Functional study of merozoite-related genes based on the precise transcriptome of Plasmodium falciparum chromosome

Malaria accounts for an enormous burden of disease globally, with Plasmodium falciparum accounting for the majority of malaria. Artemisinin resistance and lack of effective vaccines threaten the control of malaria. The whole genome sequences, transcriptomics and proteomics have provided critical information on the expression profiles of malarial proteins during the parasite’s life cycle.However, the current transcriptomic data of P. falciparum is derived from a previous DNA microarray, which based on an incomplete P. falciparum genome sequences and RNA extracted from imprecisively synchronized parasites. Compared to DNA/cDNA microarray and RNA-seq, realtime-PCR is more accurate and used widely for verification and replenishment of the P. falciparum transcriptomic data. During infection with Plasmodium spp., the merozoite form of the parasites invades red blood cells and replicates inside them. It is during the blood-stage of infection that malaria disease occurs. Therefore, understanding merozoite invasion, and targeting merozoite proteins by novel vaccines and therapeutics have been important areas of research. Several merozoite surface proteins show strong potential as malaria vaccines. However, of the ~100 vaccine candidates currently under investigation, more than 60% are based on only four parasite antigens. New antigen candidates are urgently needed. The discovery of plasmodium antigens tended to depend on infected serum from human or animals in the previous studies. Most antigens recognized by this approach were immunodominant or possessed immunodominant regions made of repeats. Although immunodominant antigens induce very strong antibody responses, recent studies have shown that they did not offer adequate protection when tested as subunit vaccines in clinical trials, suggesting that these antigens might be used by the parasites for immune evasion, such as CSP and AMA1. In the previous study, we screened the transcriptome of P. falciparum 3D7 parasites from different stages of its life cycle. Analysis of chromosome 14 transcriptome showed a batch of 87 genes that had stage-specific high-level expression in the merozoite stage, compared to the other stages, including ring-stage, trophozoites and immature schizonts. In the 87 genes, 64 genes are unkown. These genes maight play important roles in the invasion progress of merozoites into human erythrocytes. Gene knockout will also be carried out using CRISPR/Cas9 technology to find out the critical genes in the invasion processes. Furthermore, the antibody response of all these antigens in serum from P. falciparum infected human beings will be examined to analyze the relationship between immunogenicity and related protection of P. falciparum antigens. Then, chimeras of P. beighei ANKA with homologous genes replaced by indicated P. falciparum genes will be constructed. Mice vaccinated with recombinant P. falciparum proteins will be challenged with the corresponding chimera parasites to evaluate the value of the proteins as potential vaccine antigens. These studies will discover potential antigen candidates of malaria vaccines and provide evidence for the value of immunodominant and non-immunonominant antigens in malaria vaccine design.

Project details

Basic Science
Immunology

Jan 2017 — Dec 2020

$83,889

China