Original Research

Cellular immune responses induced in vitro by Ehrlichia ruminantium secreted proteins and identification of vaccine candidate peptides

Nontobeko Thema, Alri Pretorius, Selaelo I. Tshilwane, Junita Liebenberg, Helena Steyn, Mirinda van Kleef
Onderstepoort Journal of Veterinary Research | Vol 83, No 1 | a1170 | DOI: https://doi.org/10.4102/ojvr.v83i1.1170 | © 2016 Nontobeko Thema, Alri Pretorius, Selaelo I. Tshilwane, Junita Liebenberg, Helena Steyn, Mirinda van Kleef | This work is licensed under CC Attribution 4.0
Submitted: 03 February 2016 | Published: 30 August 2016

About the author(s)

Nontobeko Thema, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute; Department of Veterinary Tropical Diseases, University of Pretoria, South Africa
Alri Pretorius, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute; Department of Veterinary Tropical Diseases, University of Pretoria, South Africa
Selaelo I. Tshilwane, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute, South Africa
Junita Liebenberg, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute, South Africa
Helena Steyn, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute, South Africa
Mirinda van Kleef, New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute; Department of Veterinary Tropical Diseases, University of Pretoria, South Africa

Abstract

Secreted proteins are reported to induce cell-mediated immunity characterised by the production of interferon-gamma (IFN)-γ. In this study three open reading frames (ORFs) (Erum8060, Erum7760, Erum5000) encoding secreted proteins were selected from the Ehrlichia ruminantium (Welgevonden) genome sequence using bioinformatics tools to determine whether they induce a cellular immune response in vitro with mononuclear cells from needle and tick infected animals. The whole recombinant protein of the three ORFs as well as four adjacent fragments of the Erum5000 protein (Erum5000A, Erum5000B, Erum5000C, Erum5000D) were successfully expressed in a bacterial expression system which was confirmed by immunoblots using anti-His antibodies and sheep sera. These recombinant proteins were assayed with immune sheep and cattle peripheral blood mononuclear cells (PBMCs), spleen and lymph node (LN) cells to determine whether they induce recall cellular immune responses in vitro. Significant proliferative responses and IFN-γ production were evident for all recombinant proteins, especially Erum5000A, in both ruminant species tested. Thus overlapping peptides spanning Erum5000A were synthesised and peptides that induce proliferation of memory CD4+ and CD8+ T cells and production of IFN-γ were identified. These results illustrate that a Th1 type immune response was elicited and these recombinant proteins and peptides may therefore be promising candidates for development of a heartwater vaccine.


Keywords

Bioinformatics; Cytokines; Ehrlichia ruminantium; Secreted proteins; Th1 type immune responses

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Crossref Citations

1. Ehrlichia ruminantium antigens and peptides induce cytotoxic T cell responses in vitro
N. Thema, S.I. Tshilwane, L. Son, R.M. Smith, F.E. Faber, H.C. Steyn, M. van Kleef, J. Liebenberg, A. Pretorius
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doi: 10.1016/j.vetimm.2018.11.012