Prolonged TSH receptor A subunit immunization of female mice leads to a long-term model of Graves' disease, tachycardia, and cardiac hypertrophy.

Abstract

A transient model for human Graves' disease was successfully established in mice using up to 3 immunizations with recombinant adenovirus expressing the extracellular A-subunit of the human TSH receptor (TSHR) (Ad-TSHR). We studied extension of adenovirally induced TSHR A-subunit immunization in mice by using a novel protocol of long-term 3- and 4-weekly injections. Generation of TSHR binding stimulatory antibodies (capacity to stimulate cAMP activity in TSHR-expressing test cells), goiter, and histological thyroid alterations were maintained for at least 9 months in all Ad-TSHR-immunized mice. In response to injection of 10(10) plaque-forming units of Ad-TSHR, also elevated mean serum T4 levels were observed throughout the study. Moreover, cardiac organ involvement (tachycardia and hypertrophy) were consistently observed in these mice. Higher doses of Ad-TSHR (10(11) plaque-forming units) did not produce consistent elevation of T4 and were not associated with a clear increase in heart rate vs controls, probably because these high doses provoked an immune response-induced tachycardia on their own. In summary, a long-term model of Graves' disease induced by a relatively simple protocol of continuing monthly immunizations should allow to investigate long-term disease mechanisms and may possibly obviate the need for more complicated disease models. Moreover, the clinical outcome predictor of tachycardia and cardiac involvement was reliably detected in the model.