Hematotoxicity and genotoxicity evaluations in Swiss mice intraperitoneally exposed to Bacillus thuringiensis (var kurstaki) spore crystals genetically modified to express individually Cry1Aa, Cry1Ab, Cry1Ac, or Cry2Aa

Abstract

Bacillus thuringiensis (Bt) has been widely used in foliar sprays as part of integrated pest management strategies against insect pests of agricultural crops. Since the advent of genetically modified plants expressing Bt δ-endotoxins, the bioavailability of Cry proteins has increased, and therefore for biosafety reasons their adverse effects should be studied, mainly for nontarget organisms. We evaluated, in Swiss mice, the hematotoxicity and genotoxicity of the genetically modified strains of Bt spore crystals Cry1Aa, 1Ab, 1Ac, or 2Aa at 27 mg/kg, and Cry1Aa, 1Ab and 2Aa also at 136 and 270 mg/kg, administered with a single intraperitoneal injection 24 h before euthanasia. Controls received filtered water or cyclophosphamide. Blood samples collected by cardiac puncture were used to perform hemogram, and bone marrow was extracted for the micronucleus test. Bt spore crystals presented toxicity for lymphocytes when in higher doses, which varied according to the type of spore crystal studied, besides promoting cytotoxic and genotoxic effects for the erythroid lineage of bone marrow, mainly at highest doses. Although the profile of such adverse side effects can be related to their high level of exposure, which is not commonly found in the environment, results indicated that these Bt spore crystals were not harmless to mice. This suggests that a more specific approach should be taken to increase knowledge about their toxicological properties and to establish the toxicological risks to nontarget organisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 970-978, 2016.

Toxicological Evaluation of a Potential Immunosensitizer for Use as a Mucosal Adjuvant—Bacillus thuringiensis Cry1Ac Spore-Crystals: A Possible Inverse Agonist that Deserves Further Investigation

“…This data suggests that the plasma membrane of erythrocytes could be the primary target for these toxins [ 19 , 27 ], and that Cry toxins are not completely destroyed in the stomach, having their toxic form activated by intestinal alkaline pH. However, some studies have shown that commercial Bt products are safe, and that the mortality observed in tests with mice was verified for extremely high doses and shown to be dependent on the route of administration [ 25 , 28 ], corroborating our previous report [ 20 ].…”

“…Therefore, the applicability of Cry1Ac proteins as potential tools in combating diseases in humans and other mammals further highlights the importance of studies directed to the biosafety of non-target organisms. This is mainly because although Cry toxins have been considered harmless to humans and other vertebrates [ 2 , 18 ], studies by our group have demonstrated that Bt spore-crystals caused hematologic disturbances for the erythroid and lymphoid lineages of Swiss mice [ 19 , 20 , 21 ], indicating that each spore-crystal endotoxin presents a characteristic profile of toxicity and might be investigated individually [ 21 ].…”

Toxicological Examinations Following Oral Administration of Bacillus thuringiensis var kurstaki Biological Insecticide in Wistar Rats

“…A significant decrease in bone marrow cell proliferation presented cytotoxic but not genotoxic impacts. 17 The findings of this study demonstrated that the Cry toxins of B. thuringiensis could induce hematotoxicity in mice. In this study, Cry 10Aa and Cry 1Ba6 significantly decreased the MCV values, while Cry1Ia increased the red cell distribution width above the reference values.…”

In vitro antitumoral activity of soluble protein extracts of Bacillus thuringiensis

“…It is characterized by crystal production during sporulation, containing Cry proteins, encoded by the Cry genes, with a wide division into classes and subclasses according to their insecticide activity, and presently classified according to the percent amino acid identity between Cry protein sequences (Mezzomo et al, 2015 Palma et al, 2014a). Besides the cry proteins, known as -endotoxins, B. thuringiensis isolates can synthesize other toxins, such as -exotoxin, phospholipases, proteases, chitinases and enterotoxins (Berlitz et al, 2012).…”

“…B. thuringiensis spore crystals have shown toxicity for lymphocytes and promoting cytotoxic and genotoxic effects for the erythroid lineage of bone marrow at high concentrations which is not commonly found in the environment, indicated that these B. thuringiensis spore crystals (Mezzomo et al, 2015) were not harmless to mammals (Mezzomo et al, 2015;Okumura et al, 2014).…”