Parasites of the phylum Apicomplexa include many important human and veterinary pathogens such as Plasmodium (malaria), Toxoplasma (a leading opportunistic infection associated with AIDS and congenital neurological birth deffects), and Eimeria (an economically significant disease of poultry and cattle). Recent studies have identified an unusual organelle in these parasites: a plastid that appears to have been acquired by secondary endosymbiosis of a green alga. The replication of this apicoplexan plastid (apicoplast) can be specifically inhibited by certain drugs and antibiotics leading to death of the parasite of which the kinetics resemble those observed after exposure to clindamycin and macrolide antibiotics. The Toxoplasma apicoplast contains a 35 Kb circular DNA, the replication of which is specifically inhibited by the gyrase inhibitor Ciprofloxanine. This leads to the death of the parasites in a way similar to that described for anumber of antibiotics. This organelle seems to provide an effective target for parasiticidal chemotherapy. (See Fichera and Roos, A plastid organelle as drug target in apicomplexan parasites. Nature 390 27 November 1997, pages 407-409).
created by :Fred Opperdoes