关键词: 　Ficolin-A, 伯氏疟原虫, 裂殖子表面蛋白1羧基端Mr 19 000片段

Abstract:  【Abstract】 Objective  To evaluate the effect of Ficolin-A, a lectin complement against Plasmodium berghei in mice model.  Methods  The Mr 19 000 fragment of merozoite surface protein-1 of P. berghei（MSP119） was cloned and then subcloned into the vector pGEX-KG. The recombinants of pGEX-KG-Ficolin-A and pGEX-KG-MSP119 were transformed into Escherichia coli BL21, and followed by expression of the protein induced by 1 mmol/L IPTG. The fusion protein was purified by affinity chromatography using Glutathione Sepharose 4B, and then identified by SDS-PAGE and Western-blotting. Five mouse model groups were treated with PBS, GST, Ficolin-A, MSP119, or Ficolin-A+MSP119, respectively. Each group had eight mice. Mice in Ficolin-A or MSP119 groups were injected with 20 μg Ficolin-A or MSP119 protein each time, respectively. Mice in Ficolin-A+MSP119 group were injected with 20 μg Ficolin-A and 20 μg MSP119 each time. Mice in control groups were injected with 200 μl PBS or 20 μg GST, respectively. All the mice received four immunizations at 2-week intervals. Two weeks after the last immunization, all the mice were inoculated with 300 μl Plasmodium berghei-infected red blood cells. On day 2, 4, 6, 8, and 10 post-infection, blood samples were collected from three mice of each group, and the Giemsa stained-blood films were microscopically examined. Density of malaria parasites was calculated. The survival rate was evaluated on day 20 post-infection.  Results  The recombinant vectors of pGEX-KG-Ficolin-A and pGEX-KG-MSP119 were constructed. Purified fusion proteins, Ficolin-A-GST and MSP119-GST, were obtained. Western blotting analysis indicated that the relative molecular mass of fusion proteins Ficolin-A-GST and MSP119-GST was about Mr 69 000 and Mr 41 000. Animal experiments showed that on day 10 after infection, the parasite density in Ficolin-A+MSP119 group ［（22.2±1.7）%］ was slightly lower than that of the groups MSP119 ［（33.4±2.7）%］, Ficolin-A [（36.2±3.1）%］, GST ［（43.8±4.8）%］ and PBS [（45.3±3.6）%], but the difference was not statistically significant（P>0.05）. No mouse survived in PBS group on day 20 after infection. There was no significant difference in number of survival mice between Ficolin-A group (3 mice) and GST group  (2 mice). Six mice survived in Ficolin-A+MSP119 group, which was significantly more than that of GST group （P<0.05）.  Conclusion  Ficolin-A cannot significantly suppress parasite density. However， Ficolin-A+MSP119 can increase the survival rate of Plasmodium berghei-infected mice.

Key words: Ficolin-A, Plasmodium berghei, MSP119