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Biomedical subjects

Nigel Klein

Publications and source records attributed to Nigel Klein.

13 recordsLinked to original sources
PubMed2005

Relationship between changes in thymic emigrants and cell-associated HIV-1 DNA in HIV-1-infected children initiating antiretroviral therapy.

OBJECTIVES AND METHODS: To investigate the relationship between cell-associated HIV-1 dynamics and recent thymic T-cell emigrants, HIV-1 DNA and T-cell receptor rearrangement excision circles (TREC, a marker of recent thymic emigrants) were measured in peripheral blood mononuclear cells in 181 samples from 33 HIV-1-infected children followed for 96 weeks after antiretroviral therapy (ART) initiation. RESULTS: At baseline, HIV-1 DNA was higher in children with higher TREC (P=0.02) and was not related to age, CD4 or HIV-1 RNA in multivariate analyses (P>0.3). Overall, TREC increased and HIV-1 DNA decreased significantly after ART initiation, with faster HIV-1 DNA declines in children with higher baseline TREC (P=0.009). The greatest decreases in HIV-1 DNA occurred in children with the smallest increases in TREC levels during ART (P=0.002). However, this inverse relationship between changes in HIV-1 DNA and TREC tended to vary according to the phase of HIV-1 RNA decline (P=0.13); for the same increase in TREC, HIV-1 DNA decline was much smaller during persistent or transient viraemia compared with stable HIV-1 RNA suppression. CONCLUSIONS: Overall, these findings indicate that TREC levels predict HIV-1 DNA response to ART and suggest that immune repopulation by thymic emigrants adversely affects HIV-1 DNA decline in the absence of persistent viral suppression, possibly by providing a cellular source for viral infection and replication.

Adolescent↗
PubMed2004

Human milk oligosaccharides reduce platelet-neutrophil complex formation leading to a decrease in neutrophil beta 2 integrin expression.

Human milk is thought by many authorities to be preferable to formula as a source of nutrients for infants. Some of the benefits may stem from its high concentration of unbound oligosaccharides (5-10 g/L). These sugars have structural similarities to selectin ligands, known to mediate important cell-cell interactions in the immune system. Platelet-neutrophil complexes (PNC) exist in healthy individuals but have been implicated in disease states. Formation of these complexes requires selectins and as such, could be influenced by human milk oligosaccharides (HMO). Here, we investigate this possibility by examining the effect of HMO on the formation of PNC and activation of associated neutrophils. We collected blood from 10 healthy volunteers, activated platelets with adenosine 5'-diphosphate, and added HMO, oligosaccharide standards, or phosphate-buffered saline as a control. We determined the influence of HMO on PNC formation and adjacent neutrophil activation with fluorescein-activated cell sorter analysis after labeling with antibodies for the platelet marker CD42a and the neutrophil activation marker CD11b. Within physiologically achievable concentrations (6.25-125 microg/mL), an acidic HMO fraction reduced PNC formation up to 20%, which was similar to the effect seen with high concentrations of sialyl-Lewis x. Associated neutrophils showed a dose-dependent decrease in beta 2 integrin expression, up to 30%, at high but physiological concentrations. The neutral HMO fraction had no effect. These results support the hypothesis that acidic HMO serve as anti-inflammatory components of human milk and thus, contribute to the lower incidence of inflammatory diseases such as necrotizing enterocolitis in breast-fed versus formula-fed infants.

Adenosine Diphosphate↗
PubMed2004

Targeted gene delivery to human airway epithelial cells with synthetic vectors incorporating novel targeting peptides selected by phage display.

Human airway epithelial cell targeting peptides were identified by biopanning on 1HAEo-cells, a well characterised epithelial cell line. Bound phage were recovered after three rounds of binding, high stringency washing and elution, leading to the production of an enriched phage peptide population. DNA sequencing of 56 clones revealed 14 unique sequences. Subsequent binding analysis revealed that 13 of these peptides bound 1HAEo-cells with high affinity. Three peptides, SERSMNF, YGLPHKF and PSGAARA were represented at high frequency. Three clearly defined families of peptide were identified on the basis of sequence motifs including (R/K)SM, L(P/Q)HK and PSG(A/T)ARA. Two peptides, LPHKSMP and LQHKSMP contained two motifs. Further detailed sequence analysis by comparison of peptide sequences with the SWISSPROT protein database revealed that some of the peptides closely resembled the cell binding proteins of viral and bacterial pathogens including Herpes Simplex Virus, rotavirus, Mycoplasma pneumoniae and rhinovirus, the latter two being respiratory pathogens, as well as peptide YGLPHKF having similarity to a protein of unknown function from the respiratory pathogen Legionella pneumophila. Peptides were incorporated into gene delivery formulations with the cationic lipid Lipofectin and plasmid DNA and shown to confer a high degree of transfection efficiency and specificity in 1HAEo-cells. Improved transfection efficiency and specificity was also observed in human endothelial cells, fibroblasts and keratinocytes. Therefore, on the basis of clone frequency after biopanning, cell binding affinity, peptide sequence conservation and pathogenic similarity, we have identified 3 novel peptide families and 5 specific peptides that have the potential for gene transfer to respiratory epithelium in vivo as well as providing useful in vitro transfection reagents for primary human cell types of scientific and commercial interest.

Amino Acid Sequence↗
PubMed2004

Resolution of orbitocerebral aspergillosis during combination treatment with voriconazole and amphotericin plus adjunctive cytokine therapy.

Orbitocerebral aspergillosis has a very high fatality rate and cure is unusual. We describe the successful management of a child with cereberal aspergillosis who had a dramatic response to therapy with a combination of liposomal amphotericin and voriconazole with adjunctive cytokine therapy during immunosuppresive chemotherapy for acute lymphoblastic leukaemia.

Amphotericin B↗
PubMed2004

Toll-like receptor 2 (TLR2) and TLR4 are present inside human dendritic cells, associated with microtubules and the Golgi apparatus but are not detectable on the cell surface: integrity of microtubules is required for interleukin-12 production in response to internalized bacteria.

The activation of dendritic cells (DCs) by microbes is mediated by pattern recognition receptors including the Toll-like receptors (TLR). Bacterial lipopolysaccharide acts via TLR4 whereas peptidoglycan and lipoprotein responses are mediated by TLR2. It is generally accepted that TLR binding to microbes occurs at the cell surface but this has not been directly demonstrated for human DCs. We show here that TLR2 and TLR4 are expressed inside DCs in an abundant tubulovesicular pattern with a focus of intense staining adjacent to the nucleus. In contrast, there was no detectable expression on the cell surface. TLR2 and TLR4 were readily found both intracellularly and on the surface of monocytes. They were shown to be closely associated with the Golgi complex and colocalized with alpha-tubulin, displaying a high focal concentration at the microtubule organizing centre. Alignment of TLR2 and TLR4 with microtubules was observed, suggesting that microtubules serve as transport tracks for TLR vesicles. Depolymerization of the microtubule network disrupted the intracellular expression of TLR2 and TLR4 and profoundly inhibited interleukin-12 (IL-12) production in response to Neisseria meningitidis but did not prevent phagocytosis. These data are consistent with the bacterial signalling through TLR2 and TLR4 required for IL-12 production occurring inside DCs after phagocytosis.

Cell Membrane↗
PubMed2004

Human dendritic cell activation by Neisseria meningitidis: phagocytosis depends on expression of lipooligosaccharide (LOS) by the bacteria and is required for optimal cytokine production.

Group B Neisseria meningitidis is a human pathogen, for which a universally effective vaccine is still not available. Immune responses to bacteria are initiated by dendritic cells (DC), which internalize and process bacterial antigens for presentation to T cells. We show here that optimal IL-12 and TNF-alpha production by human monocyte derived DC in response to killed serogroup B N. meningitidis depends on physical contact and internalization of the bacteria by DC. The majority of DC producing cytokines had internalized N. meningitidis while inhibition of bacterial internalization markedly impaired IL-12 and TNF-alpha, but not IL-6 production. Internalization of N. meningitidis was shown to depend on lipooligosaccharide (LOS) expressed by the bacteria with poor internalization of LOS deficient bacteria compared to wild-type bacteria. Restoration of LOS biosynthesis in a LOS regulatory strain also restored both internalization and cytokine production and was enhanced in the presence of LPS binding protein (LBP). These results suggest that DC phagocytosis depends on expression of LOS within the bacteria and that optimal cytokine production, particularly IL-12, requires internalization of the bacteria. These findings have important implications for designing vaccines that will induce protective immune responses to group B N. meningitidis.

Cells, Cultured↗
PubMed2003

A novel form of integrin dysfunction involving beta1, beta2, and beta3 integrins.

The adhesion receptors known as integrins perform key functions for hematopoietic cells. The platelet integrin alphaIIbbeta3 is critical in hemostasis, and the beta1 and beta2 integrins on leukocytes have many roles in cell-mediated immunity. Mutations in the beta2 subunit lead to integrin nonexpression and to an immune deficiency, leukocyte adhesion deficiency-1. Mutations in either the alpha or beta subunit of alphaIIbbeta3 usually lead to integrin nonexpression and a bleeding tendency termed Glanzmann thrombasthenia. Here we describe a unique patient with clinical features of both Glanzmann thrombasthenia and leukocyte adhesion deficiency-1. The patient has normal expression of beta1, beta2, and beta3 integrins, but all are dysfunctional. The key findings are that "inside-out" signaling pathways leading to integrin activation are defective and that this is associated with abnormal integrin clustering. The integrins themselves are intact and capable of function following extracellular stimulation. T cell motility is normal, as are the expression levels and electrophoretic characteristics of all cytoskeletal and signaling proteins tested, except PKC-alpha, which has enhanced expression in the patient's cells. To our knowledge, this is the first description of a dysfunction affecting three classes of integrins. We propose that it is caused by a lesion in an intracellular factor or signaling pathway essential for integrin activation in hematopoietic cells and results in lack of regulation of clustering, an essential component of integrin-mediated adhesion.

Blood Platelets↗
PubMed2002

Hyperzincaemia and hypercalprotectinaemia: a new disorder of zinc metabolism.

BACKGROUND: Calprotectin (complex of S100A8 and S100A9) is the major calcium and zinc-binding protein of phagocytes. We report a new syndrome with recurrent infections, inflammation, and hyperzincaemia associated with excessively high plasma concentrations of calprotectin. METHODS: We measured calprotectin in plasma and protein fractions by ELISA assay and zinc by atomic absorption spectrometry. Plasma proteins were fractionated by size exclusion chromatography and electrophoresis. Mass spectra of purified proteins were determined by MALDI-TOFMS. FINDINGS: We assessed five patients, two of whom are related. All patients had much the same biochemical findings of hyperzincaemia (77-200 micromol/L, reference range 11-18 micromol/L) and raised plasma calprotectin concentrations (1.4-6.5 g/L, reference range <1 mg/L). All patients presented with recurrent infections, hepatosplenomegaly, anaemia, and evidence of systemic inflammation. Three patients had cutaneous inflammation and three presented in infancy with severe growth failure. Size exclusion chromatography showed that zinc and calprotectin were associated in a broad fraction with molecular weight range 100-300 kDa. Analysis by electrophoresis and mass spectrometry showed that the patients' protein contained normal S100A8 and S100A9 subunits. INTERPRETATION: Dysregulation of zinc metabolism associated with accumulation in plasma of S100A8 and S100A9 defines a new disease, which encompasses a pathological role for dysregulation of two members of the large S100 protein family.

Adolescent↗
PubMed2002

Increased thymic output after initiation of antiretroviral therapy in human immunodeficiency virus type 1-infected children in the Paediatric European Network for Treatment of AIDS (PENTA) 5 Trial.

To investigate the thymic contribution to immune reconstitution during antiretroviral therapy (ART), T cell receptor gene rearrangement excision circles (TRECs) were measured in peripheral blood mononuclear cells (PBMC) and CD4 cells from 33 human immunodeficiency virus (HIV) type 1-infected children monitored for 96 weeks after ART initiation. Baseline TREC levels were associated positively with baseline CD4 cell percentage and inversely with age and HIV-1 RNA load. During therapy, TREC level changes in PBMC and CD4 cells were fairly comparable. TREC level changes were inversely related to baseline CD4 cell percentage and positively associated with CD4 cell percentage increases, the main source being naive CD4 cells. TREC changes were independent of age and baseline HIV-1 RNA load; however, HIV-1 suppression was independently associated with smaller TREC changes. Thymic output appears to be the main source of CD4 cell repopulation in children receiving ART. Recovery of thymic function is independent of age and influenced by the status of peripheral CD4 cell depletion and HIV-1 suppression.

Adolescent↗
PubMed2002

Prevention of inflammation-induced endothelial dysfunction: a novel vasculo-protective action of aspirin.

BACKGROUND: Inflammation and infection may initiate and promote atherosclerosis or its complications by adverse effects on the vascular endothelium. The mechanisms by which aspirin reduces cardiovascular risk might involve anti-inflammatory actions or direct effects on the endothelium in addition to its antiplatelet action. We investigated the role of aspirin in modulating endothelial dysfunction induced by an experimental inflammatory stimulus. METHODS AND RESULTS: An inflammatory response was generated in healthy volunteers by Salmonella typhi vaccination. Venous occlusion plethysmography was used to assess resistance vessel responses (16 hours before and 8 hours after vaccination) to the endothelium-dependent dilator bradykinin (BK) and the endothelium-independent dilator glyceryl-trinitrate (GTN). Twelve subjects were randomized to receive either aspirin 1.2 g orally or placebo 2 hours before vaccination. After vaccination alone there was suppression of the response to BK in the placebo group (P=0.01), with no change in response to GTN. In the aspirin group there was no change in the response to either BK or GTN after vaccination. Aspirin treatment prevented vaccine-induced elevation of interleukin-1 receptor antagonist but enhanced the generation of tumor necrosis factor-alpha compared with placebo. In an additional 5 individuals, local intrabrachial aspirin (10 mg/min for 15 minutes) failed to restore responses to BK after vaccination. CONCLUSIONS: Experimental inflammation produces endothelial dysfunction, which can be prevented by pretreatment with aspirin. Locally administered aspirin does not reverse vaccine-induced endothelial dysfunction once established. The protective effects of aspirin on inflammation-induced endothelial dysfunction may be through modulation of the cytokine cascade.

Administration, Oral↗
PubMedDate not supplied

Evaluation of a porcine model for pulmonary gene transfer using a novel synthetic vector.

BACKGROUND: The pig lung, given its gross anatomical, histological and physiological similarities to the human lung, may be useful as a large animal model, in addition to rodents, in which to assess the potential of vectors for pulmonary airway gene transfer. The aim of this study was to assess the utility of the pig lung as a model of gene transfer to the human lung with a synthetic vector system. METHODS: The LID vector system consists of a complex of lipofectin (L), integrin-binding peptide (I) and plasmid DNA (D). LID complexes containing a beta-galactosidase reporter gene under a CMV promoter or a control plasmid at1 mg/3 ml PBS, or 3 ml buffer, was administered to the right lower lobe of the pig lung through a bronchoscope. Pigs were culled at 48 h and lung sections prepared for immunohistochemical and histological analysis. Bronchoalveolar lavage fluid was collected and analysed for TNF-alpha by ELISA. RESULTS: Immunohistochemical staining for the beta-galactosidase reporter gene indicated high efficiency of gene transfer by the LID vector to pig bronchial epithelium with 46% of large bronchi staining positively. There was no evidence for vector-specific inflammation assessed by leukocytosis and cytokine production. CONCLUSIONS: This study demonstrates the use of the pig for studies of gene transfer in the lung and confirms in a second species the potential of the LID vector for gene therapy of pulmonary diseases such as cystic fibrosis.

Animals↗