Friday, July 25, 2008

The mother of all parasites

Future Microbiol. 2008 Aug;3:391-395

The mother of all parasites

Okamoto N, McFadden GI.

School of Botany, University of Melbourne, VIC 3010, Australia and, Department of Botany, University of Birtish Columbia, BC, V6T 1Z4, Canada. , School of Botany, University of Melbourne, VIC 3010, Australia.

Evaluation of: Moore RB, Obornik M, Janouskovec J et al.: A photosynthetic alveolate closely related to apicomplexan parasites. Nature 451(7181), 959-963 (2008). Malaria and related apicomplexan parasites contain a relict plastid (apicoplast) that is a promising drug target. The apicoplast has been argued to derive from either an engulfed red or green alga. The discovery of the first photosynthetic apicomplexan, dubbed Chromera velia, with a fully functional plastid resolves the debate, clearly showing that the relict plastid is derived from a modified red alga. Intriguingly, C. velia is a coral symbiont and thus reminiscent of the closely related dinoflagellate symbionts (zooxanthellae) vital to corals and many other invertebrates. Symbiosis and parasitism are thus wide-spread in both the dinoflagellates and apicomplexans, suggesting that modern parasites like Plasmodium spp. and Toxoplasma likely started out as mutualistic symbionts that initially nourished their animal hosts before turning to parasitism. These symbiotic/parasitic relationships thus extend back in evolutionary time to the earliest origins of the animals, which means that either as parasites or symbionts, these protists have been interacting with the animal immune system since its inception. As a consequence of this protracted dance, malaria parasites are exquisitely well-equipped to evade our immune system: a sobering harbinger for malaria vaccine prospects.

PMID: 18651810 [PubMed - as supplied by publisher]

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