Bacterial feeding, leishmania infection and distinct infection routes induce differential defensin expression in Lutzomyialongipalpis

Telleria, Erich L and Sant'anna, Maurício R Viana and Alkurbi, Mohammad O and Pitaluga, André N and Dillon, Rod J and Traub-Csekö, Yara M (2013) Bacterial feeding, leishmania infection and distinct infection routes induce differential defensin expression in Lutzomyialongipalpis. Parasites and Vectors, 6 (1). ISSN 1756-3305

Abstract

BACKGROUND: Phlebotomine insects harbor bacterial, viral and parasitic pathogens that can cause diseases of public health importance. Lutzomyialongipalpis 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 Lutzomyialongipalpis to understand its role in sand fly immune response. METHODS: We identified, sequenced and evaluated the expression of a L. longipalpisdefensin 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 L. longipalpis to bacteria and Leishmania. RESULTS: Phylogenetic analysis showed that the L. longipalpisdefensin is closely related to a defensin from the Old World sand fly Phlebotomusduboscqi. 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 Micrococcus luteus induced early high defensin expression, whilst the Gram-negative entomopathogenicSerratiamarcescens induced a later response. Bacterial injection also induced defensin expression in adult insects. Female sand flies infected orally with Leishmaniamexicana showed no significant difference in defensin expression compared to blood fed insects apart from a lower defensin expression 5 days post Leishmania infection. When Leishmania was introduced into the hemolymph by injection there was no induction of defensin expression until 72 h later. CONCLUSIONS: Our results suggest that L. longipalpis modulates defensin expression upon bacterial and Leishmania infection, with patterns of expression that are distinct among bacterial species and routes of infection.