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Biomedical subjects

H Chapel

Publications and source records attributed to H Chapel.

At least 19 recordsLinked to original sources
PubMed2006

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.

Abscess↗
PubMed2004

Vitamin E deficiency induced neurological disease in common variable immunodeficiency: two cases and a review of the literature of vitamin E deficiency.

Vitamin E deficiency causes a neurological disorder characterised by sensory loss, ataxia and retinitis pigmentosa due to free radical mediated neuronal damage. Symptomatic vitamin E deficiency has been reported in genetic defects of the vitamin E transport protein and in malabsorption complicating cholestasis, abetalipoproteinaemia, celiac disease, cystic fibrosis and small bowel resection. There are no reports to date of vitamin E deficiency in patients with primary immunodeficiencies. We describe two CVID patients with the associated enteropathy who developed neurological disease because of vitamin E deficiency, suggesting a possible predisposition to developing this complication. We recommend that all CVID patients with evidence of an enteropathy be screened for vitamin E deficiency, as early detection and consequent treatment may prevent, halt or reverse the neurological sequelae.

Adult↗
PubMed2004

Prevalence of SAP gene defects in male patients diagnosed with common variable immunodeficiency.

The molecular basis of common variable immunodeficiency (CVID) is undefined, and diagnosis requires exclusion of other diseases including X-linked lymphoproliferative disease (XLP). This rare disorder of immunedysregulation presents typically after Epstein-Barr virus infection and results from defects in the SAP (SLAM associated protein) gene. SAP mutations have been found in a few patients diagnosed previously as CVID, suggesting that XLP may mimic CVID, but no large-scale analysis of CVID patients has been undertaken. We therefore analysed 60 male CVID and hypogammaglobulinaemic patients for abnormalities in SAP protein expression and for mutations in the SAP gene. In this study only one individual, who was found later to have an X-linked family history, was found to have a genomic mutation leading to abnormal SAP cDNA and protein expression. These results demonstrate that SAP defects are rarely observed in CVID patients. We suggest that routine screening of SAP may only be necessary in patients with other suggestive clinical features.

Adolescent↗
PubMed2003

Transverse sinus thrombosis and IVIg treatment: a case report and discussion of risk-benefit assessment for immunoglobulin treatment.

A 54 year old woman presented with symptoms resulting from a thrombosis of the lateral transverse and sagittal sinuses the day after an infusion of intravenous immunoglobulin (IVIg) replacement treatment. She had previously suffered a milder episode after IVIg. Following recurrent bacterial chest infections and sinusitis for more than 40 years, a diagnosis of IgG1 deficiency had been made two years earlier, after exclusion of other causes. She made a good recovery from the thrombosis but high platelet counts were investigated and primary thrombocythaemia was diagnosed. Investigation of humoral immunity revealed protective amounts of IgG antibodies to pathogens, and because the previous IgG1 deficiency had resolved IVIg infusions were not restarted. She made a good response to treatment with hydroxyurea, with improvement of the headaches and lowering of the platelet counts. Prophylactic antibiotics reduced the number of bacterial chest infections and nasal corticosteroids improved the chronic sinusitis. This case is presented to highlight the need to look for other contributing factors for severe recurrent headaches after IVIg treatment, and to consider the risk of thrombosis even when replacement doses of IVIg are used. It is also important to emphasise the need to ensure that an isolated IgG subclass deficiency is not transient; that failure to produce specific IgG antibodies to immunisation and/or exposure antigens is confirmed, thus meeting the criteria for the diagnosis of primary antibody deficiency. A thorough risk-benefit assessment is essential before blood product treatment is started.

Female↗
PubMed2002

Intravenous immunoglobulin in neurological disease: a specialist review.

Treatment of neurological disorders with intravenous immunoglobulin (IVIg) is an increasing feature of our practice for an expanding range of indications. For some there is evidence of benefit from randomised controlled trials, whereas for others evidence is anecdotal. The relative rarity of some of the disorders means that good randomised control trials will be difficult to deliver. Meanwhile, the treatment is costly and pressure to "do something" in often distressing disorders considerable. This review follows a 1 day meeting of the authors in November 2000 and examines current evidence for the use of IVIg in neurological conditions and comments on mechanisms of action, delivery, safety and tolerability, and health economic issues. Evidence of efficacy has been classified into levels for healthcare interventions (tables 1 and 2).

Drug Costs↗
PubMed2001

Does 77C-->G in PTPRC modify autoimmune disorders linked to the major histocompatibility locus?

A 77G allele of the gene encoding CD45, also known as the protein tyrosine phosphatase receptor-type C gene (PTPRC), has been associated with multiple sclerosis (MS). Here we determine allele frequencies in large numbers of MS patients, primary immunodeficiencies linked to major histocompatibility complex (MHC) locus and over 1,000 controls to assess whether aberrant splicing of PTPRC caused by the 77C-->G polymorphism results in increased susceptibility to these diseases. Our results show no difference in the frequency of the 77G allele in patients and controls and thus do not support a causative role for the polymorphism in the development of disorders with a strong autoimmune component in etiology.

Animals↗
PubMed2001

Assessment of male CVID patients for mutations in the Btk gene: how many have been misdiagnosed?

The presentation of hypogammaglobulinaemia in young males without a family history of immunodeficiency can pose a diagnostic problem. In the past, the presence of B-cells has suggested a diagnosis of common variable immunodeficiency (CVID), although genotypic analysis has now clarified that individuals with B cells may have mutations in their Btk gene. In order to address the issue of how many male individuals with a clinical diagnosis of CVID do in fact have mutations in the Btk gene, we analysed a group of 24 male patients. Single-strand conformation polymorphism (SSCP) analysis was used to screen the patient cohort for mutations in the Btk gene. Given the size of the Btk gene, the number of patients in the cohort and the amount of available DNA, multiplex PCR reactions were utilized to span the 19 exons and promoter region of the gene. Where abnormal migration patterns were observed with multiplex PCR reactions, in nine of the 24 patients, the individual Btk gene fragments were re-amplified and analysed again by SSCP. Following this analysis, four patients continued to demonstrate abnormal SSCP migration patterns. However, direct sequencing of the relevant Btk gene fragments for these four CVID patients revealed a mutation in only one patient. The mutation was the previously described polymorphism at position 2031 of Btk gene within exon 18. These results indicate that caution should be taken with the application of SSCP analysis to mutation detection. While it has a role to play in screening large patient cohorts, direct sequencing is a necessary adjunct to such analysis. Finally, the clinical diagnosis of CVID in this cohort successfully excluded males with Btk mutations.

Adult↗
PubMed2000

Impaired antibody affinity maturation process characterizes a subset of patients with common variable immunodeficiency.

Common variable immunodeficiency (CVID) is an heterogeneous syndrome characterized by decreased levels of serum Ig and recurrent bacterial infection. Here, we were interested to study whether a qualitative defect of the affinity Ab maturation process could be combined to the low level of serum Ig in a cohort of 38 CVID patients. For this, we designed a novel and rapid screening test for the detection of hypomutated V gene expressed by memory B cells. This test delineated a subset of 9/38 (23%) CVID patients with an abnormal pattern of Ig V gene mutation. The mean frequency of V gene mutation of this subset was significantly lower (1.74%) compared with other CVID patients (5.46%) and normal donors (6.5%) (p<0.0001). The mean age of this subgroup was significantly higher than other hypogammaglobulinemic patients with normal levels of V gene mutation (p<0.02), whereas no difference in the duration of symptoms was noted between the two groups. This suggests that hypomutation characterizes patients who began CVID late in life. Recently, it was shown that non-Ig sequences, such as the intronic BCL-6 gene, could be the target of the somatic hypermutation process in normal memory B cells. Our finding of a normal mutation frequency of the BCL-6 gene in two hypomutated CVID point to a defect of the Ig targeting of hypermutation machinery in these cases.

Adult↗
PubMed2000

Intravenous immunoglobulin for ANCA-associated systemic vasculitis with persistent disease activity.

Intravenous immunoglobulin (IVIg) is a potential alternative treatment for anti-neutrophil cytoplasm antibody (ANCA)-associated systemic vasculitis (AASV) with less toxicity than conventional immunosuppressive agents. This randomized, placebo-controlled trial aimed to investigate the efficacy of a single course of IVIg (total dose 2 g/kg) in previously-treated AASV with persistent disease activity in whom there was an intention to escalate therapy. Vasculitic activity was monitored by the Birmingham vasculitis activity score (BVAS), C-reactive protein (CRP) and ANCA levels. Treatment response was defined as a reduction in BVAS of more than 50% after 3 months, and there was an intention to keep doses of concurrent immunosuppressive drugs unchanged during this period; follow-up continued to 12 months. Seventeen patients were randomized to receive IVIg and 17 to receive placebo. Treatment responses were found in 14/17 and 6/17 of the IVIg and placebo groups, respectively (p=0.015, OR 8.56, 95%CI 1.74-42.2). Following infusion of trial medication, greater falls in CRP were seen at 2 weeks (p=0.02) and 1 month (p=0.04) in the IVIg group. No differences were observed between ANCA levels or cumulative exposure to immunosuppressive drugs, and after 3 months there were no differences in CRP levels or disease activity between the IVIg and placebo groups. Seventeen adverse effects occurred after IVIg and six after placebo: they were mostly mild, although reversible rises in serum creatinine occurred in four from the IVIg group. A single course of IVIg reduced disease activity in persistent AASV, but this effect was not maintained beyond 3 months; mild, reversible side-effects following IVIg were frequent. IVIg is an alternative treatment for AASV with persistent disease activity after standard therapy.

Adult↗
PubMed1999

Regulation and function of WASp in platelets by the collagen receptor, glycoprotein VI.

Wiskott Aldrich syndrome (WAS) is an X-linked recessive disorder associated with abnormalities in platelets and lymphocytes giving rise to thrombocytopenia and immunodeficiency. WAS is caused by a mutation in the gene encoding the cytoskeletal protein (WASp). Despite its importance, the role of WASp in platelet function is not established. WASp was recently shown to undergo tyrosine phosphorylation in platelets after activation by collagen, suggesting that it may play a selective role in activation by the adhesion molecule. In the present study, we show that WASp is heavily tyrosine phosphorylated by a collagen-related peptide (CRP) that binds to the collagen receptor glycoprotein (GP) VI, but not to the integrin alpha2beta1. Tyrosine phosphorylation of WASp was blocked by Src family kinase inhibitors and reduced by treatment with wortmannin and in patients with X-linked agammaglobulinemia (XLA), a condition caused by a lack of functional expression of Btk. This indicates that Src kinases, phosphatidylinositol 3-kinase (PI 3-kinase), and Btk all contribute to the regulation of tyrosine phosphorylation of WASp. The functional importance of WASp was investigated in 2 WAS brothers who show no detectable expression of WASp. Platelet aggregation and secretion from dense granules induced by CRP and thrombin was slightly enhanced in the WAS platelets relative to controls. Furthermore, there was no apparent difference in morphology in WAS platelets after stimulation by these agonists. These observations suggest that WASp does not play a critical role in intracellular signaling downstream of tyrosine kinase-linked and G protein-coupled receptors in platelets.

Blood Platelets↗
PubMed1999

Lymphoproliferative syndrome with autoimmunity: A possible genetic basis for dominant expression of the clinical manifestations.

Fas (CD95/Apo-1) mutations were previously reported as the genetic defect responsible for human lymphoproliferative syndrome associated with autoimmune manifestations (also known as autoimmune lymphoproliferative syndrome or Canale-Smith syndrome). We have identified 14 new heterozygous Fas mutations. Analysis of patients and families allow us to further dissect this syndrome with regards to the relationship between Fas mutations, inheritance pattern, and phenotype as observed on long-term follow-up. In vitro studies show that lymphocytes from all Fas mutant carriers exhibit a Fas-antibody-induced apoptosis defect. However, among the 8 inherited mutations, 4 of 4 Fas missense mutations were associated with high clinical penetrance, whereas 3 of 4 mutations leading to a truncated Fas product were associated with variable clinical penetrance. This suggests that a second defect, in another yet undefined factor involved in apoptosis and/or lymphoproliferation control, is necessary to induce full clinical expression of the disease. These results also indicate that the currently available antibody-mediated in vitro apoptosis assay does not necessarily reflect the in vivo ability of abnormal Fas molecules to trigger lymphocyte death. In addition, we found that lymphoproliferative manifestations resolved with age, whereas immunological disorders [ie, hypergammaglobulinemia and detection of TcR alphabeta(+) CD4(-) CD8(-) lymphocytes] persisted. This observation suggests that Fas-mediated apoptosis plays a more important role in lymphocyte homeostasis in early childhood than later on in life.

Adolescent↗
PubMed1999

Immune selection and genetic sequence variation in core and envelope regions of hepatitis C virus.

How Hepatitis C Virus (HCV) causes persistent infection is unknown. One hypothesis is that HCV evades the host immune response through mutation in immune epitopes. We have investigated mutations in the HCV genome to see if they cluster within immune epitopes; and we have studied the effect of antibody deficiency on mutation rates. We studied patients with chronic hepatitis C, 3 with antibody deficiency and 3 with normal immunity. Regions of the core and envelope genes of HCV, encoding cytotoxic (CTL), and B cell epitopes were sequenced at 2 time points, 2 years apart. The diversity of quasispecies increased with time. The HCV genetic mutation rate was higher than previously predicted. The cryptic nucleotide mutation rate in core was similar to that observed in envelope, suggesting that the error rate of the HCV RNA polymerase is similar in both regions. In contrast, the coding mutation rate was decreased in core and increased in envelope. No genetic mutation was seen in any of the core CTL epitopes despite detectable cellular responses. All patients had mutations within a previously described envelope CTL epitope but did not exhibit immune responses to either index or mutated peptides. There was no difference in mutation rates in any cellular or humoral epitopes between patients with antibody deficiency and normal immunity. Thus we have found no evidence that mutations were selected by T-lymphocytes or antibodies. These findings implicate alternative virus-host interactions in the selection of HCV mutations.

Adult↗
PubMed1997

Anti-cell surface endothelial antibodies in sera from cardiac and kidney transplant recipients: association with chronic rejection.

The aetiologies of accelerated or transplant-associated coronary artery disease (TxCAD) following cardiac transplantation and chronic rejection following renal transplantation remain ill-defined. Previous studies have used Western blotting to demonstrate an association between the formation of anti-endothelial (anti-EC) antibodies and TxCAD after heart transplantation. However, Western blotting favours detection of cytosolic proteins. The objectives of this study were to determine whether flow cytometry, a method which detects antigens on the cell surface, could be used to detect anti-EC antibodies and also whether the observations would extend to renal transplant patients with chronic rejection. Flow cytometry was used to look for antibodies reactive with the surface antigens of macrovascular and microvascular endothelial cell lines in sera from 44 cardiac and 35 renal transplant recipients before and after transplantation. In addition, sera from normals (n = 20), patients with nontransplant CAD (n = 50) and patients with unrelated diseases (n = 40) were investigated. Of 23 cardiac recipients who had developed TxCAD at one or two years post-transplant, 61% had IgM and 13% had IgG anti-EC antibodies post-transplantation. In contrast, in 21 cardiac recipients who had not developed TxCAD 14% had IgM and 14% IgG anti-EC antibodies. There was little evidence for the presence of anti-EC antibodies in cardiac recipients before transplantation. Of 26 renal transplant recipients whose transplants failed due to chronic rejection, 42% had IgG and 19% IgM anti-EC antibodies post-transplantation. Of nine renal recipients whose grafts were either functioning normally or who had acutely rejected, none had IgG or IgM anti-EC antibodies either pre- or post-transplantation. The anti-EC antibodies were not found in normals and were rare (less than 4%) in the other disease groups; they do not appear to be autoantibodies. In conclusion, these results suggest the FACS assay could be an informative and rapid test to provide more information on chronic rejection following cardiac and renal transplantation.

Adolescent↗
PubMed1997

Intracellular cytokine expression in whole blood preparations from normals and patients with atopic dermatitis.

In recent years, the importance of characterizing the role of cytokines in a wide range of clinical conditions has resulted in development of new methods to assess cytokine expression in clinical samples. The use of anti-cytokine MoAbs and flow cytometry to detect cytokines intracellularly at the single-cell level has the potential to quantify cytokine production in different diseases. For this technique to be useful in a clinical setting, rapid throughput of clinical samples and a cheap, reliable assay would be required, therefore the development of the above technique using unseparated whole blood samples would be advantageous. Using this technique, only one study to date (Maino et al., 1996) has used unseparated whole blood as the source of cells for detecting intracellular cytokines. In clinical practice, whole blood may be optimal, since this most closely approximates conditions in vivo: as no purification of blood mononuclear cells is required, very little blood is needed to detect a number of cytokines simultaneously in various lymphocyte subpopulations, and the assay can be applied to samples from infants and children. In this study we describe an intracellular cytokine assay using unseparated whole blood from normals. In activated CD8- T cells, IL-2 and interferon-gamma (IFN-gamma) were optimally induced after 10 h stimulation with phorbol 12-myristate acetate (PMA)/ionomycin, and in CD8+ T cells IL-2 was optimally induced after 10 h and IFN-gamma after 6 h. The levels of IL-2 and IFN-gamma in CD8+ and CD8- T cells in four healthy individuals were consistent on four occasions over a 3-month period. In a large group of 34 normal subjects, there was considerable heterogeneity in CD3/IL-2+ (range 9.7-41.3) and CD3/IFN-gamma+ cells (10.1-44), expressed as a percentage of total lymphocytes. In patients with atopic dermatitis (n = 5) there was a significantly decreased percentage of CD3+/CD8+ peripheral blood T cells expressing IFN-gamma and an increased percentage of CD3+/CD8- T cells expressing IL-4 compared with non-atopic dermatitis controls (n = 5). Possible applications of this technique are discussed.

Adult↗
PubMed1997

Clinical outcome of hypogammaglobulinaemic patients following outbreak of acute hepatitis C: 2 year follow up.

In 1994, an outbreak of hepatitis C virus (HCV) infection, genotype 1a, occurred in 30 hypogammaglobulinaemic patients in the UK from one batch of contaminated anti-HCV screened intravenous immunoglobulin. This study aimed to study prospectively the outcome of HCV in hypogammaglobulinaemic patients, and to assess the response to early treatment with interferon-alpha, 6 million units three times weekly for 6 months. Data were collected using standardized questionnaires. Five patients with secondary hypogammaglobulinaemia due to lymphoid malignancy were not treated and all have died of their primary malignancy. Of 25 patients with primary hypogammaglobulinaemia, one resolved HCV infection before treatment, 17 commenced on treatment, and seven declined or treatment was contra-indicated. Thirteen of 17 patients completed therapy and seven (54%) have a sustained response (normal transaminases, negative serum HCV RNA) at 6 and 12 months after treatment. Two of the 12 patients with primary hypogammaglobulinaemia, who were not treated or failed to complete treatment, have cleared the virus. Liver biopsy was performed in patients not clearing HCV and was abnormal in all. Four patients developed liver failure within 2 years, of whom three have died and one has been successfully transplanted. In conclusion, HCV can cause rapid severe liver disease in hypogammaglobulinaemic patients. Early treatment with high-dose interferon-alpha results in a high clearance of HCV.

Acute Disease↗