Synthetic human target autoantigen genes comprising sequences coding for at least two immunogenic epitopic clusters (hereinafter IEC) of autoantigen(s) related to a specific autoimmune disease, wherein said at least two IECs may be derived from a sole autoantigen or from at least two different autoantigens related to said autoimmune disease, and polypeptides encoded thereby, can be used for the treatment and the diagnosis of autoimmune diseases such as multiple sclerosis (MS), insulin-dependent diabetes mellitus (IDDM), rheumatoid arthritis (RA), myasthenia gravis (MG) and uveitis.