MXPA98007323A - Purification of plasmid dna of pharmaceutical quality - Google Patents

Abstract

The present invention relates to a process for the purification of pharmaceutical grade plasmid DNA comprising at least one step of hydroxypati column chromatography

Description

- Ej1lS-a ------- E8t-MQ ----- i - fc-3C - t ^ jB-fl-l - Mf? LE ---. HB- - - ^^ The present invention relates to a new process for the purification of DNA. The method according to the invention allows the double-stranded DNA pharmacologically usable to be purified rapidly. More particularly, the purification process according to the invention only intervenes in diafiltration and chromatography.

Gene and cell therapy techniques are currently undergoing an extraordinary development. However, these techniques involve the possibility of producing significant amounts of DNA of pharmacological purity, in particular of plasmid DNA. Indeed within these new therapies, the drug is often made up of the same DNA, and it is essential to be able to manufacture in the adapted quantities, isolate and purify it in an appropriate manner for a therapeutic use in man, in particular by intravenous route.

These problems of quantity and purity have not been taken into account in classical methods of DNA isolation. In fact, the methods used in the laboratory are not transposable in the domain of the pharmaceutical industry for REF .: 27988 purify the plasmidic DNA. Two of these methods are the most used and are the ones that give the best results. They consist of starting from a crude bacterial lysate and enriching plasmid DNA, eliminating a maximum of contaminants. In particular, the lysozyme of the egg white and used is used to break the bacterial wall and then the lysate was centrifuged to remove the cell debris. The supernatant was then subjected to the action of a pancreatic RNA of animal origin which allows the RNA to be eliminated, which at this moment represents approximately 75% of the nucleic acids present.

The proteins are then precipitated with a phenol / chloroform / isoamyl alcohol mixture. The supernatant obtained after the centrifugation was separated from the proteins and the RNA but still containing large amounts of chromosomal DNA that must be removed in a supplementary step. This stage consists of an ultracentrifugation in the presence of Ethidium Bromide and Cesium Chloride. The three types of nucleic acids that are chromosomal DNA, plasmid DNA and RNA have a greater or lesser ability to bind ethyl bromide. In fact they are separated into three distinct phases in a gradient ultracentrifugation of cesium chloride.

A variant of this protocol consists of following the action of the pancreatic Rnase by a reduction in the presence of an alkaline detergent, followed by an extraction in phenol / chloroform. The DNA is then precipitated with ethanol, suspended and reprecipitated with polyethylene glycol.

These two methods that allow to obtain a solution of Plasmid DNAs are meanwhile used for the industrial production of a product of pharmaceutical purity. Indeed the use of enzymes of animal origin poses the problem. Thus lysozyme and pancreatic RNase, in fact of their origin, put at risk to introduce a viral contamination in the final product. In addition, organic solvents are extremely toxic and should be eliminated if you want to be able to use the product as a medicine. This solvent also induces a considerable increase of costs, linked in particular to its storage, its use in the conditions of maximum security and the elimination of toxic waste that it loads, and also because of the difficulty encountered to succeed in validating the complete elimination of such products of the final solution. Ethidium bromide is such a toxic, mutagenic and teratogenic that its very presence in the form of traces can not be tolerated in a product for pharmaceutical purposes. The use of solvents, of toxic reagents, of the same enzymes of animal origin is incompatible with an industrial procedure that responds to Good Manufacturing Practices.

The present invention describes a new simple and particularly effective procedure for the purification of DNA. The process described in the present application allows the production in large quantity of a DNA of very high purity. In a particularly advantageous manner, the method described in the present application makes it possible to avoid the use of toxic organic solvents and enzymes of animal origin. It also makes it possible to get rid of numerous and annoying centrifuges that are difficult to extrapolate and of low yield, particularly due to precipitation stages in PEG, in ammonium acetate or in CaC12. The method according to the invention also allows obtaining large amounts of DNA (100 mg, 1 g, 10 g or more) in a single batch, without particular technical difficulty. In another, the method according to the invention mentions the methods compatible with the Good Manufacturing Practices and allows obtaining a DNA of pharmaceutical quality.

A first objective of the invention relates to a method for the purification of double-stranded DNA which allows to obtain very quickly large quantities of plasmid DNA of pharmaceutical purity, which involves a step of chromatography on hydroxyapatite column in ceramic form. Hydroxyapatite in crystalline form was already known but, in fact, of its fragility, of a difficult and limited use. The ceramic form is very resistant both in a physical plan and in a chemical plan.

In a preferred manner, the method of the invention comprises two chromatography steps, at least one is a hydroxyapatite chromatography.

Advantageously, the second chromatography is an affinity or ion exchange chromatography. The two chromatographies can be done in an indifferent order.

According to a particularly preferred embodiment, the process according to the invention comprises a step of hydroxyapatite column chromatography and a Triple-Helix affinity chromatography step. Triple-Helix affinity chromatography is based on the use of a support in which an oligonucleotide capable of hybridizing a triple helix with a specific sequence present in said DNA is covalently coupled. The two chromatographies can be done in an indifferent order.

According to another embodiment, the method of the invention comprises a step of hydroxyapatite column chromatography and an anion exchange chromatography step.

Advantageously, the process of the invention further comprises a diafiltration step. The one that is done in general before the chromatographies.

Hydroxyapatite column chromatography is involved in an important step of the process of the invention.

Hydroxyapatite is a complex calcium phosphate that contains ten calcium atoms. The more stable ceramic form than the crystalline form is available from Bio-Rad Laboratories and Asahi Optical Co., Ltd. The ceramic compound has the same properties as the crystalline compound without having the physical limitations; This material is used above all in chromatography for the purification of proteins, but it has advantages and allows obtaining very good results in the purification of nucleic acids. It is macroporous, spherical, chemically and physically very stable and can be reused several tens of times without loss of efficiency. This ceramic form can withstand high pressures, very high pH, very fast flows and organic solvents.

Hydroxyapatite ceramic column chromatography is a particular type of chromatography that is neither an affinity chromatography nor an ion exchange in the strict sense. It prints its properties in these two types of chromatographies and could be defined as a pseudo-affinity and a pseudo ion exchange.

The nucleic acids bind to the hydroxyapatite by virtue of interactions between the phosphate groups of the polynucleotide backbone and the calcium residues of the support. The nucleic acids can be eluted differentially by varying the ionic strength of phosphate buffers. Nucleic acids can thus be separated from proteins and between these, the DNA of RNA and the DNA of single strands of double-stranded DNA. The RNAs are those that bind in the least solid way and can be eluted with a relatively weak ionic strength buffer. Single-stranded DNAs also bind less strongly than double-stranded DNAs that bind more solidly to the support and need a stronger buffer.

The biological material in a phosphate buffer of weak ionic strength was deposited in the column. Nucleic acids DNA and RNA were fixed. A second buffer, of higher ionic strength, was used immediately to elute the RNA that was almost completely eliminated at this stage. A third superior ionic strength buffer was used to elute the double-stranded DNA that was recovered. The use of hydroxyapatite in the method of the invention makes it possible to recover double-stranded DNA having a very high degree of purity.

As indicated above, a preferred embodiment of the invention further comprises a triple helix affinity chromatography step.

Triple-helical affinity chromatography consists in passing the solution obtained in a support in which an oligonucleotide capable of hybridizing a triple helix with a specific sequence present in the DNA to be purified is covalently coupled (W096 / 18744).

The specific sequence may be a sequence naturally present in the double-stranded DNA, or a synthetic sequence artificially introduced therein. The oligonucleotides used in the present invention are oligonucleotides that hybridize directly with double-stranded DNA. These oligonucleotides may contain the following bases: - thymidine (T), which is capable of forming triplets with the A.t doublets of double-stranded DNA (Rajagopal et al, Biochem 28 (1989) 7859); - adenine (A), which is capable of forming triplets with the A.T doublets of double-stranded DNA; - guanine (G), which is capable of forming triplets with the G.C doublets of double-stranded DNA; - protonated cytosine (C +), which is capable of forming triplets with the G.C doublets of double-stranded DNA (Rajagopal et al precipitated); - Uracil (U) which is capable of forming triplets with base pairs A.U or A.T.

Preferably, the oligonucleotide used comprises a homopyrimidic sequence rich in cytosines and the specific sequence present in the DNA is a homopuric-homopyridic sequence. The presence of cytosines allows to have a stable triple helix at acidic pH, where the cytosines are protonated, and unstable at alkaline pH, where the cytosines are neutralized.

To allow the formation of a triple-helix by hybridization, it is important that the oligonucleotide and the specific sequence present in the DNA are complementary. In this regard, to obtain the best yields and the best selectivity, a perfectly complementary oligonucleotide and specific sequence is used in the method of the invention. It can be, in particular, a poly-CTT oligonucleotide and a poly-GAA specific sequence. By way of example, the sequence oligonucleotide 5'-GAGGCTTCTTCTTCTTCTTCTTCTT-3 '(GAGG (CTT) 7; (SEQ ID NO: 1), in which the GAGG bases do not form a triple helix but allow the oligonucleotide of the Coupling arm The sequence (CTT) 7 (SEQ ID No. 2) can also be cited These oligonucleotides are capable of forming a triple helix with a specific sequence containing complementary elements (GAA). a region containing 7, 14 or 17 GAA elements, as described in the examples.

Another sequence of specific interest is the sequence: '-AAGGGAGGGAGGAGAGGAA-3 * (SEQ ID No. 3).

This sequence forms a triple helix with the oligonucleotides '-AAGGAGAGGAGGGAGGGAA-3' (SEQ ID n ° 4) or '-TTGGTGTGGTGGGTGGGTT-3 '(SEQ ID No. 5).

In this case, the oligonucleotide is fixed in an antiparallel orientation in the polyuric strand. These triple helices are not stable except in the presence of Mg2 + (Vasquez et al., Biochemistry, 1995, 34, 7243-7251, Beal et Dervan, Science, 1991, 251, 1360-1363).

As indicated above, the specific sequence may be a sequence naturally present in the double-stranded DNA, or a synthetic sequence artificially introduced therein. It is particularly interesting to use an oligonucleotide capable of forming a triple-helix with a sequence naturally present in double-stranded DNA, for example in the origin of replication of a plasmid or in a marker gene. In this regard, the applicant performed analysis of the plasmid sequence and was able to demonstrate that certain regions of these DNAs, in particular at the origin of replication, possess homopuridic-homopyrimidic regions. The synthesis of oligonucleotides capable of forming triple helices with these natural homopuric-homopyrimidic regions makes it possible advantageously to apply the process of the invention to unmodified plasmids, in particular commercial plasmids of the pUC type, pBR322, pSV, etc. Among the homopyrimidic-homopyrimidic sequences naturally present in a double-stranded DNA, a sequence may be mentioned that contains all or part of the sequence 5'-CTTCCCGAAGGGAGAAAGG-31 (SEQ ID No. 6) present in the ColEl origin of E replication. coli. In this case, the oligonucleotide forming the triple helix possesses the sequence: S'-GAAGGGTTCTTCCCTCTTTCC-S * (SEQ ID No. 7) and is alternatively fixed in the two strands of the double helix, as described by Beal and Dervan ( J. Am. Chem. Soc. 1992, 114, 4976-4982) and Jayasena and Johnston (Nucleic Acids Res. 1992, 20, 5279-5288). Mention may also be made of the sequence 5'-GAAAAAGGAAGAG-3 '(SEQ ID No. 8) of the β-lactamase gene of plasmid pBR322 (Duval-Valentin et al., Proc. Natl. Acad. Sci. USA, 1992, 89 , 504-508). The use of an oligonucleotide capable of forming a triple-helix with a sequence present in an origin of replication or a marker gene is particularly advantageous because it allows, with the same oligonucleotide, to purify all the DNA containing said origin of replication or said marker gene. Accordingly, it is not necessary to modify the plasmid or double-stranded DNA to incorporate an artificial specific sequence.

Although perfectly complementary sequences are preferred it is understood however that certain unequal matings can be tolerated between the sequence of the oligonucleotide and the sequence present in the DNA, when they do not lead to a very large loss of affinity. Mention may be made of the sequence 51-AAAAAAGGGAAlAAGGG-3 '(SEQ ID No. 9) present in the β-lactamase gene of E_j. coli In this case, the thymine that interrupts the polyuric sequence can be recognized by a guanine from the third strand, thus forming a triplet ATG that is stable when it is framed by two TAT triplets (Kiessling et al., Biochemistry, 1992, ¿1, 2829 -2834).

According to a particular embodiment, the oligonucleotides of the invention comprise the sequence (CCT) n, the sequence (CT) n or the sequence (CTT) n, in which n is an integer comprised between 1 and 15 inclusive. It is particularly advantageous to use sequences of type (CT) n or (CTT) n. The Applicant demonstrated in effect that the purification performance was influenced by the amount of C in the oligonucleotide. In particular, as indicated in example 7, the purification performance increases when the oligonucleotide contains fewer cytosines. It is understood that the oligonucleotides of the invention can also combine elements (CCT), (CT) or (CTT).

The oligonucleotide used can be natural (composed of natural, unmodified bases) or chemically modified. In particular, the oligonucleotide can advantageously exhibit certain chemical modifications that increase its resistance or protection against nucleases, or its affinity for the specific sequence.

According to the present invention, oligonucleotide is also understood to be any chain of nucleosides that have undergone a modification of the skeleton with the purpose of making it more resistant to nucleases. Among the possible modifications that can be mentioned are the oligonucleotides phosphorothioates which are capable of forming the triple helices with the DNA (Xodo et al., Nucleic Acids Res., 1994, 22, 3322-3330), as well as the oligonucleotides which possess skeletons of formacetal or methylphosphonate (Matteucci et al., J. Am. Chem. Soc., 1991,] __., 7767-7768). Oligonucleotides synthesized from nucleotide α-anomers can also be used, which also form triple helices with the DNA (Le Doan et al., Nucleic Acids Res., 1987, 1¿, 7749-7760). Another modification of the skeleton is the binding of phosphoramidate. Mention may be made, for example, of the internucleotide linkage N3'-P5 'phosphoramidate described by Gryaznov and Chen, which give oligonucleotides which form with the DNA particularly stable triple helices (J. Am. Chem. Soc., 1994, 116. 3143-3144) . Among other modifications of the skeleton, one can also mention the use of ribonucleotides, of 2'-O-methylribose, of phosphodiester, ... (Sun et Héléne, Curr Opinion Struct. Biol., 116. 3143-3144). The phosphorated skeleton can finally be replaced by a polyamide skeleton as in the PNA (Peptid Nucleic Acid), which can also form triple helices (Nielsen et al., Science, 1991, 254. 1497-1500; Kim et al., J Am. Chem. Soc., 1993, 115. 6477-6481)) or by a guanidine-based skeleton, as in the DNG (deoxyribonucleic guanidine, Proc. Natl. Acad. Sci. USA, 1995, __, 6097- 6101), polycationic analogs of DNA, which also form triple helices.

The thymine of the third strand can also be replaced by a 5-bromouracil, which increases the affinity of the oligonucleotide for the DNA (Povsic et Dervan, J. Am. Chem. Soc, 1989, 111. 3059-3061). The third strand may also contain non-natural bases, among which may be mentioned 7-deaza-2'-deoxyxantosine (Milligan et al., Nucleic Acids Res., 1993, 21, 327-333), 1- (2 -deoxy-β-D-ribofuranosyl) -3-methyl-5-amino-1H-pyrazolo [4,3-] pyrimidin-7-one (Koh et Dervan, J. Am. Chem. Soc., 1992, 1, 1470-1478), 8-oxoadenine, 2-aminopurine, 2'-0-methyl-pseudoisocitidine, or any modification known to the person skilled in the art (see for review Sun et Héléne, Curr.

Opinion Struct. Biol., 1993, 3_, 345-356).

Another type of oligonucleotide modification is aimed more particularly at improving the interaction and / or the affinity between the oligonucleotide and the specific sequence. In particular, a completely advantageous modification according to the invention consists in ethylating the cytosines of the oligonucleotide. The oligonucleotide thus methylated has the remarkable property of forming a stable triple helix with the specific sequence in areas of pH closer to neutrality (= 5). Thus it allows to work at higher pH than the oligonucleotides of the prior art, that is to say at pH where the risks of degradation of the plasmid DNA are much lower.

The length of the oligonucleotide used in the method of the invention is at least 3 bases, and preferably comprises between 5 and 30. Advantageously, an oligonucleotide with a length greater than 10 bases is advantageously used. The length can be adapted on a case-by-case basis by the person skilled in the art depending on the selectivity and stability of the interaction sought.

The oligonucleotides according to the invention can be synthesized by any known technique. In particular, they can be prepared by means of nucleic acid synthesizers. Any other method known to the person skilled in the art may well be used.

To allow its covalent coupling in the support, the oligonucleotide is generally functionalized. Thus, it can be modified by a terminal thiol, amine or carboxyl group, in position 5 'or 3'. In particular, the addition of a thiol, amine or carboxyl group makes it possible, for example, to couple the oligonucleotide to a support having disulfide, maleimide, amine, carboxyl, ester, epoxide, cyanogen bromide or aldehyde functions. These couplings are formed to establish disulfide, thioether, ester, amide or amine bonds between the oligonucleotide and the support. Any other method known to the person skilled in the art can be used, such as bifunctional coupling reagents, for example.

On the other hand, to improve the hybridization with the coupled oligonucleotide, it may be advantageous if the oligonucleotide contains an "arm" and a "spacer" base sequence. The use of an arm in fact allows the oligonucleotide to be fixed at a chosen distance from the support allowing its interaction conditions with the DNA to be improved. The arm is advantageously constituted by a linear carbon chain, which contains 1 to 18, and preferably 6 or 12 groups (CH2), and of an amine that allows attachment to the column. The arm meets a phosphate of the oligonucleotide or a "spacer" composed of bases that interfere with the hybridization. Thus, "the spacer" can include the pyrrhic bases. By way of example, "the spacer" may comprise the GAGG sequence. The arm is advantageously composed of a linear carbon chain containing 6 or 12 carbon atoms.

To use the present invention, different types of supports can be used. They may be functionalized, bulk or preconditioned column chromatography supports, functionalized plastic surfaces or functionalized latex beads, magnetic or not. It is preferably chromatography supports. By way of example, the chromatography supports that can be used are agarose, acrylamide or Dextran as well as their derivatives (such as Sephadex, Sepharose, Superose, ...), polymers such as poly (styrenedivinylbenzene), or the inserted or non-inserted silica, for example. The chromatography columns can operate in diffusion or perfusion mode.

To obtain a better purification performance, it is particularly advantageous to use, in the plasmid, a sequence containing several hybridization positions with the oligonucleotide. The presence of several hybridization positions indeed favors the interactions between said sequence and the oligonucleotide, which leads to improved purification performances. So for an oligonucleotide that contains n repeats of elements (CCT), (CT) or (CTT), it is preferable to use a DNA sequence containing at least n complementary elements and, preferably, n + l complementary elements. A sequence having n + l complementary elements thus offers two positions of hybridization in the oligonucleotide. Advantageously, the DNA sequence contains up to 11 hybridization positions, ie n + 10 complementary elements.

According to another embodiment, the ceramic hydroxyapatite column chromatography is followed or preceded by an anion exchange column chromatography step. A weak anion exchange column is preferably used. Strong anions have the property of fixing the DNA very strongly, so strongly that it is very difficult to recover the product (the yield is then less than 60%). This is why the applicant uses weak anion exchangers that do not retain the plasmid DNA but that bind the residual RNA.

As indicated above, the process according to the invention advantageously comprises a diafiltration step. Diafiltration is a stage of concentration of the sample in the course of which water is removed and small molecules (such as salts, proteins and small nucleic acids) present in the clear lysate. The salts are replaced by a phosphate buffer for chromatography. After diafiltration, the solution is 5 to 50 times more concentrated than the exit solution (the concentration factor depends on the volume of the exit solution).

The use of diafiltration presents several advances. It allows among others to avoid the use of organic solvents such as isopropanol in which the use would require an anti-detonating installation. In addition, this technique is used for very variable volumes. In fact, it is sufficient to increase the surface area of the membranes according to the volume to be treated.

Advantageously, for the diafiltration, an apparatus that serves as a support for a modified polyether sulfone membrane or modified cellulose acetate allows to have a liquid flow of adjustable flow rate. These membranes are defined by their cut-off point, which is at the nominal value the maximum size of the molecules that can pass through said membrane. Related to a real value, a membrane in which the cut-off point is equal to 100 kD allows retaining molecules larger than 30 kD.

A preferred method according to the invention comprises the following steps: diafiltration, Ceramic chromatography hydroxyapatite, and affinity chromatography by specific hybridization between a DNA sequence and an oligonucleotide with formation of a triple helix.

The process according to the present invention can be used to purify all types of double-stranded DNA. It is, for example, circular DNA, such as a plasmid that has in general one or several genes of therapeutic interest. The plasmid can also have an origin of replication, a marker gene, etc ... This method also makes it possible to purify the DNA, linear or circular, having a sequence of interest, from a mixture containing DNA from different sequences.

In general, the output DNA is produced by a host microorganism modified by recombinant DNA techniques. In this regard the host that contains the double-stranded DNA that is sought to recover first multiplies and amplifies everything. To do this, classical fermentation techniques are used to obtain a high cell density. The most commonly used technique is the so-called "fedbatch" which is abundantly described in the literature (Jung et al, Ann.Inst. Pasteur / Microbiol., 1988, 139, pl29-146, Bauer et al., Biotechnol., Bioeng., 1976, 18 , p81-94).

The fermentation is followed by a lysis of cells. In order to lyse the cells, either a mechanical system can be used, either a chemical system following the type of cells referred to or following what is desired to work in the crude lysate or in the clear lysate. For mechanical lysis, systems that do not denature the DNA (agitation, thermal shock, osmotic shock) are preferably used. These methods do not adapt to the extraction of DNA from prokaryotic cells. Indeed, the mechanical treatments used to break the prokaryotic cells denature the DNA. Mechanical lysis is preferably reserved for eukaryotic cells, chemical lysis will be preferred for prokaryotic cells.

The prokaryotic cells are chemically lysed by any technique known to those skilled in the art (detergents, lysozymes, optionally combined with thermal shock, etc.). Preferably, a mixture of soda and SDS is used. During the treatment the pH becomes 12. The pH of the lysate thus obtained is then brought to approximately 6 which causes the precipitation of proteins of a part of the chromosomal DNA and of the RNA. This precipitate is removed by centrifugation.

A preferred embodiment of the invention consists in first subjecting the cells containing the double-stranded DNA to be purified in a chemical lysis which allows obtaining a clear lysate. The clear lysate thus obtained is subjected to a diafiltration and is the concentrate thus obtained which is chromatographed on a ceramic hydroxyapatite column.

The cell lysate may be a lysate of prokaryotic or eukaryotic cells.

In the case of prokaryotic cells, there may be mentioned, for example, the bacteria, O1llr __ subtilis. £ -, _ tvphimurium or Streptomyces. In the case of eukaryotic cells, animal cells, yeasts, fungi, etc., can be cited, and more particularly, Klu? Veromyces or Saccharomvces yeasts or COS, CHO, C127, NIH3T3, etc.

The method of the invention is particularly advantageous since it allows the plasmid DNA of very high purity to be obtained quickly and simply. In particular, as illustrated in the examples, the method allows efficient separation of the plasmid DNA considered contaminating compounds, such as fragmented chromosomal DNA, RNA, endotoxins, proteins, nucleases, etc. More particularly, the method of the invention makes it possible to obtain the preparation of double-stranded DNA, in particular plasmid, practically free of chromosomal DNA (< 0.5%). In addition, the DNA preparations obtained also have a very low endotoxin content (<50 EU / mg), compatible with a pharmaceutical use.

The applicant demonstrated that, in a completely surprising manner, the combination of two steps described above, namely Hydroxyapatite column chromatography followed or preceded by Triple Helical Chromatography, allows to obtain plasmid DNA preparations having a chromosomal DNA content of 0.01. %. Most preferably, the invention also relates to the preparation of plasmid DNA having a chromosomal DNA content less than or equal to 0.01%.

The invention also relates to those of plasmid DNA preparations having an endotoxin content of less than 50 EU / mg, preferably less than 10 EU / mg. The content of endotoxins is therefore well below the authorized content which is 350 EU / injection for a person weighing 70 kg (one EU is an Endotoxin Unit and is equal to 100 pg).

The present invention thus describes the compositions containing the plasmid DNA which can be used pharmaceutically, in particular in gene or cell therapy in vivo or ex vivo. In this regard, the invention also aims at a pharmaceutical composition containing the double-stranded, linear or plasmid DNA, prepared according to the procedure described above.

The compositions may contain plasmid DNA "naked" or associated with transport vectors such as liposomes, nanoparticles, cationic lipids, polymers, recombinant proteins or viruses, etc.

The present application will be described in more detail with the help of the following examples, which should be considered as illustrative and not limiting.

MATERIAL AND METHODS In the experiments that follow, a specific plasmid pXL2784 was used. The plasmid comprises a cassette containing the Cytomegalovirus promoter, the gene coding for luciferase and a homopuric-homopyrimidic sequence (GAA) 17. The construction of the plasmid is described below. It is very evident that the process according to the invention is not limited to the described plasmid.____ Description of plasmid DXL2784 The plasmid pXL2784 was constructed from the plasmid vector pXL2675 (2.513 kb), minimum replicon of the ColEl plasmid derived from the pBluescript plasmid (ORÍ) and having the transposon Tn¿ gene as the selection marker for the kanamycin resistance. Plasmid pXL2784 also contains a homopuric-homopyrimidic sequence (GAA) 17 output of plasmid pXL2563 and which can bind to an oligomer (CTF) n where n = 1 to 17, to locally generate a triple helical structure and allow an affinity purification. Plasmid pXL2784 possesses the cer locus (382 bp) derived from the ColEl plasmid and was cloned into the plasmid pXL565; the cer locus contains a specific site sequence of XerC / XerD recombinases and leads to the resolution of multimers of plasmids. The transgene cloned in this plasmid pXL2784 is an expression cassette (3.3 kb) of the luc gene that codes for the luciferase of Photinus pyralis under the control of the P CMV promoter of the human cytomegalovirus, this cassette comes from the plasmid pXL2622.

The plasmid has a size of 6390 bp. The map of plasmid pXL2784 is presented in Figure 1, and its construction is detailed below. 1 , ? , Víctor ffiinJlffQ Fffi? S7S After having made the Bsal limb transpired by the action of the Klenow fragment, the Bsal-PvuII fragment of 1. 15 kb of plasmid pBKS + (Stratagen) was cloned with the 1.2 kb Smal fragment of plasmid pUC4KIXX (Pharmacia) to generate plasmid pXL2647.

Oligonucleotide 5542: , -AGCTTCTCGA GCTGCAGGAT ATCGAATTCG GATCCTCTAG AGC GGCCGCG AGCTCC-3 '(SEQ ID No. 10) and oligonucleotide 5543: '-AGCTGGAGCT CGCGGCCGCT CTAGAGGATC CGAATTCGAT ATC CTGCAGC TCGAGA-3' (SEQ ID NO. 11) they hybridized to each other and then cloned into the HindIII site of pXL2647 generating the plasmid pXL2675. This plasmid comprises the HindIII multisite. Xhol. PstI. EcoRV EcoRl. BamHl. Xbal. Notl. Sst; I between the origin of replication and the gene that codes for kanamycin resistance.

The CMV promoter contained in the 660 bp MluI-HindIII fragment of pcDNA3 plasmid (which comes from Invitrogen) was cloned between the MluI-HindIII sites of the basic pGL2 plasmid (Promega containing the luciferase gene) to generate the plasmid pXL2622. 1. 4. Plaamide »PXL2563 and PMTL22-TH suß contain one -K-E-3fi9-K-KsS-a-CJB ---- B - .------- &- ^^ oliponuclaotide.

Oligonucleotide 4817: '-GATCCGAAGA AGAAGAAGAA GAAGAAGAAG AAGAAGAAGA A GAAGAAGAA GAAGAAGG-3 '(SEQ ID N ° 12) and oligonucleotide 4818: * -AATTCCTTCT TCTTCTTCTT CTTCTTCTTC TTCTTCTTCT TCTTCT TCTT CTTCTTCG-3 '(SEQ ID N ° 13) they hybridized between them and cloned in the sites EcoRI and BamHl of plasmid pBluescriptII KS to form plasmid? XL2563. The 62 bp EcoRI-BamHI fragment was cloned into the EcoRI-BamHI sites of plasmid pMTL22 (P. Minton 1988 Gen 68: 139) to generate the plasmid pMTL22-TH. 1. 5. Plá-Wftido »P-SL565 v PXL2781 sue contienan ßl locuß car The 382 bp HpalI fragment of the ColEl plasmid (P-L Biochemicals) was cloned into the AccI site of the plasmid M13 mp7 (Messing et al., 1981 Nucleic Acids Res 9: 309) to form the plasmid pXL565. The 382 bp BamH1 fragment of? XL565 was then cloned into the BslII site of plasmid pSL301 (Invitrogen) to create the plasmid pXL2781. < ------------ w - LJE »Jti-i-wl-K-H-- -M - UP-fc-K-M wSm JKmmL The BamHI-XhoI fragment of the 382 bp plasmid pXL2781 and containing the cer locus was cloned into the BamHI and XhoI sites of the plasmid pXL2675 to create the plasmid pXL2782.

The BalII-BamHI fragment of the 62 bp pMTL22-TH plasmid containing the sequence (GAA) 17 was cloned into the BamH1 site of the plasmid pXL2782 to form the plasmid pXL2783.

At the end, the 3.3 kb Sall-Spel fragment of the plasmid pXL2622 and containing the luciferase cassette was cloned into the Xhol and Nhel sites of the plasmid pXL2783 to create the plasmid pXL2784. It is well understood that any other cassette for the expression of a gene can be inserted in the place of the luciferase cassette.

The DH1 strain (Maniatis et al., 1989) containing this plasmid was cultured in a fermenter of 2, 7 and up to 800 liters. Other strains can also be used. 2. Fermentation The host containing the plasmid DNA to be cultured can be obtained by classical fermentation techniques (Jung et al Ann.Inst.Pasteur / Microbiol., 1988, 139, pl29-146; Bauer et al. Biotechnol. Bioeng., 1976, 18, p81-94) the batch feeding technique is preferred. After fermentation, the cells are recovered, on a laboratory scale, that is to say for volumes lower than 5 1, by classical centrifugation (20 mn at 10,000 rpm) or by continuous centrifugation for larger volumes (industrial volumes that can go up to several hundreds of liters). The cells thus recovered can be used completely immediately or frozen at -80 ° C. 3. Chemical lysia (light lyse) The cells are thawed, if necessary, and then lysed. Chemical lysis is broken down into three stages. The first consists of suspending the cells in a buffer Tris 25mM pH 6.8, glucose 50mM, ETDA lOmM or equivalent. The lysis of the cells is then carried out in a mixture containing 0.2M NaOH and 1% SDS. The pH of the solution is about 12. The selection of the ionic detergent imposes, in effect a non-ionic detergent giving the extraction yields 10 times lower. The lysis is followed by a pseudo-neutralization of the medium in the presence of potassium acetate (the final pH of the solution is between 5.5 and 6). This acidification of the medium leads to the appearance of a precipitate that contains the proteins, a part of the chromosomal DNA and the RNA. This precipitation is due to the reaction of sodium dodecyl sulfate (SDS) with potassium acetate which form a white precipitate of potassium dodecyl sulfate.

The precipitate must be removed. To do this we proceed by centrifugation in jars (15 min, 8000 rpm) if the volumes are less than 5 liters or by continuous centrifugation if the volumes are larger (> 5 liters). Another method to eliminate the supernatant is to carry out a filter filtration with a depth of porosity greater than or equal to 20 μm (PALL, profile II used according to the manufacturer's specifications). 4. Diafiltration The supernatant recovered after the chemical lysis undergoes a diafiltration in order to concentrate the plasmid DNA and to eliminate the molecules of small molecular weights, in particular the salts that occur in high concentrations. This diafiltration is done in membrane of cut-off point between 50 and 300 kD following the size of the plasmids. Preferably, a lOOkD cut-off membrane is used. The value of 100kD is a nominal value given by the proteins that are the globular molecules. It is considered that for the nucleic acid molecules, which have a different spatial structure, all molecules having a molecular weight less than 30kd are eliminated. The amount of DNA present in the solution after diafiltration and the amount present in the clear lysate is measured by HPLC. The ratio thus determined gives the performance of this stage that is greater than or equal to 80%.

During the course of this diafiltration, the salts are eliminated. They are replaced by a lOmM phosphate buffer.

Thus it is possible to apply the product directly on a chromatography column, in particular Ceramic Hydroxyapatite ™.

Plasmid DNA from triple-helical affinity chromatography was diafiltered again in order to concentrate the sample and remove the undesirable salts.

This allows to balance the product in the appropriate formulation buffer. For this, diafiltration was carried out on a membrane with a cut-off point between 10 and 50kD. The yield is higher than 80%.

The product was then sterile filtered and subjected to analysis before formulation.

. Hydroxyapatite ™ ceramic column chromatography Hydroxyapatite ™ Ceramic gel is immersed in a column of appropriate size following the volume of the sample to be purified and according to the purity of the initial sample. To determine the size of the column and the volume of the gel, the amount in mg / ml of DNA present in the initial solution is measured by HPLC. It is estimated in effect that at least 0.1 mg of DNA are fixed per ml of hydroxyapatite this value can vary up to 1 mg is seen more depending on the amount of RNA present in the initial solution. The RNA is fixed in the gel and as the amount of RNA is important less DNA can be fixed. The RNA was removed by differential elution. The column was equilibrated in phosphate buffer of weak ionic strength (10 mM). The sample was deposited on the gel with a linear flow of 50 cm / h. The gel was then subjected to a wash with a higher conductivity phosphate buffer (150 mM). Most of the RNA contained in the sample was removed at this stage. The plasmid DNA was eluted again increasing the conductivity of the phosphate buffer (250mM). The last contaminants were eliminated by application of 0.5N NaOH that was neutralized with the high molarity phosphate buffer (500mM) before the optional reuse of the column. In the case of a pharmaceutical production, this support has the advantage of being able to undergo chemical decontamination in the place since it resists 0.5 M soda, a classic washing agent in chromatography, but also at high concentrations of ethanol.

The resolution of ceramic hydroxyapatite is excellent. This stage of the procedure allows to eliminate more than 80% of RNA, 99.9% of chromosomal DNA and to decrease the content of endotoxins by a factor of 1000. In addition this technology avoids the use of all enzymes of bovine or other origin (neither Rnasa, nor proteinase K), in addition its resistance to chemical agents has allowed to use it nowadays more than 40 times without reproducibility problem. The yield of chromatography is greater than or equal to 80%. 6. Chromatography of affinity with formation da vina tripla helix. 6. 1. Preparation of the column Materjal. The column used is a HiTrap column activated with NHS (N-hydroxysuccinimide, Pharmacia) of 5 ml, connected to a peristaltic pump (flow < ml / min). The specific oligonucleotide used has a 5 'NH2 group.

The dampers used in this example are the following: - Coupling damper: NaHC03 0.2 M, NaCl 0.5 M, pH 8.3.

- Shock absorber A: 0.5 M ethanolamine, 0.5 M NaCl, pH 8.3.

- Shock absorber B: 0.1 M acetate, 0.5 M NaCl, pH 4.

Method: The column was washed with 30 ml of 1 mM HCl, and then the oligonucleotide was diluted in the coupling buffer (250 nmol in 5 ml) was applied to the column and left for 30 minutes at room temperature. The column was washed 3 successive times with 30 ml of buffer A and then 30 ml of buffer B. The oligonucleotide was thus bound covalently to the column with a CONH binding. The column was stored at 4 ° C and could be used at least four times. § »2, Pyrífi? Acjfn < faith? pl £ $ miio Material : The plasmid pXL2784 (described in 1) was purified on the HiTrap column coupled to the oligonucleotide described in 7.1. The buffers used in this purification are the following: Shock absorber F: 2M NaCl, 0.2 M acetate, pH 4.5.

Shock absorber E: Tris 1 M, HCl pH 9, EDTA 0.5 mM.

Method: The column was washed with buffer F, and then the solution containing the plasmid was applied to the column and incubated for at least two hours at room temperature. The column was washed with buffer F and then the elution was made with buffer E. 7. Ion exchange chromatography.

The pre-purified sample was then subjected to a weak anion exchange column chromatography. In fact, strong anions have the property to bind very strongly to DNA, so strongly that it is very difficult to recover the product (the yield is then less than 60%). This is why the applicant uses the exchange of weak anions that do not retain the plasmid DNA but that fix the residual RNA. An exchange of weak anions of type DEAE Sefarose or DEAE hyper D or equivalents will therefore preferably be used. The gel was equilibrated in lOmM phosphate buffer, the sample that comes from the chromatography stage in Hydroxyapatite Ceramics was applied directly in the gel. The fixed RNA was then removed by applying a concentrated NaCl solution. The chemical decontamination could be done with a 0.5 M soda solution that allows working in good hygiene conditions (elimination of endotoxins and risks of microbial contamination.) 8. Dose of plasmid DNA in complex samples for HPLC The objective of this method is to be able to quantify the plasmid DNA during the different stages of purification in order to determine the yields. In this way, the efficiency of the different operations can be judged quantitatively and qualitatively.

The technique used is the following: The chromatographic support is a Poros R2 gel from Perseptive Biosystems. It is a support of polystyrendivinylbenzene, the size of the particles is 10 μm. The perfusion pore size is from 6000 to 8000 Angstrdms, the size of the diffusion pores is from 500 to 1000. The volume of the gel is 1.7 ml.

It is an ion-pairing chromatography.

The solvent system is water, triethylamine acetate pH 7.1 / 90% triethylamine acetonitrile acetate.

The flow is 3 ml / min. The gradient was defined in order to distinguish the plasmid DNA from the RNA.

The reference sample is a plasmid DNA purified with Qiagen according to the manufacturer's instructions. In an agarose gel, this sample contains only ocDNA and cccDNA. In HPLC, it does not give more than a single peak. Its concentration was determined by measuring its OD at 260 nm and having 1 DO unit = 50 μg / ml DNA as a base.

Thus the increasing amounts of this product were injected in order to effect a range of frame.

The surface of the peaks corresponding to the retention times of the reference DNA was compared to the range. Thus, a quantification could be carried out. 9. Dosage of residual chromosomal DNA The residual genomic DNA was quantified by PCR using primers in the qalK gene of _. coli The sequence of primers of the aalK gene of E. coli is (Debouck et al., Nucleic Acids Res., 1985, i, 1841-1853): '-CCG AAT TCT GGG GAC CAA AGC AGT TTC-3' (SEQ ID No. 14) and 5 '-CCA AGC TTC ACT GTT CAC GAC GGG TGT-3 * (SEQ ID No. 15).

The reaction medium comprises, in the PCR buffer (Promega France, Charbonniéres): 1.5 mM MgCl2; 0.2 mM dXTP (Pharmacia, Orsay); 0.5 μM of primer; 20 U / ml Taq polymerase (Promega). The reaction was carried out following the sequence: - 5 min. at 95 ° C - 30 cycles of 10 sec. at 95 ° C sec. at 60 ° C 1 min. at 78 ° C - 10 minutes. at 78 ° C.

The amplified DNA fragment, 124 base pairs long, was separated by electrophoresis on 3% agarose gel in the presence of SybrGreen I (Molecular Probes, Eugene, USA), and then quantified with reference to a range of Ultrapur genomic DNA from E. coli. strain B (Sigma, ref.D4889).

This method was used to dose the biological activity of the purified plasmid by the process according to the invention. The cells used are NIH 3T3, seeded on the eve of the experiment in 24-well culture plates, at a rate of 50,000 cells / well. The plasmid was diluted in 150 M NaCl and mixed with a lipofectant. A ratio of positive charges of lipofectant / DNA negative charges equal to 3 is used. The mixture was vortexed, left at room temperature for 10 minutes, diluted in the culture medium devoid of calf fetal serum, and then was added to the cells, at a rate of 1 μg of DNA per well of culture. After two hours at 37 ° C, 10% v / v of calf fetus serum was added and the cells were incubated 48 hours at 37 ° C in the presence of 5% C02. The cells were washed twice in PBS and the luciferase activity was measured according to the protocol described (Promega kit, Promega Corp. Madison, Wl), in a Lumat LB9501 luminometer (EG and G Berthold, Evry). The proteins were dosed with the BCA technique (Pierce, Interchim, Asniéres). 11. Various techniques: The plasmid obtained, analyzed by agarose gel electrophoresis and staining with ethidium bromide, is presented in the form of a single "super-coiled" circular DNA band. No trace of high molecular weight (chromosomal) DNA or RNA is detectable in the purified plasmid.

The protein concentration in the samples was measured by Micro-BCA (Pierce) according to the manufacturer's instructions.

The endotoxin concentration was estimated with the dosage of LAL (Biosepra) according to the manufacturer's instructions.

Classical molecular biology methods such as digestion with restriction enzymes, gel electrophoresis, transformation into _. coli the precipitation of nucleic acids etc are described in the literature (Maniatis et al., T., EF Fritsch, and J. Sambrook, 1989. Molecular cloning: a laboratory manual, second edition, Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, New York, Ausubel FM, R. Brent, RE Kinston, DD Moore, J.

A. Smith, J. G. Seidman and K. Struhl. 1987. Current protocols in molecular biology 1987-1988. John Wiley and Sons, New York.). The nucleotide sequences were determined by the chain termination method following the protocol already presented (Ausubel et al., 1987).

Restriction enzymes were made with New-England Biolabs, Beverly, MA (Biolabs).

For ligatures, the DNA fragments were incubated in a buffer 50 mM Tris-HCl pH 7.4, 10 mM MgCl 2, 10 mM DTT, 2 mM ATP, in the presence of T4 phage DNA ligase (Biolabs,).

The oligonucleotides were synthesized using the chemistry of the phosphoramidites protected in β by a cyanoethyl group (Sinha, ND, J. Biernat, J. McManus and H. Kdster, 1984. Polymer support oligonucleotide synthesis, XVIII: Use of β-cyanoethyl-N , -dialkylamino- / N-morpholino phosphoramidite of deoxynucleosides for the synthesis of DNA fragments simplifying deprotection and isolation of the final product Nucí Acids Res., 12, 4539-4557; Giles, JW 1985. Advances in automated DNA synthesis. Biotechnol., Nov. / Dec.) With the Biosearch 8600 automatic DNA synthesizer using the manufacturer's recommendations.

The DNA bound or tested for their transforation efficiency was used to transform the competent strain: fi. coli DH5 [F '/ endAl. I) $ dfil7, ¡g pS 4, -t-Üi-l, recAl. ayrA96. RELAl D (the? .Z? A-? RqF) U169, dgoR, F80dlac (lacZDM15) 1 The mini-preparations of plasmid DNA are made following the protocol of Klein et al., 1980.

The LB culture medium is used for the growth of strains of _. coli (Maniatis et al .-- 1982). The strains were incubated at 37 ° C. The bacteria were exposed to in boxes of LB medium supplemented with the appropriate antibiotics.

Ahem the 1, - PFgparggj-fn dgl lysate Clay Ma eial: The solutions used in this example are the following: Tris 25mM pH 6.8, glucose 50mM, ETDA lOmM: solution 1 0.2M NaOH and 1% SDS: solution 2 3M potassium acetate, pH 5: solution 3 200 g of cells are suspended in 2200 ml of solution 1. Solution 2 (also 2200 ml) was added immediately. At the end, 1100 ml of solution 3 was added. The precipitate formed was then removed by centrifugation at 9000 rpm for 30 min. 5200 ml of supernatant are obtained. 1. 2. Diafiltration Meximana Maximate (Filtron) of cutting point 100 kD of surface 1860 cm2 Shock absorber: 100 mM sodium phosphate pH 6.8 M__Q__: Before use, the membrane was subjected to a chemical decontamination in 0.5 M soda during 1H. The soda was immediately removed with ppi water.

The supernatant obtained in step 1.1 was concentrated approximately 10 times and then diafiltered against 4 volumes of water and then against 4 volumes of 100mM phosphate buffer and pH 6.8. The final volume is 810 mi. The sample then contains 224 mg of plasmid DNA determined by HPLC. 1. 3. Hydroxyapatite ™ Ceramic Purification _______: The buffers used in this purification are the following: Shock absorber A = 10 mM phosphate buffer pH 6.8 Shock absorber B = 150 mM phosphate buffer pH 6.8, Shock absorber C = 250 mM phosphate buffer pH 6.8 Shock absorber D = 500 mM phosphate buffer pH 6.8 0.5M NaOH Method: The column (diameter 113 mm and height 17 cm) contains 1700 ml of gel.

Before use, the gel was subjected to chemical decontamination with 0.5M soda for 1 hour. The soda was removed immediately by application of the shock absorber D. And then, the column was balanced with shock absorber A. 610 ml of gel from the 810 ml (which is 171 mg) obtained above is applied to the gel. The flow is 60 ml / min. The gel was then washed with 6 L of buffer B. The product was then eluted by applying shock absorber C. The volume of eluent is 1520 ml and contains 147 mg of plasmid DNA (determined by HPLC).

The gel was then regenerated by washing with soda (0.5M NaOH) followed by buffer D. The gel was then set for a new cycle.

The set of operations was followed by UV spectrometry at 254 nm. ? t 4, puyiE-Jcflción §n EAE guaros Material : The buffers used in this purification are the following: Shock absorber A, NaCl ÍM and NaOH 0.5M.

Method: The column (diameter 50 mm and height 6 cm) contains 110 ml of gel.

Before use, the gel was subjected to chemical decontamination with 0.5M soda for 1 hour. The soda was removed immediately with a NaCl solution. And then, the column was balanced with cushion A. 1130 ml from the 1520 ml (which is 110 mg) obtained above were applied to the gel with a flow of 50 ml / min. The DNA was not retained, the effluent was collected (1036 ml) and contains 104 mg of DNA. The products retained in the gel were removed immediately with a NaCl solution. The gel was then washed with 0.5M soda followed by NaCl IM. The gel was then placed for a new operation.

The set of operations was followed by UV spectrometry at 254 nm. í-5 P- f traci n M___Jal: Ultrasette membrane (Filtron) cut-off point 30 kD surface 860 cm2 Shock absorber: water ppi Method: Prior to use, the membrane was subjected to chemical decontamination with 0.5M soda during ÍH. The soda was immediately removed with ppi water. 720 ml of product obtained in the previous step were concentrated approximately 3 times and then diafiltered twice against 4 volumes of ppi water. The final volume is 210 ml. The sample then contains 62 mg of plasmid DNA determined by HPLC. 1. 6 DNA characteristics The procedure described above allows obtaining the almost pure plasmid. The different compounds of the final sample were determined and summarized below.

- RNA: not detectable in agarose gel or HPLC - Chromosomal DNA determined by PCR: < 0.5% - Super-coiled DNA determined by HPLC > 80% - Endotoxins (LAL) < 50 EU / mg - proteins (microBCA) < lμg / ml - in vitro biological activity: PXL2784 lot 42DNA95: 20 * 106 RLU / μg of proteins (to be compared with the same plasmid purified in Cesium Chloride gradient = 13 * 106 RLU / μg proteins). 1.7 vríaru-g • The procedure described above was reproduced by performing, in step 1.1, a depth membrane filtration instead of centrifugation. This variant of the process makes it possible to obtain a plasmid of pharmaceutical purity, in which the characteristics are summarized below.

- RNA: not detectable in agarose gel or by HPLC - Chromosomal DNA determined by PCR: < 0.5% - Supercoiled DNA determined by HPLC > 70% - Endotoxins (LAL) < 50 EU / mg - proteins (micro BCA) < 1 μg / ml 2,?, Pre r.a í n,? Te -j column? The column used is a HiTrap column activated with NHS (N-hydroxysuccinimide, Pharmacia) of 5 ml, connected to a peristaltic pump. The specific oligonucleotide used possesses a 5 'NH2 group. Its sequence is the following: S'-GAGGCTTCTTCTTCTTCTTCTTCTT-S1 (SEQ ID No. 1).

The dampers used in this example are the following: Coupling absorber: NaHC030.2 M, 0.5 M NaCl, pH 8.3.

Shock absorber A: 0.5 M ethanolamine, 0.5 M NaCl, pH 8.3.

Shock absorber B: 0.1 M acetate, 0.5 M NaCl, pH 4.

The column was washed with 30 ml of 1 mM HCl, and then the oligonucleotide was diluted in the coupling buffer (250 nmol in 5 ml) was applied to the column and left for 30 minutes at room temperature. The column was washed 3 successive times with 30 ml of buffer A and then 30 ml of buffer B. The oligonucleotide was thus bound covalently to the column with CONH binding. The column was stored at 4 ° C. 2. 2. Purification of the plasmid The shock absorbers used are the following: Shock absorber F: 2M NaCl, 0.2 M acetate, pH 4.5.

Shock absorber E: Tris 1 M, HCl pH 9, EDTA 0.5 mM.

The column was balanced in the shock absorber F, and after 9ml of the hydroxyapatite eluent obtained under the conditions described in example 1.3., Previously adjusted to 2M NaCl and pH 4.5, was applied on a slope in the column overnight at room temperature (flow 0.5 ml / min). The column was washed with buffer F and then elution was made with buffer E. DNA was detected by U.V. spectrometry. at 254 nm. 2. 3. Characteristics of purified DNA The purified DNA was analyzed by HPLC (method described above) is presented as a single peak in a retention time of 24.8 min. No trace of RNA is detectable. Also, after electrophoresis in 1% agarose gel and staining with ethidium bromide, the purified DNA does not present any detectable traces of RNA.

The DNA was also analyzed by anion exchange chromatography on the Gen-Pak Fax Waters column, which separates the relaxed DNA from the supercoiled DNA. The purified sample contains 97% supercoiled DNA against 80% supercoiled DNA in the deposited sample.

The genomic DNA of fi. coli was quantified by PCR according to the technique described in paragraph 3: DNA purified on affinity column contains approximately 0.01% genomic DNA. giwHpio n ° _ 3.1, pcrifiction of plgmido.

An affinity column prepared as described in Example 2 is used with the sequence oligonucleotide: '-CTT CTT CTT CTT CTT CTT CTT-3' (SEQ ID No. 2).

The shock absorbers used are: Shock absorber F: 2M NaCl, 0.2 M sodium acetate, pH 4.5.

Shock absorber E: Tris 1 M, HCl pH 9, EDTA 0.5 mM.

The column was equilibrated with the buffer F, and then 0.8mg of the purified plasmid was deposited according to the protocol of example 1.7, diluted in 10 ml of buffer F. The sample was recirculated in slope in the column overnight at room temperature ( flow 0.5 ml / min). The column was washed with buffer F and after elution was made with buffer E. DNA was detected by U.V. spectrometry. at 254 nm. 3. 2. Characteristics of purified DNA The DNA obtained was analyzed by anion exchange chromatography on the Gen-Pak Fax Waters column, which separates the relaxed DNA from the supercoiled DNA. The purified sample contains 100% supercoiled DNA, against 72% in the sample deposited in the affinity column.

The genomic DNA of fi. coli was quantified by PCR according to the technique described above: the DNA purified on affinity column contains approximately 0.01% of genomic DNA, against approximately 0.3% in the sample deposited on the affinity column. alkylator of hydroxyapatite (PXL 2784) 4. í, prep a tion < faith the cp-i- μiwa $ fini? -ted The column used is a column containing Sepharose 4 Fast Flow activated with NHS (N-hydroxysuccinimide, Pharmacia) and coupled to a sequence oligonucleotide: '-CTT CTT CTT CTT CTT CTT-3 '[. { CTT) 7: SEQ ID No. 2] according to the method described in example 2.1.

The column (diameter 26 mm, height: 16 cm) contains 80 ml of gel and was connected to a peristaltic pump. 4. 2. Purification of the plasmid The shock absorbers used are the following Shock absorber F: 2M NaCl, 0.2 M sodium acetate, pH 4.5.

Shock absorber E: Tris 1 M, HCl pH 9, EDTA 0.5 mM.

The column was equilibrated with buffer F, and then 135 ml which is 8 mg of eluent of hydroxyapatite obtained under the conditions described in example 1.3, previously adjusted to 2M NaCl and pH 4.5, were applied to the column (1.25 ml flow). / min) recirculating four times. The column was washed with buffer F and after elution was made with buffer E. DNA was detected by U.V. spectrometry. at 254 nm: 2.2 mg was recovered. 4. 3. Characteristics of purified DNA The purified DNA analyzed by HPLC (method described above) is presented as a single peak in a retention time of 24.4 min. No trace of RNA is detectable. Also, after electrophoresis in 1% agarose gel and ethidium bromide staining, the purified DNA does not present any detectable traces of RNA.

The DNA was also analyzed by anion exchange chromatography on the Gen-Pak Fax Waters column, which separates the relaxed DNA from the supercoiled DNA. The purified sample contains 100% supercoiled DNA, against 94% of supercoiled DNA in the deposited sample.

The genomic DNA of fi. coli was quantified by PCR according to the technique described in paragraph 3: the DNA purified on affinity column contains approximately 0.02% genomic DNA against 2% of the deposited sample. -ÜaüBlS-S - Purification of a DNA scale .1 Preheat light binding ion The clear lysate was prepared as described in Example 1.1 from a culture of E. coli bacteria transformed by the plasmid pXL2774. The plasmid pXL2774 has a reduced size (approximately 4.5 kb) and comprises in particular: - a cassette expressing the Luc gene (promoter CMV-luc-poly (A) +) - the selection marker sup Phe - the origin of replication ori? of R6K - the col fragment of ColEl M__2_Q: 456 g of cells were suspended in 5000 ml of solution 1. Solution 2 (5500 ml) was added immediately. At the end, 2500 ml of solution 3 was added. The precipitate formed was then removed by centrifugation at 9000 rpm for 30 min or by filtration. 12.3 L of supernatant are obtained. . 2. Diafiltration ______! : Meximana Maximate (Filtron) of cutting point 100 kD of surface 1860 cm2 Shock absorber: 100 mM sodium phosphate pH 6.8 MétQdQ: The sample was diafiltered according to the method described in example 1.2 The final volume is 945 ml. The sample then contains 253 mg of plasmid DNA determined by HPLC. , 3, p h ication in Ce hmi, P o ™ a Ma ial The buffers used in this purification are the following: Shock absorber A = 100 mM phosphate buffer pH 6.8 Shock absorber B = 150 mM phosphate buffer pH 6.8, Shock absorber C = 250 mM phosphate buffer pH 6.8 Shock absorber D = 500 mM phosphate buffer pH 6.8 0.5M NaOH Method: The column (diameter 100 mm and height 23 cm) contains 1700 ml of gel.

Before use, the gel was subjected to chemical decontamination with 0.5M soda for 1 hour. The soda was eliminated immediately by application of the shock absorber D.

And afterwards, the column was balanced with the shock absorber A. 475 ml of the 945 ml (which is 128 mg) obtained above is applied to the gel. The flow is 65 ml / min. The gel was then washed with 6 L of buffer B. The product was eluted immediately by applying buffer C. The volume of eluent is 1760 ml and contains 100 mg of plasmid DNA (determined by HPLC).

The gel is then regenerated by washing with soda (0.5M NaOH) followed by buffer D. The gel is then set for a new cycle.

The set of operations was followed by UV spectrometry at 254 nm .. .4, p The diafiltration was performed according to the protocol described in example 1.5. . 5. DNA characteristics The procedure described above makes it possible to obtain the almost pure plasmid. The different compounds of the final sample were determined and summarized below.

- RNA: not detectable in agarose gel - Chromosomal DNA determined by PCR: 0.6% - Super-coiled DNA determined by HPLC: 87% - Endotoxins (LAL) < 50 EU / mg - proteins (microBCA) < lμg / ml It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

LIST OF SEQUENCES (1) GENERAL INFORMATION: (i) DEPOSITANT: (A) NAME: RHONE POULENC RORER S.A. (B) STREET: 20, AVENUE RAYMOND ARON (C) CITY: ANTONY (E) COUNTRY: FRANCE (F) POSTAL CODE: 92165 (G) TELEPHONE: (1) 40.91.70.36 (H) TELEFAX: (1) 40.91. 72.91 (ii) TITLE OF THE INVENTION: PURIFICATION OF PLASMID DNA OF PHARMACEUTICAL QUALITY (iii) NUMBER OF SEQUENCES: 15 (iv) COMPUTER READING FORM: (A) TYPE OF MEDIA: Tape (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS / MS-DOS (D) PACKAGE: Patentln Relay # 1.0, Version # 1.30 (OEB) (2) INFORMATION FOR SEC ID NO: 1: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 29 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 1: GAGGCTTCTT CTTCTTCTTC TTCTT 25 (2) INFORMATION FOR SEC ID NO: 2: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 21 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 2: CTTCTTCTTC TTCTTCTTCT T 21 (2) INFORMATION FOR SEC ID NO: 3: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 19 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 3: AAGGGAGGGA GGAGAGGAA 19 (2) INFORMATION FOR SEC ID NO: 4: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 19 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 4: AAGGAGAGGA GGGAGGGAA 19 (2) INFORMATION FOR SEQ ID NO: 5: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 19 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 5: TTGGTGTGGT GGGTGGGTT 19 (2) INFORMATION FOR SEQ ID NO: 6: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 19 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 6: CTTCCCGAAG GGAGAAAGG 19 (2) INFORMATION FOR SEQ ID NO: 7: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 21 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 7: GAAGGGTTCT TCCCTCTTTC C 21 (2) INFORMATION FOR SEC ID NO: 8: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 13 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 8: GAAAAAGGAA GAG 13 (2) INFORMATION FOR SEC ID NO: 9: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 17 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 9: AAAAAAGGGA ATAAGGG 17 (2) INFORMATION FOR SEQ ID NO: 10: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 56 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 10: AGCTTCTCGA GCTGCAGGAT ATCGAATTCG GATCCTCTAG AGCGGCCGCG AGCTCC 56 (2) INFORMATION FOR SEQ ID NO: 11: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 56 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 11: AGCTGGAGCT CGCGGCCGCT CTAGAGGATC CGAATTCGAT ATCCTGCAGC TCGAGA 56 (2) INFORMATION FOR SEC ID NO: 12: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 58 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 12: GATCCGAAGA AGAAGAAGAA GAAGAAGAAG AAGAAGAAGA AGAAGAAGAA GAAGAAGG 58 (2) INFORMATION FOR SEQ ID NO: 13: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 58 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 13: AATTCCTTCT TCTTCTTCTT CTTCTTCTTC TTCTTCTTCT TCTTCTTCTT CTTCTTCG 58 (2) INFORMATION FOR SEQ ID NO: 14: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 27 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 14: CCGAATTCTG GGGACCAAAG CAGTTTC 27 (2) INFORMATION FOR SEC ID NO: 15: (i) CHARACTERISTICS OF THE SEQUENCE: (A) LENGTH: 27 base pairs (B) TYPE: nucleotide (C) HEBRA: simple (D) TOPOLOGY: linear (ii) TYPE OF MOLECULE: cDNA (xi) DESCRIPTION OF THE SEQUENCE: SEQ ID NO: 15: CCAAGCTTCA CTGTTCACGA CGGGTGT 27

Claims (13)

1. Purification process of double-stranded DNA of pharmaceutical purity, characterized in that it comprises at least one step of ceramic hydroxyapatite column chromatography.

2. Double-stranded DNA purification process, characterized in that it comprises two chromatography steps of which one is on a hydroxyapatite column.

3. Process according to claim 2, characterized in that it comprises a step of chromatography on a hydroxyapatite column and an affinity chromatography or ion exchange step.

4. Process according to claim 3, characterized in that it comprises a hydroxyapatite column chromatography step and an affinity chromatography step by specific hybridization between a DNA sequence and an immobilized oligonucleotide, with the formation of a triple helix.

5. Process according to claim 3, characterized in that it comprises a step of hydroxyapatite column chromatography and an anion exchange chromatography step.

6. Process according to one of claims 1 to 5, characterized in that it also comprises a diafiltration step.

7. Double-stranded DNA purification process characterized in that it comprises the following steps: - chemical cell lysis, - diafiltration, - Ceramic hydroxyapatite column chromatography, - affinity chromatography by specific hybridization between a DNA sequence and an immobilized oligonucleotide, with the formation of a triple helix.

8. Process according to one of claims 1 to 7, characterized in that the double-stranded DNA also comprises one or more sequences of interest.

9. Process according to any of claims 1 to 8, characterized in that the double-stranded DNA is a plasmid DNA.

10. Preparation of recombinant plasmid DNA, characterized by a chromosomal DNA content less than or equal to 0.01%.

11. Preparation of purified recombinant plasmid DNA according to claim 10, characterized by an endotoxin content less than or equal to 50 EU / mg.

12. Preparation of purified recombinant plasmid DNA according to claim 11, characterized by an endotoxin content less than or equal to 10 EU / mg;

13. Pharmaceutical composition containing a DNA obtained by the process according to one of claims 1 to 9. fifigWgN Pl LA IEVJNX < > H The present invention relates to a process for the purification of pharmaceutical grade plasmid DNA comprising at least one step of hydroxyapatite column chromatography.