Is it possible to express antibodies in bacteria?

08 Oct, 2024

Monoclonal antibodies are currently produced in mammalian cell culture, making them complex to express and expensive to manufacture. If it were possible to express antibodies in bacteria, it would be quick and easy to introduce the desired genes, as well as making the proteins cheaper to obtain. Bacteria have difficulty producing large proteins, due to the small size of their cytoplasm - fragments of antibody can instead be used.¹

Researchers have been able to express antibodies in E. coli, introducing DNA coding for a specific fusion protein. The methods described in [1] suggest it is possible to obtain a target antibody in just three days. ²

Although bacteria-synthesised monoclonal antibodies are not glycosylated, it is understood that this does not affect their action in vivo or in vitro.³

Using bacteria, specifically E. coli, allows for simpler protein purification methods to be used, as the expression levels of all proteins in E. coli can be controlled across the entire genome. In [1], they used a protein purification matrix.

There are a number of antibody fragment drugs already available for clinical use, with many being expressed in E. coli.¹ Directed evolution and rational design could be used to improve antibody fragments for prokaryotic expression and to improve their thermal/acid/alkali resistance. Technologies like AlphaFold⁴ or LigandMPNN⁵ could be used to aid the design of these proteins.
Special tagging domains can be added to antibodies, improving the purification efficiency and allowing cheaper purification methods to be used.¹ Due to the de novo design of many of these molecules, adding tagging domains is a good method to improve the manufacturing efficiency.
Host cells can also be engineered to increase their protein expression levels.¹ Increasing yields may reduce costs by allowing smaller bioreactors to be used, while fed-batch methods can be used to convert the bacteria from growth to protein synthesis phases.

Antibody fragment drugs are cheaper and easier to produce, as it is possible to express them easily in E. coli chassis. They have a similar function to monoclonal antibodies, but cannot have such complex antigen-binding sites. Due to antibody fragments smaller size, they are able to reach more locations within the organism, and are less likely to cause infusion reactions in the patient.⁶

It’s also possible to express nanobodies in bacteria. Nanobodies are the smallest functional unit of an antibody, and are produced in vivo in response to viral infection and vaccination. These proteins are highly versatile and have a modular nature, allowing them to be fused with Fc domains of antibodies to be used in a similar way to conventional antibodies. However, their smaller size reduces the range of epitopes they can complement.⁷
Yeasts have also been used to express nanobodies.⁸