Linkage of the CCR5 Delta 32 mutation with a functional polymorphism of CD45RA

Associations of human leukocyte antigen-G with resistance and susceptibility to HIV-1 infection in the Pumwani sex worker cohort

OBJECTIVE

To determine the association between human leukocyte antigens (HLA)-G genotypes and resistance or susceptibility to HIV-1.

DESIGN

A group of sex workers in Pumwani, Kenya can be epidemiologically defined as resistant to HIV-1 infection despite frequent exposure and provide an example of natural protective immunity. HLA class I and II molecules have been shown to be associated with resistance/susceptibility to infection in this cohort. HLA-G is a nonclassical class I allele that is primarily involved in mucosal and inflammatory response, which is of interest in HIV-1 resistance.

METHODS

In this study, we used a sequence-based typing method to genotype HLA-G for 667 women enrolled in this cohort and examined the influence of HLA-G genotypes on resistance or susceptibility to HIV-1 infection.

RESULTS

The G*01 : 01:01 genotype was significantly enriched in the HIV-1-resistant women [P = 0.002, Odds ratio: 2.11, 95% confidence interval (CI): 0.259-0.976], whereas the G*01 : 04:04 genotype was significantly associated with susceptibility to HIV-1 infection (P = 0.039, OR:0.502, 95% CI:0.259-0.976). Kaplan-Meier survival analysis correlated with these results. G*01 : 01:01 genotype was associated with significantly lower rate of seroconversion (P = 0.001). Whereas, G*01 : 04:04 genotype was significantly associated with an increased rate of seroconversion (P = 0.013). The associations of these HLA-G alleles are independent of other HLA class I and II alleles identified in this population.

CONCLUSION

Our study showed that specific HLA-G alleles are associated with resistance or susceptibility to HIV-1 acquisition in this high-risk population. Further studies are needed to understand its functional significance in HIV-1 transmission.

Unusual case presentations associated with the CD45 C77G polymorphism

CD45, the leucocyte common antigen, is a haematopoietic cell specific tyrosine phosphatase. Human polymorphic CD45 variants are associated with autoimmune and infectious diseases and alter the phenotype and function of lymphocytes, establishing CD45 as an important regulator of immune function. Here we report four patients with diverse diseases with unusual clinical features. All four have the C77G polymorphism of CD45 exon 4, which alters the splicing and CD45RA/CD45R0 phenotype of lymphocytes. We suggest that C77G may be a contributing factor in these unusual cases.

Chemokine receptor 5 and primary biliary cirrhosis: a two-centre genetic association study

BACKGROUND

Chemokines and their receptors are important mediators of leucocyte trafficking and are suggested to be critical for establishment of inflammatory autoimmune processes. CC chemokine receptor 5 (CCR5) is expressed preferentially by CD4+ T cells. We hypothesised that the CCR5delta(Delta)32 genotype, which impairs surface expression of CCR5 in heterozygotes and is linked to a functional polymorphism of CD45RA expressed on suppressor-inducer-like 'naive' CD4+ T cells, may modulate the inflammatory process in primary biliary cirrhosis (PBC).

METHODS

CCR5Delta32 polymorphism was determined by PCR in 226 Caucasian PBC patients and 197 racially matched controls from two geographical areas, Newcastle, UK and Padua, Italy. (UK: 144 PBC, 105 controls, Italy: 82 PBC, 92 controls).

RESULTS

When the two series were analysed separately, there were no significant differences in the genotype distribution comparing patients and controls (UK: wt/wt 72% vs 76%; wt/Delta32 28% vs 22%; Delta32/Delta32 0% vs 2%, P=0.24; Italy: wt/wt 72% vs 82%; wt/Delta32 27% vs 17%; Delta32/Delta32 0% vs 1%, P=0.14). However, when the data for the two series were pooled and reanalysed, we found an increase in the CCR5Delta32 mutation in PBC patients vs controls (28% vs 21%, OR=1.43, P=0.03), but there was no evidence that this Delta32 polymorphism is associated with less severe disease.

CONCLUSIONS

Although this two-centre genetic association study is large compared with others performed in PBC, taken separately, each geographically based cohort of patients and controls is underpowered to detect a small effect of this functional polymorphism. This emphasises the need for far larger case-control collections to address which polymorphic markers or haplotypes might modify the pathogenesis and clinical course of PBC. We propose that multi-centre collaboration on an international scale in 'orphan' complex liver diseases such as (PBC) is supported by the International Association for the Study of the Liver and promoted via their journal with development of a brief format for web-based publication of studies.

CC chemokine receptor 5 delta32 polymorphism in two independent cohorts of hepatitis C virus infected patients without hemophilia

Recently CC chemokine receptor 5 (CCR5) related immune mechanisms and a functional mutation of the CCR5 gene have been implicated in hepatitis C virus (HCV) infection in a cohort of predominantly hemophiliac patients. The present study investigated the frequency and clinical consequences of the CCR5 Delta32 mutation in two genetically homogeneous populations of HCV infected patients with a different risk profile for infection. Genomic DNA samples from 333 German patients with chronic HCV infection were screened by PCR for the presence of the CCR5 Delta32 polymorphism. In-hospital patients admitted for other diseases than viral hepatitis but with a comparable risk for HCV exposure were used as control population ( n=125). Allele frequencies of CCR5 Delta32 polymorphism did not differ significantly between the two groups (7.6% and 9.5%, respectively) and control subjects (10.4%), and did not deviate from Hardy-Weinberg equilibrium in any group. Furthermore, there were no major differences between patients with respect to HCV genotypes, viral loads, liver enzymes, or fibrosis scores in relation to the presence or absence of the heterozygous CCR5 Delta32 mutation. Differences in inflammatory scores in liver biopsy samples and response to antiviral therapy in CCR5 Delta32 heterozygotes in one cohort could neither be reproduced in the other group of patients nor when both cohorts were pooled. These results argue against a strong effect of the CCR5 Delta32 deletion regarding these phenotypes. In conclusion, we found no increased frequency of the CCR5 Delta32 polymorphism in two independent cohorts of patients with HCV infection but without hemophilia as the main risk factor for infection. As the major difference to investigations demonstrating an association between CCR5 Delta32 and HCV infection is the selection of cases and controls, our study emphasizes the importance of epidemiological criteria for association studies of HCV infection.

PTPRC (CD45) is not associated with the development of multiple sclerosis in U.S. patients

A C-->G nucleotide transition in exon 4 of PTPRC (encoding protein-tyrosine phosphatase receptor-type C, also known as CD45) was recently reported to be genetically associated with the development of multiple sclerosis (MS). We performed an extensive evaluation of this polymorphism using large family-based and case-control comparisons. Overall, we observed no evidence of genetic association between the PTPRC polymorphism and MS susceptibility or disease course.

The exon A (C77G) mutation is a common cause of abnormal CD45 splicing in humans

The leukocyte common (CD45) Ag is essential for normal T lymphocyte function and alternative splicing at the N terminus of the gene is associated with changes in T cell maturation and differentiation. Recently, a statistically significant association was reported in a large series of human thymus samples between phenotypically abnormal CD45 splicing and the presence of the CC chemokine receptor 5 deletion 32 (CCR5del32) allele, which confers resistance to HIV infection in homozygotes. We show here that abnormal splicing in these thymus samples is associated with the presence of the only established cause of CD45 abnormal splicing, a C77G transversion in exon A. In addition we have examined 227 DNA samples from peripheral blood of healthy donors and find no association between the exon A (C77G) and CCR5del32 mutations. Among 135 PBMC samples, tested by flow cytometric analysis, all those exhibiting abnormal splicing of CD45 also showed the exon A C77G transversion. We conclude that the exon A (C77G) mutation is a common cause of abnormal CD45 splicing and that further disease association studies of this mutation are warranted.

A deletion in the gene encoding the CD45 antigen in a patient with SCID

SCID is a heterogeneous group of hereditary diseases. Mutations in the common gamma-chain (gamma(c)) of cytokine receptors, including those for IL-2, IL-4, IL-7, IL-9, and IL-15, are responsible for an X-linked form of the disease, while mutations of several other genes, including Janus-associated kinase-3, may cause autosomal recessive forms of SCID. We investigated the first SCID patient to be described with minimal cell surface expression of the leukocyte common (CD45) Ag. CD45 is an abundant transmembrane tyrosine phosphatase, expressed on all leukocytes, and is required for efficient lymphocyte signaling. CD45-deficient mice are severely immunodeficient and have very few peripheral T lymphocytes. We report here that a homozygous 6-bp deletion in the gene encoding CD45 (PTPRC, gene map locus 1q31-32), which results in a loss of glutamic acid 339 and tyrosine 340 in the first fibronectin type III module of the extracellular domain of CD45, is associated with failure of surface expression of CD45 and SCID. Molecular modeling suggests that tyrosine 340 is crucial for the structural integrity of CD45 protein. This is the second description of a clinically relevant CD45 mutation, provides direct evidence for the importance of CD45 in immune function in humans, and suggests that abnormalities in CD45 expression are a possible cause of SCID in humans.