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.

1 . A mutant herpesvirus which 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.  
     
     
         2 . A mutant herpesvirus according to  claim 1 , wherein mutation (a) is a mutation effective to reduce the ability of the virus to cause expression of at least one immediate early gene function.  
     
     
         3 . A mutant herpesvirus according to  claim 2 , wherein mutation (a) is a mutation in the VP16 gene which is effective to reduce the transinducing properties of the protein encoded by that gene.  
     
     
         4 . A mutant herpesvirus according to  claim 2 , wherein mutation (a) is a mutation in the VP16 gene that allows growth of the mutant virus in cell culture in the presence of hexamethylene bisacetamide (HMBA), e.g. a in 1814 mutation.  
     
     
         5 . A mutant herpesvirus according to  claim 2 , wherein mutation (a) is a mutation in the gene encoding ICP0, ICP4, ICP22 or ICP27, (i.e. gene IE0, IE4, IE22 or IE27).  
     
     
         6 . A mutant herpesvirus according to  claim 1 , wherein mutation (b) is an inactivating mutation in.an essential viral glycoprotein gene.  
     
     
         7 . A mutant herpesvirus according to  claim 6 . wherein mutation (b) is a deletion of the gH gene.  
     
     
         8 . A mutant herpesvirus according to  claim 1 , wherein the virus is a herpes simplex virus of type 1 (HSV-1) or type 2 (HSV-2). human or animal cytomegalovirus (CMV), varicella zoster virus (VZV). Epstein-Barr virus (EBV), human herpesvirus 6 or 7, pseudorabies virus (PRV). an equine or bovine herpesvirus (EHV or BHV) or a Marek's disease virus (MDV).  
     
     
         9 . A mutant herpesvirus according to  claim 1 , wherein the mutant virus genome further comprises a DNA insert encoding a heterologcus polypeptide expressible within a cell infected by the mutant virus.  
     
     
         10 . A mutant herpesvirus according to  claim 9 , wherein the DNA insert is located at the site of inactivating mutation (b).  
     
     
         11 . A mutant herpesvirus according to  claim 9  or  10 , having a genome which includes a coding sequences) for one or more polypeptides, in which the coding sequences) comprise gene(s) for gene therapy in order to supplement a patient with a protein, e.g. ADA, normally absent or functionally defective in the patient.  
     
     
         12 . An injectable pharmaceutical composition comprising a mutant herpesvirus according to any of  claims 1  to  11 .  
     
     
         13 . Use of a mutant herpesvirus according to any of  claims 1  to  11  as a vector for gene therapy.  
     
     
         14 . A cell infected with a mutant herpesvirus according to  claim 1 , said cell being of a type on which said virus is unable to cause production of infectious new virus particles.  
     
     
         15 . A method of expressing a heterologous gene in a cell, which comprises infecting the cell with a virus according to  claim 9 ,  10 , or  11 , said virus being unable to cause production of infectious new virus particles or lysis of said cell when said virus infects said cell.