ABSTRACT
Here, we describe the preliminary results of an experimental vaccination of a self-experimenting healthy volunteer with eight SARS-CoV-2-derived peptides: five predicted to bind to HLA class I molecules (CD8 peptides) and three predicted to bind to HLA-DR molecules (CD4 peptides). The vaccine formulation also included one long and one short CMV-pp65-derived peptide that had previously been administered to the same individual and could thus act as positive controls. It further contained the new adjuvant XS15 and was administered as an emulsion in Montanide as a single subcutaneous (s.c.) injection. Peripheral blood mononuclear cells (PBMCs) isolated from blood drawn on day 36 before vaccination and day 19 after vaccination were assessed using an ex vivo Interferon-γ ELISpot assay. We detected strong vaccine-induced T-cell responses against all four CD4 peptides and against the recall CMV CD8 epitope, but found no immune responses against the five predicted SARS-CoV-2 CD8 peptides. Antibody reactivity against all the SARS-CoV-2 CD4 peptides, as detected using ELISA, was negative or marginal. We interpret these results in terms of the prospects of a therapeutic vaccine to be applied in symptomatic COVID-19 patients. An advantage of this approach is the possibility to assess efficacy or failure within a short time after vaccination.