Immunoblotting with wild type and mutant P0 (N-P0) protein. Full length P0 (lanes 1, 3, 5, 7 and 9) or mutant P0 (lanes 2, 4, 6, 8 and 10) were immunoblotted with sera containing anti-P0P1P2 (lanes 1–8) or anti-P0P1 (lanes 9 and 10). Anti-P0P1P2–reactive sera reacted only with P0 (lanes 1, 3 and 5); anti-P0P1-reactive serum reacted with both P0 and N-P0 (lanes 9 and 10).