Experimental observation of the effects of reinfection with Plasmodium berghei ANKA on formation of immune memory

Objective To investigate the effects of malaria reinfection on formation of immune memory.Methods DBA/2 mice were infected with Plasmodium berghei ANKA-parasitized erythrocytes and radically treated with chloroquine plus artesunate on day 3 after infection.Then the mice were reinfected with P.berghei ANKA on day 90 after primary infection.The level of parasitemia during primary and secondary infections was observed by means of the Giemsa staining of thin blood smears,and flow cytometry was used to quantitatively analyze the percentage of memory T cells and memory B cells in the spleen cell population on days 0,1,3,and 5 post-reinfection.Results Parasitemia in mice post-reinfection was transient and extremely mild,although the percentage of memory T cells and memory B cells in the spleen cell population from the mice began to increase on day 1 and day 3 post-reinfection,respectively.Both began to decline to a degree on day 5 post-reinfection.Moreover,the percentage of memory T cells and memory B cells in pre-reinfection mice was slightly higher than that in control(noninfected) mice.Conclusion Malaria reinfection can promote the generation of immune memory,but high levels of immune memory are not sustained.