In a major study, researchers have developed a new type of precise therapeutic vaccine against leukaemia — a cancer of blood-forming tissues, including bone marrow.

Although the possibility of treating leukaemia through vaccination has been established, therapeutic performance still falls short of expectations in the clinic.

According to the study, published in the journal Nature Biomedical Engineering, the vaccine utilises self-healing polylactic acid microcapsules for co-encapsulating a new epitope peptide and PD-1 antibody.

“Our clinical findings revealed the high expression of EPS8 and PD-1/PD-L1 in leukaemia patients, which could be respectively used as a new type of leukaemia antigen and a checkpoint target for a leukaemia vaccine,” said study author LI Yuhua from Zhujiang Hospital in China.

In the novel vaccine, epitope peptides and PD-1 antibodies can be simply, mildly and efficiently loaded into polylactic acid microcapsules, facilitated by the unique self-healing feature of the microcapsule.

After a single vaccination, the deposition and degradation of microcapsules at the local injection site lead to the recruitment of activated antigen-presenting cells and sustained release of both cargos.

“With the synergism of these two aspects, we observed a significant improvement in specific Cytotoxic T Lymphocyte (CTL) activation,” said researchers.

They also verified the availability of the novel vaccine using various epitope peptides in different models, such as murine leukaemia, humanised cell line-derived leukaemia xenograft (CDX) and patient-derived leukaemia xenograft (PDX) models.

The microcapsule-based formulation demonstrated its superior performance over that of the ISA adjuvant (commercialized adjuvant) in all leukaemia therapeutic models, showing the promise of the microcapsule-based vaccine for use against various leukaemia antigens in the clinic.

“With the advantages of FDA-approved polylactic acid material, convenience in preparing the vaccine formulation, diversity of vaccine components, and excellent therapeutic effect, the microcapsule-based vaccine exhibits great potential for clinical translation,” the authors wrote.