Influence of anti-malarial therapy on the acquirement protective immunity in mice infected in vitro malaria parasite

In order to investigate the influence of anti-malarial therapy on the protective immunity in mice infected with malaria parasites, BALB/c mice infected intra-peritoneal with erythrocytes parasitized with Plasmodium yoelii 17XNL(non-lethal strain) were treated with different dose of Chloroquine or Artesunate Thirty days after infection during which the parasites inoculated were cleansed up in the spontaneously cured group, mice of different groups were re-infected with P.yoelli 17XNL, P.yoelii 17XL (lethal strain) or P.berghei ANKA (heterologous strain). The level of parasitemia in mice during primary and challenged infections was observed by mean of the Giemsa staining of thin blood smears, and the levels of IFN-γ in the supernatants of cultured splenic cells and the specific antibody levels in serum were determined by ELISA. It was demonstrated that high levels of IFN-γ production were obvious during early stage of primary infection both in the spontaneously cured and various treated groups of mice, and then levels of the specific IgG antibodies against P.yoelii(non-lethal strain) increased remarkablly without significant difference among different groups. A complete resistance to the challenges with P.yoelli(non-lethal and lethal strains) could be demonstrated,but few of the re-infected mice showed low level of temporal parasitemia. However, the infected mice challenged with the heterologous strain of plasmodia were died completely. Taken together, it is evident that treatment of mice infected with palsmodia by Chloroquine or Artesunate shows no any effect on the acquirement of anti-malarial immunity and the maintenance of immuno-memory obtained and the specific IgG antibodies are the main immune effector molecules of host to resist re-infection.