JC polyomavirus infection is strongly controlled by human leucocyte antigen class II variants.

JC polyomavirus (JCV) carriers with a compromised immune system, such as in HIV, or subjects on immune-modulating therapies, such as anti VLA-4 therapy may develop progressive multifocal leukoencephalopathy (PML) which is a lytic infection of oligodendrocytes in the brain. Serum antibodies to JCV mark infection occur only in 50-60% of infected individuals, and high JCV-antibody titers seem to increase the risk of developing PML. We here investigated the role of human leukocyte antigen (HLA), instrumental in immune defense in JCV antibody response. Anti-JCV antibody status, as a surrogate for JCV infection, were compared to HLA class I and II alleles in 1621 Scandinavian persons with MS and 1064 population-based Swedish controls and associations were replicated in 718 German persons with MS. HLA-alleles were determined by SNP imputation, sequence specific (SSP) kits and a reverse PCR sequence-specific oligonucleotide (PCR-SSO) method. An initial GWAS screen displayed a strong HLA class II region signal. The HLA-DRB1*15 haplotype was strongly negatively associated to JCV sero-status in Scandinavian MS cases (OR = 0.42, p = 7×10(-15)) and controls (OR = 0.53, p = 2×10(-5)). In contrast, the DQB1*06:03 haplotype was positively associated with JCV sero-status, in Scandinavian MS cases (OR = 1.63, p = 0.006), and controls (OR = 2.69, p = 1×10(-5)). The German dataset confirmed these findings (OR = 0.54, p = 1×10(-4) and OR = 1.58, p = 0.03 respectively for these haplotypes). HLA class II restricted immune responses, and hence CD4+ T cell immunity is pivotal for JCV infection control. Alleles within the HLA-DR1*15 haplotype are associated with a protective effect on JCV infection. Alleles within the DQB1*06:03 haplotype show an opposite association. These associations between JC virus antibody response and human leucocyte antigens supports the notion that CD4+ T cells are crucial in the immune defence to JCV and lays the ground for risk stratification for PML and development of therapy and prevention.

Smoking and two human leukocyte antigen genes interact to increase the risk for multiple sclerosis.

Both genetic and environmental factors display low or modest associations with multiple sclerosis. Hypothetically, gene-environment interactions may exert much stronger effects. In this study, we investigated potential interactions between genetic risk factors and smoking in relation to risk of developing multiple sclerosis. A population-based case-control study involving incident cases of multiple sclerosis (843 cases, 1209 controls) was performed in Sweden. Cases and controls were classified according to their smoking status and human leukocyte antigen DRB1 as well as human leukocyte antigen A genotypes. Subjects with different genotypes and smoking habits were compared with regard to incidence of multiple sclerosis, by calculating odds ratios with 95% confidence intervals employing logistic regression. The potential interaction between different genotypes, as well as between genotype and smoking, was evaluated by calculating attributable proportion due to interaction. A significant interaction between two genetic risk factors, carriage of human leukocyte antigen DRB1*15 and absence of human leukocyte antigen A*02, was observed among smokers whereas such an interaction was absent among non-smokers. There were considerable differences in odds ratios between the various groups. Compared with non-smokers with neither of the genetic risk factors, the odds ratio was 13.5 (8.1-22.6) for smokers with both genetic risk factors. The odds ratio for smokers without genetic risk was 1.4 (0.9-2.1) and the odds ratio for non-smokers with both genetic risk factors was 4.9 (3.6-6.6). Among those with both genetic risk factors, smoking increased the risk by a factor of 2.8 in comparison with a factor of 1.4 among those without the genetic risk factors. The risk of developing multiple sclerosis associated with human leukocyte antigen genotypes may be strongly influenced by smoking status. The findings are consistent with our hypothesis that priming of the immune response in the lungs may subsequently lead to multiple sclerosis in genetically susceptible people.

HLA-A(∗)02, gender and tobacco smoking, but not multiple sclerosis, affects the IgG antibody response against human herpesvirus 6.

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system. Both genetic and environmental factors contribute to disease susceptibility and two viruses associated with MS are human herpesvirus (HHV)-6A and HHV-6B, together referred to as HHV-6. This study characterized the plasma IgG antibody response against HHV-6 in MS patients (n=446) and healthy controls (n=487), and the relationship between MS susceptibility factors and the anti-HHV-6 response was investigated. In addition, 134 samples were further investigated for IgG against the early HHV-6 antigen p41. Antibody levels were measured with ELISA. The overall seroprevalence against HHV-6 was 90%, with no significant difference in positivity or levels between MS patients and controls. Interestingly, carriership of HLA-A(∗)02 and tobacco smoking was associated with lower anti-HHV-6 IgG levels (p=0.0017 and p=0.026 respectively), whereas females sex was associated with higher levels (p=0.0090). No difference in IgG titers against p41 was observed between MS patients and controls. In conclusion, the IgG response against HHV-6 was associated with several factors that have previously been associated with MS susceptibility, possibly reflecting a relation between autoimmunity and how the immune system handles viral infections.

Lack of replication of interaction between EBNA1 IgG and smoking in risk for multiple sclerosis.

BACKGROUND: Epstein-Barr virus infection, smoking, HLA-A*02, and DRB1*15 have all been proposed as risk factors for multiple sclerosis (MS). In 2010, Simon et al. described an interaction on the multiplicative scale between EBNA1 immunoglobulin G (IgG) and smoking regarding risk of MS, a finding that we attempted to replicate. METHODS: This Swedish case-control study consisted of patients with newly diagnosed MS and matched controls. Using logistic regression, we analyzed association to MS risk and interactions between EBNA1 IgG and smoking, HLA-DRB1*15, and A*02, respectively, on the multiplicative scale. In addition, we analyzed interactions on the additive scale using attributable proportion due to interaction (AP). RESULTS: We did not observe any interaction on the multiplicative scale between EBNA1 IgG and any of the 3 risk factors, smoking, DRB1*15, or absence of A*02, although in a conditional analysis the interaction with absence of A*02 becomes significant. However, we observed interactions on the additive scale between EBNA1 IgG and DRB1*15 (AP = 0.34, 95% confidence interval 0.11-0.57, p = 5 × 10⁻³) and between EBNA1 IgG and absence of A*02 (AP = 0.36, 0.13-0.59, p = 2 × 10⁻³) but not between smoking and DRB1*15 and EBNA1 IgG. The interaction between EBNA1 IgG and DRB1*15 was not significant in the conditional analysis. CONCLUSION: We did not observe any interaction between EBNA1 IgG and smoking, regardless of scale used, and thus did not replicate the observations from Simon et al.

Confirmation of association between multiple sclerosis and CYP27B1.

Multiple sclerosis, MS (OMIM No. 126200), is a complex inflammatory disease that is characterized by lesions in the central nervous system. Both genes and other environmental factors influence disease susceptibility. One of the environmental factors that has been implicated in MS and autoimmune disease, such as type 1 diabetes, is vitamin D deficiency, in which patients have lower levels of 25-hydroxyvitamin D3 (25-OHD(3)) in blood than do controls. Previtamin D(3) is produced in the skin, and turned into 25-OHD(3) in the liver. In the kidney, skin and immune cells, 25-OHD(3) is turned into bioactive 1,25(OH)(2)D(3) by the enzyme coded by CYP27B1 (cytochrome P450 family 27 subfamily B peptide 1) on chromosome 12q13.1-3. 1,25(OH)(2)D(3) binds to the vitamin D receptor, expressed in T cells and antigen-presenting cells. 1,25(OH)(2)D(3) has a suppressive role in the adaptive immune system, decreasing T-cell and dendritic cell maturation, proliferation and differentiation, shifting the balance between T-helper 1 (Th1) and Th2 cells in favor of Th2 cells and increasing the suppressive function of regulatory T cells. Rs703842 in the 12q13-14 region was associated with MS in a recent study by the Australian and New Zealand Multiple Sclerosis Genetics Consortium (ANZgene). We show associations with three SNPs in this region in our Swedish materials (2158 cases, 1759 controls) rs4646536, rs10877012 and rs10877015 (P=0.01, 0.01 and 3.5 × 10(-3), respectively). We imputed rs703842 SNP and performed a joint analysis with the ANZgene results, reaching a significant association for rs703842 (P=5.1 × 10(-11); odds ratio 0.83; 95% confidence interval 0.79-0.88). Owing to its close association with 25-OHD(3), our results lend further support to the role of vitamin D in MS pathology.