Increased levels of anti-BSA antibodies in children with Down syndrome.

Introduction: Autoimmune diabetes occurs more often in the first 2 years of life in children with Down syndrome (DS) compared with the general population. We previously observed increased frequencies of islet autoantibodies, including insulin autoantibodies (IAA), in children with DS. Assays for IAA using 125I-labelled insulin require competition to overcome cross reactivity with antibodies to the cow's milk protein, bovine serum albumin (BSA). 125I-IAA assay results suggested that levels of antibodies to BSA may also be increased in children with DS. The aim of this study therefore was to determine whether the levels of anti-BSA antibodies differed in children with DS compared with controls. Methods: Samples were available from two populations with DS: one from the UK, (UK DS cohort n=106, 58 male, median age 12.5 years) and one from Estonia (Estonian DS cohort: n=121, 65 male, median age 9.75 years). A UK control population was provided by sex and age-matched healthy siblings of probands participating in the Bart's Oxford (BOX) family study of type 1 diabetes. A competitive-displacement radiobinding assay (RBA) and a Dissociation Enhanced Lanthanide Fluoroimmunoassay (DELFIA) were developed to measure and confirm anti-BSA antibody levels. HLA class II genotype was analysed by PCR using sequence specific primers (PCR-SSP). Results: Overall, levels of anti-BSA antibodies were increased in those with DS compared with controls (p<0.0001) but this was not HLA associated. Conclusion: Increased levels of anti-BSA antibodies may reflect a defect in immune maturation or increased gut permeability in children with DS, increasing their risk of developing autoimmunity.

Patients with down syndrome have increased prevalence of rheumatoid factor but not autoantibodies to anti-cyclic citrullinated peptide.

The association between Down syndrome (DS), a genetic disorder resulting from trisomy of the 21st chromosome, and the autoantibodies of rheumatoid arthritis (RA) has been proposed but not unequivocally proven. The aim of this study was to determine whether adult patients with DS present higher levels of anti-cyclic citrullinated peptide (anti-CCP) antibodies and/or rheumatoid factor (RF) than the general population. Our results showed that none of the 68 patients with DS had anti-CCP antibodies, whereas among 204 age- and sex-matched controls these autoantibodies were present in one person. However, DS patients presented a higher number of RF positive cases than controls (11.7% to 3.2% respectively; Fisher's exact test, p = .027). The higher number of RF positive cases in the DS group without increase of anti-CCP antibodies may be indicative of immune disturbances in general rather than RA in these patients. Our study supports the view that RA does not occur with higher frequency in patients with DS than in the general population.

GADA and anti-ZnT8 complicate the outcome of phenotypic type 2 diabetes of adults.

BACKGROUND: A proportion of phenotypic type 2 diabetes (T2D) patients produce pancreatic autoantibodies and a majority of T2D patients develop serious life-disabling complications over time despite the implementation of adequate clinical interventions. This study determined whether the presence of pancreatic autoantibodies (GADA, IA-2A, anti-ZnT8, or ICA) was associated with serious complications or concomitant diseases of adult patients diagnosed with T2D (N = 305). MAIN RESULTS: In the study population, 22.3% (N = 68) of subjects were positive for at least 1 of the 4 of the markers associated with autoimmune diabetes (presence of pancreatic autoantibody - pAb), followed by GADA (14.1%, N = 43), ICA (8.9%, N = 27), anti-ZnT8 (5.6%, N = 17) and IA-2A (2.0%, N = 6). Logistic regression analysis adjusted for patient's age, gender and duration of T2D revealed that (i) pAb was associated with higher prevalence of adiposity (odds ratio of adjusted regression model (adOR) 2.51, P = 0.032); (ii) pAb, GADA and anti-ZnT8 were associated with autoimmune thyroid disease (adORs 3.07, P = 0.012; 6.29, P < 0.001 and 3.52, P = 0.052, respectively); (iii) pAb and GADA, in particular, were risk factors for neurological complications (adORs 2.10, P = 0.036; 2.76, P = 0.009, respectively) and polyneuropathy in particular (adORs 2.60, P = 0.012; 3.10, P = 0.007, respectively); and (iv) anti-ZnT8 was a risk factor for developing nephropathy (adOR 4.61, P = 0.022). In addition, adiposity was associated with 5.3-year earlier onset of disease (adjusted linear regression model, P = 0.006). CONCLUSIONS: These results suggest that GADA and anti-ZnT8 are associated with progression of serious T2D complications, including polyneuropathy and nephropathy. In addition, adiposity represents a significant risk for autoimmunity development in T2D patients.

Development of a luciferase-based system for the detection of ZnT8 autoantibodies.

Appearance of autoantibodies represents the first detectable sign of autoimmune destruction of beta cells in type 1 diabetes (T1D). In addition, autoantibody levels represent an important predictive marker regarding the development of an autoimmune process. Recently, the zinc transporter (ZnT8) protein was identified as an autoimmune target in T1D; therefore, there is a need for reliable and simple methods for detection of ZnT8 autoantibodies. This report describes an assay designed to detect anti-ZnT8 autoantibodies in the serum of patients with T1D. This was carried out by generating a ZnT8 C-terminal dimer fused to the N-terminus of the Gaussia princeps luciferase that was overexpressed in insect cells using the baculovirus expression system. Recombinant protein was semi-purified and used as the target antigen in the liquid-phase luciferase immunoprecipitation system assay (LIPS), and results were compared to data obtained using a commercial ELISA designed to detect ZnT8 autoantibodies in T1D patient sera, particularly among adults. LIPS was less effective in detecting antibodies in children probably due to the relatively high prevalence of IgM anti-ZnT8 antibodies in children with T1D.

Antibodies to neurofilaments.

Immune responses to neuronal proteins are a frequent occurrence in neurodegenerative diseases. This study determines the occurrence of autoantibodies to the three neurofilament subunits in phosphorylated and dephosphorylated forms and relates these measures to age, human leukocyte antigen (HLA), and severity of disease in Down syndrome (DS). IgG-type antibodies to three neurofilament (NF) subunits, NF-L, NF-M, and NF-H, in both phosphorylated and dephosphorylated forms were tested by immunoblot in 128 patients with DS and compared to antibody levels in 94 normal controls. DS was revealed by karyotype analysis. Antibodies to dephospho-NF-M, NF-M, and NF-L were more common in DS samples than in controls. Total pools of DS and control samples had similar frequency of antibodies to NF-H, but there was a higher prevalence of antibodies against NF-H in DS patients with moderate or mild disability (43.0%) compared with those having serious disability (14.3%). No NF-H antibody was seen among young children (age 14 years or younger) of the latter group. The HLA-DR15 allele was negatively correlated with antibodies against NF-H. The high prevalence of antibodies to neurofilament proteins and the differences between DS and control samples may reflect the cross-talk between neural and immune systems that could have an important role in defending neural structures from neurodegenerative processes. In children with DS the presence of antibodies to NF-H might reflect a more favorable prognosis.

Testis-expressed protein TSGA10 an auto-antigen in autoimmune polyendocrine syndrome type I.

Autoimmune polyendocrine syndrome type 1 (APS1) is a rare monogenic autosomal recessive disorder. Autoimmune gonadal failure is often one of its features. The aim of this study was to identify targets of immune reactions associated with male autoimmune hypogonadism in APS1. Human testis cDNA expression library immunoscreening with APS1 patients' sera identified the protein testis-specific protein 10 (TSGA10), which is a testis-expressed protein with a key role in spermatogenesis. The corresponding serum autoantibodies were detected by Radioimmunoprecipitation assay in 3 of 40 male (7.5%) and 2 of 26 female (7.7%) APS1 patients but in none of either 32 patients with Addison's disease or 116 healthy controls (p = 0.0055). However, the TSGA10 antibodies in APS1 patients showed no correlation with testicular or ovarian failure or with autoimmune hypogonadism markers. Nevertheless, their presence in a proportion of patients with APS1 highlights the role of TSGA10 as a target of immune reactions in APS1.

Screening for celiac disease in Down's syndrome patients revealed cases of subtotal villous atrophy without typical for celiac disease HLA-DQ and tissue transglutaminase antibodies.

AIM: To investigate the prevalence of celiac disease (CD) as well as CD marker antibodies and susceptibility HLA-DQ haplotypes in 134 karyotyped Down's syndrome (DS) patients. METHODS: Immunoglobulin A (IgA) and G (IgG) type anti-gliadin antibodies (AGA), IgA type anti-tissue transglutaminase (tTG) antibodies (anti-tTG) with antigen of guinea pig and human source were determined by enzyme-linked immunosorbent assay and endomysium antibodies (EMA) by indirect immunofluorescence test. HLA-DQA1*0501/DQB1*0201 (DQ2) was revealed by polymerase chain reaction. Celiac disease was diagnosed by revised ESPGHAN criteria. RESULTS: 41% of DS patients had AGA, 6.0% IgA anti-tTG with guinea pig antigen, and 3.0% IgA EMA (all positive for anti-tTG with human tTG). Subtotal villous atrophy was found in 5 out of 9 DS patients who had agreed to small bowel biopsy. One of them had DQA1*0501/DQB1*0201 and anti-tTG and EMA i.e. typical for CD markers (this case also fulfilled the ESPGHAN diagnostic criteria),but other four lacked these markers. Three non-biopsied DS patients had also most probably CD because DQA1*0501/DQB1*0201 and IgA anti-tTG (EMA) were detected. Thus, the prevalence of CD among our DS patients population is 3.0% (95 % of confidence interval [CI]: 0.1-5.9%). CONCLUSION: We confirm the increased frequency of CD among DS patients. In addition, we have revealed a subgroup of patients with subtotal villous atrophy but without characteristic for CD immunological and genetic markers. Whether these cases represent CD (with atypical immunopathogenesis) or some other immune enteropathy, requires further investigations.