Protective Immunity against Trichinella spiralis Infection Induced by a Multi-Epitope Vaccine in a Murine Model

Trichinellosis is one of the most important food-borne parasitic zoonoses throughout the world. Because infected pigs are the major source of human infections, and China is becoming the largest international producer of pork, the development of a transmission-blocking vaccine to prevent swine from being infected is urgently needed for trichinellosis control in China. Our previous studies have demonstrated that specific Trichinella spiralis paramyosin (Ts-Pmy) and Ts-87 antigen could provide protective immunity against T. spiralis infection in immunized mice. Certain protective epitopes of Ts-Pmy and Ts-87 antigen have been identified. To identify more Ts-Pmy protective epitopes, a new monoclonal antibody, termed 8F12, was produced against the N-terminus of Ts-Pmy. This antibody elicited significant protective immunity in mice against T. spiralis infection by passive transfer and was subsequently used to screen a random phage display peptide library to identify recognized epitopes. Seven distinct positive phage clones were identified and their displayed peptides were sequenced. Synthesized epitope peptides conjugated to keyhole limpet hemocyanin were used to immunize mice, four of which exhibited larval reduction (from 18.7% to 26.3%, respectively) in vaccinated mice in comparison to the KLH control. To increase more effective protection, the epitope 8F7 that was found to induce the highest protection in this study was combined with two other previously identified epitopes (YX1 from Ts-Pmy and M7 from Ts-87) to formulate a multi-epitope vaccine. Mice immunized with this multi-epitope vaccine experienced a 35.0% reduction in muscle larvae burden after being challenged with T. spiralis larvae. This protection is significantly higher than that induced by individual-epitope peptides and is associated with high levels of subclasses IgG and IgG1. These results showed that a multi-epitope vaccine induced better protective immunity than an individual epitope and provided a feasible approach for developing a safer and more effective vaccine against trichinellosis.