Selective cytotoxic activity against leukemic cell lines from mosquitocidal Bacillus thuringiensis parasporal inclusions.

The discovery of parasporin has triggered an interest in examining various Bacillus thuringiensis (Bt) isolates for specific anti-cancer activity. The aim of this study was to determine the potency and specificity of parasporal inclusions from Malaysian mosquitocidal Bt isolates against a leukemic cell line (CEM-SS). The Bt isolates used in this study were identified as having weak to potent larvicidal activity against Aedes aegypti and varying hemolytic activity. The 12 mosquitocidal Bt isolates examined in this study showed low to moderate cytotoxicity when tested against CEM-SS and HeLa. Interestingly the parasporal inclusions of Bt 18 (non-hemolytic isolate), showed therapeutic potential demonstrating specificity for CEM-SS compared to HeLa, whilst being non-cytotoxic to normal T lymphocytes. The mode of cell death by Bt 18 was shown to be initially apoptotic. SDS-PAGE analysis and N-terminal sequencing of the upper and lower bands of Bt 18 showed similarity between Bt 18 parasporal inclusions with Cry 24Aa and 25Aa of Bacillus thuringiensis subsp jegathesan and Cry 15Aa of Bacillus thuringiensis subsp israelensis. Although the BLAST analysis did not show sequence similarity between Bt 18 and Parasporin, we propose that the Bt 18 parasporal inclusions share similar characteristics to Parasporin since Bt 18 is not hemolytic but discriminately cytotoxic towards leukemic cell lines.

Malaysian mosquitocidal soil bacterium (Bacillus thuringiensis) strains with selective hemolytic and lectin activity against human and rat erythrocytes.

The objective of this study is to determine the role of carbohydrates on the toxic effect of parasporal inclusion proteins isolated from Malaysian mosquitocidal Bacillus thuringiensis (Bt) strains on erythrocytes (human and rat). Dose response analyses on the effect of these parasporal inclusions on human and rat erythrocytes suggest that toxin action is selective depending on bacterial strains and source of erythrocytes. Results from this study suggest Bt toxin is a lectin which recognizes specific plasma membrane glycoconjugate receptor(s) with a terminal residue of either D-mannose (Man), N-acetyl-D-galactosamine (GalNAc), N-acetyl-D-glucosamine (GlcNAc) or even a combination of these monosaccharides.