Comparative analysis of whole cell-derived vesicular delivery systems for photodynamic therapy of extrahepatic cholangiocarcinoma.

This first-in-its-class proof-of-concept study explored the use of bionanovesicles for the delivery of photosensitizer into cultured cholangiocarcinoma cells and subsequent treatment by photodynamic therapy (PDT). Two types of bionanovesicles were prepared: cellular vesicles (CVs) were fabricated by sonication-mediated nanosizing of cholangiocarcinoma (TFK-1) cells, whereas cell membrane vesicles (CMVs) were produced by TFK-1 cell and organelle membrane isolation and subsequent nanovesicularization by sonication. The bionanovesicles were loaded with zinc phthalocyanine (ZnPC). The CVs and CMVs were characterized (size, polydispersity index, zeta potential, stability, ZnPC encapsulation efficiency, spectral properties) and assayed for tumor (TFK-1) cell association and uptake (flow cytometry, confocal microscopy), intracellular ZnPC distribution (confocal microscopy), dark toxicity (MTS assay), and PDT efficacy (MTS assay). The mean ±â€¯SD diameter, polydispersity index, and zeta potential were 134 ±â€¯1 nm, -16.1 ±â€¯0.9, and 0.220 ±â€¯0.013, respectively, for CVs and 172 ±â€¯3 nm, -16.4 ±â€¯1.1, and 0.167 ±â€¯0.022, respectively, for CMVs. Cold storage for 1 wk and incorporation of ZnPC increased bionanovesicular diameter slightly but size remained within the recommended range for in vivo application (136-220 nm). ZnPC was incorporated into CVs and CMVs at an optimal photosensitizer:lipid molar ratio of 0.006 and 0.01, respectively. Both bionanovesicles were avidly taken up by TFK-1 cells, resulting in homogenous intracellular ZnPC dispersion. Photosensitization of TFK-1 cells did not cause dark toxicity, while illumination at 671 nm (35.3 J/cm2) produced LC50 values of 1.11 µM (CVs) and 0.51 µM (CMVs) at 24 h post-PDT, which is superior to most LC50 values generated in tumor cells photosensitized with liposomal ZnPC. In conclusion, CVs and CMVs constitute a potent photosensitizer platform with no inherent cytotoxicity and high PDT efficacy in vitro.

Amplification and sequencing of entire tick mitochondrial genomes for a phylogenomic analysis.

The mitochondrial genome (mitogenome) has proven to be important for the taxonomy, systematics, and population genetics of ticks. However, current methods to generate mitogenomes can be cost-prohibitive at scale. To address this issue, we developed a cost-effective approach to amplify and sequence the whole mitogenome of individual tick specimens. Using two different primer sites, this approach generated two full-length mitogenome amplicons that were sequenced using the Oxford Nanopore Technologies' Mk1B sequencer. We used this approach to generate 85 individual tick mitogenomes from samples comprised of the three tick families, 11 genera, and 57 species. Twenty-six of these species did not have a complete mitogenome available on GenBank prior to this work. We benchmarked the accuracy of this approach using a subset of samples that had been previously sequenced by low-coverage Illumina genome skimming. We found our assemblies were comparable or exceeded the Illumina method, achieving a median sequence concordance of 99.98%. We further analyzed our mitogenome dataset in a mitophylogenomic analysis in the context of all three tick families. We were able to sequence 72 samples in one run and achieved a cost/sample of ~ $10 USD. This cost-effective strategy is applicable for sample identification, taxonomy, systematics, and population genetics for not only ticks but likely other metazoans; thus, making mitogenome sequencing equitable for the wider scientific community.

Metallated phthalocyanines and their hydrophilic derivatives for multi-targeted oncological photodynamic therapy.

BACKGROUND AND AIM: A photosensitizer (PS) delivery and comprehensive tumor targeting platform was developed that is centered on the photosensitization of key pharmacological targets in solid tumors (cancer cells, tumor vascular endothelium, and cellular and non-cellular components of the tumor microenvironment) before photodynamic therapy (PDT). Interstitially targeted liposomes (ITLs) encapsulating zinc phthalocyanine (ZnPC) and aluminum phthalocyanine (AlPC) were formulated for passive targeting of the tumor microenvironment. In previous work it was established that the PEGylated ITLs were taken up by cultured cholangiocarcinoma cells. The aim of this study was to verify previous results in cancer cells and to determine whether the ITLs can also be used to photosensitize cells in the tumor microenvironment and vasculature. Following positive results, rudimentary in vitro and in vivo experiments were performed with ZnPC-ITLs and AlPC-ITLs as well as their water-soluble tetrasulfonated derivatives (ZnPCS4 and AlPCS4) to assemble a research dossier and bring this platform closer to clinical transition. METHODS: Flow cytometry and confocal microscopy were employed to determine ITL uptake and PS distribution in cholangiocarcinoma (SK-ChA-1) cells, endothelial cells (HUVECs), fibroblasts (NIH-3T3), and macrophages (RAW 264.7). Uptake of ITLs by endothelial cells was verified under flow conditions in a flow chamber. Dark toxicity and PDT efficacy were determined by cell viability assays, while the mode of cell death and cell cycle arrest were assayed by flow cytometry. In vivo systemic toxicity was assessed in zebrafish and chicken embryos, whereas skin phototoxicity was determined in BALB/c nude mice. A PDT efficacy pilot was conducted in BALB/c nude mice bearing human triple-negative breast cancer (MDA-MB-231) xenografts. RESULTS: The key findings were that (1) photodynamically active PSs (i.e., all except ZnPCS4) were able to effectively photosensitize cancer cells and non-cancerous cells; (2) following PDT, photodynamically active PSs were highly toxic-to-potent as per anti-cancer compound classification; (3) the photodynamically active PSs did not elicit notable systemic toxicity in zebrafish and chicken embryos; (4) ITL-delivered ZnPC and ZnPCS4 were associated with skin phototoxicity, while the aluminum-containing PSs did not exert detectable skin phototoxicity; and (5) ITL-delivered ZnPC and AlPC were equally effective in their tumor-killing capacity in human tumor breast cancer xenografts and superior to other non-phthalocyanine PSs when appraised on a per mole administered dose basis. CONCLUSIONS: AlPC(S4) are the safest and most effective PSs to integrate into the comprehensive tumor targeting and PS delivery platform. Pending further in vivo validation, these third-generation PSs may be used for multi-compartmental tumor photosensitization.

Strategies for Improving Photodynamic Therapy Through Pharmacological Modulation of the Immediate Early Stress Response.

Photodynamic therapy (PDT) is a minimally to noninvasive treatment modality that has emerged as a promising alternative to conventional cancer treatments. PDT induces hyperoxidative stress and disrupts cellular homeostasis in photosensitized cancer cells, resulting in cell death and ultimately removal of the tumor. However, various survival pathways can be activated in sublethally afflicted cancer cells following PDT. The acute stress response is one of the known survival pathways in PDT, which is activated by reactive oxygen species and signals via ASK-1 (directly) or via TNFR (indirectly). The acute stress response can activate various other survival pathways that may entail antioxidant, pro-inflammatory, angiogenic, and proteotoxic stress responses that culminate in the cancer cell's ability to cope with redox stress and oxidative damage. This review provides an overview of the immediate early stress response in the context of PDT, mechanisms of activation by PDT, and molecular intervention strategies aimed at inhibiting survival signaling and improving PDT outcome.

Inhibition of the HIF-1 Survival Pathway as a Strategy to Augment Photodynamic Therapy Efficacy.

Photodynamic therapy (PDT) is a non-to-minimally invasive treatment modality that utilizes photoactivatable drugs called photosensitizers to disrupt tumors with locally photoproduced reactive oxygen species (ROS). Photosensitizer activation by light results in hyperoxidative stress and subsequent tumor cell death, vascular shutdown and hypoxia, and an antitumor immune response. However, sublethally afflicted tumor cells initiate several survival mechanisms that account for decreased PDT efficacy. The hypoxia inducible factor 1 (HIF-1) pathway is one of the most effective cell survival pathways that contributes to cell recovery from PDT-induced damage. Several hundred target genes of the HIF-1 heterodimeric complex collectively mediate processes that are involved in tumor cell survival directly and indirectly (e.g., vascularization, glucose metabolism, proliferation, and metastasis). The broad spectrum of biological ramifications culminating from the activation of HIF-1 target genes reflects the importance of HIF-1 in the context of therapeutic recalcitrance. This chapter elaborates on the involvement of HIF-1 in cancer biology, the hypoxic response mechanisms, and the role of HIF-1 in PDT. An overview of inhibitors that either directly or indirectly impede HIF-1-mediated survival signaling is provided. The inhibitors may be used as pharmacological adjuvants in combination with PDT to augment therapeutic efficacy.

Attritional evaluation of lipophilic and hydrophilic metallated phthalocyanines for oncological photodynamic therapy.

BACKGROUND AND AIM: Oncological photodynamic therapy (PDT) relies on photosensitizers (PSs) to photo-oxidatively destroy tumor cells. Currently approved PSs yield satisfactory results in superficial and easy-to-access tumors but are less suited for solid cancers in internal organs such as the biliary system and the pancreas. For these malignancies, second-generation PSs such as metallated phthalocyanines are more appropriate. Presently it is not known which of the commonly employed metallated phtahlocyanines, namely aluminum phthalocyanine (AlPC) and zinc phthalocyanine (ZnPC) as well as their tetrasulfonated derivatives AlPCS4 and ZnPCS4, is most cytotoxic to tumor cells. This study therefore employed an attritional approach to ascertain the best metallated phthalocyanine for oncological PDT in a head-to-head comparative analysis and standardized experimental design. METHODS: ZnPC and AlPC were encapsulated in PEGylated liposomes. Analyses were performed in cultured A431 cells as a template for tumor cells with a dysfunctional P53 tumor suppressor gene and EGFR overexpression. First, dark toxicity was assessed as a function of PS concentration using the WST-1 and sulforhodamine B assay. Second, time-dependent uptake and intracellular distribution were determined by flow cytometry and confocal microscopy, respectively, using the intrinsic fluorescence of the PSs. Third, the LC50 values were established for each PS at 671 nm and a radiant exposure of 15 J/cm2 following 1-h PS exposure. Finally, the mode of cell death as a function of post-PDT time and cell cycle arrest at 24 h after PDT were analyzed. RESULTS: In the absence of illumination, AlPC and ZnPC were not toxic to cells up to a 1.5-µM PS concentration and exposure for up to 72 h. Dark toxicity was noted for AlPCS4 at 5 µM and ZnPCS4 at 2.5 µM. Uptake of all PSs was observed as early as 1 min after PS addition to cells and increased in amplitude during a 2-h incubation period. After 60 min, the entire non-nuclear space of the cell was photosensitized, with PS accumulation in multiple subcellular structures, especially in case of AlPC and AlPCS4. PDT of cells photosensitized with ZnPC, AlPC, and AlPCS4 yielded LC50 values of 0.13 µM, 0.04 µM, and 0.81 µM, respectively, 24 h post-PDT (based on sulforhodamine B assay). ZnPCS4 did not induce notable phototoxicity, which was echoed in the mode of cell death and cell cycle arrest data. At 4 h post-PDT, the mode of cell death comprised mainly apoptosis for ZnPC and AlPC, the extent of which was gradually exacerbated in AlPC-photosensitized cells during 8 h. ZnPC-treated cells seemed to recover at 8 h post-PDT compared to 4 h post-PDT, which had been observed before in another cell line. AlPCS4 induced considerable necrosis in addition to apoptosis, whereby most of the cell death had already manifested at 2 h after PDT. During the course of 8 h, necrotic cell death transitioned into mainly late apoptotic cell death. Cell death signaling coincided with a reduction in cells in the G0/G1 phase (ZnPC, AlPC, AlPCS4) and cell cycle arrest in the S-phase (ZnPC, AlPC, AlPCS4) and G2 phase (ZnPC and AlPC). Cell cycle arrest was most profound in cells that had been photosensitized with AlPC and subjected to PDT. CONCLUSIONS: Liposomal AlPC is the most potent PS for oncological PDT, whereas ZnPCS4 was photodynamically inert in A431 cells. AlPC did not induce dark toxicity at PS concentrations of up to 1.5 µM, i.e., > 37 times the LC50 value, which is favorable in terms of clinical phototoxicity issues. AlPC photosensitized multiple intracellular loci, which was associated with extensive, irreversible cell death signaling that is expected to benefit treatment efficacy and possibly immunological long-term tumor control, granted that sufficient AlPC will reach the tumor in vivo. Given the differential pharmacokinetics, intracellular distribution, and cell death dynamics, liposomal AlPC may be combined with AlPCS4 in a PS cocktail to further improve PDT efficacy.

De novo assembled salivary gland transcriptome and expression pattern analyses for Rhipicephalus evertsi evertsi Neuman, 1897 male and female ticks.

Ticks secrete proteins in their saliva that change over the course of feeding to modulate the host inflammation, immune responses, haemostasis or may cause paralysis. RNA next generation sequencing technologies can reveal the complex dynamics of tick salivary glands as generated from various tick life stages and/or males and females. The current study represents 15,115 Illumina sequenced contigs of the salivary gland transcriptome from male and female Rhipicephalus evertsi evertsi ticks of early, mid and late feeding stages from 1320 separate assemblies using three short read assemblers. The housekeeping functional class contributed to the majority of the composition of the transcriptome (80%) but with lower expression (51%), while the secretory protein functional class represented only 14% of the transcriptome but 46% of the total coverage. Six percent had an unknown status contributing 3% of the overall expression in the salivary glands. Platelet aggregation inhibitors, blood clotting inhibitors and immune-modulators orthologous to the ancestral tick lineages were confirmed in the transcriptome and their differential expression during feeding in both genders observed. This transcriptome contributes data of importance to salivary gland biology and blood feeding physiology of non-model organisms.

Argasid and ixodid systematics: Implications for soft tick evolution and systematics, with a new argasid species list.

The systematics of the genera and subgenera within the soft tick family Argasidae is not adequately resolved. Different classification schemes, reflecting diverse schools of scientific thought that elevated or downgraded groups to genera or subgenera, have been proposed. In the most recent classification scheme, Argas and Ornithodoros are paraphyletic and the placement of various subgenera remains uncertain because molecular data are lacking. Thus, reclassification of the Argasidae is required. This will enable an understanding of soft tick systematics within an evolutionary context. This study addressed that knowledge gap using mitochondrial genome and nuclear (18S and 28S ribosomal RNA) sequence data for representatives of the subgenera Alectorobius, Argas, Chiropterargas, Ogadenus, Ornamentum, Ornithodoros, Navis (subgen. nov.), Pavlovskyella, Persicargas, Proknekalia, Reticulinasus and Secretargas, from the Afrotropical, Nearctic and Palearctic regions. Hard tick species (Ixodidae) and a new representative of Nuttalliella namaqua (Nuttalliellidae), were also sequenced with a total of 83 whole mitochondrial genomes, 18S rRNA and 28S rRNA genes generated. The study confirmed the utility of next-generation sequencing to retrieve systematic markers. Paraphyly of Argas and Ornithodoros was resolved by systematic analysis and a new species list is proposed. This corresponds broadly with the morphological cladistic analysis of Klompen and Oliver (1993). Estimation of divergence times using molecular dating allowed dissection of phylogeographic patterns for argasid evolution. The discovery of cryptic species in the subgenera Chiropterargas, Ogadenus and Ornithodoros, suggests that cryptic speciation is common within the Argasidae. Cryptic speciation has implications for past biological studies of soft ticks. These are discussed in particular for the Ornithodoros (Ornithodoros) moubata and Ornithodoros (Ornithodoros) savignyi groups.

Transporter and Lysosomal Mediated (Multi)drug Resistance to Tyrosine Kinase Inhibitors and Potential Strategies to Overcome Resistance.

Tyrosine kinase inhibitors are a class of chemotherapeutic drugs that target specific protein kinases. These tyrosine kinase inhibitors constitute a relatively new class of drugs which target for instance Bcr-Abl, Epidermal Growth Factor Receptor (EGFR) and Vascular Endothelial Growth Factor Receptor (VEGFR). Despite some initial successes, the overall therapeutic benefit of tyrosine kinase inhibitors in the clinic has been mixed. Next to mutations in the target, multidrug resistance is a major obstacle for which still no clinically effective strategies have been developed. Major mechanisms of multidrug resistance are mediated by drug efflux transporter proteins. Moreover, there is accumulating evidence that multidrug resistance can also be caused by lysosomal sequestration of drugs, effectively trapping tyrosine kinase inhibitors and preventing them from reaching their target. Lysosomal drug sequestration seems to work together with ATP-binding cassette transporters, increasing the capacity of lysosomes to mediate sequestration. Both membrane efflux transporter proteins and lysosomes present potential therapeutic targets that could reverse multidrug resistance and increase drug efficacy in combination therapy. This review describes both mechanisms and discusses a number of proposed strategies to circumvent or reverse tyrosine kinase inhibitor-related multidrug resistance.

Integrative taxonomy of Afrotropical Ornithodoros (Ornithodoros) (Acari: Ixodida: Argasidae).

Afrotropical Ornithodoros (Ornithodoros) ticks are revised based on qualitative morphology of females and nymphs, as well as tarsus I shape outlines of females measured in a geometric morphometric framework. These lines of evidence corroborate lineages based on 16S rRNA nucleotide sequence data. Four previously unrecognized species are described, along with a revived nomen nudum that was previously considered a synonym. Afrotropical Ornithodoros (Ornithodoros) now comprise ten species. Ornithodoros moubata and Ornithodoros porcinus are separated from three other species in southern Africa (Ornithodoros compactus, Ornithodoros phacochoerusn. sp., Ornithodoros waterbergensisn. sp.), with O. porcinus restricted to central east Africa. Known species boundaries for Ornithodoros apertus and O. compactus are supported. Ornithodoros savignyi are separated from three other species in South Africa and Namibia, with O. savignyi restricted to north Africa. Neumann's Ornithodoros pavimentosusnom. rev. are resurrected from synonymy as a species that occur in Bushmanland, Namaqualand and Namibia, while Ornithodoros kalahariensisn. sp. occur in Kalahari thornveld, and Ornithodoros noorsveldensisn. sp. occur in Noorsveld thicket of South Africa. Detailed descriptions are given for each species along with high resolution images and point map distributions. Support is provided for speciation driven by riverine barriers, Pliocene uplift and differential arid tolerance. Exaggerated tarsus I shape in the O. savignyi group suggests adaptation to fossorial habits and soil type. Conversely, reduced tarsus I shape in the O. moubata group is suggested as an evolutionary consequence of the life history change from soil to warthog burrows. This study represents an integrative (iterative) approach to delimiting Afrotropical Ornithodoros (Ornithodoros) species, and provides the first application of tarsus I shape outlines in a geometric morphometric framework for testing species boundaries.

Notes on maternal behaviour in soft ticks: Specifically observed in Argas (Argas) striatus Bedford, 1932 and Argas (Secretargas) transgariepinus White, 1846.

Maternal behaviour (carrying of larvae on the opisthosoma) in ticks has thus far only been observed in Antricola (Parantricola) marginatus and was considered a unique derived adaptation of this genus. The authors extend this observation to two additional argasid species, namely Argas (Argas) striatus and Argas (Secretargas) transgariepinus. In addition, brooding behaviour over eggs were observed with A. (S.) transgariepinus. Maternal behaviour may be an evolutionary adaptation to ecological challenges in habitats unsuited for larval survival and may be related to the presence of pulvilli in larvae. This adaptation might have been present in the ancestral tick lineage since pulvilli occur in all tick families, and may have been derived from a more ancient adaptation in chelicerates where maternal behaviour was common. Female A. (S.) transgariepinus also possess a unique area on their ventral abdomen that is absent in males and may be a unique adaptation for maternal behaviour in this species. Phylogenetic analysis of the 16S rRNA genes for both species indicate that they are unique lineages that group basal to other members of the Argas genus, supporting the possibility that they harbour ancestral traits for this group.

DNA methyltransferases expression in normal tissues and various human cancer cell lines, xenografts and tumors.

DNA methylation plays an important role in carcinogenesis and aberrant methylation patterns have been found in many tumors. Methylation is regulated by DNA methyltransferases (DNMT), catalyzing DNA methylation. Therefore inhibition of DNMT is an interesting target for anticancer treatment. RX-3117 (fluorocyclopentenylcytosine) is a novel demethylating antimetabolite that is currently being studied in clinical trials in metastatic bladder and pancreatic cancers. The active nucleotide of RX-3117 is incorporated into DNA leading to downregulation of DNMT1, the maintenance DNA methylation enzyme. Since DNMT1 is a major target for the activity of RX-3117, DNMT1 may be a potential predictive biomarker. Therefore, DNMT1 protein and mRNA expression was investigated in 19 cancer cell lines, 26 human xenografts (hematological, lung, pancreatic, colon, bladder cancer) and 10 colorectal cancer patients. The DNMT1 mRNA expression showed large variation between cell lines (100-fold) and the 26 xenografts (1100-fold) investigated. The DNMT1 protein was overexpressed in colon tumours from patients compared to non-malignant mucosa from the same patients (P = 0.02). The DNA methylation in these patients was significantly higher in tumour tissues compared to normal mucosa (P = 0.001). DNMT1 expression in normal white blood cells also showed a large variation. In conclusion, the large variation in DNMT1 expression may serve as a potential biomarker for demethylating therapy such as with RX-3117.

Sialotranscriptomics of Rhipicephalus zambeziensis reveals intricate expression profiles of secretory proteins and suggests tight temporal transcriptional regulation during blood-feeding.

BACKGROUND: Ticks secrete a diverse mixture of secretory proteins into the host to evade its immune response and facilitate blood-feeding, making secretory proteins attractive targets for the production of recombinant anti-tick vaccines. The largely neglected tick species, Rhipicephalus zambeziensis, is an efficient vector of Theileria parva in southern Africa but its available sequence information is limited. Next generation sequencing has advanced sequence availability for ticks in recent years and has assisted the characterisation of secretory proteins. This study focused on the de novo assembly and annotation of the salivary gland transcriptome of R. zambeziensis and the temporal expression of secretory protein transcripts in female and male ticks, before the onset of feeding and during early and late feeding. RESULTS: The sialotranscriptome of R. zambeziensis yielded 23,631 transcripts from which 13,584 non-redundant proteins were predicted. Eighty-six percent of these contained a predicted start and stop codon and were estimated to be putatively full-length proteins. A fifth (2569) of the predicted proteins were annotated as putative secretory proteins and explained 52% of the expression in the transcriptome. Expression analyses revealed that 2832 transcripts were differentially expressed among feeding time points and 1209 between the tick sexes. The expression analyses further indicated that 57% of the annotated secretory protein transcripts were differentially expressed. Dynamic expression profiles of secretory protein transcripts were observed during feeding of female ticks. Whereby a number of transcripts were upregulated during early feeding, presumably for feeding site establishment and then during late feeding, 52% of these were downregulated, indicating that transcripts were required at specific feeding stages. This suggested that secretory proteins are under stringent transcriptional regulation that fine-tunes their expression in salivary glands during feeding. No open reading frames were predicted for 7947 transcripts. This class represented 17% of the differentially expressed transcripts, suggesting a potential transcriptional regulatory function of long non-coding RNA in tick blood-feeding. CONCLUSIONS: The assembled sialotranscriptome greatly expands the sequence availability of R. zambeziensis, assists in our understanding of the transcription of secretory proteins during blood-feeding and will be a valuable resource for future vaccine candidate selection.

The Cytidine Analog Fluorocyclopentenylcytosine (RX-3117) Is Activated by Uridine-Cytidine Kinase 2.

Fluorocyclopentenylcytosine (RX-3117) is an orally available cytidine analog, currently in Phase I clinical trial. RX-3117 has promising antitumor activity in various human tumor xenografts including gemcitabine resistant tumors. RX-3117 is activated by uridine-cytidine kinase (UCK). Since UCK exists in two forms, UCK1 and UCK2, we investigated which form is responsible for RX-3117 phosphorylation. For that purpose we transfected A549 and SW1573 cell lines with UCK-siRNAs. Transfection of UCK1-siRNA efficiently downregulated UCK1-mRNA, but not UCK2-mRNA expression, and did not affect sensitivity to RX-3117. However, transfection of UCK2-siRNA completely downregulated UCK2-mRNA and protein and protected both A549 and SW1573 against RX-3117. UCK enzyme activity in two panels of tumor cell lines and xenograft cells correlated only with UCK2-mRNA expression (r = 0.803 and 0.915, respectively), but not with UCK1-mRNA. Moreover, accumulation of RX-3117 nucleotides correlated with UCK2 expression. In conclusion, RX-3117 is activated by UCK2 which may be used to select patients potentially sensitive to RX-3117.

An update of the tsetse fly (Diptera: Glossinidae) distribution and African animal trypanosomosis prevalence in north-eastern KwaZulu-Natal, South Africa.

An unpredicted outbreak of African animal trypanosomosis or nagana in 1990 in north-eastern KwaZulu-Natal necessitated an emergency control programme, utilising the extensive cattledipping system in the area, as well as a reassessment of the tsetse and trypanosomosis problem in the province. Since 1990, sporadic blood sampling of cattle at the dip tanks in the naganainfested areas were undertaken to identify trypanosome species involved and to determine the infection prevalence in cattle. The distribution and species composition of the tsetse populations in the area were also investigated. From November 2005 to November 2007 selected dip tanks were surveyed for trypanosome infection prevalence. During April 2005 to August 2009 the distribution and abundance of tsetse populations were assessed with odour-baited H traps. The tsetse and trypanosome distribution maps were updated and potential correlations between tsetse apparent densities (ADs) and the prevalence of trypanosomosis were assessed. Glossina brevipalpis Newstead and Glossina austeni Newstead were recorded in locations where they have not previously been collected. No significant correlation between tsetse relative abundance and nagana prevalence was found, which indicated complex interactions between tsetse fly presence and disease prevalence. This was epitomised by data that indicated that despite large differences in the ADs of G. austeni and G. brevipalpis, trypanosome infection prevalence was similar in all three districts in the area. This study clearly indicated that both tsetse species play significant roles in trypanosome transmission and that it will be essential that any control strategy, which aims at sustainable management of the disease, should target both species.

De novo assembly and annotation of the salivary gland transcriptome of Rhipicephalus appendiculatus male and female ticks during blood feeding.

Tick secretory proteins modulate haemostasis, inflammation and immune responses of the host and are attractive recombinant anti-tick vaccine candidates. Yet, many of the proteins have not been characterised due to the limited sequence availability for ticks and other arthropods for homology-based annotation. To address this limitation, we sequenced the salivary glands of the economically important adult male and female Rhipicephalus appendiculatus ticks during feeding. The quality-filtered Illumina sequencing reads were de novo assembled to generate a R. appendiculatus sialotranscriptome of 21,410 transcripts. A non-redundant set of 12,761 R. appendiculatus proteins was predicted from the transcripts, including 2134 putative secretory and 8237 putative housekeeping proteins. Secretory proteins accounted for most of the expression in the salivary gland transcriptome (63%). Of the secretory protein class, the Glycine-rich superfamily contributed 66% and the Lipocalin family 12% of the transcriptome expression. Differential expression analysis identified 1758 female and 2346 male up-regulated transcripts, suggesting varying blood-feeding mechanisms employed between female and male ticks. The sialotranscriptome assembled in this work, greatly improves on the sequence information available for R. appendiculatus and is a valuable resource for potential future vaccine candidate selection.

Ancestral reconstruction of tick lineages.

Ancestral reconstruction in its fullest sense aims to describe the complete evolutionary history of a lineage. This depends on accurate phylogenies and an understanding of the key characters of each parental lineage. An attempt is made to delineate our current knowledge with regard to the ancestral reconstruction of the tick (Ixodida) lineage. Tick characters may be assigned to Core of Life, Lineages of Life or Edges of Life phenomena depending on how far back these characters may be assigned in the evolutionary Tree of Life. These include housekeeping genes, sub-cellular systems, heme processing (Core of Life), development, moulting, appendages, nervous and organ systems, homeostasis, respiration (Lineages of Life), specific adaptations to a blood-feeding lifestyle, including the complexities of salivary gland secretions and tick-host interactions (Edges of Life). The phylogenetic relationships of lineages, their origins and importance in ancestral reconstruction are discussed. Uncertainties with respect to systematic relationships, ancestral reconstruction and the challenges faced in comparative transcriptomics (next-generation sequencing approaches) are highlighted. While almost 150 years of information regarding tick biology have been assembled, progress in recent years indicates that we are in the infancy of understanding tick evolution. Even so, broad reconstructions can be made with relation to biological features associated with various lineages. Conservation of characters shared with sister and parent lineages are evident, but appreciable differences are present in the tick lineage indicating modification with descent, as expected for Darwinian evolutionary theory. Many of these differences can be related to the hematophagous lifestyle of ticks.

Next-generation sequencing as means to retrieve tick systematic markers, with the focus on Nuttalliella namaqua (Ixodoidea: Nuttalliellidae).

Nuclear ribosomal RNA (18S and 28S rRNA) and mitochondrial genomes are commonly used in tick systematics. The ability to retrieve these markers using next-generation sequencing was investigated using the tick Nuttalliella namaqua. Issues related to nuclear markers may be resolved using this approach, notably, the monotypic status of N. namaqua and its basal relationship to other tick families. Four different Illumina datasets (∼55 million, 100 bp reads each) were generated from a single tick specimen and assembled to give 350k-390k contigs. A genome size of ∼1 Gbp was estimated with low levels of repetitive elements. Contigs (>1000 bp, >50-fold coverage) present in most assemblies (n=69), included host-derived 18S and 28S rRNA, tick and host-derived transposable elements, full-length tick 18S and 28 rRNA, the mitochondrial genome in single contig assemblies and the histone cassette. Coverage for the nuclear rRNA genes was above 1000-fold confirming previous sequencing errors in the 18S rRNA gene, thereby maintaining the monotypic status of this tick. Nuclear markers for the soft tick Argas africolumbae were also retrieved from next-generation data. Phylogenetic analysis of a concatenated 18S-28S rRNA dataset supported the grouping of N. namaqua at the base of the tick tree and the two main tick families in separate clades. This study confirmed the monotypic status of N. namaqua and its basal relationship to other tick families. Next-generation sequencing of genomic material to retrieve high quality nuclear and mitochondrial systematic markers for ticks is viable and may resolve issues around conventional sequencing errors when comparing closely related tick species.

The host preferences of Nuttalliella namaqua (Ixodoidea: Nuttalliellidae): a generalist approach to surviving multiple host-switches.

Nuttalliella namaqua has been described as a "living fossil" and the closest extant species to the ancestral tick lineage. It was previously proposed that the Nuttalliella lineage parasitized reptile-like mammals in the Permian and had to switch hosts several times due to mass or host lineage extinctions. Extant hosts include girdled lizards and murid rodents. The current study extends knowledge on the extant host range of N. namaqua using gut meal analysis of field collected specimens. Nymphs and females can parasitize a variety of reptiles that includes skinks, geckos and girdled lizards. Blood-meal from a hyrax was also detected in a specimen suggesting that N. namaqua could parasitize a broader range of mammals than the previously suggested murid rodents. Rather than being host specific, N. namaqua is proposed to be a generalist and the ability to switch and parasitize multiple hosts allowed it to survive multiple mass and host lineage extinctions.

The mitochondrial genomes of Nuttalliella namaqua (Ixodoidea: Nuttalliellidae) and Argas africolumbae (Ixodoidae: Argasidae): estimation of divergence dates for the major tick lineages and reconstruction of ancestral blood-feeding characters.

Ixodida are composed of hard (Ixodidae), soft (Argasidae) and the monotypic Nuttalliellidae (Nuttalliella namaqua) tick families. Nuclear 18S rRNA analysis suggested that N. namaqua was the closest extant relative to the last common ancestral tick lineage. The mitochondrial genomes of N. namaqua and Argas africolumbae were determined using next generation sequencing and de novo assembly to investigate this further. The latter was included since previous estimates on the divergence times of argasids lacked data for this major genus. Mitochondrial gene order for both was identical to that of the Argasidae and Prostriata. Bayesian analysis of the COI, Cytb, ND1, ND2 and ND4 genes confirmed the monophyly of ticks, the basal position of N. namaqua to the other tick families and the accepted systematic relationships of the other tick genera. Molecular clock estimates were derived for the divergence of the major tick lineages and supported previous estimates on the origins of ticks in the Carboniferous. N. namaqua larvae fed successfully on lizards and mice in a prolonged manner similar to many argasids and all ixodids. Excess blood meal-derived water was secreted via the salivary glands, similar to ixodids. We propose that this prolonged larval feeding style eventually gave rise to the long feeding periods that typify the single larval, nymphal and adult stages of ixodid ticks and the associated secretion of water via the salivary glands. Ancestral reconstruction of characters involved in blood-feeding indicates that most of the characteristics unique to either hard or soft tick families were present in the ancestral tick lineage.