血吸虫对吡喹酮抗药性的研究XIV日本血吸虫吡喹酮抗性株和敏感株成虫毛蚴和尾蚴对吡喹酮敏感性比较

Studies on resistance of Schistosoma to praziquantel XIV Experimental comparison of susceptibility to praziquantel between PZQ-resistant isolates and PZQ-susceptible isolates of Schistosoma japonicum in stages of adult worms, miracidia and cercariae

目的测定实验室诱导筛选获得的日本血吸虫吡喹酮抗性株成虫、毛蚴和尾蚴对吡喹酮的敏感性变化,为建立吡喹酮敏感性检测/监测技术提供依据。方法以未暴露于吡喹酮的日本血吸虫江苏实验室传代株和现场采集并经实验室传代的湖南株作为吡喹酮敏感株,以实验室传代并经吡喹酮抗性诱导的日本血吸虫江苏抗性诱导株及现场采集并经实验室吡喹酮抗性诱导的湖南抗性诱导株作为吡喹酮抗性株。分别收集各虫株尾蚴感染小鼠,感染35d后分为6组,5个服药组分别一次性灌服剂量为37.5、75、150、300mg/kg和600mg/kg吡喹酮,对照组不给药;用药后14d解剖小鼠,收集小鼠体内成虫,计算虫负荷和减虫率,计算吡喹酮对各虫株的半数有效剂量(ED50值)。取一定量各虫株尾蚴分别暴露于10-5、5×10-6、10-6、5×10-7mol/L和10-7mol/L吡喹酮溶液中,20、40、60、80min和100min后,在解剖镜下观察尾蚴的断尾变化,计算各虫株尾蚴断尾率。取一定量各虫株毛蚴分别暴露于10-5、5×10-6、10-6、5×10-7mol/L和10-7mol/L吡喹酮溶液中,1、3min和5min后,解剖镜下观察毛蚴的形态变化,计算各虫株毛蚴变形率。结果吡喹酮对江苏吡喹酮敏感株和抗性诱导株的ED50值分别为147.7mg/kg和565.5mg/kg,对湖南吡喹酮敏感株和抗性诱导株的ED50值分别为151.8mg/kg和467.2mg/kg。当暴露于10-5mol/L吡喹酮溶液中20min,江苏吡喹酮敏感株尾蚴断尾率为68.8%,吡喹酮抗性诱导株尾蚴断尾率为38.2%,差异有统计学意义(P<0.01);当暴露于10-7mol/L吡喹酮溶液中100min,江苏吡喹酮敏感株尾蚴断尾率为15.9%,吡喹酮抗性诱导株尾蚴断尾率为6.7%,差异有统计学意义(P<0.01)。当暴露于10-5mol/L吡喹酮溶液中20min,湖南吡喹酮敏感株尾蚴断尾率为59.4%,吡喹酮抗性诱导株尾蚴断尾率为54.6%,差异有统计学意义(P<0.05);当暴露于5×10-7mol/L吡喹酮溶液中40min,湖南吡喹酮敏感株尾蚴断尾率为34.3%,吡喹酮抗性诱导株尾蚴断尾率为18.4%,差异有统计学意义(P<0.01)。当暴露于5×10-7mol/L和10-7mol/L吡喹酮溶液1、3min和5min后,江苏吡喹酮敏感株和湖南吡喹酮敏感株毛蚴的变形率均明显高于吡喹酮抗性诱导株,差异均有统计学意义(P均<0.01)。结论采用亚治疗剂量吡喹酮,在小鼠体内经过诱导筛选所获得的中国大陆日本血吸虫吡喹酮抗性株对吡喹酮敏感性显著低于未经诱导筛选的原代虫株,其抗药性可表现在成虫、毛蚴和尾蚴发育阶段。吡喹酮对成虫的ED50值、尾蚴断尾率和毛蚴变形率作为量化指标,可用于现场日本血吸虫对吡喹酮的敏感性检测/监测。

Objective To investigate the changes of sensitivity to praziquantel （PZQ） about PZQ-resistant isolates of Schistosoma japonicum established in laboratory by means of the resistance-inducement method during the stages of adult worms, cercariae and miracidia, so as to provide the basis for establishing the sensitivity-detecting technique to praziquantel. Methods A Jiangsu laboratory-maintaining isolate and a Hunan field-collecting isolate of S. japonicum that were never treated with PZQ were as PZQ-susceptible isolates, and two PZQ-induced isolates that were established via drug-treated passage in laboratory were as PZQ-resistant isolates. Mice were infected with S. japonicum cercariae collected from above four isolates each. Thirty-five days after the infection, the mice were divided into 6 groups and administered orally with PZQ at dosages of 0, 37.5, 75, 150, 300 mg/kg and 600 mg/kg, respectively. All the mice were sacrificed two weeks after the treatment, and all the adult worms in the hepatic and portomesenteric veins were recovered and counted. The mean worm burden and reductions were calculated and input into Graphpad Prism 5.0 software, and the PZQ ED50 values of four isolates were calculated by the software. The cercariae of above four isolates were exposed to 10^-5, 5×10^-6, 10^-6, 5×10^-7, 10^-7 mol/L PZQ solutions for 20, 40, 60, 80, 100 min and the changes of tail shedding were observed under a dissecting microscope, then the tail shedding rates of cercariae were calculated. The miracidia of above four isolates were exposed to 5×10^-6, 10^-6, 5×10^-7, 10^-7 mol/L PZQ solutions for 1, 3 and 5 min and the morphological changes were observed under a dissecting microscope, then the morphological change rates of miracidia were calculated. Results The PZQ ED50 values of PZQ-susceptible and PZQ-resistant isolates of Jiangsu were 147.7 mg/kg and 565.5 mg/kg, respectively, and the PZQ ED50 values of PZQ-susceptible and PZQ-resistant isolates of Hunan were 151.8 mg/kg and 467.2 mg/kg, respectively. When the cercariae were exposed to 10^-5 mol/L PZQ solution over 20 min, the tail shedding rate of cercariae from PZQ-susceptible isolate of Jiangsu was 68.8%, and the tail shedding rate of cercariae from PZQ-resistant isolate of Jiangsu was 38.2% （P〈0.01）. When the cercariae were exposed to 10^-7 mol/L PZQ solution over 100 min, the tail shedding rate of cercariae from PZQ-susceptible isolate of Jiangsu was 15.9%, and the tail shedding rate of cercariae from PZQ-resistant isolate of Jiangsu was 6.7% （P〈0.01）. When the cercariae were exposed to 10^-5 mol/L PZQ solution over 20 min, the tail shedding rates of cercariae from PZQ-susceptible isolate of Hunan was 59.4%, and the tail shedding rates of cercariae from PZQ-resistant isolate of Hunan was 54.6% （P〈0.05）. When the cercariae were exposed to 5×10^-7 mol/L PZQ solution over 40 min, the tail shedding rates of cercariae from PZQ-susceptible isolate of Jiangsu was 34.3%, and the tail shedding rates of cercariae from PZQ- resistant isolate of Jiangsu was 18.4% （P〈0.01）. When the miracidia were exposed to 5×10^-7 mol/L and 10^-7 mol/L PZQ solutions for 1, 3 and 5 min respectively, the morphological change rates of miracidia from PZQ-susceptible isolates of Jiangsu and Hunan were significantly higher than those of PZQ-resistant isolates （P〈0.01）. Conclusions PZQ-resistant isolates of S. japonicum has been established in mice with sub-curative doses of PZQ by artificial selection in laboratory, and their sensitivities to PZQ are significantly lower than those of the isolates never treated with PZQ. The drug-resistance could exhibit in the stages of adult worms, cercariae and miracidia. The PZQ ED50 value of adult worms, the tail shedding rates of cercariae and the morphological change rates of miracidia as quantitative indicators can be used for monitoring the S. japonicum sensitivity to PZQ.