The synthetic silk biopolymer is lightweight, biocompatible, non-toxic and highly resistant to degradation from light and heat

Scientists have developed microcapsules made of spider silk that can deliver vaccines directly to the heart of immune cells.

To fight cancer, researchers increasingly use vaccines that stimulate the immune system to identify and destroy tumour cells. However, the desired immune response is is not always guaranteed. In order to strengthen the efficacy of vaccines on the immune system and in particular on T lymphocytes, specialised in the detection of cancer cells researchers developed this new spider silk microcapsules

This process, described in the journal Biomaterials, could also be applied to preventive vaccines to protect against infectious diseases, and constitutes an important step towards vaccines that are stable, easy to use, and resistant to the most extreme storage conditions.

Stimulate immune response

The human immune system is largely based on two types of cells: B lymphocytes, which produce the antibodies needed to defend against various infections, and T lymphocytes. In the case of cancer and certain infectious diseases such as tuberculosis, T lymphocytes need to be stimulated.

However, their activation mechanism is more complex than that of B lymphocytes: to trigger a response, it is necessary to use a peptide, a small piece of protein which, if injected alone, is rapidly degraded by the body even before reaching its target.

“To develop immunotherapeutic drugs effective against cancer, it is essential to generate a significant response of T lymphocytes,” said Carole Bourquin, from the University of Geneva (UNIGE), who directed this work. “As the current vaccines have only limited action on T-cells, it is crucial to develop other vaccination procedures to overcome this issue.”

Scientists used synthetic spider silk biopolymers – a lightweight, biocompatible, non-toxic material that is highly resistant to degradation from light and heat.

“We recreated this special silk in the lab to insert a peptide with vaccine properties,” said Thomas Scheibel, from the University of Bayreuth in Germany and one of the authors of the study. “The resulting protein chains are then salted out to form injectable microparticles,” said Scheibel.

New vaccination strategy

Silk microparticles form a transport capsule that protects the vaccine peptide from rapid degradation in the body, and delivers the peptide to the center of the lymph node cells, thereby considerably increasing T lymphocyte immune responses.

“Our study has proved the validity of our technique. We have demonstrated the effectiveness of a new vaccination strategy that is extremely stable, easy to manufacture and easily customizable,” said Bourquin.

The synthetic silk biopolymer particles demonstrate a high resistance to heat, withstanding over 100 degree Celsius for several hours without damage. In theory, this process would make it possible to develop vaccines that do not require adjuvants and cold chains. An undeniable advantage, especially in developing countries where one of the great difficulties is the preservation of vaccines.

One of the limitations of this process, however, is the size of the microparticles: while the concept is in principle applicable to any peptide, which are all small enough to be incorporated into silk proteins, further research is needed to see if it is also possible to incorporate the larger antigens used in standard vaccines, especially against viral diseases.