Molecular aspects of immunity of Lutzomyia longipalpis (Díptera: Psychodidae).
Sandflies are known for the transmission of leishmaniasis but can also transmit viral and bacterial diseases. Also, sandflies get in contact with several insect pathogens like fungi andhelminths. The strategies used by sandflies for defense against pathogens are mostly unknown. The main infection path is through blood feeding and the midgut is the first immunity related tissue. For these reasons, the midgut transcriptome was analyzed. EST sequencing was performed on 3 differentcDNA libraries from female midguts 6 (6h) and 72 (72h) hours post blood feeding, and after 72 hours of Leishmania chagasi infection (Inf). Several of the identified genes were related to digestion and defense. The comparative analysis of the libraries showed a higher number of defense related genes (e.g. defensin, serpin, PGRP) in Inf and an increase of digestion related genes (e.g. tripsins, VATPases, Kazal) in 6h. Two trypsins were identified previously, Lltryp1 is expressed between 2 and 48 hours post-blood feeding and Lltryp2 is constitutively expressed, although it is down regulated by blood digestion. Lltryp1 is absent from developmental stages while Lltryp2 is expressed mainly after L3 stage. Blood feeding also modulates V-ATPase. After feeding, its expression increases until 48hour followed by a decrease after 72 hours. During the developmental stages, the expression increases constantly until pupae and males. The antimicrobial peptide (AMP) defensin was among the immune related genes identified. Blood feeding also modulates this AMP; it is upregulated during the first hours of digestion followed by a down regulation after 72 hours and is absent from initial larvae stages. In an attempt of silence immunity related genes in L. longipalpis cell line (LL5) using the RNAi mechanism, an unexpected nonspecific antiviral response was identified. The replication of virus-like particles from west Nile virus was inhibited by dsRNAs unrelated with the virus. This was the first description of such anti-viral response in insects and could have great significance in insect arbovirusvectorial capacity. With these data, we hope to improve the knowledge on sandfly immunity and also to better understand vector/pathogens interactions. This information might also help on the identification of putative molecular targets for the development of blocking transmission vaccines and in the studies of immune system evolution.
Advisor:Yara Maria Traub-Cseko
School:Faculdades Oswaldo Cruz
Source Type:Master's Thesis
Keywords:Psychodidae Leishmania Expressed Sequence Tags Adenosine Triphosphatases
Date of Publication:12/10/2007