Engineering of single chain antibodies for solubility

Application of germline antibody features to vaccine development, antibody discovery, antibody optimization and disease diagnosis

Although the efficacy and commercial success of vaccines and therapeutic antibodies have been tremendous, designing and discovering new drug candidates remains a labor-, time- and cost-intensive endeavor with high risks. The main challenges of vaccine development are inducing a strong immune response in broad populations and providing effective prevention against a group of highly variable pathogens. Meanwhile, antibody discovery faces several great obstacles, especially the blindness in antibody screening and the unpredictability of the developability and druggability of antibody drugs. These challenges are largely due to poorly understanding of germline antibodies and the antibody responses to pathogen invasions. Thanks to the recent developments in high-throughput sequencing and structural biology, we have gained insight into the germline immunoglobulin (Ig) genes and germline antibodies and then the germline antibody features associated with antigens and disease manifestation. In this review, we firstly outline the broad associations between germline antibodies and antigens. Moreover, we comprehensively review the recent applications of antigen-specific germline antibody features, physicochemical properties-associated germline antibody features, and disease manifestation-associated germline antibody features on vaccine development, antibody discovery, antibody optimization, and disease diagnosis. Lastly, we discuss the bottlenecks and perspectives of current and potential applications of germline antibody features in the biotechnology field.

An Intercompany Perspective on Practical Experiences of Predicting, Optimizing and Analyzing High Concentration Biologic Therapeutic Formulations

Developing high-dose biologic drugs for subcutaneous injection often requires high-concentration formulations and optimizing viscosity, solubility, and stability while overcoming analytical, manufacturing, and administration challenges. To understand industry approaches for developing high-concentration formulations, the Formulation Workstream of the BioPhorum Development Group, an industry-wide consortium, conducted an inter-company collaborative exercise which included several surveys. This collaboration provided an industry perspective, experience, and insight into the practicalities for developing high-concentration biologics. To understand solubility and viscosity, companies desire predictive tools, but experience indicates that these are not reliable and experimental strategies are best. Similarly, most companies prefer accelerated and stress stability studies to in-silico or biophysical-based prediction methods to assess aggregation. In addition, optimization of primary container-closure and devices are pursued to mitigate challenges associated with high viscosity of the formulation. Formulation strategies including excipient selection and application of studies at low concentration to high-concentration formulations are reported. Finally, analytical approaches to high concentration formulations are presented. The survey suggests that although prediction of viscosity, solubility, and long-term stability is desirable, the outcome can be inconsistent and molecule dependent. Significant experimental studies are required to confirm robust product definition as modeling at low protein concentrations will not necessarily extrapolate to high concentration formulations.

Structure-based engineering of an antiangiogenic scFv antibody for soluble production in E. coli without loss of activity

Development of monoclonal antibody therapeutics against vascular endothelial growth factor receptor 2 (VEGFR-2) protein, which is the main regulator in angiogenesis, has been a major challenge for years. In the current study, we engineer an inclusion body forming single-chain variable fragment (scFv) against VEGFR-2 by using complementarity determining regions (CDR) grafting technique to improve its solubility and investigate the activity of the engineered molecule. CDR sequences of the target scFv were grafted into the framework of another intrinsically soluble scFv molecule. Based on the computational results, CDR grafting has increased the solubility of the grafted scFv molecule. Results confirmed that the grafting approach increased in vivo folding properties of the target scFv molecule compared with the original scFv molecule. Similar binding affinities to the VEGFR-2 were observed for the original and the grafted scFv by surface plasmon resonance assays. Biological activity assays, including human umbilical vein endothelial cells proliferation and wound healing assays, showed that grafted scFv molecule has an antiangiogenic property. This study suggests that an antiangiogenic scFv fully expressed as an inclusion body can be rescued by grafting its CDR regions to a scFv expressed in a soluble form without any loss in its binding property and its activity.

Deciphering Protein Corona by scFv-Based Affinity Chromatography

It remains challenging to precisely decipher the structural and functional characteristics of protein coronas. To overcome the drawbacks frequently occurring in the traditional separation methods, an anti-PEG single-chain variable fragment (PEG-scFv) based affinity chromatography (AfC) was developed to achieve precise and efficient separation of protein coronas on PEGylated liposomes (sLip). His-tagged PEG-scFv could readily capture sLip without affecting protein corona compositions, and separate sLip/protein complex from plasma protein aggregates and endogenous vesicles through the Ni-NTA column. AfC demonstrated 43-fold higher protein corona collecting efficiency than centrifugation, which was extremely crucial for separation of in vivo protein coronas due to the limitation of sample size. AfC evaded contamination by endogenous vesicles and protein aggregates occurring in centrifugation, and reserved the loosely bound proteins, providing an unprecedented approach to deeply decipher protein coronas. The scFv-based AfC also paves new avenues for the separation of protein coronas formed on other nanomedicines.

Test bacterial inclusion body for activity prior to start denaturing and refolding processes to obtain active eukaryotic proteins

One of a major drawbacks correlated with expressing antibody fragments in bacterial cells is insolubility, which is often regarded as an obstacle in obtaining active molecules. Recombinant proteins aggregated as inclusion bodies within bacterial cells are thought to be unfolded or misfolded, and therefore inactive. So, denaturing and refolding strategies, which are laborious and sometime inefficient, are used to obtain correctly-folded active proteins. In the current study, we show that large quantities of correctly folded and completely active scFv molecules are there in bacterial inclusion bodies; they only need to be isolated from inclusion bodies.