Interference of GFP and scFv incorporation in the capsid of GFP/α-CEA-λ with phage infectivity. Lambda double displaying phage GFP/α-CEA-λ and wild type λKM4 were assayed by using anti-gpV antibody-coated ELISA plate and polyclonal anti-λ rabbit antibodies to reveal the bound phages. The amounts of phage measured as PFUs used per well of ELISA plate, are indicated on the abscissa. Results are expressed as A=A450-A620. Data reported are the average values of assays performed in duplicate. Error bars represent the standard deviation of the mean.