Summary                         

Background: The objective was to study targeted therapies using a biologically active monoclonal antibody against intracellular adhesion molecule-1 (ICAM-1 mAb) and an siRNA targeting thyroid-stimulating hormone (TSH) receptor (TSHR) in a BALB/c mouse model of Graves’ disease (GD).

Material and methods: An improved method for establishing a stable model of GD in BALB/c mice was developed by immunization with pcDNA 3.1/TSHR 289 and electroporation (EP). The mice in which GD was successfully established were divided into a nontreated control group, which was treated with continuous immunization, and treated groups, which were treated with the siRNA and ICAM-1 mAb. Normal mice were included as a blank group. These groups were used to compare the effects of treatment with the ICAM-1 mAb and siRNA.

Results: The two novel treatments markedly improved weight loss, serum thyroxine (T4) levels, thyroid-stimulating hormone antibody (TSAb) levels, thyroid-stimulating blocking antibody (TSBAb) levels and thyroid uptake of ^99mTcO₄ in GD model mice. Compared with the siRNA treatment, treatment with the ICAM-1 mAb produced more obvious benefits. The differences in the posttreatment indexes between the two treatment groups were statistically significant (p < 0.05).

Conclusions: These preliminary data suggest that both the biologically active ICAM-1 mAb and the siRNA targeting TSHR were effective. The ICAM-1 mAb exerted a better therapeutic effect than the siRNA targeting TSHR. Both treatments showed potential efficacy as novel treatments for GD and may therefore represent therapeutic options in addition to the existing drugs or interventions.

Results from nanoScan® SPECT/CT

Female BALB/c mice were injected with pcDNA 3.1/TSHR 289 into the bilateral gastrocnemius and electroporated every 3 weeks 4 times. The protocol for establishing the GD mouse model was described in a previous article. At week 12, which was the end of the immunization period, 53 of the 70 mice presented increased levels of T4, TSAb and TSBAb. Fifty mice in which GD was successfully established were randomly assigned to five groups (groups A–E). In addition, age-matched mice that were unimmunized and untreated were used as a control for comparisons (group F). Each group included 10 mice.

The study protocol included four immunizations every 3 weeks (groups A–E), followed by a ‘maintenance’ phase that included additional regular immunizations every 3 weeks until the end of the experiment (groups A, C, and E). The siRNA (10 μg/piece) was administered to groups A and B via intraperitoneal (i.p.) injection 3 times 2 weeks after the fourth immunization (week 12), with 2 days between each injection. The ICAM-1 mAb (10 μg/injection) was administered to groups C and D using the same method as the siRNA was administered to groups A and B.

Whole-body ^99mTcO₄ imaging was performed at week 12 (2 weeks after the fourth immunization) and week 18 (the end of the experiment). Each mouse was anesthetized with 3% isoflurane, followed by an intraperitoneal injection of 37 MBq ^99mTcO₄ – (1 mCi/0.1 mL) while the mouse was in a prone position. The scintillation scan was performed 10 min later using the NanoSCAN small animal SPECT/CT with a multipinhole collimator, peak energy of 140 keV, and total acquisition time of only 2 h.

Results show:

• The uptake of ^99mTcO₄ - by the thyroid was increased in the experimental group following the fourth immunization.
• After treatment, compared with the blank group (group F), groups A-E exhibited increased ^99mTcO₄ - uptake in the thyroid.
• ^99mTcO₄ - uptake in the thyroid of group E was higher than that of the other groups.
• No significant differences in ^99mTcO₄ - uptake were observed between the two treatment groups.

Taken together with additional results, treatment of a mouse GD model with an siRNA and ICAM-1 mAb led to marked improvements in several disease parameters.

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