Production of single chain Fab (scFab) fragments in Bacillus megaterium

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Efficient production of soluble recombinant single chain Fv fragments by a Pseudomonas putida strain KT2440 cell factory

<p>Abstract</p> <p>Background</p> <p>Recombinant antibody fragments have a wide range of applications in research, diagnostics and therapy. For many of these, small fragments like single chain fragment variables (scFv) function well and can be produced inexpensively in bacterial expression systems. Although <it>Escherichia coli </it>K-12 production systems are convenient, yields of different fragments, even those produced from codon-optimized expression systems, vary significantly. Where yields are inadequate, alternative production systems are needed. <it>Pseudomonas putida </it>strain KT2440 is a versatile biosafety strain known for good expression of heterologous genes, so we have explored its utility as a cell factory for production of scFvs.</p> <p>Results</p> <p>We have generated new broad host range scFv expression constructs and assessed their production in the <it>Pseudomonas putida </it>KT2440 host. Two scFvs bind either to human C-reactive protein or to mucin1, proteins of significant medical diagnostic and therapeutic interest, whereas a third is a model anti-lysozyme scFv. The KT2440 antibody expression systems produce scFvs targeted to the periplasmic space that were processed precisely and were easily recovered and purified by single-step or tandem affinity chromatography. The influence of promoter system, codon optimization for <it>P. putida</it>, and medium on scFv yield was examined. Yields of up to 3.5 mg/l of pure, soluble, active scFv fragments were obtained from shake flask cultures of constructs based on the original codon usage and expressed from the <it>Ptac </it>expression system, yields that were 2.5-4 times higher than those from equivalent cultures of an <it>E. coli </it>K-12 expression host.</p> <p>Conclusions</p> <p><it>Pseudomonas putida </it>KT2440 is a good cell factory for the production of scFvs, and the broad host range constructs we have produced allow yield assessment in a number of different expression hosts when yields in one initially selected are insufficient. High cell density cultivation and further optimization and refinement of the KT2440 cell factory will achieve additional increases in the yields of scFvs.</p

Production of recombinant antibody fragments in Bacillus megaterium

BACKGROUND: Recombinant antibodies are essential reagents for research, diagnostics and therapy. The well established production host Escherichia coli relies on the secretion into the periplasmic space for antibody synthesis. Due to the outer membrane of Gram-negative bacteria, only a fraction of this material reaches the medium. Recently, the Gram-positive bacterium Bacillus megaterium was shown to efficiently secrete recombinant proteins into the growth medium. Here we evaluated B. megaterium for the recombinant production of antibody fragments. RESULTS: The lysozyme specific single chain Fv (scFv) fragment D1.3 was succesfully produced using B. megaterium. The impact of culture medium composition, gene expression time and culture temperatures on the production of functional scFv protein was systematically analyzed. A production and secretion at 41°C for 24 h using TB medium was optimal for this individual scFv. Interestingly, these parameters were very different to the optimal conditions for the expression of other proteins in B. megaterium. Per L culture supernatant, more than 400 μg of recombinant His(6)-tagged antibody fragment were purified by one step affinity chromatography. The material produced by B. megaterium showed an increased specific activity compared to material produced in E. coli. CONCLUSION: High yields of functional scFv antibody fragments can be produced and secreted into the culture medium by B. megaterium, making this production system a reasonable alternative to E. coli

Developing Recombinant Antibodies by Phage Display Against Infectious Diseases and Toxins for Diagnostics and Therapy

Antibodies are essential molecules for diagnosis and treatment of diseases caused by pathogens and their toxins. Antibodies were integrated in our medical repertoire against infectious diseases more than hundred years ago by using animal sera to treat tetanus and diphtheria. In these days, most developed therapeutic antibodies target cancer or autoimmune diseases. The COVID-19 pandemic was a reminder about the importance of antibodies for therapy against infectious diseases. While monoclonal antibodies could be generated by hybridoma technology since the 70ies of the former century, nowadays antibody phage display, among other display technologies, is robustly established to discover new human monoclonal antibodies. Phage display is an in vitro technology which confers the potential for generating antibodies from universal libraries against any conceivable molecule of sufficient size and omits the limitations of the immune systems. If convalescent patients or immunized/infected animals are available, it is possible to construct immune phage display libraries to select in vivo affinity-matured antibodies. A further advantage is the availability of the DNA sequence encoding the phage displayed antibody fragment, which is packaged in the phage particles. Therefore, the selected antibody fragments can be rapidly further engineered in any needed antibody format according to the requirements of the final application. In this review, we present an overview of phage display derived recombinant antibodies against bacterial, viral and eukaryotic pathogens, as well as microbial toxins, intended for diagnostic and therapeutic applications

A multi-Fc-species system for recombinant antibody production

<p>Abstract</p> <p>Background</p> <p>Genomic, transcriptomic and proteomic projects often suffer from a lack of functional validation creating a strong demand for specific and versatile antibodies. Antibody phage display represents an attractive approach to select rapidly <it>in vitro </it>the equivalent of monoclonal antibodies, like single chain Fv antibodies, in an inexpensive and animal free way. However, so far, recombinant antibodies have not managed to impose themselves as efficient alternatives to natural antibodies.</p> <p>Results</p> <p>We developed a series of vectors that allow one to easily fuse single chain Fv antibodies to Fc domains of immunoglobulins, improving their sensitivity and facilitating their use. This series enables the fusion of single chain Fv antibodies with human, mouse or rabbit Fc so that a given antibody is no longer restricted to a particular species. This opens up unlimited multiplexing possibilities and gives additional value to recombinant antibodies. We also show that this multi-Fc species production system can be applied to natural monoclonal antibodies cloned as single chain Fv antibodies and we converted the widely used 9E10 mouse anti-Myc-tag antibody into a human and a rabbit antibody.</p> <p>Conclusion</p> <p>Altogether, this new expression system, that brings constant quality, sensitivity and unique versatility, will be important to broaden the use of recombinant and natural monoclonal antibodies both for laboratory and diagnosis use.</p

Development of human antibody fragments using antibody phage display for the detection and diagnosis of Venezuelan equine encephalitis virus (VEEV)

<p>Abstract</p> <p>Background</p> <p>Venezuelan equine encephalitis virus (VEEV) belongs to the Alphavirus group. Several species of this family are also pathogenic to humans and are recognized as potential agents of biological warfare and terrorism. The objective of this work was the generation of recombinant antibodies for the detection of VEEV after a potential bioterrorism assault or an natural outbreak of VEEV.</p> <p>Results</p> <p>In this work, human anti-VEEV single chain Fragments variable (scFv) were isolated for the first time from a human naïve antibody gene library using optimized selection processes. In total eleven different scFvs were identified and their immunological specificity was assessed. The specific detection of the VEEV strains TC83, H12/93 and 230 by the selected antibody fragments was proved. Active as well as formalin inactivated virus particles were recognized by the selected antibody fragments which could be also used for Western blot analysis of VEEV proteins and immunohistochemistry of VEEV infected cells. The anti-VEEV scFv phage clones did not show any cross-reactivity with Alphavirus species of the Western equine encephalitis virus (WEEV) and Eastern equine encephalitis virus (EEEV) antigenic complex, nor did they react with Chikungunya virus (CHIKV), if they were used as detection reagent.</p> <p>Conclusion</p> <p>For the first time, this study describes the selection of antibodies against a human pathogenic virus from a human naïve scFv antibody gene library using complete, active virus particles as antigen. The broad and sensitive applicability of scFv-presenting phage for the immunological detection and diagnosis of Alphavirus species was demonstrated. The selected antibody fragments will improve the fast identification of VEEV in case of a biological warfare or terroristic attack or a natural outbreak.</p

Single chain Fab (scFab) fragment

BACKGROUND: The connection of the variable part of the heavy chain (VH) and and the variable part of the light chain (VL) by a peptide linker to form a consecutive polypeptide chain (single chain antibody, scFv) was a breakthrough for the functional production of antibody fragments in Escherichia coli. Being double the size of fragment variable (Fv) fragments and requiring assembly of two independent polypeptide chains, functional Fab fragments are usually produced with significantly lower yields in E. coli. An antibody design combining stability and assay compatibility of the fragment antigen binding (Fab) with high level bacterial expression of single chain Fv fragments would be desirable. The desired antibody fragment should be both suitable for expression as soluble antibody in E. coli and antibody phage display. RESULTS: Here, we demonstrate that the introduction of a polypeptide linker between the fragment difficult (Fd) and the light chain (LC), resulting in the formation of a single chain Fab fragment (scFab), can lead to improved production of functional molecules. We tested the impact of various linker designs and modifications of the constant regions on both phage display efficiency and the yield of soluble antibody fragments. A scFab variant without cysteins (scFabΔC) connecting the constant part 1 of the heavy chain (CH1) and the constant part of the light chain (CL) were best suited for phage display and production of soluble antibody fragments. Beside the expression system E. coli, the new antibody format was also expressed in Pichia pastoris. Monovalent and divalent fragments (DiFabodies) as well as multimers were characterised. CONCLUSION: A new antibody design offers the generation of bivalent Fab derivates for antibody phage display and production of soluble antibody fragments. This antibody format is of particular value for high throughput proteome binder generation projects, due to the avidity effect and the possible use of common standard sera for detection

Generation of Recombinant Antibodies against the beta-(1,6)-Branched beta-(1,3)-D-Glucan Schizophyllan from Immunized Mice via Phage Display

beta-(1,6)-Branched beta-(1,3)-D-glucans like schizophyllan from the basidiomycete Schizophyllum commune excite various immunostimulatory effects and have been clinically tested as adjuvants. Some of the glucans are also applicable in food or petrol industry due to their viscosity and temperature stability in aqueous solution. Antibodies against these glucans could be used as tool for analysis of glucan preparations or for further research of its bioactivity. Therefore, an immune phage display library was constructed from mice immunized with schizophyllan. Three recombinant monoclonal antibodies were isolated from this library by affinity selection (panning) on schizophyllan. The half-maximal effective concentration (EC50) values for those antibodies varied between 16.4 ng mL−1 and 21.3 ng mL−1. The clones showed binding specificity not only for schizophyllan but also for other beta-(1,6)-branched beta-(1,3)-D-glucans of similar macromolecular structure. Denaturation of the secondary structure led to a reduced antibody binding, indicating an epitope requiring the correct conformation of the triple helical structure of the glucans

Development of an inhibiting antibody against equine interleukin 5 to treat insect bite hypersensitivity of horses

Insect bite hypersensitivity (IBH) is the most common allergic skin disease of horses. It is caused by insect bites of the Culicoides spp. which mediate a type I/IVb allergy with strong involvement of eosinophil cells. No specific treatment option is available so far. One concept could be the use of a therapeutic antibody targeting equine interleukin 5, the main activator and regulator of eosinophils. Therefore, antibodies were selected by phage display using the naïve human antibody gene libraries HAL9/10, tested in a cellular in vitro inhibition assay and subjected to an in vitro affinity maturation. In total, 28 antibodies were selected by phage display out of which eleven have been found to be inhibiting in the final format as chimeric immunoglobulin G with equine constant domains. The two most promising candidates were further improved by in vitro affinity maturation up to factor 2.5 regarding their binding activity and up to factor 2.0 regarding their inhibition effect. The final antibody named NOL226-2-D10 showed a strong inhibition of the interleukin 5 binding to its receptor (IC50 = 4 nM). Furthermore, a nanomolar binding activity (EC50 = 8.8 nM), stable behavior and satisfactory producibility were demonstrated. This antibody is an excellent candidate for in vivo studies for the treatment of equine IBH

Human antibodies neutralizing diphtheria toxin in vitro and in vivo

Diphtheria is an infectious disease caused by Corynebacterium diphtheriae. The bacterium primarily infects the throat and upper airways and the produced diphtheria toxin (DT), which binds to the elongation factor 2 and blocks protein synthesis, can spread through the bloodstream and affect organs, such as the heart and kidneys. For more than 125 years, the therapy against diphtheria has been based on polyclonal horse sera directed against DT (diphtheria antitoxin; DAT). Animal sera have many disadvantages including serum sickness, batch-to-batch variation in quality and the use of animals for production. In this work, 400 human recombinant antibodies were generated against DT from two different phage display panning strategies using a human immune library. A panning in microtiter plates resulted in 22 unique in vitro neutralizing antibodies and a panning in solution combined with a functional neutralization screening resulted in 268 in vitro neutralizing antibodies. 61 unique antibodies were further characterized as scFv-Fc with 35 produced as fully human IgG1. The best in vitro neutralizing antibody showed an estimated relative potency of 454 IU/mg and minimal effective dose 50% (MED50%) of 3.0 pM at a constant amount of DT (4x minimal cytopathic dose) in the IgG format. The targeted domains of the 35 antibodies were analyzed by immunoblot and by epitope mapping using phage display. All three DT domains (enzymatic domain, translocation domain and receptor binding domain) are targets for neutralizing antibodies. When toxin neutralization assays were performed at higher toxin dose levels, the neutralizing capacity of individual antibodies was markedly reduced but this was largely compensated for by using two or more antibodies in combination, resulting in a potency of 79.4 IU/mg in the in vivo intradermal challenge assay. These recombinant antibody combinations are candidates for further clinical and regulatory development to replace equine DAT