Recombinant virus vectors

Abstract

A mutant herpesvirus that can be used as a recombinant virus vector comprises (a) a mutation such that the mutant virus has a reduced ability in comparison with a parent type to cause lysis of an infected cell, and (b) an inactivating mutation in a gene essential for the production of infectious virus. An example is a HSV1 mutant lacking the essential glycoprotein gH gene and having a mutation impairing the function of gene product VP16. A heterologous gene can be carried at the site of the inactivated essential gene, e.g. a gene suitable for administering gene therapy. The vector has an increased margin of safety over known herpesvirus vectors in respect of incidence of cytopathic effects and / or risk of reversion.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to mutant viruses that can be used as recombinant virus vectors. The invention also relates to mutant virus vectors that can be used for the delivery to cells of nucleotide sequence(s) encoding polypeptide(s). The invention also relates to cells infected by such mutant viruses and to materials and methods for delivering nucleotide sequencers) encoding polypeptide(s) to host cells ex vivo or to treated subjects in vivo such as human patients by use of a recombinant virus vector based on such mutant herpesvirus.[0003] Many disorders which manifest in symptoms such as respiratory distress, growth abnormalities, muscular insufficiency, and / or mental retardation result from the inheritance of genetic material which is defective in that a gene coding for the synthesis of a protein is either completely or partially absent, or of an incorrect coding sequence. Thus the defect results in the disruption of the normal activiti...

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Benefits of technology

[0012] The further genetic defect in the form of inactivating mutation (b) brings a safety advantage in that this mutation can be such that it is not susceptible of complementation within the host cell, and is practically free from risk of reversion. Such a further genetic defect is known per se, being of the kind described in specification WO 92 / 05263 (SC Inglis et al: Immunology Ltd) and corresponding GB 2 263 480 (Cantab Pharmaceuticals Ltd) entitled "Viral Defective Vaccine Produced by Transcomplementing Cell Line" which describe a mutant virus for use as a vaccine, having a genome which is defective in respect of a gene essential for the production of normal infectious virus. Mutant virus of this kind can be propagated on a recombinant complementing cell which provides the virus with the product of the deleted gene, thus making it possible to grow the virus in tissue culture.

[0014] Embodiments of the invention can in this connection have an advantage in that they can combine an increased margin of safety over known herpesvirus vectors in respect of the incidence of cytopathic effects and / or of the risk of reversion to virulence, along with useful persistence of expression, in cells of the treated subject, of the gene carried by the vector.

[0027] The nature of the mutation(s) created in the target essential viral gene(s) is a latter of choice. An change which produces a non-functional gene product can be satisfactory, preferably being such as to minimise risk of reversion to a wild type structure. Such changes include interruption of the target with extraneous sequences and creation of specific deletions. The preferred mutation for a virus intended for use in treatment of humans however is a deletion that encompasses the entire sequence to be introduced into the complementing cell. This approach minimises the risk of regenerating wild type virus through recombination between the virus and cell DNA in the complementing cell.

[0028] A particular example of a mutant virus according to the invention, more particularly described below, is based on HSV-1 and includes the mutation of mutant strain in 1814 and complete deletion of the glycoprotein gH gene. It is considered that since the mutation in 1814 is a small sequence insertion, there is an appreciably high probability that the mutant will revert to wild-type in respect of its VP16 function. Thus with strain in 1814 there is a finite probability of lytic Infection developing and this probability varies from cell type to cell types The mutant virus example described below has the safety advantage over strain in 1814 of a much reduced or zero risk of reversion to replication competence and lytic ability.

[0033] A further embodiment of the invention provides a recombinant herpesvirus vector carrying (a) a mutation that reduces the capability of the virus to cause lysis of a cell that it infects, (b) an inactivating mutation in an essential viral gene and (c) a gene intended to be expressed in a host cell infected by the vector, said gene being inserted at the site of the essential viral gene affected by the inactivating mutation (b).

[0037] The present invention also provides a method of manufacturing (propagating) such a mutant virus which comprises culturing cells infected with the mutant virus, the cells also expressing a gene which complements the defective gene essential for the production of infectious virus, so as to allow the production of infectious virus particles containing the defective genome, and recovering the mutant virus from the culture.

Problems solved by technology

Thus the defect results in the disruption of the normal activities of cells which are dependent upon the normal protein for correct functioning.

Nevertheless, a disadvantage of wild-type HSV is that it is a lytic virus whose growth results in cell damage or cell death.

Therefore, the use of an unmodified form of an HSV virus vector is unacceptable, and even some modified forms can carry significant risks.

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