Wilms tumor 1 peptide vaccination after hematopoietic stem cell transplant in leukemia patients

Although the prognosis of leukemia patients after allogeneic hematopoietic stem cell transplantation (HSCT) has greatly improved, relapse is still a major cause of death after HSCT. Cancer vaccines may have the potential to enhance the graft-versus-leukemia (GVL) effect. The post–allogeneic HSCT period provides a unique platform for vaccination, because (I) tumor burden is minimal, (II) lymphopenia allows for rapid expansion of cytotoxic T cells (CTLs), (III) donor-derived CTLs are not exhausted, (IV) inflammation is caused by alloreactions, and (V) the abundance of regulatory T cells is low due to their late recovery. Tumor cell lysates, dendritic cells (DCs), and peptides derived from leukemia-associated antigens (LAAs) have been used as vaccines. Clinical trials with several types of vaccines for post-HSCT patients revealed that the vaccination induced an immunological response and might benefit patients with minimal residual disease; however, the efficacy of this approach must be examined in randomized studies. In addition, it is important to consider the combination of cancer vaccine with checkpoint antibodies, recently shown to be useful in treating leukemia relapse after HSCT.