No description available.

This thesis reports on an unknown/orphan gene from the sheep tick <i>Ixodes ricinus, </i>so named <i>RicOrph17, </i>that was identified by mass spectrometry while attempting to isolate a hydrolase protein by a chromatographic approach.  <i>Ric</i>Orph17 was “deorphanised” employing bioinformatics, gene-knockdown and recombinant protein production to determine its function. Primers were designed to screen an <i>I.</i><i> ricinus </i>cDNA library to obtain the full length sequence of the gene.  The <i>RicOrph17</i> open reading frame encodes a 145 amino acid polypeptide, including a putative 26-amino acids signal peptide and a 26-coding region with a putative GPI-anchoring site.  The deduced <i>Ric</i>Orph17 protein shared some structural features of the three finger protein family, including a cysteine skeleton responsible for the formation of disulfide bonds.  <i>Ric</i>Orph17 has close homologues in many different insects species. RT-PCR analysis showed that <i>RicOrph17</i> was expressed in various tissues and at different life stages. <i>RicOrph17</i> was not up regulated upon bacterial challenge.  Injection of <i>RicOrph17-</i>dsRNA into unfed adult ticks silenced the target gene expression in the whole tick.  Such dsRNA-injected ticks challenged with <i>E. coli </i>showed higher morality compared to the control injected ticks.  Recombinant <i>Ric</i>Orph17 lacking the signal peptide and the GPI-anchor peptide was produced in <i>E. coli </i>Origami cells to assist the determination of its function.  Rec<i>Ric</i>Orph17 possessed potent antibacterial activity against Gram +ve, -ve bacteria and yeast. FITC-labelled rec<i>Ric</i>Orph17 accumulated inside bacteria and did not remain embedded in the bacterial membrane.  Further, rec<i>Ric</i>Orph17 was demonstrated to bind DNA in gel retardation studies.  Taken together, these results suggest that <i>Ric</i>Orph17 is a novel GPI-linked antimicrobial peptide with an intracellular target involved in tick immunity.

No description available.

The flavivirus genus is of major concern for world morbidity and mortality and includes viruses causing both encephalitic as well as hemorrhagic diseases. The incidence of Tick-borne encephalitis is increasing in many European countries and several reports have emphasized the expansion of the main vector, Ixodes ricinus. The pattern of vector distribution is also changing in Sweden, which makes it important to set up solid and successful strategies for detection and genetic characterization of novel Swedish TBEV strains. In this study we have generated strategies for detection of broad types of tick-borne flaviviruses in pools of I. ricinus sampled in Sweden. The positive collection on the island of Torö was used to generate a sequence of a complete TBEV genome straight from the arthropod reservoir. This cloned virus was used to construct a self-replicating DNA based sub-genomic TBEV replicon capable of expressing reporter genes. The replicon was used to study the effect of TBEV on neurite outgrowth, which revealed that the MTase domain of NS5 block the formation of the Scribble/Rac1/βPIX protein complex, impairing neurite outgrowth in neuronal growth factor induced PC12 cells. We also demonstrate that TBEV replication is affected by two PDZ binding motifs within NS5 and reveal putative PDZ binding proteins. These interactions might affect cellular pathways and might have a role in flavivirus replication. We also characterize the variable 3´ non-coding region (V3’-NCR) by in silico studies on TBEV. Analysis brings new evidence that V3’-NCR region carries an enhancer element important for different replication/translation dynamics during the viral lifecycle in mammalian and tick cells. We also propose a temperature-sensitive trans-acting riboswitch mechanism; altering the secondary RNA structures of a closed form at lower temperatures and a form open for translation at higher temperatures. This mechanism may explain the low TBEV level observed in sampled ticks. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

The overall goal of this research was to examine the interactions of adult Amblyomma maculatum Koch, the Gulf Coast tick, with respect to their utilization of hosts and to male-female cross strain interaction. Historical data along with two Petri dish experiments were used to understand male-female interaction in the field, and to determine if the aggregation attachment pheromone (AAP) produced by fed males of varying strains is attractive to geographic specific strains of unfed female ticks. It was hypothesized that questing female Gulf Coast ticks are attracted to fed males and can discriminate between grazing cattle with fed males and those without. Archival control data from ear tag studies conducted in 1985, 1987, and 1991 were analyzed to better understand female Gulf Coast tick behavior in the field relative to fed male tick presence. Females were found primarily on hosts with an abundance of male ticks, leading one to conclude that female ticks are attracted to hosts infested with male ticks. It was also discovered that females were more likely to be found on a host as the number of males on a host increased. A female’s ability to detect hosts parasitized by males likely allows them to feed and mate on-host in a fairly limited period of time. A Petri dish bioassay was used to evaluate female preference to varying geographic strains of fed males. One experiment was designed to determine if a female preferred fed males from her geographically specific strain over other males. A second experiment evaluated female response to a non-specific male in the absence of her geographically specific male. While female responses to fed males regardless of strain were higher than to unfed male control ticks, no statistical differences in female response could be determined. The Petri dish bioassay was determined to be inadequate to test female preference over several populations of pheromone producing males, and a more intensive procedure was proposed.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (Ph.D.)--Murdoch University, 2007. / Thesis submitted to the Division of Health Sciences. Includes bibliographical references (leaves 145-189).

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on March 9, 2009). Includes bibliographical references.

The proposed thesis brings new information on several aspects of tick glycobiology - tick N-glycans, tick lectins, and glycosylation of the tick-borne pathogen, Lyme disease spirochetes Borrelia burgdorferi s.l.