Abstract
Infectious hematopoietic necrosis virus (IHNV) is well known fish pathogen on salmonid fishes in an aquaculture. In present moment, however, the effective chemotherapy on IHNV infection was not reported so far. We described here the search for new therapeutic agents IHNV infection in vitro and in vivo.
Firstly, we examined mainly nucleoside analogues as potential virostatic agent using our developed, very simple and quantitative method (namely, CPE spot reduction method) on CHSE-214 cell monolayer. This method could be successfully applied to our screening purpose and gave good results which were comparable to usual plaque reduction method.
Among the twenty four compounds tested in vitro, we selected eleven effective compounds against IHNV which showed the 50% inhibition of CPE spot within 10 μg/ml and were not observed the cytotoxicity within 10 μg/ml. In this report, we used five compounds such as 9-β-D-ribofuranosyl-6-mercaptopurine (6-thioinosine, 6-TI), 1-β-D-ribofuranosyl-5-hydroxyuracil (5-OHUrd), 1-β-D-ribofuranosyl-1, 2, 4-triazole-3-carboxamide (Virazole), 9-[S]-(2, 3-dihydroxypropyl)adenine ([S]-DHPA) and 7-chloro-4(4-diethylamino-1-methyl-butylamino)-quinoline (Chloroquine).
Then we extended our experiment to in vivo for further evaluation against experimentally IHNV infected steelhead trout (Salmo gairdnerii) fry by the immersion method. Life span was increased in treated groups, especially in the case of 6-TI and 5-OHUrd treated groups when compared with virus control group. Difference of the effect of compound was observed between the daily treatment and a day interval treatment of 5-OHUrd, but was not shown in the case of 6-TI.
Additionally we examined the effects of selected compounds on normal cell growth and viral RNA synthesis. Some of the mode of action of compounds will be discussed.
