Characterisation and expression of Pbs25, a sexual and sporogonic stage specific protein of Plasmodium berghei

Following gametogenesis and fertilisation in the bloodmeal within the mosqu ito midgut, the newly formed zygotes of the malaria parasite develop into m otile invasive ookinetes. During this development, surface molecules are sy nthesised de novo including molecules of 21-28 kDa from the zygote-ookinete stages. An antiserum recognising a 26 kDa protein of Plasmodium berghei wa s used to clone the corresponding gene from a cDNA library, which was shown to be identical to the reported Pbs25 gene sequence. We show here that Pbs 25 was detectable in preparations of gametes 30 min post-gametocyte activat ion, expression continued on zygotes, ookinetes and oocysts indicating ther e is a significant overlap of expression of the two immunogenic zygote-ooki nete proteins belonging to the P25/28 protein family of sexual stage antige ns. Biochemical analysis of Pbs25 demonstrates the presence of a malaria-sp ecific glycosylphosphatidylinositol (GPI) anchor. Antibodies recognising Pb s25 impaired parasite development in the mosquito. (C) 2000 Elsevier Scienc e B.V. All rights reserved.