Abstract
Hematophagous insects transmit infectious diseases. Sand flies are vectors of leishmaniasis, but can also transmit viruses. We have been studying immune responses of Lutzomyia longipalpis, the main vector of visceral leishmaniasis in the Americas. We identified a non-specific antiviral response in L. longipalpis LL5 embryonic cells when treated with non-specific double-stranded RNAs (dsRNAs). This response is reminiscent of interferon response in mammals. We are investigating putative effectors for this antiviral response. Secreted molecules have been implicated in immune responses, including interferon-related responses. We conducted a mass spectrometry analysis of conditioned medium from LL5 cells 24 and 48 h after dsRNA or mock treatment. We identified 304 proteins. At 24 h, 19 proteins had an abundance equal or greater than 2-fold change, while the levels of 17 proteins were reduced when compared to control cells. At the 48 h time point, these numbers were 33 and 71, respectively. The two most abundant secreted peptides at 24 h in the dsRNA-transfected group were phospholipid scramblase, an interferon-inducible protein that mediates antiviral activity, and forskolin-binding protein (FKBP), a member of the immunophilin family, which mediates the effect of immunosuppressive drugs. The transcription profile of most candidates did not follow the pattern of secreted protein abundance.
Highlights
Insect-borne diseases afflict billions of people throughout the world
Immune responses are triggered through the recognition of pathogen-associated molecular patterns (PAMPs) by host pattern recognition receptors (PRRs)
Binding of PAMPs leads to the activation of signaling pathways: RNA interference (RNAi), Janus kinase/signal transducers and activators of transcription (JAK/STAT), Immune Deficiency (IMD) and Toll [36,37,38,39]
Summary
Insect-borne diseases afflict billions of people throughout the world These illnesses are caused by different pathogens such as helminths, protists, bacteria, and viruses, which are the etiologic agents of diseases such as filariasis, leishmaniasis, babesiosis and dengue. The deleterious side effects of insecticide usage are widely known Among these are consequences to ecosystems, animal and human health, and development of resistance, pointing to the urgency of developing new control strategies. Our group has been studying the interaction and immune responses of the sand fly Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae), the most important vector of American visceral leishmaniasis [13], when infected with different pathogens [14,15,16]. We have detected complex immune responses in the Lutzomyia longipalpis LL5 embryonic cell line [20] when challenged by different pathogens [21]. LL5 cells, we carried out mass spectrometry (MS) analyses comparing the protein composition of conditioned medium from poly (I:C) and mock-treated LL5 cells
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