Western blot analysis of the immunoreactivity of native and recombinant proFhCatB. Sera from rats immunized with proFhCatB were tested for activity on a Western blot using FhCatB expressed in different systems. Lanes 1 and 2, supernatants of COS7 cells transfected with pVR1012 vector alone and pVRCatB, respectively; lanes 3 and 4, ES material from F. hepatica juveniles and adults, respectively; lane 5, recombinant proFhCatB. Samples were separated by SDS-PAGE (12%) under nonreducing conditions and then transferred to nitrocellulose. STD, standard molecular size marker.