O. Abida

Tunisian endemic pemphigus foliaceus is associated with the HLA-DR3 gene: anti-desmoglein 1 antibody-positive healthy subjects bear protective alleles.

Background  Pemphigus foliaceus is an autoimmune blistering skin disease that partly results from genetic factors, especially human leucocyte antigen (HLA) class II genes.

Anti‐desmoglein 1 antibodies in healthy related and unrelated subjects and patients with pemphigus foliaceus in endemic and non‐endemic areas from Tunisia

Background  Pemphigus foliaceus is an autoimmune blistering skin disease characterized by the production of pathogenic IgG autoantibodies directed against desmoglein 1.

Contribution of PTPN22, CD28, CTLA-4 and ZAP-70 variants to the risk of type 1 diabetes in Tunisians.

Type 1 diabetes (T1D) is caused by an immune-mediated destruction of the insulin-producing β-cells. Several studies support the involvement of T cell activation molecules. In order to underline the role of the genes involved in this pathway, we investigated, using the Sequenom MassARRAY platform, polymorphisms of sixteen single-nucleotide polymorphisms (SNPs) belonging to PTPN22, CD28, CTLA-4, and ZAP-70 genes in 76 T1D patients and 162 unrelated healthy controls from Southern Tunisia. We confirmed the association with PTPN22 (rs2476601, Corrected P (Pcorr)=0.002, OR=6.20) and CD28 gene (rs1879877, Pcorr=0.003; OR=4.27 and rs3181096, Pcorr=0.02; OR=1.73). We also identified an association with rs17695937 of ZAP-70 gene (Pcorr=0.02, OR=1.87). Our results suggest a significant effect on T1D susceptibility for A-C-A-G-C and T-C-C-T-A-C haplotypes, of ZAP-70 and CD28 genes, respectively. In addition, (A-G-C) combination of ZAP-70/CD28 gene was significantly increased in T1D patients as compared to controls, suggesting the possible interaction between these genes. These results confirm the involvement of PTPN22 and CD28 genes in the genetic susceptibility to T1D. Interestingly, ZAP-70 seems to contribute to the susceptibility to the disease in our population. However, this finding has to be confirmed in further studies.

Polymorphisms in the IL2RA and IL2RB Genes in Inflammatory Bowel Disease Risk

Associations with different autoimmune diseases of polymorphisms in genes encoding the IL2RA and IL2RB subunits (located in 10p15 and 22q13, respectively), were identified through genome-wide studies. Polymorphisms in these two genes were studied in 107 inflammatory bowel disease (IBD) patients (39 Crohns disease [CD] and 68 ulcerative colitis [UC]) and in 162 ethnically healthy controls from Tunisia (Sfax). Two of the 15 IL2RA single-nucleotide polymorphisms (SNPs) genotyped (rs4749924 and rs706778) were significantly associated with UC (pcorr=0.018 and 0.048, respectively), but no evidence of association with CD was observed. The IL2RA GTCT haplotype was also more frequent in UC patients compared to controls (2.6% vs. 0%; p=0.002). One of the 6 IL2RB SNPs genotyped (rs743776) was significantly associated with CD (pcorr= 0.039), but no evidence of association with UC was observed. No significant association between IL2RB haplotypes was observed among investigated groups. Our study identified markers in the IL2RA and IL2RB genes that are significantly associated with UC and CD, respectively. Our results supporting IL2RA and IL2RB as promising candidate genes for IBD and suggesting a potential role of IL2R in the pathogenesis of IBD, likely involves regulatory T cells.

The CREM gene is involved in genetic predisposition to inflammatory bowel disease in the Tunisian population

The identification of susceptibility genes for inflammatory bowel disease (IBD) is key to understanding pathogenic mechanisms. Recently, the results of genetic association studies have highlighted many loci that are shared among several autoimmune diseases. We aimed to study the genetic epidemiology of polymorphisms in specific genes previously associated with other autoimmune diseases, namely the CREM, STAT4, STAT5a, Stat5b, and IRF5 genes. Twelve polymorphisms in the CREM, STAT4, STAT5a, Stat5b, and IRF5 genes were genotyped in a cohort of 107 IBD patients (39 Crohns disease [CD] and 68 ulcerative colitis [UC]) and 162 controls from southern Tunisia. One CREM single nucleotide polymorphism (SNP) displayed evidence for genetic association with IBD (p=8.7×10(-4), odds ratio [OR]=2.84 [1.58; 5.09]). One STAT4 SNP (p=0.026; OR=1.65 [1.06; 2.58]) exhibited a marginal association with UC but not with CD. No significant association was observed with the SNPs in STAT5a, IRF5, and STAT5b. These results suggest that common variants of the CREM gene are involved in the genetic component conferring general susceptibility to IBD, whereas STAT4 appears to be more specifically associated with UC. This work provides motivation for studies aiming to replicate these findings in larger populations.

Anti-desmoglein-1 antibodies are prevalent in Tunisian patients with hydatidosis and leishmaniasis.

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Polymorphisms of HLA microsatellite marker in Tunisian pemphigus foliaceus.

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease that partly results from genetic factors, especially from human leucocyte antigen (HLA) class II genes. Several data have reported the involvement of microsatellite (STR) markers across different regions of the HLA in many auto-immune diseases. To test the hypothesis of the existence of a major HLA haplotype predisposing to PF, we analyzed six polymorphisms of microsatellite loci at 6p21.3-21.4 spanning HLA: D6S291, D6S273, TNFa, MICA, D6S265 and D6S276 in 81 PF patients compared to 123 healthy individuals recruited from the south of Tunisia. In this study, after Bonferronis correction, 3 STR alleles from the TNFa locus were associated with the disease: the allele TNFa(∗)2 (p(c) = 4.2×10(-6)) and, at a lower level, the TNFa(∗)5 (p(c) = 0.014) as susceptibility alleles and TNFa(∗)6 (p(c) = 0.014) as protective ones. Furthermore, the expression of the TNFa(∗)2/TNFa(∗)5 genotype seem to confer susceptibility to PF (p = 0.00001, OR = 11.25). Interestingly, no significant LD was found between TNFa2/TNFa5 alleles and DRB1(∗)03/DRB1(∗)04 alleles. However, the multivariant regression analysis indicates that both the HLA class II and the TNFa alleles remained significant (p < 0.001). Although, these findings rejected our hypothesis on the existence of HLA susceptibility haplotype, they assessed the role of TNFa loci. Accordingly, TNFa seem to contribute to the aethiopathogenesis of Tunisian endemic PF may be by the induction of a high TNFα production which is known to enhance the autoimmune cascade of the disease.

Non-HLA autoimmunity genetic factors contributing to Autoimmune Polyglandular Syndrome type II in Tunisian patients

Autoimmune Polyglandular Syndrome Type II (APSII) is characterized by the co-occurrence of clinical insufficiency of at least two endocrine glands. Although, HLA determinants of APSII predisposition have been identified, little attention has been paid to non-HLA genes. Here, we used SNP genotyping in a Sequenom platform and genetic association tests to study a cohort of 60 APSII Tunisian patients presenting highly frequent co-occurrence of Autoimmune Thyroid Disease (AITD) and Type 1 Diabetes (T1D) and lower frequency of Addisons disease (AD). We tested the high a priori possibility that well-established non-HLA autoimmunity loci were involved in APSII and confirmed five association signals to APSII, namely: (1) two T1D-associated SNPs, in CTLA4 and IL2RA, suggest their involvement in T1D pathogenesis in this cohort; (2) two SNPs in STAT4 and IL15 not previously associated to endocrinopathies, are possibly involved in co-occurrence of organ autoimmunity in APSII, and; (3) one SNP in TNF alpha showed association to APSII irrespective of AD. While this work was performed in a relatively small cohort, these results support the notion that the non-HLA genetic component of APSII include genetic factors specific of particular autoimmune manifestations as well as genetic factors that promote the co-occurrence of multiple autoimmune endocrinopathies.

Catalase and Lipid Peroxidation Values in Serum of Tunisian Patients with Pemphigus Vulgaris and Foliaceus

Pemphigus is an autoimmune disorder resulting from the interaction between autoantibodies and desmoglein. Oxidative stress seems to be responsible for the onset/aggravation of many human diseases. Actually, it is considered as one of the several factors for the etiopathogenesis of pemphigus. The present study aims to evaluate the oxidative state in the sera of pemphigus vulgaris and pemphigus foliaceus patients by assessing lipid peroxidation, proteins oxidation, and antioxidant enzyme activity. This study included 36 pemphigus vulgaris and 42 pemphigus foliaceus patients as well as a group of controls consisting of 78 healthy volunteers. Malondialdehyde levels (p < 0.001) and catalase activity (p < 0.001) are higher in both groups of patients than in the control group. The two groups of patients showed a nonsignificant decrease in the thiol groups compared with the healthy one. A nonsignificant difference was shown between pemphigus vulgaris and pemphigus foliaceus patients, except for the catalase which shows an increase in the pemphigus vulgaris group. We have also found significant correlations between serum oxidative stress marker levels and serum anti-desmoglein antibody levels in the two pemphigus groups. These findings underline the implication of oxidative stress in the physiopathology of pemphigus by the increase in the autoantibodies’ reactivity.

The familial feature of Tunisian endemic pemphigus foliaceus

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