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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.

Type

Journal article

Journal

Am J Trop Med Hyg

Publication Date

04/2003

Volume

68

Pages

421 - 430

Keywords

Adolescent, Adult, Aged, Aged, 80 and over, Amino Acid Sequence, Child, Child, Preschool, Enzyme-Linked Immunosorbent Assay, Female, Humans, Immunity, Cellular, Infant, Interferon-gamma, Kenya, Leukocytes, Mononuclear, Longevity, Malaria Vaccines, Malaria, Falciparum, Male, Middle Aged, Molecular Sequence Data, Peptide Fragments, Pilot Projects, Protozoan Proteins, Risk Factors, T-Lymphocytes