An unselected population of 755 siblings of children with insulin-dependent diabetes mellitus (IDDM) was studied to evaluate the predictive characteristics of islet cell antibodies (ICA), antibodies to the IA-2 protein (IA-2A), antibodies to the 65-kD isoform of glutamic acid decarboxylase (GADA), insulin autoantibodies (IAA), and combinations of these markers. We also evaluated whether the histochemical ICA test could be replaced by the combined detection of other markers. 32 siblings progressed to IDDM within 7.7 yr of the initial sample taken at or close to the diagnosis of the index case (median follow-up, 9.1 yr). The positive predictive values of ICA, IA-2A, GADA, and IAA were 43, 55, 42, and 29%, and their sensitivities 81, 69, 69, and 25%, respectively. In contrast to the other three antibody specificities, GADA levels were not related to the risk for IDDM. The risk for IDDM in siblings with four, three, two, one, or no antibodies was 40, 70, 25, 2, and 0.8%, respectively. Combined screening for IA-2A and GADA identified 70% of all ICA-positive siblings, and all of the ICA-positive progressors were also positive for at least one of the three other markers. The sensitivity of the combined analysis of IA-2A and GADA was 81%, and the positive predictive value was 41%. In conclusion, combined screening for IA-2A and GADA may replace the ICA assay, giving comparable sensitivity, specificity, and positive predictive value. Accurate assessment of the risk for IDDM in siblings is complicated, as not even all those with four antibody specificities contract the disease, and some with only one or no antibodies initially will progress to IDDM.

Previous studies suggest that enterovirus infections may initiate and accelerate ␤-cell damage years before the clinical manifestation of type 1 diabetes. We have now analyzed the role of enterovirus infections in the initiation of autoimmunity in children who have tested positive for diabetes-associated autoantibodies in a prospective study starting at birth (the Finnish Diabetes Prediction and Prevention Study). The frequency of enterovirus infections was studied using both serology and testing for the presence of enterovirus RNA in the sera of 21 children who developed and retained autoantibodies and in 104 control subjects chosen from the same study cohort and matched for the time of birth, sex, and HLA alleles determining genetic diabetes susceptibility. Sample intervals were taken as basic units of follow-up, to which the observed number of infections was adjusted. Enterovirus infections were detected in 26% of sample intervals in the case subjects and in 18% of the sample intervals in the control children (P = 0.03). A temporal relationship between enterovirus infections and the induction of autoimmunity was found; enterovirus infections were detected in 57% of the case subjects during a 6-month follow-up period preceding the first appearance of autoantibodies compared with 31% of the matched control children in the same agegroup (odds ratio 3.7, 95% CI 1.2-11.4). The frequency of adenovirus infections did not differ between the patient and control groups. Our data imply that enterovirus infections are associated with the development of ␤-cell autoimmunity and provide evidence for the role of enteroviruses in the initiation of ␤-cell destruction. Diabetes 49:1314-1318, 2000 T he etiology of type 1 diabetes comprises both genetic and environmental components. Enterovirus infections have long been suspected as potential environmental factors playing a role in the pathogenesis of type 1 diabetes (1,2). Recent prospective studies, based on enterovirus serology (3-5) and detection of enterovirus RNA in sera of prediabetic children (6), suggest that enterovirus infections may initiate and accelerate the ␤-cell-damaging process years before the clinical manifestation of type 1 diabetes. Enterovirus RNA has also been detected more frequently in patients with newly diagnosed type 1 diabetes than in healthy control subjects (7-9).Clear signs of ␤-cell damage often appear months or years before the manifestation of clinical diabetes (10), suggesting that prospective studies starting before the appearance of autoantibodies may be helpful in studying the etiology of the disease. In addition, early recognition of the individuals with ongoing ␤-cell damage may make it possibile to delay or halt ␤-cell destruction. The Finnish Diabetes Prediction and Prevention (DIPP) Study is a prospective population-based birth-cohort study in which Finnish children with increased genetic risk for type 1 diabetes are studied for the appearance of diabetes-associated autoantibodies at 3-to 12-month intervals from birth. We have now stud...

Abbreviations: GADA, GAD autoantibodies; IA-2A, autoantibodies to the protein tyrosine phosphatase-related IA-2 molecule; IAA, insulin autoantibodies; ICA, islet cell antibodies; JDF U, Juvenile Diabetes Foundation units; RU, relative units.A OBJECTIVE -To assess whether there are any differences in genetic, autoimmune, or clinical features between type 1 diabetes presenting in childhood and that diagnosed later.RESEARCH DESIGN AND METHODS -We studied 352 individuals (252 children and adolescents Ͻ20 years of age and 100 adults Ն20 years of age) manifesting clinical signs of type 1 diabetes over a period of 7.5 years at a university hospital in northern Finland with a primary catchment area population of ϳ300,000. The patients were analyzed for susceptible and protective HLA-DQB1 alleles (*02, *0302, *0301, *0602, *0603, and *0604), islet cell antibodies (ICA), insulin autoantibodies, and antibodies to GAD and IA-2 (IA-2A). Their clinical symptoms and signs were recorded at diagnosis.RESULTS -The adult patients carried the high-risk DQB1*02/0302 genotype less frequently than the children and more often had protective genotypes. They also had a decreased frequency of all 4 single autoantibody specificities and of multiple (Ն3) autoantibodies. The proportion of patients testing negative for all autoantibodies was lower among the children than among the adults. IA-2A were associated with the DQB1*0302/x genotype in both the children and adults, and the same held true for ICA among the adults. The adults were characterized by a higher proportion of males, a longer duration of symptoms, and a lower frequency of infections during the preceding 3 months. In addition, they had a higher relative body weight on admission and milder signs of metabolic decompensation (higher pH, base excess, and bicarbonate concentrations) and a lower glycated hemoglobin level at diagnosis than the children.CONCLUSIONS -Clinical manifestation of type 1 diabetes before the age of 20 years is associated with a strong HLA-defined genetic disease susceptibility, an intensive humoral immune response to various ␤-cell antigens, a higher frequency of preceding infections, and a shorter duration of symptoms and more severe metabolic decompensation at diagnosis. Taken together, these observations suggest that the age at clinical onset of type 1 diabetes is determined by the intensity of the ␤-cell-destructive process, which is modulated by both genetic and environmental factors.

To study the relationship of IA-2 antibodies (IA-2A) to other autoantibodies and genetic risk markers in insulin-dependent diabetes mellitus (IDDM), 758 children and adolescents younger than 15 years of age (mean age 8.4 years) with newly diagnosed diabetes were analysed for IA-2A, GAD antibodies (GADA) and insulin autoantibodies (IAA) with radiobinding assays, for islet cell antibodies (ICA) with immunofluorescence and for HLA DR alleles by serology. IA-2A were detected in 85.9% of cases with no association with gender or age. An overwhelming majority of the patients (71.3%) tested positive for three or more antibodies, and 90.7% for at least two. Fifty-four subjects (7.1%) had one antibody detectable, whereas only 2.1% of the patients tested negative for all four. A higher proportion of patients was positive for IA-2A and/or GADA than for ICA alone (95.5 vs 84.2%, p < 0.001). The prevalence and level of IA-2A were increased in cases carrying HLA DR4/non-DR3 compared with other DR combinations. The results indicate that almost all patients with newly diagnosed childhood IDDM can be identified by screening with these four autoantibodies. The combination of IA-2A and/or GADA had a higher sensitivity for IDDM than ICA alone. The close association between IA-2A and HLA DR4, the strongest single allele predisposing to IDDM, suggests that IA-2A may be a more specific marker of beta-cell destruction than GADA, which have been shown to associate with the DR3 allele and thyroid autoimmunity.

Type I (insulin-dependent) diabetes mellitus is closely related to both cellular and humoral immune responses to insulin-producing beta cells [1]. Prediabetic patients often have autoantibodies against islet antigens [1] that are perceived as markers of beta-cell damage and at the time of diagnosis almost all children and adolescents with diabetes test antibody positive [2]. Little is known, however, about the persistence of these autoantibodies after clinical diagnosis. Islet cell antibodies (ICA) and antibodies to the 65 kDa isoform of glutamic acid decarboxylase (GADA) have been observed to persist after the clinical diagnosis of Type I diabetes, and with highly fluctuating concentrations for GADA [3,4]. Antibodies to the protein tyrosine phosphatase related IA-2 antigen (IA-2A) have been detected in cross-sectional analyses of patients with long-term Type I diabetes [5]. We studied the persistence of ICA, GADA and IA-2A and their relationship to clinical characteristics and genetic risk markers in a longitudinal 10-year study in 90 children and adolescents with Type I diabetes. Diabetologia (1998) Summary To study the persistence of Type I (insulindependent) diabetes mellitus associated autoantibodies and their relation to genetic risk markers and clinical characteristics of the disease after clinical manifestation, serum samples were obtained from 90 children and adolescents at diagnosis and 2, 5 and 10 years later. The samples were analysed for islet cell antibodies (ICA) by immunofluorescence and for antibodies to glutamic acid decarboxylase (GADA), intracellular portion of the protein tyrosine phosphatase related IA-2 antigen (IA-2A) and insulin autoantibodies by specific radiobinding assays. Of the subjects tested 79 % were positive for IA-2A at diagnosis, 62 % for GADA, 81 % for ICA and 28 % for insulin autoantibodies, but the prevalence of IA-2A, GADA and ICA decreased substantially as a function of increasing duration of the disease (p < 0.05 or less), their levels following the same pattern (p < 0.001 for all three autoantibodies).Two thirds of the subjects still tested positive for at least one autoantibody specificity after the first 10 years of the disease and 42 % had two or three antibodies detectable. An increase over the initial antibody concentrations after the diagnosis was seen more often for GADA than for ICA (p < 0.001) or IA-2A (p < 0.05). In conclusion, autoantibodies associated with Type I diabetes appear to persist longer than expected after manifestation of the clinical disease, possibly due to small scale continuous beta-cell regeneration after diagnosis or to structural and/or functional mimicry between exogenous proteins and beta-cell antigens or both. [Diabetologia (1998)