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Biomedical subjects

A D Webster

Publications and source records attributed to A D Webster.

At least 55 records · Page 3Linked to original sources
PubMed1996

Prevalence of hepatitis C in patients with primary antibody deficiency.

Concern over sporadic hepatitis C virus (HCV) infection from treatment with contaminated immunoglobulin in patients with immunodeficiency prompted use to screen serum from 44 patients for HCV RNA. We found no evidence of either horizontal or iatrogenic infection in our Clinic, except in two patients known to have received contaminated batches, and in one who had had regular plasma infusions. Thus, common variable immunodeficiency (CVID) patients in England do not have a high incidence of HCV infection despite exposure to various immunoglobulin products. This contrasts with the recently reported high prevalence in similar patients in Italy. Although our data reinforce the impression that both intramuscular and current licensed i.v. preparations in the UK are safe, manufacturers should be encouraged to PCR screen all batches of immunoglobulin for HCV.

Agammaglobulinemia↗
PubMed1996

Intracellular cytokine production by human CD4+ and CD8+ T cells from normal and immunodeficient donors using directly conjugated anti-cytokine antibodies and three-colour flow cytometry.

Using three-colour flow cytometry, we have measured intracellular IL-2, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) induced in human CD4+ and CD8+ T cells from normal donors and patients with common variable immunodeficiency (CVID). Since a new range of directly FITC-conjugated anti-cytokine antibodies was used, conditions were optimized for the concentration of antibody, for cell permeabilization and fixation, and for the time of exposure to monensin to retain the cytokines within the cell. Kinetics of intracellular cytokine production were measured for up to 20 h in culture with phorbol myristate acetate (PMA) and ionomycin, or with phytohaemagglutinin (PHA). Kinetic studies of activation with PMA and ionomycin show that a higher proportion of normal CD4+ cells can make IL-2 than the other two cytokines, and that there are more TNF-alpha-positive CD4+ cells than cells with IFN-gamma. For normal CD8+ cells the highest production of cytokine is of IFN-gamma (up to 50% of the cells) especially at longer times (10-20 h) of stimulation. For CD8+ cells, IL-2-positive cells exceed those with TNF-alpha. The other mitogenic stimulus used (PHA) was grossly inferior to PMA and ionomycin in its ability to induce intracellular cytokines. The time of exposure to monensin was also examined. Its continuous presence in the cultures (up to a maximum of 20 h) increased the detection of IL-2-positive cells without apparently reducing the percentage of cytokine-positive CD4+ or CD8+ cells. Finally, using optimal conditions, we compared cytokine production in cells from patients with the disease CVID and showed normal cellular levels of ability to produce IL-2 and TNF-alpha but significantly raised levels of production of IFN-gamma in both CD4+ and CD8+ lymphocytes. This suggests that the pathology of this disease may involve an excessive Th1-type response.

Adult↗
PubMed1996

Encephalomyelitis in primary hypogammaglobulinaemia.

The neurological features of 13 patients with primary hypogammaglobulinaemia are described. Seven patients had X-linked agammaglobulinaemia (XLA) and six had common variable immunodeficiency (CVID). Three clinical pictures emerged: (i) a progressive myelopathy (one case); (ii) a myelopathy progressing to an encephalopathy (four cases); (iii) a pure encephalopathy (eight cases). In four patients the encephalopathy was temporarily reversible; the relationship of this to immunoglobulin therapy is unclear. Additional features occurred in some patients. Three had retinopathy interpreted as retinitis pigmentosa, in one of whom the retinopathy resolved. Two patients had a sensori-neural hearing loss and three had features of dermatomyositis; a variable pleocytosis was found in the CSF of nine patients. Imaging revealed atrophic changes in the cerebral hemispheres in eight cases. Ten patients have died, 1-11 years after the onset of the CNS manifestations, and in four autopsies were obtained. Two patients had encephalopathy, one with XLA had evidence of end-stage encephalitis and the other with CVID had a multi-focal leucoencephalopathy. The other two with XLA had leptomeningitis without evidence of encephalitis. Enteroviral infection is probably an important cause of neurological disease in these patients as CSF from seven patients was either positive by polymerase chain reaction (PCR) or by culture for enteroviruses. Other possible mechanisms are discussed.

Adolescent↗
PubMed1996

Exon-scanning mutation analysis of the ATM gene in patients with ataxia-telangiectasia.

Using a polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) assay, which amplifies individually all coding exons of the ATM gene deficient ataxia-telangiectasia (A-T), we have analyzed 10 patients with A-T for ATM mutations. Mutation were detected in 9 patients. We describe the first ATM mutation in the splice junction found in the 5' splice site of intron 17, leading to exon skipping. However, most mutations were small deletions or insertions resulting in premature termination of the translation product. The development of DNA-based methods for detection of unknown mutations and further characterization of ATM mutation pattern will facilitate identification of A-T carriers and assessment of their cancer risk.

Ataxia Telangiectasia↗
PubMed1995

Family and linkage study of selective IgA deficiency and common variable immunodeficiency.

Screening of close relatives of Swedish patients with selective immunoglobulin A deficiency (IgAD) and common variable immunodeficiency (CVID) for serum immunoglobulin levels has identified the positive family history of IgAD/CVID as the most significant risk factor for developing the disease. The relative risk for siblings of patients with IgAD was estimated to be approximately 50. In 12 of 34 Swedish multiplex families identified in the study, both IgAD and CVID occurred, usually CVID in the parental generation and IgAD in the subsequent generation. This proportion was much higher than expected by chance and strongly suggests that the two clinically discernible disorders represent an allelic condition, reflecting a variable expressivity of a common defect. In 27 multiplex families the disorders segregated as an autosomal dominant trait, affecting at least two generations. A high relative risk for siblings, permanent phenotype, low number of phenocopies, and common population prevalence, which makes it possible to obtain a sufficient sample size, make these immunoglobin deficiencies amenable to genetic linkage analysis. In a pilot multicenter linkage study involving 16 multiplex families with dominant transmission of IgAD/CVID, we have attempted to confirm previously reported genetic linkage of the disease susceptibility to the major histocompatibility complex (MHC) region. Using both parametric and nonparametric linkage analyses with a set of microsatellite markers at and flanking the MHC region, no evidence for linkage was found. In accordance with these results, no evidence for linkage to the MHC region was obtained by analyzing previously published segregation data at the MHC region in multiplex families with IgAD/CVID in more than one generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Common Variable Immunodeficiency↗
PubMed1995

Orthotopic liver transplantation for chronic hepatitis in two patients with common variable immunodeficiency.

Two patients with common variable immunodeficiency underwent orthotopic liver transplantation for chronic hepatitis, unequivocally caused by hepatitis C virus in one case. Although one patient had pneumonia 8 days after surgery and the other developed hepatic venular stenosis in the transplanted liver, both had a reasonably good quality of life for at least 15 months. However, both subsequently died of recurrent hepatitis C virus hepatitis or hemorrhage after splenectomy for hypersplenism. This shows that severe infection is not a major problem in patients with common variable immunodeficiency after liver transplantation provided they undergo prophylactic antimicrobial and immunoglobulin therapy. The longer term prognosis must be regarded as poor until more data are available following transplantation in similar patients.

Adolescent↗
PubMed1995

Mediastinal lymph node enlargement and splenomegaly in primary hypogammaglobulinaemia.

The computed tomography (CT) scans of 37 patients with primary hypogammaglobulinaemia were reviewed to determine the frequency of enlarged mediastinal lymph nodes and splenomegaly in this group. None of the 10 X-linked Agammaglobulinaemia (XLA) patients had enlarged nodes and only one had splenomegaly. Eleven of the 27 Common Variable Immunodeficiency (CVID) group had enlarged nodes (41%) and 13 had splenomegaly (48%). There was no significant correlation between the presence of enlarged nodes and splenic enlargement. Twenty-two patients had bronchiectasis but the presence of bronchiectasis did not correlate with the presence of either splenomegaly or lymphadenopathy. Three to 6 years follow-up is available for 36 of the 37 patients and none of this group have developed lymphoma or other malignancy. Enlarged mediastinal nodes and/or splenomegaly are frequently found in patients with CVID and are usually due to a benign, non-neoplastic, process. Mediastinal lymph node enlargement is not a feature of XLA and splenomegaly is unusual in this condition.

Adolescent↗
PubMed1995

Structural basis for X-linked agammaglobulinemia (XLA): mutations at interacting Btk residues R562, W563, and A582.

It has been suggested that tryptophan 563 is sandwiched between residues R562 and A582 in Bruton's agammaglobulinemia tyrosine kinase (Btk). Mutations of the surrounding residues have been shown to cause X-linked agammaglobulinemia. Substitutions R562P and A582V were noticed to have impaired kinase activity. However, based on Western blot analysis, the mutant proteins were expressed at normal levels. Molecular modeling of the kinase domain has previously indicated that these residues presumably govern the position of the W563 side chain, which is thought to interact with the catalytic loop. W563 is inside the molecule and too far away from the catalytic center to interact directly with the substrate or cofactors. To prove these model-based conclusions, a conservative substitution with phenylalanine for W563 was made, and the resultant mutant lacked kinase activity. These results confirm our previous assumption that the side chain of W563, invariant in protein tyrosine kinases, is crucial for Btk kinase activity. Mutations in the surrounding residues seem to inactivate Btk by affecting the location of W563.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Identification of Btk mutations in 20 unrelated patients with X-linked agammaglobulinaemia (XLA).

X-linked agammaglobulinaemia (XLA) is an inherited immunodeficiency resulting from mutations in the gene for a cytoplasmic protein tyrosine kinase (Btk). We have utilised reverse-transcription-based PCR in combination with the chemical cleavage and mismatch technique (CCM) to screen for Btk mutations in 42 unrelated patients having classical XLA or 'leaky' XLA-like phenotypes. A variety of mutations, including point mutations, large deletions and splicing defects were detected using this strategy. In total, 20 mutations were found in these patients. All the mutations were different with the exception of three unrelated patients who all showed the same Arg-->His amino acid substitution (R641H) at a highly-conserved residue in the kinase domain. We have also used structural modelling of the Btk kinase domain to predict how two different amino acid substitution mutations at highly-conserved residues are likely to affect the Btk kinase activity.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Defects in antigen-driven lymphocyte responses in common variable immunodeficiency (CVID) are due to a reduction in the number of antigen-specific CD4+ T cells.

T cells from patients with CVID have defects that may relate to the failure in vivo of B cell production of antibodies. Antigen-driven responses of T cells from CVID patients and normal subjects have been assessed by measuring DNA synthesis in vitro. Low density cells enriched for antigen-presenting dendritic cells were pulsed with purified protein derivative (PPD) and cultured with autologous T cells. Overall, T cells from CVID patients showed a significantly low mean response to PPD, although non-specific DNA synthesis induced in CVID T cells by IL-2 was within the normal range. However, mean PPD-specific T cell responses in CVID were not restored by IL-2 irrespective of the presence of monocytes. Depletion of CD8+ cells also failed to restore the mean PPD response of CVID CD4+ T cells. Limiting dilution analysis showed that in CVID there was a reduced frequency of antigen-specific cells within the T cell preparations. The mean frequency of the PPD-specific T cells in cultures from patients vaccinated with bacille Calmette-Guérin (BCG) was reduced to 1 in 109,000 T cells compared with 1 in 18,600 T cells in BCG-vaccinated normal donors. These data show that the reduced PPD-specific response in CVID is due to a partial peripheral loss of antigen-specific cells.

Adult↗
PubMed1995

A prospective controlled crossover trial of a new heat-treated intravenous immunoglobulin.

Twenty-one patients with primary immunoglobulin deficiency were enrolled in a crossover study to test the efficacy and safety of Alphaglobin in comparison with the licensed preparations Sandoglobulin and Gamimune. There was no statistical difference in these parameters between Alphaglobin and Sandoglobulin/Gamimune. The level of total serum IgG and specific IgG to pneumococcal polysaccharides was similar in individual patients when they were receiving Alphaglobin or one of the other products. Transient increases in serum alanine transferase occurred in five patients on Sandoglobulin/Gamimune and two patients on Alphaglobin. Some patients showed a rise in total serum IgM afterwards, indicating a response to infection. However, serum hepatitis C virus (HCV) RNA was not found during the alanine transferase (ALT) rises, and IgM antibody to hepatitis A virus (HAV) was negative afterwards. We conclude that Alphaglobin is a safe, well tolerated and clinically efficacious treatment for patients with primary antibody deficiency.

Adult↗
PubMed1994

Structural basis for chromosome X-linked agammaglobulinemia: a tyrosine kinase disease.

X-linked agammaglobulinemia (XLA) is a hereditary defect of B-cell differentiation in man caused by deficiency of Bruton tyrosine kinase (BTK). A three-dimensional model for the BTK kinase domain, based on the core structure of cAMP-dependent protein kinase, was used to interpret the structural basis for disease in eight independent point mutations in patients with XLA. As Arg-525 of BTK has been thought to functionally substitute for a critical lysine residue in protein-serine kinases, the mutation Arg-525-->Gln was studied and found to abrogate the tyrosine kinase activity of BTK. All of the eight mutations (Lys-430-->Glu, Arg-520-->Glu, Arg-525-->Gln, Arg-562-->Pro, Ala-582-->Val, Glu-589-->Gly, Gly-594-->Glu, and Gly-613-->Asp) were located on one face of the BTK kinase domain, indicating structural clustering of functionally important residues.

Adenosine Triphosphate↗
PubMed1994

Adult onset immunodeficiency caused by inherited adenosine deaminase deficiency.

Adenosine deaminase (ADA) deficiency is identified here as a cause of adult onset immunodeficiency. Two sisters who noted recurrent, predominantly chest infections in their twenties were found in their thirties to have CD4+ lymphopenia and lymphocyte ADA activity of approximately 5% of the lower limit of normal. Immune function, measured by proliferation of PBMCs in vitro to mitogens and specific Ags, was impaired. Inheritance of a polymorphic marker showed that both patients were heterozygous at the ADA locus. In the paternal allele there was a deletion resulting from homologous recombination between two alu elements that normally flank the first exon and the polymorphic marker. The recombination site was distinct from that in similar deletions described in two infants having severe combined immunodeficiency. This allele is predicted to result in a null phenotype. In the mutant allele inherited from the mother, a C to T transition in a CpG dinucleotide changed the codon for arginine 211, which lies in a conserved sequence close to the active site, to that for cysteine. This mutation has been observed previously in a child in whom the other allele was also a null mutation, but who was diagnosed as having partial ADA deficiency because immune function was apparently normal. The late onset of immunodeficiency in our patients suggests that immune function in children with partial ADA deficiency may deteriorate with time and that ADA deficiency should be regarded as a possible cause of adult onset immune dysfunction of unknown etiology.

Adenosine Deaminase↗
PubMed1994

Hepatitis C virus transmission by intravenous immunoglobulin.

The polymerase chain reaction was used to detect hepatitis C virus infection in patients who had previously been reported to have developed non-A, non-B hepatitis after intravenous immunoglobulin infusion. Of the 33 patients with intravenous immunoglobulin associated non-A, non-B hepatitis studied, HCV RNA could be detected in 15 out of 17 patients (88%) who were HCV RNA negative prior to the development of non-A, non-B hepatitis after implicated intravenous immunoglobulin batches. Similarly, eight out of nine patients (89%) in whom no sample was available for polymerase chain reaction testing prior to intravenous immunoglobulin therapy, had detectable HCV RNA after intravenous immunoglobulin therapy with intravenous immunoglobulin batches implicated in non-A, non-B hepatitis transmission. Two of the three intravenous immunoglobulin preparations implicated in non-A, non-B hepatitis transmissions that were available for polymerase chain reaction testing also had detectable HCV RNA, confirming that hepatitis C virus is the implicated virus in intravenous immunoglobulin-associated non-A, non-B hepatitis.

Hepacivirus↗