Inclusion Criteria:

          1. Histological confirmation of grade III or IV high-grade glioma

          2. Tumor is mutated for IDH1 or IDH2 gene (detected by R132HIDH immunochemistry or
             IDH1/IDH2 sequencing)

          3. Age between 18 and 85 years old

          4. Recurrence after radiotherapy and at least one line of alkylating chemotherapy
             (Temozolomide or PCV (Procarbazine, CCNU, Vincristine) (Surgery at recurrence is
             allowed before trial inclusion)

          5. Recurrence occurring more than 12 weeks from the end of the radiotherapy or occurring
             outside the irradiated volume

          6. Karnofsky performance status > 50

          7. Radiologically measurable disease based on RANO criteria. Tumor lesions situated in a
             previously irradiated area are considered measurable if progression has been
             demonstrated in such lesions

          8. Patients must be able to taper steroids (preferably discontinued). Dose at inclusion
             must be ≤ 10 mg prednisone (or equivalent*). The decrease in dose will be evaluated by
             clinical examination, the ability to decrease the corticosteroids being related to the
             absence of increased headaches and the absence of increased of neurological disability
             (impaired alertness)

          9. Available archived tissue for molecular (MGMT methylation, mutational load estimation)
             and immunohistochemical analysis (PD1, PD-L1, CD3, CD4, FoxP3, CD8, CD68, CD163, GFAP,
             olig2, ATRX, CIC, Ki67, P53)

         10. The following laboratory values obtained ≤ 7 days prior to inclusion:

               -  WBC ≥ 2000/μL

               -  Neutrophils ≥ 1500/μL

               -  Platelets ≥ 100 x103/μL

               -  Hemoglobin > 9.0 g/dL

               -  Serum creatinine ≤ 1.5 x ULN or creatinine clearance (CrCl) ≥ 40 mL/min (if using
                  the Cockcroft-Gault formula below):

             Female CrCl = [(140 - age in years) x weight in kg x 1.04] / serum creatinine in
             µmol/l Male CrCl = ([140 - age in years) x weight in kg x 1.23] / serum creatinine in
             µmol/l

               -  AST/ALT ≤ 3 x ULN

               -  Total Bilirubin ≤ 1.5 x ULN (except subjects with Gilbert Syndrome, who can have
                  total bilirubin < 3.0 mg/dL)

               -  Negative serum pregnancy test for women of childbearing potential

         11. Women of childbearing potential (WOCBP) must agree to follow instructions for
             method(s) of contraception for the duration of study treatment with nivolumab and 5
             months after the last dose of study treatment (ie, 30 days (duration of ovulatory
             cycle) plus the time required for the investigational drug to undergo approximately
             five half-lives)

         12. Males who are sexually active with WOCBP must agree to follow instructions for
             method(s) of contraception for the duration of study treatment with nivolumab and 7
             months after the last dose of study treatment {i.e., 90 days (duration of sperm
             turnover) plus the time required for the investigational drug to undergo approximately
             five half-lives.}

         13. Written informed consent dated and signed, prior to any study specific procedures
             (sampling, treatment and analyses).

         14. Affiliation to a French social security system (recipient or assign) excluding AME.

        Exclusion Criteria:

          1. Pregnant or breastfeeding women

          2. Any serious or uncontrolled medical disorder that, in the opinion of the investigator,
             may increase the risk associated with study participation or study drug
             administration, impair the ability of the subject to receive protocol therapy, or
             interfere with the interpretation of study results

          3. Prior treatment with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, anti-CTLA-4
             antibody or any other antibody or drug specifically targeting T-cell co-stimulation or
             immune checkpoint pathways

          4. Subjects with an active, known or suspected autoimmune disease. Subjects with type I
             diabetes mellitus, hypothyroidism only requiring hormone replacement, skin disorders
             (such as vitiligo, psoriasis or alopecia) not requiring systemic treatment, or
             conditions not expected to recur in the absence of an external trigger are permitted
             to enrol

          5. Subjects with interstitial lung disease that is symptomatic or may interfere with the
             detection or management of suspected drug-related pulmonary toxicity or congestive
             cardiac insufficiency

          6. Any positive test for hepatitis B virus or hepatitis C virus indicating acute or
             chronic infection, and/or detectable virus and a known history of positive test for
             human immunodeficiency virus (HIV) or known acquired immunodeficiency syndrome (AIDS).

          7. Subjects with a condition requiring systemic treatment with either corticosteroids (>
             10 mg daily prednisone or > 1,5 mg dexamethasone or equivalent*) or other
             immunosuppressive medications within 14 days of first study treatment administration.
             Inhaled or topical steroids, and adrenal replacement steroid doses > 10 mg daily
             prednisone or > 1,5 mg dexamethasone or equivalent, are permitted in the absence of
             active autoimmune disease.

          8. Any chemotherapy, anticancer immunotherapy or anticancer agents within 4 weeks (6
             weeks for nitrosourea) before the first dose of study treatment,

          9. Receiving any other investigational agent or study drugs from a previous clinical
             study within 4 weeks before the first dose of study treatment (6 weeks for
             nitrosoureas).

         10. Prior malignancy active within the previous 3 years except for locally curable cancers
             that have been apparently cured, such as basal or squamous cell skin cancer,
             superficial bladder cancer, or carcinoma in situ of the prostate, cervix, or breast.

         11. History of allergy or Hypersensitivity to Nivolumab or to any of the excipients

         12. Any unresolved toxicities (excepted alopecia), from prior therapy greater than CTCAE
             grade 1 at the time of inclusion.

         13. Subjects with history of life-threatening toxicity, including hypersensitivity
             reaction, related to prior immunoglobulin treatment for another condition (except
             those considered unlikely to re-occur) or any other study drug component.

         14. Surgical procedure < 7 days prior to first study treatment administration, vascular
             access device no restriction;

         15. Subjects unable (e.g., due to pacemaker or ICD device) or unwilling to have a
             contrast-enhanced MRI of the head;

         16. Known allergy or contraindication to Gadolinium;

         17. Patients under guardianship