The paratransgenic sand fly: A platform for control of <it>Leishmania </it>transmission

• Main Authors: Hillesland Heidi, Hurwitz Ivy, Fieck Annabeth, Das Pradeep, Durvasula Ravi
• Format: Article
• Language: English
• Published: BMC 2011-05-01
• Series: Parasites & Vectors
• Online Access: http://www.parasitesandvectors.com/content/4/1/82

<p>Abstract</p> <p>Background</p> <p><it>Leishmania donovani </it>is transmitted by the bite of the sand fly, <it>Phlebotomus argentipes</it>. This parasite is the agent of visceral leishmaniasis (VL), an endemic disease in Bihar, India, where prevention has relied mainly on DDT spraying. Pesticide resistance in sand fly populations, environmental toxicity, and limited resources confound this approach. A novel paratransgenic strategy aimed at control of vectorial transmission of <it>L. donovani </it>is presented using <it>Bacillus subtilis</it>, a commensal bacterium isolated from the sand fly gut. In this work, <it>B. subtilis </it>expressing Green Fluorescent Protein (GFP) was added to sterilized larval chow. Control pots contained larval chow spiked either with untransformed <it>B. subtilis </it>or phosphate-buffered saline. Fourth-instar <it>P. argentipes </it>larvae were transferred into the media and allowed to mature. The number of bacterial colony forming units, relative abundance and the mean microbial load were determined per developmental stage.</p> <p>Results</p> <p>Addition of <it>B. subtilis </it>to larval chow did not affect sand fly emergence rates. <it>B. cere</it>us and <it>Lys fusiformis </it>were identified at each developmental stage, revealing transstadial passage of endogenous microbes. Larvae exposed to an exogenous bolus of <it>B. subtilis </it>harbored significantly larger numbers of bacteria. Bacterial load decreased to a range comparable to sand flies from control pots, suggesting an upper limit to the number of bacteria harbored. Emerging flies reared in larval chow containing transformed <it>B. subtilis </it>carried large numbers of these bacteria in their gut lumens. Strong GFP expression was detected in these paratransgenic flies with no spread of transformed bacteria to other compartments of the insects. This is the first demonstration of paratransgenic manipulation of <it>P. argentipes</it>.</p> <p>Conclusions</p> <p>Paratransgenic manipulation of <it>P. argentipes </it>appears feasible. Expression of leishmanicidal molecules via commensal bacteria commonly found at breeding sites of <it>P. argentipes </it>could render adult sand flies refractory to <it>L. donovani </it>infection.</p>