Identification and characterization of CD4+ T cell epitopes present in Trichinella spiralis paramyosin

•CD4+ T cell epitopes in paramyosin of Trichinella spiralis were predicted.•Predicted CD4+ T cell epitopes were verified with experiments.•Four identified CD4+ T cell epitopes induced both Th1 and Th2 responses.

Trichinellosis is a worldwide zoonosis and vaccinating swine with a potent vaccine is a practical approach to prevent Trichinella infections in China. Paramyosin of T. spiralis (Ts-Pmy) was shown in our previous work to be a good vaccine candidate against Trichinella infections. Because CD4+ T cells play a crucial role in effective immunity against T. spiralis infection, identifying CD4+ T cell epitopes of paramyosin is crucial for constructing a chimeric subunit epitope vaccine. Twelve CD4+ T cell epitopes of Ts-Pmy with the highest scores were predicted and synthesized as peptides. Five of the twelve peptides, P2, P3, P4, P5 and P12, induced strong splenocyte proliferation and secretion of the Th2 cytokines IL-4 and IL-5 from rTs-Pmy-immunized mouse splenocytes. To assess the immunogenicity of CD4+ T cell epitopes in vivo, splenocytes from mice immunized with individual peptides were stimulated with the corresponding peptides. P2, P3, P4 and P5 induced strong cell proliferation and secretion of both Th1 (INF-γ, IL-2) and Th2 (IL-4, IL-5) cytokines. The results indicate that the peptides P2, P3, P4 and P5 are immunodominant CD4+ T cell epitopes of Ts-Pmy. This study will facilitate the design of an effective epitope-based multivalent subunit vaccine against Trichinella infections.