BACKGROUND

Invariant natural killer T (iNKT) cells and CD8 T cells are key in the immune response against multiple myeloma (MM), a largely incurable blood cancer. Immunization is a promising strategy to activate these T cell populations. To our knowledge, immunization with messenger RNA (mRNA) and the iNKT agonist, α-galactosylceramide (αGC), has not been studied in MM, as knowledge on clinically relevant antigens in preclinical MM models is lacking.

METHODS

Microarray data and immunopeptidomics (imPep) were used to identify candidate antigens for immunization in 5TMM models. Galsomes, lipid nanoparticles containing antigen mRNA and αGC were used to immunize 5T33MM-bearing mice. This treatment was combined with a CD40 agonist. Tumor burden and activation of iNKT cells and CD8 T cells were studied using M-protein electrophoresis, flow cytometry and ELISA.

RESULTS

RNA transcripts revealed survivin as a candidate antigen. Prime-boost Galsomes therapy targeting survivin significantly reduced M-protein levels despite low survivin-specific T cell responses. Further analysis showed potential T cell fratricide. ImPep revealed HSP60, Idiotype, PICALM and EF1A1 as candidate antigens. Prime-boost therapy with Galsomes targeting these antigens reduced MM growth significantly when combined with a CD40 agonist, coinciding with significantly improved antigen presentation, costimulation and cytotoxicity of iNKT cells and CD8 T cells.

CONCLUSION

These findings highlight the potential of Galsomes, an mRNA vaccine designed to activate CD8 T cells and iNKT cells, for MM therapy, and emphasize the importance of combinatorial approaches, addressing immune anergy for effective MM immunotherapies.