Inner ear autoantibodies and their targets in patients with autoimmune inner ear diseases

Immunological mechanisms an thought to play an important role in the pathog enesis of some cochleo-vestibular diseases. This study attempts to present further evidence of autoantibodies reactive against guinea pig inner ear pr oteins found in patients with autoimmune inner ear diseases (AIED) and spec ifically identifies the main target antigens of these antibodies. Sera from 110 patients with a clinical diagnosis of either rapidly progressive senso rineural hearing loss (n = 32), Meniere's disease (n = 41), sudden deafness (n = 26) or other aetiologies of hearing loss (n = 11) were screened by th e Western blot technique. Forty-four percent of the patients' sera had anti bodies to several inner ear proteins, of which the 30, 42 and 68 kDa protei ns were found to be the most reactive. These highly reactive proteins were identified by gas-phase micro sequencing after digestion with trypsin and s eparation of peptide fragments by high-performance liquid chromatography. A partial sequence of each protein was determined. These data, together with those obtained from 2-dimensional gel electrophoresis followed by Western blotting, demonstrated that the 30 and 42 kDa inner ear proteins are the ma jor peripheral myelin protein P0 and the beta -actin protein, respectively, while sequence analysis indicated that the 68 kDa protein is novel. These findings further support the hypothesis that several populations of antibod ies may contribute to the enhanced immunological activity of AIED patients. They also add a new dimension to our knowledge of AIED and may open new av enues in the development of simple serological assays, which are easier to perform and more rapid than Western blotting.