Expression, partial purification and immunogenicity of fragments of the knob protein of Plasmodium falciparum

Three structural domains of the histidine-rich knob protein (KP) of Plasmodium falciparum were expressed in Escherichia coli. A single-step purification scheme was devised to obtain great enrichment of expressed polypeptides for use in subsequent experiments. Immune human sera from Africa, South-East Asia and South America were tested for reactivity with each of the expressed fragments. While the two fragments which represented the central and C-terminal regions of KP showed a strong reactivity with all the antisera which were tested, the N-terminal fragment which contains the repetitive histidine-rich sequences showed almost no reactivity.