Investigate the Effect of Streptococcal Infection and CTLA-4 gene polymorphism in the Onset of Autoimmune Hashimoto’s Disease

Background: The global incidence of Hashimoto's thyroiditis (HT) is rising worldwide. Bacterial infections and polymorphisms in genes related to immune function may contribute to the development of the disease. Objectives: This study aimed to investigate the impact of post-streptococcal infection and CTLA-4 gene polymorphisms on the predisposition to HT. Methodology: Eighty participants were recruited for this case-control study, including 30 healthy controls and 50 HT patients attending the Endocrinology and Diabetes Center at Al-Sader Medical City. Blood samples were collected from all participants to measure serum levels of TSH, T3, and T4 using the Cobas E114 Roche analyzer. Thyroid peroxidase antibodies (TPO) were measured by electro-Chemiluminescence immunoassay, anti-streptomycin O (ASO) titers by a latex reagent test kit, and CTLA-4 levels by enzyme-linked immunosorbent assay (ELISA) (Biotech, China). Additionally, 1 ml of blood was collected in EDTA tubes for detection (−318 C>T) CTLA-4 gene polymorphism using Tetra-Amplification Refractory Mutation System PCR (T-ARMS-PCR) technique. Results: The female to male ratio was 3:1 in both patients and controls. Mean serum levels of TSH and TPO were significantly higher in patients compared to controls. ASO titers were markedly elevated in patients (309.32±38.5 U/ml) compared to the healthy group (56.04 ± 18.1 U/ml). CTLA-4 serum levels were also increased in patients (1.36 ± 0.094 pg/ml) versus healthy individuals (0.88±0.063 pg/ml). Analysis of the rs5742909 polymorphism showed that the TT genotype was more frequent in patients (56%) than in healthy controls (33%). The T allele was identified as a risk factor, whereas the C allele appeared to be protective. Conclusion: Both ASO titers and CTLA-4 levels are useful predictors for the onset of Hashimoto’s thyroiditis. The −318 C/T promoter polymorphism in the CTLA-4 gene is associated with an increased risk of developing HT.