Silke Schüle

PKCδ-induced PU.1 phosphorylation promotes hematopoietic stem cell differentiation to dendritic cells.

Human CD34+ hematopoietic stem cells (HSCs) exhibit the potential to differentiate into a variety of specialized blood cells. The distinct intracellular mechanisms that control cell fate and lineage commitment of these multipotent cells are not well defined. In this study, we investigate and modulate the signaling processes during HSC differentiation toward myeloid dendritic cells (mDCs). DC differentiation induced by the cytokines Granulocyte macrophage colony‐stimulating factor (GM‐CSF) and Interleukin‐4 (IL‐4) led to activation of the Extracellular‐signal‐regulated kinase (ERK), protein kinase C (PKC), and Janus kinase (JAK)/Signal Transducer and Activator of Transcription (STAT) but not the SAPK/c‐Jun NH2‐terminal kinase and p38 mitogen‐activated protein kinase signaling pathways. From the activated signaling pathways the PKC isoform δ was found to phosphorylate the transcription factor PU.1, which is described as one of the key factors for myeloid HSC differentiation. On molecular level, PKCδ regulated PU.1 activity by affecting its transactivation activity, whereas its DNA binding activity remained unaffected. This was accompanied by PKCδ‐induced phosphorylation of the PU.1 transactivation domain. Furthermore, treatment with PKC‐ and ERK1/2‐specific signaling inhibitors impaired both HSC differentiation toward mDCs as well as phosphorylation‐mediated transactivation activity of PU.1. Taken together, these results provide new insights into the molecular mechanisms promoting the differentiation process of HSCs toward mDCs and introduce the PKC isoform δ as critical mediator. STEM CELLS 2011;29:297–306

Interaction of Vpx and Apolipoprotein B mRNA-editing Catalytic Polypeptide 3 Family Member A (APOBEC3A) Correlates with Efficient Lentivirus Infection of Monocytes

The accessory protein Vpx is encoded by lentiviruses of the human immunodeficiency virus type 2 (HIV-2) and the simian immunodeficiency SIVsm/SIVmac lineage. It is packaged into virions and is indispensable in early steps of monocyte infection. HIV-1, which does not encode Vpx, is not able to infect human monocytes, but Vpx enables infection with HIV-1. The underlying mechanism is not completely understood. In this work, we focus on Vpx-mediated intracellular postentry events as counteraction of host cell proteins. We found that Vpx binds to apolipoprotein B mRNA-editing catalytic polypeptide 3 family member A (APOBEC3A; A3A), a member of the family of cytidine deaminases, present in monocytes. This interaction led to a reduction of the steady-state protein level of A3A. A single-point mutation in Vpx (H82A) abrogated binding to A3A and single-round infection of monocytes by HIV-1. Taken together, our data indicate that lentiviral Vpx counteracts A3A in human monocytes.

Restriction of HIV-1 replication in monocytes is abolished by Vpx of SIVsmmPBj

Background Human primary monocytes are refractory to infection with the human immunodeficiency virus 1 (HIV-1) or transduction with HIV-1-derived vectors. In contrast, efficient single round transduction of monocytes is mediated by vectors derived from simian immunodeficiency virus of sooty mangabeys (SIVsmmPBj), depending on the presence of the viral accessory protein Vpx. Methods and Findings Here we analyzed whether Vpx of SIVsmmPBj is sufficient for transduction of primary monocytes by HIV-1-derived vectors. To enable incorporation of PBj Vpx into HIV-1 vector particles, a HA-Vpr/Vpx fusion protein was generated. Supplementation of HIV-1 vector particles with this fusion protein was not sufficient to facilitate transduction of human monocytes. However, monocyte transduction with HIV-1-derived vectors was significantly enhanced after delivery of Vpx proteins by virus-like particles (VLPs) derived from SIVsmmPBj. Moreover, pre-incubation with Vpx-containing VLPs restored replication capacity of infectious HIV-1 in human monocytes. In monocytes of non-human primates, single-round transduction with HIV-1 vectors was enabled. Conclusion Vpx enhances transduction of primary human and even non-human monocytes with HIV-1-derived vectors, only if delivered in the background of SIVsmmPBj-derived virus-like particles. Thus, for accurate Vpx function the presence of SIVsmmPBj capsid proteins might be required. Vpx is essential to overcome a block of early infection steps in primary monocytes.

Comparative analysis of transduced primary human dendritic cells generated by the use of three different lentiviral vector systems.

Lentiviral gene transfer vectors are suitable for genetically modifying non-cycling primary human cells. In this study, we analyzed transduced human dendritic cells (DC) generated by the use of three different GFP-encoding lentiviral vectors, HIV-2 ROD A Δenv-GFP (ROD A), SIVsmm PBj ΔE EGFP (PBj), and SIVmac ΔE EGFP (SIVmac). CD14+ monocytes were isolated from buffy coat, transduced, and differentiated to immature and mature DC. Cytofluometric analysis of DC revealed high transduction efficiencies at MOI 1 for simian immunodeficiency virus (SIV)-derived vectors PBj and SIVmac ranging between 80–90 and 70–90%, respectively. In contrast, transduction with ROD A resulted only in approximately 30%-positive DC at the same MOI. Of note, none of the analyzed vectors affected expression of maturation and/or activation markers. Moreover, transduction with PBj or SIVmac did not induce significant cytokine responses whereas ROD A transduction stimulated weak interferon-alpha responses. SIVmac transduced DC showed normal phagocytosis of antigen and normal allo T cell stimulatory capacity when compared with untreated DC. Thus, the SIVmac lentiviral transduction vector is suitable for efficient genetic modification of human DC without affecting phenotype or function and thus qualifies this vector as a versatile tool for use in basic research.

Safety assessment of biolistic DNA vaccination.

DNA-based vector systems have been widely studied as new modalities for the prevention and treatment of human diseases. As for all other medicinal products, safety is an important aspect in the evaluation of such products. In this chapter we reflect on the basic safety issues which have been raised with respect to preventive and therapeutic DNA vaccines, including insertional mutagenesis in case of chromosomal integration, possible formation of anti-DNA antibodies, induction of autoimmune responses and/or immunological tolerance. In addition, local reactions at the site of administration and adverse effects resulting from plasmid DNA spread to nontarget tissues are discussed. Most importantly, however, the benefit-risk profile of a medicinal product is crucial for a decision on providing marketing authorization or not. A product has an acceptable benefit-risk profile if the benefits of the product outweigh its risks for the treated patient.

Functional HIV-2- and SIVsmmPBj- derived lentiviral vectors generated by a novel polymerase chain reaction-based approach

Lentiviral vectors allow stable gene transfer into nonreplicating cells and are increasingly used in clinical gene therapy approaches. Vectors derived from different origins can show distinct target cell transduction properties. Therefore, the construction of modern vector systems of different viral origin remains desirable. The generation of safe and efficient lentivirus‐derived transfer vectors by gradual enhancing cloning steps is a time‐consuming process that depends on the presence of suitable restriction sites. Multiple‐step cloning protocols also enhance the risk of acquisition of mutations or other genetic instabilities.

[The certification of advanced therapy medicinal products. A quality label for product development in small and medium-sized enterprises].

Advanced therapy medicinal products (ATMPs) are gene therapy, cell therapy, and tissue engineered products. To gain access to the market within the European Union, ATMPs must be authorized by the European Commission (EC). Especially for small and medium-sized enterprises (SMEs), the European centralized procedure of marketing authorization that is conducted by the European Medicines Agency (EMA) constitutes a major challenge, because SMEs often have little experience with regulatory procedures and many have limited financial possibilities. To tackle these challenges, a certification procedure exclusively for SMEs and their ATMP development was introduced by the EC. Independently from a marketing authorization application, development and/or production processes can be certified. An issued certificate demonstrates that the respective process meets the current regulatory and scientific requirements of the EMA, representing a valuable milestone for putative investors and licensees. This article highlights the background, the detailed procedure, the minimum requirements, as well as the costs of certification, while giving further noteworthy guidance for interested parties.ZusammenfassungArzneimittel für neuartige Therapien (Advanced Therapy Medicinal Products, ATMPs) sind Gentherapeutika, Zelltherapeutika und biotechnologisch bearbeitete Gewebeprodukte. Um ATMPs innerhalb der Europäischen Union (EU) auf den Markt bringen zu können, müssen diese zentralisiert durch die EU-Kommission zugelassen werden. Die zentrale Zulassung über die EMA stellt vor allem für kleine und mittlere Unternehmen (KMUs) eine große Herausforderung dar, da diese oft nur begrenzte Erfahrung mit den regulatorischen Vorgängen haben und über eine geringe Finanzkraft verfügen. Um dieser Problematik Rechnung zu tragen, wurde von der EU-Kommission ein von der zentralisierten Zulassung unabhängiges Zertifizierungsverfahren für KMUs und deren ATMP-Entwicklung eingeführt. Mit einem Zertifikat „ausgezeichnete“ Entwicklungs- und Produktionsprozesse stehen dafür, dass diese den gegenwärtigen regulatorischen und wissenschaftlichen Anforderungen der EMA entsprechen. Auf diese Weise wird die Attraktivität eines Unternehmens für potenzielle oder bestehende Investoren und Lizenznehmer gesteigert. Der vorliegende Beitrag beleuchtet die Hintergründe, den Verfahrensablauf, die Mindestanforderungen und die Kosten der Zertifizierung und gibt weitere bedenkenswerte Hinweise.AbstractAdvanced therapy medicinal products (ATMPs) are gene therapy, cell therapy, and tissue engineered products. To gain access to the market within the European Union, ATMPs must be authorized by the European Commission (EC). Especially for small and medium-sized enterprises (SMEs), the European centralized procedure of marketing authorization that is conducted by the European Medicines Agency (EMA) constitutes a major challenge, because SMEs often have little experience with regulatory procedures and many have limited financial possibilities. To tackle these challenges, a certification procedure exclusively for SMEs and their ATMP development was introduced by the EC. Independently from a marketing authorization application, development and/or production processes can be certified. An issued certificate demonstrates that the respective process meets the current regulatory and scientific requirements of the EMA, representing a valuable milestone for putative investors and licensees. This article highlights the background, the detailed procedure, the minimum requirements, as well as the costs of certification, while giving further noteworthy guidance for interested parties.

Tropism, intracerebral distribution, and transduction efficiency of HIV- and SIV-based lentiviral vectors after injection into the mouse brain: a qualitative and quantitative in vivo study

Lentiviruses are suitable to transfer potential therapeutic genes into non-replicating cells such as neurons, but systematic in vivo studies on transduction of neural cells within the complete brain are missing. We analysed the distribution of transduced cells with respect to brain structure, virus tropism, numbers of transduced neurons per brain, and influence of the Vpx or Vpr accessory proteins after injection of vectors based on SIVsmmPBj, HIV-2, and HIV-1 lentiviruses into the right striatum of the mouse brain. Transduced cells were found ipsilaterally around the injection canal, in corpus striatum and along corpus callosum, irrespective of the vector type. All vectors except HIV-2SEW transduced also single cells in the olfactory bulb, hippocampus, and cerebellum. Vector HIV-2SEW was the most neuron specific. However, vectors PBjSEW and HIV-1SEW transduced more neurons per brain (means 41,299 and 32,309) than HIV-2SEW (16,102). In the presence of Vpx/Vpr proteins, HIV-2SEW(Vpx) and HIV-1SEW(Vpr) showed higher overall transduction efficiencies (30,696 and 27,947 neurons per brain) than PBjSEW(Vpx) (6636). The distances of transduced cells from the injection canal did not differ among the viruses but correlated positively with the numbers of transduced neurons. The presence of Vpx/Vpr did not increase the numbers of transduced neurons. Parental virus type and the vector equipment seem to influence cellular tropism and transduction efficiency. Thus, precision of injection and choice of virus pseudotype are not sufficient when targeted lentiviral vector transduction of a defined brain cell population is required.

Die Zertifizierung neuartiger Therapien

Advanced therapy medicinal products (ATMPs) are gene therapy, cell therapy, and tissue engineered products. To gain access to the market within the European Union, ATMPs must be authorized by the European Commission (EC). Especially for small and medium-sized enterprises (SMEs), the European centralized procedure of marketing authorization that is conducted by the European Medicines Agency (EMA) constitutes a major challenge, because SMEs often have little experience with regulatory procedures and many have limited financial possibilities. To tackle these challenges, a certification procedure exclusively for SMEs and their ATMP development was introduced by the EC. Independently from a marketing authorization application, development and/or production processes can be certified. An issued certificate demonstrates that the respective process meets the current regulatory and scientific requirements of the EMA, representing a valuable milestone for putative investors and licensees. This article highlights the background, the detailed procedure, the minimum requirements, as well as the costs of certification, while giving further noteworthy guidance for interested parties.ZusammenfassungArzneimittel für neuartige Therapien (Advanced Therapy Medicinal Products, ATMPs) sind Gentherapeutika, Zelltherapeutika und biotechnologisch bearbeitete Gewebeprodukte. Um ATMPs innerhalb der Europäischen Union (EU) auf den Markt bringen zu können, müssen diese zentralisiert durch die EU-Kommission zugelassen werden. Die zentrale Zulassung über die EMA stellt vor allem für kleine und mittlere Unternehmen (KMUs) eine große Herausforderung dar, da diese oft nur begrenzte Erfahrung mit den regulatorischen Vorgängen haben und über eine geringe Finanzkraft verfügen. Um dieser Problematik Rechnung zu tragen, wurde von der EU-Kommission ein von der zentralisierten Zulassung unabhängiges Zertifizierungsverfahren für KMUs und deren ATMP-Entwicklung eingeführt. Mit einem Zertifikat „ausgezeichnete“ Entwicklungs- und Produktionsprozesse stehen dafür, dass diese den gegenwärtigen regulatorischen und wissenschaftlichen Anforderungen der EMA entsprechen. Auf diese Weise wird die Attraktivität eines Unternehmens für potenzielle oder bestehende Investoren und Lizenznehmer gesteigert. Der vorliegende Beitrag beleuchtet die Hintergründe, den Verfahrensablauf, die Mindestanforderungen und die Kosten der Zertifizierung und gibt weitere bedenkenswerte Hinweise.AbstractAdvanced therapy medicinal products (ATMPs) are gene therapy, cell therapy, and tissue engineered products. To gain access to the market within the European Union, ATMPs must be authorized by the European Commission (EC). Especially for small and medium-sized enterprises (SMEs), the European centralized procedure of marketing authorization that is conducted by the European Medicines Agency (EMA) constitutes a major challenge, because SMEs often have little experience with regulatory procedures and many have limited financial possibilities. To tackle these challenges, a certification procedure exclusively for SMEs and their ATMP development was introduced by the EC. Independently from a marketing authorization application, development and/or production processes can be certified. An issued certificate demonstrates that the respective process meets the current regulatory and scientific requirements of the EMA, representing a valuable milestone for putative investors and licensees. This article highlights the background, the detailed procedure, the minimum requirements, as well as the costs of certification, while giving further noteworthy guidance for interested parties.

The Human Genome Editing Race: Loosening Regulatory Standards for Commercial Advantage?

Medicinal products based on genome editing must undergo rigorous preclinical testing and are subject to regulatory oversight for proper risk assessment prior to first evaluation in humans. We give a European perspective on the regulatory expectations to translate genome editing to the clinic to ensure their timely progress to market.