Bacterial feeding, <it>Leishmania</it> infection and distinct infection routes induce differential defensin expression in <it>Lutzomyia longipalpis</it>

• Main Authors: Telleria Erich L, Sant’Anna Maurício R Viana, Alkurbi Mohammad O, Pitaluga André N, Dillon Rod J, Traub-Csekö Yara M
• Format: Article
• Language: English
• Published: BMC 2013-01-01
• Series: Parasites & Vectors
• Subjects: <it>Lutzomyia longipalpis</it>; Defensin; <it>Leishmania</it>; Bacteria
• Online Access: http://www.parasitesandvectors.com/content/6/1/12

<p>Abstract</p> <p>Background</p> <p>Phlebotomine insects harbor bacterial, viral and parasitic pathogens that can cause diseases of public health importance. <it>Lutzomyia longipalpis</it> is the main vector of visceral leishmaniasis in the New World. Insects can mount a powerful innate immune response to pathogens. Defensin peptides take part in this response and are known to be active against Gram-positive and Gram-negative bacteria, and some parasites. We studied the expression of a defensin gene from <it>Lutzomyia longipalpis</it> to understand its role in sand fly immune response.</p> <p>Methods</p> <p>We identified, sequenced and evaluated the expression of a <it>L</it>. <it>longipalpis</it> defensin gene by semi-quantitative RT-PCR. The gene sequence was compared to other vectors defensins and expression was determined along developmental stages and after exposure of adult female <it>L</it>. <it>longipalpis</it> to bacteria and <it>Leishmania</it>.</p> <p>Results</p> <p>Phylogenetic analysis showed that the <it>L</it>. <it>longipalpis</it> defensin is closely related to a defensin from the Old World sand fly <it>Phlebotomus duboscqi</it>. Expression was high in late L4 larvae and pupae in comparison to early larval stages and newly emerged flies. Defensin expression was modulated by oral infection with bacteria. The Gram-positive <it>Micrococcus luteus</it> induced early high defensin expression, whilst the Gram-negative entomopathogenic <it>Serratia marcescens</it> induced a later response. Bacterial injection also induced defensin expression in adult insects. Female sand flies infected orally with <it>Leishmania mexicana</it> showed no significant difference in defensin expression compared to blood fed insects apart from a lower defensin expression 5 days post <it>Leishmania</it> infection. When <it>Leishmania</it> was introduced into the hemolymph by injection there was no induction of defensin expression until 72 h later.</p> <p>Conclusions</p> <p>Our results suggest that <it>L</it>. <it>longipalpis</it> modulates defensin expression upon bacterial and <it>Leishmania</it> infection, with patterns of expression that are distinct among bacterial species and routes of infection.</p>