Methods and compositions are provided for treatment of neurodegenerative diseases in which there is accumulation of misfolded and/or aggregated proteins, excluding prion diseases. In particular, the invention relates to treatment of the neurodegenerative diseases Huntington's disease (HD), Alzheimer's disease (AD) or Parkinson's disease (PD), by administration of an agent selected from the group consisting of (i) Copolymer 1, (ii) a Copolymer 1-related peptide, (iii) a Copolymer 1-related polypeptide, and (iv) T cells activated with (i), (ii) or (iii).
