Simple scale-up of recombinant antibody production using an UCOE containing vector

Use of ubiquitous chromatin opening elements (UCOE) as tools to maintain transgene expression in biotechnology

Amongst the most important outputs of the biopharmaceutical industry are recombinant proteins, many of which are produced by integrating transgenes into the genomes of mammalian cells. However, expression is highly variable and can be unstable during prolonged culture. This is often due to epigenetic mechanisms silencing the transgenes. To combat this problem, vectors have been engineered to include ubiquitous chromatin opening elements (UCOEs) that protect against silencing. Here, we recount the evidence that UCOEs can modify chromatin environments and benefit biomanufacturing.

Effects of ubiquitous chromatin opening element (UCOE) on recombinant anti-TNFα antibody production and expression stability in CHO-DG44 cells

To date, the production of antibodies (mAbs) usually faces the risks of transgene expression reduction and instability, especially after long-time culture. The inclusion of ubiquitous chromatin opening element (UCOE) into expression vectors was reported to enhance protein production and maintain transgene expression stability in CHO cell lines. Thus, we investigate the effects of UCOE on recombinant monoclonal anti-TNFα antibody (mAbTNFα) production and expression stability in CHO-DG44 cells. In our study, non-UCOE and UCOE-based vectors encoding mAbTNFα were constructed and introduced into the CHO-DG44 cells. Cell pools and single-cell clones were obtained by selecting transfected cells with G418, amplifying them by treatment with methotrexate (MTX), and isolating them by limiting dilution. The effects of UCOE on mAb production and stable transgene expression in transfected cells were analyzed via the correlation between mAb yields and mRNA expression level variations, and gene copy number changes. The UCOE pool exhibited higher mAb yield compared to non-UCOE pool. The UCOE was associated with higher transgene transcriptional activity, leading to improvement of mAb production after MTX-mediated gene amplification. The incorporation of UCOE generated cells allowed isolation of greater numbers of positive clones with higher expression. Despite the slightly decreased mAb yield, UCOE clones still retain stable long-term expression in the absence of selective pressure, which was explained by the loss of transgene copies rather than due to the decline of transcriptional activity. In addition, the purified mAb had primary chemical and biological characteristics similar to those of adalimumab. The results showed that the incorporation of UCOE within vectors provides significant advantages in the generation of high-producing clones, enhancement of mAb production, and improvement of gene expression stability.

Enhancement of anti-TNFα monoclonal antibody production in CHO cells through the use of UCOE and DHFR elements in vector construction and the optimization of cell culture media

Recently, there has been a high demand for anti-tumor necrosis factor-α monoclonal antibodies (mAbTNFα) in the treatment of rheumatoid arthritis and other autoimmune diseases. Thus, efficient strategies and stable high-producing cell lines need to be established to increase antibody production. In this study, we describe an efficient approach to establish a mAbTNFα high-producing clone through the optimization of expression vectors and cell culture media. The ubiquitous chromatin opening element (UCOE) and dihydrofolate reductase (DHFR)-based vectors encoding mAbTNFα were introduced into the CHO-DG44 cells using lipofection. Clones were obtained by selecting transfected cells with G418, amplifying them by treatment with methotrexate, and isolating them by limiting dilution. Different media formulated with commercial feeds and media were also screened to develop an improved medium. The antibody produced by the selected clone was purified, characterized, and compared to standard adalimumab. Using our established protocol, a cell clone obtained from stable mAbTNFα-expressing cell pools showed a 3.8-fold higher antibody titer compared to stable cell pools. Furthermore, the highest antibody yield of selected clones cultured in fed-batch mode using improved medium was 2450 ± 30 µg/mL, which was 13.2-fold higher than that of stable cell pool cultivated in batch mode using a basal medium. The purified antibody had primary chemical and biological characteristics similar to those of adalimumab. Therefore, the use of UCOE and DHFR vectors in combination with the optimization of cell culture media may help in establishing stable and high-producing CHO cell lines for therapeutic antibody production.

Improving the expression of anti-IL-2Rα monoclonal antibody in the CHO cells through optimization of the expression vector and translation efficiency

The growing need for monoclonal antibodies (mAbs) necessitates the development of novel and efficient production approaches. Regulatory elements like ubiquitous chromatin-opening elements (UCOEs) have been employed for improvement of the mAb expression in the Chinese hamster ovary (CHO) cells. SINEUPs are a class of long non-coding RNAs, which can improve the translation of partly overlapping mRNAs. A combination of these two elements might lead to higher production of mAbs. Therefore, the current study was conducted to investigate the effects of SINEUPs and A2UCOE on the expression of an IgG1 in the CHO-K1 cells. Hence, after constructing the mAb, mAb-SINEUP, and mAb-UCOE vectors, four stable cell pools were generated through combining the above vectors. According to the expression analysis, antibody yields were higher in the mAb-SINEUP and mAb-UCOE cell pools compared to the mAb cells. In addition, the cells possessing both SINEUP and UCOE elements provided the best expression. Persistent mAb expression was observed for over 2 months in these cells, whilst the expression was decreased in the mAb pool. SINEUP and UCOE positively influenced the stable mAb expression. It can be concluded that the SINEUP and UCOE enhance the antibody stability and expression level separately and their combination improves the mAb production in the CHO cells.

Chromatin-modifying elements for recombinant protein production in mammalian cell systems

Mammalian cells are the preferred choice system for the production of complex molecules, such as recombinant therapeutic proteins. Although the technology for increasing the yield of proteins has improved rapidly, the process of selecting, identifying as well as maintaining high-yield cell clones is still troublesome, time-consuming and usually uncertain. Optimization of expression vectors is one of the most effective methods for enhancing protein expression levels. Several commonly used chromatin-modifying elements, including the matrix attachment region, ubiquitous chromatin opening elements, insulators, stabilizing anti-repressor elements can be used to increase the expression level and stability of recombinant proteins. In this review, these chromatin-modifying elements used for the expression vector optimization in mammalian cells are summarized, and future strategies for the utilization of expression cassettes are also discussed.

Short note: Infliximab recovery in a simulated intestinal fluid of the upper intestine tract

BACKGROUND

The oral administration of Infliximab (IFX) antibody would ensure a direct action on inflamed intestinal tissues without side effects. Thus, investigations about its resilience within the intestinal environment are required.

OBJECTIVE

Quantify the IFX recovery in a simulated upper intestinal environment.

METHODS

IFX was incubated for different times until 120 min in simulated intestinal fluid (SIF) which differed (i) for pH (7.2 vs 6.8, Exp 1), (ii) for addition or not with pancreatin (Exp 2) and (iii) for addition or not with bovine serum albumin in presence of pancreatin (BSA, Exp 3).

RESULTS

In Exp 1 the IFX incubated without pancreatin was degraded by about 15% by SIF pH change from 7.2 to 6.8 and after 120 min it was reduced by about 20%. In Exp 2 the presence of pancreatin determined an intense and rapid IFX degradation (recovery < 33%, within 30 min), but when BSA was added to simulate the presence of food protein (Exp 3) the IFX half-life ranged between 59 and 70 min.

CONCLUSIONS

A discrete in vitro stability of IFX in the upper intestine environment was demonstrated, if food protein is available and competes with pancreatin proteases.

IgE Antibodies: From Structure to Function and Clinical Translation

Immunoglobulin E (IgE) antibodies are well known for their role in mediating allergic reactions, and their powerful effector functions activated through binding to Fc receptors FcεRI and FcεRII/CD23. Structural studies of IgE-Fc alone, and when bound to these receptors, surprisingly revealed not only an acutely bent Fc conformation, but also subtle allosteric communication between the two distant receptor-binding sites. The ability of IgE-Fc to undergo more extreme conformational changes emerged from structures of complexes with anti-IgE antibodies, including omalizumab, in clinical use for allergic disease; flexibility is clearly critical for IgE function, but may also be exploited by allosteric interference to inhibit IgE activity for therapeutic benefit. In contrast, the power of IgE may be harnessed to target cancer. Efforts to improve the effector functions of therapeutic antibodies for cancer have almost exclusively focussed on IgG1 and IgG4 subclasses, but IgE offers an extremely high affinity for FcεRI receptors on immune effector cells known to infiltrate solid tumours. Furthermore, while tumour-resident inhibitory Fc receptors can modulate the effector functions of IgG antibodies, no inhibitory IgE Fc receptors are known to exist. The development of tumour antigen-specific IgE antibodies may therefore provide an improved immune functional profile and enhanced anti-cancer efficacy. We describe proof-of-concept studies of IgE immunotherapies against solid tumours, including a range of in vitro and in vivo evaluations of efficacy and mechanisms of action, as well as ex vivo and in vivo safety studies. The first anti-cancer IgE antibody, MOv18, the clinical translation of which we discuss herein, has now reached clinical testing, offering great potential to direct this novel therapeutic modality against many other tumour-specific antigens. This review highlights how our understanding of IgE structure and function underpins these exciting clinical developments.

Cellular Antisilencing Elements Support Transgene Expression from Herpes Simplex Virus Vectors in the Absence of Immediate Early Gene Expression

Inactivation of all herpes simplex virus (HSV) immediate early (IE) genes to eliminate vector cytotoxicity results in rapid silencing of the viral genome, similar to the establishment of HSV latency. We recently reported that silencing of a nonviral reporter cassette could be overcome in nonneuronal cells by positioning the cassette in the viral latency (LAT) locus between resident chromatin boundary elements. Here, we tested the abilities of the chicken hypersensitive site 4 insulator and the human ubiquitous chromatin opening element A2UCOE to promote transgene expression from an IE-gene-inactivated HSV vector. We found that A2UCOE was particularly active in nonneuronal cells and reduced reporter promoter occupancy by a repressive histone mark. We determined whether multiple transgenes could be expressed under the control of different promoters from different loci of the same virus. The results showed abundant coexpression of LAT-embedded and A2UCOE-flanked genes in nonneuronal cells. In addition, a third reporter gene without known protective elements was active in cultured rat sensory neurons. These findings indicate that cellular antisilencing sequences can contribute to the expression of multiple genes from separate promoters in fully IE gene-disabled HSV vectors, providing an opportunity for therapeutic applications requiring mutually independent expression of different gene products from a single vector.IMPORTANCE Gene therapy has now entered a phase of development in which a growing number of recessive single gene defects can be successfully treated by vector-mediated introduction of a wild-type copy of the gene into the appropriate tissue. However, many disease conditions, such as neurodegeneration, cancer, and inflammatory processes, are more complex, requiring either multiple gene corrections or provision of coordinated gene activities to achieve a therapeutic outcome. Although herpes simplex virus (HSV) vectors have the capacity to meet this need, the challenge has been to genetically engineer the HSV genome in a manner to prevent expression of any viral genes while retaining the ability to express multiple therapeutic transgenes under independent transcriptional control. Here, we show that non-HSV insulator elements can be applied to retain at least transient transgene activity from multiple viral loci, thereby opening the door for more complex gene therapy applications in the future.

Humoral immune responses toward tumor-derived antigens in previously untreated patients with chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL) the occurrence and the impact of antibody responses toward tumor-derived antigens are largely unexplored. Our serological proteomic data show that antibodies toward 47 identified antigens are detectable in 29 out of 35 patients (83%) with untreated CLL. The glycolytic enzyme alpha-enolase (ENO1) is the most frequently recognized antigen (i.e. 54% of CLL sera). We show that ENO1 is upregulated in the proliferating B-cell fraction of CLL lymph nodes. In CLL cells of the peripheral blood, ENO1 is exclusively expressed at the intracellular level, whereas it is exposed on the surface of apoptotic leukemic cells.

From the clinical standpoint, patients with progressive CLL show a higher number of antigen recognitions compared to patients with stable disease. Consistently, the anti-ENO1 antibodies are prevalent in sera from patients with progressive disease and their presence is predictive of a shorter time to first treatment. This clinical inefficacy associates with the inability of patients’ sera to trigger complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity against leukemic cells.

Together, these results indicate that antibody responses toward tumor-derived antigens are frequently detectable in sera from patients with CLL, but they are expression of a disrupted immune system and unable to hamper disease progression.

Targeted Delivery of Neutralizing Anti-C5 Antibody to Renal Endothelium Prevents Complement-Dependent Tissue Damage

Complement activation is largely implicated in the pathogenesis of several clinical conditions and its therapeutic neutralization has proven effective in preventing tissue and organ damage. A problem that still needs to be solved in the therapeutic control of complement-mediated diseases is how to avoid side effects associated with chronic neutralization of the complement system, in particular, the increased risk of infections. We addressed this issue developing a strategy based on the preferential delivery of a C5 complement inhibitor to the organ involved in the pathologic process. To this end, we generated Ergidina, a neutralizing recombinant anti-C5 human antibody coupled with a cyclic-RGD peptide, with a distinctive homing property for ischemic endothelial cells and effective in controlling tissue damage in a rat model of renal ischemia/reperfusion injury (IRI). As a result of its preferential localization on renal endothelium, the molecule induced complete inhibition of complement activation at tissue level, and local protection from complement-mediated tissue damage without affecting circulating C5. The ex vivo binding of Ergidina to surgically removed kidney exposed to cold ischemia supports its therapeutic use to prevent posttransplant IRI leading to delay of graft function. Moreover, the finding that the ex vivo binding of Ergidina was not restricted to the kidney, but was also seen on ischemic heart, suggests that this RGD-targeted anti-C5 antibody may represent a useful tool to treat organs prior to transplantation. Based on this evidence, we propose preliminary data showing that Ergidina is a novel targeted drug to prevent complement activation on the endothelium of ischemic kidney.

Evaluating the expression profile and stability of different UCOE containing vector combinations in mAb-producing CHO cells

Background

As the demand for monoclonal antibodies (mAb) increases, more efficient expression methods are required for their manufacturing process. Transcriptional gene silencing is a common phenomenon in recombinant cell lines which leads to expression reduction and instability. There are reports on improved antibody expression in ubiquitous chromatin opening element (UCOE) containing both heavy and light chain gene constructs. Here we investigate the impact of having these elements as part of the light chain, heavy chain or both genes during cell line development. In this regard, non-UCOE and UCOE vectors were constructed and stable Chinese hamster ovary (CHO) cell pools were generated by different vector combinations.

Results

Expression analysis revealed that all UCOE cell pools had higher antibody yields compared to non-UCOE cells, Moreover the most optimal expression was obtained by cells containing just the UCOE on heavy chain. In terms of stability, it was shown that the high level of expression was kept consistence for more than four months in these cells whereas the expression titers were reduced in the other UCOE pools.

Conclusions

In conclusion, UCOE significantly enhanced the level and stability of antibody expression and the use of this element with heavy chain provided more stable cell lines with higher production level.

Engineering Translation in Mammalian Cell Factories to Increase Protein Yield: The Unexpected Use of Long Non-Coding SINEUP RNAs

Mammalian cells are an indispensable tool for the production of recombinant proteins in contexts where function depends on post-translational modifications. Among them, Chinese Hamster Ovary (CHO) cells are the primary factories for the production of therapeutic proteins, including monoclonal antibodies (MAbs). To improve expression and stability, several methodologies have been adopted, including methods based on media formulation, selective pressure and cell- or vector engineering. This review presents current approaches aimed at improving mammalian cell factories that are based on the enhancement of translation. Among well-established techniques (codon optimization and improvement of mRNA secondary structure), we describe SINEUPs, a family of antisense long non-coding RNAs that are able to increase translation of partially overlapping protein-coding mRNAs. By exploiting their modular structure, SINEUP molecules can be designed to target virtually any mRNA of interest, and thus to increase the production of secreted proteins. Thus, synthetic SINEUPs represent a new versatile tool to improve the production of secreted proteins in biomanufacturing processes.

Evaluating the use of a CpG free promoter for long-term recombinant protein expression stability in Chinese hamster ovary cells

Background

Methylated CpG dinucleotides in promoters are associated with the loss of gene expression in recombinant Chinese hamster ovary (CHO) cells during large-scale commercial manufacturing. We evaluated a promoter devoid of CpG dinucleotides, CpGfree, in parallel with a similar CpG containing promoter, CpGrich, for their ability to maintain the expression of recombinant enhanced green fluorescent protein (EGFP) after 8 weeks of culturing.

Results

While the promoters gave similar transient expression levels, CpGfree clones had significantly higher average stable expression possibly due to increased resistance to early silencing during integration into the chromosome. A greater proportion of cells in clones generated using the CpGfree promoter were still expressing detectable levels of EGFP after 8 weeks but the relative expression levels measured at week 8 to those measured at week 0 did not improve compared to clones generated using the CpGrich promoter. Chromatin immunoprecipitation assays indicated that the repression of the CpGfree promoter was likely linked to histone deacetylation and methylation. Use of histone deacetylase inhibitors also managed to recover some of the lost expression.

Conclusion

Using a promoter without CpG dinucleotides could mitigate the early gene silencing but did not improve longer-term expression stability as silencing due to histone modifications could still take place. The results presented here would aid in promoter selection and design for improved protein production in CHO and other mammalian cells.

Transglutaminase 2-specific coeliac disease autoantibodies induce morphological changes and signs of inflammation in the small-bowel mucosa of mice

Coeliac disease is hallmarked by an abnormal immune reaction against ingested wheat-, rye- and barley-derived gluten and the presence of transglutaminase 2 (TG2)-targeted autoantibodies. The small-bowel mucosal damage characteristic of the disorder develops gradually from normal villus morphology to inflammation and finally to villus atrophy with crypt hyperplasia. Patients with early-stage coeliac disease have TG2-autoantibodies present in serum and small-intestinal mucosa and they may already suffer from abdominal symptoms before the development of villus atrophy. Previously, we have shown that intraperitoneal injections of coeliac patient-derived sera or purified immunoglobulin fraction into mice induce a condition mimicking early-stage coeliac disease. In the current study, we sought to establish whether recombinantly produced patient-derived TG2-targeted autoantibodies are by themselves sufficient for the development of such an experimentally induced condition in immune-compromised mice. Interestingly, mice injected with coeliac patient TG2-antibodies had altered small-intestinal mucosal morphology, increased lamina propria cellular infiltration and disease-specific autoantibodies deposited in the small bowel, but did not evince clinical features of the disease. Thus, coeliac patient-derived TG2-specific autoantibodies seem to be sufficient for the induction of subtle small-bowel mucosal alterations in mice, but the development of clinical features probably requires additional factors such as other antibody populations relevant in coeliac disease.

Thrombin Cleavage of Osteopontin Modulates Its Activities in Human Cells In Vitro and Mouse Experimental Autoimmune Encephalomyelitis In Vivo

Osteopontin is a proinflammatory cytokine and plays a pathogenetic role in multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), by recruiting autoreactive T cells into the central nervous system. Osteopontin functions are modulated by thrombin cleavage generating N- and C-terminal fragment, whose individual roles are only partly known. Published data are difficult to compare since they have been obtained with heterogeneous approaches. Interestingly, thrombin cleavage of osteopontin unmasks a cryptic domain of interaction with α₄β₁ integrin that is the main adhesion molecule involved in lymphocyte transmigration to the brain and is the target for natalizumab, the most potent drug preventing relapses. We produced recombinant osteopontin and its N- and C-terminal fragments in an eukaryotic system in order to allow their posttranslational modifications. We investigated, in vitro, their effect on human cells and in vivo in EAE. We found that the osteopontin cleavage plays a key role in the function of this cytokine and that the two fragments exert distinct effects both in vitro and in vivo. These findings suggest that drugs targeting each fragment may be used to fine-tune the pathological effects of osteopontin in several diseases.

Production of a High-affinity Monoclonal Antibody Reactive with Folate Receptors Alpha and Beta

Folate receptors α (FRα) and β (FRβ) are two isoforms of the cell surface glycoprotein that binds folate. The expression of FRα is rare in normal cells and elevated in cancer cells. Thus, FRα-based tumor-targeted therapy has been a focus area of laboratory research and clinical trials. Recently, it was shown that a significant fraction of tumor-associated macrophages expresses FRβ and that these cells can enhance tumor growth. Although FRα and FRβ share 70% identity in their deduced amino acid sequence, a monoclonal antibody (MAb) reactive with both receptors has not been developed. A MAb that can target both FRα-expressing cancer cells and FRβ-expressing tumor-associated macrophages may provide a more potent therapeutic tool for cancer than individual anti-FRα or anti-FRβ MAbs. In this study, we developed a MAb that recognizes both FRα and FRβ (anti-FRαβ). The anti-FRαβ specifically stained trophoblasts and macrophages from human placenta, synovial macrophages from rheumatoid arthritis patient, liver macrophages from cynomolgus monkey and common marmoset, and cancer cells and tumor-associated macrophages from ovary and lung carcinomas. Surface plasmon resonance showed that the anti-FRαβ bound to soluble forms of the FRα and FRβ proteins with high affinity (KD=6.26×10(-9) M and 4.33×10(-9) M, respectively). In vitro functional analysis of the anti-FRαβ showed that this MAb mediates complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity, and antibody-dependent cellular phagocytosis of FRα-expressing and FRβ-expressing cell lines. The anti-FRαβ MAb is a promising therapeutic candidate for cancers in which macrophages promote tumor progression.

Cell line development for biomanufacturing processes: recent advances and an outlook

At the core of a biomanufacturing process for recombinant proteins is the production cell line. It influences the productivity and product quality. Its characteristics also dictate process development, as the process is optimized to complement the producing cell to achieve the target productivity and quality. Advances in the past decade, from vector design to cell line screening, have greatly expanded our capability to attain producing cell lines with certain desired traits. Increasing availability of genomic and transcriptomic resources for industrially important cell lines coupled with advances in genome editing technology have opened new avenues for cell line development. These developments are poised to help biosimilar manufacturing, which requires targeting pre-defined product quality attributes, e.g., glycoform, to match the innovator's range. This review summarizes recent advances and discusses future possibilities in this area.

Chromatin function modifying elements in an industrial antibody production platform--comparison of UCOE, MAR, STAR and cHS4 elements

The isolation of stably transfected cell lines suitable for the manufacture of biotherapeutic protein products can be an arduous process relying on the identification of a high expressing clone; this frequently involves transgene amplification and maintenance of the clones' expression over at least 60 generations. Maintenance of expression, or cell line stability, is highly dependent upon the nature of the genomic environment at the site of transgene integration, where epigenetic mechanisms lead to variable expression and silencing in the vast majority of cases. We have assessed four chromatin function modifying elements (A2UCOE, MAR X_S29, STAR40 and cHS4) for their ability to negate chromatin insertion site position effects and their ability to express and maintain monoclonal antibody expression. Each element was analysed by insertion into different positions within a vector, either flanking or between heavy chain (HC) and light chain (LC) antibody expression cassettes. Our results clearly show that the A2UCOE is the most beneficial element in this system, with stable cell pools and clones increasing antibody yields 6.5-fold and 6.75-fold respectively. Stability analysis demonstrated that the reduction in antibody expression, seen with cells transfected with the control vector over 120 generations, was mitigated in the clones containing A2UCOE-augmented transgenes. Analysis also showed that the A2UCOE reduced the amount of transgene promoter DNA methylation, which contributed to the maintenance of starting levels of expression.

Structural basis for the recognition in an idiotype-anti-idiotype antibody complex related to celiac disease

Anti-idiotype antibodies have potential therapeutic applications in many fields, including autoimmune diseases. Herein we report the isolation and characterization of AIM2, an anti-idiotype antibody elicited in a mouse model upon expression of the celiac disease-specific autoantibody MB2.8 (directed against the main disease autoantigen type 2 transglutaminase, TG2). To characterize the interaction between the two antibodies, a 3D model of the MB2.8-AIM2 complex has been obtained by molecular docking. Analysis and selection of the different obtained docking solutions was based on the conservation within them of the inter-residue contacts. The selected model is very well representative of the different solutions found and its stability is confirmed by molecular dynamics simulations. Furthermore, the binding mode it adopts is very similar to that observed in most of the experimental structures available for idiotype-anti-idiotype antibody complexes. In the obtained model, AIM2 is directed against the MB2.8 CDR region, especially on its variable light chain. This makes the concurrent formation of the MB2.8-AIM2 complex and of the MB2.8-TG2 complex incompatible, thus explaining the experimentally observed inhibitory effect on the MB2.8 binding to TG2.

A non-complement-fixing antibody to β2 glycoprotein I as a novel therapy for antiphospholipid syndrome

A single-chain fragment variable (scFv) recognizing β2-glycoprotein 1 (β2GPI) from humans and other species was isolated from a human phage display library and engineered to contain an IgG1 hinge-CH2-CH3 domain. The scFv-Fc directed against β2GPI domain I-induced thrombosis and fetal loss, thus mimicking the effect of antibodies from patients with antiphospholipid syndrome (APS). Complement is involved in the biological effect of anti-β2GPI scFv-Fc, as demonstrated by its ability to promote in vitro and in vivo complement deposition and the failure to induce vascular thrombosis in C6-deficient rats and fetal loss in C5-depleted mice. A critical role for complement was also supported by the inability of the CH2-deleted scFv-Fc to cause vessel occlusion and pregnancy failure. This antibody prevented the pathological effects of anti-β2GPI antibodies from APS patients and displaced β2GPI-bound patient antibodies. The CH2-deleted antibody represents an innovative approach potentially useful to treat APS patients refractory to standard therapy.

Optimizing retroviral gene expression for effective therapies

With their ability to integrate their genetic material into the target cell genome, retroviral vectors (RV) of both the gamma-retroviral (γ-RV) and lentiviral vector (LV) classes currently remain the most efficient and thus the system of choice for achieving transgene retention and therefore potentially long-term expression and therapeutic benefit. However, γ-RV and LV integration comes at a cost in that transcription units will be present within a native chromatin environment and thus be subject to epigenetic effects (DNA methylation, histone modifications) that can negatively impact on their function. Indeed, highly variable expression and silencing of γ-RV and LV transgenes especially resulting from promoter DNA methylation is well documented and was the cause of the failure of gene therapy in a clinical trial for X-linked chronic granulomatous disease. This review will critically explore the use of different classes of genetic control elements that can in principle reduce vector insertion site position effects and epigenetic-mediated silencing. These transcriptional regulatory elements broadly divide themselves into either those with a chromatin boundary or border function (scaffold/matrix attachment regions, insulators) or those with a dominant chromatin remodeling and transcriptional activating capability (locus control regions,, ubiquitous chromatin opening elements). All these types of elements have their strengths and weaknesses within the constraints of a γ-RV and LV backbone, showing varying degrees of efficacy in improving reproducibility and stability of transgene function. Combinations of boundary and chromatin remodeling; transcriptional activating elements, which do not impede vector production; transduction efficiency; and stability are most likely to meet the requirements within a gene therapy context especially when targeting a stem cell population.

High-throughput ClonePix FL analysis of mAb-expressing clones using the UCOE expression system

Therapeutic recombinant monoclonal antibodies (mAbs) are commonly produced by high-expressing, clonal, mammalian cells. Creation of these clones for manufacturing remains heavily reliant on stringent selection and gene amplification, which in turn can lead to genetic instability, variable expression, product heterogeneity and prolonged development timelines. Inclusion of cis-acting ubiquitous chromatin opening elements (UCOE™) in mammalian expression vectors has been shown to improve productivity and facilitate high-level gene expression irrespective of the chromosomal integration site without lengthy gene amplification protocols. In this study we have used high-throughput robotic clone selection in combination with UCOE™ containing expression vectors to develop a rapid, streamlined approach for early-stage cell line development and isolation of high-expressing clones for mAb production using Chinese hamster ovary (CHO) cells. Our results demonstrate that it is possible to go from transfection to stable clones in only 4 weeks, while achieving specific productivities exceeding 20 pg/cell/day. Furthermore, we have used this approach to quickly screen several process-crucial parameters including IgG subtype, enhancer-promoter combination and UCOE™ length. The use of UCOE™-containing vectors in combination with automated robotic selection provides a rapid method for the selection of stable, high-expressing clones.

Prevention of arthritis by locally synthesized recombinant antibody neutralizing complement component C5

Treatment of patients suffering from chronic diseases such as rheumatoid arthritis with recombinant antibodies is time consuming and fairly expensive and can be associated with side effects due to generalized depletion of the target molecule. We have addressed these issues by developing an alternative approach consisting of the intraarticular injection of a DNA vector encoding for the anti-C5 neutralizing recombinant miniantibody MB12/22. This method allows local production of the antibody in sufficient amount to be effective in preventing joint inflammation in a rat model of antigen-induced arthritis. Injection of the DNA vector in a right knee of normal rats resulted in the production of the minibody detected in the synovial washes by western blot with a strong signal peaking at 3 days after administration. DNA encoding for the minibody was shown for 14 days in the synovial tissue and was undetectable in the controlateral knee and in other organs. The preventive effect of this approach was evaluated in rats receiving a single injection of the vector 3 days before the induction of antigen-induced arthritis and analyzed 3 days later. The treated rats exhibited a lower increase in swelling, associated with a lower number of PMN in the articular washes and reduced deposition of C9 in synovial tissue compared to control rats. These results suggest that treating the inflamed joints with a vector that induces a local production of a neutralizing anti-C5 antibody may represent a useful strategy to inhibit in situ complement activation and to treat patients with monoarthritis. Moreover, this approach may be adopted as a novel therapeutic strategy to prevent monoarthritis as an alternative to local treatment with antibodies commonly used in this form of arthritis, with the advantages of the lower cost and the longer persistence of antibody production.