Drug – bio-affecting and body treating compositions – Antigen – epitope – or other immunospecific immunoeffector – Recombinant virus encoding one or more heterologous proteins...
Reexamination Certificate
2002-08-22
2004-01-27
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...
C424S232100, C424S281100, C424S093200, C435S235100, C435S237000, C435S320100, C435S069100, C435S091100, C435S456000, C435S325000
Reexamination Certificate
active
06682743
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to new strains of the Modified Vaccinia virus Ankara (MVA) that have a strongly reduced virulence for most mammals, especially humans, but nevertheless grows in cells of a continuous cell line approved for the production of a therapeutic agent such as a vaccine. The invention also relates to a method for producing said adapted MVA strains. The MVA can be used e.g. for parenteral immunization, as a vector system, or in the active or inactivated form as an adjuvant or as a regulator of the unspecific components of the immune system.
BACKGROUND OF THE INVENTION
An organism is constantly challenged by infectious agents like bacteria, viruses, fungi or parasites. The immune system prevents the organism from permanent infection caused by these agents by the destruction and elimination of these infectious agents and any toxic molecules produced by them. The immune system can be divided into a specific and an unspecific part although both parts are closely cross linked. The unspecific immune response enables an immediate defense against a wide variety of foreign substances and infectious agents. In contrast, the specific immune response is raised after a lag phase, when the organism is challenged with a substance for the first time. However, the specific immune response is highly efficient. The specific immune response is responsible for the fact that an individual who recovers from a specific infection is protected against this specific infection but still susceptible for other infectious diseases. In general, a second infection with the same or a very similar infectious agent causes much milder symptoms or no symptoms at all. The immunity persists for a long time, in some cases even lifelong. This immunological memory is used for vaccination, where the organism is challenged with a harmless or inactivated form of the infectious agent to induce a specific immunity. Sometimes adjuvants are incorporated into vaccines to enhance the specific immune response.
Much of the knowledge about infectious diseases and immunity is contributed by studies of smallpox. The disease is caused by the variola virus, a member of the genus of Orthopox viruses. Nearly two centuries ago, prophylactic inoculations with cowpox was initiated resulting in the immunization against smallpox. Later immunization was performed with the Vaccinia virus. In the early 1950s, many of the industrialized countries had eliminated endemic smallpox by using vaccination with Vaccinia virus. However, smallpox vaccination with this Vaccinia virus resulted occasionally in serious complications, such as postvaccinal encephalitis, generalized Vaccinia or contact infection.
A new vaccine that does not show these complications was developed by Anton Mayr. The pox vaccine consists of the pox virus Modified Vaccinia Virus Ankara (MVA) and was used for parenteral vaccination against smallpox in about 150 000 vaccinations without causing any complications related to the vaccination. Even children with immunologic deficiencies did not show serious side effects. The MVA was obtained by mutation and selection of the original vaccina virus Ankara after 575 passages in chicken embryo fibroblast cultures. The safety of this MVA is reflected by biological, chemical and physical characteristics. MVA has a reduced molecular weight, six deletions in the genome, and is highly attenuated for mammalian cells, i.e. DNA and protein is synthesized but virtually no viral particles are produced. The Modified Vaccina virus Ankara developed by Anton Mayr was deposited at the European Collection of Cell Cultures (ECACC), Salisbury, UK, under depository No. V 94012707.
The vaccination against smallpox was highly successful. In 1979, the World Health Organization declared the eradication of smallpox. Accordingly, the mass vaccination of children was discontinued and only laboratory workers and members of the armed forces of some countries are vaccinated.
With the eradication of smallpox, the predominant cause of pox infection in humans was removed. However, some non-human poxviruses have reduced host specificity, i.e. they cause infections not only in their typical host (e.g. for cowpox the cow), but also in other animals, (e.g. rats and cats). Humans can be infected by this route as well. Since parts of the population are no longer immune against smallpox, orthopox infections of animal species can be dangerous for them. Domestic animals are the main source of infection for humans. Accordingly, the vaccination of domestic animals against orthopoxviruses is of increasing importance. In addition, the MVA may be of significance as a vector for gene therapy, i.e. to transfer nucleic acid sequences into a target cell where they are expressed.
For a logarithmic reproduction of the MVA cell cultures of primary or secondary chicken embryo fibroblasts are needed. The cells are obtained from chicken eggs that are incubated for 10 to 12 days. Since eggs are subjected to a biological variability, the cells obtained for the cell culture system are variable on a cellular level as well. In addition, in a chicken embryo “fibroblast culture” often other cell types such as epithelial cells are found. This variation of the cells also results in variation of viruses produced in chicken embryo fibroblasts. It is therefore difficult to standardize and validate the cell culture system to guarantee a constantly high quality of the MVA produced. Furthermore, contamination of the cell culture system by microorganisms or viruses already present in the incubated eggs can not be completely excluded. When the MVA is grown in virus-contaminated cells, the MVA may recombine with the contaminating virus. Thereby an MVA with new and unpredictable characteristics may be generated. For the production of the virus in large scale in a suspension culture, primary or secondary chicken embryo fibroblasts are also not highly suitable. In addition, the purification and concentration of MVA by ultra gradient centrifugation would be advantageous. However, such purification is difficult, when MVA is cultivated on primary or secondary chicken embryo fibroblast. Finally, an increasing number of patients have developed allergies against chicken egg's albumen. Although the in vitro conditions of the cultivation strongly reduce the allergenic potential, a hazard of an allergic reaction can not be completely excluded.
In conclusion, on the one hand the MVA can only be efficiently grown in primary or secondary chicken embryo fibroblasts causing a number of disadvantages, however, on the other hand the save application of the MVA in humans has been shown by its large-scale application as a vaccine.
OBJECT OF THE INVENTION
It is an object of the present invention to provide conditions for the production of homogeneous virus particles of the MVA. A Additionally, said conditions should allow an easy and large-scale production of the MVA.
DETAILED DESCRIPTION OF THE INVENTION
To achieve the foregoing and other objects, the present invention provides an MVA strain that is adapted for growing in cells of a continuous cell line, said cell line being approved for the production of a therapeutic agent.
According to the present invention, for the first time an efficient and large-scale production of MVA is possible. Since cells of a continuous cell line are homogeneous and their characteristics are stable the MVA harvested from these cell lines is also homogeneous with highly predictable characteristics. Furthermore, the risk of contamination by microorganisms can be controlled and contamination of the MVA preparation by proteins of the chicken egg—as found when cultivating MVA on chicken embryo fibroblasts—can be excluded. The handling of a permanent cell line is convenient and thus highly suitable for industrial application.
In a preferred embodiment of the invention, the MVA is adapted for growing in cells of a mammalian cell line, which is approved for the production of a vaccine. It has been surprisingly found that the MVA adapted to a mammalian cell line such
Bavarian Nordic A/S
Dubno Herbert
Mosher Mary E.
Myers Jonathan
LandOfFree
Altered strain of the modified vaccinia virus ankara (MVA) does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Altered strain of the modified vaccinia virus ankara (MVA), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Altered strain of the modified vaccinia virus ankara (MVA) will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3201887