Abstract: Objective To investigate the dynamic expression of transforming growth factor β1(TGF-β1) in subcutaneous muscles of mice infected with Spirometra erinacei and its implication in control of the disease. Methods Morphological observation and PCR detection were performed on the larvae collected from wild Elaphe carinata. A total of 80 Kunming mice (20-25 g) were equally divided into experiment group and control group. Mice in the experiment group were each orally infected with 5 plerocercoids, while those in the control group were not infected. On days 7, 14, 28, and 56 after infection, 10 mice from each group were sacrificed and specimens of the subcutaneous muscle tissues containing pleroceroids were collected, fixed in formaldehyde, and paraffin sections prepared. HE staining was performed to observe pathological alterations and the degree of fibrosis at lesion-surrounding sites. Immunohistochemistry was performed to detect TGF-β1 in subcutaneous muscles. Results PCR resulted in specific COX1 bands of 400 bp, which showed a sequence similarity of > 99% with Spirometra erinacei. HE staining showed that the plerocercoids were packed by inflammatory cysts, and caverns were formed between plerocercoids and the cyst wall, with occasional appearance of serum or blood in the cavern. There were thin layers of fibrous protein and necrotic fragments inside the cyst wall. Early cyst walls were mainly invaded by neutrophils, eosinophils, macrophages, and plasmocyte. There was an enlargement of inflammatory cyst wall following the disease progression. There was a significant fibrous connective tissue hyperplasia and different degrees of fibrosis between the cyst wall and subcutaneous tissue. Immunohistochemistry showed that TGF-β1 was mainly expressed in inflammatory zones surrounding the plerocercoids and around focal fibrous hyperplasia. The level of TGF-β1 increased with time, reached a peak (0.654 5 ± 0.045 5) at 28 days post-infection, and decreased obviously at 56 days (0.346 8 ± 0.030 4). The TGF-β1 levels during days 7-56 post infection ranged from (0.502 6 ± 0.008 2) to (0.346 8 ± 0.030 4), which were all significantly higher than the control [(0.270 0 ± 0.001 6)-(0.274 0 ± 0.005 1)] (P < 0.01). Conclusion The expression of TGF-β1 increases in the early and middle stages of infection. The immune inhibition effect of TGF-β1 is disadvantageous for clearing and control of plerocercoids in subcutaneous muscle tissues.

Key words: Spirometra erinacei, Plerocercoid, Transforming growth factor β1;, HE staining, Immunohistochemistry