Comparison of the response of midgut epithelial cells and cell lines from lepidopteran larvae to CryIA toxins from Bacillus thuringiensis

Abstract The cytotoxic responses of midgut epithelial cells (MEC) from spruce budworm (SBW), gypsy moth (GM) and silkworm (SW) larvae were compared with the cytotoxic response of lepidopteran cell lines (SF-9, SE-1a, and CF-1) to CryIA toxins from Bacillus thuringiensis . The MEC from SBW, SW and GM had binding proteins for CryIA a,b,c toxins, whereas the lepidopteran cell lines had binding proteins for CryIA c . Single MEC exposed to CryIA a,b,c toxins in a qualitative lawn assay were equally susceptible to the toxins with a threshold response at about 1 ng. The cell lines were not susceptible to CryIA a,b toxins in the dose range tested, but had threshold responses for CryIA c of 3.4 ng for SF-9, 50.2 ng for SE-1a and 5.9 ng for CF-1. In the quantitative Live/Dead assay, MEC were equally susceptible to CryIA a,b,c toxins with a threshold effect at about 1 ng and a maximum effect at about 10 ng. CF-1 was most sensitive to CryIA c with a threshold effect at 0.39 ng and a maximal effect at about 1 ng. In contrast, a 25–50 times greater dose of CryIA a or CryIA b was required to elicit a similar response as CryIA c for CF-1. SF-9 and SE-1a were most susceptible to CryIA c with a threshold effect observed at about 0.5 ng and maximal effects at about 2 ng. SF-9 cells have a threshold and maximum response to CryIA a,b of about 10 ng and 20 ng, respectively. SE-1a cells have a threshold and maximal response to CryIA a,b of 5 ng and 10 ng, respectively. Intact midgut epithelium exposed to CryIA a,b,c toxins had a threshold dose of 2 ng for CryIA b , 10–30 ng for CryIA a and 2–30 ng for CryIA c . This study has shown that MEC are affected by a broader spectrum of toxins compared to the lepidopteran larvae and insect cell lines.