The Development of Single Domain Antibodies for Diagnostic and Therapeutic Applications

Abstract

Monoclonal antibodies have become increasingly accepted as diagnostics and therapeutics for various human diseases due to their high affinity and specificity. However, several practical drawbacks are apparent for the reagents based on conventional IgG antibodies. With the emergence of antibody engineering, many problems were overcome when the recombinant antibody fragments such as Fabs, scFvs, diabodies and single domain antibodies (sdAbs), are developed. These fragments not only retain the specificity of the whole monoclonal antibodies, but are also easy to express and produce in prokaryotic expression systems. Rather unexpectedly, the natural sdAbs namely V HH s, V NAR s and variable lymphocyte receptors (VLRs) that comprise excellent biological activities were recently discovered in camelids, cartilaginous fish and lampreys, respectively. Due to their unique characteristics, including small size, high thermostability, stable folding in the nucleus and cytosol and long CDR3 regions which have access to cavities or clefts on the surface of proteins, these new binders are now investigated extensively as a substitute for conventional antibodies. This review describes the potential of sdAbs selected using in vitro display systems and their use in multiple applications.(polyclonal Abs) are heterogeneous antibody mixtures that are derived from multiple plasma cell lines. Because polyclonal antibodies comprise a mixture of different antibodies carrying numerous paratopes, they have excellent properties for recognizing antigens [2]. A monoclonal antibody (mAb) is a homogeneous antibody generated from a single B lymphocyte clone. Antibodies produced in mAb format have an extremely high specificity against a single epitope on antigens [3]. Recombinant antibodies (rAbs) are antibodies generated using molecular biology techniques. They are aimed to improve the sensitivity, selectivity, stability and immobilization properties in diagnostic applications, for example, in biosensors [4]. In making decision to use or generate polyclonal, monoclonal or recombinant antibodies, several factors should be considered, including commercial availability, possibility to raise animals, types of applications, time length of a project and costs [1]. Although a vast number of rAbs has been proposed [5][6][7][8], the natural sdAb fragments that were recently discovered from camelids (V HH s), sharks (V NAR s) and lampreys (VLRs) have shown to possess extraordinary features that are not found in conventional antibodies, such as a small dimension, an elevated stability and the capability of recognizing cavities and clefts on the surface of proteins that cannot be reached by conventional recombinant antibodies [9][10][11]. This chapter will discuss the availability of new binders derived from vertebrates and give an overview of their applications in a biomedical platform by recognizing specified targets from various diseases. Monoclonal antibodies and their limitationsThe first description of monoclonal antibody (mAbs) production was published ...

Generation of a nanobody against HER2 tyrosine kinase using phage display library screening for HER2-positive breast cancer therapy development

“…The potential applications of camelid VHH single domains for diagnostic and therapeutic use have been reviewed (Leow et al, 2018;Tillib 2020). Many nanobody-based biological agents showed anticancer activity in preclinical studies (Bannas et al, 2017;Kijanka et al, 2015).…”

Easily Established and Multifunctional Synthetic Nanobody Libraries as Research Tools

“…Phages displaying nanobodies which bind to antigens can be enriched through several rounds of biopanning. These phages will be subsequently picked and screened using ELISA assay to confirm the binding and then sequenced before protein expression and purification [38].…”

Shark New Antigen Receptor (IgNAR): Structure, Characteristics and Potential Biomedical Applications

“…Consideration of the variable domain of sharks as therapeutic agents is caused by the peculiarity of this antibody’s structure from different discoveries: short α-helix structure of constant domain (C1) [ 15 ], salt bridge, and hydrophobic core are thought to contribute to the stability of constant domains [ 10 ]. Compared with murine mAbs and scFvs, shark VNAR sdAbs molecules are more sensitive and thermally stable to viral nucleoprotein (NP) of ZEBOV [ 58 ]. The variable domain of the shark antibody can be modified into a high number of formats and fused to various molecules and produced a satisfactory outcome.…”

“…The advantage of VNAR stability in extreme pHs, for example, incubation with acid produced by gastric glands [ 23 , 59 ]. The two distinct clones of VNAR reported to have a good binding ability and stability to P. gingivalis KgP [ 58 ]. All these findings are important to consider IgNAR as a satisfactory therapeutic agent.…”