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Stroke has emerged as the second commonest cause of mortality worldwide and is a major public health problem. For the first time, we present here the association of human leucocyte antigen (HLA)-DRB1*/DQB1* alleles and haplotypes with ischaemic stroke in South Indian patients. Ischaemic stroke (IS) cases and controls were genotyped for HLA-DRB1*/DQB1* alleles by polymerase chain reaction sequence-specific primers (PCR-SSP) method. The frequencies of HLA class II alleles such as DRB1*04, DRB1*07, DRB1*11, DRB1*12, DRB1*13, DQB1*02 and DQB1*07 were high in IS patients than in the age- and gender-matched controls, suggesting that the individuals with these alleles are susceptible to ischaemic stroke in South India. The frequencies of alleles such as DRB1*03, DRB1*10, DRB1*14, DQB1*04 and DQB1*05 were less in IS cases than in the controls, suggesting a protective association. Haplotypes DRB1*04-DQB1*0301, DRB1*07-DQB1*02, DRB1*07-DQB1*0301, DRB1*11-DQB1*0301 and DRB1*13-DQB1*06 were found to be high in IS patients conferring susceptibility. The frequency of haplotype DRB1*10-DQB1*05 was high in controls conferring protection. IS-LVD and gender-stratified analysis too confirmed these susceptible and protective associations. Thus, HLA-DRB1*/DQB1* alleles and haplotypes strongly predispose South Indian population to ischaemic stroke. Further studies in different populations with large sample size or the meta-analysis are needed to explain the exact mechanism of associations of HLA gene(s) with IS.

The HLA-DQB1* region exhibits complex associations with autoimmune thyroid disease (AITD). AITD patients (Hashimoto's thyroiditis, HT = 180; Graves' disease, GD = 55) and age/sex matched controls (n = 235) were genotyped for DQB1* alleles by PCR-SSP. Alleles DQB1*02:02, *06:03, *06:09, *03:02, and *03:03 showed an increased risk and *02:01, *05:02, and *06:02 showed a protection toward AITD. Multiple sequence alignment was used to find out the amino acid variations within the peptide-binding pockets of susceptible and/or protective DQB1* alleles. We observed susceptible associations for amino acids 'Glu(P < 0.0007)' and 'Leu(P < 3.8 × 10)' in P1, 'Leu(P < 4.0 × 10)' in P4, 'His(P < 5.0 × 10)' and 'Ala(P < 3.6 × 10)' in P9 toward HT; and 'Gly(P < 0.0004)' in P1 and 'Asp(P < 1.9 × 10)' in P9 towards GD. Protective associations were observed for amino acids 'Ala(P < 8.2 × 10)' and 'Tyr(P < 0.0003)' in P1, 'Gly(P < 4.9 × 10)' and 'Ser(P < 4.9 × 10)' in P4, 'Phe(P < 0.0007)' and 'Ser(P < 0.0016)' in P9 towards HT. Thus, the present study revealed that DQB1* alleles and putative amino acid residues play an important role in susceptibility toward AITD in south India.

Two hundred ischemic stroke patients and 193 age and sex matched healthy controls were studied for the presence of Angiotensin Converting Enzyme Insertion/Deletion (ACE I/D) gene polymorphism. The PCR studies revealed that ACE ‘II’ (OR = 2.055; p = 0.004) genotype and ‘I’ (OR = 1.411; p = 0.018) alleles were significantly associated with IS patients. Gender specific analysis revealed a strong association of ‘II’ (OR = 2.044; p = 0.014) genotype and ‘I’ (OR = 1.531; p = 0.011) allele with male sex. Classification of patients based on TOAST criteria, revealed a significant association for ‘II’ genotype (OR = 1.713; p = 0.043) and ‘I’ (OR = 1.382; p = 0.039) allele in LVD patients only. When the data was stratified based on age and sex, a statistically significant association was observed for ACE ‘II’ genotype (OR = 2.288; p = 0.006) and ‘I’ allele (OR = 1.395; p = 0.054) in IS male patients of > 50 years of age. The ACE ‘D’ allele was found to be increased in controls (OR = 0.709; p = 0.018) than IS patients. Multivariate logistic regression analysis showed that smoking and diabetes were the most powerful independent risk factor in LVD type of stroke. Thus, we presented here an evidence for a strong association of ACE ‘II’ genotype and ‘I’ allele compounded by factors such as smoking and diabetes among south Indian IS patients.