Experimental Validation of Multi-Epitope Peptides Including Promising MHC Class I- and II-Restricted Epitopes of Four Known Leishmania infantum Proteins

Maria Agallou; Evita Athanasiou; Olga Koutsoni; Eleni Dotsika; Evdokia Karagouni

doi:10.3389/fimmu.2014.00268

Experimental Validation of Multi-Epitope Peptides Including Promising MHC Class I- and II-Restricted Epitopes of Four Known Leishmania infantum Proteins

Front Immunol. 2014 Jun 10:5:268. doi: 10.3389/fimmu.2014.00268. eCollection 2014.

Authors

Maria Agallou¹, Evita Athanasiou¹, Olga Koutsoni¹, Eleni Dotsika¹, Evdokia Karagouni¹

Affiliation

¹ Laboratory of Cellular Immunology, Department of Microbiology, Hellenic Pasteur Institute , Athens , Greece.

Abstract

Leishmaniasis is a significant worldwide health problem for which no vaccine exists. Activation of CD4(+) and CD8(+) T cells is crucial for the generation of protective immunity against parasite. Recent trend in vaccine design has been shifted to epitope-based vaccines that are more specific, safe, and easy to produce. In the present study, four known antigenic Leishmania infantum proteins, cysteine peptidase A (CPA), histone H1, KMP-11, and Leishmania eukaryotic initiation factor (LeIF) were analyzed for the prediction of binding epitopes to H2(d) MHC class I and II molecules, using online available algorithms. Based on in silico analysis, eight peptides including highly scored MHC class I- and II-restricted epitopes were synthesized. Peptide immunogenicity was validated in MHC compatible BALB/c mice immunized with each synthetic peptide emulsified in complete Freund's adjuvant/incomplete Freund's adjuvant. CPA_p2, CPA_p3, H1_p1, and LeIF_p6 induced strong spleen cell proliferation upon in vitro peptide re-stimulation. In addition, the majority of the peptides, except of LeIF_p1 and KMP-11_p1, induced IFN-γ secretion, while KMP-11_p1 indicated a suppressive effect on IL-10 production. CPA_p2, CPA_p3, LeIF_p3, and LeIF_p6 induced IFN-γ-producing CD4(+) T cells indicating a TH1-type response. In addition, CPA_p2, CPA_p3, and H1_p1 induced also the induction of CD8(+) T cells. The induction of peptide-specific IgG in immunized mice designated also the existence of B cell epitopes in peptide sequences. Combining immunoinformatic tools and experimental validation, we demonstrated that CPA_p2, CPA_p3, H1_p1, H1_p3, CPA_p2, LeIF_p3, and LeIF_p6 are likely to include potential epitopes for the induction of protective cytotoxic and/or TH1-type immune responses supporting the feasibility of peptide-based vaccine development for leishmaniasis.

Keywords: CD4+IFN-γ+ T cells; CD8+IFN-γ+ T cells; Leishmania eukaryotic initiation factor; cysteine peptidase A; histone H1; in silico analysis; kinetoplastid membrane protein 11; lymphocyte proliferation.