Efficacy of Native and Recombinant Cry1B Protein Against Experimentally Induced and Naturally Acquired Ovine Myiasis (Fly Strike) in Sheep

Abstract

Several hundred strains of Bacillus thuringiensis (Bt), isolated in New Zealand from samples of soil and sheep fleece, were tested for toxicity to larvae of the blowfly Lucilia cuprina Wiedemann. Characterization of the Bt strains revealed that three of the more active strains produced Cry1Ba (an insecticidal protein present in Bt mother cell crystal inclusion) that was toxic to blowflies. These strains were evaluated for the ability to prevent experimentally induced fly strike in a bioassay by using first instars. Results with undiluted spore/crystal preparations were variable, but they generally prevented fly strike on sheep maintained on pasture for 3-6 wk. Spore viability was satisfactory throughout the trials and environmental factors (e.g., precipitation and UV radiation) seemed to have minimal effect on persistence. The loss of fly strike protection in these experiments correlated with the movement of spore/crystal toxicity away from the skin as a result of wool growth. Solubilized protein preparations were not as potent as spore/crystal preparations and fly strike protection lasted only from 1 to 3 wk. Vegetative forms of the Cry1Ba-producing strains of Bt did not establish on the fleece of sheep, did not produce significant sporulation, and no protection against fly strike was achieved. Escherichia coli expressing recombinant Cry1Ba protein was toxic to larvae in vitro but did not effectively protect sheep from fly strike because blowfly larvae were able to establish readily 8 d posttreatment. In a single field experiment involving 80 sheep per group, a spore/crystal preparation from a Bt strain expressing Cry1Ba provided less protection from naturally acquired fly strike than afforded by a commercially available dip.

Expression and lytic efficacy assessment of theStaphylococcus aureusphage SA4 lysin gene

“…The lytic range of the expressed lysin was found to be low compared to the native lysin [20]. Our results are in agreements with earlier observations [9,11] showing that the native protein provides better protection than recombinant ones.…”

Lucilia cuprina genome unlocks parasitic fly biology to underpin future interventions

“…Conspicuous among the 79 druggable molecules are seven transporters and four ion channels that could represent primary targets for multiple classes of natural or synthetic insecticidal compounds. Other candidates among the 79 druggable proteins include 19 kinases, five peptidases, five growth factor receptors and seven TFs, some of which have been suggested as targets for proteinase inhibitors 49 , genetically modified baculoviruses 50 or Bacillus thuringiensis endotoxins 51 .…”

Insecticidal activity of Bacillus thuringiensis crystal proteins

“…2. Within the Lepidoptera-active Cry1 family, cross-order activity includes toxicity of Cry1Ab and Cry1Ac to Diptera (Aedes aegypti, Glossina morsitans, respectively; Haider et al, 1986 andOmolo et al, 1997) and possibly Hemiptera (Macrosiphum euphorbiae; Walters and English, 1995); of Cry1Ba to Coleoptera (Leptinotarsa decemlineata, Chrysomela scripta, Anthonomus grandis; Bradley et al, 1995;Federici and Bauer, 1998;Martins et al, 2006;Naimov et al, 2001;Zhong et al 2000) and Diptera (Lucilia cuprina, Musca domestica; Heath et al, 2004;Zhong et al, 2000); of Cry1Ca to Diptera (Aedes aegypti, Anopheles stephensi, Culex quinquefasciatus; Smith et al, 1996); and of Cry1Ia to Coleoptera (L. decemlineata, Anthonomus grandis; Naimov et al, 2001;Tailor et al, 1992;Ruiz de Escudero et al, 2006;Martins et al, 2008). The Cry2Aa protein was found to have hemipteran activity (M. euphorbiae; Sims, 1997) in addition to its previously known dipteran and lepidopteran activities.…”