ELISA reactivity of lambda phage displaying GFP or AP and anti-CEA scFv antibody against CEA. Lambda phage clones, displaying GFP or alternatively AP as a fusion to the C-terminus of the gpD and anti-CEA scFv antibody as a fusion to the truncated gpV, were tested by ELISA against purified CEA and an irrelevant control protein (GST). Anti-lambda polyclonal rabbit serum was used for detection of the bound phage. Wild type λKM4 was included as a negative control. The phage samples were stored at 4°C for (*) 55-months, (#) 23-months or ($) 9-months. Irrelevant GST protein is included as a negative control. 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.