Risk assessment and fitness of a transgenic entomopathogenic nematode

A strain of the entomopathogenic nematode, Heterorhabditis bacteriophora, was transformed by the addition of a heat-shock protein gene (hsp70A) from the free-living nematode Caenorhabditis elegans. Laboratory experiments with wild-type and transgenic nematodes were done at 16, 25, 30, and 37°C to investigate infectivity, reproductive capacity, and survival in water. Heat-shocked transgenic nematodes (ones subjected to a heat shock that is lethal to wild-type nematodes) were included in experiments to determine if this treatment caused sublethal damage. We found no significant differences in the ability of wildtype, transgenic, and heat-shocked-transgenic nematodes to infect or to reproduce in last-instar Galleria mellonella larvae or to survive at these temperatures. We compared the ability of wild-type and transgenic nematodes to infect and kill 11 species of invertebrates, representing groups known to be susceptible and nonsusceptible to wild-type nematodes. Transformation caused no detectable change in virulence of nematodes to any test invertebrates. Transgenic and wild-type nematodes were also injected interperitoneally into mice and transgenic nematodes were fed by injection to mice without mouse mortality or changes in growth rate. We conclude that genetic engineering has provided a precise method to alter the heat shock tolerance of H. bacteriophora without affecting other important life history characteristics and that the transgenic nematode is unlikely to pose any threat to the environment if released on a wide scale.