Elsevier

Veterinary Parasitology

Volume 231, 15 November 2016, Pages 59-62
Veterinary Parasitology

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

https://doi.org/10.1016/j.vetpar.2016.06.022Get rights and content

Highlights

  • 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.

Abstract

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.

Introduction

Trichinellosis is a widespread food-borne zoonosis found throughout the world, and the parasitic nematode Trichinella spiralis is one of the most common etiologic agents of this disease. As infected pork is the major source of infection in China (Cui and Wang, 2011), development of a transmission-blocking vaccine to prevent swine infection would be a practical contribution to disease control. A subunit vaccine based on multiple protective epitopes of several vaccine antigens may have many advantages compared to whole-protein antigens. Because CD4+ T cells play a crucial role in effective immunity against T. spiralis infection, identifying CD4+ T cell epitopes of vaccine antigens is crucial to construct a chimeric subunit epitope vaccine.

Our previous studies have shown that recombinant Ts-Pmy protein (rTs-Pmy) is a good vaccine candidate that induces protective immunity, with muscle larvae reduction from 33.7% to 36.7% in BALB/c mice against challenge with T. spiralis larvae (Yang et al., 2010, Yang et al., 2008). In the present study, CD4+ T cell epitopes of Ts-Pmy were predicted using an in silico algorithm, and twelve epitopes with the highest scores were synthesized as peptides. The efficacy of these synthesized peptides was determined by stimulating lymphocytes from mice immunized with rTs-Pmy or with individual peptides and assessing the immunogenicity of the epitopes based on their ability to induce Th1 or Th2 responses. This study will facilitate the design of an effective epitope-based subunit vaccine against Trichinella infections.

Section snippets

Materials and methods

Based on the BALB/c mouse model, H-2d restricted CD4+ T cell epitopes (I-Ad and I-Ed) of Ts-Pmy were predicted using the SYFPEITHI database. Seven I-Ad and five I-Ed restricted epitopes predicted with the highest scores (Table 1) were synthesized as peptides by the AVIVA Systems Biology Company (Beijing, China). Six-seven week-old female BALB/c mice were subcutaneously immunized with 25 μg of rTs-Pmy or individual peptide emulsified with the adjuvant ISA50 V2 (SEPPIC, France), then boosted twice

Results and discussion

For the identification of CD4+ T cell epitopes on Ts-Pmy in vitro, splenocytes were isolated from mice immunized with rTs-Pmy and stimulated individually with the selected 12 epitope peptides. The T cell proliferation results showed that candidate epitope peptides P2, P3, P4, P5 and P12 stimulated the highest levels of proliferation similar to rTs-Pmy compared to other candidate peptides (Fig. 1, p < 0.01). The results of the ELISPOT assay demonstrated that the Th2 cytokine IL-4 and IL-5 levels

Conflict of interest

No financial or personal relationships are maintained with other people or organizations that could inappropriately influence or bias this paper.

Acknowledgement

This work was supported by grants from the National Natural Science Foundation of China (81572015, 81371837, 81201312).

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