Revolutionary Advances in Single-Domain Antibody Development and Applications-Special Topic on Phage Display Technology-Tekbiotech-Yeast and Phage Display CRO, Expert in Nano-body and Antibody Drug Development

Revolutionary Advances in Single-Domain Antibody Development and Applications

Origin of the Revolution

Recombinant antibodies known as heavy-chain antibodies (HCAbs) consist solely of two heavy chains and lack light chains. The antigen recognition portion of an HCAb is a single variable domain, referred to as sdAb, VHH, or nanobody (Nb) [1]. Approximately 30 years ago, research groups serendipitously discovered HCAbs in camelids. These antibodies can constitute up to 81% of total serum IgG in some camelid species. Although sdAbs also exist naturally in species such as cartilaginous fish, mice, and even humans, only camelids and cartilaginous fish possess functional sdAbs capable of effectively binding antigens. In mice and humans, these types of antibodies can sometimes lead to disease or immune system disorders.

Figure 1: IgG and sdAb

Revolutionary Breakthroughs

To date, many monoclonal antibodies (mAbs) have been approved for treating various tumors. However, certain inherent structural limitations restrict the efficacy of mAbs and conventional antibody derivatives for tumor therapy, particularly in solid tumors with dense tissue. Furthermore, the long half-life of mAbs, ranging from several days to 4 weeks, can pose safety concerns, further limiting their application in areas such as imaging or radioimmunotherapy.

Compared to mAbs, sdAbs possess numerous advantages that make them ideal for medical applications. First, sdAbs exhibit better solubility and high thermal stability. Moreover, the small size of sdAbs enables them to cross the blood-brain barrier more efficiently, providing a foundation for disease treatment. Finally, the CDR3 region of sdAbs can form a unique structure that allows binding to cavities and crevices on target antigens, enabling them to recognize unique epitopes inaccessible to conventional antibodies [2]. Although sdAbs of animal origin possess unique properties, they may present potential safety issues hindering their clinical application. Therefore, humanization has become the mainstream approach to address the immunogenicity of sdAbs. Using different humanization strategies, camelid and shark-derived VHH and VNAR sequences can be replaced with human sequences.

Practical Applications

As more academic institutions, research organizations, and biotechnology companies employ these technologies, the identification and production of nanobodies have become well-established. Typically, nanobody libraries are constructed, and screening technologies are used to efficiently isolate monoclonal nanobodies, which are subsequently purified.

Purified sdAbs have a wide and diverse range of applications. Their most significant impact is in the medical disease field. As a class of novel therapeutic antibodies considerably smaller and more stable than conventional antibodies, nanobodies can extravasate from blood vessels and diffuse into tissues to bind tumor-specific antigens. Even in plant science, the application of sdAbs can enhance plant defense against pathogens.

sdAbs are also used for detecting and neutralizing infectious diseases and biological toxins. Nanobodies can function by binding to key proteins used by pathogens to enter host cells. They can also neutralize bacterial toxins, such as anthrax toxin from Bacillus anthracis.

Due to their favorable biodistribution in the body and high affinity for disease biomarkers, nanobodies are increasingly used in diagnostics. They can be customized against tumor-specific markers to help detect and locate tumor sites. Their ability to cross the blood-brain barrier is particularly beneficial for treating neurological diseases.

TekBiotech, based on phage display and yeast display technologies, has established a comprehensive targeted antibody drug discovery platform. We provide high-quality monoclonal antibody development services for scientists worldwide, covering various formats including scFv, VHH, and Fab. Furthermore, we can develop antibodies with diverse functional and structural characteristics, including but not limited to neutralizing antibodies, conformation-specific antibodies, and cross-reactive antibodies. Additionally, TekBiotech offers supporting downstream services such as antibody expression validation, antibody humanization design and validation, antibody affinity maturation, and CAR-T candidate sequence design, meeting the diverse needs of clients for antibody drug development.

References

[1] Yu T, Zheng F, He W, et al. Single domain antibody: Development and application in biotechnology and biopharma. Immunol Rev. 2024;328(1):98-112.

[2] Wang M, Ying T, Wu Y. Single-domain antibodies as therapeutics for solid tumor treatment. Acta Pharm Sin B. 2024;14(7):2854-2868.

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