Efficient production of human bivalent and trivalent anti-MUC1 Fab-scFv antibodies in Pichia pastoris

Recombinant monoclonal antibody production in yeasts: Challenges and considerations

Monoclonal antibodies (mAbs) are laboratory-based engineered protein molecules with a monovalent affinity or multivalent avidity towards a specific target or antigen, which can mimic natural antibodies that are produced in the human immune systems to fight against detrimental pathogens. The recombinant mAb is one of the most effective classes of biopharmaceuticals produced in vitro by cloning and expressing synthetic antibody genes in a suitable host. Yeast is one of the potential hosts among others for the successful production of recombinant mAbs. However, there are very few yeast-derived mAbs that got the approval of the regulatory agencies for direct use for treatment purposes. Certain challenges encountered by yeasts for recombinant antibody productions need to be overcome and a few considerations related to antibody structure, host engineering, and culturing strategies should be followed for the improved production of mAbs in yeasts. In this review, the drawbacks related to the metabolic burden of the host, culturing conditions including induction mechanism and secretion efficiency, solubility and stability, downstream processing, and the pharmacokinetic behavior of the antibody are discussed, which will help in developing the yeast hosts for the efficient production of recombinant mAbs.

A neutralizing single-domain antibody that targets the trimer interface of the human metapneumovirus fusion protein

IMPORTANCE

Human metapneumovirus (hMPV) is an important respiratory pathogen for which no licensed antivirals or vaccines exist. Single-domain antibodies represent promising antiviral biologics that can be easily produced and formatted. We describe the isolation and detailed characterization of two hMPV-neutralizing single-domain antibodies that are directed against the fusion protein F. One of these single-domain antibodies broadly neutralizes hMPV A and B strains, can prevent proteolytic maturation of F, and binds to an epitope in the F trimer interface. This suggests that hMPV pre-F undergoes trimer opening or "breathing" on infectious virions, exposing a vulnerable site for neutralizing antibodies. Finally, we show that this single-domain antibody, fused to a human IgG1 Fc, can protect cotton rats against hMPV replication, an important finding for potential future clinical applications.

Bispecific antibodies revolutionizing breast cancer treatment: a comprehensive overview

Breast cancer (BCa) is known as a complex and prevalent disease requiring the development of novel anticancer therapeutic approaches. Bispecific antibodies (BsAbs) have emerged as a favorable strategy for BCa treatment due to their unique ability to target two different antigens simultaneously. By targeting tumor-associated antigens (TAAs) on cancer cells, engaging immune effector cells, or blocking critical signaling pathways, BsAbs offer enhanced tumor specificity and immune system involvement, improving anti-cancer activity. Preclinical and clinical studies have demonstrated the potential of BsAbs in BCa. For example, BsAbs targeting human epidermal growth factor receptor 2 (HER2) have shown the ability to redirect immune cells to HER2-positive BCa cells, resulting in effective tumor cell killing. Moreover, targeting the PD-1/PD-L1 pathway by BsAbs has demonstrated promising outcomes in overcoming immunosuppression and enhancing immune-mediated tumor clearance. Combining BsAbs with existing therapeutic approaches, such as chemotherapy, targeted therapies, or immune checkpoint inhibitors (ICIs), has also revealed synergistic effects in preclinical models and early clinical trials, emphasizing the usefulness and potential of BsAbs in BCa treatment. This review summarizes the latest evidence about BsAbs in treating BCa and the challenges and opportunities of their use in BCa.

Yeast-produced fructosamine-3-kinase retains mobility after ex vivo intravitreal injection in human and bovine eyes as determined by Fluorescence Correlation Spectroscopy

Globally, over 2 billion people suffer from vision impairment. Despite complex multifactorial etiology, advanced glycation end products are involved in the pathogenesis of many causative age- and diabetes-related eye diseases. Deglycating enzyme fructosamine-3-kinase (FN3K) was recently proposed as a potential therapeutic, but for further biopharmaceutical development, knowledge on its manufacturability and stability and mobility in the vitreous fluid of the eye is indispensable. We evaluated recombinant production of FN3K in two host systems, and its diffusion behavior in both bovine and human vitreous. Compared to Escherichia coli, intracellular production in Pichia pastoris yielded more and higher purity FN3K. The yeast-produced enzyme was used in a first attempt to use fluorescence correlation spectroscopy to study protein mobility in non-sonicated bovine vitreous, human vitreous, and intact bovine eyes. It was demonstrated that FN3K retained mobility upon intravitreal injection, although a certain delay in diffusion was observed. Alkylation of free cysteines was tolerated both in terms of enzymatic activity and vitreous diffusion. Ex vivo diffusion data gathered and the availability of yeast-produced high purity enzyme now clear the path for in vivo pharmacokinetics studies of FN3K.

A Potential Role for Fructosamine-3-Kinase in Cataract Treatment

Cataracts are the major cause of blindness worldwide, largely resulting from aging and diabetes mellitus. Advanced glycation end products (AGEs) have been identified as major contributors in cataract formation because they alter lens protein structure and stability and induce covalent cross-linking, aggregation, and insolubilization of lens crystallins. We investigated the potential of the deglycating enzyme fructosamine-3-kinase (FN3K) in the disruption of AGEs in cataractous lenses. Macroscopic changes of equine lenses were evaluated after ex vivo intravitreal FN3K injection. The mechanical properties of an equine lens pair were evaluated after treatment with saline and FN3K. AGE-type autofluorescence (AF) was measured to assess the time-dependent effects of FN3K on glycolaldehyde-induced AGE-modified porcine lens fragments and to evaluate its actions on intact lenses after in vivo intravitreal FN3K injection of murine eyes. A potential immune response after injection was evaluated by analysis of IL-2, TNFα, and IFNγ using an ELISA kit. Dose- and time-dependent AF kinetics were analyzed on pooled human lens fragments. Furthermore, AF measurements and a time-lapse of macroscopic changes were performed on intact cataractous human eye lenses after incubation with an FN3K solution. At last, AF measurements were performed on cataractous human eyes after crossover topical treatment with either saline- or FN3K-containing drops. While the lenses of the equine FN3K-treated eyes appeared to be clear, the saline-treated lenses had a yellowish-brown color. Following FN3K treatment, color restoration could be observed within 30 min. The extension rate of the equine FN3K-treated lens was more than twice the extension rate of the saline-treated lens. FN3K treatment induced significant time-dependent decreases in AGE-related AF values in the AGE-modified porcine lens fragments. Furthermore, in vivo intravitreal FN3K injection of murine eyes significantly reduced AF values of the lenses. Treatment did not provoke a systemic immune response in mice. AF kinetics of FN3K-treated cataractous human lens suspensions revealed dose- and time-dependent decreases. Incubation of cataractous human eye lenses with FN3K resulted in a macroscopic lighter color of the cortex and a decrease in AF values. At last, crossover topical treatment of intact human eyes revealed a decrease in AF values during FN3K treatment, while showing no notable changes with saline. Our study suggests, for the first time, a potential additional role of FN3K as an alternative treatment for AGE-related cataracts.

Fructosamine-3-Kinase as a Potential Treatment Option for Age-Related Macular Degeneration

Age-related macular degeneration is the leading cause of blindness in the developed world. Since advanced glycation end products (AGEs) are implicated in the pathogenesis of AMD through various lines of evidence, we investigated the potential of fructosamine-3-kinase (FN3K) in the disruption of retinal AGEs, drusenoid material and drusenoid lesions in patients with AMD. AGE-type autofluorescence was measured to evaluate the effects of FN3K on glycolaldehyde-induced AGE-modified neural porcine retinas and unmodified human neural retinas. Eye pairs from cigarette-smoke- and air-exposed mice were treated and evaluated histologically. Automated optical image analysis of human tissue sections was performed to compare control- and FN3K-treated drusen and near-infrared (NIR) microspectroscopy was performed to examine biochemical differences. Optical coherence tomography (OCT) was used to evaluate the effect of FN3K on drusenoid deposits after treatment of post-mortem human eyes. FN3K treatment provoked a significant decrease (41%) of AGE-related autofluorescence in the AGE-modified porcine retinas. Furthermore, treatment of human neural retinas resulted in significant decreases of autofluorescence (−24%). FN3K-treated murine eyes showed less drusenoid material. Pairwise comparison of drusen on tissue sections revealed significant changes in color intensity after FN3K treatment. NIR microspectroscopy uncovered clear spectral differences in drusenoid material (Bruch’s membrane) and drusen after FN3K treatment. Ex vivo treatment strongly reduced size of subretinal drusenoid lesions on OCT imaging (up to 83%). In conclusion, our study demonstrated for the first time a potential role of FN3K in the disruption of AGE-related retinal autofluorescence, drusenoid material and drusenoid lesions in patients with AMD.

Structural Basis for Potent Neutralization of Betacoronaviruses by Single-Domain Camelid Antibodies

Coronaviruses make use of a large envelope protein called spike (S) to engage host cell receptors and catalyze membrane fusion. Because of the vital role that these S proteins play, they represent a vulnerable target for the development of therapeutics. Here, we describe the isolation of single-domain antibodies (VHHs) from a llama immunized with prefusion-stabilized coronavirus spikes. These VHHs neutralize MERS-CoV or SARS-CoV-1 S pseudotyped viruses, respectively. Crystal structures of these VHHs bound to their respective viral targets reveal two distinct epitopes, but both VHHs interfere with receptor binding. We also show cross-reactivity between the SARS-CoV-1 S-directed VHH and SARS-CoV-2 S and demonstrate that this cross-reactive VHH neutralizes SARS-CoV-2 S pseudotyped viruses as a bivalent human IgG Fc-fusion. These data provide a molecular basis for the neutralization of pathogenic betacoronaviruses by VHHs and suggest that these molecules may serve as useful therapeutics during coronavirus outbreaks.

Selective Engagement of FcγRIV by a M2e-Specific Single Domain Antibody Construct Protects Against Influenza A Virus Infection

Lower respiratory tract infections, such as infections caused by influenza A viruses, are a constant threat for public health. Antivirals are indispensable to control disease caused by epidemic as well as pandemic influenza A. We developed a novel anti-influenza A virus approach based on an engineered single-domain antibody (VHH) construct that can selectively recruit innate immune cells to the sites of virus replication. This protective construct comprises two VHHs. One VHH binds with nanomolar affinity to the conserved influenza A matrix protein 2 (M2) ectodomain (M2e). Co-crystal structure analysis revealed that the complementarity determining regions 2 and 3 of this VHH embrace M2e. The second selected VHH specifically binds to the mouse Fcγ Receptor IV (FcγRIV) and was genetically fused to the M2e-specific VHH, which resulted in a bi-specific VHH-based construct that could be efficiently expressed in Pichia pastoris. In the presence of M2 expressing or influenza A virus-infected target cells, this single domain antibody construct selectively activated the mouse FcγRIV. Moreover, intranasal delivery of this bispecific FcγRIV-engaging VHH construct protected wild type but not FcγRIV^−/− mice against challenge with an H3N2 influenza virus. These results provide proof of concept that VHHs directed against a surface exposed viral antigen can be readily armed with effector functions that trigger protective antiviral activity beyond direct virus neutralization.

Potent single-domain antibodies that arrest respiratory syncytial virus fusion protein in its prefusion state

Human respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections in young children. The RSV fusion protein (F) is highly conserved and is the only viral membrane protein that is essential for infection. The prefusion conformation of RSV F is considered the most relevant target for antiviral strategies because it is the fusion-competent form of the protein and the primary target of neutralizing activity present in human serum. Here, we describe two llama-derived single-domain antibodies (VHHs) that have potent RSV-neutralizing activity and bind selectively to prefusion RSV F with picomolar affinity. Crystal structures of these VHHs in complex with prefusion F show that they recognize a conserved cavity formed by two F protomers. In addition, the VHHs prevent RSV replication and lung infiltration of inflammatory monocytes and T cells in RSV-challenged mice. These prefusion F-specific VHHs represent promising antiviral agents against RSV.

A collagen-binding EGFR antibody fragment targeting tumors with a collagen-rich extracellular matrix

Many tumors over-express collagen, which constitutes the physical scaffold of tumor microenvironment. Collagen has been considered to be a target for cancer therapy. The collagen-binding domain (CBD) is a short peptide, which could bind to collagen and achieve the sustained release of CBD-fused proteins in collagen scaffold. Here, a collagen-binding EGFR antibody fragment was designed and expressed for targeting the collagen-rich extracellular matrix in tumors. The antibody fragment (Fab) of cetuximab was fused with CBD (CBD-Fab) and expressed in Pichia pastoris. CBD-Fab maintained antigen binding and anti-tumor activity of cetuximab and obtained a collagen-binding ability in vitro. The results also showed CBD-Fab was mainly enriched in tumors and had longer retention time in tumors in A431 s.c. xenografts. Furthermore, CBD-Fab showed a similar therapeutic efficacy as cetuximab in A431 xenografts. Although CBD-Fab hasn’t showed better therapeutic effects than cetuximab, its smaller molecular and special target may be applicable as antibody–drug conjugates (ADC) or immunotoxins.

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.

Generation and in vivo characterization of a chimeric αvβ5-targeting antibody 14C5 and its derivatives

Background

Previous studies showed that radiolabeled murine monoclonal antibody (mAb) 14C5 and its Fab and F(ab')₂ fragments, targeting α_vβ₅ integrin, have promising properties for diagnostic and therapeutic applications in cancer. To diminish the risk of generating a human anti-mouse antibody response in patients, chimeric variants were created. The purpose of this study was to recombinantly produce chimeric antibody (chAb) derivatives of the murine mAb 14C5 and to evaluate the in vitro and in vivo characteristics.

Methods

In vitro stability, specificity, and affinity of radioiodinated chAb and fragments (Iodo-Gen method) were examined on high-expressing α_vβ₅ A549 lung tumor cells. In vivo biodistribution and pharmacokinetic characteristics were studied in A549 lung tumor-bearing Swiss Nu/Nu mice.

Results

Saturation binding experiments revealed high in vitro affinity of radioiodinated chAb, F(ab')₂, and Fab, with dissociation constants (K_D) of 1.19 ± 0.19, 0.68 ± 0.10, and 2.11 ± 0.58 nM, respectively. ChAb 14C5 showed highest tumor uptake (approximately 10%ID/g) at 24 h post injection, corresponding with other high-affinity Abs. ChF(ab')₂ and chFab fragments showed faster clearance from the blood compared to the intact Ab.

Conclusions

The chimerization of mAb 14C5 and its fragments has no or negligible effect on the properties of the antibody. In vitro and in vivo properties show that the chAb 14C5 is promising for radioimmunotherapy, due to its high maximum tumor uptake and its long retention in the tumor. The chF(ab')₂ fragment shows a similar receptor affinity and a faster blood clearance, causing less non-specific retention than the chAb. Due to their fast blood clearance, the fragments show high potential for radioimmunodiagnosis.

High yield of human monoclonal antibody produced by stably transfected Drosophila schneider 2 cells in perfusion culture using wave bioreactor

Since it was first introduced in late 1990s Wave bioreactor has been used for protein production by mammalian and insect cell lines. However, using Wave bioreactor to produce human monoclonal antibody by stable Drosophila Schneider 2 (S2) cell transfectants has not been reported before. In this study, S2 cells were co-transfected with an inducible vector expressing human monoclonal antibody heavy and light chains, respectively, specific for hemagglutinin (HA) of H5N1 influenza virus. Stable S2 transfectant clone was selected by limiting dilution assay. Stable S2 transfectant clone that produce the highest amount of human monoclonal antibody was inoculated into two 2-l disposable cellbags, where cell growth and antibody production were compared between batch and perfusion cultures using Wave bioreactor. Here, we report that maximum viable cell density reached 1.06 × 10(7) cells/ml in batch culture; whereas 1.04 × 10(8) cells/ml was achieved in perfusion culture. The maximum volumetric antibody productivity in batch culture was 52 mg/l/day; while perfusion culture yielded 1,437 mg/l/day. As a result, the total antibody production was 201 mg in batch culture and 8,212 mg in perfusion culture. The antibody produced by both cultures displays full neutralizing activity. Thus, our results provide strong support for using Wave bioreactor in perfusion culture for a large-scale production of human monoclonal antibody by stable S2 cell transfectants.

Engineering and expression of bibody and tribody constructs in mammalian cells and in the yeast Pichia pastoris

Bibodies and tribodies are therapeutic antibody derivatives with sizes of approximately 75 and 100 kDa, respectively. This makes them smaller than full-size monoclonal antibodies, leading to better tissue penetration. Compared to the smaller scFv and Fab fragments, the bi- and tribody formats have the additional advantage of a slower renal clearance. However, the cost-effective and efficient production of these and other antibody derivatives is crucial for their further success as therapeutics. Here, we describe the construction and initial transient production in mammalian cells of bibodies and tribodies, followed by their stable production in Pichia pastoris. The purification of the antibody derivatives from the yeast supernatant is also explained.

Production of antibody derivatives in the methylotrophic yeast Pichia pastoris

New antibody derivatives are continuously being generated to interact with a range of therapeutic targets. The cost-effective and efficient production of these and other antibody derivatives is crucial for their further success. Here, we describe the construction of the expression vectors needed for heterologous expression of a Fab fragment in the yeast Pichia pastoris. The experimental conditions for lab-scale expressions are discussed, and an overview of an efficient purification strategy is presented.

Production in yeast of pseudotype virus-like particles harboring functionally active antibody fragments neutralizing the cytolytic activity of vaginolysin

Background

Recombinant antibodies can be produced in different formats and different expression systems. Single chain variable fragments (scFvs) represent an attractive alternative to full-length antibodies and they can be easily produced in bacteria or yeast. However, the scFvs exhibit monovalent antigen-binding properties and short serum half-lives. The stability and avidity of the scFvs can be improved by their multimerization or fusion with IgG Fc domain. The aim of the current study was to investigate the possibilities to produce in yeast high-affinity scFv-Fc proteins neutralizing the cytolytic activity of vaginolysin (VLY), the main virulence factor of Gardnerella vaginalis.

Results

The scFv protein derived from hybridoma cell line producing high-affinity neutralizing antibodies against VLY was fused with human IgG1 Fc domain. Four different variants of anti-VLY scFv-Fc fusion proteins were constructed and produced in yeast Saccharomyces cerevisiae. The non-tagged scFv-Fc and hexahistidine-tagged scFv-Fc proteins were found predominantly as insoluble aggregates and therefore were not suitable for further purification and activity testing. The addition of yeast α-factor signal sequence did not support secretion of anti-VLY scFv-Fc but increased the amount of its intracellular soluble form. However, the purified protein showed a weak VLY-neutralizing capability. In contrast, the fusion of anti-VLY scFv-Fc molecules with hamster polyomavirus-derived VP2 protein and its co-expression with VP1 protein resulted in an effective production of pseudotype virus-like particles (VLPs) that exhibited strong VLY-binding activity. Recombinant scFv-Fc molecules displayed on the surface of VLPs neutralized VLY-mediated lysis of human erythrocytes and HeLa cells with high potency comparable to that of full-length antibody.

Conclusions

Recombinant scFv-Fc proteins were expressed in yeast with low efficiency. New approach to display the scFv-Fc molecules on the surface of pseudotype VLPs was successful and allowed generation of multivalent scFv-Fc proteins with high VLY-neutralizing potency. Our study demonstrated for the first time that large recombinant antibody molecule fused with hamster polyomavirus VP2 protein and co-expressed with VP1 protein in the form of pseudotype VLPs was properly folded and exhibited strong antigen-binding activity. The current study broadens the potential of recombinant VLPs as a highly efficient carrier for functionally active complex proteins.

Biochemical and biophysical characterization of humanized IgG1 produced in Pichia pastoris

The first full length IgG produced in Pichia pastoris was reported in late 1980. However, use of a wild-type Pichia expression system to produce IgGs with human-like N-linked glycans was not possible until recently. Advances in glycoengineering have enabled organisms such as Pichia to mimic human N-glycan biosynthesis and produce IgGs with human glycans on an industrial scale. Since there are only a few reports of the analytical characterization of Pichia-produced IgG, we summarize the results known in this field, and provide additional characterization data generated in our laboratories. The data suggest that Pichia-produced IgG has the same stability as that produced in Chinese hamster ovary (CHO) cells. It has similar aggregation profiles, charge variant distribution and oxidation levels as those for a CHO IgG. It contains human N-linked glycans and O-linked single mannose. Because of the comparable biophysical and biochemical characteristics, glycoengineered Pichia pastoris is an attractive expression system for therapeutic IgG productions.

MUC1 immunotherapy

The overexpression and aberrant glycosylation of MUC1 is associated with a wide variety of cancers, making it an ideal target for immunotherapeutic strategies. This review highlights the main avenues of research in this field, focusing on adenocarcinomas, from the preclinical to clinical; the problems and possible solutions associated with each approach; and speculates on the direction of MUC1 immunotherapeutic research over the next 5-10 years.

Generation of Fab fragment-like molecular recognition proteins against staphylococcal enterotoxin B by phage display technology

Antigen-binding fragments (Fab fragments) and single-chain variable fragments (scFv) against staphylococcal enterotoxin B (SEB) were produced by phage display technology. SEB epitopes were first identified by phage display approach using the commercial anti-SEB monoclonal antibody ab53981 as the target. Heptamer and dodecamer mimotope peptides recognized by ab53981 were screened from Ph.D-7 or Ph.D-12 random peptide phage libraries expressed in Escherichia coli. The isolated 7-mer and 12-mer mimotopes were shown to share a sequence homologous to ⁸PDELHK¹⁴S in the amino acid sequence of SEB. The N-terminal 15-mer peptide of SEB was determined to be an epitope of ab53981. After immunization of mice with maltose-binding protein-tagged N-terminal 15-mer peptide, a phage display Fab library was constructed using cDNA prepared from the mRNAs of spleen cells. Three phage clones displaying the Fab molecule which recognized SEB were isolated through three rounds of panning. Only one of them produced a soluble Fab fragment from the transformed cells, and the fragment fused with a histidine tag sequence was produced in E. coli cells and converted into scFv. Surface plasmon resonance analysis showed that the dissociation constants of these proteins with SEB were (4.1 ± 1.1) × 10⁻⁹ M and (8.4 ± 2.3) × 10⁻¹⁰ M, respectively. The produced molecule was applied to the determination of SEB by enzyme-linked immunosorbent assay and Western blot analysis.