CA2199131C - Retroviral vector hybrids and the use thereof for gene transfer - Google Patents

Abstract

The disclosure relates to replication defective retroviral vector hybrids characterized by the fact that they contain: ( a) in the leader region as U5 region and/or tRNA primer binding site, the U5 region and/or tRNA
primer binding site of MESV; and (b) as U3 and R
regions in 3'-LTR, the U3 and R regions from a Friend murine leukaemia virus (F-MuLV). The proposed hybrids are particularly suitable for effective gene transfer in haematopoietic stem cells.

Description

Retroviral vector hybrids and the use thereof for gene transfer The invention concerns retroviral vector hybrids and their use for gene transfer in particular for gene transfer into haematopoietic stem cells (ES).
Retroviral vectors with replication defects are at present a standard in gene transfer and gene therapy applications on cells of the human blood-forming system (A. D. Miller ( 1992 ) (1) , R. C. Mulligan ( 1993 ) (2) , R.
Vile and S.J. Russell (1994) (3)). Their main advantages are:
- the infection leads to a stable integration of the vector and of the DNA sequences transferred by it into the host genome of mitotically active cells - the number of integrations into the host genome can be controlled via the infection conditions - the safety aspects of retroviral gene transfer are well researched; complications have so far not occurred in numerous applications on humans.
The most frequently cited advantage of retroviral vectors, their high gene transfer efficiency, only partly applies to applications on the blood-forming system. only Late maturing blood-forming precursor cells can preferably be infected with conventional vectors based on the Moloney murine sarcoma virus (MoMuSV); 30-95 ~ of the precursor cells transducecl with these vectors exhibit either no or an inadequate expression of the transferred genes due to primary silencing mechanisms (4); moreover after a longer residence period in vivo the retrovirally controlled gene expression is weakened in a high percentage of the initially expressing cells up to the point of non-function due to secondary silencing (Palmer et al. (1991) (5), Brenner et al. (1993) (6)).
It has been demonstrated that also in embryonic cells such as embryonic carcinoma cells (myeloid (non-lymphatic) derivatives of haematopoietic stem cells) the viruses are indeed integrated but the expression of the integrated provirus is blocked.
Mutations and derivatives of MoMuSV are known from Stocking et al. (1993) (21) which can be used to improve the retroviral gene expression in such cells. Such hybrids are obtained by point mutations in the LTRs especially in the U3 region. For example the binding of the ECF-1 repressor can be reduced by a point mutation at -345 of MoMuLV. A point mutation which creates a binding site for SP-1 (e.g. point mutation at -166 (S.
McKnight and R. Tijan (1986) (16)) is equally advantageous. It is furthermore advantageous to also introduce mutations outside the LTR regions. It has been shown that an 18 by region which adjoins the 5'-LTR
directly downstream is a negative regulation element (NRE; silencer binding element). Point mutations in this element enable the retroviral transcription to be improved (murine embryonic stem cell virus , MESV; M.
Grez et al (1990) (22) ) .
The object of the invention is to provide retroviral vector hybrids which can be used to further improve retroviral gene expression especially in haematopoietic stem cells and their myeloid (non-lymphatic) derivatives.
The invention concerns retroviral vector hybrids which are characterized in that they a) contain the U5 region and/or tRNA primer binding site of MESV and/or MoMuSV in the leader region as a U5 region and/or tRNA primer binding site and b) contain the U3 and R regions from a Friend murine leukemia virus (F-MuLV) as U3 and R regions in 3'-LTR.
The vector hybrids according to the invention preferably contain the leader region of MESV as the leader region.
In a further embodiment of the invention the U5 region and/or preferably the tRNA primer binding site can also be derived from MoMuSV.
The vector hybrids according to the invention also preferably contain the LTR from a Friend murine leukemia virus (F-MuLV) as the 3'-LTR and thus also the U5 region from F-MuLV in addition to the U3 and R regions from MoMuLV and MESV.
The vector hybrids can be replication-defective as well as replication-competent.
A replication-defective vector is understood as a vector which contains no retroviral gene functions (gag, env, pol) and therefore cannot independently form virus particles. However, the vector usually contains a packaging function (psi). In order to form infectious retroviral particles a packaging cell line which contains the gene functions gag, env and pol in a stable .
-~-~ 199 1~ 1' form (as an episome or integrated into the genome) is transfected with the replication-defective DNA vector according to the invention. RNA transcripts are formed which are packaged into virus particles due to the gag and env functions. These virus particles are replication-deficient because the RNA genome contained in them does not carry retroviral gene functions.
Retroviral vector hybrids capable of replication additionally contain the gene regions gag, pol and env.
These gene regions can be derived from any desired retroviruses. Only the selection of the env region depends on the cell to be infected. Such methods are however, known to a person skilled in the art. In this manner it is possible to produce ecotropic, xenotropic, amphotropic or polytropic retroviruses capable of replication.
More details of this and on the production of vectors, virus particles and helper cells are described in M.
Kriegler, Gene Transfer and Expression, A Laboratory Manual, W.H. Freeman & Co., New York (1990), 47-55 and 161-164 (31). This publication is a subject matter of the disclosure of the present application.
Silencer proteins.within the sense of the invention are understood as cellular (e. g. derived from a mutated cell) nuclear proteins, for example from haematopoietic stem cells, which preferably bind to the first 450 by preferably the first 18 bp, of MoMuI~V and MoMuSV which immediately follow the 5°-LTR and inhibit the retroviral transcription by interaction with cis regulatory sequences of the provirus.

~ =~2199'6~ 1 The leader region of MESV is understoqd as the sum of sequences from the short direct terminal repeat (R), the U5 region and the sequence immediately adjoining the 5'-LTR of MESV which contains the tRNA primer binding site as well as the packaging region (~). At a maximum the leader sequence can be composed of the complete sequence which is contained in the virus from R up to the translation start. However, it is preferable to use a truncated leader region which in addition to R and U5 is preferably composed of about the first 450 bases downstream of the end of the 5'-LTR region. It is also preferred that the U5 region and the tRNA primer binding site are derived exclusively or to a major extent from MESV and the other parts of the leader sequence are derived from MoMuLV or MoMuSV. A suitable MESV region is shown in the Figures (Fig. 1 - 5) from: KpnI (ca. 550) to Ball (ca. 729).
The leader region of MESV corresponds to the leader region of MoMuLV or MoMuSV (sequence of U3, U5 and R of MoMuLV and PCMV, see (22) and (23)) in which point mutations are inserted which reduce or prevent the binding of silencer proteins. Compared to MoMuLV and PCMV the leader region of MESV contains 5 point mutations in the 18 by region which directly adjoins the 5'-LTR (C. Stocking et al. (1993) (21)). This drastically reduces the inhibitory binding ability of nuclear proteins from the infected cells and correspondingly improves the expression of a gene contained in the vector hybrid (R. Petersen et al., Mol.
Cell Biol. 11 (1991) 1213-1221 (8)). Instead of these point mutations, other (at least one) point mutations in the leader region (preferably within the first 450 bases downstream from the end of the 5'-LTR region and particularly preferably in the 18 by region) are also ~1 suitable for reducing or preventing the inhibitory binding of silencer proteins e.g. to the leader region.
Thus in addition to the aforementioned sequence described in SEQ ID N0:1 a leader region of MESV within the sense of the invention is also understood as a sequence which essentially corresponds with this section of SEQ ID N0:1, contains a tRNA binding site and a psi function and is modified by point mutations in such a way that the inhibitory binding of silencer proteins from the cells which have been chosen for the transfection is reduced or prevented.
In order to check whether a point mutation is suitable for preventing the binding of silencer proteins to the leader region it is usual to construct a plasmid which contains an LTR, the leader region to be examined and an indicator gene which is preferably the CAT gene. The cells to be examined are transfected with this plasmid and the CAT activity is determined preferably after 48 hours (transient transfection). If the CAT activity is clearly present then the point mutation is suitable for preventing the binding of the silencer protein in these cells (P. Artelt et al. (1991) (32)).
Transient transfection experiments have shown that cis-regulatory sequences are located in the leader sequence of MoMuSV that have an inhibitory influence on the gene expression in particular in early multipotent myeloid cells (primary silencing). A substitution of this region by leader sequences of the murine embryonic stem cell virus [MESV (22)] completely abolishes the inhibitory effect in myeloid stem cells. The leader sequence of MESV was originally derived from the endogenous mouse retrovirus dl-587rev (23) and was introduced into MESV
in order to abolish the silencing of the MoMuSV leader ~-219~ ~3 ~

- 7 _ observed in embryonic stem cells (22). Mutations of the retroviral primer binding site (PBS) which is located immediately 3' of the 5'-LTR are decisive for the abolition of the silencing (22).
Retroviruses of the F-MuLV group are known to a person skilled in the art and are described for example iri D.
Linnemeyer et al. (I981) (7), J. Friel et al. (1990) (9) , S.P. Clark and T.W. Mak (1982) (10) , L. Wolff et al. (1985) (11), R.K. Bestwick et al. (1984) (12), W.
Koch et al. (1984) (13) and A. Adachi et al. (1984) (14). A review is given in W. Ostertag et al. (1987) (1s). The 3'-LTRs of malignant histiosarcoma virus (MHSV) (9) , SFFVp Lilly-Steeves (10) , SFFVa (11) , Rauscher SFFV (12), F-MuLV c157 (13) and Friend-mink cell focus forming virus (F-MCFV FrNx (14) , F-MCFV
pFM548 (13)) are preferably used.
According to the invention sequences of the genomic vector RNA are suitable as 3'-LTR sequences which have a high degree of sequence homology to the 3°-LTR regions of the aforementioned Friend virus family in the U3 region. The LTR sequence of SFFVp is described in SEQ ID
NO:1 (nucleotides 1707 - 2283).
The advantages according to the invention are exhibited in transient transfections of reporter gene constructs in numerous representative cell lines of humans and mice. It has surprisingly turned out that U3 sequences of mouse retroviruses of the Friend murine leukemia virus (F-MuLV) family in combination with leader sequences (preferably tRNA binding site) of MESV enable an especially efficient gene expression in myeloid stem and precursor cells. The increase of the gene expression _8_ with the vector hybrids according to the invention is more than a power of ten compared to MoMuSV. This applies to relatively late precursor cells of the granulocytes, macrophages and erythrocytes as well as to the early multipotent precursors and even stem cells of the myeloid system. The vector hybrids according to the invention enable an efficient gene expression especially in the case of immature multipotent myeloid cells in which MoMuSV-LTR exhibits a pronounced primary silencing. The activity is also high in the lymphatic system as well as in fibroblasts.
An early isolate of the polycythaemia-inducing spleen focus forming virus (SFFVp (7)), is particularly preferred whose LTR sequence is described in SEQ ID NO:1 (bp 2654-3230) as well as the malignant histiosarcoma virus (MHSV (9), LTR SEQ ID N0:4, by 170?-2324). In the U3 region of these viruses there is a high degree of sequence homology to other representatives of the Friend virus family such as SFFVp Lilly-Steeves (10), SFFVa (11), Rauscher SFFV (12), F-MuLV c157 (23) and Friend-minl~ cell focus forming virus [F-MCFV FrNx (14) , F-MCFV
pFM548 (Z3)]. These and similar Friend-related retroviruses have a similar expression pattern as SFFVp and MHSV due to the sequence homology of the U3 regions.
Mutations in the enhancer region of U3 [340 to 140 nucleotides on the 5' side of the transcription start (Z0)] are particularly advantageous for the pronounced increase compared to MoMuSV of the gene expression in myeloid stem and precursor cells by the vectors according to the invention. The partial duplication of the so-called direct repeat element in SFFVp (similar to F-MCFV FrNx) and MHSV is of importance. Binding sites for transcription factors may be located here which lead -2 199 1.~ 1 to an efficient gene expression in myeloid cells.
SFFVp and MHSV as well as Friend MCFV carry a binding site for the transcription factor Spl (16) directly 5' of the direct repeats. Sp1 is capable of multiple interactions with surrounding transcription factors which usually lead to a considerable increase in gene expression. In the case of the MoMuSV derivatives myeloproliferative sarcoma virus (MPSV (27), (18)) and PCC4-cell passaged MPSV (PCMV (19)) the occurrence of an Sp1 binding site in the U3 region is also necessary for the abolition of the silencing of the MoMuSV-LTR in embryonic stem cells (20) as well as probably also in blood stem cells (21). The Spl binding site of SFFVp, MHSV as well as Friend-MCF viruses may also have an analogous function.
In a further embodiment of the invention the retroviral vector hybrids can contain the U3 and R regions from MPSV as U3 and R regions in 3°-LTR. MPSV differs from MoMuSV and MoMuLV by point mutations in the LTR (21). In this case A(-381) is deleted and the following substitutions have been carried out CST, -345; TEA, -326; TEA; -249 and ABC, -166 (numbering according to (21)). In this case the retroviral vector hybrid contains the U5 region and tRNA primer binding site of MESV in the leader region as the U5 region and tRNA
primer binding site. It has turned out that such MPSV/MESV hybrid vectors (also called MPEV in the following) have considerable advantages compared to vectors based on MoMuLV and are of major importance for numerous applications in somatic gene therapy.
Any desired U3 and R regions can be used in 5'-LTR since after integration of the virus the U~ from the 3'~-LTR is copied in the target cell also at the 5°-LTR position after completion of the retroviral life cycle and drives the gene expression. U3 and R regions are derived for example from MoMuLV or MoMuSV derivatives such as for example MPSV, PCMV and MESV. 5'-LTRs from F-MuLV are also suitable as the 5'-LTR.
The vector hybrids according to the invention exhibit a high tissue-specific expression after retroviral transduction of myeloid stem and precursor cells. These vectors therefore have the potential to considerably increase the gene transfer efficiency in myeloid stem and precursor cells compared to MoMuSV vectors. The vectors according to the invention additionally have the potential to be considerably less subject to silencing processes in myeloid cells than MoMuSV vectors. The high and possibly even persistent gene expression of these vectors in myeloid cells can form the basis for the successful application of numerous gene transfer protocols on the blood-forming system of humans. The constructs described in the examples are constructed in such a way that the cDNAs transferred by the vector can be replaced without difficulty by other genes.
The tissue specificity of the expression is suitable for abolishing the primary silencing in the myeloid system observed in the case of conventional MoMuSV vectors.
This leads to a considerable increase in the functional gene transfer rates in myeloid cells. Since a high functional gene transfer rate is desired in most gene transfer/gene therapy applications on the myeloid system this is a generally usable advantage of the constructs according to the invention.

=~21991~ 1 The Friend virus-related U3 regions were also selected in the myeloid system of the mouse for persistency of the gene expression in vivo. Secondary silencing occurred with these vectors to a much lower extent than with MoMuSV vectors. The exclusion of inhibitory leader sequences by substitution for MESV sequences is of additional advantage in this regard. This is of importance for all gene transfer/gene therapy applications in which a persistent (if possible life long) expression of the retrovirally transferred sequences is desired in the myeloid system (gene marker studies, correction of metabolic defects).
For this purpose the vector hybrids according to the invention can contain at least one gene that is heterologous for the virus and can be expressed in eukaryotic cells. Such genes are for example the multiple drug resistance gene (MDR gene), an antibiotic resistance gene such as the neon gene, the LNGFR gene, the cerebrosidase gene or the herpes simplex TK gene. In a preferred embodiment several and preferably two or three heterologous genes can also be contained in the vector hybrid. In order to enable an expression of these separate genes, it is expedient to insert a promoter, a splicing site (preferably from SF7Vp) or an internal ribosomal entry site (IRES preferably from polio viruses (I. R. Ghattas et al. (1991) (26)) in front of the second or third gene.
The production of a high virus titre in fibroblastoid packaging cell lines is a further important requirement for retroviral vectors which are intended to be used for gene transfer in myeloid cells. In the case of all the construct examples listed below the activity of the Friend-related U3 regions in fibroblastic retrovirus 199 ~~ 1 packaging cell lines is adequate to produce the required titre of 105 to 106 vector-transferring retroviral particles/ml cell culture supernatant.
Accordingly a subject matter of the invention is also a process for the production of a retrovirally transduced eukaryotic cell which contains an active exogenous gene which is characterized in that the eukaryotic cell is transduced with a replication-defective retroviral vector virus which in its genome contains a) the leader region of MESV or MoMuSV as the leader region b) the U3 and R regions from a Friend murine leukemia virus (F-MuLV) as the U3 and R regions in the 3'-LTR
and c) the said exogenous gene.
The LTR from F-MuLV is preferably used as the 3'-LTR
which then contains the said U3 and R regions.
A further subject matter of the invention are retrovirally transduced, eukaryotic cells obtainable by transducing the eukaryotic cell with a replication defective retroviral vector virus which in its genome contains a) the leader region of MESV and/or MoMuSV as the leader region b) the U3 and R regions from a Friend murine leukemia virus (F-MuLV) as the U3 and R regions in the 3'-LTR.
This vector optionally contains one or several (up to three) exogenous genes which can be expressed in the eukaryotic cell. Mammalian cells preferably haematopoietic cells and especially haematopoietic stem cells are preferably used as eukaryotic cells.

~~~99131 4, The LTR from F-MuLV is preferably used as the 3'-LTR
which then contains the said U3 and R regions.
An active exogenous gene is understood as a gene which is introduced from outside into the cell and is expressed (is active) in this cell after integration into the genome. The exogenous gene may be a gene not present in the cell genome (e. g. an antibiotic resistance gene such as neon, LNGFR receptor (D. Johnson et al. (1986) (33)), the cerebrosidase gene or a herpes simplex TK gene) or a gene present in the genome but not expressed there or only to an inadequate extent such as the multiple drug resistance (MDR) gene.
A further subject matter of the invention is a replication-defective infectious virus particle which contains a retroviral RNA as the genome wherein the genome contains a leader region from MESV which contains a packaging function and a tRNA binding site, and contains a heterologous gene for the virus which can be expressed in a eukaryotic cell and contains at the 3' end U3 and R from a Friend murine leukemia virus (F-MuLV) but no active gag, env and pol sequences.
A further subject matter of the invention is a process for the production of a replication-defective infectious virus particle by transfection of a eukaryotic helper cell which possesses the helper functions gag, env and pol with a vector hybrid which contains the leader region of MESV as the leader region and the LTR from a Friend murine leukemia virus as the 3'-LTR, production of the RNA corresponding to the DNA of the vector hybrid as a virus genome in the cell (for example by cellular polymerases), packaging of the said RNA into the - 2 99~ ~~

replication-deficient empty virus envelopes that are formed in the cell and isolation of the infectious virus particles which contain the said virus genome.
A further subject matter of the invention is the use of a replication-defective retroviral vector hybrid according to the invention which contains the leader region of MESV
as the leader region and the U3 and R regions from a Friend marine leukemia virus (F-MuLV) as the U3 and R
regions in the 3'-LTR for the production of a pharmaceutical agent for ex vivo or in vivo gene therapy.
Vector hybrids are also suitable for the process and uses according to the invention which contain the U5 region and/or tRNA binding site of MESV or MoMuLV/MoMuSV in the leader region as the U5 region and/or tRNA binding site.
l~reas of application I. All somatic gene transfer/gene therapy methods in which myeloid stem cells and precursor cells are the target population for retroviral vectors.
In the individual protocols different cDNAs are integrated into the vectors. Examples are --Gene marker studies (1): Selectable marker genes such as neon or shortened nerve growth factor receptor are transferred in order to monitor the date of the labelled cell population in the organism under the conditions of the examined disease/therapy. The neon vectors pSF2N and pMFilN which carry the neon under the control of the SFFVp U3 and MHSV U3 (MESV leader) exhibit in comparison to neon-transferring Maloney vectors a considerable increase in the functional gene transfer rate in the model system of the mouse stem cell line FDCPmix. They are suitable for neon transfer in human myeloid stem cells.
Protection of bone marrow against the side-effects of a high dose chemotherapy (28): genes mediating chemotherapy resistance such as MDR1 or alkyl transferases are transferred. High transfer rates and expression via the optimized Friend virus-related vectors prevent myelosuppressive side-effects and eventually also secondary tumour induction of the chemotherapy.
--correction of metabolic diseases: In the case of monogenic hereditary diseases intact copies of the defective genes are introduced by means of retroviral gene transfer into myeloid stem cells. Applications are for example conceivable in the case of hereditary diseases whose gene defect has effects on the myeloid system (storage diseases such as the Hurler syndrome; M.
Gaucher (29) ) II Cloning of replication-competent Friend-related retroviruses Due to their extended host spectrum towards early myeloid stem and precursor cells the viruses according to the invention are particularly well suited for insertion mutagenesis in these cells. Insertion mutagenesis enables genes to be cloned which have an important function in the physiological growth regulation of the myeloid system.
The principle of using retroviruses as an insertion -~ ~~ ~3 mutagen has already been described several times (Review:
Kung et al. (1991) (34)). Retroviruses integrate DNA
sequences unspecifically into the genome and in this process can activate or inactivate genes. Replicatable retroviruses infect tissues with a very high efficiency and can therefore increase the probability of producing mutations by integration. Such mutations can in turn lead to a degeneration of the mutated cells i.e. tumours are formed .
In in vivo experiments with mice (usually on new-born mice since they do not yet have an immune system which works efficiently and are therefore very sensitive towards retroviruses) for the identification of regulatory genes, these are infected with retroviruses and, after a latency period of about 3 months, it is possible to discover and examine specific tumours (dependent on the virus type). Analyses of the clonal retroviral integration sites reveal genes whose activation or inactivation can lead to cells of a modified or degenerate phenotype. This enables a large number of diverse gene types to be discovered such as genes for ligands, receptors, signal transducers and transcription factors. It is significant that there is a high correlation between the tumour type found which is produced by particular viruses and the activated/inactivated gene (e.g. in the case of erythroleukemia which is induced by Friend-MuLV ca. 80 %
of the tumours exhibit integration events in the Fli-1 locus and transcriptional activation of the transcription factor PU-1 gene: It was possible to identify interacting oncogenes by infecting transgenic mice with ecotropic expression of an oncogene (e.g. myc) and observing the tumorigenesis. After a considerably shortened latency period tumours were formed by secondary mutations ("second hit" e.g. in the pim-1 gene)).
Nevertheless it has only been possible to identify some of the possible genes using the previous retrovirus constructs. The spectrum of genes that can be identified with this approach of activation/inactivation and the concomitant phenotypic modification of the cell depends strongly on the specificity of the retroviruses used for particular cell types. Thus retroviruses that have been previously used only exhibit a very low infectiousness in haematopoietic and embryonic stem cells (cf. Review:
Stocking et al. (1993) (2Z)). This is due to several reasons; primarily to transcription control elements in the retroviral LTRs (Stocking et al. (1985) (18)) and secondarily also due to the protein interactions between cellular and viral proteins that are necessary for viral replication.
Replication-competent retroviruses produce new cells producing retroviruses by infection which leads to a complete infection of the entire cell population and to a much higher probability of forming mutations. A similar efficiency can only be achieved by a much more complicated and time-consuming co-cultivation of the retrovirus packaging line with the target cell line.
Friend-related replication-competent viruses can in addition be used to produce forced passage mutants which also have an additional improvement of the infectiousness towards blood stem cells. Mutations in retroviral structural proteins of these viruses may be used to produce optimized packaging cell lines for gene transfer into myeloid cells. Mutations in cis regulatory sequences of these viruses may be used to further optimize retroviral vectors for blood stem cell gene transfer.
A further subject matter of the invention are ecotropic, xenotropic, amphotropic or polytropic retroviruses capable of replication containing the regulatory elements (leader region) of MESV and optionally MoMuLV or MoMuSV
combined with the U3 and R regions from a Friend murine leukemia virus (F-MuLV) as U3 and R regions in the 3'-LTR, which as a result are capable of more efficiently infecting murine (in vivo and in vitro) or human (in vitro) precursor cells and to trigger mutations. The retroviruses preferably contain the LTR from F-MuLV as the 3'-LTR.
The combination of both components leads to retroviral insertion mutagenesis constructs of a new quality which can be used to identify genes which cannot be detected with conventional replicatable retroviruses. They can be produced in a very high titre and result in an almost 100 ~ infection rate since each infected cell becomes a production cell for new viruses. The neomycin resistance gene which is used in retroviral vectors for selection can be deleted in them. This leads to a higher transcription of the LTR promoters since neon functions as a silencer (Artelt et al. (1991) (32)) and consequently leads to an improved insertion rate.
Murine as well as human haematopoietic and embryonic stem cells can be infected in vitro with a high efficiency by the retroviruses according to the invention and mutants can be produced by insertion into the genome (activation or inactivation of genes). Therefore also in the case of in vivo experiments it would be expected that the viruses according to the invention would infect early ~ '~g9'~3 1 -lg-haematopoietic and embryonic cells with a higher efficiency and to activate or inactivate genes by integration into the genome.
Gene activation can occur in several ways. Thus integration upstream of a gene can activate it under the transcriptional control of the 3'-LTiZ promoter. The binding sites of negative control elements can also be inactivated which can lead to a gene activation. There are also several examples (Kung et al. (1991) (34)) which demonstrate that the 5~-LTR promoter can activate a gene after insertion is completed either directly by reading through or by its enhancer effect many bases upstream of and also within an intron.
An integration within a gene or in the accompanying promoter/enhancer region can also lead to an inactivation of the corresponding gene.
If genes are effected which are important for the regulation of the cell it is possible that the cells degenerate i.e. tumours may be formed. The viruses according to the invention can therefore be used to find other genes e.g. genes which are involved in the cell regulation of haematopoietic or embryonic stem cells which are different from those that can be found by conventional viruses which do not replicate or only very poorly in such cell types.
The replication-competent viruses according to the invention can also be used in vitro for example in the following manner:
Factor-dependent promyelocytic cell lines were made -~~9~~ 1 factor-independent by retroviral insertion mutagenesis i.e. the growth factor gene was activated by retroviral integration. The retrovirus infection was achieved by co-culturing the target cell line with packaging lines producing the MPSV vector. This in vitro approach can be made more efficient by using the constructs according to the invention. Moreover murine or human embryonic and haematopoietic stem cells can also be used in the above investigations using the viruses according to the invention.
A further application is in experiments which have the goal of producing improved vector virus packaging lines, e.g. for gene therapy, which can produce viruses with a higher infection efficiency in precursor cells. In these cells there are several blocks which interfere with the retroviral infection/replication. The use of the constructs according to the invention has the advantage over replicatable wild-type MoMuLV or AM4o70 that the transcriptional blocks are already removed. Improvements in the infection efficiency can therefore be attributed to corresponding mutations in the viral proteins.
A further application of the constructs according to the invention is to produce "knock out" mice by insertion inactivation of one or several genes in embryonic stem cells.
The invention is further elucidated by the following examples, diagrams and sequence protocols.
The sequence protocols show:
SEQ ID NO:1 sequence of pSFi SEQ ID N0:2 sequence of pSF2 SEQ ID N0:3 sequence of pSF3 SEQ ID NO:~!sequence of pMH1 SEQ ID N0:5 sequence of pSF-MDR

SEQ ID N0:6 sequence of pMP-MDR

(only the viral part of the sequences is shown pro in each case) Fig.11L shows the plasmid map of pSF-MDR:

(information on restriction sites for guidance) Fig.1B shows the plasmid map of pSF-MDR

(more exact details of restriction sites) Fig.2A shows the restriction map of pSFi Fig.2B shows the restriction map of pSFiN. This vector corresponds to pSFl into which the neon gene was inserted into the multiple cloning site (MCS).

Fig.3A shows the restriction map of pSF2 Fig.3B shows the restriction map of pSF2N which corresponds to pSF2 after integration of the neon gene Fig.4A shows the restriction map of pSF3 Fig.4B shows the restriction map of pSF3N which corresponds to pSF3 after integration of the neon gene Fig.5A shows the restriction map of pMIil Fig.5B shows the restriction map of pMHlN which corresponds to pMHl after integration of the neon gene.

Fig.6 shows the scheme for the formation of vector pSF-MDR1.

Fig.7 shows the scheme for the formation of vectors pSFlN, pSF2N, pSF3N and pMHlN.

Fig.8 shows the protection of myeloid cells by FMEV and MPEV-mdrl vectors in comparison to standard MoMuLV vectors. The average relative transduction frequency is stated (corrected for fibroblast titres and cloning efficiency). Fibroblast titres between the various vectors vary by less than factor 3. A: cell line K-562, B:
cell line TF-1.
Fig. 9 shows the restriction map of pMP-MDR.
Example 1 a) Description of construction Table 1 shows the cloning strategies of the constructs according to the invention.
I. p8F-MDR (Fig. 1, 6, Table 1, SEQ ID N0:5) This vector was cloned based on the MESV vector 8224 (base pUC 19) in which parts of the env region as well as the complete U3 region of the 3'LTR were replaced by SFFV-p sequences. Vector pSFS + 3 (cf. Fig. 6) was obtained in this manner. In a second step the cDNA (from pMDR2000XS (25)) coding for MDR1 was inserted into the multiple cloning site (NotI, XbaI, BamHI, Hind3).
II. p8FlN, p8F'2N, p8F3N, pMHlN (Fig. 2-5, 7, Table 1) The backbone of these plasmids is based on the MESV
vector 8224 in which a major deletion had been carried out between the Xbai cleavage site of the the 5'LTR and the Kpnl cleavage site in the 3'LTR. The complementing sequences were inserted by means of three fragment ligations; base vectors pSFl, pSF2, pSF3 and pMHi result (formation scheme and cloning strategy , Fig. 7, Table 1, sequences described in SEQ ID NO:1-4). The fragments used for~the three fragment ligation are obtained from auxiliary constructs (see formation scheme, Fig. 6) in which simple modifications can be carried out in order to further optimize the vectors. It is also conceivable to substitute the SFFVp or MHSV U3 regions by analogous sequences of other Friend-related retroviruses or by the above-mentioned modifications of the leader in order to optimize the titre. The construct examples pSFlN, pSF2N, pSF3N, pMHlN were obtained after insertion of the neon cDNA (from R229). The construct examples carry polylinkers with singular restriction cleavage sites which can be used for the exchange of genes to be transferred. At these cleavage sites it is additionally possible to insert regulatory sequences for secondary gene expression that may be necessary such as the splice acceptor of SFFVp or the so-called internal ribosome entry site IRES (I. R. Ghattas et ai. (1991) (26)).
The Friend-related regions cloned in the construct examples as U3 and R (in the 3'-LTR) are also copied at the 5'-LTR position after completion of a retroviral life cycle and then drive gene expression in the target cells. The construct examples contain all cis regulatory elements necessary for retroviral gene transfer and retroviral gene expression. Properties of SFFVp (or MHSV), MESV and MoMuSV are combined ~n these constructs.
The point mutation of the start codon for the retroviral gag protein to form a stop codon (A. D. Miller and G.J.
Rosman (1990) (27)) and the deletion of superfluous env sequences (27) are integrated as safety-relevant modifications in pSFlN, pSF2N, pSF3N, pMHiN.

_ ~ ~-z ~~ ~~ 1 Table 1. Cloning strategies for the constructs and auxiliary constructs according to the invention.
ConstructBackbone Fragment 1 Fragment 2 pSFMDR SF5+3 Sall/notl pMDRSXl SalljNotl pSF5+3 R224didB Xho 1/Nrul pSFpolyHind3 blunt end pMDR~,SXlbluescript KS Sall/SmalpMDR2000XS Sall/Sspl pSFlN pSFl Notl/BamHl neon Notl/BamHi (R229) pSF2N pSF2 Notl/BamHl neon Notl/BamHI (R229) pSF3N pSF3 Notl/BamHl neon Notl/BamHI (R229) pMHlN pMHl Notl/BamAl neon Notl/BamFiI
(R229) pSFl R229~Xba1/Rpnl pLl Xbal/Notl pOenvSF Notl/Kpnl pSF2 R2290Xbal/Kpnl pL2 Xbal/Notl pOenvSF Notl/Kpnl pSF3 R229~XbalJKpnl pL3 Xbal/Notl pOenvSF Notl/Kpnl pMHi R229~Xba1/Kpnl pLl Xbal/Notl p~envMH Notl/Kpnl pLl bluescript KS Xbal/Notl8224 Xbal/Not 1 pL2 pL10Ba11 pV-MDR 1 Ball pL3 pLl~Kpnl-Pstl pV-MDR1 Kpnl/Pstl p~envMO bluescript RSBamHl/KpnlpV-MDR1 BamHl/Kpnl pOenvSF pOenvMO Nhel/Kpnl pSFU3 Xbal/Rpnl p~envMH p~envSF EcoRS/Kpnl pBR-MHSV EcoR5/Kpnl pSFU3 pUCl9 Hinc2 pSFenv SfaNl/Kpnl ._.

Example 2 Increasing the functional gene transfer rate in comparison to conveatioaal Moloney vectors The multiple drug resistance 1 (MDR1) gene codes for an efflux pump located in the membrane (P-glycoprotein) which mediates resistance to a series of clinically important cytostatic agents (I. Pastan et al. (1988) (25)). The degree of resistance is closely related to the level of expression of P-glycoprotein. If myeloic stem cells are successfully made resistant to cytostatic agents by retroviral MDR1 transfer, this could make an important contribution to lowering the side-effect rate in tumour chemotherapy.
In the experiment K562 cells (ATCC CLL243) and TF-1 cells (human myeloid progenitor cell lines) were infected with retroviral vectors which express MDR1 under the control of the SFFV-LTR (virus SF-MDR
resulting from the construct pSF-MDR with MESV leader and MPSV/MESV hybrid vector pMP-MDR).
The TF1 cell line was obtained from a patient with erythroleukemia as described by T. Kitamura et al.
(1989) (30). The cells are kept in culture in RPMI
medium (supplemented with 20 ~ foetal calf serum, 1 mM
Na pyruvate, 4 mM glutamine and 20 U/ml recombinant GM-CSF) .
K562 cells and TF1 cells were infected in an identical mixture with a Moloney-MDR1 vector (virus V-MDR
resulting from the construct pVMDR) which is used in a clinical gene transfer protocol under the leadership of -21991 ~

Prof. A. Deisseroth at the MD Anderson Cancer Center, Houston, Texas. As can be seen from Table 2 SF-MDR in the case of K562 leads to a 20-fold increase of the gene transfer rate compared to VMDR as measured by the number of colonies growing when cytostatic agents are administered (ca. 10-fold LD50 for R562).
The increase of the functional gene transfer rate in myeloid cells is an expression of the average increase of the gene expression rate in transduced cells. This is important in gene transfer applications whose success also depends on the level of gene expression (see example of application: protection of bone marrow in high-dose chemotherapy). If the cells are plated out with very high doses of cytostatic agents (ca. 20-fold LD50 for TF1) in the experiment described above (infection of human myeloid cells with SFMDR or V-MDR) only cells infected with SF-MDR are able to form colonies (Table 2).
Table 2: Colony number under colchicine selection after infection of human haematopoietic cells K562 and TF1 by MDR1-transduced retroviral vectors. The vectors pSF, MDR
and pMP-MDR considerably increase the functional gene transfer rate compared to a conventional MoMuLV vector.
Number of colonies under selection Virus U3 region Leader K562 (20 ng TF1 (80 ng of 3'LTR colchicine) cochicine) SF-MDR SFFVp MESV 948 +/- 98 13 +/- 3 V-MDR MoMuLV MoMuSV 38 +/- 4 0 MP-MDR MPSV MESV 410 + 28 9 + 3 ~-2 X99 ~~ ~

The cells were infected with a retroviral supernatant of amphotropic packaging cell lines. The .titre of fibroblasts was ca. 2x104/ml for both vectors at the time of the experiment. The ratio of vector/target cell was <1 during infection. 24 hours after the infection 5x104 cells were plated out in soft agar medium containing colchicine. The evaluation was carried out on day 8 of the agar cloning. The cloning efficiency without selection was ca. 15 % for both cell lines. The experiments were carried out in duplicate.
Analogous results are obtained to those of vector pV-MDR
for a vector whose U3 region is derived from MoMuLV and whose leader is derived from MESV.
In the MDR1 system constructs with an MESV leader have slightly reduced titres compared to conventional MoMuSV
vectors. This may be due to mutations in the packaging region of MESV. Hybrids between the leader sequences of MESV and MoMuSV have the potential to produce vectors with a higher titre due to an improved packaging function in retroviral packaging cell lines with simultaneous exclusion of cis-inhibitory sequences. This was taken into account when cloning the construct examples pSF2N and pSF3N.
Note: Proviral vectors are for example denoted SF-MDR, MP-MDR etc. in order to differentiate them from the corresponding plasmids pSF-MDR, pMP-MDR etc..

-~ 991 _28- ~ 1 Example 3 Construction of insertion mutagenesis vectors capable of replication based on the Friend/M$sv vector constructs according to the invention The construct example of an amphotropic Friend/MESV
vector capable of replication was produced for insertion mutagenesis by cloning the gag-pol-env genes necessary for the retroviral replication into the Friend-/MESV
vector pSFl and pSF3 (sae Fig. 2A and 4A).
For this the entire 7.2 kb gag-pol-env gene cassette from pAM (Miller et al. (1985) (35) ) was amplified with the help of the "expand long template PCR system"
(Boehringer Mannheim, see also: W.M. Barns (1994) (36)) and incorporated into pSFl and pSF3.
pAM represents a fusion construct from the ecotropic MoMuLV vector pMLV-K (gag-pol to the SalI cleavage site) and from the amphotropic virus 4070A vector p4070A (pol from the SalI cleavage site and envamphotropic), The upper PCR primer was placed 60 by upstream of the gag start codon (directly adjoining the PstI cleavage site), the lower PCR primer was directly placed at the end of the envamphotropic gene. The 7.2 kb gag-pol-envamphotropic pCR amplificate was incorporated uncleaved i.e. with blunt ends, into the vectors pSF1 and pSF3 that had been cleaved with PstI and HindIII and treated with Klenow enzyme in order to remove overhangs (Sambrook et al. (1989) (37)). The resulting vectors were named pSFi-AM, pSF3-AM and are in principle constructed as follows: 5'-LTRMESV_pgS(_)MESV_gag_pol-env-amphotropic_3~-LTRSFFV (pSFi-AM) and 5'-LTRMESV_ PBS(-)MHSV_gag-pol-envamphotropic_3._LTR-SFFV (pSF3-AM).

-~9~9~1 After transfection in human or murine cells they are able to form replication-competent retroviruses (RCR) which can be used for insertion mutagenesis in haematopoietic stem and progenitor cells.
$xample Construction of insertion mutagenesis vectors capable of regliaation based on MPSV/l~sv vector constructs according to the invention In the vector MoMuLV-TAT (Hilberg, F. et al. Prog. Natl.
Acad. Sci. USA 84 (1987) 5232-5236 (38) the Nhel-Kpnl fragment was replaced by the corresponding LTR fragment of MPSV (-416 - +31). The resulting vector was named MP-CAT. This plasmid can be used as a reporter gene plasmid by expressing the chloroamphenicol transferase (CAT) gene under the control of the retroviral LTR fragment.
The vector P50-M is used as the MPSV/MESV base vector.
This vector contains the MPSV-U3 in the 3'-LTR. It is a derivative of pSGneo which contains a 537 by long leader fragment of d1587rev (Grez M. et al., Proc. Natl. Acad.
Sci. USA 87 (1990), 9202-9206 (39), Colicelli J. and Goff S.P., J. Virol. 57 (1987) 37 - 45 (40)). Neon-env coding regions of pSGneo were replaced by a polylinker from p Bluescript KS (Stratagene) and the AUG of gag was destroyed by point mutation. The mdr-1 cDNA was cut out from pMDR2000XS (base pair -138 - +3878) as a SacI/SspI
fragment (Chen C. et al., Cell 47 (1986) 381 - 389 (41)). After subcloning in p Bluescript II KS the cDNA
was isolated as a BamHI fragment and p50-M was inserted.
The vector produced in this way is named pMP-MDR. The sequence of p-MDR, pMP-MDR is shown in Fig. 9 and SEQ ID
N0:6.

~~9~ 1~ 1 List of references (1) Miller A.D., Nature 357, 455-460 (1992) (2) Mulligan R.C., Science 260, 926-932 (1993) (3) Vile R. and Russell S.J., Gene Therapy 1, 88-98 (1994) (4) Lu M. et al., Human Gene Therapy 5, 203-208 (1994) (5) Palmer T.D. et al., Proc. Natl. Acad. Sci. U.S.A. 88, 1330-1334 (1991) (6) Brenner M.K. et al., The Lancet 342, 1134-1137 (1993) (7) Linemeyer D.L. et al., Proc. Natl. Acad. Sci. U.S.A.78, 1401-1405 (1981) (8) R. Petersen et al., Mol. Cell. Biol. 11, 1213-1221 (1991) (9) Friel J. et al., J. Virol. 64, 369-378 (1990) (10) Clark S.P. and Mak T.W., Nucl. Acid Res. 10, 3315-3330 (1982) (11) Wolff L. et al., J. Virol. 53, 570-578 (1985) (12) Bestwick R.K. et al., J. Virol. 51, 695-705 (1984) (13) Koch W. et al., J. Virol. 49, 828-840 (1984) (14) Adachi A. et al., J. Virol. 50, 813-821 (1984) (15) Ostertag W. et al., Adv. Cancer Res. 48, 193-355 (1987) (16) McKnight S. and Tijan R., Cell 46, 795-805 (1986) (17) Ostertag W. et al., J. Virol. 33, 573-582 (1980) (18) Stocking C. et al., Proc. Natl. Acad. Sci. U.S.A. 82, 5746-5750 (1985) (19) Franz T. et al., Proc. Natl. Acad. Sci. U.S.A. 83, 3292-3296 (1986) (20) Grez M. et al., J. Virol. 65, 4691-4698 (1991) (21) Stocking C. et al., in Virus Strategies, ed. by W.
Doerfler and P. Bohm, VCH Verlagsgesellschaft, Weinheim, Germany (1993) (22) Grez M. et al., Proc. Natl. Acad. Sci. U.S.A. 87, 9202-9206 (1990) (23) Colicelli J. and Goff S.P., J. Virol. 57, 37-45 (1987) (24) Bilello J.A. et al., Virology 107, 331-344 (1980) (25) Pastan I. et al., Proc. Nat. Acad. Sci. USA 85, 4486-_31- -~-~9~~ 1 4490 (1988) (26) Ghattas I.R. et al., Mol. Cell. Biol. 11, 5848-5859 ( 1991) (27) Miller A.D. and Ros~nan G.J., Biotechniques 7, 980-990 (1990) (28) Anderson W.F., Human Gene Therapy 5, 1-2 (1994) (29) Ohashi T. et al., Proc. Nat. Acad. Sci. USA 89, 11332-11336 (1992) (30) T. Kitamura et al., J. Cell. Physiol. 140, 323-334 (1989) (31) M. Kriegler, Gene Transfer and Expression, A Laboratory Manual, W.H. Freeman & Co., New York (1990), 47-55 and (32) P. Artelt et al., Gene 99, 249-254 (1991) (33) D. Johnson et al., Cell 47, 545-554 (1986) (34) H.J. Kung et al., Current Topics in Microbiol. & Immunol.
171 (1991) 1-25 (35) A.D. Miller et al., Molecular and Cell Biology, Vol. 5, No. 3 (1985) 431-437 (36) W.M. Barns, Proc. Natl. Acad. Sci. USA 91 (1994) 2216-(37) J. Sambrook et al., Molecular Cloning: A Laboratory Manual, second edition (1989), CSH Laboratory Press (38) Hilberg, F, et ai, Prog. Natl. Acad. Sci. USA 84 (1987) (39) Grez M. et al., Proc. Natl. Acad. Sci. USA 87 (1990), (40) Colicelli J. and Goff S.P., J. Virol. 57 (1987) 37 - 45 (41) Chen C. et al., Cell 47 (1986) 381 - 389 -~~~9~~~

SEQUENCE LISTING
(1) GENERAL INFORMATION:
(i) APPLICANT:
(A) NAME: BOEHRINGER MANNHEIM GMBH
(B) STREET: Sandhofer Str. 116 (C) CITY: Mannheim (E) COUNTRY: Germany (F) POSTAL CODE (ZIP): D-69305 (G) TELEPHONE: 08856/60-3446 (H) TELEFAX: 08856/60-3451 (ii) TITLE OF INVENTION: Retroviral vector hybrids and the use thereof for gene transfer (iii) NUMBER OF SEQUENCES: 6 (iv) COMPUTER READABLE FORM:
(A) DATA CARRIER: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS
(D) SOFTWARE: PatentIn Release #1.0, Version #1.30B (EPO) (vi) PRIOR APPLICATION DATA:
(A) APPLICATION NUMBER: DE P 44 31 973.8 (B) FILING DATE: 08-SEP-1994 (vi) PRIOR APPLICATION DATA:
(A) APPLICATION NUMBER: DE 195 03 952.1 (B) FILING DATE: 07-FEB-1995 -~9~ ~~ 1 (2) INFORMATION FOR SEQ ID NO: 1:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 5323 base pairs (B) TYPE: nucleotide (C) STRANDEDNESS: double strand (D) TOPOLOGY: circular (ii) MOLECULE TYPE: DNA (genomic) (xi) SEQUENCE DESCRIPTION: SEQ ID NO: l:

p~AAAAAAGGA TCTCAAGAAG ATCCTTTGAT CTTTTCTACG GGGTCTGACG CTCAGTGGAA 3900 i.

CACCAGCGTT TCTGGGTGAG CAAAA.ACAGG AAGGCAAAAT GCCGCAA.A.AA AGGGAATAAG 4860 (2) INFORMATION FOR SEQ ID NO: 2:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 5294 base pairs (B) TYPE: nucleotide (C) STRANDEDNESS: double-strand (D) TOPOLOGY: circular (ii) MOLECULE TYPE: genomic DNA
(xi) SEQUENCE DESCRIPTION: SEQ ID NO: 2:

a -~~9~'~~ ~

GGCGAGTTAC ATGATCCCCC ATGTTGTGCA AA.AAAGCGGT TAGCTCCTTC GGTCCTCCGA 4440 ~~~ ~

(2) INFORMATION FOR SEQ ID NO: 3:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 5292 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: circular (ii) MOLECULE TYPE: DNA (genomic) (xi) SEQUENCE
DESCRIPTION
SEQ ID
NO: 3:

_41_ °~~1991~ 1 GTTCTGGTAG GAGACGAGAP. CCTAAAACAG TTCCCGCCTC CGTCTGAATT TTTGCTTTCG 1020 AACACGAGCC ATAGATAGAA TAAAAGATTT TATTTAGTCT CCAGAAA.AAG GGGGGAATGA 1680 GTACATGAAA ATAGCTAACG TTGGGCCAA.A CAGGATATCT GCGGTGAGCA GTTTCGGCCC 1860 -' GGAA.AAAGAG TTGGTAGCTC TTGATCCGGC AAACAAACCA CCGCTGGTAG CGGTGGTTTT 3780 -43- -~~99~3 ~

AGGCAAAATG CCGCAA.A.AAA GGGAATAAGG GCGACACGGA AATGTTGAAT ACTCATACTC 4860 CCACCTGACG TCTAAGAAAC CATTATTATC ATGACATTAA CCTATAAAA.A TAGGCGTATC 5040 (2) INFORMATION FOR SEQ ID NO: 4:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 5364 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: circular (ii) MOLECULE TYPE: DNA (genomic) (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 4:
CGATTAGTCC AATTTGTTAA AGACAGGATA TCAGGTGGT~C CAGGCTCTAG TTTTGACTCA 60 _ - 46 -GTTCGCTCCA AGCTGGGCTG TGTGCACGA.A CCCCCCGTTC AGCCCGACCG CTGCGCCTTA 3600 (2) INFORMATION FOR SEQ ID NO: 5:
(i) SEQUENCE CFIARACTERISTICS:
(A) LENGTH: 6505 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: circular (ii) MOLECULE TYPE: DNA (genomic) (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 5:

CGACCCCCCC GCCGGGAGGT AAGCTGGCCA GCGGTCGTT~.C CGTGTCTGTC TCTGTCTTTG 780 =~~~ ~

AAGTGATATC AATGATACAG GG'1'TCTTCAT GAATCTGGAG GAAGACATGA CCAGGTATGC 2160 AAGGTACAAC AA.AAATTTAG AAGAAGCTAA AAGAATTGGG ATAAAGAAAG CTATTACAGC 2700 TGACAGCTAT TCGAAGAGTG GGCACAAACC AGATAATAT'P AAGGGAAATT TGGAATTCAG 3000 ATGTTTCCGG TTTGGAGCCT ACTTGGTGGC ACATAAACTC ATGAGCTTTG. AGGATGTTCT 4740 -5~- - ~1~~1~ 1 GCAAGGCATG GAA.AAATACC AAACCAAGAA TAGAGAAGTT CAGATCAAGG GCGGGTACAT 6060 ., - 52 -(2) INFORMATION FOR SEQ ID NO: 6:
(i) SEQUENCE CHARACTERISTICS:
(A) LENGTH: 9318 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: circular (ii) MOLECULE TYPE: DNA (genomic) (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 6:

AAAAGAAACC AAGI'GTCAGT GTATTTTCAA TGTTTCGCTA TTCAAATTGG CTTGACAAGT 1920 ~-~ ~~9'~3 1 TCATGATCAT TGAAAA.AACC CCTTTGATTG ACAGCTACAG CACGGAAGGC CTAATGCCGA 4860 AAAGTGAAAA GGTTGTCCAA GAAGCCCTGG ACAAA.GCCAG AGAAGGCCGC ACCTGCATTG 5460 _ - 56 -CCATAGATAG AATAAAAGAT TTTATTTAGT,CTCCAGAAAA AGGGGGGAAT GAAAGACCCC 5880 GACAGCTTCA AGGATCGCTC GCGGCTCTTA CCAGCCTAAC TTCGATCACT
Gc~AC°~~(~m~n ~o~n _ _ _ ____ _____ _________.... ~"", GCGCCTGATG CGGTATTTTC TCCTTACGCA TCTGTGCGGT ATTTCACACC GCATATGGTG ?080 --X99 ~~ '~

ATATATACTT TAGATTGATT, TAAAACTTCA TTTTTAATTT AAAAGGATCT AGGTGAAGAT 8400 CTGCTTGCAA AC~~AAAAAAC CACCGCTACC AGCGGTGGTT TGTTTGCCGG ATCAAGAGCT 8580 t _ - 58 -

Claims (34)

CLAIMS:

1. A retroviral vector hybrid comprising:
a) at least one element selected from the group consisting of a 5'-long tandem repeat (LTR) and of a tRNA primer binding site, wherein said 5'-LTR comprises a U5 region of murine embryonic stem cell virus (MESV) or of Moloney murine sarcoma virus (MoMuSV), and wherein said tRNA
primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) a 3'-LTR comprising U3 and R regions from a Friend murine leukemia virus (F-MuLV).

2. The vector hybrid of claim 1, wherein said vector hybrid contains the LTR from F-MuLV as the 3'-LTR.

3. The vector hybrid of claim 1, wherein said vector hybrid contains a leader region of MESV.

4. The vector hybrid of claim 1, 2 or 3, wherein the Friend murine leukemia virus is selected from the group consisting of malignant histiosarcoma virus (MHSV), spleen focus forming virus (SFFVp) Lilly-Steeves, spleen focus forming virus (SFFVa), Rauscher SFFV, F-MuLV c157 and Friend-mink cell focus forming virus.

5. The vector hybrid of claim 4, wherein the Friend-mink cell focus forming virus is selected from the group consisting of F-MCFV FrNx and F-MCFV pFM548.

6. The vector hybrid of claim 1, 2, 3, 4 or 5, comprising in the 5'-LTR U3 and R regions from myeloproliferative sarcoma virus (MPSV), MESV or PCC4-cell passaged MPSV (PCMV).

7. A retroviral vector hybrid comprising:
a) a 5'-long tandem repeat (LTR) of a Friend murine leukemia virus (F-MuLV) and a tRNA primer binding site, wherein said tRNA primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) a 3'-LTR comprising U3 and R regions from a Friend murine leukemia virus (F-MuLV).

8. The vector hybrid of claim 1, 2, 3, 4, 5 or 6, wherein the 5'-LTR comprises by 142-657 from SEQ ID NO:1.

9. The vector hybrid of claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the 3'-LTR comprises by 1707-2283 from SEQ ID
NO:1.

10. The vector hybrid of claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, further comprising at least one gene that is heterologous to the retroviral vector hybrid and can be expressed in eukaryotic cells.

11. The vector hybrid of claim 10, wherein the heterologous gene is selected from the group consisting of a multiple drug resistance gene (MDR gene), an antibiotic resistance gene, a low affinity nerve growth factor receptor (LNGFR) gene, a cerebrosidase gene and the herpes simplex thymidine kinase (TK) gene.

12. The vector hybrid of claim 11, wherein the antibiotic resistance gene is a neo R gene.

13. A vector hybrid selected from the group consisting of pSF1, pSF2, pSF3 and pHM1.

14. The vector hybrid of any one of claim 1 to 13, which is replication-defective.

15. The vector hybrid of any one of claim 1 to 9, which is replication-competent.

16. An in vitro process for the production of a retrovirally transduced eukaryotic cell which expresses an exogenous gene, said process comprising transducing a eukaryotic cell with a retroviral vector virus, which virus comprises (in 5' to 3' order:
a) at least one element selected from the group consisting of a U5 region and a tRNA primer binding site, wherein the U5 region is selected from the group consisting of the U5 region of murine embryonic stem cell virus (MESV) and the U5 region of Moloney murine sarcoma virus (MoMuSV), and wherein said tRNA primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) a 3'-LTR comprising U3 and R regions from a Friend murine leukemia virus (F-MuLV).

17. The process of claim 16, wherein the retroviral vector virus further comprises a leader region of MESV.

18. The process of claim 16 or 17, wherein the retroviral vector virus is replication defective.

19. A retrovirally-transduced eukaryotic cell obtained by the process of transducing a eukaryotic cell with a retroviral vector virus comprising (in 5' to 3' order):
a) at least one element selected from the group consisting of a U5 region and a tRNA primer binding site, wherein the U5 region is selected from the group consisting of the U5 region of murine embryonic stem cell virus (MESV) and the U5 region of Moloney murine sarcoma virus (MoMuSV), and wherein said tRNA primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV); and b) a 3'-LTR comprising U3 and R regions from a Friend murine leukemia virus (F-MuLV).

20. The cell of claim 19, wherein the retroviral vector virus further comprises a leader region of MESV.

21. The cell of claim 19 or 20, wherein the retroviral vector virus is replication defective.

22. The cell of claim 19, 20 or 21, wherein the F-MuLV is selected from the group consisting of malignant histiosarcoma virus (MHSV), SFFVp Lilly-Steeves, SFFVa, Rauscher SFFV, F-MuLV c157 and Friend-mink cell focus forming virus.

23. The process of claim 16, 17 or 18, wherein the eukaryotic cell is a haematopoietic stem cell.

24. A replication defective infectious virus particle comprising a retroviral RNA genome, wherein the genome comprises (in 5' to 3' order):
a) at least one element selected from the group consisting of a U5 region and a tRNA primer binding site, wherein the U5 region is selected from the group consisting of the U5 region of murine embryonic stem cell virus (MESV) and the U5 region of Moloney murine sarcoma virus (MoMuSV), wherein said tRNA primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) further comprises a packaging function, a gene which is heterologous to the virus and can be expressed in the eukaryotic cell, and U3 and R
from a Friend murine leukemia virus (F-MuLV) in the 3'-LTR, but c) does not comprise active gag, env and pol sequences.

25. A process for the production of a replication defective infectious virus particle comprising:
a) transfecting a eukaryotic helper cell which has the helper functions gag, env and pol with a vector hybrid comprising (in 5' to 3' order):
i) at least one element selected from the group consisting of a U5 region and a tRNA primer binding site, wherein the U5 region is selected from the group consisting of the U5 region of murine embryonic stem cell virus (MESV) and the U5 region of Moloney murine sarcoma virus (MoMuSV), and wherein said tRNA
primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and ii) a 3'-long tandem repeat (LTR) comprising U3 and R regions from a Friend murine leukemia virus (F-MuLV), b) producing the RNA corresponding to the DNA of the vector hybrid as the virus genome in the cell, c) packaging the virus genome into replication deficient empty virus envelopes formed in the cell, and d) isolating said replication defective infectious virus particle which contains said virus genome.

26. The process of claim 25, wherein the vector hybrid further comprises a leader region of MESV.

27. The process of claim 25 or 26, wherein the F-MuLV
is selected from the group consisting of malignant histiosarcoma virus (MHSV), SFFVp Lilly-Steeves, SFFVa, Rauscher SFFV, F-MuLV cl57 and Friend-mink cell focus forming virus.

28. Use of a replication-defective retroviral vector which comprises (in 5' to 3' order):
a) at least one element selected from the group consisting of a U5 region and a tRNA primer binding site, wherein the U5 region is selected from the group consisting of the U5 region of murine embryonic stem cell virus (MESV) and the U5 region of Moloney murine sarcoma virus (MoMuSV), and wherein said tRNA primer binding site is the tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) a 3'-long tandem repeat (LTR) comprising U3 and R
regions from a Friend murine leukemia virus (F-MuLV), to produce a pharmaceutical agent for ex vivo or in vivo gene therapy.

29. The use of claim 28, wherein the vector hybrid further comprises a leader region of MESV.

30. The use of claim 28 or 29, wherein the F-MuLV is selected from the group consisting of malignant histiosarcoma virus (MHSV), SFFVp Lilly-Steeves, SFFVa, Rauscher SFFV, F-MuLV c157 and Friend-mink cell focus forming virus.

31. A retroviral vector hybrid comprising:
a) a U5 region of murine embryonic stem cell virus (MESV) and a tRNA primer binding site of MESV in a leader region, and b) U3 and R regions from myeloproliferative sarcoma virus (MPSV) as U3 and R regions in a 3' long tandem repeat (LTR).

32. A process for the production of a retrovirally transduced eukaryotic cell comprising an exogenous gene, wherein a eukaryotic cell is transduced with a retroviral vector virus comprising:
a) a U5 region of murine embryonic stem cell virus (MESV) and a tRNA primer binding site of MESV in a leader region, b) U3 and R regions from myeloproliferative sarcoma virus (MPSV) as U3 and R regions in a 3' long tandem repeat (LTR), and c) said exogenous gene.

33. A replication-defective infectious virus particle comprising retroviral RNA as the genome, wherein the genome comprises (in 5' to 3' order) a) at least one of a U5 region of murine embryonic stem cell virus (MESV) and a tRNA primer binding site of murine embryonic stem cell virus (MESV), and b) further comprises a packaging function and a gene which is heterologous for the virus particle and can be expressed in the eukaryotic cell, and U3 and R regions from the myeloproliferative sarcoma virus (MPSV) in the 3'-LTR, but c) does not contain active gag, env and pol sequences.

34. Use of a replication-defective retroviral vector hybrid which contains at least one of a U5 region of MESV
and a tRNA primer binding site of murine embryonic stem cell virus (MESV) in a leader region and U3 and R regions from the myeloproliferative sarcoma virus (MPSV) in a 3' long tandem repeat (LTR) for the production of a pharma-ceutical agent for ex vivo or in vivo gene therapy.