Abstract
In this paper some criteria for the plaque assay of eel virus European (EVE) and infectious hematopoietic necrosis virus (IHNV) in loosely confluent RTG-2 cell monolayers were evaluated.
1. Suitable virus adsorption times for both EVE and IHNV were 60 min.
2. The linear relationship between the number of plaques and the concentration of virus was shown in both EVE and IHNV-RTG-2 cell systems. This indicated that a single infectious viral particle of EVE or IHNV is sufficient to infect a RTG-2 cell.
3. The coefficient of variation of the distribution of plaque numbers was 0.06 in the EVE-RTG-2 cell system and 0.054 in the IHNV-RTG-2 cell system.
4. The number of plaques increased as the volume of viral inoculum increased, but the efficiency of adsorp tion decreased with inocula volumes greater than 0.1 ml.
5. Neither the concentration of agar in agar overlay medium (AOM) nor the incubation periods significantly affected the number of plaques (EVE : 0.5<P, 0.5<P; IHNV : 0.25<P, 0.5<P, respectively). However there was a significant effect of both concentration of agar in AOM and incubation period on the diameter of plaques (EVE : P<0.05, P<0.005 ; IHNV : p<0.005, P<0.01, respectively).
These results indicated that loosely confluent RTG-2 cell monolayers gave precise quantitative analysis for EVE and IHNV.
