The role of vaccines in glioblastoma—Updated clinical results

Glioblastoma (GB) is regarded as an incurable disease due to its poor prognosis and limited treatment options. One of the main obstacles is attributed to the unique immunosuppressive microenvironment in which GB occurs. The central nervous system (CNS), in particularly the brain has been traditionally viewed as an immune-privileged organ in which inflammation is prevented by a lack of professional antigen-presenting cells (APCs), lack of lymphatic drainage, and presence of tight endothelial barriers (i.e., blood-brain barrier (BBB)) that prevent the entry of immune cells and macromolecules. This results in a poor activation of the adaptive immune response, and lack of infiltration of the tumor by autoreactive lymphocytes, a phenotype also known as “cold” tumors. Several strategies have been proposed to activate the immune system and remodel the GB microenvironment, turning “cold tumors” into “hot tumors.” This chapter will focus in vaccination strategies that try to engage the adaptive immune system and trigger T-cell infiltration.