Delivery of a Genetically Marked Serratia AS1 to Medically Important Arthropods for Use in RNAi and Paratransgenic Control Strategies
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Understanding how arthropod vectors acquire their bacteria is essential for implementation of paratransgenic and RNAi strategies using genetically modified bacteria to control vector-borne diseases. In this study, a genetically marked Serratia AS1 strain expressing the mCherry fluorescent protein (mCherry-Serratia) was used to test various acquisition routes in six arthropod vectors including Anopheles stephensi, Culex pipiens, Cx. quinquefaciatus, Cx. theileri, Phlebotomus papatasi, and Hyalomma dromedarii. Depending on the species, the bacteria were delivered to (i) mosquito larval breeding water, (ii) host skin, (iii) sugar bait, and (iv) males (paratransgenic). The arthropods were screened for the bacteria in their guts or other tissues. All the hematophagous arthropods were able to take the bacteria from the skin of their hosts while taking blood meal. The mosquitoes were able to take up the bacteria from the water at larval stages and to transfer them transstadially to adults and finally to transfer them to the water they laid eggs in. The mosquitoes were also able to acquire the bacteria from male sperm. The level of bacterial acquisition was influenced by blood feeding time and strategies (pool or vessel feeding), dipping in water and resting time of newly emerged adult mosquitoes, and the disseminated tissue/organ. Transstadial, vertical, and venereal bacterial acquisition would increase the sustainability of the modified bacteria in vector populations and decrease the need for supplementary release experiments whereas release of paratransgenic males that do not bite has fewer ethical issues. Furthermore, this study is required to determine if the modified bacteria can be introduced to arthropods in the same routes in nature.
KeywordsSerratia AS1 Delivery methods RNAi Paratransgenesis
We thank Marcelo Jacobs-Lorena Professor of Molecular Microbiology and Immunology Deputy-Director, at Johns Hopkins Bloomberg School of Public Health, for his immense help with editing and critical reading of the manuscript. Also, we thank Ms. Salimi (Department of Medical Parasitology, SPH, and TUMS) for helping with fluorescent microscopy and Naser Ghasemi (Department of Medical Entomology and Vector Control, SPH, TUMS) for rearing mosquitoes.
This study was funded by the Tehran University of Medical Sciences, Iran, Grant numbers 30353 and 33613.
Compliance with Ethical Standards
All procedures were performed in accordance with the terms of the Iran Animals (Scientific Procedures) Act Project License and were approved by the Tehran University of Medical Sciences Ethical Review Committee.
Conflict of Interest
The authors declare that they have no conflict of interest.
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