Oral administration with attenuated Salmonella encoding a Trichinella cystatin-like protein elicited host immunity.

Trichinellosis is a public health problem and is regarded as an emergent/re-emergent disease in various countries. The cDNA encoding a cystatin-like protein (Ts-cystatin) was identified by immunoscreening intestinal muscle larvae cDNA libraries with serum from pigs experimentally infected with 20,000 Trichinella spiralis muscle larvae. To study its impact on host immunity, we chose a eukaryotic expression system based on several comparisons of immunogenicity between the two Salmonella typhimurium administration schemes, which indicated that the eukaryotic expression system was superior. Humoral IgG and mucosal IgA were measured to determine the antibody response. To explore whether Th1 and Th2 responses were responsible for the induced protection, Th1- and Th2-specific cellular transcription factors and the cytokine profile were examined. Changes in the T lymphocyte and macrophage populations were detected by flow cytometry. Lastly, parasitological examination was examined. The results showed that Ts-cystatin induced a Th1/Th2-mixed type of immune response and decreased STAT6 transcription. The intestinal adult recovery increased by 10.9% in the Ts-cystatin group, the Ts-cystatin group fecundity rate was decreased by 91%. Furthermore, the number of muscle larvae did not change compared with the control group. In conclusion, our results suggest that Ts-cystatin plays an important role in Trichinella resistance to rapid expulsion by the host and is worth further study.