA class II alleles in HCV-associated MC.

METHODS

One hundred fifty-eight HCV-infected patients, of whom 76 had MC (56 with type II MC and 20 with type III MC) and 82 did not have MC, were studied prospectively. MC vasculitis was noted in 35 HCV-infected patients with type II IgMkappa-containing cryoglobulins. HLA-DRB1 and HLA-DQB1 polymorphism was analyzed by hybridization using allele-specific oligonucleotides, after gene amplification. The odds ratio (OR) was calculated with Woolf's method. Then, using multivariate analysis, demographic, biologic, immunologic, virologic, and liver histologic factors associated with the presence of MC and MC vasculitis were investigated.

RESULTS

HLA-DR11 was significantly more frequent in patients with type II MC than in those without MC (41.1% versus 17.1%; OR 3.4, corrected P [Pcorr] = 0.017), regardless of the presence of vasculitis accompanying the MC (37.1% of those with MC vasculitis, 34.1% of those with MC but no vasculitis). HLA-DR7 was less frequent in HCV-infected patients with MC than in those without MC (13.2% versus 30.5%; OR 0.34, P = 0.012, Pcorr not significant), with a particularly lower frequency in those with type II MC and those with MC vasculitis (12.5% and 8.6%, respectively). There was no significant difference in HLA-DQB1 distribution between the different patient groups. By univariate and multivariate analysis, HLA-DR11 was the only positive predictive factor, besides female sex and advanced age, for the presence of MC and HCV-associated MC vasculitis (OR 2.58).

CONCLUSION

Our results indicate that the presence of the DR11 phenotype is associated with a significantly increased risk for the development of type II MC in patients with chronic HCV infection. In contrast, HLA-DR7 appears to protect against the production of type II MC. These results suggest that the host's immune response genes may play a role in the pathogenesis of HCV-associated MC.

Maternally inherited diabetes and deafness: a multicenter study

BACKGROUND

Maternally inherited diabetes and deafness (MIDD), which is seen in 0.5% to 2.8% of patients with type 2 diabetes mellitus, is related to a point mutation at position 3243 of mitochondrial (mt) DNA. Its clinical description is incomplete.

OBJECTIVE

To study the clinical presentation and complications of diabetes in patients with MIDD and to identify clinical characteristics that may help select diabetic patients for mtDNA mutation screening.

DESIGN

Multicenter prospective descriptive study.

SETTING

16 French departments of internal medicine, diabetes and metabolic diseases, or both.

PATIENTS

54 patients with type 2 diabetes mellitus and the mtDNA 3243 mutation.

MEASUREMENTS

Characteristics of diabetes, metabolic control (glycosylated hemoglobin level), complications of diabetes, and involvement of other organs.

RESULTS

On average, patients with MIDD were young at diabetes onset and presented with a normal or low body mass index. None were obese. Seventy-three percent of probands had a maternal family history of diabetes. Diabetes was non-insulin-dependent at onset in 87% of patients; however, 46% of patients had non-insulin-dependent disease at onset but progressed to insulin therapy after a mean duration of approximately 10 years. Neurosensory hearing loss was present in almost all patients. Eighty-six percent of patients who received an ophthalmologic examination had macular pattern dystrophy (a specific retinal lesion). Forty-three percent of patients had myopathy, 15% had cardiomyopathy, and 18% (9 of 51) had neuropsychiatric symptoms. Although the prevalence of diabetic retinopathy was 8% among patients who received an ophthalmologic examination, lower than expected after a mean 12-year duration of diabetes, prevalence of kidney disease was 28%. This suggests that a specific renal involvement was the result of mitochondrial disease.

CONCLUSIONS

Maternally inherited diabetes and deafness has a specific clinical profile that may help identify diabetic patients for mtDNA testing.

A common stromal cell-derived factor-1 chemokine gene variant is associated with the early onset of type 1 diabetes

Type 1 diabetes results from the autoimmune destruction of pancreatic beta-cells. Although the disease shows a strong association with HLA class II alleles, other genes may influence the initiation or the rate of progression of the autoimmune process. The recruitment of mononuclear cells within the islets of Langerhans is a critical step in the pathogenesis of the disease. Because chemokines are cytokines that promote migration of mononuclear cells, we hypothesized that polymorphisms in chemokine receptor or chemokine genes, CCR5 and SDF1, may be involved in susceptibility to or clinical expression of type 1 diabetes. The frequencies of the CCR5-delta32 and SDF1-3'A (801G-->A in the 3' untranslated region) variants were similar in 208 unrelated Caucasian patients with type 1 diabetes and in 120 Caucasian control subjects. They were not modified after stratification for the predisposing HLA-DR3 and -DR4 haplotypes. However, the SDF1-3'A variant was strongly associated with early onset (< 15 years) of the disease (odds ratio 2.6, P = 0.0019). On average, the presence of the SDF1-3'A allele was associated with a 5-year reduction in the age at onset of diabetes (P = 0.0067). Our results suggest that stromal cell-derived factor-1 may be implicated in the aggressiveness of the autoimmune process leading to type 1 diabetes. These preliminary data require replication in other populations.

HLA-B*51 and B*15 alleles confer predisposition to Behçet's disease in Moroccan patients

HLA class I polymorphism in Moroccan patients with Behçet's disease has not been investigated so far. In this study, HLA-B* phenotype frequencies were analyzed in 86 unrelated Moroccan patients (45 males, 41 females) and 111 ethnically matched healthy controls. The predisposing effect of the B*51 was confirmed (30.2% in patients and 15.3% in controls, OR = 2.39, 95% CI [1.2-4.8], p = 0.015). It was mostly observed in males with young age at disease onset (OR= 5.5 [1.9-15.9], p = 0.002 compared to controls). The Moroccan BD group also presented a previously unknown association with HLA-B*15 (25.6% of patients versus 11.7% of controls, OR = 2.59 [1.2-5.5], p = 0.014), both in females and in males with late-onset of the disease. Altogether, the B*15 and/or B*51 alleles were expressed in 55.8% of patients compared to 27% of controls (OR = 3.4 [1.9-6.2], p < 10-4, Pc = 0.003). Our data indicate HLA-B effects on BD pathogenesis should be considered separately for men and women.

Lack of evidence of a specific role for C4A gene deficiency in determining disease susceptibility among C4-deficient patients with systemic lupus erythematosus (SLE)

The aim of the present study was to investigate the prevalence of C4 and C2 deficiencies and to characterize genomic alterations in C4 genes in a large cohort of 125 unselected patients with SLE. We determined the protein concentration and functional activity of C2 and C4, as well as the C4 phenotype. C4 genotyping included Taq 1 restricted fragment lengh polymorphism (RFLP) analysis and polymerase chain reaction using sequence-specific primers (SSP-PCR). Type I C2 deficiency was diagnosed by PCR. Overall, 79.2% of the patients exhibited abnormalities of the C4 genes including deletion, non-expression, gene conversion and duplication. Among C4-deficient patients (n = 66, 52.8% prevalence), 41.0% of the patients exhibited a C4A deficiency and 59.0% a C4B deficiency. Half of the C4 deficiencies were due to a gene deletion. There was a strong association between C4A and C4B gene deletion and the presence of the DRB1*03 allele. Among the silent C4A genes, only two cases were related to a 2-bp insertion in exon 29 of the C4A gene. A gene conversion was demonstrated in eight patients (6.4%). One patient had a homozygous C4A deficiency. Three (2.4%) patients presented with a heterozygous type I C2 deficiency and none with homozygous deficiency. Our results argue against a specific role for C4A gene deficiency in determining disease susceptibility among patients with SLE that are C4-deficient.

Focal segmental glomerulosclerosis associated with mitochondrial cytopathy

BACKGROUND

The nonspecific lesion of focal segmental glomerulosclerosis (FSGS) can occur as a primary disease or in a variety of secondary settings. In mitochondrial cytopathies (MCs), the phenotypic expression of the disease depends on the degree of cellular dysfunction, and this correlates with the proportion of abnormal mitochondrial DNA in the cells and the dependence of tissues on oxidative metabolism. The most common renal manifestation in MCs is tubular dysfunction; little has been reported about glomerular diseases.

METHODS

Cases of four adult patients with FSGS and MC are reported. Routine histology and mitochondrial DNA analysis were carried out on renal biopsies.

RESULTS

Family history and clinical manifestations in the four patients with FSGS suggested a diagnosis of MC. An A3243G transition in the mitochondrial DNA tRNA(leu(UUR)) was found in lymphocytes and kidney. Glomerular lesions of FSGS were associated with unusual hyaline lesions, which appeared to represent individual myocyte necrosis in afferent arterioles and small arteries.

CONCLUSION

FSGS is a renal manifestation of MCs. The renal lesion can precede other manifestations of the genetic disease by many years. The striking arteriolar lesions in these cases may have resulted in glomerular hypertension and hyperperfusion, leading to secondary epithelial cell abnormalities and, ultimately, FSGS. However, primary epithelial cell dysfunction caused by mitochondrial defects could not be ruled out on morphological grounds. MCs should be considered in cases of so-called primary FSGS, particularly if there is a familial history of diabetes, neuromuscular disorders, or deafness.

Structural analysis of two HLA-DR-presented autoantigenic epitopes: crucial role of peripheral but not central peptide residues for T-cell receptor recognition

Specific and major histocompatibility complex (MHC)-restricted T-cell recognition of antigenic peptides is based on interactions of the T-cell receptor (TCR) with the MHC alpha helices and solvent exposed peptide residues termed TCR contacts. In the case of MHC class II-presented peptides, the latter are located in the positions p2/3, p5 and p7/8 between MHC anchor residues. For numerous epitopes, peptide substitution studies have identified the central residue p5 as primary TCR contact characterized by very low permissiveness for peptide substitution, while the more peripheral positions generally represent auxiliary TCR contacts. In structural studies of TCR/peptide/MHC complexes, this has been shown to be due to intimate contact between the TCR complementarity determining region (CDR) three loops and the central peptide residue. We asked whether this model also applied to two HLA-DR presented epitopes derived from an antigen targeted in type 1 diabetes. Large panels of epitope variants with mainly conservative single substitutions were tested for human leukocyte antigen (HLA) class II binding affinity and T cell stimulation. Both epitopes bind with high affinity to the presenting HLA-DR molecules. However, in striking contrast to the standard distribution of TCR contacts, recognition of the central p5 residue displayed high permissiveness even for non-conservative substitutions, while the more peripheral p2 and p8 TCR contacts showed very low permissiveness for substitution. This suggests that intimate TCR interaction with the central peptide residue is not always required for specific antigen recognition and can be compensated by interactions with positions normally acting as auxiliary contacts.

Clinical characteristics of type 2 diabetes in patients with mutations of HFE

Genetic hemochromatosis (GH) is associated with two mutations of the HFE gene (Cys282Tyr and His63Asp). Heterozygosity for GH is associated with a mild increase in iron metabolism parameters, and increased iron stores are associated with abnormal glucose tolerance and decreased insulin sensitivity in the general population. We have previously shown that the frequency of the two HFE mutations is not increased in patients with type 2 diabetes. However, to assess whether the presence of HFE mutations modulates the clinical presentation of type 2 diabetes, we studied the clinical characteristics and iron metabolism indexes according to the presence of the two mutations in 266 patients with type 2 diabetes. The Cys282Tyr mutation and the His63Asp mutation were present in 9. 8% and 26% of the patients, respectively. Serum iron, transferrin saturation and ferritin concentrations were significantly increased in patients expressing either HFE mutations, compared to those without any mutation. There was no difference in the clinical characteristics in the two groups except that obesity was significantly less frequent in the patients with at least one mutation than in those without any mutation (27.6% vs 42.8%, p=0.02). This finding suggests that, in the absence of obesity, HFE mutations, through the insulin resistance associated with the increase in iron stores, may contribute to the onset of type 2 diabetes.

Linkage and association study of the CTLA-4 region in coeliac disease for Italian and Tunisian populations

Coeliac disease (CD) is a multifactorial disease for which there is an intensive search for genetic risk factors. Some authors found an association between the CTLA-4 region and CD. In the present work, we investigate the possible implication of the CTLA-4 region as a genetic risk factor for CD, through two statistical approaches: the maximum likelihood score (MLS) test in a large Italian sample of affected sib-pairs using polymorphic genetic markers on chromosome 2, and the transmission disequilibrium test (TDT) in continental Italian and Tunisian families using the CTLA-4 exon 1 49 A/G polymorphism. None of these approaches provides evidence for linkage or association between the CTLA-4 region and CD. This might result from a difference in the CTLA-4 region from population to population, either in its involvement as a risk factor or in the strength of linkage disequilibrium.

Tapasin enhances assembly of transporters associated with antigen processing-dependent and -independent peptides with HLA-A2 and HLA-B27 expressed in insect cells

Assembly of HLA class I-peptide complexes is assisted by multiple proteins that associate with HLA molecules in loading complexes. These include the housekeeping chaperones calnexin and calreticulin and two essential proteins, the transporters associated with antigen processing (TAP) for peptide supply, and the protein tapasin which is thought to act as a specialized chaperone. We dissected functional effects of processing cofactors by co-expressing in insect cells various combinations of the human proteins HLA-A2, HLA-B27, beta(2)-microglobulin, TAP, calnexin, calreticulin, and tapasin. Stability at 37 degrees C and surface expression of class I dimers correlated closely in baculovirus-infected Sf9 cells, suggesting that these cells retain empty dimers in the endoplasmic reticulum. Both HLA molecules form substantial quantities of stable complexes with insect cell-produced peptide pools. These pools are TAP-selected cytosolic peptides for HLA-B27 but endoplasmic reticulum-derived, i.e. TAP-independent peptides for HLA-A2. This discrepancy may be due to peptide selection by human TAP which is much better adapted to the HLA-B27 than to the HLA-A2 ligand preferences. HLA class I assembly with peptides from TAP-dependent and -independent pools was enhanced strongly by tapasin. Thus, tapasin acts as a chaperone and/or peptide editor that facilitates assembly of peptides with HLA class I molecules independently of mediating their interaction with TAP and/or retention in the endoplasmic reticulum.

[Recent findings on the genetics of Behçet's disease]

Behçet's disease is a systemic inflammatory disease with a multifactorial genetic and environmental pathogenesis. The main factor of genetic predisposition is located in the HLA region. The disease is significantly linked with the HLA-B51 antigen in different ethnic groups. Recently, a linkage with MICA gene polymophism has been evidenced. This gene, located 46 kb centromerically from the HLA-B gene, codes for a non-classic HLA class I protein induced by stress and probably plays an important role in the destruction of cells targeted by Tgd lymphocytes. The functional significance of this polymorphism in Behçet's disease remains unclear.

Identification of peptides from autoantigens GAD65 and IA-2 that bind to HLA class II molecules predisposing to or protecting from type 1 diabetes

Type 1 diabetes is a T-cell-mediated disease in which presentation of autoantigens to CD4+ T-cells is thought to play a crucial role. Polymorphism of HLA class II genes accounts for 50% of the genetic risk of contracting type 1 diabetes. HLA-DQ and -DR molecules predisposing to or protecting from type 1 diabetes have been identified, but the molecular basis controlling these associations is as yet undefined. Apart from distinct thymic selection of autoreactive T-cells by susceptible and protective HLA molecules, exclusive presentation of autoantigenic peptides by type 1 diabetes-predisposing HLA molecules or, alternatively, induction of regulatory T-cells by protective alleles are potential mechanisms for modification of type 1 diabetes risk by HLA polymorphism. As a first step in exploring the role of HLA molecules in autoantigen-specific cellular responses in type 1 diabetes, we have screened peptides covering the sequence of two major autoantigens targeted by humoral and cellular immune responses, GAD65 and islet associated-2 (IA-2), for binding to class II molecules. We developed a sensitive novel competition binding assay allowing us to measure peptide binding on intact cells to 10 HLA-DR and 4 HLA-DQ molecules. For all tested alleles, multiple peptides binding with high affinity were identified. We report clustering of binding peptides in the COOH-terminal regions of GAD65 and IA-2, as well as highly promiscuous binding patterns of some peptides. Our results demonstrate that most peptides derived from the GAD and IA-2 autoantigens can bind to both type 1 diabetes-predisposing and type 1 diabetes-protective HLA molecules, although some exceptions were observed. The binding inventory presented here for GAD and IA-2 peptides can be useful for mapping natural epitopes and predicting peptide-specific responses induced by preventive immunization.

Prevalence of macular pattern dystrophy in maternally inherited diabetes and deafness. GEDIAM Group

OBJECTIVE

To evaluate the prevalence of macular pattern dystrophy (MPD) in maternally inherited diabetes and deafness (MIDD), a new subtype of diabetes mellitus that cosegregates with a mutation of mitochondrial DNA (i.e., the substitution of guanine for adenine at position 3243 of leucine transfer RNA) and to report the clinical characteristics of MPD.

DESIGN

Prospective cohort study.

PARTICIPANTS

Forty-six patients from 29 families with an adenine-to-guanine mutation of mitochondrial DNA were recruited from a French collaborative multicenter study. Thirty-five patients had MIDD, 8 were asymptomatic children of MIDD patients, and 3 had MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes). The 33 MIDD patients with diabetes were matched for diabetes duration and gender with 33 patients with "common" type-2 diabetes to compare the prevalence of diabetic retinopathy (DR) in both series.

METHODS

All patients had a full ophthalmologic examination and fundus photographs.

MAIN OUTCOME MEASURES

The presence and severity of MPD and DR were assessed in each patient.

RESULTS

Thirty MIDD patients (85.7%) of 35 exhibited bilateral MPD characterized by linear pigmentation surrounding the macula and optic disc. In 24 of these 30 patients, visual acuity was 20/25 or more in both eyes. The prevalence of DR was 6% in MIDD patients with diabetes versus 15% for patients with common type-2 diabetes (a difference that was not significant, P = 0.23). The fundus of each of the eight asymptomatic children was normal. MPD was present in one of the three cases of MELAS.

CONCLUSION

The prevalence of MPD in MIDD is high. Its detection may be helpful for the diagnosis of this new subtype of diabetes, for which specific treatments may be proposed.

New class I and II HLA alleles strongly associated with opposite patterns of progression to AIDS

The genetics of resistance to infection by HIV-1 cohort consists of 200 slow and 75 rapid progressors to AIDS corresponding to the extremes of HIV disease outcome of 20,000 Caucasians of European descent. A comprehensive analysis of HLA class I and class II genes in this highly informative cohort has identified HLA alleles associated with fast or slow progression, including several not described previously. A quantitative analysis shows an overall HLA influence independent of and equal in magnitude (for the protective effect) to the effect of the CCR5-Delta32 mutation. Among HLA class I genes, A29 (p = 0.001) and B22 (p < 0.0001) are significantly associated with rapid progression, whereas B14 (p = 0.001) and C8 (p = 0.004) are significantly associated with nonprogression. The class I alleles B27, B57, C14 (protective), and C16, as well as B35 (susceptible), are also influential, but their effects are less robust. Influence of class II alleles was only observed for DR11. These results confirm the influence of the immune system on disease progression and may have implications on peptide-based vaccine development.

Distinctive effects of CCR5, CCR2, and SDF1 genetic polymorphisms in AIDS progression

The Genetics of Resistance to Infection by HIV-1 (GRIV) cohort represents 200 nonprogressor/slow-progressor (Slowprog) and 90 fast-progressor (Fastprog) HIV-1-infected patients. Using this unique assembly, we performed genetic studies on three recently discovered polymorphisms of CCR5, CCR2, and SDF1, which have been shown to slow the rate of disease progression. The increased prevalence of mutant alleles among Slowprogs from the GRIV cohort was significant for CCR5 (p < .0001) but not for CCR2 (p = .09) or SDF1 (p = . 12), emphasizing the predominant role of CCR5 as the major HIV-1 coreceptor. However, the prevalence of the CCR2 mutant allele (64I) was significantly increased among Slowprogs homozygous for wild-type CCR5 compared with Fastprogs (p = .04). The prevalence of double mutants SDF1-3'A/3'A genotypes was also increased among Slowprogs homozygous for wild-type CCR5 compared with Fastprogs (p = .05). The effects of the CCR2 and SDF1 mutations are overshadowed by the protective effects of the CCR5 deletion. Predictive biologic markers such as CD4 cell counts or viral load in the Slowprog population did not show significant differences between Slowprog groups with wild-type or mutant alleles for the three genes. Thus, our data suggest that the effects of these genes are exerted earlier in infection and no longer evident in the Slowprog of the GRIV cohort whose average duration of HIV infection is 12 years. We conclude that these genes, whose products serve as viral coreceptors or their ligands, may play a role early in infection and delay the onset of disease. However, among Slowprogs, whose duration of infection is >8 years, they are no longer influential for maintenance of their longterm nonprogression status. Other genetic determinants may be responsible for late protective effects.

CTLA-4 gene polymorphism is associated with predisposition to coeliac disease

BACKGROUND

Susceptibility to coeliac disease is strongly associated with particular HLA class II alleles. However, non-HLA genetic factors are likely to be required for the development of the disease. Among candidate genes is the CTLA-4 (cytotoxic T lymphocyte associated) gene located on chromosome 2q33 in humans, which encodes a cell surface molecule providing a negative signal for T cell activation.

AIMS

To investigate CTLA-4 exon 1 polymorphism (position 49 A/G) in patients with coeliac disease.

PATIENTS

101 patients with coeliac disease and 130 healthy controls.

METHODS

Allele specific hybridisation and restriction enzyme digestion of polymerase chain reaction amplified genomic DNA.

RESULTS

The A allele of the CTLA-4 position 49 polymorphism was found on 82.2% of chromosomes in patients with coeliac disease compared with 65.8% in controls (p < 0.0001), mostly in the homozygous form (68.3% in patients versus 47.7% in controls; odds ratio (OR) 2.36, 95% confidence interval (CI) 1.37 to 4.06, p = 0.002). Four patients only had the G/G genotype compared with 21 controls (OR 0.21, CI 10.07 to 0.64, p = 0.002). These differences were maintained when subjects were stratified according to the HLA class II phenotype, in particular when patients and controls were matched for the presence of the predisposing HLA DQB1*02 (DQ2) allele or HLA-DQA1*0501/DQB1*02 heterodimer.

CONCLUSION

The CTLA-4 gene polymorphism is a non-HLA determinant that predisposes to coeliac disease. Whether it directly contributes to disease susceptibility or represents a marker for a locus in linkage disequilibrium with CTLA-4 needs further investigation.

Relationship between peptide selectivities of human transporters associated with antigen processing and HLA class I molecules

Efficiency of presentation of a peptide epitope by a MHC class I molecule depends on two parameters: its binding to the MHC molecule and its generation by intracellular Ag processing. In contrast to the former parameter, the mechanisms underlying peptide selection in Ag processing are poorly understood. Peptide translocation by the TAP transporter is required for presentation of most epitopes and may modulate peptide supply to MHC class I molecules. To study the role of human TAP for peptide presentation by individual HLA class I molecules, we generated artificial neural networks capable of predicting the affinity of TAP for random sequence 9-mer peptides. Using neural network-based predictions of TAP affinity, we found that peptides eluted from three different HLA class I molecules had higher TAP affinities than control peptides with equal binding affinities for the same HLA class I molecules, suggesting that human TAP may contribute to epitope selection. In simulated TAP binding experiments with 408 HLA class I binding peptides, HLA class I molecules differed significantly with respect to TAP affinities of their ligands. As a result, some class I molecules, especially HLA-B27, may be particularly efficient in presentation of cytosolic peptides with low concentrations, while most class I molecules may predominantly present abundant cytosolic peptides.