Effect of early radical treatment of primary infection with Plasmodium berghei ANKA on the cellular immune response to homologous reinfection

Objective To investigate the effect of early radical treatment of primary Plasmodium infection on the cellular immune response to homologous reinfection.Methods DBA/2 mice were infected by intraperitoneal injection of 1×106 P.berghei ANKA parasitized erythrocytes.The mice were then radically treated with chloroquine plus artesunate at day-3 after infection.After primary infection,the mice were reinfected with P.berghei ANKA at day-90.The level of parasitemia during primary and secondary infections was determined by the Giemsa staining of thin blood smears.Flow cytometric method was used to quantitively analyze the percentage of activated T cells in spleen at day-0,1,3 and 5 post-reinfection.The levels of IFN-γ,TNF-α,IL-4 and IL-10 in the spleen cell culture supernatant were measured by ELISA.Results Parasitemia in radically treated mice was transient and extremely low.And the percentage of activated T cells was steadily increased from day-1 to day-5 after reinfection.The levels of IFN-γ was significantly increased at day-1 post-reinfection and reached the peak at day-3 post-reinfection.Similarly,TNF-α and IL-10 were also significantly increased.IL-4 was significantly increased at day-5 post-reinfection.Conclusion Early radical treatment of primary Plasmodium infection has little effect on the cellular immune response to homologous reinfection.CD4+ Th1 response may also be a key factor involved in protective immunity against homologous reinfection.