Evaluation Of Humanized Monoclonal Antibody HP6H8 Against Plasmodium Falciparum In HuRBCs-NOD/SCID Mice

Malaria is one of the major infectious diseases around the world,accounting for hundreds of thousands of deaths each year.The vast majority of deaths are due to P.falciparum malaria.Pregnant women and children are the main susceptible populations.The emergence of drug-resistant parasites is one of the main barriers to malaria elimination,especially for chemical drug.Meanwhile,the severe adverse effect of chemical drugs makes it hard for pregnant women and infants to get proper treatment.Antibody drugs are a new strategy for antimalarial treatment.The discovery of ligand-receptor relationships between parasites and its hosts provides an opportunity for it.The choice of antimalarial efficacy evaluation models is greatly restricted by the parasite species specificity.In small animal models,P.falciparum-infected Hu RBCs engrafting SCID mouse models are good tools to evaluate antimalarial drug efficacy in vivo.These tools are been widely approved and developed.It proved that Humanized monoclonal antibody HP6H8 targeting receptor protein CD147 made significant inhibitory effect for various strains of the parasites in vitro.(This part was performed by Dr.Zhang Meng-yao).We suspected whether this antibody could achieve the same antimalarial efficacy in vivo.This study aimed to evaluate the antimalarial efficacy of humanized monoclonal antibody HP6H8 in P.falciparum-infected Hu RBCs engrafting NOD/SCID mice.The study was composed of two parts:Part 1: the Construction of P.falciparum-infected Hu RBCs-NOD/SCID mouse modelWe intraperitoneally injected immune-suppressor to inhibit congenital immune response caused by macrophagocyte and inflammatory response caused by exogenous materials.We established humanized NOD/SCID mouse model based on repeated intravenous delivery of Hu RBCs.We detected Hu RBCs engrafting rate in humanized NOD/SCID mice by flow-cytometry technology and removed the mice at low engrafting rate.Then we intravenously infected Hu RBCs engrafting mice with P.falciparum-infected Hu RBCs.It was only a single infection.After infection,we observed parasite survival by daily Giemsa stained thin blood films drawn from the tail vein.The results showed that the Hu RBCs engrafting rates could reach above 80%.Initial parasitaemia in mice was approximately 0.1%.The parasites had complete erythrocytic stage life cycle and could proliferate normally.These results demonstrated that we successfully established P.falciparum-infected Hu RBCs-NOD/SCID mouse model.Part 2: Antimalarial therapeutic efficacy of HP6H8 in vivoWe used P.falciparum-infected Hu RBCs-NOD/SCID mouse model to evaluate the antimalarial efficacy of humanized monoclonal antibody HP6H8 in vivo.Before dosing,we randomly assigned mice according to the engrafting rate of Hu RBCs,parasitaemia.Then we administrated HP6H8 by intravenous route for one shot.Following infection,we observed parasite survival in peripheral blood on thin blood smears.Statistical results showed that the 50% effective doses(ED50)of HP6H8 were 0.948mg/kg.A dose of 2mg/kg could completely eliminate parasites in peripheral blood.In conclusion,we established a P.falciparum-infected Hu RBCs-NOD/SCID mouse model.We evaluated antimalarial efficacy of humanized monoclonal antibody HP6H8 in this model.More importantly,the antibody HP6H8 developed by our lab has significantly antimalarial efficacy in vitro and in vivo.The efficacy data we achieved in this study have important significance for further preclinical studies of the antibody.