Dermacentor reticulatus (Acari, Ixodidae) female feeding in laboratory

The effects of host, size of tick males and tick density per host on feeding of Dermacentor reticulatus females were investigated in the laboratory. Comparison of feeding performances on laboratory animals suggests that mice and rabbits are more suitable hosts than guinea pigs. The size of male ticks did not influence the feeding rate of females. Density of tick pairs per host influenced finally the length of female feeding, however, other female characteristics were the same

Sexual differences in the sialomes of the zebra tick, Rhipicephalus pulchellus

10.1016/j.jprot.2014.12.014Journal of Proteomics117120-14

Anti-interleukin-8 activity of tick salivary gland extracts

Interleukin-8 (IL-8) is one of many mammalian chemokines (chemotactic cytokines) that direct mammalian inflammatory and immune cells to sites of injury and infection. Chemokines are produced locally and act on leucocytes through selective receptors. The principal role of IL-8 is to control the movement and activity of neutrophils. To date, several tick species have been shown to modulate the production or activity of certain cytokines but none of these are chemokines. Using an IL-8 specific ELISA, we showed that salivary gland extracts (SGE) from several ixodid tick species (Dermacentor reticulatus, Amblyomma variegatum, Rhipicephalus appendiculatus, Haemaphysalis inermis and Ixodes ricinus) reduced the level of detectable IL-8. Analyses of fractionated SGE revealed one similar peak of activity for D. reticulatus, A. variegatum and R. appendiculatus; a second peak, observed for D. reticulatus and A. variegatum, differed between the two species. Using radiolabelled IL-8, SGE and peak activity fractions of D. reticulatus were shown to bind the chemokine, and to inhibit binding of IL-8 to its receptors on human granuolocytes enriched for neutrophils. The biological significance of these observations was demonstrated by the ability of SGE to inhibit IL-8 induced chemotaxis of human blood granulocytes. Future isolation and characterization of the active molecules will enable determination of their functional roles in bloodfeeding and effect on tick-borne pathogen transmissio

Transcriptional Immunoprofiling at the Tick-Virus-Host Interface during Early Stages of Tick-Borne Encephalitis Virus Transmission

Emerging and re-emerging diseases transmitted by blood feeding arthropods are significant global public health problems. Ticks transmit the greatest variety of pathogenic microorganisms of any blood feeding arthropod. Infectious agents transmitted by ticks are delivered to the vertebrate host together with saliva at the bite site. Tick salivary glands produce complex cocktails of bioactive molecules that facilitate blood feeding and pathogen transmission by modulating host hemostasis, pain/itch responses, wound healing, and both innate and adaptive immunity. In this study, we utilized Illumina Next Generation Sequencing to characterize the transcriptional immunoprofile of cutaneous immune responses to Ixodes ricinus transmitted tick-borne encephalitis virus (TBEV). A comparative immune gene expression analysis of TBEV-infected and uninfected tick feeding sites was performed. Our analysis reveals that ticks create an inflammatory environment at the bite site during the first 3 h of feeding, and significant differences in host responses were observed between TBEV-infected and uninfected tick feeding. Gene-expression analysis reveals modulation of inflammatory genes after 1 and 3 h of TBEV-infected tick feeding. Transcriptional levels of genes specific to chemokines and cytokines indicated a neutrophil-dominated immune response. Immunohistochemistry of the tick feeding site revealed that mononuclear phagocytes and fibroblasts are the primary target cells for TBEV infection and did not detect TBEV antigens in neutrophils. Together, the transcriptional and immunohistochemistry results suggest that early cutaneous host responses to TBEV-infected tick feeding are more inflammatory than expected and highlight the importance of inflammatory chemokine and cytokine pathways in tick-borne flavivirus transmission

Impact of genetic background on NVT of TBEV.

<p>A) Correlation of non-viratemic transmission (NVT) rates of different TBEV chimaeras with reproduction rate in different life stages of ticks. The trend lines are estimated by the polynomial method. The Pearson`s correlation coefficients between NVT rate (solid trend line) and titres in ticks (dashed lines) are shown by brackets with indicated r values. B) Correlation of TBEV gene replacements with NVT rate. The solid and dashed trend-lines reflect the changes in Hypr and Vs NVT rate efficiency respectively, in correspondence with size of exchanged gene fragments. Trend-lines were drawn using order 3 polynomial method with R-square value shown at the right end of the corresponding trend line. C) Correlation between NVT rate and the amino acid substitutions. The amino acid differences between C-prM-E region of polyprotein of control and chimaeric viruses are plotted on the X-axis as number of amino acid substitutions per site in comparison to VsIC sequence. The NVT rates are plotted on the Y-axis. The linear regression is calculated using equation [Y = 914.53*X + 4.77] and shown as solid line (goodness of fit R² = 0.58). The Pearson’s correlation coefficient (r) is shown in top left corner of the panel.</p

Efficiency of non-viraemic transmission of SIB-TBEV (Vs) and EU-TBEV (Hypr) between co-feeding <i>I</i>. <i>ricinus</i>.

<p>Two infected female ticks were placed in close proximity to 15 uninfected nymphs on the same skin site of laboratory mice. Following three days of co-feeding, nymphs were removed and virus titres determined by plaque titration. The mean transmission rate is expressed as percentage of positive nymphs in which TBEV was detected.</p

Chimaeric virus growth kinetics in cell culture.

<p>Viruses are specified as shown in the text. PS cells were infected with TBEV at a multiplicity of 1 pfu per cell in at least 4 replicates. Samples of cell culture media were collected every 4 hours during the first day pi and then once a day. Virus infectivity was established by plaque assay. A-C) HyprIC and Hypr-based recombinant viruses; D-F) VsIC and Vs-based recombinant viruses. Error bars reflect 95% confidence intervals.</p

Virion stability.

<p>Identical aliquots of virus suspension were treated as indicated in chart legend (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158105#sec013" target="_blank">Materials and Methods</a>) with virus titres determined by plaque infectivity assay. Error bars show 95% confidence intervals from the mean across three replicates.</p

TBEV replication in mice following transmission from ticks.

<p>Mice infected via tick bites during the NVT experiments were observed for 21 days and cumulative numbers of challenged and moribund mice were analysed. A) Survival dynamics of mice infected with Vs-based (green lines/bars) chimaeras; B) Survival dynamics of mice infected with Hypr-based (red lines/bars) chimaeras. The probabilities of survival were estimated using Kaplan-Meier method; C) Correlation between mouse morbidity and infectious dose of TBEV in adult tick salivary glands following the termination of co-feeding. The data are arranged in descending order of mouse morbidity. The trend lines were drawn using the order 4 polynomial method (R² ≥ 0.95). The (r) value in the top right corner of the chart reflects the Pearson’s coefficient of correlation between datasets.</p

Vs and Hypr chimaeric viruses.

<p>A) The polyproteins, with individual proteins of Hypr virus (grey bars) and Vs virus (white bars) are flanked with 3`UTR (thick and thin lines for Hypr and Vs respectively). B) Schematic representation of the 3`UTRs., Numbers specify nucleotide positions in 3’UTRs following the stop codon. Internal deletions present in the Hypr and Vs genomes are identified by the numbers corresponding to those of the Hypr-long 3’UTR. Intermediate plasmids, constructed to recover Hypr, Vs and chimaeric Hypr/Vs infectious virus, are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158105#pone.0158105.s001" target="_blank">S1 Fig</a>.</p