a, SDS–PAGE gel of purified rPfGARP-A (250 ng). b, c, We analysed rPfGARP-A, as well as extracts prepared from uninfected RBCsand 3D7 trophozoite-infected RBCs by western blot. b, Blots were probed with mouse polyclonal anti-PfGARP-A serum (generated by plasmid immunization) and with anti-MSP2 (rabbit polyclonal serum), which were detected with anti-mouse IgG (red) and anti-rabbit IgG (green). c, Blots were probed with pre-immune mouse serum and anti-MSP2 (rabbit polyclonal serum), detected with anti-mouse IgG (red) and anti-rabbit IgG (green). Data in a–c are representative of five independent experiments. d, GIAs performed on parasites collected from our field site in Muheza, Tanzania, after short-term adaptation to the culture. Assays were performed using polyclonal anti-PfGARP-A antibodies generated by immunizing mice with recombinant protein. Ring-stage malaria parasites from adults (NIH 00710 and NIH 00918) or children (NIH 408551 and NIH 4122821) were cultured in the presence of anti-PfGARP mouse serum at a 1:10 dilution. Negative controls were no antiserum (blue) and pre-immune mouse serum (red). Parasites were cultured for 48 h at 37 °C and ring-stage and early-trophozoite-stage parasites were counted by microscopy. Data are mean ± s.e.m. of five biologically independent replicates. P values were calculated by two-sided non-parametric Mann–Whitney U-test. Data are representative of five independent experiments. e–h, 3D7 P. falciparum parasites were synchronized to the ring stage and plated at 5% parasitaemia in the presence of pre-immune (e, g) and anti-rPfGARP-A (f, h) mouse serum at a 1:10 dilution. Parasites were cultured for 24 h (e, f) or 48 h (g, h), stained with Giemsa and photographed by light microscopy. Images in e–h are representative of three independent experiments. i–l, Purification of anti-PfGARP antibodies from human (i, j) and mouse (k, l) serum. Serum was affinity-purified using PfGARP-A coupled to sepharose beads. The specificity of the purified anti-PfGARP antibodies was determined by western blot on extracts prepared from unsynchronized 3D7 parasite-infected RBCs. In all panels: lane 1, infected RBCs extracted in RIPA buffer; lane 2, uninfected RBCs extracted in RIPA buffer. Blots in i, j were probed with anti-PfGARP purified from serum that was pooled from adults living in a holoendemic area of Tanzania (2 μg ml−1) (i), or with immunoglobulin from malaria-naive adults (2 μg ml−1) (j). Blots in k, l were probed with anti-PfGARP purified from serum that was prepared from PfGARP-A-immunized mice (10 μg ml−1) (k), or immunoglobulin from malaria-naive mice (10 μg ml−1). Blots in i–l are representative of two biologically independent experiments.