P5443Association of G allele of CTLA 4 1661 A/G polymorphism with susceptibility and severity of rheumatic heart disease

Abstract

Background: Rheumatic heart disease (RHD), a prevalent cause of heart failure in majority of the developing countries, is characterized by progressive and per-manent valvular lesions. Environmental as well as genetic factors are known to play a notable role in the pathogenesis of RHD. Several single nucleotide polymorphisms (SNPs) in genes that code for inflammatory molecules and contribute to predisposition and manifestation of the disease have been investigated. CTLA-4 gene is found to be co-localized on band q33 of human chromosome 2. It is a co-stimulatory molecule and is expressed on the surface of activated T-cells, and plays a pivotal role in the inhibition of T-cell activation and peripheral tolerance. It is a negative regulator of T-cell activation and alteration of its expression may have a notable effect in immune-mediated diseases. Two SNPs -318 C/T and +49 A/G of CTLA-4 have been studied with respect to RHD; whereas, a third SNP -1661 A/G has been less characterized, although it has been associated with type 1 diabetes mellitus, systemic sclerosis, multiple sclerosis and oral squamous cell carcinoma thus indicating a correlation between this SNP and autoimmune diseases. Purpose: In this study, we conducted a case-control interpretation to look for any association of four SNPs namely, -1661 A/G, +49 A/G, -318 C/T of CTLA-4 and -308 C/T of TNF-α with RHD. Methods:. Through the outpatient clinic, a total of 83 RHD North-Indian patients and 291 healthy unrelated North-Indian controls were recruited, and their demographic and clinical profile was recorded. Genotyping was performed using SNaPshot ddNTP Primer Extension PCR. Results: Among the 4 SNPs, -1661 A/G emerged as significant with respect to disease severity with the minor G allele being less frequent in RHD patients compared to the controls (p<0.05). Importantly, segregation of patients on the basis of severity i.e. MVL (Mitral Valve Lesion) and CVL (Combined Valve Lesion) revealed that the G allele depleted as the disease progressed to CVL (p<0.05). Patients in the middle age group of 31-45 years were significantly more susceptible (p<0.046), whereas the number of patients in the upper age group of 46-60 was significantly less to achieve statistical significance. Also, a significant difference was observed in the dominant genotype -1661 A/G frequency of CTLA-4 (p=0.049) as well as the additive model's G allele frequency (p=0.040) in females. Conclusion: Present study thus reports the association of depletion of G allele of CTLA-4 -1661 A/G SNP with susceptibility of RHD. It also explains the higher susceptibility of females for RHD. Moreover, it also correlates with the severity of disease in the form of multivalvular involvement.