Sand flies, which transmit diseases like leishmaniases, bartonellosis, and certain viruses, pose a significant public health threat. Our research focuses on the immune responses of Lutzomyia longipalpis, the primary vector for visceral leishmaniasis in the Americas. We use L. longipalpis LL5 cells as a model to study how sand flies respond to pathogens. These cells exhibit robust immune reactions, producing molecules mainly regulated by the Toll, IMD, Jak-STAT, and RNAi pathways. In previous studies, we detected a non-specific antiviral response in LL5 cells following double-stranded RNAs (dsRNAs) transfection. A previous complete secretome of these cells showed molecules resembling an interferon-like antiviral response when transfected with polyinosinic-polycytidylic acid (poly I:C), a synthetic dsRNA analog. In the current study, we analyzed soluble proteins secreted by LL5 cells after poly I:C transfection. Using comparative mass spectrometry, we examined protein composition of conditioned media depleted of exosomes at 24 h and 48 h. Most proteins uniquely expressed in the transfected groups had low abundance compared to the overall expressed proteins. Interactome prediction analysis revealed that at 24 h, the proteins uniquely found in the secretome of the transfected group were involved in RNA degradation and purine metabolism, while at 48 h they were linked to ribosomal proteins and signaling pathways such as Hedgehog, Transforming Growth Factor-beta (TGF-β), and Wingless/integrated (Wnt). We highlight increased abundance of the TGF-β-induced protein ig-h3 (24 h and 48 h), a Toll-like receptor 3 (48 h), and a hemocytin (48 h) in the secretion of transfected groups compared to the controls. We also performed an interaction analysis of proteins more secreted by the treated group at 24 h and 48 h. Unlike the interactome of uniquely identified proteins, few interactions were observed at 24 h, with a predominance of extracellular matrix and cell adhesion proteins. The set of proteins more secreted at 48 h presented more interactions than at 24 h, with emphasis on catabolic processes, including RNA degradation. These findings indicate that poly I:C transfection in LL5 cells induces the secretion of proteins involved in cellular defense and repair, revealing molecules involved in the LL5 non-specific antiviral response.

• Klíčová slova
• RNA degradation, cell repair, non-specific antiviral response, poly I:C, sand fly cell line, secreted proteins,
• MeSH
• buněčné linie MeSH
• dvouvláknová RNA * genetika   MeSH
• hmyzí proteiny * metabolismus   MeSH
• poly I-C MeSH
• proteom * analýza   MeSH
• proteomika MeSH
• Psychodidae * imunologie   metabolismus   genetika   MeSH
• sekretom * MeSH
• signální transdukce MeSH
• transfekce MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dvouvláknová RNA * MeSH
• hmyzí proteiny * MeSH
• poly I-C MeSH
• proteom * MeSH

INTRODUCTION: Sand flies (Diptera: Phlebotominae) belonging to the Lutzomyia genus transmit Leishmania infantum parasites. To understand the complex interaction between the vector and the parasite, we have been investigating the sand fly immune responses during the Leishmania infection. Our previous studies showed that genes involved in the IMD, Toll, and Jak-STAT immunity pathways are regulated upon Leishmania and bacterial challenges. Nevertheless, the parasite can thrive in the vectors' gut, indicating the existence of mechanisms capable of modulating the vector defenses, as was already seen in mammalian Leishmania infections. METHODS RESULTS AND DISCUSSION: In this study, we investigated the expression of Lutzomyia longipalpis genes involved in regulating the Toll pathway under parasitic infection. Leishmania infantum infection upregulated the expression of two L. longipalpis genes coding for the putative repressors cactus and protein tyrosine phosphatase SHP. These findings suggest that the parasite can modulate the vectors' immune response. In mammalian infections, the Leishmania surface glycoprotein GP63 is one of the inducers of host immune depression, and one of the known effectors is SHP. In L. longipalpis we found a similar effect: a genetically modified strain of Leishmania amazonensis over-expressing the metalloprotease GP63 induced a higher expression of the sand fly SHP indicating that the L. longipalpis SHP and parasite GP63 increased expressions are connected. Immuno-stained microscopy of L. longipalpis LL5 embryonic cells cultured with Leishmania strains or parasite conditioned medium showed cells internalization of parasite GP63. A similar internalization of GP63 was observed in the sand fly gut tissue after feeding on parasites, parasite exosomes, or parasite conditioned medium, indicating that GP63 can travel through cells in vitro or in vivo. When the sand fly SHP gene was silenced by RNAi and females infected by L. infantum, parasite loads decreased in the early phase of infection as expected, although no significant differences were seen in late infections of the stomodeal valve. CONCLUSIONS: Our findings show the possible role of a pathway repressor involved in regulating the L. longipalpis immune response during Leishmania infections inside the insect. In addition, they point out a conserved immunosuppressive effect of GP63 between mammals and sand flies in the early stage of parasite infection.

• Klíčová slova
• SHP-2, immunity, protein-tyrosine phosphatase, sand fly, signaling pathway, vector-parasite interaction,
• MeSH
• imunosupresivní léčba MeSH
• kultivační média speciální MeSH
• Leishmania infantum * MeSH
• leishmanióza * MeSH
• Phlebotomus * MeSH
• Psychodidae * MeSH
• savci MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kultivační média speciální MeSH

Toscana virus (TOSV) (Bunyavirales, Phenuiviridae, Phlebovirus, Toscana phlebovirus) and other related human pathogenic arboviruses are transmitted by phlebotomine sand flies. TOSV has been reported in nations bordering the Mediterranean Sea among other regions. Infection can result in febrile illness as well as meningitis and encephalitis. Understanding vector-arbovirus interactions is crucial to improving our knowledge of how arboviruses spread, and in this context, immune responses that control viral replication play a significant role. Extensive research has been conducted on mosquito vector immunity against arboviruses, with RNA interference (RNAi) and specifically the exogenous siRNA (exo-siRNA) pathway playing a critical role. However, the antiviral immunity of phlebotomine sand flies is less well understood. Here we were able to show that the exo-siRNA pathway is active in a Phlebotomus papatasi-derived cell line. Following TOSV infection, distinctive 21 nucleotide virus-derived small interfering RNAs (vsiRNAs) were detected. We also identified the exo-siRNA effector Ago2 in this cell line, and silencing its expression rendered the exo-siRNA pathway largely inactive. Thus, our data show that this pathway is active as an antiviral response against a sand fly transmitted bunyavirus, TOSV.

• MeSH
• arboviry * genetika   MeSH
• lidé MeSH
• malá interferující RNA genetika   MeSH
• Phlebotomus * genetika   MeSH
• Phlebovirus * genetika   MeSH
• Psychodidae * genetika   MeSH
• RNA interference MeSH
• virus horečky pappataci * genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• malá interferující RNA MeSH

Antimicrobial peptides (AMPs) are produced to control bacteria, fungi, protozoa, and other infectious agents. Sand fly larvae develop and feed on a microbe-rich substrate, and the hematophagous females are exposed to additional pathogens. We focused on understanding the role of the AMPs attacin (Att), cecropin (Cec), and four defensins (Def1, Def2, Def3, and Def4) in Lutzomyia longipalpis, the main vector of visceral leishmaniasis in the Americas. Larvae and adults were collected under different feeding regimens, in addition to females artificially infected by Leishmania infantum. AMPs' gene expression was assessed by qPCR, and gene function of Att and Def2 was investigated by gene silencing. The gene knockdown effect on bacteria and parasite abundance was evaluated by qPCR, and parasite development was verified by light microscopy. We demonstrate that L. longipalpis larvae and adults trigger AMPs expression during feeding, which corresponds to an abundant presence of bacteria. Att and Def2 expression were significantly increased in Leishmania-infected females, while Att suppression favored bacteria growth. In conclusion, L. longipalpis AMPs' expression is tuned in response to bacteria and parasites but does not seem to interfere with the Leishmania cycle.

• Klíčová slova
• Leishmania, Lutzomyia longipalpis, RNAi gene silencing, antimicrobial peptides, innate immunity, microbiota,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Ixodid ticks are important vectors of a wide variety of viral, bacterial and protozoan pathogens of medical and veterinary importance. Although several studies have elucidated tick responses to bacteria, little is known about the tick response to viruses. To gain insight into the response of tick cells to flavivirus infection, the transcriptomes and proteomes of two Ixodes spp cell lines infected with the flavivirus tick-borne encephalitis virus (TBEV) were analysed. METHODS: RNA and proteins were isolated from the Ixodes scapularis-derived cell line IDE8 and the Ixodes ricinus-derived cell line IRE/CTVM19, mock-infected or infected with TBEV, on day 2 post-infection (p.i.) when virus production was increasing, and on day 6 p.i. when virus production was decreasing. RNA-Seq and mass spectrometric technologies were used to identify changes in abundance of, respectively, transcripts and proteins. Functional analyses were conducted on selected transcripts using RNA interference (RNAi) for gene knockdown in tick cells infected with the closely-related but less pathogenic flavivirus Langat virus (LGTV). RESULTS: Differential expression analysis using DESeq resulted in totals of 43 and 83 statistically significantly differentially-expressed transcripts in IDE8 and IRE/CTVM19 cells, respectively. Mass spectrometry detected 76 and 129 statistically significantly differentially-represented proteins in IDE8 and IRE/CTVM19 cells, respectively. Differentially-expressed transcripts and differentially-represented proteins included some that may be involved in innate immune and cell stress responses. Knockdown of the heat-shock proteins HSP90, HSP70 and gp96, the complement-associated protein Factor H and the protease trypsin resulted in increased LGTV replication and production in at least one tick cell line, indicating a possible antiviral role for these proteins. Knockdown of RNAi-associated proteins Argonaute and Dicer, which were included as positive controls, also resulted in increased LGTV replication and production in both cell lines, confirming their role in the antiviral RNAi pathway. CONCLUSIONS: This systems biology approach identified several molecules that may be involved in the tick cell innate immune response against flaviviruses and highlighted that ticks, in common with other invertebrate species, have other antiviral responses in addition to RNAi.

• MeSH
• arachnida jako vektory * genetika   metabolismus   virologie   MeSH
• buněčné linie MeSH
• genový knockdown MeSH
• klíště * genetika   imunologie   metabolismus   virologie   MeSH
• přirozená imunita MeSH
• proteomika * MeSH
• RNA interference MeSH
• stanovení celkové genové exprese * MeSH
• viry klíšťové encefalitidy imunologie   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH