hello,

if you use 96-wells plates, you can use the Spearman & Kärber algorithm (ready to use excel added. be carefull not to change the wrong parameter). Any well with GFP signal is counted as 1, even if not all cells are GFP+.

Another way is to use 6-wells plates, with a short infection time in 1mL (in serial dilution) and then use methylcellulose or agarose coating (to avoid virus diffusion via the culture medium) for X days before counting.

There you count the number of green spots (or lysis spots if your virus is aggressive enough) and you report with the dilution you used. For example, if you have 8 zones of infected cells in your 10^-6 dilution well, then you have a rought concentration of 8.10^6 infectious virus per mL in your production.

Use of duplicate is strongly advised.