Mass spectrometric identification of an HLA-A*0201 epitope from Plasmodium falciparum MSP-1

Cytotoxic T lymphocytes (CTL) directed against Plasmodium falciparum-derived antigens were shown to play an important role for the protection against malaria. Although several CTL epitopes have been identified from P. falciparum sporozoite-derived antigens, none has been described for the merozoite form. Since the merozoite surface protein (MSP)-1 is a known target of the immune response, we focused on this protein to identify HLA-A*0201-associated epitopes. Using our mass spectrometry-based method [the 'predict-calibrate-detect' (PCD) approach], we were able to identify an MSP-1-derived epitope in the peptide mixture naturally associated with HLA-A*0201 molecules purified from an MSP-1-expressing cell line. CTLs against this epitope were generated from HLA-A*0201 monochain transgenic mice (HHD). They specifically killed MSP-1-expressing HLA-A2-positive target cells. Thus, we describe here the first MHC class I epitope from the merozoite form of P. falciparum. This epitope can be used as a tool for the immunomonitoring of natural or vaccine-induced CTL immune responses against malaria and could eventually be proposed as a component of an anti-malaria peptide-based vaccine.