Anti-Plasmodium Activity of Angiotensin II and Related Synthetic Peptides

Plasmodium species are the causative agents of malaria, the most devastating insect-borne parasite of human populations. Finding and developing new drugs for malaria treatment and prevention is the goal of much research. Angiotensins I and II (ang I and ang II) and six synthetic related peptides designated Vaniceres 1-6 (VC1-VC6) were assayed in vivo and in vitro for their effects on the development of the avian parasite, Plasmodium gallinaceum. Ang II and VC5 injected into the thoraces of the insects reduced mean intensities of infection in the mosquito salivary glands by 88% and 76%, respectively. Although the mechanism(s) of action is not completely understood, we have demonstrated that these peptides disrupt selectively the P. gallinaceum cell membrane. Additionally, incubation in vitro of sporozoites with VC5 reduced the infectivity of the parasites to their vertebrate host. VC5 has no observable agonist effects on vertebrates, and this makes it a promising drug for malaria prevention and chemotherapy.

A new thrombospondin-related anonymous protein homologue in Neospora caninum (NcMIC2-like1)

Neospora caninum is an Apicomplexan protozoan that has the dog as a definitive host and cattle (among other animals) as intermediate hosts. It causes encephalopathy in dogs and abortion in cows, with significant loss in worldwide livestock. As any Apicomplexan, the parasite invades the cells using proteins contained in the phylum-specific organelles, like the micronemes, rhoptries and dense granules. The aim of this study was the characterization of a homologue (denominated NcMIC2-like1) of N. caninum thrombospondin-related anonymous protein (NcMIC2), a micronemal protein previously shown to be involved in the attachment and connection with the intracellular motor responsible for the active process of invasion. A polyclonal antiserum raised against the recombinant NcMIC2-like1 functional core (thrombospondin and integrin domains) recognized the native form of NcMIC2-like1, inhibited the in vitro invasion process and localized NcMIC2-like1 at the apical complex of the parasite by confocal immunofluorescence, indicating its micronemal localization. The new molecule, NcMIC2-like1, has features that differentiates it from NcMIC2 in a substantial way to be considered a homologue dagger.

Effects of Plasmodium gallinaceum on hemolymph physiology of Aedes aegypti during parasite development

Insect disease vectors show diminished fecundity when infected with Plasmodium. This phenomenon has already been demonstrated in laboratory models such as Aedes aegypti, Anopheles gambiae and Anopheles stephensi. This study demonstrates several changes in physiological processes of A. aegypti occurring upon infection with Plasmodium gallinaceum, such as reduced ecdysteroid levels in hemolymph as well as altered expression patterns for genes involved in vitellogenesis, lipid transport and immune response. Furthermore, we could show that P. gallinaceum infected A. aegypti presented a reduction in reproductive fitness, accompanied by an activated innate immune response and increase in lipophorin expression, with the latter possibly representing a nutritional resource for Plasmodium sporozoites. (C) 2010 Elsevier Ltd. All rights reserved.