Analysis of adult globin profiles was carried out on RBCs from tadpoles taken at stage 42 and metamorphs at 1-2 weeks post tail resorption, by which time the switch has been made from tadpole to adult globin production. Blood from tadpoles given all three doses of the test virus (rBIV/neo r /Adglob that does express adult globin) and the control virus (rBIV/neo r that does not express adult globin) were analysed by polyacrylamide gel electrophoresis (PAGE) and silver staining (Fig. 6a) . The protein profiles of blood from animals infected with the rBIV/neo r control (n = 51) and rBIV/neo r /Adglob (n = 89) viruses were all similar. A western blot using rabbit anti toad adult globin confirmed that the main 14 kDa band detected by silver stain was adult globin (Fig. 6b) . We were thus unable to detect any change in the adult globin profile in RBCs taken from the animals that had been exposed to adult globin as tadpoles.