Structure and development of single domain antibodies as modules for therapeutics and diagnostics

Abstract

Since their discovery just over 25 years ago, the single variable domain from heavy-chain-only antibodies plays a role in an increasing number of antibody-based applications. Structural and biophysical studies have revealed that the small, ∼15 kDa, single variable domain found in camelids displays versatility in target recognition. Such insight has served as the foundation to develop and engineer VHH domains with enhanced properties capable of targeting a range of therapeutically relevant protein antigens or low-molecular weight haptens. Furthermore, the modular nature of VHH domains allows them to be introduced into constructs that are simply not possible with conventional antibodies. Here, we review the structural and biophysical properties of VHH domains, highlight recent VHH-based therapeutics and diagnostics, and provide insight into VHH engineering that may pave the way to next-generation single domain antibody applications. Impact statement The development of novel antibody formats, beyond conventional antibodies, opens new possibilities in medical therapies, diagnostics, and general life science applications requiring affinity reagents. The camelid VHH domain, from heavy-chain-only antibodies, has emerged as a jack-of-all-trades module for novel affinity reagents. Applications include targeted cancer therapies, novel antimicrobial agents, conformation specific reagents, and tailor-made molecular switch entities. The breadth of unique uses for the VHH will continue to grow, opening new opportunities to treat and understand disease.

Nanobody—A versatile tool for cancer diagnosis and therapeutics

“…Furthermore, fusion of nanobody with other functional proteins could provide complementary activities to enhance the anti‐cancer effects and improve the target delivery of the effector moieties. Several excellent reviews have summarized the advances and progress of nanobody in antitumor investigations (Al‐Baradie, 2020; Hoey et al, 2019; Jindal et al, 2020; Yang et al, 2020). In this review, we focus on the conjugation of nanobody to various functional moieties that can further enhance their antitumor activities.…”

Single-Domain Antibodies for the Detection of SARS-CoV-2 Nucleocapsid Protein

“… 22 − 24 They possess many advantages over conventional antibodies including remarkable stability, ability to bind to hidden epitopes, and can be engineered to work optimally for specific applications. 25 In addition, these antibodies are small and easily produced in good quantity in Escherichia coli or yeast. SdAbs have been tapped as potential therapeutics and prophylactics for SARS-CoV-2, with reports of several high-affinity sdAbs specific for S showing promise in preventing viral infection.…”

Development and Characterization of Nanobodies Targeting the Kupffer Cell

“…The name nanobody (Nb) was coined to refer to the recombinantly-produced form of the VHH ( 16 ). As compared to other antibody fragments consisting of multiple domains, the Nb domains have a characteristic prolate ellipsoid shape that allows them to target cavities deep within their target antigens, therefore, Nb domains are frequently observed to target hidden or conformational target epitopes, which offers an added value for many applications ( 17 ). Owing to their unique properties, Nb domains have become increasingly popular for purposes of diagnostic or therapeutic applications in various disease areas, including infectious, inflammatory and oncologic diseases ( 18 , 19 ).…”