Effect Of ?-turn Structure On The Properties Of Amyloidogenic MSP2 Peptide As Antimalarial Drug/Vaccine

Malaria is one of the most serious insect-borne infectious diseases in the world,causing more than 200 million infection and more than 400,000 death.At present,although artemisinin plays a significant role in curing malaria,the resistance of malaria parasites to drugs such as artemisinin cannot be ignored.Therefore,researches aiming to develop other safe and effective antimalarial drugs/vaccines to control malaria are necessary.MSP2,the second most abundant protein on the surface of the merozoites of Plasmodium falciparum,apperares to be aggregated on the malarial surface and thereby disrupt the cell membrane to facilitate invasion into the host.MSP2 and peptides derived from its functional N-terminal region have been shown to be potential antimalarial drugs/vaccines.However,in the previous MSP2 vaccine developments,the problems of the safety and effectiveness of the vaccine caused by MSP2's aggregation and membrane disruption were neglected.Studies have shown that the MSP21-25 sequence at the N-terminus of MSP2 protein is a key region for the formation of amyloid fibrils,in which the MSP28-15 sequence is the core of amyloid fibrils,while the MSP215-22 is where one of the MSP2 epitopes is locateed.In this study,we designed WT-MSP28-22 mutants by site-directed substitution and insertionto compose ?-turn prone sequence,then measured their aggregation,interaction with membranes,and antigenicity.Among them,M5-MSP2(refered to as M5 hereafter)was a variant with a strong ?-turn prone sequence inserted within MSP2s-22.Aggregation kinetics monitored by ThT fluorescence and turbidity showed that M5 did not aggregate while could inhibit the aggregation of WT-MSP28-22;SEC showed that M5 adopted monomeric or dimeric form;TEM showed M5 did not form mature fibrils or oligomers.In addition,M5 neither interacted with mimetic membranes nor disrupted the membrane,while could inhibit WT-MSP28-22 membrane interaction and membrane desruption;Indirect ELISA,aggregation kinetics,and fluorescence leakage assays showed that,polyclonal antibodies prepared with M5 as antigen,interacted effectively with both M5 and WT-MSP2s-22,and the interaction inhibited WT-MSP28-22 aggregation,membrane interaction and membrane disruption.Our results indicate that insertion of P prone sequence could inhibit aggregation and membrane interaction of amyloidogenic proteins while retain their antigenicity/immunogenicity.This is helpful for exploitation of the potential of MSP2 as a target of antimalarial drug/vaccine development,and may be reference to designing drugs/vaccines based on other amyloidogenic proteins.