Fasciola gigantica: Production and characterization of a monoclonal antibody against recombinant cathepsin B3

► Clone 2F9 had the highest titer from six stable clones of MoAb (1C4, 1E9, 2E5, 2F9, 5B4, 5D7). All MoAbs were found to be IgG1 and λ light chain, and exhibited specific binding to the rFgCatB3 band. ► The immunoblotting experiment: all MoAbs reacted with two bands of rFgCatB3 which have MW of 37 kDa and 55-75 kDa. These MoAbs reacted with native CatB3 which appeared as a single band at MW 37 kDa in WB extract of metacercariae and NEJ, but no positive band was detected in TA, ES, and WB extracts of 4-week-old juvenile or of adult parasites. When similar antigenic fractions were analyzed with PoAbs against native CatB3, the positive band was only observed at MW 37 kDa in WB extracts of metacercariae as well as at MW 37 kDa and 34 kDa in those of NEJ which confirmed that the proteins detected by MoAb were CatB3. ► Immunolocalization: in metacercariae, specific immunostaining was observed in both caecal epithelium and in the lumen of the caecum, while the tegument and parenchymal cells were not stained. In NEJ, the intense immunostaining was also observed in the both caecal epithelium and in the lumen of the caecum, while the tegument, muscle and parenchymal cells were not stained. Consistent with the immunoblotting analysis, there was no immunostaining in 4-week-old juvenile and adult parasite tissues. The negative control sections of the parasite tissues stained with myeloma culture fluid, showed no reddish staining in any of the parasite tissues. ► The cross-reactivity study in immunoblotting, no positive band was detected in WB antigens from four other trematode parasites (G. explanatum, E. pancreaticum, P. cervi, S. spindale and S. mansoni) and from two nematode parasites (Haemonchus placei and Setaria labiato-papillosa), while the band was very prominent in WB of F. gigantica NEJ. ► It is possible that this MoAb could be used for immunodiagnosis for fasciolosis which are now being studied.