Proteins for western blot were extracted either from Trizol samples according to the manufacturer's instructions, or from virally infected tadpoles homogenised in 10 mM Tris with 100 mL sterile 1.0 mm zirconia silicone beads (BioSpec Products). The tadpole was homogenised in a mini-beadbeater (BioSpec Products) for 30 sec, centrifuged at 13,0006 g for 30 sec then homogenised in a minibeadbeater for a further 30 sec. SDS was added to a final concentration of 5% and the homogenate heated to 100uC for 1 min. After 30 min at RT to allow SDS to penetrate the sample, the homogenate was centrifuged, the supernatant decanted, heated to 100uC for 1 min and stored at 280uC until used. To extract globin from RBCs, blood was processed as previously described (see Infection and sampling) and the protein content of each sample was determined 