Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Diagnosis and treatment of sleep related breathing disorders in children: 2007 to 2011

Sleep related breathing disorders (SRBD) have historically been under-recognised and under-treated. Obstructive sleep apnoea (OSA) affects approximately 3% of children. In line with the increased recognition of SRBD there has been an increase in demand for diagnostic services. We determined the awareness of SRBD amongst Irish paediatricians, examined the provision of sleep services to children throughout the country between 2007 and 2011 and audited diagnostic sleep services in a tertiary centre in 2011. Amongst respondents there was an awareness of SRBD but a poor understanding of diagnostic evaluation with 31/46 (67) referring to inappropriate services. There has been a sharp increase in both diagnostic sleep tests (433-1793 [414]) and in the use of non-invasive ventilation (NIV) (31-186 [627]) for treatment of SRBD between 2007 and 2011. Paediatric sleep services are organized in an ad-hoc manner nationally with significant service variation. The use of domiciliary overnight oximetry reduced the requirement for more formal polysomnography by 70%.

Outpatient parenteral antimicrobial therapy: a report of three years experience

Although outpatient parenteral antimicrobial therapy (OPAT) is practiced internationally, there is a paucity of data regarding outcomes of paediatric OPAT. A retrospective analysis, of 3 years experience (January 2010 to 2013) was performed at a tertiary paediatric Respiratory unit. There were 362 OPAT courses administered to 32 children, of which 30 had cystic fibrosis and the remaining two had recurrent pneumonia. A total of 3,688 days of antibiotics were administered. The median age was 8.8 years (range 2.75 - 17.8 years). Sixteen (50%) were male. Each child received an average of 11 courses and median duration of OPAT was 10 days (range 2-21 days). Tobramycin was the commonest antimicrobial prescribed, with ceftazidime second. During this period, there was one readmission (0.3%) post discharge and 3 (2%) portocath infections. All patients attended for weekly review and laboratory monitoring. OPAT appears safe, effective and reduces the need for inpatient beds.

Pulmonary complications of congenital heart disease

Cardiac and pulmonary pathophysiologies are closely interdependent, which makes the management of patients with congenital heart disease (CHD) all the more complex. Pulmonary complications of CHD can be structural due to compression causing airway malacia or atelectasis of the lung. Surgical repair of CHD can also result in structural trauma to the respiratory system, e.g., chylothorax, subglottic stenosis, or diaphragmatic paralysis. Disruption of the Starling forces in the pulmonary vascular system in certain types of CHD lead to alveolar-capillary membrane damage and pulmonary oedema. This in turn results in poorly compliant lungs with a restrictive lung function pattern that can deteriorate to cause hypoxemia. The circulation post single ventricle palliative surgery (the so called "Fontan circulation") poses a unique spectrum of pulmonary pathophysiology with restrictive lung function and a low pulmonary blood flow state that predisposes to thromboembolic complications and plastic bronchitis. As the population of patients surviving post CHD repair increases, the incidence of pulmonary complications has also increased and presents a unique cohort in both the paediatric and adult clinics.

Congenital central hypoventilation syndrome in children

Congenital central hypoventilation syndrome (CCHS) is a rare, lifelong condition wherein control of breathing is abnormal and patients present with symptoms of alveolar hypoventilation. The severity of hypoventilation varies and although most patients present in the neonatal period, late onset cases have been reported. In 2003, it was discovered that mutations in the PHOX2B gene were responsible for CCHS. This gene also plays a role in neural crest cell migration, and many patients present with symptoms of autonomic dysfunction in addition to hypoventilation. The pathophysiology responsible for hypoventilation remains unclear although a unifying hypothesis is that the abnormality is located in areas of the brain involved in integration of chemoreceptor afferent pathways for ventilation. The goal of treatment for CCHS is to ensure adequate ventilation during wakefulness and sleep. A variety of ventilation modalities are available including positive pressure ventilation via tracheostomy, non-invasive ventilation via nasal mask, and diaphragmatic pacing. With close monitoring and support, children with CCHS can be expected to function well in society and have a good quality of life.

Co-morbidity in a cystic fibrosis population attending a regional clinic

Pulmonary disease remains the major cause of morbidity in patients with cystic fibrosis (CF). However, of 115 patients attending a regional CF clinic we noted 16 cases (14%) with co-morbid conditions. Of this group, 4 of 115 patients (3.5%) had renal problems including both structural and functional defects and 4 (3.5%) had neurological disorders, 3 of which were types of epilepsy. Notably, 3 of 115 patients (2.6%) had different forms of neoplasia, all of which required significant surgical and/or chemotherapeutic intervention. There is now increasing evidence of the association between digestive tract malignancy and CF, which further complicates management of these already complex cases.

Induction in transgenic mice of HLA-A2.1-restricted cytotoxic T cells specific for a peptide sequence from a mutated p21ras protein

Cytotoxic T cells (CTL) recognize short peptides that are derived from the proteolysis of endogenous cellular proteins and presented on the cell surface as a complex with MHC class I molecules. CTL can recognize single amino acid substitutions in proteins, including those involved in malignant transformation. The mutated sequence of an oncogene may be presented on the cell surface as a peptide, and thus represents a potential target antigen for tumour therapy. The p21ras gene is mutated in a wide variety of tumours and since the transforming mutations result in amino acid substitutions at positions 12, 13 and 61 of the protein, a limited number of ras peptides could potentially be used in the treatment of a wide variety of malignancies. A common substitution is Val for Gly at position 12 of p21ras. In this study, we show that the peptide sequence from position 5 to position 14 with Val at position 12-ras p5-14 (Val-12)-has a motif which allows it to bind to HLA-A2.1. HLA-A2.1-restricted ras p5-14 (Val-12)-specific CTL were induced in mice transgenic for both HLA-A2.1 and human beta2-microglobulin after in vivo priming with the peptide. The murine CTL could recognize the ras p5-14 (Val-12) peptide when they were presented on both murine and human target cells bearing HLA-A2.1. No cross-reactivity was observed with the native peptide ras p5-14 (Gly-12), and this peptide was not immunogenic in HLA-A2.1 transgenic mice. This represents an interesting model for the study of an HLA-restricted CD8 cytotoxic T cell response to a defined tumour antigen in vivo.

Combined effects of interleukin-3 and interleukin-11 on hematopoiesis in irradiated mice

The survival rate and recovery of peripheral blood cells and platelets were studied in Balb/c mice subjected to different single doses of whole-body irradiation and treated with a combination of interleukin-3 (IL-3) and interleukin-11 (IL-11). In a first group of 20 mice, 7.5 Gy irradiation, immediately followed by 2 and 5 days therapy of IL-3 and IL-11, respectively, increased the survival rate to 82% compared to 20% in untreated controls. In a second group of mice irradiated with 7 Gy, we observed significantly higher platelet, white blood cell (WBC), and red blood cell (RBC) counts after treatment with both cytokines, as compared to IL-3 or IL-11 alone or untreated controls. In addition, the survival rate of the mice with the combined therapy was also increased to 84%, compared to 48% in untreated controls. Irradiation (8.5 Gy) gave 100% mortality for the control mice, and therapy with combined IL-3 plus IL-11 had only a marginal effect. Interestingly, syngeneic bone marrow transplantation (BMT) alone, performed 16 hours after irradiation, increased the survival rate to 70%, while BMT combined with administration of IL-3 plus IL-11 increased it to 97%. Furthermore, BMT combined with cytokine administration could partially prevent the severe WBC and RBC depletion observed in mice treated with BMT alone and promoted a more rapid recovery of platelets and RBC. These data show that the combination of IL-3 and IL-11 has a radioprotective effect and can enhance recovery of platelets, WBC, and RBC in irradiated mice. Combined IL-3 plus IL-11 therapy may be clinically useful in myelodepression, especially in platelet depletion related to radiation therapy or chemotherapy, or after bone marrow transplantation.

Molybdate and regulation of mod (molybdate transport), fdhF, and hyc (formate hydrogenlyase) operons in Escherichia coli

Escherichia coli mutants with defined mutations in specific mod genes that affect molybdate transport were isolated and analyzed for the effects of particular mutations on the regulation of the mod operon as well as the fdhF and hyc operons which code for the components of the formate hydrogenlyase (FHL) complex. phi (hyc'-'lacZ+) mod double mutants produced beta-galactosidase activity only when they were cultured in medium supplemented with molybdate. This requirement was specific for molybdate and was independent of the moa, mob, and moe gene products needed for molybdopterin guanine dinucleotide (MGD) synthesis, as well as Mog protein. The concentration of molybdate required for FHL production by mod mutants was dependent on medium composition. In low-sulfur medium, the amount of molybdate needed by mod mutants for the production of half-maximal FHL activity was increased approximately 20 times by the addition of 40 mM of sulfate, mod mutants growing in low-sulfur medium transported molybdate through the sulfate transport system, as seen by the requirement of the cysA gene product for this transport. In wild-type E. coli, the mod operon is expressed at very low levels, and a mod+ merodiploid E. coli carrying a modA-lacZ fusion produced less than 20 units of beta-galactosidase activity. This level was increased by over 175 times by a mutation in the modA, modB, or modC gene. The addition of molybdate to the growth medium of a mod mutant lowered phi (modA'-'lacZ+) expression. Repression of the mod operon was sensitive to molybdate but was insensitive to mutations in the MGD synthetic pathway. These physiological and genetic experiments show that molybdate can be transported by one of the following three anion transport system in E. coli: the native system, the sulfate transport system (cysTWA gene products), and an undefined transporter. Upon entering the cytoplasm, molybdate branches out to mod regulation, fdhF and hyc activation, and metabolic conversion, leading to MGD synthesis and active molybdoenzyme synthesis.

Peptide-antibody conjugates for tumour therapy: a MHC-class-II-restricted tetanus toxin peptide coupled to an anti-Ig light chain antibody can induce cytotoxic lysis of a human B-cell lymphoma by specific CD4 T cells

Anti-idiotype antibody therapy of B-cell lymphomas, despite numerous promising experimental and clinical studies, has so far met with limited success. Tailor-made monoclonal anti-idiotype antibodies have been injected into a large series of lymphoma patients, with a few impressive complete tumour remissions but a large majority of negative responses. The results presented here suggest that, by coupling to antilymphoma idiotype antibodies a few molecules of the tetanus toxin universal epitope peptide P2 (830-843), one could markedly increase the efficiency of this therapy. We show that after 2-hr incubation with conjugates consisting of the tetanus toxin peptide P2 coupled by an S-S bridge to monoclonal antibodies directed to the lambda light chain of human immunoglobulin, human B-lymphoma cells can be specifically lysed by a CD4 T-lymphocyte clone specific for the P2 peptide. Antibody without peptide did not induce B-cell killing by the CD4 T-lymphocyte clone. The free cysteine-peptide was also able to induce lysis of the B-lymphoma target by the T-lymphocyte clone, but at a molar concentration 500 to 1000 times higher than that of the coupled peptide. Proliferation assays confirmed that the antibody-peptide conjugate was antigenically active at a much lower concentration than the free peptide. They also showed that antibody-peptide conjugates required an intact processing function of the B cell for peptide presentation, which could be selectively inhibited by leupeptin and chloroquine.(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction of antigenic peptides with the H-2Kd MHC class I molecule

An important event in the recognition of antigen by T cells is the selective interaction of peptides with major histocompatibility complex (MHC) molecules. We have defined several critical structural features that promote the efficient interaction of antigenic peptides with the MHC class I molecule, H-2Kd. For four unrelated antigens, we found that optimal synthetic peptides were short, only 9 or 10 amino acids long. These and other H-2Kd-restricted peptides were found to share a distinct 2-residue binding motif. Two regions in the H-2Kd antigen binding site that might accommodate the motif residues were identified by analysis of Ala-substituted H-2Kd molecules. A molecular model showing the possible interaction of one antigenic peptide with the H-2Kd molecule is presented.

Conversion of a self peptide sequence into a Kd-restricted neo-antigen by a Tyr substitution

We have previously found that a Tyr residue was critical for the interaction of peptides with the Kd molecule, and therefore may be acting as an anchor residue. In the present report we show that it is possible to convert a self peptide sequence into a Kd-restricted neo-antigen by a single Tyr substitution at position 2 of the peptide. This supports the idea that Tyr is a critical element in the binding motif of Kd-restricted peptides and is a finding that could also prove useful for vaccine development.

Delineation of determinants on HLA-B7 and HLA-B27 that are necessary for cytolytic T cell recognition by using inter- and intra-domain recombinants

We have used bulk culture HLA-B7 and HLA-B27 specific CTL lines derived from 11 donors, and a series of rHLA-B7/HLA-B27 genes transfected into and expressed on the surface of the murine cell P815, to determine the amino acid residues on these HLA class I molecules that are critical for allospecific CTL recognition. The results obtained indicate that for four of six HLA-B7-specific CTL lines the alpha-1 domain for CTL recognition. Furthermore, we found that residues 77 and/or 80 had a critical effect on recognition for all of the CTL lines tested. The region 97-156 in the alpha-2 domain was also important for some of these CTL lines. Furthermore, by using five bulk culture HLA-B27-specific CTL lines we were able to show that residues 77 and/or 80 and residue 152 are also essential for recognition of HLA-B27 by HLA-B27-specific CTL. The strong influence exerted by these residues is discussed in terms of the three-dimensional structure of class I molecules. Finally, a selection was regularly observed in the bulk cultures such that the CTL that were preferentially influenced by either the alpha-1 or the alpha-2 domain were lost after 4 to 7 wk of culture resulting in CTL cell lines which were extremely sensitive to sequence modifications of HLA-B7 or HLA-B27. The possible reasons for this selection, which we have previously observed with both anti-HLA-A2 and anti-HLA-A3 cell lines and is therefore not unique to HLA-B7 or HLA-B27, are discussed.

Delineation of determinants on HLA-B7 and HLA-B27 that are necessary for cytolytic T cell recognition by using inter- and intra-domain recombinants

We have used bulk culture HLA-B7 and HLA-B27 specific CTL lines derived from 11 donors, and a series of rHLA-B7/HLA-B27 genes transfected into and expressed on the surface of the murine cell P815, to determine the amino acid residues on these HLA class I molecules that are critical for allospecific CTL recognition. The results obtained indicate that for four of six HLA-B7-specific CTL lines the alpha-1 domain for CTL recognition. Furthermore, we found that residues 77 and/or 80 had a critical effect on recognition for all of the CTL lines tested. The region 97-156 in the alpha-2 domain was also important for some of these CTL lines. Furthermore, by using five bulk culture HLA-B27-specific CTL lines we were able to show that residues 77 and/or 80 and residue 152 are also essential for recognition of HLA-B27 by HLA-B27-specific CTL. The strong influence exerted by these residues is discussed in terms of the three-dimensional structure of class I molecules. Finally, a selection was regularly observed in the bulk cultures such that the CTL that were preferentially influenced by either the alpha-1 or the alpha-2 domain were lost after 4 to 7 wk of culture resulting in CTL cell lines which were extremely sensitive to sequence modifications of HLA-B7 or HLA-B27. The possible reasons for this selection, which we have previously observed with both anti-HLA-A2 and anti-HLA-A3 cell lines and is therefore not unique to HLA-B7 or HLA-B27, are discussed.

A study of functionally active amino acids involved in the interaction of HLA-A2 or HLA-A3 molecules with cytolytic T lymphocytes

A large series of HLA-A2/HLA-A3 recombinant genes were generated by using the in vivo recombination technique. These genes have each been modified in the last two-thirds of the third exon such that one or several HLA-A2-specific substitutions have been made in the HLA-A3 gene and vice versa. The recombinant genes were transfected into the murine cell line P815 and the transfectants were used as targets for a series of 20 human CTL lines or clones specific for HLA-A2 or HLA-A3, or restricted by HLA-A2 and specific for influenza A. Several patterns of anti-HLA-A2, anti-HLA-A3, and HLA-A2-restricted anti-influenza CTL activity were observed and when uncloned cell lines were studied, a progressive selection of some clones with a similar pattern of activity was regularly found. From the comparison of these different patterns the following conclusions can be drawn: 1) In most but not all cases both domains of the class I molecule were essential for CTL recognition, but residue 152 was critically important for the majority of CTL tested; 2) amino acids 114/116 were also critical in most cases, and their position close to amino acid 152 in the tertiary structure of the molecule may have some functional significance; and 3) amino acid 161, although highly conserved, plays an unexpected but very important role in CTL function.

A study of functionally active amino acids involved in the interaction of HLA-A2 or HLA-A3 molecules with cytolytic T lymphocytes

A large series of HLA-A2/HLA-A3 recombinant genes were generated by using the in vivo recombination technique. These genes have each been modified in the last two-thirds of the third exon such that one or several HLA-A2-specific substitutions have been made in the HLA-A3 gene and vice versa. The recombinant genes were transfected into the murine cell line P815 and the transfectants were used as targets for a series of 20 human CTL lines or clones specific for HLA-A2 or HLA-A3, or restricted by HLA-A2 and specific for influenza A. Several patterns of anti-HLA-A2, anti-HLA-A3, and HLA-A2-restricted anti-influenza CTL activity were observed and when uncloned cell lines were studied, a progressive selection of some clones with a similar pattern of activity was regularly found. From the comparison of these different patterns the following conclusions can be drawn: 1) In most but not all cases both domains of the class I molecule were essential for CTL recognition, but residue 152 was critically important for the majority of CTL tested; 2) amino acids 114/116 were also critical in most cases, and their position close to amino acid 152 in the tertiary structure of the molecule may have some functional significance; and 3) amino acid 161, although highly conserved, plays an unexpected but very important role in CTL function.

Recognition of hybrid HLA molecules expressed on murine P815 cells using human alloreactive cytotoxic T lymphocytes

The HLA-A2 and -A3 genes were used to construct intra-exon hybrids in which part of the third exon (corresponding to the second domain) was of one type and the rest of the other. Murine P815 cells expressing these hybrid constructs were assayed with human alloreactive cytotoxic T-lymphocyte lines specific for either HLA-A2 or HLA-A3. Specific recognition patterns were obtained which indicate that, in some cases, a small portion of the HLA-A2 sequence in an HLA-A3 background is sufficient for recognition by HLA-A2-specific cytotoxic T cells.

An assessment of natural cell-mediated cytotoxicity in patients with malignant lymphoma

Fifty per cent of untreated malignant lymphoma patients were shown to have profoundly reduced levels of peripheral blood lymphocyte-natural cell mediated cytotoxicity (PBL-NCMC) when tested against the leukaemic cell-line K562; assessment of NCMC in unfractionated blood from a large number of these patients showed a comparable reduction in activity. High levels of NCMC were observed in some patients with stage III/IV non-Hodgkin's lymphoma (NHL), while Hodgkin's disease (HD) patients over 40 yr of age had normal levels. In both NHL and HD patients there was no correlation between NCMC and absolute lymphocyte count or lymphoma histology. Human interferon was seen to boost NCMC in the majority of NHL patients, but most HD patients were nonresponders. Almost all patients tested had normal number of target binding lymphocytes, and most had numbers of HNK-1+ cells within the control range. However, on exposure to IFN, the number of target binding lymphocytes increased in over half of the patients tested, with some patients showing an increase in HNK-1+ cells, in the majority of cases without enhancement of NCMC.

Physiologic correlates of airway collapse in chronic airflow obstruction

Forty percent of 89 patients with chronic airflow obstruction (CAO) demonstrated maximum expiration flow-volume (MEFV) patterns consistent with sudden collapse or marked narrowing of large central airways. In contrast, 43 percent of the CAO patients demonstrated a curvilinear (C) pattern; the remainder (17 percent) were intermediate. Volume displacement plethysmography indicated that the airway collapse (AC) pattern was influenced by, but was not solely, a gas compression artifact. Airway collapse patients had more obstruction and hyperinflation than C patients and also had decreased diffusing capacity, absence of density dependence, reduced lung recoil, and no effort dependence of airflow. Bronchodilator administration in AC patients typically produced large reduction of residual volume and increase of vital capacity, with a smaller increase of airflow. These data suggest that AC patients have significant, partially reversible peripheral airways obstruction plus emphysema. Possible determinants of AC include reduced central airway support, increased peripheral resistance, loss of lung recoil, and increased pleural pressures during forced expiration. The MEFV contour appears to evolve from normal to curvilinear to the AC pattern as the severity of airflow obstruction worsens.