PubMed Health⌕ Search

Biomedical subjects

C Kinnon

Publications and source records attributed to C Kinnon.

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

Mutation analysis in CD40 ligand deficiency leading to X-linked hypogammaglobulinemia with hyper IgM syndrome.

Mutations in the gene encoding CD40 ligand have been shown to be the cause of X-linked hypogammaglobulinemia with hyper IgM (HIGM1). We have used the technique of single strand conformational polymorphism (SSCP) analysis to screen for mutations in this gene in affected boys from nineteen unrelated families. Sixteen novel mutations were identified in patients, comprising six patients with single base substitutions, two patients with single base insertions, six patients with deletions ranging from one to seven bases and two patients with large deletions at the 5' end of the gene. These mutations were distributed throughout the gene SSCP band shifts and/or alterations in restriction enzyme digestion sites could be used for unambiguous determination of carrier status in at-risk female relatives of most of the affected boys and, in some cases, prenatal diagnosis also can be offered.

Agammaglobulinemia↗
PubMed1996

Gene transfer into the mouse retina mediated by an adeno-associated viral vector.

Gene transfer to photoreceptor cells may provide a means for arresting the retinal degeneration that is characteristic of many inherited causes of blindness, including retinitis pigmentosa (RP). However, transduction of photoreceptors has to date been inefficient, and further limited by toxicity and immune responses directed against vector-specific proteins. An alternative vector system based on adeno-associated virus (AAV) may obviate these problems, and may be useful for transduction of neuronal cells. In this study we have demonstrated successful transduction of all layers of the neuroretina as well as the retinal pigment epithelium (RPE) following subretinal injection of recombinant AAV particles encoding lac Z. Furthermore, the efficiency of transduction of photoreceptors is significantly higher than that achieved with an equivalent adenoviral vector. This is the first report showing that AAV is capable of transducing photoreceptor cells and supports the use of this vector system for gene therapy of retinal diseases such as RP.

Animals↗
PubMed1996

X linked agammaglobulinaemia with a 'leaky' phenotype.

Typical X linked agammaglobulinaemia (XLA) is characterised by absence of immunoglobulin production and lack of mature B cells. The gene responsible for XLA has recently been identified, and codes for a B cell tyrosine kinase, BTK. A family affected by a B cell immunodeficiency, which is less severe than classical XLA, is described but they had a pedigree suggestive of X linked inheritance. Demonstration of a mutation in the BTK gene confirms that this is a mild form of XLA.

Agammaglobulinemia↗
PubMed1995

The protein product of the c-cbl protooncogene is phosphorylated after B cell receptor stimulation and binds the SH3 domain of Bruton's tyrosine kinase.

X-linked agammaglobulinemia, a B cell immunodeficiency, is caused by mutations in the Bruton's tyrosine kinase (Btk) gene. The absence of a functional Btk protein leads to a failure of B cell differentiation and antibody production. B cell receptor stimulation leads to the phosphorylation of the Btk protein and it is, therefore, likely that Btk is involved in B cell receptor signaling. As a nonreceptor tyrosine kinase, Btk is likely to interact with several proteins within the context of a signal transduction pathway. To understand such interactions, we have generated glutathione S-transferase fusion proteins corresponding to different domains of the human Btk protein. We have identified a 120-kD protein present in human B cells as being bound by the SH3 domain of Btk and which, after B cell receptor stimulation, is one of the major substrates of tyrosine phosphorylation. We have shown that this 120-kD protein is the protein product of c-cbl, a protooncogene, which is known to be phosphorylated in response to T cell receptor stimulation and to interact with several other tyrosine kinases. Association of the SH3 domain of Btk with p120cbl provides evidence for an analogous role for p120cbl in B cell signaling pathways. The p120cbl protein is the first identified ligand of the Btk SH3 domain.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Functional reconstitution of the NADPH-oxidase by adeno-associated virus gene transfer.

Chronic granulomatous disease (CGD) comprises a heterogeneous group of inherited conditions characterized biochemically by disordered function of a unique multicomponent enzyme system present in phagocytic cells, the NADPH-oxidase. Clinically, it is characterized by recurrent bacterial and fungal infections that are relatively resistant to treatment by conventional means. Curative bone marrow transplantation has been successfully achieved in a small number of cases, but the wider application of this procedure is limited by availability of suitable donor material. Somatic gene therapy would overcome this problem, and several groups have now shown correction of the biochemical defect in hematopoietic cells by retrovirus-mediated gene transfer. However, the failure of the current generation of retroviral vectors to efficiently transduce quiescent cells greatly restricts their potential for gene transfer to pluripotent hematopoietic stem cells. Given these limitations, we have constructed vectors based on adeno-associated virus and used these to transfer a functional copy of the p47phox gene to immortalized B cells derived from patients with p47phox-deficient autosomal recessive CGD. We show stable expression of protein and restoration of NADPH-oxidase function in these cells in the absence of selection. Adeno-associated virus vectors may overcome some of the limitations of retroviral gene delivery systems and may therefore be a useful vehicle for curative gene therapy of CGD and other primary immunodeficiencies.

B-Lymphocytes↗
PubMed1995

Gene transfer to primary chronic granulomatous disease monocytes.

For somatic gene therapy to become a realistic therapeutic strategy for chronic granulomatous disease (CGD), we have to be able to assign the molecular lesion to a specific component of the NADPH oxidase and to confirm that transfer of a functional copy of the corresponding defective gene will result in correction of the cellular defect. We used an adenovirus vector expressing p47phox to transduce monocytes from patients with CGD. We showed by nitroblue-tetrazolium staining that NADPH-oxidase activity was restored to these cells. This technique offers a rapid means for molecular diagnosis. In the short term, this approach may have therapeutic potential.

Adenoviridae↗
PubMed1995

Function of the interleukin-2 (IL-2) receptor gamma-chain in biologic responses of X-linked severe combined immunodeficient B cells to IL-2, IL-4, IL-13, and IL-15.

The interleukin-2 (IL-2) receptor gamma-chain is a common component of several members of the cytokine receptor superfamily including those for IL-2, IL-4, IL-7, IL-9, IL-15, and possibly IL-13, and has recently been renamed the common gamma-chain (gamma c-chain). Transfection experiments have shown that the gamma c-chain participates in signal transduction by IL-2, IL-4 and IL-7, but a functional role for the gamma c-chain in biological responses by normal T cells and B cells to these cytokines has not been established. In this study, we have used X-linked severe combined immunodeficiency (X-SCID) as a naturally occurring gamma c-chain gene disruption model to examine the role of the gamma c-chain in human B-cell responses to IL-2, IL-4, IL-13, and IL-15. Our experiments show that B cells from two X-SCID patients with characterized gamma c-chain gene mutations do not respond to IL-2 or IL-15, but respond as well or better than normal B cells to both IL-4 and IL-13 in assays for B-cell activation, proliferation, and IgE secretion. This finding raises important questions about the function of the gamma c-chain in receptors for IL-4 and IL-13, and the nature of the immune defect in X-SCID.

B-Lymphocytes↗
PubMed1995

The protein defective in X-linked agammaglobulinemia, Bruton's tyrosine kinase, shows increased autophosphorylation activity in vitro when isolated from cells in which the B cell receptor has been cross-linked.

X-linked agammaglobulinemia is a primary inherited immunodeficiency resulting in a lack of or dramatic reduction in the number of mature B lymphocytes and, thus, greatly reduced levels of serum immunoglobulin. The defect results from mutations in the gene for Bruton's tyrosine kinase (Btk). Using rabbit antisera generated against Btk, we have demonstrated an increase in the level of in vitro kinase activity present in anti-Btk immunoprecipitates from B cells following stimulation with anti-immunoglobulin antibody. This increase in immune complex kinase activity is detectable 1 to 2 min following stimulation and remains elevated for over 30 min. A similar increase was not seen with two late pre-B cell lines investigated in the same way. This stimulation of activity may suggest a role for Btk in signalling through the B cell receptor or associated proteins, in mature B cells.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Screening for mutations causing X-linked severe combined immunodeficiency in the IL-2R gamma chain gene by single-strand conformation polymorphism analysis.

Mutations in the common gamma chain (gamma c or IL2RG) of the interleukin-2, -4, -7, -9 and -15 receptors have been found to cause X-linked severe combined immunodeficiency (SCIDX1). We report here on the mutations identified in a further ten families. Two of the mutations identified have occurred twice in unrelated families, indicating two possible mutational hotspots. Seven of the mutations, which were identified by single-strand conformational polymorphism (SSCP) analysis, are point mutations, and the eighth is a small deletion. We also report on the first use of assays based on these mutations within IL2RG for unambiguous carrier determination. The consequences for the gamma c proteins produced as a result of these mutations are discussed.

Base Sequence↗
PubMed1995

Generation of recombinant adeno-associated virus (rAAV) from an adenoviral vector and functional reconstitution of the NADPH-oxidase.

The human parvovirus, adeno-associated virus-2 (AAV-2), has many attributes that recommend its use as a gene transfer vehicle, including a broad tissue tropism, the ability to integrate stably into the host genome, and efficient transduction of cells which proliferate slowly. However, application to human gene therapy is currently limited by existing methods for generation of recombinant AAV (rAAV), resulting in relatively low transducing titres. In an attempt to overcome some of these problems, we have developed a defective adenoviral vector which improves the efficiency of rAAV vector delivery to cells in which rAAV is propagated, and from which the rAAV genome can be efficiently rescued. A functional copy of the p47phox gene was successfully transferred to cell lines derived from patients with autosomal recessive chronic granulomatous disease (CGD) by rAAV recovered in this way, and function of the NADPH-oxidase was restored to levels which were stable for at least 8 weeks. This method for generation of rAAV, although still limited by the need for cotransfection of AAV Rep and Cap functions, may permit recovery of higher titre transducing stocks from cell lines in which these genes are stably incorporated, and significantly reduces the risk of contamination with wild-type adenovirus (wtAd).

Adenoviridae↗
PubMed1994

p22-phox-deficient chronic granulomatous disease: reconstitution by retrovirus-mediated expression and identification of a biosynthetic intermediate of gp91-phox.

Chronic granulomatous disease (CGD) results from defects in the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, central to which is the membrane-bound cytochrome b-245. The cytochrome is composed of two protein subunits, the larger (gp91-phox) being deficient in X-linked CGD. In this study, we have analyzed expression of the cytochrome subunits in B-cell lines from two autosomal CGD patients for whom the disease is caused by deficiency of p22-phox, the smaller subunit. We report the presence of a 65-kD precursor of gp91-phox in the membrane fraction of both p22-phox-deficient cell lines, corresponding to the core protein with N-linked carbohydrate side chains in the high mannose form. Expression of p22-phox in these cells resulted in functional correction of NADPH oxidase. In addition, gp91-phox in the reconstituted cells was processed to its terminally glycosylated form. These data suggest that the association of the 65-kD gp91-phox precursor with p22-phox is a prerequisite for processing of the carbohydrate side chains to the complex form in the Golgi. The detection of this precursor will enable characterization of mutations disrupting the subunit interaction (either naturally occurring or derived by in vitro mutagenesis) and so aid in structure-function analysis of cytochrome b-245. Reconstitution of p22-phox-deficient cells shows the potential of gene therapy for this autosomal form of CGD.

B-Lymphocytes↗