Ehrlichia ruminantium antigens and peptides induce cytotoxic T cell responses in vitro

Abstract

Since CD8 + T cells play an important role in resistance to infection with heartwater, effective vaccines against this disease will likely require identification of antigens that contain CD8 + T cell epitopes responsible for cytotoxic T lymphocyte (CTL) responses. With the use of the fluorescent antigen-transfected target cell (FATT)-CTL assay, IFN-γ ELISPOT and flow cytometry, peptides that induce CTL, proliferation of CD8+T cells and IFN-γ production were identified as possible target antigens for vaccine development. Of particular relevance was the finding that different peptides from different antigens were able to elicit varied cytotoxic activities by immune peripheral blood mononuclear cells (PBMC) from heartwater immune tick-infected sheep. Several peptides derived from Erum0660, Erum2330, Erum2540, Erum2580 and Erum5000 induced CTL in immune sheep PBMC. Peptide Erum2540-6 was the only peptide that induced significant CTL, CD8 + CD45RO + and CD8 + IFN-γ + by PBMC from all three sheep, and Erum2540 and p2540-20 induced the highest % CTL response in all three outbred sheep. These results suggest that these epitopes may be of major importance in heartwater recombinant vaccine development.

Th1 and Th2 epitopes of Cowdria polymorphic gene 1 of Ehrlichia ruminantium

“…The variability in response of the two sheep to the same antigen observed in the study can be attributed to the usage of outbred animals (genetic variability), which has been reported by other groups (Esteves et al 2004 ; Thema et al 2019a , 2019b ). Major histocompatibility complex (MHC) typing of sM2 (results not shown) and s6823 (Thema et al 2016 ) showed different ovar-DRB1 alleles at exon 20, s6823: *0201, 0801 and sM2: *0323, 0333.…”

“…The 1H12 cocktail DNA vaccine containing four E. ruminantium genes provided 100% protection against a virulent needle challenge in sheep (Collins et al 2003 ) but only 20% protection in sheep to a natural tick challenge in the field (Pretorius et al 2008 ). Thereafter, selected 1H12 epitopes and multiple-vaccine candidate E. ruminantium epitopes that induce varied cellular immune responses (Thema et al 2019a , 2019b ) were combined in a multi-epitope DNA vaccine. This vaccine induced 60% protective efficacy in sheep after a laboratory tick challenge (Tshilwane et al 2019 ).…”

A multi-epitope DNA vaccine co-administered with monophosphoryl lipid A adjuvant provides protection against tick transmitted Ehrlichia ruminantium in sheep

“…ELISpot assay was performed in triplicate wells using the Bovine IFN-γ ELISpot PLUS kit (Mabtech) according to the manufacturer's instructions. Following stimulation, cell surface staining was performed as described previously [3,4].…”

“…A successful heartwater DNA vaccine might result from multi-epitope DNA vaccines that can elicit similar immune responses. Previously, we identified CD4 + T cell and CD8 + cytotoxic T lymphocyte (CTL) epitopes from the following E. ruminantium antigens: Erum2540; Erum7140; Erum7320; Erum7350; Erum7620; and Erum8010 [3,4]. Four of the epitopes induced positive CTL responses, proliferation of CD8 + T cells as well as production of IFN-γ by these cells [3].…”

“…Previously, we identified CD4 + T cell and CD8 + cytotoxic T lymphocyte (CTL) epitopes from the following E. ruminantium antigens: Erum2540; Erum7140; Erum7320; Erum7350; Erum7620; and Erum8010 [3,4]. Four of the epitopes induced positive CTL responses, proliferation of CD8 + T cells as well as production of IFN-γ by these cells [3]. Eight could induce IFN-γ production by memory CD4 + T cells in addition to expression of other Th1 cytokines [4].…”