Cellular immune responses inducedin vitrobyEhrlichia ruminantiumsecreted proteins and identification of vaccine candidate peptides.
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.
New Generation Vaccines Programme, Agricultural Research Council-Onderstepoort Veterinary Institute; Department of Veterinary Tropical Diseases, University of Pretoria. theman@arc.agric.za.
Nontobeko
N
Thema
Alri
A
Pretorius
Selaelo I
SI
Tshilwane
Junita
J
Liebenberg
Helena
H
Steyn
Mirinda
M
Van Kleef
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001428:Bacterial Vaccines / Q000276:immunology*; D002417:Cattle; D016995:Ehrlichia ruminantium / Q000235:genetics / Q000276:immunology*; D006357:Heartwater Disease / Q000517:prevention & control*; D007114:Immunization / Q000662:veterinary; D007371:Interferon-gamma / Q000096:biosynthesis; D008213:Lymphocyte Activation; D016366:Open Reading Frames; D012756:Sheep
D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D007371:Interferon-gamma