H3.3K27M Peptide Vaccine With Nivolumab for Children With Newly Diagnosed DIPG and Other Gliomas

Participants who are eligible will receive a specific peptide vaccine, along with a helper drug called poly-ICLC, in combination with nivolumab, every 3 weeks for the first 6 months of treatment. Participants will be monitored routinely by laboratory assessments, physical evaluation, vital signs, and MRI. Participants who tolerate therapy well and have stable or improved disease after 6 months of treatment can continue to receive treatment, nivolumab continuing every 3 weeks but vaccine and poly-ICLC now every 6 weeks, for a total of 96 weeks of treatment.