Peptide-Pulsed Dendritic Cell Vaccination in Combination With Nivolumab and Ipilimumab for the Treatment of Recurrent and/or Progressive Diffuse Hemispheric Glioma, H3 G34-mutant

Inclusion Criteria: * Participants between the ages of 13 and 60 years with pathologically-confirmed diagnosis of (or pathology re-review consistent with) DHG will be enrolled in this study * All participants must be undergoing clinically indicated resection surgical resection with the goal of cytoreduction * Participants must undergo human leukocyte antigen (HLA) testing * A female participant who has childbearing potential must have negative urine or serum pregnancy test 72 hours prior to the first dose and be willing to use adequate method of contraception for course of study and 120 days after last dose * The participant (or legally acceptable representative if applicable) provides informed consent (and written assent from minors) for the trial * Have unequivocal evidence for contrast-enhancing tumor progression by modified response assessment in neuro-oncology (mRANO) criteria based on MRI scan within 72 days prior to enrollment. This criterion will be reviewed by investigators prior to enrollment * An interval of the following durations prior to enrollment: * At least 14 days from prior surgical resection * At least 7 days from prior stereotactic biopsy * At least 12 weeks from prior radiotherapy, unless there is unequivocal histologic confirmation of tumor progression * At least 23 days from prior chemotherapy * At least 42 days from nitrosureas * Have sufficient archival tumor tissue confirming high-grade glioma (HGG) or variants for submission following r…