Viral vaccines

Details Viral vaccines Viral vaccines

1995-06-05

2003-04-01

Mosher, Mary E. (Department: 1648)

Drug, bio-affecting and body treating compositions

Antigen, epitope, or other immunospecific immunoeffector

Recombinant virus encoding one or more heterologous proteins...

C424S205100, C424S229100

Reexamination Certificate

active

06541009

ABSTRACT:

The present invention relates to viral vaccines. In particular, it relates to genetically engineered mutant viruses for use as vaccines; vaccines comprising the mutant viruses; recombinant cell; and to methods relating to the production of vaccines.
Viral vaccines are traditionally of two sorts. The first sort are ‘killed’ vaccines, which are virus preparations which have been killed by treatment with a suitable chemical such as beta-propiolactone. The second type are live ‘attenuated’ vaccines, which are viruses which have been rendered less pathogenic to the host, either by specific genetic manipulation of the virus genome, or, more usually, by passage in some type of tissue culture system. These two types of vaccine each have their own disadvantages. Since killed vaccines do not replicate in the host, they must be administered by injection, and hence may generate an inappropriate kind of immune response. For example the Salk vaccine, a killed preparation of poliovirus, produces an immunoglobulin (Ig) G antibody response, but does not stimulate the production of IgA in the gut, the natural site of primary infection. Hence this vaccine, though it can protect the individual from the neurological complications of poliomyelitis, does not block primary infection, and so does not confer “herd immunity”. In addition, killed viruses, do not enter and replicate inside host cells. Hence any beneficial immunological response to non-structural proteins produced during replication is not available. They also cannot stimulate the production of cytotoxic T cells directed against virus antigens. “Dead” antigens can be picked up by antigen presenting cells and presented to T cells. However, the presentation occurs via MHC Class II molecules and leads to stimulation of T helper cells. In turn, the T helper cells help B cells to produce specific antibody against the antigen. In order to stimulate the production of cytotoxic T cells, virus antigens must be processed through a particular pathway inside the infected cell, and presented as broken-up peptide fragments on MHC Class I molecules. This degradation pathway is thought to work most effectively for proteins that are synthesised inside the infected cell, and hence only virus that enters host cells and expresses immunogenic viral protein is capable of generating virus-specific cytotoxic T cells.Therefore, killed vaccines are poor inducers of cellular immunity against virus infection. From this point of view, live attenuated vaccines are more satisfactory.
To date, live attenuated viruses have been made by deleting an inessential gene or partly damaging one or more essential genes (in which case, the damage is such that the genes are still functional, but do not operate so effectively). However, live attenuated viruses often retain residual pathogenicity which can have a deleterious effect on the host. In addition, unless the attenuation is caused by a specific deletion, there remains the possibility of reversion to a more virulent form. Nevertheless, the fact that some viral protein production occurs in the host means that they are often more effective than killed vaccines which cannot produce such viral protein.
Live attenuated viruses, as well as being used as vaccines in their own right, can also be used as ‘vaccine vectors’ for other genes, in other words carriers of genes from a second virus (or other pathogen) against which protection is required. Typically, members of the pox virus family eg. vaccinia virus, are used as vaccine vectors. When a virus, is used as a vaccine vector, it is important that it causes no pathogenic effects. In other words it may need to be attenuated in the same way that a simple virus vaccine is attenuated. The same disadvantages as those described above, therefore apply in this case.
It has been found possible to delete a gene from a viral genome and provide a so-called ‘complementing’ cell which provides the virus with the product of the deleted gene. This has been achieved for certain viruses, for example adenoviruses, herpesviruses and retroviruses. For adenoviruses, a human cell line was transformed with fragments of adenovirus type 5 DNA (Graham, Smiley, Russell & Nairn, J. Gen. Virol., 36,59-72, 1977). The cell line expressed certain viral genes, and it was found that it could support the growth of virus mutants which had those genes deleted or inactivated (Harrison, Graham & Williams, Virology 77, 319-329, 1977). Although the virus grew well on this cell line (the ‘complementing cell line’) and produced standard viral particles, it could not grow at all on normal human cells. Cells expressing the T-antigen-encoding region of the SV40 virus genome (a papovavirus) have also been shown capable of supporting the replication of viruses specifically deleted in this region (Gluzman, Cell, 23,182-195, 1981). For herpes simplex virus, cell lines expressing the gB glycoprotein (Cai et al, J. Virol. 62,714-721, 1987) the gD glycoprotein (Ligas and Johnson, J. Virol. 62,1486, 1988) and the Immediate Early protein ICP4 (Deluca et al., J. Virol., 56,558, 1985) have been produced, and these have been shown capable of supporting the replication of viruses with specifically inactivated copies of the corresponding genes.
The present invention provides a mutant virus for use as a vaccine, in which a viral gene encoding a protein which is essential for the production of infectious virus has been deleted or inactivated; and wherein said virus can be grown in a cell which has a heterologous nucleotide sequence which allows said cell to express the essential protein encoded by said deleted or inactivated viral gene.
The present invention also provides a vaccine which comprises a virus as described above, together with one or more excipients and/or adjuvants. The viral genome may itself provide the immunogen, or it may contain a heterologous gene insert expressing the immunogenic protein.
The present invention also provides a complementing cell transfected with an attenuated virus as described above, for use in the preparation of a vaccine.
The present invention also provides a method which comprises the use of a virus as described above in the preparation of a vaccine for the therapeutic or prophylactic treatment of a disease.
The present invention also provides a method for the production of a vaccine which comprises: culturing a cell infected with a virus having a deleted or inactivated viral gene encoding a protein which is essential for the production of infectious virus, and wherein the host cell has a heterologous nucleotide sequence comprising said viral gene and which is able to express the essential protein encoded by said gene; harvesting the virus thus produced, and using it in a vaccine.
The virus may be derived from herpes simplex virus (HSV) in which, for example, the gene encoding glycoprotein H (gH) has been inactivated or deleted. The mutant virus may also comprise a heterologous sequence encoding an immunogen derived from a pathogen. The host cell will suitably be a recombinant eukaryotic cell line containing the gene encoding HSV glycoprotein H. As another example the virus may be derived from an orthopox virus, for example, vaccinia virus, which again may comprise a heterologous sequence encoding an immunogen derived from a pathogen.
This invention shows a unique way of combining the efficacy and safety of a killed vaccine with the extra immunological response induced by the in vivo production of viral protein by the attenuated vaccine. In preferred embodiments it comprises two features. Firstly, a selected gene is inactivated within the virus genome, usually by creating a specific deletion. This gene will be involved in the production of infectious virus, but preferably not preventing replication of the viral genome. Thus the infected cell can produce more viral protein from the replicated genetic material, and in some cases new virus particles may be produced, but these would not be infectious. This means that the viral infection cannot spread from the site of inoculation.
A second feature of the inve

Affiliated with

Also associated with

Rating

Viral vaccines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Viral vaccines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Viral vaccines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3067282