Expression System of Bispecific Antibody

Bispecific antibodies (bsAbs) are synthetic antibodies that contain two distinct antigen-binding sites. These antibodies do not occur naturally; instead, they are designed and produced using antibody engineering techniques. Over the past few decades, significant advancements in the production technology of bispecific antibodies have laid the groundwork for their widespread application.

To produce bsAbs, it is crucial to select an appropriate expression system. Common expression systems include mammalian cells, bacteria, yeast, and others. The following sections will introduce several prevalent types of expression systems:

Mammalian Expression System

The majority of approved therapeutic antibodies are produced in mammalian cells. This preference is due to their ability to express, fold, post-translationally modify, and secrete proteins in ways that closely resemble endogenous human proteins, thereby reducing the risk of unnecessary immunogenicity ^[1]. To produce bsAbs, it is crucial to select an appropriate expression system. Common expression systems include mammalian cells, bacteria, yeast, and others. The following sections will introduce several prevalent types of expression systems:

1.2 Human Embryonic Kidney 293 (HEK293) Cells

HEK293 cells are a widely used mammalian expression system for producing bsAbs. Their high transfection efficiency, ability to perform complex post-translational modifications, and scalable production capabilities make them ideal for bsAbs expression. Commonly utilized in the discovery and early development stages, HEK cells provide a human-like environment for protein folding and processing, ensuring the proper structure and function of therapeutic antibodies ^[4].

Other Expression Systems

2.1 Escherichia coli (E. coli)

E. coli is a commonly used bacterial expression system for producing bsAbs, particularly for smaller antibody fragments like single-chain variable fragments (scFvs). Its advantages include fast growth, low cost, and high protein yield, making it an attractive option for early-stage research and development. However, since E. coli lacks the machinery for post-translational modifications such as glycosylation, it is less suitable for full-length antibodies or complex bsAbs requiring mammalian-like processing ^[1]. Despite these limitations, E. coli remains a valuable tool for bsAbs production in specific applications.

2.2 Yeast

The yeast expression system offers an efficient and cost-effective option. Yeast cells grow rapidly and can prodoptionuce large quantities of antibodies within a short timeframe. They combine some of the advantages of prokaryotic systems with the ability to perform post-translational modifications on expressed proteins [5]. However, due to differences in the intracellular environments between yeast and mammalian cells, the correct folding and assembly of certain complex antibodies may present challenges.

Different expression systems each have their own advantages and disadvantages in the production of bispecific antibodies. Future research should aim to optimize these expression systems to better meet the growing demand for bispecific antibodies.

References

[1] Frenzel A, Hust M, Schirrmann T. Expression of recombinant antibodies. Front Immunol. 2013;4:217. doi: 10.3389/fimmu.2013.00217.

[2] Kunert R, Reinhart D. Advances in recombinant antibody manufacturing. Appl Microbiol Biotechnol. 2016;100(8):3451–3461. doi: 10.1007/s00253-016-7388-9.

[3] Kunert R, Reinhart D. Advances in recombinant antibody manufacturing. Appl Microbiol Biotechnol. 2016 Apr;100(8):3451-61. doi: 10.1007/s00253-016-7388-9.

[4] Goh JB, Ng SK. Impact of host cell line choice on glycan profile. Crit Rev Biotechnol. 2018;38(6):851–867. doi: 10.1080/07388551.2017.1416577.

[5] Dalvie, N. C., & Dunn, M. J. (2016). Yeast systems for the production of recombinant proteins. In Recombinant Protein Expression in Microbial Systems (pp. 23-44). Springer, New York, NY.