Gene engineered exosome reverses T cell exhaustion in cancer immunotherapy

Cancer patients by immune checkpoint therapy have achieved long-term remission,with no recurrence of clinical symptoms of cancer for many years.Nevertheless,more than half of cancer patients are not responsive to this therapy due to immune exhaustion.Here,we report a novel gene engineered exosome which is rationally designed by engineering PD1 gene and simultaneously enveloping an immune adjuvant imiquimod(PD1-Imi Exo)for boosting response of cancer immune checkpoint blockage therapy.The results showed that PD1-Imi Exo had a vesicular round shape(approximately 139 nm),revealed a significant targeting and a strong binding effect with both cancer cell and dendritic cell,and demonstrated a remarkable therapeutic efficacy in the melanoma-bearing mice and in the breast cancer-bearing mice.The mechanism was associated with two facts that PD1-Imi Exo blocked the binding of CD8^(+)T cell with cancer cell,displaying a PD1/PDL1 immune checkpoint blockage effect,and that imiquimod released from PD1-Imi Exo promoted the maturation of immature dendritic cell,exhibiting a reversing effect on the immune exhaustion through activating and restoring function of CD8^(+)T cell.In conclusion,the gene engineered exosome could be used for reversing T cell exhaustion in cancer immunotherapy.This study also offers a promising new strategy for enhancing PD1/PDL1 therapeutic efficacy,preventing tumor recurrence or metastasis after surgery by rebuilding the patients’immunity,thus consolidating the overall prognosis.