Plasmodial Proteins Expressed on The Surface of Infected Hepatocytes

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We established the small scale method of primary hepatocyte culture, in order to increase the efficiency of in vitro infection of sporozoites. The abdominal cavity and thorax and salivary glands of the mosquitoes were separated each other, and then the infected numbers of sporozoites were counted every other day after blood meal. The number of sporozoites obtained from the abdominal cavity were maximal 12 days after blood meal. The number of sporozoites obtained from the thorax and salivary gland were maximal 18 days after blood meal. The sporozoites obtained 14 to 16 days after blood meal were infectious to mice. To look for the better experimental conditions for obtaining a lot of sporozoites, we used DBA/1 and C5-deficient DBA/2 mice for the experimental host to determine the effects of complement on the infectivity of malaria parasites to mosquitoes. The infectivity of oocysts to Anopheles stephensi fed on DBA/1 mice was significantly less than those fed on DBA/2 mice. Heat inactivated DBA/1 sera injected into DBA/2 mice did not reduce the infectivity of oocysts. By comparison to these controls, fresh DBA/1 sera injected into DBA/2 mice significantly reduced the infectivity. Moreover, male DBA/2 mouse sera restored with human C5 significantly reduced the infectivity. In contrast to the reduction of infectivity, the numbers of infected mosquitoes were not reduced. In conclusion, the alternative pathway of complement in the mouse serum significantly reduced, but did not eliminate, the infectivity of Plasmodium yoelii to A.stephensi. The reduction of the infectivity is mainly due to the inability of the zygote to transform into the ookinete in the mosquito midgut. And DBA/2 mouse seems to be a suitable mouse strain to obtain a lot of sporozoites for in vitro infection.