Edwinson Adam, Widmer Giovanni, McEvoy John
Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, ND, USA.
Cummings School of Veterinary Medicine at Tufts University, Division of Infectious Diseases & Global Health, North Grafton, MA, USA.
Int J Parasitol. 2016 Jan;46(1):67-74. doi: 10.1016/j.ijpara.2015.09.001. Epub 2015 Sep 30.
The apicomplexan parasite Cryptosporidium causes cryptosporidiosis, a diarrheal disease that can become chronic and life threatening in immunocompromised and malnourished people. There is no effective drug treatment for those most at risk of severe cryptosporidiosis. The disease pathology is due to a repeated cycle of host cell invasion and parasite replication that amplifies parasite numbers and destroys the intestinal epithelium. This study aimed to better understand the Cryptosporidium replication cycle by identifying molecules that trigger the switch from invasive sporozoite to replicative trophozoite. Our approach was to treat sporozoites of Cryptosporidium parvum and Cryptosporidium hominis, the species causing most human cryptosporidiosis, with various media under axenic conditions and examine the parasites for rounding and nuclear division as markers of trophozoite development and replication, respectively. FBS had a concentration-dependent effect on trophozoite development in both species. Trophozoite development in C. parvum, but not C. hominis, was enhanced when RPMI supplemented with 10% FBS (RPMI-FBS) was conditioned by HCT-8 cells for 3h. The effect of non-conditioned and HCT-8 conditioned RPMI-FBS on trophozoite development was abrogated by proteinase K and sodium metaperiodate pretreatment, indicating a glycoprotein trigger. Cryptosporidium parvum and C. hominis trophozoite development also was triggered by Gal-GalNAc in a concentration-dependent manner. Cryptosporidium parvum replication was greatest following treatments with Gal-GalNAc, followed by conditioned RPMI-FBS and non-conditioned RPMI-FBS (P<0.05). Cryptosporidium hominis replication was significantly less than that in C. parvum for all treatments (P<0.05), and was greatest at the highest tested concentration of Gal-GalNAc (1mM).
顶复门寄生虫隐孢子虫可引发隐孢子虫病，这是一种腹泻疾病，在免疫功能低下和营养不良的人群中可能会发展为慢性疾病并危及生命。对于那些最易患严重隐孢子虫病的人，目前尚无有效的药物治疗方法。该疾病的病理原因是宿主细胞入侵和寄生虫复制的反复循环，这会增加寄生虫数量并破坏肠道上皮。本研究旨在通过识别触发从侵袭性子孢子向增殖性滋养体转变的分子，更好地了解隐孢子虫的复制周期。我们的方法是在无菌条件下，用各种培养基处理引起大多数人类隐孢子虫病的微小隐孢子虫和人隐孢子虫的子孢子，并分别检查寄生虫的变圆和核分裂情况，将其作为滋养体发育和复制的标志。胎牛血清（FBS）对这两种寄生虫的滋养体发育均有浓度依赖性影响。当补充10% FBS的RPMI培养基（RPMI-FBS）经HCT-8细胞预处理3小时后，微小隐孢子虫（而非人隐孢子虫）的滋养体发育得到增强。蛋白酶K和偏高碘酸钠预处理可消除未处理的和经HCT-8预处理的RPMI-FBS对滋养体发育的影响，表明存在一种糖蛋白触发因子。N-乙酰半乳糖胺（Gal-GalNAc）也以浓度依赖性方式触发微小隐孢子虫和人隐孢子虫的滋养体发育。用Gal-GalNAc处理后，微小隐孢子虫的复制最为显著，其次是经预处理的RPMI-FBS和未处理的RPMI-FBS（P<0.05）。在所有处理中，人隐孢子虫的复制均显著低于微小隐孢子虫（P<0.05），且在Gal-GalNAc的最高测试浓度（1mM）下复制最为显著。
