Olli Simell

Feasibility of genetic and immunological prediction of Type I diabetes in a population-based birth cohort

Aims/hypothesis. Population-wide genetic screening of susceptibility to multifactorial diseases will become relevant as knowledge of the pathogenesis of these diseases increases and preventive interventions are identified. Methods. Feasibility and acceptance of neonatal genetic screening for Type I (insulin-dependent) diabetes mellitus susceptibility and adherence of the at-risk children to frequent autoantibody follow-up were studied. Screening was offered to all families. The infants with HLA-DQB1 genotypes *02/*0302 and *0302/x (x¿*02, *0301, *0602) were invited to autoantibody follow-up. The children who developed signs of β-cell autoimmunity were invited to a separate prevention trial. Results. The parents of 31 526 babies born between November 1994 and April 1999 (94.4 % of those eligible) agreed to genetic screening. We found that 4651 infants (14.8 %) had increased genetic risk (2.5 to 15 times that of the general population) for Type I (insulin-dependent) diabetes mellitus, and 80 % of them joined the autoantibody surveillance. At the age of 1, 2, 3 and 4 years, 74, 69, 68 and 76 % of the at-risk children, respectively, attended the follow-up. A total of 17 of the 22 children (77 %) who were born during the study period and have developed diabetes carry the risk genotypes we currently use for screening. Conclusions/interpretation. Population-based screening of genetic susceptibility for Type I diabetes, linked with a possibility to participate later in a prevention trial, is highly accepted in Finland and identifies about 75 % of those developing diabetes at an early age. Families adhere well to the frequent measurement of signs of β-cell autoimmunity in the children at-risk. [Diabetologia (2001) 44: 290–297]

Temporal changes in the frequencies of HLA genotypes in patients with Type 1 diabetes—indication of an increased environmental pressure?

Aims/hypothesisThe incidence of Type 1 diabetes has increased 2.5 times during the time period from 1966 to 2000 in Finland—a general trend seen in almost all developed countries that can only be explained by environmental factors. The aim of this study was to test the possible effect of a changing environment on distribution of genotypes associated with disease susceptibility.MethodsHLA DRB1-DQA1-DQB1 genes and two diabetes-associated polymorphisms at IDDM2 and IDDM12 were analyzed. The frequencies of genotypes were compared between cases diagnosed with childhood-onset Type 1 diabetes during the period of 1939–1965 (n=367) and those diagnosed between 1990 and 2001 (n=736). Chi-square statistics or the Fishers Exact test were used for the comparison of frequencies of analyzed haplotypes and genotypes in the two groups.ResultsThe frequencies of (DR3)-DQA1*05-DQB1*02 and (DR4)-DQB1*0302 risk haplotypes and the high risk (DR3)-DQA1*05-DQB1*02/DRB1*0401-DQB1*0302 genotype were higher while proportion of patients carrying protective haplotypes—(DR15)-DQB1*0602 and (DR1301)-DQB1*0603—or protective genotypes was lower in patients diagnosed before 1965 as compared to those who developed disease after 1990. No temporal variation was found in the frequencies of genotypes at IDDM2 and IDDM12.Conclusion/interpretationOur data suggest that the need for genetic susceptibility to develop Type 1 diabetes has decreased over time due to an increasing environmental pressure and this results in a higher disease progression rate especially in subjects with protective HLA genotypes.

Isolation of enterovirus strains from children with preclinical Type 1 diabetes.

Aims  To develop methods for isolation of enterovirus strains from subjects with preclinical Type 1 diabetes and evaluate if their presence in stools is associated with beta‐cell damage.

PCR inhibition in stool samples in relation to age of infants

BACKGROUND PCR is rapidly replacing traditional methods in diagnostic virus laboratories. PCR inhibitors, which are often present in clinical samples, may lead to false negative test results. OBJECTIVES The aim was to study the presence of PCR inhibitors in stool samples collected from 3- to 24-month old children. STUDY DESIGN Total RNA fraction extracted from stool samples was spiked with a standardized amount of Semliki Forest Virus RNA and amplified using specific PCR primers. The presence of PCR inhibitors was detected by a decrease in amplification rate compared to spiked water samples. Inhibition in different age groups and dietary origin of PCR inhibitors were analyzed by comparing the samples taken during exclusive and non-exclusive breastfeeding periods. The inactivation of PCR inhibitors was also assessed. RESULTS Complete inhibition was seen in 12% (13/108) and partial inhibition in 19% (21/108) of the samples. Inhibition was seen in none of the stool samples (0/31) taken from infants younger than 6 months compared to 17% of samples (13/77) taken from 6 to 24 months old infants (p<0.036). Breastfeeding was more common in younger age group. Addition of bovine serum albumin (BSA) into the reaction mixtures eliminated the effect of inhibitors leading to all samples being positive. CONCLUSIONS PCR inhibitors are frequent in stool samples. They may originate from dietary components and can lead to false negative PCR results. The addition of BSA to the cDNA and PCR reactions proved to be an easy and effective method for eliminating the inhibitory effect of these compounds.

The effect of HLA class II, insulin and CTLA4 gene regions on the development of humoral beta cell autoimmunity

Aims/hypothesisThe aim of this study was to explore the contribution of genetic factors to the emergence of beta-cell-specific humoral autoimmunity.Subjects and methodsWe analysed the effect of HLA class II, insulin (INS; −23 HphI variant) and cytotoxic T-lymphocyte-associated protein 4 (CTLA4 [+49 and CT60]) genes on the appearance of beta-cell-specific autoantibodies in a large population-based birth cohort recruited in Finland. Infants carrying increased risk HLA DQB1 genotypes were monitored for the appearance of autoantibodies (islet cell autoantibodies [ICA], insulin autoantibodies [IAA], glutamic acid decarboxylase autoantibodies [GADA] and islet antigen 2 antibodies [IA–2A]). Those who developed beta-cell-specific autoantibodies were studied (n=574, mean follow-up time: 4.9 years; range 0.5–9.3).ResultsIAA emerged at a higher rate in children with the −23 HphI AA INS genotype than in those carrying AT or TT variants (hazard ratio 2.1, 95% CI 1.4–2.9, p<0.001). This effect of the INS locus was present in both HLA DQB1 risk groups. The appearance of IAA showed a strong association also with the HLA DRB1*0401 allele (hazard ratio 13.1, 95% CI 1.8–93.4, p<0.001). The development of IA–2A was also somewhat accelerated by the DRB1*0401 variant (p=0.03). Isolated ICA positivity was independent of the HLA and INS genotypes. None of the humoral immune markers showed association with the CTLA4 gene.Conclusions/interpretationThe INS and the DRB1 loci appear to contribute to the pathogenesis of type 1 diabetes by initiating/modifying insulin-specific autoimmunity. The emergence of IAA represents a crucial step in the development of beta cell autoimmunity in young children, in whom the appearance of GADA and IA–2A is linked to IAA.

Humoral β-cell autoimmunity is rare in patients with the congenital rubella syndrome

The congenital rubella syndrome (CRS) is associated with increased risk for diabetes and thyroid disease. However, the mechanisms by which the rubella virus may cause these diseases are poorly characterized. Previous studies were carried out before modern immunological methods were available. The present study aimed at evaluating whether autoimmune mechanisms are involved in the pathogenesis by analysing antibodies to biochemically characterized autoantigens. The incidence of clinical diabetes, thyroid disease, coeliac disease and related antibodies (islet cell antibodies, ICA; insulin autoantibodies, IAA; antibodies to the tyrosine phosphatase related IA‐2 molecule, IA‐2 A and glutamic acid decarboxylase, GADA; thyroid peroxidase, TPO; tissue transglutaminase, TTGA; and gliadin, AGA) and HLA risk genotypes were analysed in 37 subjects affected by or exposed to rubella during fetal life (mean age 22·5 years). One patient had diabetes and four patients had clinical hypothyroidism at the time of the examination. ICA, IAA, GADA or IA‐2 A were not detected in any of the patients, while five patients tested positive for TPO antibodies. Coeliac disease or TTGA were not observed. Eight patients carried the HLA‐DR3–associated HLA‐DQB1*02‐DQA1*05 haplotype. These results provide no evidence of an increased frequency of markers for humoral β‐cell autoimmunity in patients with CRS suggesting that diabetes in CRS may be caused by other than autoimmune mechanisms.

Maternal food consumption during pregnancy and risk of advanced β-cell autoimmunity in the offspring

Virtanen SM, Uusitalo L, Kenward MG, Nevalainen J, Uusitalo U, Kronberg‐Kippilä C, Ovaskainen M‐L, Arkkola T, Niinistö S, Hakulinen T, Ahonen S, Simell O, Ilonen J, Veijola R, Knip M. Maternal food consumption during pregnancy and risk of advanced β‐cell autoimmunity in the offspring.

Human rhinoviruses in INDIS-study material-evidence for recovery of viable rhinovirus from fecal specimens

The significance of human rhinoviruses (HRV) as prevailing respiratory pathogens has sharpened during the recent years followed by implementation of molecular methods in detection. Rhinoviruses are detected exceedingly in hospitalized cases of respiratory infection with varying severity, in addition to being frequent in cases of common cold. The aim of this study was to evaluate occurrence of HRV in a prospective study material. The prospective INDIS material comprises nasopharyngeal (N = 429) and fecal (N = 425) specimens from children under 11 years of age collected during any clinical infection. Validated real‐time RT‐PCR assays were applied for the detection of HRV. HRV were detected numerously not only in the nasopharyngeal specimens, but a myriad also in fecal specimens, 236 (55.0%) and 149 (35.1%), respectively, fecal findings actually beyond anticipation. A total of 13 of HRV‐positive fecal specimens were selected for genetic typing in the VP4/VP2 coding region. HRV‐A strains were detected in seven specimens: HRV‐A9, ‐A10, ‐A24, ‐A49, ‐A56 and ‐A82. HRV‐B—strains were detected three times: HRV‐B42 and ‐B79, and HRV‐C twice: HRV‐C12 and HRV‐Cpat4. HRV‐B42 also showed cytopathic effect in cell culture, confirmed by real‐time RT‐PCR and VP4/VP2 sequencing, suggesting presence of viable HRV in fecal specimens. J. Med. Virol. 85:1466–1472, 2013.

Familial clustering of β-cell autoimmunity in initially non-diabetic children

Type 1 diabetes is characterised by familial aggregation. We set out to explore whether β‐cell autoimmunity, which is considered to precede clinical disease, also shows familial clustering.

Soluble adhesion molecules in young children with signs of β‐cell autoimmunity—prospective follow‐up from birth

This study aimed at evaluating the relationship between the circulating concentrations of soluble intercellular adhesion molecule‐1 (sICAM‐1) and sL‐selectin and the appearance of β‐cell autoimmunity, and at assessing whether these molecules could assist in the identification of environmental factors implicated in the immune process damaging the pancreatic β‐cells.