CCR5 genotyping in an Australian and New Zealand type 1 diabetes cohort.

Infiltration of pancreatic tissue by autoreactive T-cells involves secretion of multiple cytokines and chemokine receptor expression. Genetically determined variation in cell surface expression of the chemokine receptor CCR5 may result in differences in inflammatory cell migration in response to relevant chemokines. Adolescents with type 1 diabetes (T1D) from Australia and New Zealand were genotyped for CCR5-delta32 (n = 626). The allele frequency was compared with that of 253 non-diabetic Australian adolescents and with that of 92 adults with systemic lupus erythematosus. A reduced allele frequency was seen in T1D compared with controls (0.092 vs. 0.123, p = 0.05). This difference was not seen for the cohort of patients with SLE (freq = 0.114). A reduction in the number of CCR5-delta32/delta32 homozygotes, who lack CCR5, in the T1D cohort was also seen and while not statistically significant (2 observed compared to 5.25 expected; p = 0.12) is interesting. These results suggest a partial protection from T1D for CCR5-delta32 homozygous individuals is possible and that CCR5 has a potential role in the pathogenesis of T1D.

T cell receptor beta chain genotyping in Australian relapsing-remitting multiple sclerosis patients.

This study focused on susceptibility to MS within the beta-chain of the T-cell antigen receptor (TCRB locus, 7q35) in a cohort of 122 RR-MS patients compared with 96 normal individuals using biallelic polymorphisms across the bv8s1(Vbeta8.1) to bv11s1 (Vbeta11) TCRB subregion. The markers bv6s5, bv8s1, bv10s1, bv15s1 and bv3s1 were studied for allele and genotype frequencies; haplotypes were assigned with combinations of two of these markers and stratification for HLA-DR15 was also performed. Linkage disequilibrium was found between alleles of the bv8s1, bv10s1/bv15s1 and bv3s1 loci in both patients and controls. An increase among RR-MS patients in the allele frequency of bv8s1*2 (P=0.03) and the haplotype bv8s1*2/bv3s1*1 (P=0.006) was noted and both were found to be statistically significant. In the DR15-positive group, the association between TCRB and MS was seen with the bv8s1*2 allele (Puc=0.05) and the bv8s1*2/bv10s1 haplotypes (Puc=0.048), while the haplotype associations seen among DR15-negative RR-MS patients included the bv3s1*1 allele (bv10s1*1/ bv3s1*1, Puc=0.022; bv8s1*2/bv3s1*1, Puc=0.048). These results support the involvement of the TCRB region in MS susceptibility and encourage further study of the variable gene segments in this region.

Evaluation of the apo-1/Fas promoter mva I polymorphism in multiple sclerosis.

The pathogenesis of multiple sclerosis is under strong genetic control involving several or more genes each of modest effect. Whilst the mechanisms underlying the pathogenesis of MS remain unknown, it has been hypothesised that either decreased apoptosis of autoreactive T cells in the CNS, or increased apoptosis of oligodendrocytes may play an important role. The Apo-1/Fas antigen (CD95), the gene for which is located in a chromosomal region showing linkage in MS genome screens, is a critical inducer of apoptosis and studies have shown aberrant expression of this molecule in MS, correlating with a decrease in T cell apoptosis or increase in CNS tissue damage. This study investigated an Mva I polymorphism in the Apo-1/Fas promoter region in a group of 124 Australian patients with relapsing-remitting MS and in 183 normal controls. Whilst there were increases in the Mva I*2 allele in MS individuals overall (59% vs 52%, P not corrected=0.08), and in HLA-DRB1*1501 negative MS patients (62% vs 55%), these were not significantly different from controls. Interactions were investigated between the Mva I alleles and T cell receptor beta chain variable region (TCRBV) germline polymorphisms, with a trend in MS individuals towards a decrease of the Mva I*1 allele when combined with the TCRBV3S1*2 allele (Relative Risk=0.25, P=0.067), and with the TCRBV8S1*1 allele (Relative Risk=0.44, P=0.12). Overall, the findings of this study indicate a possible effect of the Apo-1/Fas promoter Mva I polymorphism in MS susceptibility, which needs to be confirmed in further studies. Multiple Sclerosis (2000) 6 14 - 18

HLA-DMB gene and HLA-DRA promoter region polymorphisms in Australian multiple sclerosis patients.

The MHC region has been shown to contain a susceptibility locus for multiple sclerosis (MS). While the strongest association to date has been between HLA-DRB1*1501 and MS, the exact nature of the MHC association in MS remains unclear. Two candidate polymorphic loci within the MHC class II region, the HLA-DMB gene and the HLA-DRA promoter, which lie close to HLA-DRB1, were therefore examined in an Australian MS population. The HLA-DMB*0103 phenotype was increased in the MS patients (46% vs. 30%) and the frequency of the HLA-DRA promoter A allele was also increased (81% vs. 68%). When the subjects were stratified into HLA-DRB*1501 positive and negative individuals these associations were not significantly different. This is a result of the strong linkage disequilibrium between HLA-DRB*1501 and both HLA-DMB*0103 and the HLA-DRA promoter A allele. The complete linkage between DRB1*1501 and the HLA-DRA promoter A allele indicates that the MS susceptibility haplotype (DRB1*1501-HLA-DQB1*0602-HLA-DQA1* 0102) can be extended out to promoter of the HLA-DRA locus. Interactions between both HLA-DMB and the HLA-DRA promoter and other reported MS susceptibility loci were examined (TCRBV polymorphisms, HLA-DQA1 and HLA-DQB1). Some interactions between specific TCRBV polymorphisms and the HLA-DRA promoter were observed, which is consistent with other published reports suggesting an epistatic interaction between TCRBV and HLA-DRB1.

The DRB1 Val86/Val86 genotype associates with multiple sclerosis in Australian patients.

Genetic susceptibility to multiple sclerosis (MS) has so far been strongly localized to the MHC class II region encoding the alleles of the haplotype HLA-DRB1*1501, -DQA1*0102, -DQB1*0602. However, this haplotype is not carried by approximately 40% of MS patients; a potential explanation could be that they carry other MHC class II alleles with similar function due to the sharing of nucleotide sequences encoding critical amino acid residues. The DRB1 gene is polymorphic at residue 86, encoding valine or glycine. In view of the increasing evidence for a functional role for DRB1 aa86 in the binding and presentation of autoantigenic peptides such as myelin basic protein, this study investigated associations with the residue 86 polymorphism in an Australian MS population. A significant increase in the Val86/Val86 genotype was observed in the MS patients, which was still present in the absence of the DRB1*1501 allele (p = 0.032). This suggest that DRB1 aa86 may have an independent role in contributing to MS susceptibility. The Val86/Val86 genotype was correlated with genotyping for other putative MS susceptibility genes, including T cell receptor beta chain germline polymorphisms, HLA-DMB alleles, and -DQA1 and -DQB1 alleles encoding critical amino acid residues, with a significant interaction only observed with DQB1 Leu26 (p = 0.014). Additional studies of the HLA-DRB1 aa86 polymorphism in MS, and its function, are needed to more fully understand this association.

The CCR5 deletion mutation fails to protect against multiple sclerosis.

Recent advances in the understanding and identification of chemokines and their receptors have provided evidence for their consideration as candidate loci with respect to genetic susceptibility/resistance to MS. Increased levels of the chemokine, macrophage inflammatory protein (MIP)-1 alpha, have been demonstrated in the cerebrospinal fluid of both patients with MS and mice with EAE, and anti-MIP-1 alpha antibodies have been shown to prevent EAE. Recently, a common deletion mutation in the gene for the major receptor for MIP-1 alpha, chemokine receptor 5 (CCR5) has been described. Homozygotes for the mutation fail to express this receptor. Moreover, homozygotes are highly protected against HIV infection this has potential implications for the cell entry of infectious agents in other multifactorial disease where a viral component may be involved. In view of these aspects, a group of 120 unrelated Australian relapsing remitting MS and 168 unrelated control subjects were screened for the CCR5 delta 32 mutation. There was no significant difference in the allele frequency of CCR5 delta 32 gene between the MS patients (0.1125) and the control population (0.0921). The presence of two CCR5 delta 32 homozygotes in the MS patients indicates that the absence of CCR5 is not protective against MS. These data suggest that CCR5 is not an essential component in MS expression, though this may be due to redundancy in the chemokine system where different chemokine receptors may substitute for CCR5 when it is absent.

HLA-DPB1 alleles correlate with risk for multiple sclerosis in Caucasoid and Cantonese patients lacking the high-risk DQB1*0602 allele.

Multiple sclerosis (MS) is a demyelinating disease associated with the HLA-DR2-related haplotype DRB1*1501, DQB1*0602 in Caucasoids and with DQB1*0602 in DR2-positive Cantonese. However, many MS patients do not have the high-risk HLA-D determinants and alternative genes may contribute to the pathogenesis of MS. One candidate gene is HLA-DPB1. Our reanalysis of five earlier reports of HLA-DPB1 antigen distributions in Caucasoid MS patients shows a consistent and highly significant increase (p = 1.5 x 10(-5)) in frequency of HLA-DPw3 in the combined data set. This study tests whether HLA-DPw3 (DPB1*0301) is also increased in frequency in Australian and Cantonese MS patients and whether any distortion in DPB1 allelic distributions can be attributed to linkage disequilibrium with DQB1*0602. PCR-RFLPs were used to determine distributions of 20 HLA-DPB1 alleles in 41 Australian MS patients and 67 controls of known DQB1*0602 status and in 11 Cantonese MS patients and 33 controls positive for HLA-DR2. HLA-DP distributions in Australian MS patients and controls positive for DQB1*0602 did not differ, but in those MS patients lacking DQB1*0602, the DPB1*0301 antigen (phenotype) frequency was significantly (p = 0.006) increased (50.0%) when compared with DQB1*0602-negative controls (9.1%). DPB1*0301 was associated (p = 0.003) with DQB1*0402 (DR8) in Caucasoid MS patients.(ABSTRACT TRUNCATED AT 250 WORDS)