Miller R L, Wang A L, Wang C C
University of California San Francisco, School of Pharmacy, Department of Pharmaceutical Chemistry 94143.
Mol Biochem Parasitol. 1988 Apr;28(3):189-95. doi: 10.1016/0166-6851(88)90003-5.
The dsRNA virus which infects some strains of Giardia lamblia has been purified and characterized with respect to its effect on growth of the parasite. Extensive purification of the virus from G. lamblia growth medium was accomplished by Millipore filtration and two successive CsCl gradient centrifugations. The purified virus possessed a single major protein species of 100,000 molecular weight. Effects of the extensively purified virus on growth of the virus-free parasite were studied. A cloned WB strain, sensitive to the viral infection, and a cloned E-9/M strain, resistant to the infection, were studied. With the WB strain, infection can occur at a ratio as low as 10 viral particles per organism. As the virus to parasite ratio increased, the rate of growth of the parasite decreased and the percentage of parasites not adhering to the culture tube wall also increased. These nonadhering cells, which differed from the nonadhering cells under normal growth conditions, were unable to divide. They contained an average number of 500,000 viral particles per cell which may be the threshold intracellular density of viral particles arresting the growth of G. lamblia. The results also suggest that the specific consequence of viral infection, even at extremely high multiplicity of infection, is not lysis of G. lamblia trophozoites but cessation of growth.
一种感染某些蓝氏贾第鞭毛虫菌株的双链RNA病毒已被纯化，并就其对寄生虫生长的影响进行了表征。通过密理博过滤和两次连续的CsCl梯度离心，从蓝氏贾第鞭毛虫生长培养基中对该病毒进行了广泛纯化。纯化后的病毒具有一种分子量为100,000的主要蛋白质。研究了广泛纯化的病毒对无病毒寄生虫生长的影响。研究了对病毒感染敏感的克隆WB菌株和对感染有抗性的克隆E-9/M菌株。对于WB菌株，每生物体低至10个病毒粒子的比例即可发生感染。随着病毒与寄生虫比例的增加，寄生虫的生长速率下降，不附着于培养管壁的寄生虫百分比也增加。这些不附着的细胞与正常生长条件下的不附着细胞不同，无法分裂。它们每个细胞平均含有500,000个病毒粒子，这可能是阻止蓝氏贾第鞭毛虫生长的病毒粒子的细胞内阈值密度。结果还表明，即使在极高的感染复数下，病毒感染的特定后果也不是蓝氏贾第鞭毛虫滋养体的裂解，而是生长停止。
