Approximately 70-90% of hypoadrenocorticism cases in human medicine result from immune-mediated adrenalitis. Although clinical signs are not present until ~90% of the adrenal cortex is destroyed, several different anti-adrenal autoantibodies can be identified in serum. In human medicine, presence of these antibodies constitutes the primary criteria for an early diagnosis of adrenalitis. Such a diagnostic tool is not currently available in veterinary medicine. However, from preliminary studies, we hypothesized that as in human hypoadrenocorticism, anti 21-hydroxylase antibody production occurs in canine hypoadrenocorticism. The antibody production precedes clinical disease, and is more prevalent in dog breeds susceptible to developing hypoadrenocorticism. The specific aims of the proposed research are to: 1) determine whether anti-adrenal autoantibodies are present in dogs with hypoadrenocorticism, 2) establish a diagnostic test to detect canine anti-adrenal autoantibodies, and 3) determine whether development of anti-adrenal autoantibodies has breed, sex, and age based predispositions. The canine 21-hydroxylase was expressed in E. coli, using standard techniques. The protein was purified and two rabbits and two dogs were immunized with the purified protein. The obtained positive control sera from these animals were used to establish an enzyme-linked immunosorbent assay (ELISA) for the detection of 21-hydroxylase autoantibodies in dogs. The preliminary data obtained with this ELISA showed that approximately 30% of dogs with naturally occurring primary Addison's disease produce antibodies against 21-hydroxylase. What remains unknown is whether autoantibody production precedes clinical disease, implying a role in the pathogenesis of the disease; if it is then the presence of 21-hydroxylase autoantibodies would be expected to be more prevalent in dog breeds susceptible to developing hypoadrenocorticism. Further development of the ELISA will enable epidemiologic studies to address specific aim three.
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