Under interferons there is to be understood a group of proteins which are specific to the body and which have antiviral and immunoregulatory activity. The antiviral effect is achieved not by a direct influence on the viruses themselves, but by an activity on their target cells in the sense of a protection against the virus infection. The interferons can exert objectifiable effects on cancer tumours, which make them suitable for use in cancer therapy, and they can influence the immune system of the body in that, for example, they activate macrophages and NK cells and intensify the expression of various immunologically significant constituents of the cell membrane.
Human interferons (.alpha., .beta.and .gamma.) can today be prepared in a microbiological manner thanks to recombinant DNA technology in amounts which can not be made available by isolation from natural material (leucocytes, fibroblasts, lymphocytes) and purification in spite of the greatest efforts.
For the first time this new technology has opened a way for the intensive clinical testing and possible wide therapeutic use of interferons and an adequate supply of the active substances should appear feasible for persons seeking a treatment with the active substances.
Details of the cloning of interferon-cDNA and the direct expression thereof, especially in E. coli, have in the meanwhile been the subject of many publications. Thus, for example, the preparation of recombinant interferons is known, for example, from J. Interferon Res. 1 (1981), 381-390 (Wetzel et al.), Nature 284 (1980), 316-320 (Nagata et al,), Nucleic Acids Res. 8 (1980), 4057-4074 (Goeddel et al.), Nucleic Acids Res. 10 (1982), 2487-2501 (Devos et al.), Nature 295 (1982), 503-508 (Gray et al.), as well as from German Offenlegungsschriften Nos. 31 25 706, 31 38 096 and 31 44 469.
Since the recombinant interferons are of microbial origin (e.g. they are preferably derived from E. coli), after their isolation from the microorganism or from the culture medium they are initially still contaminated by a series of microbial impurities, the presence of which is prohibitive for a therapeutic use of the thus-produced interferons. The purification of the recombinant material therefore plays a particularly important role. A multitude of different methods, especially chromatography, have hitherto been used and combined with one another (see e.g. German Offenlegungsschrift No. 31 25 706) for the purification of recombinant interferons. Above all, chromatography on immunoadsorbents, namely on anti-interferon antibodies, has proved to be a valuable aid. Thus, the purification of recombinant human leucocyte interferon (HuIFN-.alpha.) by means of monoclonal antibodies has been described, for example, by Staehelin et al. [J. Biol. Chem. 256 (1981), 9750-9754] and by Secher et al. [Nature 285 (1980), 446-450]. Having regard to the high specificity of these immunoadsorbents it must be assumed from this that the thus-purified material is practically free from contaminating substances and has a high degree of purity.
In the case of the purification of larger amounts of recombinant leucocyte interferon by means of monoclonal antibodies it has, however, been found that the purified material contains not only interferon fragments (interferon in which a part of the terminal amino acid sequence is missing), but also interferon oligomers, for example dimers. These undesirable byproducts have only a part of the biological activity of the pure interferon with comparable affinity to the antibodies.
A method for the purification of human fibroblast interferon (HuIFN-.beta.) by means of a resin of the formula ##STR2## wherein Me signifies cobalt, nickel, zinc or copper, which is known from Nature 258 (1975), 598-599 (Porath et al.), has now been described in European Patent Apecification No. 11435. In addition, Edy et al. [J. Biol. Chem. 252 (1977), 5934-5935] have described the successful purification of HuIFN-.beta. on the zinc chelate resin described above. Chadha et al. [J. gen. Virol. 43 (1979), 701-706] subsequently showed that HuIFN-.alpha. can not be purified on the zinc copper chelate resins successfully employed in the case of HuIFN-.beta. and thus confirmed the observation previously made by Edy et al. (loc. cit.).