Formation of the circumsporozoite protein of Plasmodium falciparum in Anopheles stephensi.

The place and time of synthesis of the circumsporozoite protein of P. falciparum was analysed with a monoclonal antibody directed against the (NANP)3 repetitive epitope of the CS protein. By using an indirect fluorescent antibody test the epitope could be detected on the oocyst 7 days after infection and 3 days before the appearance of mature sporozoites. Using the Western blot technique, 3 polypeptides from midgut preparations were recognized by the (NANP)3-specific monoclonal antibody from the day 9 of infection onwards. The circumsporozoite precipitation reaction could be induced in sporozoites from either the midgut or the salivary glands 11 days after a blood meal. A similar reactivity of midgut-sporozoites and salivary gland-sporozoites was observed with antisporozoite antisera. Not all sporozoites recovered from the midgut showed a precipitation reaction.