Utilities: |
Autoimmune inner ear disease
(AIED) is a heterogeneous group of diseases
with regard to clinical presentation and
immunoreactivity to inner ear components.
They include rapidly progressive sensorineural
hearing loss (SNHL), Ménière's
disease (MD), and sudden deafness (SD).
The search for a diagnostic test led to
the finding that most AIED patients had
antibodies that react with 130-kd, 68-
kd, 58-kd, 42-kd and 30-kd (P0) proteins
from human and bovine ears. The presence
of antibodies to a 68-kd antigen, identified
by Western blot, has been the best candidate
to date as a diagnostic test for AIED and
may be useful in predicting steroid responsiveness
in the patient population. Moreover, reactivity
with the 68-kd protein was present in serum
samples from 89% of 47 patients with active
disease compared to none of 25 patients
with inactive disease. Of the 36 patients
with a positive test result on Western
blot assay for antibodies to the 68-kd
protein, 27 (75%) responded to steroid
therapy. Only four (18%) of the 22 patients
with a negative test result responded to
steroid therapy. A recent study showed
a positive reaction to P0 (from guinea
pig inner ear extraction) in all bilateral
MD and bilateral sudden hearing loss patients
and indicates these pathologies are the
result of an ongoing autoimmune process
directed against specific inner ear antigens.
The 68-kd inner ear antigen identified
by Ramakrishnam is not HSP-70. The 68-kd
protein binds supporting cells in the organ
of Corti, while HSP-70 antibody does not
bind to any site in the inner ear. Also,
the commercial recombinant HSP-70 could
not bind to sera from patients with AIED.
This data indicates that the presence
of circulating antibodies to human or bovine
inner ear extract serves as a useful marker
for the diagnosis of AIED and that its
presence correlates with disease activity
and responsiveness to corticosteroid treatment.
RDL has developed a new EIA anti-Bovine
Inner Ear Membrane antibody assay including
130-kd, 68-kd, 42-kd and 30-kd (P0) antibodies. |