RNAi-Mediated Silencing of Paramyosin Expression in Trichinella spiralis Results in Impaired Viability of the Parasite

BACKGROUND Trichinella spiralis expresses paramyosin (Ts-PMY) not only as a structural protein but also as an immunomodulatory protein to protect the worm from being attacked by host complement components. In this study, the functions of PMY in the viability and the growth development of T. spiralis were confirmed at the first time by silencing the gene function with RNA interference technique. METHODS AND FINDINGS To understand its functions in the viability of the worm, we used RNA interference to silence the expression of Ts-pmy mRNA and protein in the parasite. Significant silencing of Ts-pmy mRNA expression in larval and adult T. spiralis was achieved by siRNA and dsRNA through soaking and electroporation. Electroporation of T. spiralis larvae with 8 µM siRNA1743 or 100 ng/µl dsRNA-PF3 resulted in 66.3% and 60.4% decrease in Ts-pmy transcript and 52.0% and 64.7% decrease in Ts-PMY protein expression, respectively, compared with larvae treated with irrelevant control siRNA or dsRNA. Larvae treated with siRNA1743 displayed significant reduction in molting (40.8%) and serious surface damage as detected with SYTOX fluorescent staining. Infection of mice with larvae electroporated with Ts-pmy siRNA1743 resulted in 37.6% decrease in adult worm burden and 23.2% decrease in muscle larvae burden compared with mice infected with control siRNA-treated larvae. In addition, adult worms recovered from mice infected with siRNA-treated larvae released 24.8% less newborn larvae. CONCLUSION It is the first time RNAi was used on T. spiralis to demonstrate that silencing PMY expression in T. spiralis significantly reduces the parasite's viability and infectivity, further confirming that Ts-PMY plays an important role in the survival of T. spiralis and therefore is a promising target for vaccine development.