The invention provides therapeutic antibodies and methods for treatment of diseases associated with diseases associated with aggregation of α-synuclein, e.g., in the brain of a subject. Such methods provide administration of therapeutic antibodies to elicit a beneficial immunogenic response against aggregation of α-synuclein. The methods are particularly useful for prophylactic and therapeutic treatment of diseases associated with the formation of Lewy bodies, e.g., Parkinson's disease.