A novel method for development of malaria vaccines using full-length cDNA libraries

Screening of novel malaria DNA vaccine candidates using full-length cDNA library

No licensed malaria vaccine exists, in spite of intensive development efforts. We have been investigating development of a DNA vaccine to prevent malaria infection. To date, we have established a full-length cDNA expression library from the erythrocytic-stage murine malaria parasite, Plasmodium berghei. We found that immunization of mice with combined 2000 clones significantly prolonged survival after challenge infection and that splenocytes from the immunized mice showed parasite-specific cytokine production. We determined the 5'-end one-pass sequence of these clones and mapped a draft genomic sequence for P. berghei for use in screening vaccine candidates for efficacy. In this study, we annotated these cDNA clones by comparing them with the genomic sequence of Plasmodium falciparum. We then divided them into several subsets based on their characteristics and examined their protective effects against malaria infection. Consequently, we selected 104 clones that strongly induced specific IgG production and decreased the mortality rate in the early phase. Most of these 104 clones coded for unknown proteins. The results suggest that these clones represent potential novel malaria vaccine candidates.

The Schistosoma mansoni transcriptome: an update

Large scale EST sequencing projects have been carried out for Schistosoma mansoni and Schistosoma japonicum. This update will briefly review the most recent accomplishments in the area and discuss the use of EST data for the purposes of gene discovery, gene model development, genome annotation and SNP analysis. In addition, the use of ESTs for studying other features of the transcriptome such as splice site and transcription initiation variants will be discussed as well as approaches to assigning function to unknown transcripts. Although EST sequencing has contributed much for schistosome research, other data mining possibilities exist, including the identification of putative drug and vaccine targets.

Falciparum Malaria

Malaria is one of the most common infectious diseases in the world today, being the most important parasitic infection, and Plasmodium falciparum is the organism responsible for most of the mortality [1]. It has been estimated that approximately 300–500 million people contract malaria every year, with approximately 1–2 million deaths, most of these occurring in children [1–5]. Plasmodium falciparum, Mycobacterium tuberculosis and measles currently compete for the title of the single most important pathogen causing human morbidity and mortality [2, 3]. Infection with Plasmodium falciparum has a wide variety of potential clinical consequences [4, 6, 7].

Comparasite: a database for comparative study of transcriptomes of parasites defined by full-length cDNAs

Comparasite is a database for comparative studies of transcriptomes of parasites. In this database, each data is defined by the full-length cDNAs from various apicomplexan parasites. It integrates seven individual databases, Full-Parasites, consisting of numerous full-length cDNA clones that we have produced and sequenced: 12 484 cDNA sequences from Plasmodium falciparum, 11 262 from Plasmodium yoelii, 9633 from Plasmodium vivax, 1518 from Plasmodium berghei, 7400 from Toxoplasma gondii, 5921 from Cryptosporidium parvum and 10 966 from the tapeworm Echinococcus multilocularis. Putatively counterpart gene groups are clustered and comparative analysis of any combination of six apicomplexa species is implemented, such as interspecies comparisons regarding protein motifs (InterPro), predicted subcellular localization signals (PSORT), transmembrane regions (SOSUI) or upstream promoter elements. By specifying keywords and other search conditions, Comparasite retrieves putative counterpart gene groups containing a given feature in common or in a species-specific manner. By enabling multi-faceted comparative analyses of genes of apicomplexa protozoa, monophyletic organisms that have evolved to diversify to parasitize various hosts by adopting complex life cycles, Comparasite should help elucidate the mechanism behind parasitism. Our full-length cDNA databases and Comparasite are accessible from .

Advances in vaccine development against the pre-erythrocytic stage of Plasmodium falciparum malaria

With approximately 2.4 billion people at risk, Plasmodium falciparum malaria infection caused by an infectious bite of an Anopheles mosquito continues to be a major cause of mortality and morbidity, mainly in the tropics and subtropics. Measures to control the mosquito vector on a broad scale are expensive and need to be maintained continuously. The rapid emergence of parasite strains that are resistant to affordable drugs highlights the urgent need for a cheap and effective vaccine. Candidate vaccines that have been developed to date target different stages of the parasite life cycle. This review describes the recent advances in the development of a vaccine that aims to terminate the infection at its first stage in the liver. The candidate vaccines that are currently under clinical evaluation are introduced and the results from recent trials discussed. The review aims to explain the immunologic challenges a successful vaccine has to meet, as well as the different strategies that are currently employed in an attempt to induce a protective immune response. Furthermore, an outline of available options to be tested in the near future will be presented.