Genome-wide screening of the novel malaria transmission-blocking vaccine candidates

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Malaria remains one of the leading causes of both morbidity and mortality of humans residing in the tropical countries. The evidence of increasing resistance of the Plasmodium falciparum parasite to chemotherapeutic agents, such as chloroquine, highlights the critical need for an effective vaccine. However, the effective malaria vaccine has never been achieved to date. Since the genomic sequence of P.falciparum together with stage-specific proteome data was completed in October 2002, we have now free access to the genome data to search for novel vaccine candidates. However, one of the bottlenecks for the vaccine development is the high AT content in exons of P.falciparum, which will considerably inhibit the recombinant protein expression using conventional methods. Our strategy is to express recombinant proteins for the characterization of each protein based on the genome sequences of P.falciparum without using synthetic gene. Transmission-blocking vaccines (TBVs) prevent the transmiss … More ion of malaria by inducing antibodies against antigens specifically expressed on the sexual stage parasites. Since well-characterized TBV candidates are only four (Pfs25, Pfs28, Pfs48/45, and Pfs230), it would be necessary to prepare novel TBV candidates as many as possible for a successful TBV development. In order to identify the novel TBV candidates, we searched a combined dataset from genome and transcriptome databases and we selected 192 genes, which are expected to be expressed only in gametocyte stage of P.falciparum. These genes were cloned into plasmids and templates were prepared for transcription through PCR-based procedures, followed by high throughput recombinant protein synthesis by wheat germ cell-free system. Using this approach, we succeeded in obtaining 120 recombinant proteins. After the screening of these recombinant proteins to identify novel TBV candidates with anti-gametocyte monoclonal antibodies, we have identified a novel antigen expressed on the surface of gametocyte stage. Less