Simona Piccinini

Association between PTPN22 C1858T and type 1 diabetes: a replication in continental Italy

The missense PTPN22 C1858T polymorphism recently emerged as an important population-independent risk factor for type 1 diabetes (T1D) and other autoimmune diseases. The PTPN22 gene encodes the lymphoid tyrosine phosphatase (LYP), a negative regulator of signal transduction through the T-cell receptor. Although the frequency of the polymorphism is variable among different ethnic groups, the association between PTPN22 *T1858 and T1D has been replicated in several populations. Here, we contribute the first replication of the association between PTPN22 and T1D in populations from continental Italy, carried out in two independent samples of T1D patients (N = 216 and 82) and controls (N = 271 and 89). Our data also suggest that T1D carriers of the *T1858 allele could be at increased risk for other comorbid autoimmune disorders.

Altered phenotype and function of dendritic cells in children with type 1 diabetes

The importance of dendritic cells (DC) in the activation of T cells and in the maintenance of self‐tolerance is well known. We investigated whether alterations in phenotype and function of DC may contribute to the pathogenesis of Type 1 diabetes (T1DM). Mature DC (mDC) from 18 children with T1DM and 10 age‐matched healthy children were tested. mDC, derived from peripheral blood monocytes cultured for 6 days in presence of interleukin (IL)‐4 and granulocyte‐macrophage colony stimulating factor (GM‐CSF) and stimulated with lipopolysaccharide (LPS) for the last 24 h, were phenotyped for the expression of the co‐stimulatory molecules B7·1 and B7·2. In six patients and six controls allogenic mixed leucocyte reaction (AMLR) was performed using mDC and cord blood‐derived naive T cells at a DC/T naive ratio of 1 : 200. Proliferation was assessed on day 7 by [3H]‐thymidine incorporation assay. Mature DC derived from patients showed, compared with controls, a reduced expression of B7·1 [mean of fluorescence intensity (MFI): 36·2 ± 14·3 versus 72·9 ± 34·5; P = 0·004] and B7·2 (MFI: 122·7 ± 67·5 versus 259·6 ± 154·1; P = 0·02). We did not find differences in the HLA‐DR expression (P = 0·07). Moreover, proliferative response of allogenic naive T cells cultured with mDC was impaired in the patients (13471 ± 9917·2 versus 40976 ± 24527·2 cpm, P = 0·04). We also measured IL‐10 and IL‐12 concentration in the supernatant of DC cultures. Interestingly, we observed in the patients a sevenfold higher level of IL‐10 (P = 0·07) and a ninefold lower level of IL‐12 (P = 0·01). Our data show a defect in the expression of the co‐stimulatory molecules and an impairment of DC priming function, events that might contribute to T1DM pathogenesis.

Recognition of zinc transporter 8 and MAP3865c homologous epitopes by new-onset type 1 diabetes children from continental Italy

Abstract There are several pieces of evidence indicating that Mycobacterium avium subspecies paratuberculosis (MAP) infection is linked to type 1 diabetes (T1D) in Sardinian patients. An association between MAP and T1D was recently observed in an Italian cohort of pediatric T1D individuals, characterized by a different genetic background. It is interesting to confirm the prevalence of anti-MAP antibodies (Abs) in another pediatric population from continental Italy, looking at several markers of MAP presence. New-onset T1D children, compared to age-matched healthy controls (HCs), were tested by indirect enzyme-linked immunosorbent assay for the presence of Abs toward the immunodominant MAP3865c/ZnT8 homologues epitopes, the recently identified C-terminal MAP3865c281–287 epitope and MAP-specific protein MptD. Abs against MAP and ZnT8 epitopes were more prevalent in the sera of new-onset T1D children compared to HCs. These findings support the view that MAP3865c/ZnT8 cross-reactivity is involved in the pathogenesis of T1D, and addition of Abs against these peptides to the panel of existing T1D biomarkers should be considered. It is important now to investigate the timing of MAP infection during prospective follow-up in at-risk children to elucidate whether Ab-titers against these MAP/ZnT8 epitopes are present before T1D onset and if so if they wane after diagnosis.

Mycobacterium avium subsp. paratuberculosis in an Italian Cohort of Type 1 Diabetes Pediatric Patients

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiological agent of Johnes disease in ruminants. Recent studies have linked MAP to type 1 diabetes (T1D) in the Sardinian population. The aim of this study was to investigate the prevalence of MAP infection in a T1D cohort from continental Italy compared with healthy control subjects. 247 T1D subjects and 110 healthy controls were tested for the presence of MAP. MAP DNA was detected using IS900-specific polymerase chain reaction (PCR). The presence of antibodies towards a MAP antigen, heparin binding hemoagglutinin (HBHA), was detected by ELISA. We demonstrated a higher MAP DNA prevalence in plasma samples from T1D patients and a stronger immune response towards MAP HBHA, compared with healthy control subjects. Moreover, in the recent onset patients, we observed an association between anti-MAP antibodies and HLA DQ2 (DQA1 0201/DQB1 0202). These findings taken together support the hypothesis of MAP as an environmental risk factor for the development of T1D in genetically predisposed subjects, probably involving a mechanism of molecular mimicry between MAP antigens and pancreatic islet β-cells.

Genotypes of p53 codon 72 correlate with age at onset of type 1 diabetes in a sex-specific manner.

Abstract In type 1 diabetes mellitus (T1D) p53 pathways are up-regulated and there is an increased susceptibility to apoptosis. The hypothesis is that p53 codon 72 polymorphism could be associated with T1D. A total of 286 children with T1D and a control sample of 730 subjects were studied. p53 codon 72 polymorphism was analysed by polymerase chain reaction. A large increase of p53 *Arg/*Arg was observed in T1D patients with age at onset <6 years. A strong linear correlation between *Arg/*Arg genotype and age at onset was observed in females. The involvement of the *Arg/*Arg genotype in apoptosis suggests that during the autoimmune process leading to T1D, genetic factors that favor apoptosis may contribute to the onset of overt disease.

Type 1 Diabetes at-risk children highly recognize Mycobacterium avium subspecies paratuberculosis epitopes homologous to human Znt8 and Proinsulin

Mycobacterium avium subspecies paratuberculosis (MAP) has been previously associated to T1D as a putative environmental agent triggering or accelerating the disease in Sardinian and Italian populations. Our aim was to investigate the role of MAP in T1D development by evaluating levels of antibodies directed against MAP epitopes and their human homologs corresponding to ZnT8 and proinsulin (PI) in 54 T1D at-risk children from mainland Italy and 42 healthy controls (HCs). A higher prevalence was detected for MAP/ZnT8 pairs (62,96% T1D vs. 7,14% HCs; p < 0.0001) compared to MAP/PI epitopes (22,22% T1D vs. 9,52% HCs) and decreasing trends were observed upon time-point analyses for most peptides. Similarly, classical ZnT8 Abs and GADA decreased in a time-dependent manner, whereas IAA titers increased by 12%. Responses in 0–9 year-old children were stronger than in 10–18 age group (75% vs. 69,1%; p < 0.04). Younger age, female sex and concomitant autoimmune disorders contributed to a stronger seroreactivity suggesting a possible implication of MAP in multiple autoimmune syndrome. Cross-reactivity of the homologous epitopes was reflected by a high correlation coefficient (r2 > 0.8) and a pairwise overlap of positivity (>83% for MAP/ZnT8).

Seroreactivity against Specific L5P Antigen from Mycobacterium avium subsp. paratuberculosis in Children at Risk for T1D

Aims/Hypothesis Although numerous environmental agents have been investigated over the years as possible triggers of type 1 diabetes (T1D), its causes remain unclear. We have already demonstrated an increased prevalence of antibodies against peptides derived from Mycobacterium avuim subsp. paratuberculosis (MAP) homologous to human zinc transporter 8 protein (ZnT8) and proinsulin in Italian subjects at risk for or affected by T1D. In this study, we compared titers of the previously detected antibodies with seroreactivity to MAP lipopentapetide (L5P) that recently emerged as a strong immunogenic component able to specifically distinguish MAP from other mycobacteria. Methods Plasma of 32 children and youth at risk for T1D including follow-up samples and 42 age-matched healthy controls (HC) recruited at the Tor Vergata University Hospital in Rome was analyzed by indirect ELISA for the presence of antibodies against MAP-derived epitopes MAP3865c133–141, MAP3865c125-133, MAP2404c70-85 and MAP1,4αgbp157-173 along with their ZnT8 and proinsulin homologs. The data were analyzed through two-tailed Mann-Whitney U test and relation between variables was determined by principal component analysis. Results Responses to L5P were not detectable in subjects whose initial seroreactivity to MAP peptides and their human homologs was lost in follow-up samples, whereas anti-L5P antibodies appeared constantly in individuals with a stable immunity against MAP antigens. The overall coincidence in positivity to L5P and the four MAP epitopes both in children at risk for T1D and HC exceeded 90%. Conclusions MAP-derived homologs may cross-react with ZnT8 and proinsulin peptides inducing immune responses at a young age in subjects predisposed for T1D. Thus, L5P may have a diagnostic value to immediately indicate the presence of anti-MAP seroreactivity when evaluation of a more complex antibody status is not required. Almost complete coincidence in responses to both types of antigens lends support to the involvement of MAP in T1D.

A variable degree of autoimmunity in the pedigree of a patient with type 1 diabetes homozygous for the PTPN22 1858T variant

We investigated whether the PTPN22 C1858T polymorphism is associated with the autoimmune conditions present in the family of a child affected by type 1 diabetes (T1D) carrying the TT genotype (index patient) and the potential immunological effect of the variant. We found that nine family members carried the CT genotype and five suffered from autoimmunity. Interestingly, anti‐ZnT8 antibodies were detected in T1D patients and in three healthy relatives. In the TT patient, we showed diminished T‐cell proliferation and reduced interleukin‐2 (IL‐2) and interferon‐gamma (IFN‐γ) production. A marked reduction of IL‐2 was also observed for all CT relatives with autoimmunity and a lack of IFN‐γ production was observed for the younger brother of the index patient, heterozygous for the polymorphism. In this family, the C1858T variant might confer a high risk of autoimmunity. Moreover, our data confirm that impaired IL‐2 production upon T‐cell receptor stimulation is associated with autoimmunity in the carriers of the polymorphism. This study might prompt to extend the panel of risk markers in relatives of subjects affected by T1D.