Production of bifunctional proteins by Aspergillus awamori: Llama variable heavy chain antibody fragment (VHH) R9 coupled to Arthromyces ramosus peroxidase (ARP)

Large-Scale Production of Anti-RNase A VHH Expressed in pyrG Auxotrophic Aspergillus oryzae

Nanobodies, also referred to as VHH antibodies, are the smallest fragments of naturally produced camelid antibodies and are ideal affinity reagents due to their remarkable properties. They are considered an alternative to monoclonal antibodies (mAbs) with potential utility in imaging, diagnostic, and other biotechnological applications given the difficulties associated with mAb expression. Aspergillus oryzae (A. oryzae) is a potential system for the large-scale expression and production of functional VHH antibodies that can be used to meet the demand for affinity reagents. In this study, anti-RNase A VHH was expressed under the control of the glucoamylase promoter in pyrG auxotrophic A. oryzae grown in a fermenter. The feature of pyrG auxotrophy, selected for the construction of a stable and efficient platform, was established using homologous recombination. Pull-down assay, size exclusion chromatography, and surface plasmon resonance were used to confirm the binding specificity of anti-RNase A VHH to RNase A. The affinity of anti-RNase A VHH was nearly 18.3-fold higher (1.9 nM) when expressed in pyrG auxotrophic A. oryzae rather than in Escherichia coli. This demonstrates that pyrG auxotrophic A. oryzae is a practical, industrially scalable, and promising biotechnological platform for the large-scale production of functional VHH antibodies with high binding activity.

Characterization and comparison of two peptide-tag specific nanobodies for immunoaffinity chromatography

Affinity chromatography is generally regarded as a powerful tool allowing the single step purification of recombinant proteins with high purity and yields. However, for most protein products, affinity purification methods for industrial applications are not readily available, mainly due to the lack of specific and robust natural counterparts that could function as affinity ligands. In this study, we explored the applicability of nanobody-based peptide-tag immunorecognition systems as a platform for affinity chromatography. Two typical nanobodies (BC2-nb and Syn2-nb) that are capable of recognizing specifically a particular peptide-tag, were prepared through prokaryotic expression and proved to be able to bind with nanomolar affinity to their cognate tag fused to enhanced green fluorescent protein (eGFP). Through an epoxy-based immobilization reaction, the two nanobodies were coupled on a Sepharose CL-6B matrix under the same conditions. The remaining antigen binding activity of the immobilized BC2-nb and Syn2-nb was determined to be 83.1% and 42.9%, yielding the resins with the dynamic binding capacity (DBC) of 21.4 mg/mL and 5.9 mg/mL, respectively. The immobilized affinity ligands exhibited high binding specificity towards their respective target peptides, yielding a product purity above 90% directly from crude bacterial lysates in one single chromatographic step. However, for the both affinity complexes, desorption has been found difficult, and effective recovery of the bound products could be only achieved with competitive elution or after employing harsh conditions such as 10 mM NaOH solution, which will compromise the reuse cycles of the affinity resins. This study shows the potential of nanobody-based affinity chromatography for efficient purification of recombinant proteins especially from complex feedstocks and reveals the primary issues to be addressed to develop a successful application.

Nanobody-based enzyme immunoassay for aflatoxin in agro-products with high tolerance to cosolvent methanol

A phage-displayed library of variable domain of heavy chain of the heavy chain antibody (VHH) or nanobody (Nb) was constructed after immunizing an alpaca with aflatoxin B1 (AFB1) conjugated with bovine serum albumin (AFB1-BSA). Two AFB1-specific nanobodies were selected. The obtained nanobodies were compared to an aflatoxin-specific monoclonal antibody B5 with respect to stability under organic solvents and high temperature. The two nanobodies could bind antigen specifically after exposure to temperatures as high as 95 °C. Besides, the nanobodies showed better or similar tolerance to organic solvents. A competitive ELISA with nanobody Nb26 was developed for the analysis of AFB1, exhibiting an IC50 value of 0.754 ng/mL (2.4 μM), linear range from 0.117 to 5.676 ng/mL. Due to the high tolerance to methanol, sample extracts were analyzed by nanobody-based ELISA without dilution. The recovery from spiked peanut, rice, corn and feedstuff ranged from 80 to 115%. In conclusion, the isolated nanobodies are excellent candidates for immunoassay application in aflatoxin determination.

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.

Nanobodies as novel agents for disease diagnosis and therapy

The discovery of naturally occurring, heavy-chain only antibodies in Camelidae, and their further development into small recombinant nanobodies, presents attractive alternatives in drug delivery and imaging. Easily expressed in microorganisms and amenable to engineering, nanobody derivatives are soluble, stable, versatile, and have unique refolding capacities, reduced aggregation tendencies, and high-target binding capabilities. This review outlines the current state of the art in nanobodies, focusing on their structural features and properties, production, technology, and the potential for modulating immune functions and for targeting tumors, toxins, and microbes.

Nanobody-albumin nanoparticles (NANAPs) for the delivery of a multikinase inhibitor 17864 to EGFR overexpressing tumor cells

A novel, EGFR-targeted nanomedicine has been developed in the current study. Glutaraldehyde crosslinked albumin nanoparticles with a size of approximately 100nm were loaded with the multikinase inhibitor 17864-L(x)-a platinum-bound sunitinib analogue-which couples the drug to methionine residues of albumin and is released in a reductive environment. Albumin nanoparticles were surface-coated with bifunctional polyethylene glycol 3500 (PEG) and a nanobody-the single variable domain of an antibody-(Ega1) against the epidermal growth factor receptor (EGFR). EGa1-PEG functionalized nanoparticles showed a 40-fold higher binding to EGFR-positive 14C squamous head and neck cancer cells in comparison to PEGylated nanoparticles. 17864-L(x) loaded EGa1-PEG nanoparticles were internalized by clathrin-mediated endocytosis and ultimately digested in lysosomes. The intracellular routing of EGa1 targeted nanoparticles leads to a successful release of the kinase inhibitor in the cell and inhibition of proliferation whereas the non-targeted formulations had no antiproliferative effects on 14C cells. The drug loaded targeted nanoparticles were as effective as the free drug in vitro. These results demonstrate that multikinase inhibitor loaded nanoparticles are interesting nanomedicines for the treatment of EGFR-positive cancers.

Rotavirus A-specific single-domain antibodies produced in baculovirus-infected insect larvae are protective in vivo

Background

Single-domain antibodies (sdAbs), also known as nanobodies or VHHs, are characterized by high stability and solubility, thus maintaining the affinity and therapeutic value provided by conventional antibodies. Given these properties, VHHs offer a novel alternative to classical antibody approaches. To date, VHHs have been produced mainly in E. coli, yeast, plants and mammalian cells. To apply the single-domain antibodies as a preventive or therapeutic strategy to control rotavirus infections in developing countries (444,000 deaths in children under 5 years of age) has to be minimized their production costs.

Results

Here we describe the highly efficient expression of functional VHHs by the Improved Baculovirus Expression System (IBES® technology), which uses a baculovirus expression vector in combination with Trichoplusia ni larvae as living biofactories. Two VHHs, named 3B2 and 2KD1, specific for the inner capsid protein VP6 of Group A rotavirus, were expressed in insect larvae. The IBES® technology achieved very high expression of 3B2 and 2KD1, reaching 2.62% and 3.63% of the total soluble protein obtained from larvae, respectively. These expression levels represent up to 257 mg/L of protein extract after insect processing (1 L extract represents about 125 g of insect biomass or about 375 insect larvae). Larva-derived antibodies were fully functional when tested in vitro and in vivo, neutralizing Group A rotaviruses and protecting offspring mice against rotavirus-induced diarrhea.

Conclusions

Our results open up the possibility of using insects as living biofactories (IBES® technology) for the cost-efficient production of these and other fully functional VHHs to be used for diagnostic or therapeutic purposes, thereby eliminating concerns regarding the use of bacterial or mammalian cells. To the best of our knowledge, this is the first time that insects have been used as living biofactories to produce a VHH molecule.

Efficient heterologous expression and secretion in Aspergillus oryzae of a llama variable heavy-chain antibody fragment V(HH) against EGFR

We have constructed a filamentous fungus Aspergillus oryzae that secretes a llama variable heavy-chain antibody fragment (V(HH)) that binds specifically to epidermal growth factor receptor (EGFR) in a culture medium. A major improvement in yield was achieved by fusing the V(HH) with a Taka-amylase A signal sequence (sTAA) and a segment of 28 amino acids from the N-terminal region of Rhizopus oryzae lipase (N28). The yields of secreted, immunologically active anti-EGFR V(HH) reached 73.8 mg/1 in a Sakaguchi flask. The V(HH) fragments were released from the sTAA or N28 proteins by an indigenous A. oryzae protease during cultivation. The purified recombinant V(HH) fragment was specifically recognized and could bind to the EGFR with a high affinity.

Targeting epidermal growth factor receptor in tumors: from conventional monoclonal antibodies via heavy chain-only antibodies to nanobodies

The discovery of naturally occurring heavy chain only antibodies and their further development into small recombinant 'nanobodies' offers attractive applications in drug targeting. Here, we describe the properties of nanobodies that have been developed to target the epidermal growth factor receptor (EGFR) and contrast these to the characteristics of heavy chain only antibodies and conventional antibodies. EGFR is overexpressed in many tumors and is an attractive target for tumor-directed drug targeting.

Nanobody; an old concept and new vehicle for immunotargeting

The use of antibodies in cancer therapy has come a long way since the day Paul Ehrlich described the concept and Kohler and Milstein devised the hybridoma technology to bring this theory to reality. The synthesis of murine monoclonal antibodies (mAbs) was the first success in this field, leading to the invention of chimerization, the production of variable fragments (Fv) with the progression to domain antibodies (dAb) and later humanization technologies to maximize the clinical utility of murine mAbs. It was just by chance that dAbs were found to exist in ?heavy chain? immunoglobulins from Camelidae family and cartilaginous fish. These unique antibody fragments interact with antigen by virtue of only one single variable domain, referred to as VHH or nanobody. Several characteristics make nanobody use superior to the abovementioned antibodies. They are non-immunogenic and show high thermal and chemical stability. There are several reports of raising specific nanobodies against enzymes, haptens, pathogens, toxins and tumor markers, which are outlined in this paper. All these characteristics make them strong candidates as targeting agents for cancer therapy.

Properties, production, and applications of camelid single-domain antibody fragments

Camelids produce functional antibodies devoid of light chains of which the single N-terminal domain is fully capable of antigen binding. These single-domain antibody fragments (VHHs or Nanobodies®) have several advantages for biotechnological applications. They are well expressed in microorganisms and have a high stability and solubility. Furthermore, they are well suited for construction of larger molecules and selection systems such as phage, yeast, or ribosome display. This minireview offers an overview of (1) their properties as compared to conventional antibodies, (2) their production in microorganisms, with a focus on yeasts, and (3) their therapeutic applications.