Serum antibodies induced by phagotopes. Two purified phage clones (D1 and H1) were used to immunise BALB/c mice through intraperitoneal administration. For each immunisation, phage (1012 pfu/50 μl) were used, with TBS and wild-type M13 phage as controls. Three mice were immunised with each sample and pre-immune sera were obtained. The mice were bled once (pre-booster), and they were given a booster in the same manner. The immune mice were bled every 7 days after the booster immunisation, and triplicate ELISAs were performed to test each serum sample with urease B as coated protein. All assays were carried out in triplicate and the error bars indicate standard deviation.