I had never encountered the initialism "FFU" (used in the graph you reproduced), so I looked it up. For anyone else's benefit, it's Focus Forming Units, the equivalent of the plaques I was taught about back in biology school during the dark ages (1980s) for viruses that don't lyse their host cells.
It's not exclusively for viruses that don't have a cytopathic effect (what you're calling lysis here). FFU are used to increase the speed of virus infection assays. Instead of waiting for cytopathic effect, you use some easily-visualized stain that detects active virus replication. Usually, a fluorescent antibody that lights up nicely under a microscope and targets a critical and abundant virus protein. This lets you see little dots of virus replication--foci--and you count the concentration of foci in different wells down a dilution series to be able to determine the FFU concentration of the original sample.
So instead of counting plaques you're counting glowy things, usually.
FWIW, FFU as a concept was basically only emerging when I was in grad school. The only reason I didn't go into detail in today's issue was brevity and relevance. But I'm happy to elaborate on it :)
Thanks, as always.
I had never encountered the initialism "FFU" (used in the graph you reproduced), so I looked it up. For anyone else's benefit, it's Focus Forming Units, the equivalent of the plaques I was taught about back in biology school during the dark ages (1980s) for viruses that don't lyse their host cells.
It's not exclusively for viruses that don't have a cytopathic effect (what you're calling lysis here). FFU are used to increase the speed of virus infection assays. Instead of waiting for cytopathic effect, you use some easily-visualized stain that detects active virus replication. Usually, a fluorescent antibody that lights up nicely under a microscope and targets a critical and abundant virus protein. This lets you see little dots of virus replication--foci--and you count the concentration of foci in different wells down a dilution series to be able to determine the FFU concentration of the original sample.
So instead of counting plaques you're counting glowy things, usually.
Remember, I learned biology before the invention of writing.
OK, that's just hyperbole, but I did learn before you could just order fluorescent monoclonal antibodies.
FWIW, FFU as a concept was basically only emerging when I was in grad school. The only reason I didn't go into detail in today's issue was brevity and relevance. But I'm happy to elaborate on it :)