Polymorphisms in Interleukin-2 and Interleukin-7 Receptor α-Chain Genes and Human Herpes Virus-6 as Risk Factors for Multiple Sclerosis

Abstract

Aim: The aim of this study was to examine whether a Human herpes virus-6 (HHV-6) infection increases the risk of MS in individuals harboring particular cytokine receptor α-chain gene alleles. Study Design: MS patients and controls were assessed for HHV-6 DNA and for single nucleotide polymorphisms (SNPs) in their IL7RA and IL2RA genes. Place and Duration of Study: The study was carried out at the Department of Experimental Pathology, Microbiology and Immunology, American University of Beirut, between March 2011 and March 2013. Methodology: Blood samples from 100 MS patients and 100 controls were investigated for the presence of HHV-6 by nested PCR. Single nucleotide polymorphisms (SNPs) in the IL7RA and IL2RA genes were examined by restriction fragment length polymorphism. Results: HHV-6 was detected in 58% of MS patients and 32% of controls (OR = 2.935, 95% CI = 1.582-5.463, p=0.000). We did not detect a statistically significant correlation between MS and the studied rs2104286, rs12722489 SNPs in the IL2RA gene and rs6897932 SNP in the IL7RA gene. Concomitant presence of rs2104286 and HHV-6 was detected in 56% of patients and 30% of controls (OR=2.970, 95% CI=1.594-5.53, P=0.000). Similarly, rs6897932 and HHV-6 were observed in 57% of patients and 28% of controls (OR=3.409, 95% CI= 1.815-6.428, P=0.000). Therefore, double positivity moderately increased the risk of MS compared to either factor alone. HHV-6 and rs12722489 double positivity did not increase the risk of MS. Conclusion: HHV-6 infections may enhance the risk of MS in subjects with particular genetic determinants.