Abstract. Because malaria is still a significant problem worldwide, additional control methods need to be developed. The Plasmodium sporozoite is a good target for control measures because it displays dual infectivity for both mosquito and vertebrate host tissues. The Plasmodium falciparum gene, PFE0565w, was chosen as a candidate for study based on data from PlasmoDB, the Plasmodium database, indicating that it is expressed both at the transcriptional and protein levels in sporozoites, likely encodes a putative surface protein, and may have a potential role in the invasion of host tissues. Additional sequence analysis shows that the PFE0565w protein has orthologs in other Plasmodium species, but none outside of the genus Plasmodium. PFE0565w expresses transcript during both the sporozoite and erythrocytic stages of the parasite life cycle, where an alternative transcript was discovered during the erythrocytic stages. Data show that transcript is not present during axenic exoerythrocytic stages. Despite transcript being present in several life cycle stages, the PFE0565w protein is present only during the salivary gland sporozoite stage. Because the PFE0565w protein is present in salivary gland sporozoites, it could be a novel candidate for a pre-erythrocytic stage vaccine.

BackgroundEfforts to control malaria are demanding due to drug-resistant parasites, insecticide-resistant mosquitoes and poor health infrastructure in malaria-endemic countries. Therefore, the research and development of additional malaria control methods are crucial. For host-parasite interactions, surface antigens and secreted proteins are likely to be involved in infectivity and invasion of host tissues and therefore can be effective targets for control by vaccines, drug therapy, or novel mosquito control methods. In an effort to identify and characterize genes that may have a role in host-parasite interaction, this study describes the expression profile of Plasmodium falciparum PF3D7_1363700.MethodsA P. falciparum gene, PF3D7_1363700, was identified by a search of the annotated Plasmodium genome database. Protein alignments of PF3D7_1363700 orthologues from various Plasmodium species were performed to demonstrate protein similarity. Transcript expression profiles of PF3D7_1363700 were determined via reverse-transcriptase PCR and protein expression was investigated by immunofluorescence assays, western blot analysis and green fluorescent trafficking studies.ResultsThe PF3D7_1363700 protein demonstrates significant similarity with orthologues in other Plasmodium species and appears to be unique to Apicomplexans. The PF3D7_1363700 transcription profile demonstrated expression during the intra-erythrocytic, oocyst sporozoite, and salivary gland sporozoite stages while the PF3D7_1363700 protein was only detected during the intra-erythrocytic stages.ConclusionsThis research utilized an in silico approach to identify a well-conserved protein known as PF3D7_1363700. By molecular, biochemical and cellular analyses, PF3D7_1363700 was discovered to be an intra-erythrocytic-specific stage protein that is unique to Apicomplexans.

BackgroundPlasmodium falciparum malaria is a significant problem around the world today, thus there is still a need for new control methods to be developed. Because the sporozoite displays dual infectivity for both the mosquito salivary glands and vertebrate host tissue, it is a good target for vaccine development.MethodsThe P. falciparum gene, PF11_0394, was chosen as a candidate for study due to its potential role in the invasion of host tissues. This gene, which was selected using a data mining approach from PlasmoDB, is expressed both at the transcriptional and protein levels in sporozoites and likely encodes a putative surface protein. Using reverse transcription-polymerase chain reaction (RT-PCR) and green fluorescent protein (GFP)-trafficking studies, a transcript and protein expression profile of PF11_0394 was determined.ResultsThe PF11_0394 protein has orthologs in other Plasmodium species and Apicomplexans, but none outside of the group Apicomplexa. PF11_0394 transcript was found to be present during both the sporozoite and erythrocytic stages of the parasite life cycle, but no transcript was detected during axenic exoerythrocytic stages. Despite the presence of transcript throughout several life cycle stages, the PF11_0394 protein was only detected in salivary gland sporozoites.ConclusionsPF11_0394 appears to be a protein uniquely detected in salivary gland sporozoites. Even though a specific function of PF11_0394 has not been determined in P. falciparum biology, it could be another candidate for a new vaccine.

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