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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. [ABSTRACT FROM AUTHOR]

Abstract: Ticks transmit zoonotic pathogens worldwide. Nevertheless, very little information is available on their genome, transcriptome and proteome. Herein, we characterized the proteome of Amblyomma americanum adults and nymphs because of their role in pathogen transmission and compared the proteome of A. americanum, A. cajennense and A. variegatum adult ticks. We also used de novo sequencing proteomics data for the analysis of the phylogenetic relationships between the three Amblyomma spp. in a proof of concept for phyloproteomics. The results showed that host and tick proteins involved in blood digestion, heme detoxification, development and innate immunity were differentially represented between adults and nymphs. Although these ticks were unfed, over-represented host proteins may supply nutrients during off-host periods. Tick proteins involved in tick attachment, feeding, heat shock response, protease inhibition and heme detoxification were differentially represented between Amblyomma spp., suggesting adaptation processes to biotic and abiotic factors. These results suggested that phyloproteomics might be a useful tool for the phylogenetic analysis of tick species in which sequence data is a limiting factor and demonstrate the possibilities of proteomics studies for the characterization of relevant tick vector species and provide new relevant information to understand the physiology, development and evolution of these tick species. Biological significance: This is the first report on the proteome of the most important Amblyomma tick species for their relevance as vectors of zoonotic pathogens worldwide. Nevertheless, very little information is available on the genome, transcriptome and proteome of these vector ectoparasites. The results reported herein provide new relevant information to understand the physiology, development and evolution of these tick species. Phyloproteomics using de novo protein sequencing was assayed as a new approach for the phylogenetic analysis of tick species in which sequence data is a limiting factor.This article is part of a Special Issue entitled: Proteomics of non-model organisms. [Copyright &y& Elsevier]

Highlights: [•] Tick physiological factors may affect BM86 tick vaccine efficacy. [•] The proteome of R. annulatus (Ra) and R. microplus (Rm) were compared. [•] Ra ingest less blood than Rm, a difference that increases with vaccination. [ • ] Tick protein degradation machinery was under represented in Ra when compared to Rm. [•] Lesser protease activity in Ra correlates with higher vaccine efficacy. [ABSTRACT FROM AUTHOR]