Biomedical subjects

Lionel Berthoux

Publications and source records attributed to Lionel Berthoux.

10 recordsLinked to original sources

PubMed2006

G2 cell cycle arrest and cyclophilin A in lentiviral gene transfer.

Lentiviral vectors derived from the human immunodeficiency virus-1 (HIV-1) have a higher propensity to transduce nondividing cells compared to vectors based on oncoretroviruses. We report here that genistein, a previously known protein tyrosine kinase (PTK) inhibitor and G2 cell cycle arrest inducer, significantly enhanced lentiviral transduction in a dose-dependent manner. Increased transduction, as measured by vector expression, was seen in a variety of human cell lines, murine primary lymphocytes, and primary human CD34(+) peripheral blood progenitor cells as well. Increased vector expression was also associated with an increase in vector DNA copy number, as assessed by quantitative PCR. Genistein-mediated G2 cell cycle arrest, rather than PTK inhibition, appears to be the major factor responsible for increased gene transfer. Genistein also increases cyclophilin A (CypA) protein, a cellular protein important for efficient HIV-1 infection. While we show that CypA(-/-) Jurkat cells transduce poorly with lentiviral vectors, genistein does increase gene transfer in CypA-deficient cells. CypA and G2 cell cycle arrest appear to be two independent factors important for efficient lentiviral gene transfer. The role of genistein and other G2-arresting agents may be useful for improving the efficiency of lentiviral gene therapy.

Animals↗

PubMed2006

Cyclophilin A and TRIM5alpha independently regulate human immunodeficiency virus type 1 infectivity in human cells.

Cyclophilin A (CypA), a cytoplasmic, human immunodeficiency virus type 1 (HIV-1) CA-binding protein, acts after virion membrane fusion with human cells to increase HIV-1 infectivity. HIV-1 CA is similarly greeted by CypA soon after entry into rhesus macaque or African green monkey cells, where, paradoxically, the interaction decreases HIV-1 infectivity by facilitating TRIM5alpha-mediated restriction. These observations conjure a model in which CA recognition by the human TRIM5alpha orthologue is precluded by CypA. Consistent with the model, selection of a human cell line for decreased restriction of the TRIM5alpha-sensitive, N-tropic murine leukemia virus (N-MLV) rendered HIV-1 transduction of these cells independent of CypA. Additionally, HIV-1 virus-like particles (VLPs) saturate N-MLV restriction activity, particularly when the CA-CypA interaction is disrupted. Here the effects of CypA and TRIM5alpha on HIV-1 restriction were examined directly. RNA interference was used to show that endogenous human TRIM5alpha does indeed restrict HIV-1, but the magnitude of this antiviral activity was not altered by disruption of the CA-CypA interaction or by elimination of CypA protein. Conversely, the stimulatory effect of CypA on HIV-1 infectivity was completely independent of human TRIM5alpha. Together with previous reports, these data suggest that CypA protects HIV-1 from an unknown antiviral activity in human cells. Additionally, target cell permissivity increased after loading with heterologous VLPs, consistent with a common saturable target that is epistatic to both TRIM5alpha and the putative CypA-regulated restriction factor.

Antiviral Restriction Factors↗

PubMed2005

Cyclophilin A is required for TRIM5{alpha}-mediated resistance to HIV-1 in Old World monkey cells.

The peptidyl-prolyl isomerase cyclophilin A (CypA) embraces an exposed, proline-rich loop on HIV-1 capsid (CA) and renders reverse transcription complexes resistant to an antiviral activity in human cells. A CypA fusion with TRIM5 that is unique to New World owl monkeys also targets HIV-1 CA, but this interaction potently inhibits infection. A similar block to HIV-1 infection in Old World monkeys is attributable to the alpha isoform of the TRIM5 orthologue in these species. To determine whether HIV-1 restriction by Old World monkey TRIM5alpha is modulated by the CA-CypA interaction, RNA interference was used to disrupt CypA in cells from African green monkeys and rhesus macaques. HIV-1 infectivity increased in response to CypA knock-down to the same extent that it increased in response to TRIM5 knock-down. CypA knock-down eliminated the HIV-1 stimulatory effect of cyclosporin A (CsA), a competitive inhibitor of the CypA-CA interaction, or of CA mutants that block binding to CypA but caused no change in titer of retroviruses that don't interact with CypA. Simultaneous knock-down of both CypA and TRIM5 caused minimal additional increase in titer, suggesting that CypA inhibits HIV-1 replication in these cells because it is required for CA recognition by TRIM5alpha. Finally, CsA increased HIV-1 titer in otherwise nonrestrictive feline cells but only after these cells were transduced with Old World monkey TRIM5alpha. Thus, CypA is required for HIV-1 restriction by Old World monkey orthologues of TRIM5alpha.

Animals↗

PubMed2005

Disruption of human TRIM5alpha antiviral activity by nonhuman primate orthologues.

TRIM5 is a determinant of species-specific differences in susceptibility to infection by retroviruses bearing particular capsids. Human immunodeficiency virus type 1 (HIV-1) infection is blocked by the alpha isoform of macaque TRIM5 (TRIM5alpha(rh)) or by the product of the owl monkey TRIM5-cyclophilin A gene fusion (TRIMCyp). Human TRIM5alpha potently restricts specific strains of murine leukemia virus (N-MLV) but has only a modest effect on HIV-1. The amino termini of TRIM5 orthologues are highly conserved and possess a coiled-coil domain that promotes homomultimerization. Here we show that heterologous expression of TRIM5alpha(rh) or TRIMCyp in human cells interferes with the anti-N-MLV activity of endogenous human TRIM5alpha (TRIM5alpha(hu)). Deletion of the cyclophilin domain from TRIMCyp has no effect on heteromultimerization or colocalization with TRIM5alpha(hu) but prevents interference with anti-N-MLV activity. These data demonstrate that TRIM5 orthologues form heteromultimers and indicate that C-terminal extensions alter virus recognition by multimers of these proteins.

Animals↗

PubMed2005

Covalent modification of human immunodeficiency virus type 1 p6 by SUMO-1.

The p6 domain of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein mediates virion budding from infected cells via protein-protein contacts with the class E vacuolar protein sorting factors, Tsg101 and AIP1/ALIX. Interaction with Tsg101 is strengthened by covalent attachment of monovalent ubiquitin to HIV-1 p6. To identify additional host factors that bind to HIV-1 p6, a human cDNA library was screened in the yeast two-hybrid system. HIV-1 p6 was found to interact with small ubiquitin-like modifier 1 (SUMO-1) as well as the E2 SUMO-1 transfer enzyme, Ubc9. Interaction with p6 was also detected with Daxx, a cellular protein to which SUMO-1 is sometimes covalently attached. SUMO-1 was incorporated into HIV-1 virions where it was protected within the virion membrane from digestion by exogenous protease. Of the two lysine residues in p6, lysine 27 uniquely served as a site of covalent SUMO-1 attachment. As previously reported, though, HIV-1 bearing the p6-K27R mutation replicated just like the wild type. Overproduction of SUMO-1 in HIV-1 producer cells had no apparent effect on virion release or on virion protein or RNA content. Infectivity of the resulting virions, though, was decreased, with the defect occurring after membrane fusion, at the time of viral cDNA synthesis. HIV-1 bearing the p6-K27R mutation was insensitive to SUMO-1 overexpression, suggesting that covalent attachment of SUMO-1 to p6 is detrimental to HIV-1 replication.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Cyclophilin A retrotransposition into TRIM5 explains owl monkey resistance to HIV-1.

In Old World primates, TRIM5-alpha confers a potent block to human immunodeficiency virus type 1 (HIV-1) infection that acts after virus entry into cells. Cyclophilin A (CypA) binding to viral capsid protects HIV-1 from a similar activity in human cells. Among New World primates, only owl monkeys exhibit post-entry restriction of HIV-1 (ref. 1). Paradoxically, the barrier to HIV-1 in owl monkey cells is released by capsid mutants or drugs that disrupt capsid interaction with CypA. Here we show that knockdown of owl monkey CypA by RNA interference (RNAi) correlates with suppression of anti-HIV-1 activity. However, reintroduction of CypA protein to RNAi-treated cells did not restore antiviral activity. A search for additional RNAi targets unearthed TRIMCyp, an RNAi-responsive messenger RNA encoding a TRIM5-CypA fusion protein. TRIMCyp accounts for post-entry restriction of HIV-1 in owl monkeys and blocks HIV-1 infection when transferred to otherwise infectable human or rat cells. It seems that TRIMCyp arose after the divergence of New and Old World primates when a LINE-1 retrotransposon catalysed the insertion of a CypA complementary DNA into the TRIM5 locus. This is the first vertebrate example of a chimaeric gene generated by this mechanism of exon shuffling.

Amino Acid Sequence↗

PubMed2004

Lv1 inhibition of human immunodeficiency virus type 1 is counteracted by factors that stimulate synthesis or nuclear translocation of viral cDNA.

Human immunodeficiency virus type 1 (HIV-1) cDNA synthesis is inhibited in cells from some nonhuman primates by an activity called Lv1. Sensitivity to restriction by Lv1 maps to a region of the HIV-1 CA required for interaction with the cellular protein cyclophilin A. A similar antiviral activity in mammalian cells, Ref1, inhibits reverse transcription of murine leukemia virus (MLV), but only with viral strains bearing N-tropic CA. Disruption of the HIV-1 CA-cyclophilin A interaction inhibits Lv1 restriction in some cells and, paradoxically, seems to render HIV-1 sensitive to Ref1. Lv1 and Ref1 activities are overcome by high-titer infection and are saturable with nonreplicating, virus-like particles encoded by susceptible viruses. Two compounds that disrupt mitochondrial membrane potential, As(2)O(3) and m-Cl-CCP, reduce Ref1 activity. Here we show that these drugs, as well as a third compound with similar effects on mitochondria, PK11195, attenuate Lv1 activity in rhesus macaque and African green monkey cells. Effects of PK11195 and virus-like particles on HIV-1 infectivity in these cells were largely redundant, each associated with increased HIV-1 cDNA. Comparison of acutely infected macaque and human cells suggested that, in addition to effects on cDNA synthesis, Lv1 inhibits the accumulation of nuclear forms of HIV-1 cDNA. Disruption of the HIV-1 CA-cyclophilin A interaction caused a minimal increase in total viral cDNA but increased the proportion of viral cDNA in the nucleus. Consistent with a model in which Lv1 inhibits both synthesis and nuclear translocation of HIV-1 cDNA, complete suppression of macaque or African green monkey Lv1 was achieved by the additive effect of factors that stimulate both processes.

Active Transport, Cell Nucleus↗

PubMed2003

As(2)O(3) enhances retroviral reverse transcription and counteracts Ref1 antiviral activity.

Potent drugs such as cyclosporine have provided effective probes of signal transduction pathways and, as well, of human immunodeficiency virus type 1 (HIV-1) replication mechanisms. Recently, it was reported that As(2)O(3), a drug used to treat acute promyelocytic leukemia (PML), stimulates HIV-1 replication. We found that As(2)O(3) accelerates the kinetics of a spreading HIV-1 infection in human T cells and increases the number of cells bearing HIV-1 provirus after a single round of infection. The stimulatory effect occurred after membrane fusion and resulted in increased steady-state levels of newly synthesized viral cDNA. Stimulation was independent of HIV-1 env and most viral accessory genes, and As(2)O(3) had no detectable effects on viral expression postintegration or virion assembly. Murine leukemia virus (MLV) transduction was enhanced by As(2)O(3) to the same extent as HIV-1 transduction, but As(2)O(3) had no additional effect on Fv1 restriction. In contrast, As(2)O(3) largely overcame the specific block to N-tropic MLV reverse transcription posed by human Ref1. As(2)O(3) disrupts PML bodies, nuclear structures named for a major component, the PML protein. We observed no changes in PML bodies in response to HIV-1 infection. Experiments with PML-null target cells indicated that PML has no effect on HIV-1 infectivity and is dispensable for the stimulatory effect of As(2)O(3). As(2)O(3) caused cell death in uninfected cells at the same concentrations which stimulate HIV-1 replication. Among four additional apoptosis-inducing agents, a boost in HIV-1 infectivity was observed only with carbonyl cyanide m-chlorophenylhydrazone, a compound which, like As(2)O(3), disrupts the mitochondrial transmembrane potential. In summary, As(2)O(3) stimulates retroviral reverse transcription, perhaps via effects on mitochondria, and provides a useful tool for characterizing Ref1.

Animals↗

PubMed2003

Chondrocyte transplantation into articular cartilage defects with use of calcium alginate: the fate of the cells.

BACKGROUND: The fate of transplanted chondrocytes used to elicit the repair of osteochondral defects is unknown. The objective of this study was to examine the fate and the expression of cartilage-specific genes in chondrocytes when the chondrocyte phenotype was maintained preoperatively by alginate suspension culture, the cells were labeled with enhanced green fluorescent protein, and the chondrocytes in alginate were then implanted into full-thickness osteochondral defects in rabbits. METHODS: To determine the effect of alginate on rabbit chondrocytes in vitro, cells were grown in monolayer or in alginate suspension culture, and gene expression for aggrecan, type-I collagen, and type-II collagen was analyzed by reverse transcription-polymerase chain reaction. Cells were genetically labeled with the gene for enhanced green fluorescent protein, and the effect of transfer of the gene for enhanced green fluorescent protein on chondrocyte phenotype was assessed in vitro. Chondrocytes labeled with enhanced green fluorescent protein that were embedded in alginate were implanted into osteochondral defects in rabbit knees, either immediately after creation of the defects or after the cells had been preconditioned in alginate suspension culture for two weeks. The repair tissue within the osteochondral defects was assessed at one to four weeks. Cells labeled with enhanced green fluorescent protein were quantified by confocal microscopy, and the repair tissue was examined histologically with safranin O. RESULTS: Gene expression by chondrocytes demonstrated a selective upregulation of cartilage-specific genes in alginate suspension culture. This effect was less pronounced in cells that were transduced with enhanced green fluorescent protein. Chondrocytes transplanted in vivo were detected in the repair tissue for the entire period of observation with diminishing cell density over time. At one week, the cell density of the transplanted chondrocytes was 100% of the initial density; at two and three weeks, the cell density was 70%; and, after four weeks, the cell density had decreased to 15%. Safranin-O staining of histological sections indicated cartilage-specific matrix production in vitro and in vivo. Integration of transplanted cells into the host repair tissue was not observed. The two-week period of preconditioning in alginate suspension culture had no apparent influence on the temporal fate of the cells or the histological appearance of the repair tissue. CONCLUSIONS AND CLINICAL RELEVANCE: Alginate promotes expression of cartilage-specific genes and allows delivery of chondrocytes into osteochondral defects. Transgenic chondrocytes labeled with enhanced green fluorescent protein are detectable in the defect, but they do not appear to form repair tissue and they decrease in number with time. In view of the clinical application of cell-based cartilage repair, understanding the fate of transplanted cells becomes increasingly relevant. Transgenic chondrocytes are an effective tool to study the role of transplanted chondrocytes in articular cartilage repair.

Alginates↗

PubMedDate not supplied

Tracing transduced cells in osteochondral defects.

In this study the authors explored the feasibility of using transduced cells for gene therapy to induce healing of osteochondral defects. Both a mouse mesenchymal cell line and mixed rabbit adherent stromal cells were transduced with either liposomal transfection or retroviral transduction using a traceable gene. Transduction efficiency was more than 95% with the retroviral construct and expression was maintained for over 6 months of passage. The liposomal transfection led to a transient expression with an efficiency of 50%. The expression of osteochondral genes was diminished but preserved after transduction in vitro. Transduced rabbit cells were transplanted into osteochondral defects in rabbit femoral condyles. Cells transplanted in vivo could be detected for 4 weeks in the repair tissue. The authors' data demonstrate that mesenchymal cells from bone marrow, stably transduced with a traceable gene product, retain the bone and cartilage phenotype and can be followed in vivo after transplantation into cartilage defects.

Animals↗