目的 通过体外阻断实验与蚊虫直接喂养实验对截短的重组伯氏疟原虫推测分泌动合子蛋白7（rPbPSOP7）31~210氨基酸（aa）片段的传播阻断能力进行研究。方法 体外阻断实验,雌性BALB/c小鼠经腹腔注射5 × 10⁶伯氏疟原虫感染红细胞（PbRBC）,感染后第3天,尾静脉收集血液,与rPbPSOP7免疫小鼠血清（大肠埃希菌表达并纯化,与弗氏佐剂混合后免疫BALB/c小鼠）进行混合培养,观察不同稀释倍数（1 : 5、1 : 10、1 : 50）免疫血清培养15 min后疟原虫配子体出丝数及培养24 h后动合子形成数的变化,以同样稀释倍数的His标签蛋白免疫血清为对照。蚊虫直接喂养实验,rPbPSOP7（实验组）或His标签蛋白（对照组）与弗氏佐剂混合后各免疫5只雌性BALB/c小鼠,于末次免疫后第10天,用苯肼处理并经腹腔注射5 × 10⁶ PbRBC,感染后第3天,每组小鼠用至少50只雌性按蚊直接吸食小鼠血液,吸血后第10天解剖按蚊,计数蚊胃壁上的囊合子数,计算蚊虫感染率。实验重复3次。结果 体外阻断实验中,与His标签蛋白免疫血清对照组相比,rPbPSOP7免疫血清1 : 5、1 : 10和1 : 50稀释培养的配子体出丝数分别减少了22.0%、8.0%和2.0%,差异无统计学意义（P > 0.05）;与对照组相比,培养24 h后,1 : 5、1 : 10与1 : 50稀释培养的动合子形成数分别减少了69.2%、56.4%和48.6%（P < 0.01）,呈抗体剂量依赖关系。3次独立的蚊虫直接喂养实验结果显示,实验组每只蚊胃壁上的平均囊合子数分别为（31.1 ± 34.9）、（30.2 ± 32.3）和（29.1 ± 35.1）个,较对照组的（87.1 ± 69.3）、（96.4 ± 82.9）和（85.3 ± 69.1）个分别减少了64.2%、68.6%和65.8%（P < 0.01）。按蚊感染率由对照组的96.4%（27/28）、89.3%（25/28）和89.3%（25/28）,降至实验组的78.6%（22/28）、78.6%（22/28）和75%（21/28）,分别降低了17.8%、10.7%与14.3%（P > 0.05）。结论 rPbPSOP7免疫血清可明显减少动合子及囊合子的形成,抗rPbPSOP7血清具有一定的传播阻断能力。

Objective To investigate the truncated Plasmodium berghei putative secreted ookinete protein 7 (PbPSOP7) induces transmission-blocking immunity determined by in vitro antibody blocking and mosquito feeding assays. Methods Recombinant PbPSOP7 protein (rPbPSOP7) was expressed in E. coli and the anti-rPbPSOP7 sera were obtained by immunizing BALB/c mice for three times with rPbPSOP7 formulated with Freund’s adjuvant. For in vitro test, P. berghei-infected mouse blood was obtained from a mouse infected with 5 × 10⁶ P. berghei for three days, then co-incubated with mouse anti-rPbPSOP7 sera at 1 : 5, 1 : 10 and 1 : 50 dilutions. Mouse anti- a non-relevant His-tag protein serum at the same dilutions was used as control. The inhibition on the exflagellation of Plasmodium gametocytes was observed 15 min after the culture and the inhibition on the ookinete development was observed 24 hours after incubation. For mosquito feeding experiment, 5 mice were each immunized with 50 μg of rPbPSOP7 formulated with Freund’s adjuvant for three times, then infected with 5 × 10⁶ P. berghei by intraperitoneal injection 10 days after the last immunization. Three days post-infection, the mice were fed by at least 50 female anopheles mosquitoes. The mosquitoes were dissected 10 days after the blood feeding, the infection rate and the reduced number of oocysts in each infected mosquito were calculated compared with mosquitoes fed with mice immunized with His-tag control protein. The feeding experiment was repeated three times. Results When incubated with mouse anti-rPbPSOP7 sera at the 1 : 5, 1 : 10 or 1 : 50 dilutions for 15 min, the exflagellation of gametocytes was decreased by 22.0%, 8.0% and 2.0% compared to Plasmodium incubated with sera from mice immunized with His-tag protein(P > 0.05). After incubated with mouse anti-rPbPSOP7 sera for 24 hours, the significant inhibition of ookinete development was observed in the culture with different dilutions of the antisera. The development of ookinete was reduced by 69.2%, 56.4% and 48.6% when incubated with anti-rPbPSOP7 sera at 1 : 5, 1 : 10 and 1 : 50 dilutions, respectively, compared with control sera group (P < 0.01). Three independent mosquito feeding experiments showed that, compared with the control group, the development of oocysts in the midgut of mosquitoes in immunized group was significantly decreased from 87.1 ± 69.3, 96.4 ± 82.9 and 85.3 ± 69.1 to 31.1 ± 34.9, 30.2 ± 32.3 and 29.1 ± 35.1, respectively. Anti-rPbPSOP7 sera reduced the development of oocyst by 64.2%, 68.6% and 65.8% in three independent feeding experiments (P < 0.01). The infection rates of P. berghei in mosquitoes decreased from 96.4% (27/28), 89.3% (25/28) and 89.3% (25/28) to 78.6% (22/28), 78.6% (22/28) and 75.0% (21/28) in three experiments, with 17.8%, 10.7% and 14.3% reduction (P > 0.05). Conclusion Immunization of rPbPSOP7 induced transmission-blocking immunity characterized by reduced development of P. berghei ookinate and oocyst in mosquitoes, indicating that PbPSOP7 is a potential malaria transmission-blocking vaccine candidate.