The Immune Evaluation Of Novel Malaria Vaccine Candidates In Rodent Models

Malaria as a kind of insect-borne infectious diseases, is prevalent in tropical and subtropical regions. It is known that malaria, HIV/AIDS, and tuberculosis are the most serious infectious diseases to human beings. The World Health Organization estimates that there are about 3.2 billion people at risk of malaria, only in 2015, there were 214 million new cases and 438000 deaths. Plasmodium falciparum as one of thefive malaria parasite species to infect humans, is the main reason for high morbidity and mortality in malaria. Female anopheles and humans are the hosts of Plasmodium falciparum, to control the pathogenic role of Plasmodium to humans, it is mainly inhibition of the development and reproduction of parasites in the human body, and inhibition of parasite invasion of red blood cells is one of the key points to prevent the occurrence of malaria. So erythrocytic stage malaria vaccine has become the focus on malaria control and elimination.Heparin molecular is the important receptors of identification red blood cells of malaria parasites, which can mediate the formation of rosettes, the attachment between infected and uninfected RBCs, and also participate inmerozoites of the invasion erythrocytes. Previous study showed that part of P. falciparum proteins can specifically bind to heparin, most parasite proteins associated with invasion are heparin-binding proteins. PF3D7₁361800 and PF3D7₀811600 are heparin-binding proteins, which have more peptides in combination with heparin, by affinity chromatography and high-throughput proteomic analysis. The study found that the two proteins located on the the surface of merozoites, had certain immunogenicity. The specific antibodies of them could inhibite invasion of merozoites, so the two proteins are likely to be a potential candidate antigens of malaria vaccine.In this study,to further test its feasibility as a malaria vaccine antigen used in clinical trials, we found that PF3D7₁361800 and PF3D7₀811600first cons erved in Plasmodium by bioinformatic analysis. Then, we selected the homolog ous genes of Plasmodium bergheiPBANKA₁3780 and PBANKA₁42590 as r esearch subjects and analyzedtheir antigenic properties in mice. First we chose the carboxyl terminus gene fragment of PBANKA₁13780 and PBANKA₁425 90, ligated them into expression vectors pET-28a and pGEX-4T-1, expressed in prokaryotic and purified the recombinant proteins, successfully obtained rPBA NKA₁13780-963-His, rPBANKA₁42590-660-His, rPBANKA₁13780-963-GST and rPBANKA₁42590-660-GST, rPBANKA₁13780-963-His and rPBANKA₁4 2590-660-His have immunogenicity and reactogenicity by ELISA and Western Blot; His-tag recombinant proteins mixed with Freund’s adjuvant in equal volu mes, immunized BALB/c mice, to evaluate the protective effect by immune pr otection test, the data indicated that the mice infected with Plasmodium berghei has better protective effect, the parasitemia and mortalitydeclined significantly. To test whether immune protection from antibodies, we used sera protection tes t, the results were in conformity with immune protection test, indicated that th e protection was from antibodies induced after vaccination. The results proved that P. falciparum?PF3D7₁361800 and PF3D7₀811600 can be a candidate for malaria erythrocytic stage vaccine.