Abstract

Ex vivo interferon-gamma immune response to thrombospondin-related adhesive protein in coastal Kenyans: longevity and risk of Plasmodium falciparum infection

Flanagan, K. L. Mwangi, T. Plebanski, M. Odhiambo, K. Ross, A. Sheu, E. Kortok, M. Lowe, B. Marsh, K. Hill, A. V.
Am J Trop Med Hyg. 2003; 68421-30

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https://doi.org/

Thrombospondin-related adhesive protein (TRAP) of Plasmodium falciparum is currently being tested in human vaccine studies. However, its natural reactivity in the field remains poorly characterized. More than 40% of 217 Kenyan donors responded in an ex vivo interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay to at least one of 14 20mer peptides spanning 42% of the antigen. Reactivity was comparable from early childhood (>1 year of age) to old age, and the maximal precursor frequency of TRAP-specific cells to all 14 peptides was 1 in 4,000. Prospective follow-up for one year indicated that these low-level ex vivo responses to TRAP did not protect against the subsequent development of malaria. Retesting of selected donors after one year showed a complete change in the reactivity pattern, suggesting that malaria-specific ex vivo IFN-gamma ELISPOT assay responses are short lived in naturally exposed donors, even to conserved epitopes. This study provides important information regarding natural reactivity to a key malaria antigen.