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  • Sant Anna et al 2009

    Rights statement: © 2009 Sant'Anna et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Inhibition of trypsin expression in Lutzomyia longipalpis using RNAi enhances the survival of Leishmania

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Article number62
<mark>Journal publication date</mark>9/12/2009
<mark>Journal</mark>Parasites and Vectors
Volume2
Number of pages10
Publication statusPublished
Original languageEnglish

Abstract

Background
Leishmania parasites must overcome several barriers to achieve transmission by their sand fly vectors. One of the earliest threats is exposure to enzymes during blood meal digestion. Trypsin-like enzymes appear to be detrimental to parasite survival during the very early phase of development as amastigotes transform into promastigote stages. Here, we investigate whether parasites can affect trypsin secretion by the sand fly midgut epithelium and if inhibition of this process is of survival value to the parasites.

Results
Infections of Lutzomyia longipalpis with Leishmania mexicana were studied and these showed that infected sand flies produced less trypsin-like enzyme activity during blood meal digestion when compared to uninfected controls. RNA interference was used to inhibit trypsin 1 gene expression by micro-injection into the thorax, as trypsin 1 is the major blood meal induced trypsin activity in the sand fly midgut. Injection of specific double stranded RNA reduced trypsin 1 expression as assessed by RT-PCR and enzyme assays, and also led to increased numbers of parasites in comparison with mock-injected controls. Injection by itself was observed to have an inhibitory effect on the level of infection, possibly through stimulation of a wound repair or immune response by the sand fly.

Conclusion
Leishmania mexicana was shown to be able to modulate trypsin secretion by Lutzomyia longipalpis to its own advantage, and direct inhibition of trypsin gene expression led to increased parasite numbers in the midguts of infected flies. Successful application of RNA interference methodology to Leishmania-infected sand flies now opens up the use of this technique to study a wide range of sand fly genes and their role in the parasite-vector interaction.

Bibliographic note

© 2009 Sant'Anna et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.