Modulation of type 1 diabetes susceptibility by tumor necrosis factor alpha -308 G/A and lymphotoxin alpha +249 A/G haplotypes and lack of linkage disequilibrium with predisposing DQB1-DRB1 haplotypes in Bahraini patients

Tumor necrosis factor alpha (TNF-α) −308 G/A and lymphotoxin alpha (LTα) +249 A/G single-nucleotide polymorphisms were investigated in 228 type 1 diabetes mellitus (T1DM) patients and 240 controls. Only LTα +249G allele and +249G/+249G genotype frequencies were higher among patients, and no linkage disequilibrium was found between TNF-α/LTα alleles and susceptible/protective DRB1-DQB1 haplotypes. TNF-α/LTα T1DM-susceptible (−308G/+249G) and protective (−308G/+249A) haplotypes were identified.     

Evidence for HLA class II susceptible and protective haplotypes for osteomyelitis in pediatric patients with sickle cell anemia

We investigated the association of human leukocyte antigen (HLA) class II alleles and haplotypes with the pathogenesis of sickle cell anemia (SCA) osteomyelitis. SCA patients comprised 42 patients with osteomyelitis and 150 patients without osteomyelitis; HLA-DRB1* and HLA-DQB1* genotyping was performed by polymerase chain reaction-sequence-specific priming (SSP). DRB1*100101 (P value corrected for the number of different alleles tested, Pc=0.003) was positively associated with osteomyelitis. At the haplotype level, DRB1*100101-DQB1*050101 (Pc=0.001) was more prevalent among patients, while DRB1*030101-DQB1*0201 (Pc=0.020) and DRB1*040101-DQB1*0302 (Pc=0.039) were more prevalent among SCA controls, thereby conferring disease susceptibility or protection to these haplotypes, respectively. These results show that specific HLA haplotypes influence SCA osteomyelitis risk and that specific HLA types may serve as markers for identifying SCA patients at high risk for osteomyelitis.     

A probit- log- skew-normal mixture model for repeated measures data with excess zeros,with application to a cohort study of paediatric respiratory symptoms

Background  

A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis.     

Association of Single Nucleotide Polymorphisms in Cytotoxic T-Lymphocyte Antigen 4 and Susceptibility to Autoimmune Type 1 Diabetes in Tunisians

In addition to HLA and insulin genes, the costimulatory molecule CTLA-4 gene is a confirmed type 1 diabetes (T1D) susceptibility gene. Previous studies investigated the association of CTLA-4 genetic variants with the risk of T1D, but with inconclusive findings. Here, we tested the contributions of common CTLA-4 gene variants to T1D susceptibility in Tunisian patients and control subjects. The study subjects comprised 228 T1D patients (47.8% females) and 193 unrelated healthy controls (45.6% females). Genotyping for CTLA-4 CT60A/G (rs3087243), +49A/G (rs231775), and −318C/T (rs5742909) was performed by PCR-restriction fragment length polymorphism (RFLP) analysis. The minor-allele frequencies (MAF) for the three CTLA-4 variants were significantly higher in T1D patients, and significantly higher frequencies of homozygous +49G/G and homozygous CT60G/G genotypes were seen in patients, which was confirmed by univariate regression analysis (taking the homozygous wild type as a reference). Of the eight possible three-locus CTLA-4 haplotypes (+49A/G, −318C/T, and CT60A/G) identified, multivariate regression analysis confirmed the positive association of ACG (odds ratio [OR], 1.93; 95% confidence interval [CI], 1.26 to 2.94), GCG (OR, 2.40; 95% CI, 1.11 to 5.21), and GTA (OR, 4.67; 95% CI, 1.52 to 14.39) haplotypes with T1D, after confounding variables were adjusted for. Our results indicate that CTLA-4 gene variants are associated with increased T1D susceptibility in Tunisian patients, further supporting a central role for altered T-cell costimulation in T1D pathogenesis.Type 1 (insulin-dependent) diabetes (T1D) is the most prevalent form of diabetes in children and young adults and results from autoimmune CD4⁺ and CD8⁺ T-cell-directed destruction of insulin-producing pancreatic β islet cells in genetically susceptible individuals (3, 12), leading to irreversible hyperglycemia and related complications (13). There is a strong genetic component to T1D pathogenesis, evidenced by its clustering in families and by the contributions of a number of susceptibility gene variants to its pathogenesis (10, 12, 29). They include the human leukocyte antigen (HLA) locus, in particular the class II region (DR and DQ), which accounts for 40 to 50% of T1D familial clustering (1, 12, 18), and non-HLA susceptibility loci, several of which were mapped by genome-scanning (11, 29) and/or candidate gene (7, 18, 31) approaches. They include insulin promoter gene variants, which reportedly may modulate immunological tolerance by controlling the expansion of the autoreactive cell pool (26), and the T-cell costimulator cytotoxic T-lymphocyte antigen 4 (CTLA-4) transmembrane glycoprotein, which plays a key role in the fine tuning of T-cell immunity (9, 32, 33).CTLA-4 is a 40-kDa transmembrane glycoprotein expressed on resting and activated T cells and nonlymphoid cells (33), and along with the related CD28 costimulatory molecule, it regulates T-cell activation (and is itself primarily mediated by engagement of the T-cell receptor [TCR]) but does recognize major histocompatibility complex (MHC)-bound antigenic peptides (9, 33). CTLA-4 negatively regulates T-cell activation and effector function, in part by inhibiting Th1 (interleukin 2 [IL-2] and gamma interferon [IFN-γ]) cytokine production and IL-2 receptor α-chain (p55; Tac) expression by engaging antigen-presenting cell (APC)-bound B7.1 (CD80) and B7.2 (CD86) ligands (9, 33). Functionally, CTLA-4 attenuates T-cell signaling by interference with intracellular signal transduction events, including TCR signaling, and reduced CTLA-4 expression and/or activity results in uncontrolled T-cell-associated autoimmunity and lymphoproliferative disease (9, 21). In this regard, it was shown that CTLA-4 polymorphisms significantly influence the risk of autoimmune diseases, including Graves'' disease, systemic lupus erythematosus, autoimmune hypothyroidism, celiac disease, and type 1 diabetes (15, 21, 32).First observed in Italian subjects (25), and confirmed subsequently by case control and family studies, CTLA-4 polymorphic variants were linked with T1D pathogenesis (14, 20, 31, 32). While this association was detected in different ethnic groups (14, 23, 30), it appears more likely to be Caucasian selective (10, 29, 33) and absent from non-Caucasians (5, 6, 8, 19, 22). A recent report from the Type I Diabetes Genetics Consortium bearing on 2,300 affected sib pair families demonstrated that among the 24 single nucleotide polymorphisms (SNPs) genotyped in the CTLA-4 region, only the +49A/G and CT60 SNPs were replicated in the nine combined collections (27). In the present study, we investigated the association of three common CTLA-4 SNPs (−318C/T; +49A/G, and CT60A/G) and the corresponding haplotypes with T1D in Tunisian Arab patients.     

Antibodies to β2-glycoprotein I and annexin V in women with early and late idiopathic recurrent spontaneous abortions

Anti-phospholipid antibodies (APA) are heterogeneous group of autoantibodies that target phospholipid or phospholipid-binding proteins. APAs were previously shown to induce several thrombotic states, including idiopathic recurrent spontaneous abortion (RSA). Unlike the contribution of the classical lupus anticoagulant (LAC) and anticardiolipin antibodies (ACA), the contribution of anti-β2 glycoprotein 1 (β2GPI) and anti-annexin V antibodies to RSA risk remain poorly understood. We assessed anti-β2GPI and anti-annexin V IgM and IgG antibodies as RSA risk factors for RSA in 172 Tunisian women with >3 consecutive idiopathic pregnancy losses, together with 173 matched control women. The prevalence of anti-β2GPI IgG (P=0.41, OR=1.64) and IgM (P=0.50, OR=1.70) were comparable between cases and controls. Higher anti-annexin V IgG (P=0.02, OR=5.28), but not IgM (P=0.25, OR=1.78), levels were seen in cases. Regression analysis showed that anti-β2GPI IgM (OR=8.90; 95% CI=1.23–64.63) was associated with early RSA, while anti-annexin V IgG (OR=9.35, 95% CI=1.44–60.86) was associated with late RSA. For combined early + late RSA, the only variable selected was BMI (OR=0.93; 95% CI=0.87–0.99), and neither anti-annexin V nor anti-β2GPI IgM and IgG were associated with early + late RSA. Anti-annexin V and anti-β2GPI appear to be independent risk markers of RSA.     

TNF-α −308G > A and IL-6 −174G > C polymorphisms in Tunisian patients with coronary artery disease

ObjectiveOur aim was to evaluate the contribution of tumor necrosis factor (TNF)-α ?308G > A and interleukin (IL)-6 ?174G > C gene promoter variants to the presence of coronary artery disease (CAD) in Tunisians.Design and methodsStudy subjects comprised 418 angiographically proven CAD patients and 406 age-, gender-, and ethnic origin-matched controls. Genotyping was performed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis.ResultsThere were no significant differences in the allelic distribution of TNF-α ?308A (19.6% vs. 19.0%, P = 0.73), and IL-6 ?174C (15.6% vs. 14.3%, P = 0.47) promoter polymorphisms between CAD patients and control subjects, respectively. In addition, single locus analysis revealed no differences in genotype frequencies between the two study groups, and the combined distribution of both genotypes did not differ significantly between controls and CAD patients (P > 0.05).ConclusionThere is no allelic or genotypic association of TNF-α ?308G > A and IL-6 ?174G > C promoter polymorphisms with CAD in Tunisians, thereby confirming an ethnic-selective contribution of both gene variants to CAD presence.     

Prevalence of antibodies against hepatitis C virus among blood donors in Lebanon, 1997–2000

Chronic hepatitis C virus (HCV) infection in many individuals is asymptomatic and the prevalence of antibodies to hepatitis C virus (anti‐HCV) among blood donors in Lebanon is scarce. This study aimed to address the prevalence of anti‐HCV in 8700 blood donors, the data obtained was compared to other world regions. Between 1997 and 2000, 8700 blood donors were screened for the presence of anti‐HCV in their sera. Initially reactive specimens were retested in duplicate, and repeatedly positive samples were subsequently retested by a third generation microplate enzyme immunoassay. Of the 8700 blood donors screened, 51 were confirmed positive for anti‐HCV, giving a prevalence rate of 0.6%. While there was no difference in anti‐HCV prevalence in relation to age or gender, higher rates were seen in non‐Lebanese compared to Lebanese subjects (6.17% vs. 0.48%, P < 0.001). None of the anti‐HCV positive individuals had an identifiable risk factor for contracting HCV (intravenous drug user, prior transfusion, etc.), and their transaminases were comparable to anti‐HCV‐negative donors, suggesting that HCV‐positive donors were asymptomatic. These results demonstrate low prevalence of anti‐HCV among Lebanese blood donors, which was comparable to those established for Western countries.