Obtaining a functional recombinant anti-rhesus (D) antibody using the baculovirus-insect cell expression system

Expressing of Recombinant VEGFR2-specific Nanobody in Baculovirus Expression System

Background

Baculovirus expression system, introduced more than 20 years ago, is considered as a useful tool for large and complex eukaryotic recombinant protein production. A baculovirus expression vector is a recombinant virus which desired foreign protein coding sequences is under control of the virus gene promoter. Baculovirus only infects insect cells and do not normally infect vertebrates therefore, they possess no risk of biological risks for human.

Objectives

The aim of this study was to recombinant expression of vascular endothelial growth factor (VEGF) reseptor-2 specific Nanobody in the baculovirus expression system.

Materials and Methods

Gene of specific Nanobody against the VEGF reseptor-2 that called 3VGR19 was cloned and expressed in baculovirus system.

Results

3VGR19 Nanobody gene was amplified by Polymerase Chain Reaction (PCR) using the specific primers, and was cloned in pFastBac HTA plasmid. DH10Bac bacteria was transformed with resulted donor plasmid. The cultured Sf9 insect cell line was transfected with recombinant bacmid, and finally, the expression and purification of 3VGR19 was confirmed in insect cells.

Conclusions

In conclusion, Transient infection of insect cells with baculovirus can be a promising technology for expression of antibody fragments.

Expression of recombinant antibodies

Recombinant antibodies are highly specific detection probes in research, diagnostics, and have emerged over the last two decades as the fastest growing class of therapeutic proteins. Antibody generation has been dramatically accelerated by in vitro selection systems, particularly phage display. An increasing variety of recombinant production systems have been developed, ranging from Gram-negative and positive bacteria, yeasts and filamentous fungi, insect cell lines, mammalian cells to transgenic plants and animals. Currently, almost all therapeutic antibodies are still produced in mammalian cell lines in order to reduce the risk of immunogenicity due to altered, non-human glycosylation patterns. However, recent developments of glycosylation-engineered yeast, insect cell lines, and transgenic plants are promising to obtain antibodies with "human-like" post-translational modifications. Furthermore, smaller antibody fragments including bispecific antibodies without any glycosylation are successfully produced in bacteria and have advanced to clinical testing. The first therapeutic antibody products from a non-mammalian source can be expected in coming next years. In this review, we focus on current antibody production systems including their usability for different applications.

Lepidopteran cells, an alternative for the production of recombinant antibodies?

Monoclonal antibodies are used with great success in many different therapeutic domains. In order to satisfy the growing demand and to lower the production cost of these molecules, many alternative systems have been explored. Among them, the baculovirus/insect cells system is a good candidate. This system is very safe, given that the baculoviruses have a highly restricted host range and they are not pathogenic to vertebrates or plants. But the major asset is the speed with which it is possible to obtain very stable recombinant viruses capable of producing fully active proteins whose glycosylation pattern can be modulated to make it similar to the human one. These features could ultimately make the difference by enabling the production of antibodies with very low costs. However, efforts are still needed, in particular to increase production rates and thus make this system commercially viable for the production of these therapeutic agents.

Carbohydrate synthesis and biosynthesis technologies for cracking of the glycan code: recent advances

The glycan code of glycoproteins can be conceptually defined at molecular level by the sequence of well characterized glycans attached to evolutionarily predetermined amino acids along the polypeptide chain. Functional consequences of protein glycosylation are numerous, and include a hierarchy of properties from general physicochemical characteristics such as solubility, stability and protection of the polypeptide from the environment up to specific glycan interactions. Definition of the glycan code for glycoproteins has been so far hampered by the lack of chemically defined glycoprotein glycoforms that proved to be extremely difficult to purify from natural sources, and the total chemical synthesis of which has been hitherto possible only for very small molecular species. This review summarizes the recent progress in chemical and chemoenzymatic synthesis of complex glycans and their protein conjugates. Progress in our understanding of the ways in which a particular glycoprotein glycoform gives rise to a unique set of functional properties is now having far reaching implications for the biotechnology of important glycodrugs such as therapeutical monoclonal antibodies, glycoprotein hormones, carbohydrate conjugates used for vaccination and other practically important protein-carbohydrate conjugates.

Wegener's granuloma harbors B lymphocytes with specificities against a proinflammatory transmembrane protein and a tetraspanin

Wegener's granulomatosis (WG) is a severe autoimmune disorder ranging from localized granulomatous disease to generalised anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis. A previous analysis of immunoglobulin heavy chain genes derived from tissue, i.e. Wegener's granuloma indicated selection and affinity maturation towards local antigen(s). The current study focused on determining the specificity of immunoglobulins from distinct B lymphocytes out of Wegener's granuloma. Four pairs of variable region immunoglobulin light and heavy chain genes, isolated before, were recombinantly expressed using the baculovirus/insect cell system. These immunoglobulins were then analysed for their antigenic target employing a protein macroarray based upon a human fetal brain tissue cDNA expression library. The lysosomal transmembrane protein 9B, a key regulator for TNFα activation, was identified as the putative antigenic target of two immunoglobulins and a tetraspanin, which might play a role in leukocyte activation and motility, was identified as the putative antigenic target of another one. Recombinant monoclonal antibodies out of Wegener's granuloma represent a new tool aiding in elucidation of its and WG immunopathogenesis.

Efficacy of RhD monoclonal antibodies in clinical trials as replacement therapy for prophylactic anti-D immunoglobulin: more questions than answers

Prophylactic anti-D is a very safe and effective therapy for the suppression of D-immunization and prevention of haemolytic disease of the foetus and newborn. The primary mode of action of anti-D is rapid clearance of fetal D-positive red cells from the maternal circulation, mediated by interactions with immunoglobulin G Fc receptors on macrophages in the spleen. Many anti-D monoclonal antibodies (mAb) have been produced by a variety of methods. Twelve anti-D mAbs were tested in eight studies for their ability to mediate clearance of autologous red cells, and 13 antibodies studied in seven trials of the clearance of D-positive red cells injected into D-negative subjects. Antibodies produced by human B-cell lines, mouse-human heterohybridomas and Chinese hamster ovary cells varied in their activity with none being quite as effective as polyclonal anti-D. However, clearance mediated by recombinant anti-D produced by rat YB2/0 cells was extremely rapid, faster than polyclonal anti-D, but with haemolysis and some hepatic accumulation of red cells observed in one study. Two human anti-D mAbs prevented D-immunization. In contrast, anti-D mAbs from heterohybridomas increased the incidence and rapidity of anti-D responses. It is hypothesised that unnatural glycosylation of monoclonal anti-D produced by some cell lines may have caused these unexpected results. In some antibodies, unusual oligosaccharides on anti-D may have affected binding to Fc receptors resulting in reduced red cell clearance. For others, non-human glycoforms of anti-D might have bound to innate immune recognition molecules promoting pro-inflammatory reactions. These extensive data on the clinical activity of monoclonal anti-D produced by cell lines derived from four species will inform the future development of monoclonal anti-D for RhD prophylaxis.

Fully human IgG and IgM antibodies directed against the carcinoembryonic antigen (CEA) Gold 4 epitope and designed for radioimmunotherapy (RIT) of colorectal cancers

BACKGROUND

Human monoclonal antibodies (MAbs) are needed for colon cancer radioimmunotherapy (RIT) to allow for repeated injections. Carcinoembryonic antigen (CEA) being the reference antigen for immunotargeting of these tumors, we developed human anti-CEA MAbs.

METHODS

XenoMouse-G2 animals were immunized with CEA. Among all the antibodies produced, two of them, VG-IgG2kappa and VG-IgM, were selected for characterization in vitro in comparison with the human-mouse chimeric anti-CEA MAb X4 using flow cytometry, surface plasmon resonance, and binding to radiolabeled soluble CEA and in vivo in human colon carcinoma LS174T bearing nude mice.

RESULTS

Flow cytometry analysis demonstrated binding of MAbs on CEA-expressing cells without any binding on NCA-expressing human granulocytes. In a competitive binding assay using five reference MAbs, directed against the five Gold CEA epitopes, VG-IgG2kappa and VG-IgM were shown to be directed against the Gold 4 epitope. The affinities of purified VG-IgG2kappa and VG-IgM were determined to be 0.19 +/- 0.06 x 10(8) M(-1) and 1.30 +/- 0.06 x 10(8) M(-1), respectively, as compared with 0.61 +/- 0.05 x 10(8) M(-1) for the reference MAb X4. In a soluble phase assay, the binding capacities of VG-IgG2kappa and VG-IgM to soluble CEA were clearly lower than that of the control chimeric MAb X4. A human MAb concentration of about 10(-7) M was needed to precipitate approximatively 1 ng 125I-rhCEA as compared with 10(-9) M for MAb X4, suggesting a preferential binding of the human MAbs to solid phase CEA. In vivo, 24 h post-injection, 125I-VG-IgG2kappa demonstrated a high tumor uptake (25.4 +/- 7.3%ID/g), close to that of 131I-X4 (21.7 +/- 7.2%ID/g). At 72 h post-injection, 125I-VG-IgG2kappa was still concentrated in the tumor (28.4 +/- 11.0%ID/g) whereas the tumor concentration of 131I-X4 was significantly reduced (12.5 +/- 4.8%ID/g). At no time after injection was there any accumulation of the radiolabeled MAbs in normal tissues. A pertinent analysis of VG-IgM biodistribution was not possible in this mouse model in which IgM displays a very short half-life due to poly-Ig receptor expression in the liver.

CONCLUSION

Our human anti-CEA IgG2kappa is a promising candidate for radioimmunotherapy in intact form, as F(ab')2 fragments, or as a bispecific antibody.

Balancing GFP reporter plasmid quantity in large-scale transient transfections for recombinant anti-human Rhesus-D IgG1 synthesis

Using transient expression, high amounts (>20 mg/mL) of secreted anti-human Rhesus-D IgG1 were produced in a suspension-adapted HEK293 EBNA cell line (Meissner et al., Biotechnol Bioeng 75: 197-203, 2001). Time of harvest was 3 days after transfection. For the estimation of transfection efficiencies, we routinely co-transfected EGFP reporter DNA. At higher reporter plasmid concentrations, >2% of total transfecting plasmid DNA, a substantial reduction of recombinant antibody synthesis, was observed. This phenomenon was investigated in detail by co-expressing various green fluorescent protein (GFP) reporter constructs, which were targeted at different subcellular locations. Enhanced and humanized GFPs targeted to either the endoplasmic reticulum, the cytosol, or the nucleus reduced recombinant antibody production by 30 to 40% when present at higher concentrations in the transfection solution. The most severe effects were observed when the co-transfected EGFP was targeted to the endoplasmic reticulum, leading to a reduction of up to 80% in the presence of only 5% of reporter DNA. Interestingly, one nuclear-targeted GFP variant that was not codon optimized for expression in human cell lines could be added, to up to almost half of the total amount of transfecting DNA, without adverse effect on antibody production. Although the minimum amount of this reporter DNA needed for fluorescence reading was 10 times higher than for the other variants, it provided a much broader quantity range within which the transfection process could be studied without being negatively affected.

Section 5: Structural/genetic analysis of mAbs to blood group antigens. Coordinator's report

The heavy and light chain immunoglobulin variable region nucleotide sequences for 219 mAbs to human red blood cells were collected from workshop participants, published reports, and Genbank. Information regarding antigen specificity, species of origin, method of cloning, and other relevant serological properties was correlated with the sequence data. Immunoglobulin sequences were analyzed to determine the heavy- and light-chain immunoglobulin genes used and the overall extent of somatic mutation from germline configuration. Approximately 50% of the sequences encoded antibodies with Rh(D) specificity with the remaining sequences encoding mAbs to other Rh-related antigens, antigens of the ABO, MNS, and Kell blood group systems, and several others. Surprisingly, no sequence data were available for mAbs with specificity for a number of common Rh antigens, common Kell antigens, or antigens of the Lewis, Kidd, or Duffy blood group systems. The majority of mAbs were of human origin but included a significant number of macaque mAbs, murine mAbs, and a small number of synthetically-designed recombinant antibodies. Both cellular (EBV-transformation, cell fusion) and molecular (phage display) approaches were used for antibody cloning. Analysis of certain groups of sequences demonstrated patterns of immunoglobulin gene restriction, repertoire shift, and somatic mutation. Analysis of other mAbs demonstrated the value of antibody sequence data for the design and production of novel reagents useful in blood group serology.

Monoclonal anti-D for immunoprophylaxis

Routine antenatal prophylaxis with anti-D has become accepted as desirable, but concerns have been expressed about the adequacies of supply and safety of polyclonal anti-D. Human monoclonal anti-D has been produced using Epstein-Barr virus (EBV)-transformed peripheral B cells, sometimes coupled with fusions to myeloma cell lines. More recently, molecular biology techniques have been used to produce human monoclonal anti-D in a variety of different ways. Many monoclonal antibodies (mAbs) have been characterized for fine specificity and in vitro functional activity in International Workshops. Two mAbs have been shown to cause red cell clearance and immunosuppression in male volunteers. Considerations for the future development of monoclonal anti-D for prophylactic use are reviewed.

A novel patatin-like gene stimulated by drought stress encodes a galactolipid acyl hydrolase

A cDNA (Vupat1) encoding a predicted 43 kDa protein was isolated from drought-stressed cowpea (Vigna unguiculata) leaves. It has homology with patatin, a potato tuber storage protein with lipolytic acyl hydrolase activity. The recombinant protein VUPAT1 expressed in the baculovirus system displays preferentially galactolipid acyl hydrolase activity. Phospholipids are very slowly hydrolyzed and apparently triacylglycerols are not deacylated. Vupat1 promoter contains putative drought-inducible sequences. Northern blots showed that gene expression is stimulated by drought stress and is more pronounced in a drought-sensitive cultivar than in a drought-tolerant one. An involvement in drought-induced galactolipid degradation is proposed for VUPAT1.

Efficient transduction of neural cells in vitro and in vivo by a baculovirus-derived vector

Gene delivery to the central nervous system is central to the development of gene therapy for neurological diseases. We developed a baculovirus-derived vector, the Bac-CMV-GFP vector, containing a reporter gene encoding for the green fluorescent protein (GFP) under the control of the cytomegalovirus (CMV) promoter. Two neuroblastomal cell lines and three human primary neural cultures could be efficiently transduced. In all cases, addition of butyrate, an inhibitor of histone deacetylase, increased the level of expression in terms of the number of GFP-expressing cells and the intensity of fluorescence. The level of expression in a human telencephalic culture was over 50% of transduced cells with a multiplicity of infection of 25. GFP expression was demonstrated to be genuine expression and not pseudotransduction of the reporter protein. Most interestingly, Bac-CMV-GFP could transduce neural cells in vivo when directly injected into the brain of rodents and was not inactivated by the complement system. Thus, baculovirus is a promising tool for gene transfer into the central nervous system both for studies of the function of foreign genes and the development of gene therapy strategies.

V(D)J germline gene repertoire analysis of monoclonal D antibodies and the implications for D epitope specificity

BACKGROUND

The D antigen is a highly immunogenic human RBC antigen. Alloimmunization against the D antigen produces high-affinity antibodies that cause hemolytic transfusion reactions and HDN.

STUDY DESIGN AND METHODS

Cloning and subsequent sequence analysis of 11 new samples of monoclonal anti-D was performed in an attempt to identify V(D)J germline gene usage. Sequences were compared and analyzed with 37 previously published samples of anti-D for identification of V(H) and V(L) pairings, canonical structures, and conformation of restricted germline gene usage.

RESULTS

The V(H) and V(L) pairings used by the new D MoAbs resulted in seven canonical combinations, three of which had not been described previously. Preferential usage of gene segments from the VH3 and VH4 families and of D3, D6, JH6, and DPK9 germline gene segments was also determined. Three samples of anti-D from different donors were found to use similar V(H) and V(kappa) germline genes, despite the fact that two of the antibodies recognized epD6/7 and the third recognized epD1. From the cumulative analysis of the anti-D IgG, 24 V(H) and V(L) gene pairings were identified, resulting in only 10 canonical structures.

CONCLUSIONS

Despite the potential for diversity, only a minority of V(H) and V(L) germline genes are used by anti-D. Consequently, V(H) and V(L) pairings and the resulting canonical structures are similarly restricted.