Cell Expression System

Abstract

An expression system for expressing a protein comprising: a eukaryotic host cell carrying a dihydrofolate reductase (DHFR) deficiency; and an expression vector, the expression vector encoding the human growth hormone gene; a expression vector, the expression vector comprising: a eukaryotic selectable marker including a minimal SV 40 early promoter driving expression of a sequence encoding dihydrofolate reductase for complementing the DHFR deficiency in the host cell; a prokaryotic selectable marker conveying Ampicillin resistance to a prokaryotic host cell; a prokaryotic Origin of Replication; a plurality of multiple cloning sites (MCS); and at least one protein expression module comprising: a Simian Vacuolating Virus 40 (SV40) early promoter, inclusive of its 72 bp enhancer repeats; and a rabbit β-globin intron sequence being separable from a SV40 p A sequence by a first multiple cloning site, for receiving a coding sequence and expressing a desired protein therefrom.

Claims

1. A method for producing a desired recombinant polypeptide comprising culturing a mammalian host cell expressing a desired recombinant polypeptide in the presence of a human Growth Hormone (hGH) or modified hGH, wherein expression of the hGH or modified hGH enhances survival and/or cell density and/or cell viability of the mammalian host cell expressing the desired recombinant polypeptide.

2. The method according to claim 1, wherein the mammalian host cell co-expresses the human Growth Hormone (hGH) or modified hGH and the desired recombinant polypeptide.

3. The method according to claim 1, wherein the hGH is constitutively expressed in the mammalian host cell.

4. The method according to claim 1, wherein the mammalian host cell is a CHO cell.

5. The method according to claim 4, wherein the CHO cell is selected from the group consisting of: a CHO-K1, a CHO-DG44 and a CHO-S cell.

6. The method according to claim 1, wherein culturing is performed in a suspension culture.

7. The method according to claim 1, wherein culturing is performed in an adherent culture.

8. The method according to claim 1, wherein the desired recombinant polypeptide is a biosimilar of a recombinant protein.

9. The method according to claim 8, wherein the recombinant protein is selected from the group consisting of: Infliximab, Adalimumab, Etanercept, Rituximab, Bevacizumab, Trastuzumab, Ranibizumab, Cetuximab, Erythropoietin alpha, Interferon alpha, Interferon alpha 2a and Interferon alpha 2b.

10. The method according to claim 1, wherein the expression of the hGH or modified hGH increase cell density and viability of the host mammalian cell compared to a mammalian cell supplemented with insulin-like growth factor 1 (IGF-1).

11. A recombinant mammalian host cell for producing a desired recombinant polypeptide, wherein a mammalian host cell co-expresses: i) a human Growth Hormone (hGH) or modified hGH, and ii) a desired recombinant polypeptide, wherein expression of the hGH or modified hGH enhances survival of the mammalian host cell and wherein the desired recombinant polypeptide is selected from the group consisting of: Infliximab, Adalimumab, Etanercept, Rituximab, Bevacizumab, Trastuzumab, Ranibizumab, Cetuximab, Erythropoietin alpha, Interferon alpha, Interferon alpha 2a and Interferon alpha 2b.

12. The recombinant mammalian host cell according to claim 11, wherein the hGH is constitutively expressed in the mammalian host cell.

13. The recombinant mammalian host cell according to claim 11, wherein the mammalian host cell is a CHO cell.

14. An expression system for producing a desired recombinant polypeptide comprising: an expression vector comprising a nucleotide sequence encoding a human Growth Hormone (hGH) or modified hGH; an expression vector comprising a nucleotide sequence encoding a desired recombinant polypeptide; and a mammalian host cell used to co-express the hGH or modified hGH and a desired recombinant polypeptide.

15. The expression system according to claim 14, wherein the mammalian host cell is a CHO cell.

16. The expression system according to claim 15, wherein the CHO cell is selected from the group consisting of: a CHO-K1, a CHO-DG44 and a CHO-S cell.

17. The expression system according to claim 16, wherein the CHO cell has a dihydrofolate reductase (DHFR) deficiency.

18. The expression system according to claim 14, wherein the desired recombinant polypeptide is a biosimilar of a recombinant protein.

19. The expression system according to claim 18, wherein the recombinant protein is selected from the group consisting of: Infliximab, Adalimumab, Etanercept, Rituximab, Bevacizumab, Trastuzumab, Ranibizumab, Cetuximab, Erythropoietin alpha, Interferon alpha, Interferon alpha 2a and Interferon alpha 2b.

20. The expression system of claim 18, wherein the recombinant protein is selected from the group consisting of: an antibody that binds tumour necrosis factor, an antibody that binds to a vascular endothelial growth factor, an antibody that binds to HER2, and an antibody that binds to an epidermal growth factor receptor.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0059] FIG. 1A is a plasmid vector map entitled “pNAS-hGH” for the high level expression human growth hormone (hGH) inserted within a pNAS vector with use with NeuCHO cell line;

[0060] FIG. 1B is an expression vector map entitled “pNeu” used for the high level expression of a single chain protein in CHO DG44 cells;

[0061] FIG. 1C is an expression vector map entitled “pNeu-IRES-DHFR” used for the high level expression of a single chain protein in CHO DG44 cells. A dicistronic expression cassette with recombinant gene in 1.sup.st cistron followed by DHFR gene in 2.sup.nd cistron;

[0062] FIG. 1D is an expression vector map entitled “pNeuMAB” used for the high level expression of heavy and light antibody chains and/or recombinant monoclonal antibodies;

[0063] FIG. 1E is an expression vector map entitled “pNeuMAB-IRES-DHFR” used for the high level expression of heavy and light antibody chains;

[0064] FIG. 1F is an expression vector map entitled “pNeuMAB-IRES-DHFR (CMV)” used for the high level expression of heavy and light antibody chains;

[0065] FIG. 1G is a single chain expression vector map entitled “pMAB LC (IRES-DHFR)” used for expression of light chains (LC);

[0066] FIG. 1H is a single chain expression vector map entitled “pMAB HC” used for expression of heavy chains (HC);

[0067] FIG. 2. depicts a growth chart demonstrating viable cell density plotted against time in respect of various cultures and cells used. Growth of DG44 Cell Lines expressing hGH compared to the Parental DG44 Cell Line and a DG44 Cell Line expressing the IGF-1 gene;

[0068] FIG. 3. depicts a graph comparing the integral of viable cell densities against time for various preferred organisms and culture; and

[0069] FIG. 4. depicts a comparison chart showing the relative expression levels of proteins from either CHO DG44 cells or NeuCHO cell lines.

[0070] This specification also includes the following genetic sequence information relating to expression vectors:

[0071] Sequence No. 1 depicts the preferred coding sequence for the expression vector pMAB HC;

[0072] Sequence No. 2 depicts the preferred coding sequence for the expression vector pMAB LC(ires-dhfr);

[0073] Sequence No. 3 depicts the preferred coding sequence for the expression vector pNAS-hGH;

[0074] Sequence No. 4 depicts the preferred coding sequence for the expression vector pNeu;

[0075] Sequence No. 5 depicts the preferred coding sequence for the expression vector pNeu-IRES-DHFR;

[0076] Sequence No. 6 depicts the preferred coding sequence for the expression vector pNeuMAB;

[0077] Sequence No. 7 depicts the preferred coding sequence for the expression vector pNeuMAB-IRES-DHFR (CMV);

[0078] Sequence 8 depicts the preferred coding sequence for the expression vector pNeuMAB-IRES-DHFR;

[0079] Please note that in this specification Sequence No. is same and the equivalent term to SEQ ID NO.

DESCRIPTION OF THE INVENTION

[0080] Preferred embodiments of the invention will now be described with reference to the accompanying drawings and non-limiting examples.

[0081] It has been found that events during the culture of a cell may contribute significantly to the assessment of the risks associated with the use of that particular cell for production of proteins and more particularly proteins for therapeutic use.

[0082] Diligent records of all manipulations including the history of a cell throughout development, extending to the parental cell line from which it was derived, may contribute to the quality and safety of the final product.

[0083] In one scenario, such information may be important for gaining regulatory approval of protein therapeutics expressed from a cell. In particular, biosimilars present unique issues. These issues include demonstrating that immunogenicity of the biosimilar has not been altered with respect to the reference listed drug, as well as ensuring that there are no undetected differences in the product that may potentially impact the safety and efficacy of the drug. Resolving such issues would be problematic without conducting extensive clinical trials. As such, it is likely that any application for a biosimilar would be required to demonstrate that there are no clinically meaningful differences in safety, purity and potency between the biosimilar and the reference listed drug. Moreover, an application for a biosimilar would need to provide evidence that the biosimilar has “profound similarity” (as it is impractical to demonstrate identical biological products) and that the biosimilar will produce the same clinical result as the reference listed drug in any given patient.

[0084] In order to gain regulatory approval, traditional generic manufacturers are required to demonstrate their drug is chemically identical to the referenced listed drug and exhibit the same properties in the human body as the original drug. In regard to biosimilars, it was previously not possible to readily demonstrate that a second-source biologic drug is unequivocally identical to an innovator drug due to the complexities of the synthesis of the drugs in potentially disparate biological systems. As such, biosimilars may exhibit slightly different properties to the original drugs that may necessitate abbreviated clinical trials in order to gain regulatory approval.

[0085] In the context of the present invention, the term “contaminating agent” refers to any agent that can potentially compromise regulatory approval of a product by a regulatory agency. Such agents may include but are not limited to adventitious agents such as viruses, bacteria, fungi and mycoplasma or proteins there from.

[0086] As used herein the term “cell expressed product” refers to any product produced by the cell, including but not limited to proteins, peptides, glycoproteins, carbohydrates, lipids, glycolipids and nucleic acids.

[0087] The term “regulatory approval” in so far as it relates to a product defined in the context of this specification, refers to approval from a regulatory authority which permits marketing of the product.

[0088] The term “safety and effectiveness studies” refers to any studies conducted on a product that assess the safety and efficacy of that product for human and/or animal administration.

[0089] The term “clinical trials” refers to studies involving either animal or humans designed assess the safety and/or efficacy of a product for a therapeutic application.

[0090] The term “abbreviated safety effectiveness studies and/or abbreviated clinical trials” refers to studies carried out on a drug which does not involve complete phase I, II and III clinical trials. Such studies may include a bioequivalence review and a chemistry/microbiology review as defined by the US Food and Drug Administration (FDA).

[0091] The term “biosimilar drug” and ‘biosimilar” refer to a bioequivalent pharmaceutical of a drug in which patent protection has expired and where the previously protected drug has regulatory approval. In particular, this includes products prepared in cell culture by recombinant DNA technology. The term “biosimilar drug” and ‘biosimilar” as used herein is equivalent to the terms “follow-on biologicals” or “biosimilars”.

[0092] The term “protein” refers to a “complete” protein as well as fragments, derivatives or homologs or chimeras thereof comprising one or more amino acid additions, deletions or substitutions, but which substantially retain the biological activity of the complete protein.

[0093] The embodiments of the present invention will now be described by reference to the following non-limiting examples.

Example 1

[0094] Construction of pNeu and pNAS Vectors for High Level Expression of Recombinant Therapeutic Protein

[0095] The vector pNeu was designed for high-level expression of single chain peptides for the production of therapeutic proteins. The vector facilitates the insertion DNA sequences into a convenient multiple cloning site for expression in CHO cells. See Table 1 and FIG. 1A for a description of the vector and its component features.

[0096] The 5026 bp vector encodes essential coding and regulatory sequences for the efficient expression of the recombinant gene as well as essential sequences for the selection and propagation of the plasmid in bacteria. It was designed for chemical synthesis and is void of nonessential and redundant sequences that are common components in commercial expression vectors. This allows for ease of genomic insertion with less likelihood of deletion of sequences during plasmid propagation resulting in loss of expression. The multiple cloning site encodes a minimum of two unique restriction sites for rapid gene cloning.

Example 2

[0097] Synthesis and Cloning of Human Growth Hormone (hGH) cDNA into pNAS

[0098] The amino acid sequence encoding for hGH was subjected to bioinformatic analysis through proprietary third party software by GENEART AG, Regensburg Germany. Codon options were utilized to maximize expression by improving mRNA maintenance and the exploitation of available tRNA pools in CHO cells. RNA and codon optimization was performed on the coding sequences. The gene was analysed with respect to splice site recognition, mRNA stability, presence of ribosomal entry sites, mRNA secondary structures, self-homology for the purpose of increasing gene expression in CHO cells. The hGH gene was cloned into pNAS using AgeI and EcoRV restriction sites using methods well known in the art.

Example 3

[0099] Construction of pNeuMAB Vector for Expression of Recombinant Monoclonal Antibody

[0100] The pNeuMAB vector was designed for the cloning and expression of recombinant monoclonal antibodies. The DNA encoding heavy and light chains are configured in the vector as two distinct and tandem transcription units. See Table 1 and FIG. 1B for a description of the vector and its component features.

[0101] Synthesis of cDNA Encoding Heavy Chain and Light Chain of an Antibody-Infliximab

[0102] The amino acid sequence encoding the heavy chain (HC) and light chain (LC) of the monoclonal antibody, Infliximab were subjected to bioinformatic analysis through proprietary third party software by GENEART AG, Regensburg Germany. Codon options were utilized to maximize expression by improving mRNA maintenance and the exploitation of available tRNA pools in CHO cells. RNA and codon optimization was performed on the coding sequences. The genes were analysed with respect to splice site recognition, mRNA stability, presence of ribosomal entry sites, mRNA secondary structures, self-homology for the purpose of increasing gene expression in CHO cells.

[0103] Cloning Gene Encoding Heavy Chain of Infliximab

[0104] The synthetic gene encoding for the heavy chain of Infliximab was assembled from synthetic oligonucleotides and/or PCR products. The fragment was cloned into pGA14 (ampR) using AscI and PacI restriction sites. The plasmid DNA was purified (Pure Yield™ Plasmid Midiprep, Promega) from transformed bacteria and concentration determined by UV spectroscopy. The final construct was verified by sequencing. The sequence congruence within the used restriction sites was 100%. The synthetic cDNA sequence encoding heavy chain of Infliximab was designed to incorporate unique restriction sites Age I and Eco RV at the 5′ and 3′ ends respectively for directional cloning into the first multiple cloning site of NeuClone's antibody expression vector, pNeuMAB digested with the same restriction sites.

[0105] Cloning Gene Encoding Light Chain of Infliximab

[0106] The synthetic gene encoding the light chain of Infliximab was assembled from synthetic oligonucleotides and/or PCR products. The fragment was cloned into pGA18 (ampR) using AscI and PacI restriction sites. The plasmid DNA was purified (Pure Yield™ Plasmid Midiprep, Promega) from transformed bacteria and concentration determined by UV spectroscopy. The final construct was verified by sequencing. The sequence congruence within the used restriction sites was 100%. The synthetic cDNA sequence encoding light chain of Infliximab incorporates the unique restriction sites Sal I and Mlu I at the 5′ and 3′ ends respectively for directional cloning into the second multiple cloning site of NeuClone's antibody expression vector, pNeuMAB digested with the same restriction sites.

[0107] Generation of NeuCHO

[0108] Transfection of DG44 Cells with pNAS-hGH

[0109] One of the preferred methods by which the expression vector encoding human growth hormone into the host CHO DG44 cell line and the status of the rDNA within the host (copy number, etc.) is as follows. Briefly, a total of 1.5×10 e7 cells were transfected with 1.8 ug of linearized plasmid DNA together with 15 ul of FreeStyle MAX Reagent (Invitrogen) in a volume of 30 ml. The transfected cell cultures were incubated at 37 C, 8% CO2 on an orbital shaker platform. At 48 hours post transfection the cells were cultured in hypoxanthne- and thymidine-deficient, medium supplemented with Gentamycin at a final concentration of 500 ug/ml for selection of uptake of plasmid DNA. Clones were selected by limiting dilution cloning. Several single clones arising from a single cell were expanded and cell lines were characterised for production of human growth hormone. Resulting clones were examined for growth properties in comparison to the standard CHO DG44 cell line.

[0110] Transfection of NeuCHO with pNeuMAB Encoding Infliximab Genes

[0111] Linearized plasmid pNeuMAB DNA encoding Infliximab genes was used to transfect NeuCHO cell cultures At 48 hours post transfection the cells were cultured into hypoxanthne- and thymidine-deficient, medium to select for cells expressing the DHFR gene. A stable cell population was then subjected to subsequent stepwize increasing methotrexate (MTX) concentration (50-, 100-, 200-, 400-, 800 nM, 1 uM) in order to amplifiy template DNA copy number and gene expression. Clones were selected by limiting dilution cloning. Clones with high level expression of infliximab protein were scaled up for protein production.

Example 4

[0112] Cell Banking

[0113] A critical part of quality control involves the full characterization of cells. The cell banks are examined for adventitious agents (viral, bacterial, fungal and mycoplasmal). Documentation describing the type of banking system used, the size of the cell bank(s) the container (vials, ampoules and closure system used, the methods used for preparation of the cell bank(s) including the cryoprotectants and media used, and the conditions employed for cryopreservation and storage are provides.

[0114] The procedures used to avoid microbial contamination and cross-contamination by other cell types present in the laboratory, and the procedures that allow the cell bank containers to be traced are all made available. This includes a description of the documentation system as well as that of a labelling system which can withstand the process of preservation, storage, and recovery from storage without loss of labelling information on the container.

[0115] It is essential that production is based on a well-defined master and working cell bank system. During the establishment of the banks no other cell lines are handled simultaneously in the same laboratory suite or by the same persons. The origin, form, storage, use and expected duration at the anticipated rate of use are described in full for all cell banks.

[0116] The following table identifies some of the components and features of the various expression vectors using with either CHO DG44 or NeuCHO cell lines. The data has been divided into three tables for purposes of presentation in this patent specification.

TABLE-US-00001 TABLE 1 pNeu-IRES- Feature pNeu DHFR pNAS pNeuMAB Multiple cloning One multiple One multiple One multiple Two multiple site cloning site for cloning site for cloning site for cloning sites for insertion of insertion of insertion of insertion of expression unit expression unit expression unit expression units coding for coding for coding for coding for heavy single chain single chain single chain and light chains protein protein protein of a monoclonal antibody Strong The SV40 The SV40 The CMV early The SV40 promoter/enhancer virus early virus early promoter/enhancer virus early combination promoter/enhancer promoter/enhancer drives expression promoter/enhancer of each drives expression transcription of the first and unit 2nd transcription unit Intron/intervening The intron The intron The intron sequence sequence II sequence II sequence II from rabbit from rabbit from rabbit beta globin beta globin beta globin gene is located gene is located gene is located downstream of downstream of downstream of the promoter the promoter the promoter providing for providing for providing for increased increased increased expression and expression and expression and mRNA stability mRNA stability mRNA stability of the of the of the first transcription unit transcription unit transcription unit Intenal Ribosome For the Entry Site (IRES) expression of DHFR gene downstream of 2.sup.nd transcription unit ensuring high level expression of 2.sup.nd cistron in cells growing in the presence of methotrexate Polyadenylation A strong A strong A strong A strong signal polyadenylation polyadenylation polyadenylation polyadenylation signal from signal from signal from S40 signal from S40 S40 virus for S40 virus for virus for virus is for efficient efficient efficient efficient expression of expression of expression of expression of recombinant recombinant recombinant each recombinant gene. gene. gene gene DHFR gene Auxotrophic Auxotrophic Auxotrophic selection in HT selection in HT selection in HT negative media negative media negative media eliminates the eliminates the eliminates the need to maintain need to maintain need to maintain selection selection selection pressure using pressure using pressure using antibiotics. antibiotics. antibiotics. Amplification of Amplification of Amplification of gene copy gene copy gene copy number is number is number is accomplished by accomplished by accomplished by the addition the addition the addition of of methotrexate to of methotrexate to methotrexate to the culture the culture the culture media. The media. The media. The murine DHFR murine DHFR murine DHFR gene is driven gene is driven gene is driven by a minimal by a minimal by a minimal SV40 early SV40 early SV40 early promoter promoter promoter lacking the lacking the lacking the enhancer enhancer enhancer sequence. sequence. sequence Ampicillin For propagation For propagation For propagation For propagation resistance of plasmid in of plasmid in of plasmid in of plasmid in gene bacteria bacteria bacteria bacteria Neomycin For selection in gene mammalian cells

TABLE-US-00002 TABLE 2 pNeuMAB- pNeuMAB-IRES- pMAB-LC (ires- Features IRES-DHFR DHFR(CMV) dhfr) Multiple cloning Two multiple Two multiple One multiple cloning site cloning sites for cloning sites for site for insertion of insertion of insertion of Light chain gene expression units expression units coding for heavy coding for heavy and light chains of and light chains of a monoclonal a monoclonal antibody antibody Strong The SV40 virus early The SV40 virus early The SV40 virus early promoter/enhancer promoter/enhancer promoter/enhancer promoter/enhancer combination drives expression drives expression drives expression of of the first of the first gene LC gene and 2nd genes and the CMV promoter drives expression of the 2.sup.nd gene. Intron/intervening The intron sequence II The intron sequence II The intron sequence II sequence from rabbit beta from rabbit beta from rabbit beta globin gene is located globin gene is located globin gene is located downstream of the downstream of the downstream of the promoter providing promoter providing promoter providing for increased for increased for increased expression and mRNA expression and mRNA expression and mRNA stability of the stability of the stability of the transcription unit transcription unit transcription unit Intenal Ribosome For the expression For the expression For the expression of Entry Site (IRES) of DHFR gene of DHFR gene DHFR gene downstream of 2.sup.nd downstream of 2.sup.nd downstream of 2.sup.nd transcription unit transcription unit transcription unit ensuring high level ensuring high level ensuring high level expression of 2.sup.nd expression of 2.sup.nd expression of 2.sup.nd cistron in cells cistron in cells cistron in cells growing in the growing in the growing in the presence of presence of presence of methotrexate methotrexate methotrexate Polyadenylation A strong A strong A strong signal polyadenylation polyadenylation polyadenylation signal from S40 signal from S40 signal from S40 virus for efficient virus for efficient virus for efficient expression of expression of expression of recombinant gene. recombinant gene. recombinant gene. DHFR gene Auxotrophic selection Auxotrophic selection Auxotrophic selection in HT negative media in HT negative media in HT negative media eliminates the need to eliminates the need to eliminates the need to maintain selection maintain selection maintain selection pressure using pressure using pressure using antibiotics. antibiotics. antibiotics. Amplification of gene Amplification of gene Amplification of gene copy number is copy number is copy number is accomplished by the accomplished by the accomplished by the addition of addition of addition of methotrexate to the methotrexate to the methotrexate to the culture media. The culture media. The culture media. The murine DHFR gene is murine DHFR gene is murine DHFR gene is driven by a minimal driven by a minimal driven by a minimal SV40 early promoter SV40 early promoter SV40 early promoter lacking the enhancer lacking the enhancer lacking the enhancer sequence. sequence. sequence. Ampicillin For propagation of For propagation of For propagation of resistance gene plasmid in bacteria plasmid in bacteria plasmid in bacteria Neomycin gene

TABLE-US-00003 TABLE 3 Features pMAB-HC Multiple cloning site One multiple cloning site for insertion of Heavy chain gene. Vector is similar to pNAS Strong promoter/enhancer The CMV early promoter/enhancer drives combination expression of heavy chain gene Intron/intervening sequence Intenal Ribosome Entry Site (IRES) Polyadenylation signal A strong polyadenylation signal from S40 virus for efficient expression of recombinant gene. DHFR gene Ampicillin resistance gene Neomycin gene For selection in mammalian cells

[0117] FIG. 1 A-H depicts a series of expression vector map relevant to expression using CHO DG44 cell lines or NeuCHO cell lines.

[0118] More specifically, FIG. 1A depicts an expression vector pNAS including hGH coding sequence for use in constructing the NeuCHO Cell Line from CHO DG44. Preferably, NeuCHO cell line is produced by the inclusion of the vector shown in FIG. 1A within a CHO-DG44 cell line. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 1.

[0119] It is noted that CHO DG44 cell line includes a relatively and fragile cell line which inherently has issues and problems in regard to long term viability, cell density and population stability.

[0120] In this preferred embodiment, the addition of hGH to the cell culture vector may lead to increases in cell density or production that were previously not realisable using previous techniques and sequences. Previously, growth factors such as IGF-1 and insulin were used to supplement CHO cells (such as DG44). However these previous methods lead to disappointing results in terms of cell viability and/or survival. In the present embodiments, the addition of hGH coding sequences to CHO cells allows for the excretions by the CHO-DG44 cells of hGH. This expression and secretion of hGH into the cell media leads to increase in cell survival of CHO cells.

[0121] Further the expression of hGH may also improve the robustness of the NeuCHO cell line as compared to other CHO cell lines.

[0122] More specifically, the addition of hGH expressing sequences to CHO-DG44 cells gave rise to a new cell line, NeuCHO cell line. The NeuCHO cell line may include any of the expression vectors described and shown in respect to FIGS. 1 A-H.

[0123] The NeuCho cell line, deposited under the provisions of the Budapest Treaty with the Cell Bank Australia located at 214 Hawkesbury Rd, Westmead, NSW, 2145, Australia as of 4 Feb. 2013 and assigned accession no. CBA20130024, as is particularly suitable for use in pharmaceutical manufacture as described within the present application.

[0124] Preferably, the CHO-DG44 cell line was transfected with the pNAS-hGH vector to produce the NeuCHO cell line. Possible transfection methods include: standard methods described in the scientific literature including: calcium phosphate precipitation, PEI, Electroporation and lipofaction. It is generally noted that previous teachings in the field have often argued that it is preferred to deliver higher relative levels of DNA to cells by transfection to get better results. However, transfection methods delivering more DNA into the cell do not generate more stable or high producing cell lines, as the cell lines may become less stable and less robust.

[0125] FIG. 1B depicts an expression vector used for the expression of a single chain protein in CHO DG44 cells. Preferably, the recombinant gene expression may be driven by the SV40 early promoter/enhancer within the vector. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 2.

[0126] FIG. 1C depicts an expression vector used for the expression of a single chain protein in CHO DG44 cells. Preferably, a dicistronic expression cassette with a recombinant gene in the 1.sup.st cistron followed by a DHFR gene in the 2.sup.nd cistron is described in this example. The gene expression in this vector is preferably driven by SV40 early promoter or enhancer. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 3.

[0127] FIG. 1D depicts a pNeuMAB, which is a dual expression vector containing two cloning cassettes to insert heavy and light chain genes into a single vector. This expression vector has two gene expression cassettes for the insertion of multiple recombinant genes. Each cassette includes an SV40 early promoter and downstream poly A sequence. Each gene is driven by driven SV40 promoter without an enhancer sequence. This expression vector is suitable for expression of light and heavy chains expression of the antibodies. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 4.

[0128] FIG. 1E depicts a further expression vector, pNeuMAB-IRES-DHFR, for high level expression of heavy and light chains of a recombinant monoclonal antibody on a single vector driven one SV40 promoter and enhancer. This expression vector may be used for the expression of light and heavy antibody chains. This expression vector generally includes two gene expression cassettes for insertion of recombinant genes. Each cassette consists of SV40 early promoter/enhancer and downstream poly A sequence. Heavy chain and light chain are inserted in 1st and 2nd cassettes respectively. The 2nd cassette is dicistronic having light chain followed by DHFR downstream of IRES. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 5.

[0129] FIG. 1F depicts a further expression vector, pNeuMAB-IRES-DHFR-(CMV), for high level expression of heavy and light chains of recombinant monoclonal antibody on a single vector driven by CMV and SV40 promoters of heavy and light chains of antibodies respectively. The DHFR gene is driven by IRES downstream of light gene; for the expression of heavy and light chains of antibody in opposite orientations with respect to each other. Heavy chain is driven by CMV promoter whereas light chain is driven by SV40 promoter/enhancer. Light chain and DHFR gene have a dicistronic configuration with DHFR downstream of IRES. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 6.

[0130] FIG. 1G depicts a further expression vector, pMAB-LC (ires-dhfr), for expression of only light chains (LC) of antibodies. A discistronic cassette for cloning LC in 1st cistron and DHFR in 2nd cassette downstream of IRES. The vector is used in co-transfection with pMAB HC, which is the expression vector shown in FIG. 1H. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 7.

[0131] FIG. 1H depicts a further expression vector, pMAB-HC, for expression of only heavy chain (HC) of antibodies. Both pMAB-LC and pMAb-HC are co-transfected for expression of complete antibody. The genetic sequence for this expression vector has been submitted along with this application and is designated SEQ. ID No. 8.

[0132] A further graph is shown in FIG. 2. The graph of FIG. 2 represents the: Growth of DG44 Cell Lines expressing IGF-1 or hGH compared to the Parental DG44 Cell Line and a Mock Cell Line. A control (mock) cell line is derived from the Parental Cell Line which has been stably transfected with a DNA plasmid containing the selection marker but without the Gene Of Interest (GOI).

[0133] The preferred NeuCHO Cell Line demonstrates superior growth advantage compared to the original Parental DG44 Cell Line. In this example, the growth of NeuCHO cells demonstrates higher viable cell densities to that of a DG44 Cell Line expressing the IGF-1 gene.

[0134] This graph shows that when DG44 cells express human Growth Hormone, (Line Graphs E and F), the cells have a very high Maximum Viable Cell Density (up to 425%) compared to the untransfected DG44 Parental Cell Line, the Mock transfected Cell Line, and DG44 Cell Lines expressing high or Low IGF-1 protein.

[0135] The NeuCHO Cell Line has an Integral Cell Density of up to 3.67×10.sup.7 cell/day/mL, which is 230% that of the Parental DG44 Cell Line, 1.57×10.sup.7 cell/day/mL.

[0136] Also in FIG. 2, the Viable Cell Density is plotted on the Y-axis in cells/mL, and the number of days in culture is plotted on the X-axis. Six line graphs are shown in the figure, namely line graph A, B, C, D, E and F.

[0137] Line A represents the growth pattern of a parental DG44 cell line that is not transfected with DNA.

[0138] Line B represents the growth pattern of a parental DG44 cell line that was transfected with a DNA plasmid containing the selection marker but without the Gene Of Interest (GOI).

[0139] Line C represents the growth pattern of a parental DG44 cell line that was stably transfected with a DNA plasmid containing both the selection marker and the Gene Of Interest (GOI). The GOI here is Insulin-like growth factor 1 (IGF-1).

[0140] Line D represents the growth pattern of a parental DG44 cell line that was stably transfected with a DNA plasmid containing both the selection marker and the Gene Of Interest (GOI). The GOI here is Insulin-like growth factor 1 (IGF-1).

[0141] Line E represents the growth pattern of a parental DG44 cell line that was stably transfected with a DNA plasmid containing both the selection marker and the Gene Of Interest (GOI). The GOI here is human Growth Hormone (hGH).

[0142] Line F represents the growth pattern of a parental DG44 cell line that was stably transfected with a DNA plasmid containing both the selection marker and the Gene Of Interest (GOI). The preferred GOI in this example is human Growth Hormone (hGH).

[0143] In FIG. 3, a further graph is depicted comparing the integral of viable cell densities (IVCD) of NeuCHO with the standard CHO DG44 cells. This figure demonstrates the difference in the Integral of Viable Cell Densities achieved with the parent cell line NeuCHO compared to parental CHO.

[0144] The NeuCHO cell line is superior in growth capabilities and this translates into a more efficient production process which can minimize costs by having higher productions rates, fewer production runs, thus lower productions costs, lower Cost of Goods (COGS).

[0145] Growth and productivity of NeuCHO cell line expressing a recombinant mAB.

[0146] The preferred NeuCHO cell line demonstrates high titre of mAB x compared to traditional CHO expression system.

[0147] FIG. 5 demonstrates in graphical form that NeuCHO cells may have greater stable transfection efficiency than CHO cells (such CHO DG44 cells). Cells (NeuCHO and CHO) were transfected with DNA encoding mAB ‘x’ prior to selection and single cell cloning from a stable pool. The data is shown in FIG. 5 and demonstrates that stable transfection of NeuCHO cells results in a greater number of clones with high productivity than that of standard CHO cells. The graph shows the levels of various protein expressed in relative quantities at a given time.

[0148] NeuCHO cells have an integral of viable cell density that is about 230% greater than CHO DG44 cell lines. CHO DG44 cell lines expressing insulin like growth factor 1 (IGF-1) do not demonstrate the ability to grow to high cell densities as NeuCHO cell lines may generally achieved. NeuCHO cells have a generally greater transfection efficiency than CHO DG44 cells. The survival rate of transfected NeuCHO cells is generally greater then transfected CHO DG44 cells. Additionally, transfection of NeuCHO cells may result in a greater number of clones with a higher productivity than that of standard CHO DG44 cells.

[0149] Preferably, the expression system and vectors described herein may be able to allow or facilitate CHO cells such NeuCHO or CHO DG44 cells to produce desired proteins suitable for pharmaceutical preparation including, but not limited to: Infliximab tumour necrosis factor (referred to as Remicab™); Adalimumab tumour necrosis factor (referred to as Humira™); Etanercept tumour necrosis factor (referred to as Enbrel™); Rituximab CD20 (referred to as Rituxan™ & MabThera™); Bevacizumab vascular endothelial growth factor (referred to as Avastin™); Trastuzumab HER2 (referred to as Herceptin™); Ranibizumab vascular endothelial growth factor (referred to as Lucentism); Cetuximab epidermal growth factor receptor (referred as Erbitux™); Erythropoietin a; Interferon α-Pegylated interferon alfa-2a; Interferon α-Pegylated interferon alfa-2b and hGH.

[0150] NeuCHO cells when used as feeder layer may also increase efficiency of single cell cloning. NeuCHO cells were seeded in single wells of microtitre plates prior to single cell cloning of a stable transfected pool. Secretion of human growth hormone secreted from NeuCHO cells results in an increased survival rate of single cells following Limiting Dilution Cloning.

[0151] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms, in keeping with the broad principles and the spirit of the invention described herein.

[0152] The present invention and the described preferred embodiments specifically include at least one feature that is industrial applicable.