Preparation of human single-chain variable fragment antibodies against anaplastic thyroid carcinoma, and single photon emission‑computed tomography/computed tomography imaging in tumor-bearing nude mice.

Anaplastic thyroid carcinoma (ATC) is the most aggressive malignant thyroid tumor with the worst prognosis, and the response to treatment is poor. We investigated soluble human single-chain variable fragment (scFv) which provides unique information for diagnostics, and for monitoring and optimizing responses to therapy. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of scFv. The expression and relative molecular mass of soluble scFv were assessed by sodium dodecyl sulfate‑polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting, respectively. The chloramine T method was used to label scFv with 131I. The labeling rate and the radiochemical purity were determined. To analyze the distribution of 131I‑scFv in body tissues and organs of nude mice, static single photon emission-computed tomography (SPECT) imaging and single photon emission‑computed tomography/computed tomography (SPECT/CT) image fusion were performed. The relative molecular mass of soluble scFv was ~29 kDa. The labeling rate was 91.64% and the radiochemical purity was 93.3±0.32%. SPECT imaging revealed that 131I-scFv selectively accumulated in tumor tissue. In addition, SPECT/CT image fusion results were in agreement with the biodistribution results. In conclusion, the human scFv antibodies against ATC were successfully generated, and clear imaging of 131I‑scFv in a nude mouse model at 48 h was obtained.