Retroviral vectors

Details Retroviral vectors Retroviral vectors

1997-11-19

2000-08-01

Priebe, Scott D.

Chemistry: molecular biology and microbiology

Animal cell, per se ; composition thereof; process of...

435 691, 4353201, 435455, 424 9321, C12N 1500

Patent

active

06096538&

DESCRIPTION:

BRIEF SUMMARY
This invention relates to retroviral vectors and to DNA constructs encoding RNA genomes for retroviral vectors. In particular it relates to retroviral vectors for gene therapy for treatment or prevention of retrovirus infections, such as HIV.
Despite intensive research efforts, there has been limited success in the development of low molecular weight compounds as treatments for HIV infection and AIDS. Similarly, it seems unlikely that a protective or therapeutic vaccine will be produced in the near future. This situation has led to recent proposals that greater emphasis should be given to biological therapeutics (Lehrman, 1994) and there is currently much interest in the prospect of gene therapy as a clinical approach to HIV-1 infection. Several molecules have been proposed as anti-HIV therapeutics, including ribozymes, trans-dominant proteins, scFv molecules, antisense constructs and TAR and RRE decoys (reviewed in Yu et al. 1994). These molecules are envisaged to act both as therapy against already infected cells and as protective `intracellular immunisation` (Baltimore, 1988) in uninfected cells. In addition, the use of toxins (suicide genes) or immunological markers has also been proposed as a means of killing infected cells and so reducing the viral load in the patient.
For many of these molecules, it is desirable that expression can be regulated. This is clearly the case for suicide genes, but the constitutive expression of a therapeutic protein may also be undesirable in that it may cause some cellular toxicity or lead to a host immunological response. Furthermore, toxic side effects are also possible from the expression of RNA molecules in cells, including the inappropriate induction of interferon responses. In the case of HIV, the viral LTR promoter itself has the characteristic of being an inducible promoter, directing low basal levels of transcription in the absence of the virally encoded Tat trans-activator protein (Arya et al. 1985). Tat-inducibility is a property of sequences in the U3 region of the LTR and the TAR sequence in the R region (Berkhout and Jeang, 1992). Allowing the HIV LTR to direct expression of a therapeutic gene will therefore limit its expression to those cells infected by HIV. Several groups have already started exploring ways of using this property of the LTR and have demonstrated inducible expression of genes upon HIV infection (Caruso et al. 1992, Brady et al. 1994).
Current strategies to deliver a Tat-inducible therapeutic gene (TITG) by MLV based retroviral vectors place the TITG internally in the vector. A major drawback of placing a second promoter within the retroviral LTR transcriptional unit (either in a sense or antisense orientation) is that it can result in reduced gene expression (Kadesch et al. 1986, Williams et al. 1986, Mclvor et al. 1987, Bowtell et al. 1988). This is not suprising as it has been shown that the activity of promoters is often reduced when placed downstream from an active promoter, (Cullen et al. 1984, Emerman and Temin, 1984, Emerman and Temin 1986, Overell et al. 1988) and internal promoters can be unstable in long term culture, even without selection for the vector LTR driven gene (Xu et al. 1989, Li et al. 1992). Furthermore, transcriptional readthrough from an upstream retroviral promoter can also be a problem when expression of the internally placed gene is to be under the control of a regulated promoter, such as the HIV LTR.
Several strategies have been developed for preventing readthrough or interference from the 5' vector promoter. The simplest option to prevent unwanted expression by readthrough is to place the TITG in reverse orientation to the vector LTR (Brady et al. 1994, Liem et al. 1993). However, this configuration can lead to lower levels of transduction or expression (Stuhlman et al. 1989, Poznansky et al. 1991) and may lead to suppression of gene expression by antisense transcripts originating from the vector LTR.
A further possibility is to use a self-inactivating (SIN) vector (Yu et al. 1986). Here, part of the 3' U3 s

REFERENCES:
patent: 4738922 (1988-04-01), Hasetine et al.
patent: 5665577 (1997-09-01), Sodroski et al.
patent: 5672510 (1997-09-01), Eglitis et al.
patent: 5693508 (1997-12-01), Chang
patent: 5716832 (1998-02-01), Barber et al.
patent: 5747307 (1998-05-01), Lever et al.
Soneoka et al., Nucleic Acid Research, vol. 23, 4, 628-633, 1995, p. 9345, 1995.
Crystal, Science, vol. 270:404-410, 1995.
Gunzburg et al. (Molecular Medicine Today, pp. 410-417, 1995).
Hariharan et al. (Nucleic acids Research, vol. 16, No. 19, 1988).

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