The Host Protein Aquaporin-9 is Required for Efficient Sporozoite Entry into Human Hepatocytes.

Hepatocyte invasion by sporozoites represents a promising target for innovative antimalarial therapy, but the molecular events mediating this process are still largely uncharacterized. We previously showed that sporozoite entry into hepatocytes strictly requires CD81. However, CD81-overexpressing human hepatoma cells remain refractory to infection, suggesting the existence of additional host factors necessary for sporozoite entry.

Two Plasmodium 6-Cys family-related proteins have distinct and critical roles in liver-stage development.

The 10 Plasmodium 6-Cys proteins have critical roles throughout parasite development and are targets for antimalaria vaccination strategies. We analyzed the conserved 6-cysteine domain of this family and show that only the last 4 positionally conserved cysteine residues are diagnostic for this domain and identified 4 additional "6-Cys family-related" proteins. Two of these, sequestrin and B9, are critical to Plasmodium liver-stage development.

Persistence and activation of malaria hypnozoites in long-term primary hepatocyte cultures.

Malaria relapses, resulting from the activation of quiescent hepatic hypnozoites of Plasmodium vivax and Plasmodium ovale, hinder global efforts to control and eliminate malaria. As primaquine, the only drug capable of eliminating hypnozoites, is unsuitable for mass administration, an alternative drug is needed urgently. Currently, analyses of hypnozoites, including screening of compounds that would eliminate them, can only be made using common macaque models, principally Macaca rhesus and Macaca fascicularis, experimentally infected with the relapsing Plasmodium cynomolgi.

Skin-draining lymph node priming is sufficient to induce sterile immunity against pre-erythrocytic malaria.

The Plasmodium-infected hepatocyte has been considered necessary to prime the immune responses leading to sterile protection after vaccination with attenuated sporozoites. However, it has recently been demonstrated that priming also occurs in the skin. We wished to establish if sterile protection could be obtained in the absence of priming by infected hepatocytes.

Assessing the adequacy of attenuation of genetically modified malaria parasite vaccine candidates.

The critical first step in the clinical development of a malaria vaccine, based on live-attenuated Plasmodium falciparum sporozoites, is the guarantee of complete arrest in the liver. We report on an approach for assessing adequacy of attenuation of genetically attenuated sporozoites in vivo using the Plasmodium berghei model of malaria and P. falciparum sporozoites cultured in primary human hepatocytes.

Towards an in vitro model of Plasmodium hypnozoites suitable for drug discovery.

Background: Amongst the Plasmodium species in humans, only P. vivax and P. ovale produce latent hepatic stages called hypnozoites, which are responsible for malaria episodes long after a mosquito bite.

Gene disruption of Plasmodium falciparum p52 results in attenuation of malaria liver stage development in cultured primary human hepatocytes.

Difficulties with inducing sterile and long lasting protective immunity against malaria with subunit vaccines has renewed interest in vaccinations with attenuated Plasmodium parasites. Immunizations with sporozoites that are attenuated by radiation (RAS) can induce strong protective immunity both in humans and rodent models of malaria. Recently, in rodent parasites it has been shown that through the deletion of a single gene, sporozoites can also become attenuated in liver stage development and, importantly, immunization with these sporozoites results in immune responses identical to RAS.

Scavenger receptor BI boosts hepatocyte permissiveness to Plasmodium infection.

Infection of hepatocytes by Plasmodium falciparum sporozoites requires the host tetraspanin CD81. CD81 is also predicted to be a coreceptor, along with scavenger receptor BI (SR-BI), for hepatitis C virus. Using SR-BI-knockout, SR-BI-hypomorphic and SR-BI-transgenic primary hepatocytes, as well as specific SR-BI-blocking antibodies, we demonstrate that SR-BI significantly boosts hepatocyte permissiveness to P.

New approach for high-throughput screening of drug activity on Plasmodium liver stages.

Plasmodium liver stages represent potential targets for antimalarial prophylactic drugs. Nevertheless, there is a lack of molecules active on these stages. We have now developed a new approach for the high-throughput screening of drug activity on Plasmodium liver stages in vitro, based on an infrared fluorescence scanning system.

Trypanosomatid protozoa: a simplified DNA isolation procedure.

A non-toxic and versatile protein salting-out DNA extraction method is here described for convenient and rapid extraction of nuclear DNA molecules from trypanosomatids. The procedure just involves four manipulations, does not require any organic solvent, and is performed in less than 1h in a single tube. DNA yields obtained were similar to those from commercial kits and phenol-chloroform procedures.