| Retroviral vectors -> Monitor Keywords |
|
|
 
Retroviral vectorsRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Whole Live Micro-organism, Cell, Or Virus Containing, Genetically Modified Micro-organism, Cell, Or Virus (e.g., Transformed, Fused, Hybrid, Etc.)Retroviral vectors description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070104690, Retroviral vectors. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This invention relates to retroviral vector production systems and to retroviral vector particles produced by the systems. In particular, it relates to systems and vector particles from which certain retroviral auxiliary factors are absent. The invention also relates to uses of retroviral vectors, in particular for gene therapy. [0002] Retroviral vectors have been the vehicle of choice for clinical gene transfer-because of their efficacy, safety, and stable long-term gene expression. According to the United States National Institutes of Health RAC report issued in September 1996 (Ross et al., 1996), 76 out of 107 trials reviewed by the NIH were based on vector systems derived from the murine leukaemia virus (MLV). [0003] One major drawback of these vectors is their inability to infect non-proliferating cells such as neurons, macrophages and haematopoeitic stem cells. These cells are important targets for gene therapy. [0004] Human immunodeficiency-virus type 1 (HIV-1) belongs to a sub-family within the retroviruses, the lentiviruses and in common with other members of this family HIV can infect quiescent cells. This makes lentiviruses attractive vectors for gene therapy. [0005] The viral determinants for HIV-1 infection of non-dividing cells are thought to reside in the p17 matrix protein (MA) and vpr (Gallay et al., 1996). MA has karyophilic properties conferred by a conserved stretch of basic residues, which constitute a nuclear localization signal (NLS) (Bukrinsky et al., 1993). Vpr also contains a distinct NLS (Mahalingam et al., 1995). MA-NLS mutant viruses fail to rep licate efficiently in macrophages in the absence of a functional vpr gene (Heinzinger et al., 1994). These data have been interpreted to mean that vpr as well as MA function as karyophilic determinants of HIV-1. In the absence of vpr the transduction efficiency of monocyte-derived macrophages decreases by over 50%, in the presence of functional MA. (Naldini et al., 1996). [0006] Following work reported in Lever et al., 1989 which showed the sequences required for packaging of HIV-1, there has been much interest in the development of an HIV-1 based gene therapy vector. Transfer of foreign genes into a human T-ell line by a replication defective HIV-1 based vector was demonstrated by Poznanski et al (Poznansky et al., 1991). Other groups have designed HIV-1 based vectors that are tat-inducible (Buchschacher, Jr. and Panganiban, 1992) or that use heterologous promoters (Shimada et al., 1991). However, the viral titers obtained with these vectors was low (at most 10.sup.3 infectious particles per ml), and it was not clear whether the vector system could guarantee the production of helper virus-free vectors. More recently, new efforts to produce helper virus-free vectors have been based on three-plasmid cotransfections (Richardson et al., 1995). HIV vectors can be pseudotyped with Vesicular Stomatitis Virus glycoprotein (VSV-G) and these particles retain infectivity after concentration by ultracentrifugation (Akkina et al., 1996). Pseudotyping With VSV-G confers a broader host range and eliminates the chances of recombination to produce wild type HIV envelope. In vivo transduction of non-dividing neuronal cells has been demonstrated with VSV-G pseudotyping of HIV-1 in a three-plasmid cotransfection system (Naldini et al., 1996 and Naldini et al., 1996a). [0007] HIV-1 contains nine genes, three of which: gag, pol and env are found in all retroviruses. These are the structural genes. The other six: vif, vpu, vpr, nef, tat and rev are referred to as auxiliary genes. Other retroviruses have different sets of auxiliary genes in their wild type genomes. Some of the auxiliary genes of other retroviruses are analogous to those of HIV-1, although they may not always have been given the same names in the literature. Analogous auxiliary genes have homology in their nucleotide sequences and perform the same or similar functions. HIV-2 and SIV strains generally contain env, vpr, vif, tat, and nef genes analogous to those of HIV-1. HIV-2 and some strains of SIV also contain vpx which, in some SIV strains lacking vpr can be considered analogous to vpr. Lentiviruses other than HIV-1 also contain auxiliary genes which are not analogous to the HIV-1 auxiliary genes. Retrovirus auxiliary genes are reviewed for example by Tomonaga and Mikami (1996) and by Joag et al. in Fields Virology, Vol 2. [0008] To date all vector systems based on HIV contain some or all of the HIV auxiliary genes. Rev acts as an RNA export protein and tat is a major transactivator of the proviral long terminal repeat (LTR). The auxiliary genes play a crucial role in viral replication and pathogenesis. The auxiliary genes have not been fully characterized nor their function defined. [0009] However some of the auxiliary genes are thought to be involved in the pathogenesis of HIV-1. Tat has been implicated in the development of Kaposi's sarcoma (Barillari et al., 1993; Ensoli et al., 1990). HIV vpr has been shown to cause cell arrest and apoptosis and this has been proposed: to be the cause of T-Cell dysfunction seen in AIDS patients (Jowett et al., 1995). Also extracellular Vpr present in peripheral blood has been suggested: to contribute to tissue-specific pathologies associated with HIV infection since Vpr induces cell proliferation and differentiation (Levy et al, 1993 and Levy et al, 1995). [0010] Since the roles of the auxiliary genes are not clear and they probably play a major role in pathogenesis their removal from HIV-1 vector production systems is desirable, provided that sufficiently high retrovirus vector titer and ability to transduce non-proliferating cells can be retained. [0011] Naldini et al's data shows that the presence or absence of vpu has no effect on the vector particle titer. That is, a packaging system they used produced a titer of 4.times.10.sup.5 when pseudotyped with VSV-G and this system was env and vpu negative. In another system which was only env negative they obtained the same titer (Naldini et al. 1996 and Naldini et al. 1996a). However, as already discussed another system of Naldini et al which was vpr negative as well as vpu negative gave a transduction efficiency which was decreased by 50% compared to a vpr positive system. [0012] We have now discovered that leaving some or all of the auxiliary genes out of retrovirus vector production systems does not significantly compromise vector particle titers or the ability of the vector particles to transduce non-dividing cells. [0013] The invention therefore provides in one aspect a retroviral vector production system for producing lentivirus-based, replication defective vector particles for gene therapy, said vector particles capable of infecting and transducing non-dividing mammalian target cells, which system comprises a set of nucleic acid sequences encoding the components of the vector, wherein one or more functional genes chosen from the HIV-1 auxiliary genes vpr, vif, tat and nef or from the analogous auxiliary genes of other lentiviruses, which auxiliary genes are normally present in the lentivirus on which the vector particles are based, is or are absent from the system. The functional vpu gene may also be absent, with the proviso that when the production system is for an HIV-1 based vector and vpr and vpu are both absent, so also is one of the other auxiliary genes. [0014] In another aspect, the invention provides retroviral vector particles produced by a retroviral vector particle production system described herein. [0015] In yet another aspect, the invention provides a DNA construct for use in a retroviral vector production system described herein, said DNA construct encoding a packagable RNA vector genome for a retroviral vector particle and operably linked to a promoter, wherein all of the functional retroviral auxiliary genes are absent from the construct, other than rev which is optionally present. The DNA construct may be provided as part of a set of DNA constructs also encoding some or all of the structural components of the vector particles. [0016] In further aspects, the invention provides the use of retroviral vector particles as described herein, for gene therapy and in the preparation of a medicament for gene therapy; and a method of performing gene therapy on a target cell which method comprises infecting and transducing the target cell using a retroviral vector particle as described herein. The invention further provides transduced target cells resulting from these uses and methods. The invention thus provides a gene delivery system for use in medicine. [0017] The expression "lentivirus-based" means that the vector particles are derived from a lentivirus. The genome of the vector particle comprises components from the lentivirus as a backbone. The vector particle as a whole contains essential vector components compatible with the RNA genome, including reverse transcription and integration systems. Usually these will include the gag and pol proteins derived from the lentivirus. [0018] Being derived from a lentivirus, the retroviral vector particles are capable of infecting and transducing non-dividing cells. Thus, the vector particles are able to deliver a selected gene or genes such as therapeutically active genes, to the genome of a target cell. During the infection process, lentiviruses form a pre-integration complex in the target cell cytoplasm containing integrase, core proteins and proviral DNA. The complex is able to pass across the nuclear membrane of the target cell, by means of signal sequences in the proteins. Non-lentiviral retroviruses either lack the proteins or have the proteins but without the appropriate signal sequences. [0019] Examples of lentiviruses are HIV-1 and HIV-2, SIV, FIV, BLV, EIAV, CEV and visna virus. Of these, HIV and SIV are presently best understood. However, a non-immunodeficiency virus may be preferred for use in gene therapy because the immunodeficiency viruses inevitably bring with them safety considerations and prejudices. [0020] The absence of functional auxiliary genes from the retroviral vector production system means that those functional genes will also be absent from retroviral vector particles produced by the system. Also, any auxiliary proteins that would otherwise be encoded by those genes and incorporated into the vector particles, will be absent from the vector particles. In known retroviral vector production systems, the auxiliary genes may be present as part of the vector genome-encoding DNA, or together with the packaging components. The location of an auxiliary gene in a vector production system depends in part on its relationship with other retroviral components. For example, vif is often part of a gag-pol packaging cassette in a packaging cell. Thus, to remove a functional auxiliary gene for the purposes of the invention may involve its removal from the packaging components, or from the vector genome, or perhaps both. [0021] To remove a functional auxiliary gene may not require removal of the gene in its entirety. Usually removal of part of the gene, or disruption of the gene in some other way will be sufficient. The absence of a functional auxiliary gene is understood herein to mean that the gene is not present in a form in which it is capable of encoding the functional auxiliary protein. [0022] In a preferred system according to the invention, functional vpr and tat genes or analogous genes normally present in the lentivirus on which the vector particles are based are both absent. These two auxiliary genes are associated with characteristics of lentiviruses which are particularly undesirable for a gene therapy vector. However, other than by the proviso given above, the invention is not limited with regard to the combination of auxiliary genes that are absent. In a system according to the invention for producing HIV-1-base vector particles, any combination of three, or more preferably four, of the genes may be absent in their functional form. Most preferably, all five of the auxiliary genes vpr, vif, tat, nef, and vpu are absent in their functional form. Similarly, for systems concerned Swath other lentiviruses, it is most preferable that all of the auxiliary genes are absent in their functional form (except rev which is preferably present unless replaced by a system analogous to the rev/RRE system). [0023] In order to ensure efficient export of RNA transcripts of the vector genome from the nucleus to the cytoplasm, it is preferable to include functional rev and rev response element (RRE) sequences in the vector genome, or to include alternative sequences in the genome which perform the same function as the rev/RRE system. For example, a functional analogue of the rev/RRE system is found in Mason Pfizer monkey virus. This is known as CTE and consists of an RRE-type sequence in the genome which is believed to interact with a factor in the infected cell. The cellular factor can be thought of as a rev analogue. Thus, CTE may be used as an alternative to the rev/RRE system. [0024] As will be evident, in order to function as a vector the retroviral vector particles described herein will need to have a reverse transcription system (compatible reverse transcription and primer binding sites) and an integration system (compatible integrase and integration sites) allowing conversion to the provirus and integration of the double-stranded DNA into the target cell genome. Additionally, the vector genome will need to contain a packaging signal. These systems and signals will generally be derived from the lentivirus on which the vector is based. It will be evident that although the vector according to the invention is based on a lentivirus, the elements of the lentivirus incorporated into the vector may be genetically or otherwise altered versions of the elements in the wild type lentivirus. Alterations may be achieved by manipulating either the RNA genome or other components of the retroviral vector particle production system. For example, portions of the lentivirus genome not required for the vector can be excluded. Also, the vector production system can employ substitutes e.g. for the lentivirus env gene, to give the vector a different target cell range (this is known as pseudotyping). Continue reading about Retroviral vectors... Full patent description for Retroviral vectors Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Retroviral vectors patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Retroviral vectors or other areas of interest. ### Previous Patent Application: Ocular gene therapy Next Patent Application: Small interfering rna mediated transcriptional gene silencing in mammalian cells Industry Class: Drug, bio-affecting and body treating compositions ### FreshPatents.com Support Thank you for viewing the Retroviral vectors patent info. IP-related news and info Results in 0.19097 seconds Other interesting Feshpatents.com categories: Qualcomm , Schering-Plough , Schlumberger , Seagate , Siemens , Texas Instruments , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
