Combining immune checkpoint blockade with an oncolytic virus. (A) VSV infecting leukemic blasts, replicating within them, and causing cell lysis. PD-L1, expressed on leukemic blasts, interacts with PD-1 on cytotoxic T lymphocytes and suppresses their effector function. (B) Addition of anti–PD-L1 antibody disrupts the immune checkpoint interaction and releases the T-cell inhibition. Effector T lymphocytes are now able to infiltrate and potentiate an immune response against the virally infected blasts, increasing cell kill. Professional illustration by Somersault18:24.