Thanx for that; I have had experiences with rabies virus and BHK-21 cells when the virus adpated for growth in the same cell line would give only low yields sometimes (the passage numbers of the cells I had were well over 100). This is when I was preparing virus stock for my experiments. The cells would grow well at high passage numbers, though.
At other times, I have seen similar issues with herpesvirus 1 in vero cells, when the vero cells would not take infection at all, beyond passage numbers 130 or so.
The issue is, the cells grow well at the high passage numbers, but do not seem to get infected much.
These were the experiences with culture-adapted viruses; and I was wondering whether it would be the same situation if I use a highly passaged cell line for virus isolation from clinical specimens. (Say, for arboviruses, rotaviruses etc.)