INTRODUCTION:Insulin autoantibodies (IAA) are key predictors of type 1 diabetes, particularly in young children. Micro-radiobinding assays (RBA) are the gold standard for IAA measurement but have limitations. We assessed whether a luciferase immunoprecipitation system (LIPS) assay improved diabetes risk assessment. METHODS:To validate LIPS compared with RBA, samples from people with new-onset type 1 diabetes (n = 150) and first-degree relatives (FDRs) (n = 619), of whom 91 had developed diabetes during follow-up, were used. This cross-sectional observational data was analysed using the area under the receiver operator characteristic curve and cox-proportional hazard models. RESULTS:In new-onset diabetes, RBA and LIPS showed 88% agreement in IAA status. Positive IAA LIPS was more common in 89 FDRs with high-moderate affinity IAA (61%) compared with 22 FDRs with low-affinity IAA (18%) (p < 0.001). In FDRs positive for multiple other islet autoantibodies, 20-year diabetes risk was 80% for those positive compared with 30% for those negative for IAA by LIPS (p = 0.013). IAA LIPS added to diabetes risk independently of status/level of IAA by RBA, other autoantibodies and sampling age (p < 0.001). CONCLUSION:The IAA LIPS low-blood-volume, high-throughput technique identifies more individuals with the highest risk of diabetes. The ability to identify high-affinity IAA makes LIPS an ideal method for future clinical trials and population screening strategies to predict the risk of diabetes.

OBJECTIVE:The Islet Autoantibody Standardization Program (IASP) evaluates type 1 diabetes autoantibody assays through international interlaboratory comparison studies. This report describes 2024 IASP workshop results for multiplex assays that simultaneously measure multiple islet autoantibodies, increasingly adopted for population screening programs. RESEARCH DESIGN AND METHODS:Participating laboratories analyzed coded sera from individuals with new-onset type 1 diabetes (n = 50), blood donors with no diabetes (n = 98), and replicate samples (n = 3). Performance was assessed using sensitivity, specificity, adjusted sensitivity at 95%, 99%, and 100% specificity, area under the receiver operating characteristic curve analysis (ROC-AUC), and partial ROC-AUC at 95% specificity (pAUC95). RESULTS:Fifteen laboratories contributed results from 19 multiplex assays using five formats: antibody-dependent agglutination PCR (ADAP) (n = 6), bridge-ELISA (n = 8), electrochemiluminescence (n = 2), luciferase immunoprecipitation system (LIPS) (n = 1), and protein A luciferase/solid-phase capture LIPS (n = 2). Median ROC-AUC was 0.98 across all platforms, with a pAUC95 of 0.048 against a theoretical maximum of 0.05. Laboratory-reported sensitivity ranged from 86% to 96% with specificity 81% to 100%. Standardized adjusted sensitivity at 99% specificity thresholds eliminated most false positives without compromising sensitivity, achieving 93-97% adjusted sensitivity. Bridge-ELISA platforms demonstrated potential for universal cutoff standardization, while ADAP showed substantial interlaboratory threshold variation. CONCLUSIONS:Multiplex assays demonstrated good overall performance for detecting islet autoantibodies and discriminating case subjects from control subjects. However, interlaboratory variability and platform-specific recognition patterns necessitate further standardization efforts. While not directly tested in this workshop, the results suggest that sequential testing strategies using complementary platforms may be necessary to achieve the stringent specificity required when these assays are used in a screening context.

Diurnal Variation of Islet Autoantibody Titers in Established Type 1 Diabetes Suggests Restricted-Time Sampling Improves Aab Measurement and Detection Diurnal islet autoantibody (Aab) variation in type 1 diabetes (T1D) remains poorly understood and could hinder efforts to develop, test and refine new therapies. We sought to describe the extent and pattern of diurnal variation in islet autoantibodies and, having found significant variation, translate to the clinical setting. We conducted two studies in human subjects with established T1D: (1) a prospective study (n = 10) of the range of islet autoantibody and immunoglobulin daily variation within humans and (2) an independent retrospective, cross-sectional study (n = 705) of the effect of time of sample collection on Aab titer and detection in clinical settings. We found that some individuals have wide Aab variations during the day and which can exceed expected levels of inter-assay variation. For some Aab, this variation followed a circadian pattern. We also found that, in clinical settings, time-restricted sampling can lead to increased IA-2A and ZnT8A detection within specific age-groups. We conclude that time-restriction can potentially improve the use of Radiobinding-measured Aabs as biomarkers for the development and monitoring of disease-modifying therapies and in developing islet transplantation strategies in established T1D. Investigation of diurnal Aab variation and time restriction is needed in early-stage disease. .

Aim: This study aimed to evaluate characteristics of autoimmunity in individuals who have a type 2 diagnosis and are relatives of children with type 1 diabetes. Methods: Pre-diagnosis samples (median 17 months before onset) from relatives who were later diagnosed with type 2 diabetes were measured for autoantibodies to glutamate decarboxylase 65 (GADA), islet antigen-2 (IA-2A), zinc transporter 8 (ZnT8A) and insulin (IAA) as well as the type 1 diabetes genetic risk score (GRS2). Associations between islet autoantibodies, insulin treatment and GRS2 were analysed using Fisher's exact and t-tests. Results: Among 226 relatives (64% men; mean age at sampling 41 years; mean age 54 years at diagnosis), 32 (14%) were islet autoantibody-positive for at least one autoantibody more than a decade before diagnosis. Approximately half of these (n = 15) were treated with insulin. GADA-positivity was higher in insulin-treated relatives than in non-insulin-treated relatives (12/18 [67%] vs. 6/18 [33%], p < 0.001). IAA-positivity was observed in 13/32 (41%) of relatives with autoantibodies. GRS2 scores were increased in autoantibody-positive relatives (p = 0.032), but there was no clear evidence for a difference according to treatment (p = 0.072). Conclusion: This study highlights the importance of measuring islet autoantibodies, including IAA, in relatives of people with type 1 diabetes to avoid misdiagnosis.

Objective: C-peptide and islet autoantibodies are key type 1 diabetes biomarkers, typically requiring venous sampling, which limit their utility. We assessed transdermal capillary blood (TCB) collection as a practical alternative. Research Design and methods: Ninety-one individuals (71 type 1 diabetes, 20 controls; type 1 diabetes: aged median 14.8 years[interquartile range 9.1-17.1]; diabetes duration 4.0 years[1.5-7.7]; controls 42.2 years[38.0-52.1]) underwent contemporaneous venous and TCB sampling for measurement of plasma C-peptide. Type 1 diabetes participants also provided venous serum and plasma, and TCB plasma for measurement of autoantibodies to glutamate decarboxylase, islet antigen-2, and zinc transporter 8. The ability of TCB plasma to detect significant endogenous insulin secretion (venous C-peptide ≥200pmol/L) was compared along with agreement in levels using Bland-Altman. Venous serum was compared with venous and TCB plasma for detection of autoantibodies using established thresholds. Acceptability was assessed by age-appropriate questionnaire. Results: Transdermal sampling took a mean of 2.35minutes (SD 1.49). Median sample volume was 50 µl(IQR 40-50) with 3/91(3.3%) failures, and 13/88(14.7%) <35 µL). TCB C-peptide showed good agreement to venous plasma (mean venous ln(C-peptide) – TCB ln(C-peptide) = 0.008, 95% CI(-0.23, 0.29), with 100%(36/36) sensitivity/100%(50/50) specificity to detect venous C-peptide ≥ 200pmol/L. Where venous serum in multiple autoantibody positive TCB plasma agreed in 22/32 (sensitivity 69%), comparative specificity was 35/36 (97%). TCB was preferred to venous sampling (type 1 diabetes: 63% vs 7%; 30% undecided). Conclusions: Transdermal capillary testing for C-peptide is a sensitive, specific, and acceptable alternative to venous sampling, TCB sampling for islet autoantibodies needs further assessment.

Autoantibodies to glutamate decarboxylase (GADA) are widely used in the prediction and classification of type 1 diabetes. GADA radiobinding assays (RBAs) using N-terminally truncated antigens offer improved specificity but radioisotopes limit the high-throughput potential for population screening. Luciferase-based Immunoprecipitation System (LIPS) assays are sensitive and specific alternatives to RBAs with the potential to improve risk stratification. The performance of assays using the Luciferase (Nluc-) conjugated GAD 65 constructs, Nluc-GAD65(96-585) and full length Nluc-GAD65(1-585) were evaluated in 434 well-characterised sera from recent-onset type 1 diabetes patients and first-degree relatives. Non-radioactive, high-throughput LIPS assays are quicker and require less serum than RBAs. Of 171 relatives previously tested single autoantibody positive for autoantibodies to full-length GAD 65 by RBA but had not progressed to diabetes, fewer retested positive by LIPS using either truncated (n=72) or full-length (n=111) antigen. The Nluc-GAD65(96-585) truncation demonstrated the highest specificity in LIPS assays overall but in contrast to RBA, N-terminus truncations did not result in a significant increase in disease-specificity compared with the full-length antigen. This suggests that binding of non-specific antibodies is affected by the conformational changes resulting from addition of the Nluc antigen. Nluc-GAD65(96-585) LIPS assays offer low blood volume, high specificity GADA tests for screening and diagnostics.

Abstract We investigated whether characterisation of full-length (f-)GADA responses could identify early insulin requirement in adult-onset diabetes. In 179 f-GADA positive participants diagnosed with type 2 diabetes, we assessed associations of truncated (t-)GADA positivity, f-GADA IgG subclasses, and f-GADA affinity with early insulin requirement (<5 years), type 1 diabetes genetic risk score (T1D GRS), and C-peptide. t-GADA positivity was lower in f-GADA positive without early insulin in comparison to f-GADA positive type 2 diabetes requiring insulin within 5 years, and type 1 diabetes (75% vs. 91% and 95% respectively, p<0.0001). t-GADA positivity (in those f-GADA positive) identified a group with a higher type 1 diabetes genetic susceptibility (mean T1D GRS 0.248 vs. 0.225, p=0.003), lower C-peptide (1156 pmol/L vs. 4289 pmol/L, p=1x10-7), and increased IA-2A positivity (23% vs. 6%, p=0.03). In survival analysis, t-GADA positivity was associated with early insulin requirement compared with those only positive for f-GADA, independently from age of diagnosis, f-GADA titre and duration of diabetes [adjusted HR 5.7 (95% CI 1.4, 23.5), p=0.017]. The testing of t-GADA in f-GADA positive individuals with type 2 diabetes identifies those who have genetic and clinical characteristics comparable to type 1 diabetes and stratifies those at higher risk of early insulin requirement. Article Highlights · Progression to insulin therapy is highly variable in adult-onset GADA positive diabetes. · We further characterised GADA in adult-onset diabetes and assessed whether these are associated with early insulin requirement. · Truncated GADA positivity was associated with a type 1 diabetes like phenotype and stratified risk of early insulin requirement. Those GADA positive who were negative for truncated GADA had the characteristics and progression of classic type 2 diabetes. Assessing full-length GADA IgG subclass and affinity did not further stratify risk of progression. · t-GADA assessment remains underutilised in clinical practice, but could assist correct therapy allocation in adult-onset diabetes.

Coronavirus disease-19 (COVID-19) causes immune perturbations which may persist long term, and patients frequently report ongoing symptoms for months after recovery. We assessed immune activation at 3–12 months post hospital admission in 187 samples from 63 patients with mild, moderate, or severe disease and investigated whether it associates with long COVID. At 3 months, patients with severe disease displayed persistent activation of CD4+ and CD8+ T-cells, based on expression of HLA-DR, CD38, Ki67, and granzyme B, and elevated plasma levels of interleukin-4 (IL-4), IL-7, IL-17, and tumor necrosis factor-alpha (TNF-α) compared to mild and/or moderate patients. Plasma from severe patients at 3 months caused T-cells from healthy donors to upregulate IL-15Rα, suggesting that plasma factors in severe patients may increase T-cell responsiveness to IL-15-driven bystander activation. Patients with severe disease reported a higher number of long COVID symptoms which did not however correlate with cellular immune activation/pro-inflammatory cytokines after adjusting for age, sex, and disease severity. Our data suggests that long COVID and persistent immune activation may correlate independently with severe disease.

In very rare cases of monoclonal gammopathy, insulin-binding paraprotein can cause disabling hypoglycaemia. We report a 67-year-old man re-evaluated for hyperinsulinaemic hypoglycaemia that persisted despite distal pancreatectomy. He had no medical history of diabetes mellitus or autoimmune disease but was being monitored for an IgG kappa monoclonal gammopathy of undetermined significance. On glucose tolerance testing, hyperglycaemia occurred at 60 min (glucose 216 mg/dL) and hypoglycaemia at 300 min (52 mg/dL) concurrent with an apparent plasma insulin concentration of 52 850 pmol/L on immunoassay. Laboratory investigation revealed an IgG2 kappa with very high binding capacity but low affinity (Kd 1.43 x 10-6 mol/L) for insulin. The monoclonal gammopathy was restaged as smouldering myeloma not warranting plasma cell-directed therapy from a haematological standpoint. Plasma exchange reduced paraprotein levels and improved fasting capillary glucose concentrations. Lenalidomide was used to treat disabling hypoglycaemia, successfully depleting paraprotein and leading to resolution of symptoms.

Objective Proteomic profiling can identify useful biomarkers. Monozygotic(MZ) twins, discordant for a condition represent an ideal test population. We aimed to investigate and validate proteomic profiling in twins with type 1 diabetes and in other well characterised cohorts. Research Design and Methods A broad, multiplex analysis of 4068 proteins in sera from MZ twins concordant (n=43) and discordant for type 1 diabetes (n=27) identified major differences which were subsequently validated by a trypsin(ogen) assay in MZ pairs concordant (n=39) and discordant (n=42) for type 1 diabetes, individuals at-risk (n=195) and with type 1 diabetes (n=990), as well as with non-insulin requiring adult-onset diabetes diagnosed as either autoimmune (n=96) or type 2 (n=291). Results Proteomic analysis identified major differences between exocrine enzyme levels in discordant MZ twin pairs despite strong correlation between twins, whether concordant or discordant for type 1 diabetes (p<0.01 for both). In validation experiments, trypsin(ogen) levels were lower in twins with diabetes compared with non-diabetic co-twins (p<0.0001) and healthy controls (p<0.0001). In recently-diagnosed cases, trypsin(ogen) levels were lower than in controls across a broad age range. In at-risk relatives, levels <15 ng/ml were associated with increased risk of progression (uncorr. p=0.009). Multiple linear regression in recently-diagnosed cases showed that trypsin(ogen) levels were associated with insulin dose and diabetic ketoacidosis while age and BMI were confounders. Conclusions Type 1 diabetes is associated with altered exocrine function, even before onset. Twin data suggest roles for genetic and non-genetically determined factors. Exocrine/endocrine interactions are important under-investigated factors in type 1 diabetes.

Aims/hypothesis The Islet Autoantibody Standardization Program (IASP) aims to improve the performance of immunoassays measuring autoantibodies in type 1 diabetes and the concordance of results across laboratories. IASP organises international workshops distributing anonymised serum samples to participating laboratories and centralises the collection and analysis of results. In this report, we describe the results of assays measuring IAA submitted to the IASP 2018 and 2020 workshops. Methods The IASP distributed uniquely coded sera from individuals with new-onset type 1 diabetes, multiple islet autoantibody-positive individuals, and diabetes-free blood donors in both 2018 and 2020. Serial dilutions of the anti-insulin mouse monoclonal antibody HUI-018 were also included. Sensitivity, specificity, area under the receiver operating characteristic curve (ROC-AUC), partial ROC-AUC at 95% specificity (pAUC95) and concordance of qualitative/quantitative results were compared across assays. Results Results from 45 IAA assays of seven different formats and from 37 IAA assays of six different formats were submitted to the IASP in 2018 and 2020, respectively. The median ROC-AUC was 0.736 (IQR 0.617–0.803) and 0.790 (IQR 0.730–0.836), while the median pAUC95 was 0.016 (IQR 0.004–0.021) and 0.023 (IQR 0.014–0.026) in the 2018 and 2020 workshops, respectively. Assays largely differed in AUC (IASP 2018 range 0.232–0.874; IASP 2020 range 0.379–0.924) and pAUC95 (IASP 2018 and IASP 2020 range 0–0.032). Conclusions/interpretation Assay formats submitted to this study showed heterogeneous performance. Despite the high variability across laboratories, the in-house radiobinding assay (RBA) remains the gold standard for IAA measurement. However, novel non-radioactive IAA immunoassays showed a good performance and, if further improved, might be considered valid alternatives to RBAs. Graphical abstract

Objective We investigated whether further characterisation of full-length (f-) GADA responses could identify early insulin requirement in adult-onset diabetes. Research Design and Methods In 179 f-GADA positive participants diagnosed with type 2 diabetes, we assessed the association of truncated (t-)GADA positivity, f-GADA IgG subclasses, and f-GADA IgG affinity with early insulin requirement (<5 years), type 1 diabetes genetic risk score (T1D GRS), and C-peptide. These characteristics were compared to f-GADA positive type 1 diabetes (n=141) and f-GADA negative type 2 diabetes (n=6420) cohorts. Results t-GADA positivity was lower in f-GADA positive without early insulin in comparison to f-GADA positive type 2 diabetes requiring insulin within 5 years, and type 1 diabetes (75% vs. 91% and 95% respectively, p<0.0001). t-GADA positivity (in those f-GADA positive) identified a group with a higher type 1 diabetes genetic susceptibility (mean T1D GRS 0.248 vs. 0.225, p=0.003), lower C-peptide (1156 pmol/L vs. 4289 pmol/L, p=1x10-7), and increased IA-2A positivity (23% vs. 6%, p=0.03). In survival analysis, t-GADA positivity was associated with early insulin requirement compared with those only positive for f-GADA, independently from age of diagnosis, f-GADA titre and duration of diabetes [adjusted HR 5.7 (95% CI 1.4, 23.5), p=0.017]. Early insulin requirement was not associated with an IgG1-restricted f-GADA response (p=0.81) or a high affinity f-GADA response (p=0.89). Conclusions The testing of t-GADA in f-GADA positive individuals with type 2 diabetes identifies those who have genetic and clinical characteristics comparable to type 1 diabetes and stratifies those at higher risk of early insulin requirement.

Background Saliva is easily obtainable non-invasively and potentially suitable for detecting both current and previous SARS-CoV-2 infection, but there is limited evidence on the utility of salivary antibody testing for community surveillance. Methods We established 6 ELISAs detecting IgA and IgG antibodies to whole SARS-CoV-2 spike protein, to its receptor binding domain region and to nucleocapsid protein in saliva. We evaluated diagnostic performance, and using paired saliva and serum samples, correlated mucosal and systemic antibody responses. The best-performing assays were field-tested in 20 household outbreaks. Results We demonstrate in test accuracy ( N = 320), spike IgG (ROC AUC: 95.0%, 92.8–97.3%) and spike IgA (ROC AUC: 89.9%, 86.5–93.2%) assays to discriminate best between pre-pandemic and post COVID-19 saliva samples. Specificity was 100% in younger age groups (0–19 years) for spike IgA and IgG. However, sensitivity was low for the best-performing assay (spike IgG: 50.6%, 39.8–61.4%). Using machine learning, diagnostic performance was improved when a combination of tests was used. As expected, salivary IgA was poorly correlated with serum, indicating an oral mucosal response whereas salivary IgG responses were predictive of those in serum. When deployed to household outbreaks, antibody responses were heterogeneous but remained a reliable indicator of recent infection. Intriguingly, unvaccinated children without confirmed infection showed evidence of exposure almost exclusively through specific IgA responses. Conclusions Through robust standardisation, evaluation and field-testing, this work provides a platform for further studies investigating SARS-CoV-2 transmission and mucosal immunity with the potential for expanding salivo-surveillance to other respiratory infections in hard-to-reach settings.

Background: Zinc transporter 8 autoantibodies (ZnT8A) are thought to appear close to type 1 diabetes (T1D) onset and can identify high-risk multiple (>= 2) autoantibody positive individuals. Radiobinding assays (RBA) are widely used for ZnT8A measurement but have limited sustainability. We sought to develop a novel, high-performance, non-radioactive luciferase immunoprecipitation system (LIPS) assay to replace RBA. Methods: A custom dual C-terminal ZnT8 (aa268-369; R325/W325) heterodimeric antigen, tagged with a Nanoluciferase (TM) (Nluc-ZnT8) reporter, and LIPS assay was developed. Assay performance was evaluated by testing sera from new onset T1D (n = 573), healthy schoolchildren (n = 521), and selected first-degree relatives (FDRs) from the Bart's Oxford family study (n = 617; 164 progressed to diabetes). Results: In new-onset T1D, ZnT8A levels by LIPS strongly correlated with RBA (Spearman's r = 0.89; P < 0.0001), and positivity was highly concordant (94.3%). At a high specificity (95%), LIPS and RBA had comparable assay performance [LIPS pROC-AUC(95) 0.032 (95% CI: 0.029-0.036); RBA pROC-AUC(95) 0.031 (95% CI: 0.028-0.034); P = 0.376]. Overall, FDRs found positive by LIPS or RBA had a comparable 20-year diabetes risk (52.6% and 59.7%, respectively), but LIPS positivity further stratified T1D risk in FDRs positive for at least one other islet autoantibody detected by RBA (P = 0.0346). Conclusion: This novel, high-performance, cheaper, quicker, higher throughput, low blood volume Nluc-ZnT8 LIPS assay is a safe, non-radioactive alternative to RBA with enhanced sensitivity and ability to discriminate T1D progressors. This method offers an advanced approach to current strategies to screen the general population for T1D risk for immunotherapy trials and to reduce rates of diabetic ketoacidosis at diagnosis.

COVID-19 causes immune perturbations which may persist long-term, and patients frequently report ongoing symptoms for months after recovery. We assessed the extent and nature of immune activation at 3 months post hospital admission in patients with mild, moderate or severe COVID-19 and investigated whether immune activation associates with disease severity and long COVID. Patients with severe disease displayed persistent activation of CD4+ and CD8+ T-cells, based on expression of HLA-DR, CD38, Ki67 and granzyme B, but they lacked activation of other immune subsets. Elevated plasma levels of IL-4, IL-7, IL- 17 and TNF- were present in patients with severe compared to mild and/or moderate disease. Plasma from severe patients caused T-cells from healthy donors to upregulate IL-15R, suggesting that factors in the plasma of severe patients may increase T-cell responsiveness to IL-15-driven bystander" activation, which may drive persistent T-cell activation after severe COVID-19. Patients with severe disease reported a higher number of long COVID symptoms which correlated with the frequency of two subsets of activated CD4+ and CD8+ T cells (CD4+ T-cell population 2 and CD8+ T-cell population 4; FDR p<0.05), however these associations were lost after adjusting for age, sex and disease severity. Our data suggests that persistent immune activation and long COVID correlate independently with severe disease.