Modified amyloid β peptide

Providing peptide based on the sequence of amyloid β that can safely and effectively enhanced immune response as a prophylactic or therapeutic drug for Alzheimer's disease is an object. Cysteine ​​or added or inserted amyloid β peptide or a portion thereof analogs thereof, and immune response enhancing method against amyloid β with the peptide. Prophylactic or therapeutic drug for Alzheimer's disease using the immune response enhancing amyloid β peptide. Similar effects are expected, DNA vaccine containing the gene encoding the cysteine-added or inserted amyloid β peptide or derived peptides that.