Merozoite invasion properties of P. falciparum W2mef, FCR3, Dd2, 3D7 and HB3 clones.

(A) Comparison of merozoite invasion inhibition with αrRII-3 and αrtRVIII, including pre-immune serum in 1∶10 and 1∶640 dilutions. Positive control was the invasion of merozoites into the normal complete medium. The error bar denotes the SE. * p<0.001, indicating that the invasion of W2mef, FCR3 and Dd2 were successfully inhibited by αrRII-3, compared to 3D7 and HB3. + p<0.05 indicating that Dd2 exhibit an intermediate sensitivity to inhibitory antiserum as compared to W2mef and FCR3. (B) Parasites were also assayed for their ability to invade neuraminidase-treated erythrocytes (1mU/ml final). For each parasite clone, the percentage of inhibition of the ability to invade neuraminidase-treated erythrocytes (vertical axis) is plotted against the percentage of invasion inhibition of αrRII-3 in a 1∶10 dilution (horizonal axis). Western blot of enriched culture supernatant from all 5 clones used in this study and probed with αrRII-3, αrtRVIII and αSERA5 was shown in the insert of (B). No RH1 protein was detected in 3D7 and HB3 clones compared with W2mef, Dd2 and FCR3.