Blastocystis hominis: evidence for caspase-3-like activity in cells undergoing programmed cell death

We have shown previously that the human intestinal protozoan, Blastocystis hominis, undergoes apoptosis-like programmed cell death (PCD) when exposed to a cytotoxic monoclonal antibody (mAb), 1D5. In the present study, ELISA and immunoblot assays employing chicken anti-CPP32 antibody suggest that ca spase-3-like antigens exist in B. hominis. Using colorimetric and flow cyto metric assays for caspase-3 activity, we also observed an increase in activ ity between 1 h and 6 h after exposure to mAb 1D5, with greatest activity a t 6 h. These findings suggest that caspase-3-like proteases play an importa nt role in B. hominis undergoing PCD, similar to the phenomenon in higher e ukaryotic organisms.