Young age and HLA markers enhance the risk of progression to type 1 diabetes in antibody-positive siblings of diabetic children

Risk for progression to type 1 diabetes in first-degree relatives under 50 years of age

Introduction

The detection of pancreatic autoantibodies in first-degree relatives of patients with type 1 diabetes (T1D) is considered a risk factor for disease. Novel available immunotherapies to delay T1D progression highlight the importance of identifying individuals at risk who might benefit from emerging treatments. The objective was to assess the autoimmunity in first-degree relatives of patients with T1D, estimate the time from autoimmunity detection to the onset of clinical diabetes, and identify the associated risk factors.

Methods

Retrospective multicenter study of 3,015 first-degree relatives of patients with T1D recruited between 1992 and 2018. Pancreatic autoantibodies (IAA, GADA, IA2A, and ZnT8A) were determined by radioimmunoassay, starting the analyses at diagnosis of the proband. All those with positive autoimmunity and normal fasting blood glucose without clinical symptoms of diabetes were followed up in the study. The progression rate to T1D was assessed according to sex, relationship with the proband, age at autoimmunity detection, type/number of autoantibodies, and HLA-DRB1 genotype. Cox proportional-hazard models and Kaplan-Meier survival plots were used for statistical analyses.

Results

Among the relatives, 21 progenitors [43.7 years (IQR: 38.1-47.7)] and 27 siblings [7.6 years (IQR: 5.8-16.1)] had positive autoantibodies. Of these, 54.2% (95% CI: 39.2%-68.6%) developed T1D (age at autoimmunity detection 11 months to 39 years) in a median of 5 years (IQR: 3.6-8.7; ranged from 0.9 to 22.6 years). Risk factors associated with faster progression to T1D were multiple autoimmunity and <20 years at autoimmunity detection. Younger relatives (<20 years) with multiple autoantibodies had a 5-year cumulative risk of developing diabetes of 52.9% (95% CI: 22.1%-71.6%) and a 20-year risk of 91.2% (95% CI: 50.5%-98.4%). The 20-year risk decreased to 59.9% (95% CI: 21.9%-79.5%) if only one risk factor was met and to 35.7% (95% CI: 0.0%-66.2%) if the relative was older than 20 years with one autoantibody.

Conclusions

In first-degree relatives with autoimmunity, the time to progression to T1D is faster in children and adolescents with multiple autoantibodies. Young adults are also at risk, which supports their consideration in screening strategies for people at risk of developing T1D.

Newly-onset Autoimmune Diabetes Mellitus Triggered by COVID 19 Infection: A Case-based Review

The devastating global pandemic Coronavirus disease 2019 (COVID 19) isolated in China in January 2020 is responsible for an outbreak of pneumonia and other multisystemic complications. The clinical picture of the infection has extreme variability: it goes from asymptomatic patients or mild forms with fever, cough, fatigue and loss of smell and taste to severe cases ending up in the intensive care unit (ICU). This is due to a possible cytokine storm that may lead to multiorgan failure, septic shock, or thrombosis. Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV -2), which is the virus that causes COVID 19, binds to angiotensin-converting enzyme 2 (ACE2) receptors, which are expressed in key metabolic organs and tissues, including pancreatic beta cells, adipose tissue, the small intestine and the kidneys. Therefore it is possible to state that newly-onset diabetes is triggered by COVID 19 infection. Although many hypotheses have clarified the potential diabetogenic effect of COVID 19, a few observations were reported during this pandemic. Two male patients admitted to us with devastating hyperglycemia symptoms were diagnosed with type 1/autoimmune diabetes mellitus within 3 months following COVID 19 infection. Autoantibodies and decreased C peptide levels were detected in these patients. We speculated that several mechanisms might trigger autoimmune insulitis and pancreatic beta-cell destruction by COVID 19 infection. We aim to raise awareness of the possible link between SARS-CoV-2 and newly onset type 1 diabetes mellitus. Further studies are needed to determine a more definitive link between the two clinical entities.

Investigating the role of T-cell avidity and killing efficacy in relation to type 1 diabetes prediction

During the progression of the clinical onset of Type 1 Diabetes (T1D), high-risk individuals exhibit multiple islet autoantibodies and high-avidity T cells which progressively destroy beta cells causing overt T1D. In particular, novel autoantibodies, such as those against IA-2 epitopes (aa1-577), had a predictive rate of 100% in a 10-year follow up (rapid progressors), unlike conventional autoantibodies that required 15 years of follow up for a 74% predictive rate (slow progressors). The discrepancy between these two groups is thought to be associated with T-cell avidity, including CD8 and/or CD4 T cells. For this purpose, we build a series of mathematical models incorporating first one clone then multiple clones of islet-specific and pathogenic CD8 and/or CD4 T cells, together with B lymphocytes, to investigate the interaction of T-cell avidity with autoantibodies in predicting disease onset. These models are instrumental in examining several experimental observations associated with T-cell avidity, including the phenomenon of avidity maturation (increased average T-cell avidity over time), based on intra- and cross-clonal competition between T cells in high-risk human subjects. The model shows that the level and persistence of autoantibodies depends not only on the avidity of T cells, but also on the killing efficacy of these cells. Quantification and modeling of autoreactive T-cell avidities can thus determine the level of risk associated with each type of autoantibodies and the timing of T1D disease onset in individuals that have been tested positive for these autoantibodies. Such studies may lead to early diagnosis of the disease in high-risk individuals and thus potentially serve as a means of staging patients for clinical trials of preventive or interventional therapies far before disease onset.

The three ZNT8 autoantibody variants together improve the diagnostic sensitivity of childhood and adolescent type 1 diabetes

AIMS

We tested whether autoantibodies to all three ZnT8RWQ variants, GAD65, insulinoma-associated protein 2 (IA-2), insulin and autoantibodies to islet cell cytoplasm (ICA) in combination with human leukocyte antigen (HLA) would improve the diagnostic sensitivity of childhood type 1 diabetes by detecting the children who otherwise would have been autoantibody-negative.

METHODS

A total of 686 patients diagnosed in 1996-2005 in Skåne were analyzed for all the seven autoantibodies [arginin 325 zinc transporter 8 autoantibody (ZnT8RA), tryptophan 325 zinc transporter 8 autoantibody (ZnT8WA), glutamine 325 Zinc transporter 8 autoantibody (ZnT8QA), autoantibodies to glutamic acid decarboxylase (GADA), Autoantibodies to islet-antigen-2 (IA-2A), insulin autoantibodies (IAA) and ICA] in addition to HLA-DQ genotypes.

RESULTS

Zinc transporter 8 autoantibody to either one or all three amino acid variants at position 325 (ZnT8RWQA) was found in 65% (449/686) of the patients. The frequency was independent of age at diagnosis. The ZnT8RWQA reduced the frequency of autoantibody-negative patients from 7.5 to 5.4%-a reduction by 28%. Only 2 of 108 (2%) patients who are below 5 years of age had no autoantibody at diagnosis. Diagnosis without any islet autoantibody increased with increasing age at onset. DQA1-B1(*)X-0604 was associated with both ZnT8RA (p = 0.002) and ZnT8WA (p = 0.01) but not with ZnT8QA (p = 0.07). Kappa agreement analysis showed moderate (>0.40) to fair (>0.20) agreement between pairs of autoantibodies for all combinations of GADA, IA-2A, ZnT8RWQA and ICA but only slight ( < 0.19) agreement for any combination with IAA.

CONCLUSIONS

This study revealed that (1) the ZnT8RWQA was common, independent of age; (2) multiple autoantibodies were common among the young; (3) DQA1-B1(*)X-0604 increased the risk for ZnT8RA and ZnT8WA; (4) agreement between autoantibody pairs was common for all combinations except IAA. These results suggest that ZnT8RWQA is a necessary complement to the classification and prediction of childhood type 1 diabetes as well as to randomize the subjects in the prevention and intervention of clinical trials.

[Susceptibility markers in Tunisian first-degree relatives of patients with type 1 diabetes]

To identify the profile of anti-pancreas autoantibodies and elucidate the HLA DRB1, DQB1 polymorphism in Tunisian first-degree relatives of patients with type 1 diabetes, we recruited 96 relatives from 21 families with at least one diabetic child. Islet cell antibodies (ICA) were detected by immunofluorescence on monkey pancreas; glutamate decarboxylase (GADA), IA2 (IA2-A) and insulin (IAA) antibodies were measured by RIA. HLA class II DRB1 and DQB1 alleles were typed by PCR-SSP. ICA, GADA, IA2-A and IAA were found in respectively 11.5, 4.2, 5.2 and 8.3% of relatives. Twenty-two out of 96 had at least one antibody and 20 out of these 22 had a susceptibility allele (DRB1*03, DRB1*04, DQB1*02 or DQB1*0302) with or without protective allele (DRB1*11, DRB1*13, DRB1*15 or DQB1*06). All of the 5 relatives having 2 autoantibodies or more carried the DRB1*04-DQB1*0302 susceptible haplotype. In conclusion, this observational study confirms in a Tunisian population known epidemiological data and demonstrates the usefulness of follow-up to determine the predictive value of studied markers.

Developments in the prediction of type 1 diabetes mellitus, with special reference to insulin autoantibodies

The prodromal phase of type 1 diabetes is characterised by the appearance of multiple islet-cell related autoantibodies (Aab). The major target antigens are islet-cell antigen, glutamic acid decarboxylase (GAD), protein-tyrosine phosphatase-2 (IA-2) and insulin. Insulin autoantibodies (IAA), in contrast to the other autoimmune markers, are the only beta-cell specific antibodies. There is general consensus that the presence of multiple Aab (> or = 3) is associated with a high risk of developing diabetes, where the presence of a single islet-cell-related Aab has usually a low predictive value. The most commonly used assay format for the detection of Aab to GAD, IA-2 and insulin is the fluid-phase radiobinding assay. The RBA does not identify or measure Aab, but merely detects its presence. However, on the basis of molecular studies, disease-specific constructs of GAD and IA-2 have been employed leading to somewhat improved sensitivity and specificity of the RBA. Serological studies have shown epitope restriction of IAA that can differentiate diabetes-related from unrelated IAA, but current assays do not distinguish between disease-predictive and non-predictive IAA or between IAA and insulin antibodies (IA). More recently, phage display technology has been successful in identifying disease-specific anti-idiotopes of insulin. In addition, phage display has facilitated the in vitro production of antibodies with high affinity. Identification of disease-specific anti-idiotopes of insulin should enable the production of a high affinity reagent against the same anti-idiotope. Such a development would form the basis of a disease-specific radioimmunoassay able to identify and measure particular idiotypes, rather than merely detect and titrate IAA.

The role of HLA class I gene variation in autoimmune diabetes

The use of DNA-based genetic typing has enabled the identification of type 1 diabetes mellitus (T1DM) susceptible and protective major histocompatibility complex (MHC) class II alleles and haplotypes. The application of this approach has also progressed to locate MHC class I alleles that contribute to the clinicopathology of T1DM. Recent studies have shown a widespread involvement of genes from the MHC class I gene region in the clinicopathology of T1DM. These genes are shown to be involved in contributing to progression from the preclinical stage of the disease, which is characterized by the occurrence of islet-specific antibodies, to clinical disease and also to the occurrence of autoimmunity. They can either contribute directly to disease development or indirectly in concert with other susceptible MHC class II alleles or haplotypes via linkage disequilibrium. Class I alleles may also be negatively associated with T1DM. These findings are useful for the development of future strategies in designing tolerogenic approaches for the prevention or even reversal of T1DM. In this article, the latest evidence for the different kinds of participation of HLA class I genes in the etiology of T1DM is reviewed. A meta-analysis which included existing association studies was also carried out in order to re-assess the relevance of class I genes in diabetes development. The analysis of an enlarged heterogeneous sample confirmed the involvement of previously detected serotypes in the etiology of T1DM, such as A24, B8 and B18, and revealed hitherto unknown associations with B60 and B62. The analysis points out that much of the conflicting results of previous association studies originate from inadequate sample sizes and accentuate the value of future investigations of larger samples for identifying linkage in multigenic diseases.

Genetics of type 1A (immune mediated) diabetes

Type 1A (immune mediated) diabetes is genetically heterogeneous with important examples for man and animal models with major mutations (autosomal recessive and X-linked recessive) identified as well as oligogenic/polygenic inheritance. For the most common forms of type 1A diabetes alleles of DQ and DR within the major histocompatibility complex are important determinants of disease and allow identification of high risk individuals at birth. Further understanding of both common and rare genetic determinants of type 1A diabetes will contribute to understanding the pathogenesis of diabetes and of autoimmunity.

Genetic risk determines the emergence of diabetes-associated autoantibodies in young children

Timing of onset of autoimmunity is a prerequisite for unmasking triggers and pathogenesis of type 1 diabetes. We followed 4,590 consecutive newborns with 8 or 3% HLA-DQB1 conferred risk for type 1 diabetes at 3-, 6-, or 12-month intervals up to 5.5 years of age. Islet cell autoantibodies (ICAs) and, in the 137 children with ICAs, insulin autoantibodies (IAAs), GAD65 autoantibodies (GADAs), and IA-2 protein autoantibodies (IA-2As) were measured. Children with high genetic risk developed ICAs more often than those with moderate risk (log-rank P = 0.0015); 85 and 91% remained ICA negative by 5 years of age, respectively. The time of appearance of biochemical autoantibodies was then compared with the appearance of ICAs. IAAs and GADAs emerged usually before ICAs (means -1.8 and -1.5 months, respectively) and IA-2As after ICAs (mean 2.0 months). Ninety-five percent of all IAAs, GADAs, and IA-2As seroconversions occurred in a cluster (-12 to 8 months) around the ICA seroconversion. We conclude that diabetes-associated autoantibodies emerged in children with predisposing HLA-DQB1 alleles after 3 months of age at a constant tempo, determined by the genetic risk level, usually in the order of IAA, GADA, ICA, and IA-2A. Seroconversion to multiple autoantibody positivity usually occurred tightly clustered in time.

Autoantibodies to GAD, IA-2 and insulin in ICA-positive first-degree relatives of children with type 1 diabetes: a comparison between parents and siblings

BACKGROUND

Islet cell antibodies (ICA) represent a heterogenous group of autoantibodies to diabetes-associated antigens, including glutamic acid decarboxylase (GAD) and the IA-2 protein. The objectives of the present study were to compare the prevalence of autoantibodies to known biochemically characterized autoantigens between ICA-positive non-diabetic parents and siblings of children with type 1 diabetes and to evaluate how such antibodies explain ICA reactivity.

METHODS

The presence and levels of GAD antibodies (GADA), IA-2 antibodies (IA-2A) and insulin autoantibodies (IAA) were analyzed in the sera of 184 ICA-positive first-degree relatives (79 parents and 105 siblings).

RESULTS

The prevalences of GADA (61.9% in siblings vs 32.9% in parents), IA-2A (55.2% vs 15.2%) and IAA (41.0% vs 0%) were increased among ICA-positive siblings relative to ICA-positive parents (p<0.001). The siblings had higher ICA titers (p<0.001) than the parents but tended to have lower GADA levels (p=0.12). IA-2A levels did not differ between the two groups. IA-2A levels explained a higher proportion of the ICA reactivity in the siblings than in the parents (44% vs 12%, p=0.004), and GADA levels had the same tendency (27% vs 10%, p=0.11). In a multiple regression analysis, GADA and IA-2A were found to explain together 16% of the ICA reactivity in parents and 49% in siblings (p=0.003 for the difference).

CONCLUSIONS

These results indicate that the increased frequency of additional diabetes-associated autoantibodies in ICA-positive siblings when compared to their ICA-positive parents may reflect the increased risk of progression to clinical type 1 diabetes previously reported in young ICA-positive relatives. We conclude that ICA immunofluorescence is not only due to GADA and IA-2A, but there are other additional antigens contributing to the ICA reactivity. Antibodies to such antigens appear to be more common among adults than in children.

Disease-associated autoantibodies as predictive markers of type 1 diabetes mellitus in siblings of affected children

The long latent preclinical period of type 1 diabetes mellitus (DM) makes it possible to identify individuals at increased risk for clinical DM before the beta-cell destructive process has reached the point of no return. A series of reports on the predictive value of DM-associated autoantibodies are available in first-degree relatives of patients with type 1 DM, but only a few of these studies target exclusively siblings and young siblings of affected children. When planning screening of siblings for DM risk, their age needs to be considered, as predictive characteristics of autoantibodies seem to vary in different age groups. Autoimmunity may be initiated early in life and therefore early screening for signs of beta-cell autoimmunity is crucial to avoid missing young children en route to overt DM and to be able to start intervention, when clinically applicable preventive modalities become available, before the disease process has advanced too far. Young age, positivity for at least two autoantibodies, high levels of autoantibodies and low first phase insulin response are highly predictive for progression to clinical disease in initially unaffected siblings of children with type 1 DM.