Be it checkpoint inhibitor drugs or adoptive cell transfer, immunotherapy works primarily with T cells, which are a type of white blood cell, or lymphocyte.
Largely, our immune systems rely on B lymphocytes and T lymphocytes.
The former are active in a variety of infections, whereas the latter must be activated when combating cancer or more serious infections such as tuberculosis.
But T cells are more difficult to trigger than B lymphocytes. To activate T cells, healthcare providers must inject a peptide that often deteriorates before reaching its destination.
But now, an international team of researchers from different universities across Europe has devised a type of resilient microcapsule that can help to deliver vaccines straight to the core of T cells.
The scientists created these microcapsules using an unconventional material: synthetic spider silk.
The research was led by Prof. Carole Bourquin, who is a specialist in cancer immunotherapy at the faculties of medicine and science of the University of Geneva in Switzerland.
She says, "To develop immunotherapeutic drugs effective against cancer, it is essential to generate a significant response of T lymphocytes. As the current vaccines have only limited action on T cells, it is crucial to develop other vaccination procedures to overcome this issue."
The findings were published in the journal Biomaterials.
Using bioinspiration to create better vaccines
Prof. Bourquin and her team used synthetic biopolymers based on the silk spun by spiders. Spider silk is an incredibly strong and resilient material. In fact, it is thought to be "five times stronger than steel of the same diameter."
Study co-author Thomas Scheibel, who's an expert on spider silk from the University of Bayreuth in Germany, explains the procedure used by the scientists. "We recreated this special silk in the lab to insert a peptide with vaccine properties," he says.
"The resulting protein chains are then salted out to form injectable microparticles," Scheibel adds. The peptide encapsulated by these microparticles was thus delivered directly to the heart of the lymph node cells, boosting the immune response of T cells.
"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."
Prof. Carole Bourquin
The researchers explain further advantages of using particles of synthetic spider silk biopolymers. They are resistant to high temperatures of up to 100°C, for example, making the vaccines easy to store.
Also, the microparticles could theoretically enable researchers to develop and deliver vaccines without using any other adjuvants.
"More and more, scientists are trying to imitate nature in what it does best," explains Scheibel. "This approach even has a name: bioinspiration, which is exactly what we have done here."
One limitation might be the size of the microparticles, admit the scientists. Further research needs to establish whether larger antigens can be incorporated in the microcapsules.