Many ways of providing cells with additional nucleic acids are now known in the field. Many proteins have been expressed in many kinds of cells, ranging fro prokaryotic bacteria and bacilli, via yeast and fungi, to plant cells, insect cells and mammalian cells.
Often, expression of proteins as previously discussed has met with success. There are, however, certain areas in the field of recombinant technology where, because of safety issues or technical problems, such as stability of the additional nucleic acid material introduced, success has not been easy to achieve. Also, in the application of genetic engineering where the product is not a protein but, for instance, a nucleic acid of interest (such as DNA, RNA or an antisense construct), the same or similar problems have been encountered. It is in these areas particularly that the present invention finds its particular use.
One of the problems encountered in recombinant technology is that it is often desirable to have the additional nucleic acid material, which is introduced into a host cell, integrate into the genome of the host cell. Once the additional nucleic acid material is integrated in the genome, its stability is much less an issue. Moreover, the integrated material is replicated together with the genome and thus will be present in the offspring of the recombinant cell as well. Vectors which are capable of providing for integration of additional nucleic acid material into a host cell are known, but they suffer from some drawbacks which will be discussed herein.
One of the drawbacks of the integrating vectors of the prior art is that they are often not capable of transducing a host cell efficiently. Techniques such as electroporation and the like are then necessary for achieving transduction.
In some areas, such treatments of cells may be unwanted or impossible. One such an area is, for instance, gene therapy. In such cases, vectors which can efficiently transduce host cells on their own, or which can be packaged into recombinant viral particles and so infect host cells, are often employed. However, many of these vectors are then incapable of efficient integration of the desired additional nucleic acid material in the genome of the host.