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PubMed2002

Amino acid sequence and structure modeling of savignin, a thrombin inhibitor from the tick, Ornithodoros savignyi.

The full-length gene of savignin, a potent thrombin (E.C. 3.4.21.5) inhibitor from the tick Ornithodoros savignyi has been cloned and sequenced. Both 5' and 3' UTR's, a signal peptide from the translated amino acid sequence and an unusual poly-adenylation signal (AATACA) has been identified. The translated protein sequence shows high identity (63%) with ornithodorin, the thrombin inhibitor from the tick, Ornithodoros moubata. Molecular modeling using the structure of ornithodorin as reference gave a structure with an RMSD of 0.25 A for the full-length protein, 0.11 A for the N-terminal BPTI-like domain and 0.11 A for the C-terminal BPTI-like domain, indicating that maximum deviation occurs in the mobile bridge (0.18 A) between the two domains. Docking of savignin to thrombin shows that the interaction is similar to the ornithodorin-thrombin complex. The N-terminal amino acid residues of savignin bind inside the active site cleft, while the C-terminal domain of savignin has a net negative electrostatic potential and interacts with the basic fibrinogen recognition exosite of thrombin through hydrogen bonds and hydrophobic interactions. These results correlate with kinetic data obtained, which showed that savignin is a competitive, slow, tight-binding inhibitor that requires thrombin's fibrinogen-binding exo-site for optimal inhibition.

Amino Acid Sequence↗

PubMed1984

Borrelia crocidurae localization and transmission in Ornithodoros erraticus and O. savignyi.

Borrelia crocidurae infection rates in different organs of adult Ornithodoros (Pavlovskyella) erraticus and O. (Ornithodoros) savignyi were studied at intervals during a 60-day period following an infective meal. The spirochaetes persisted in tick guts for 1 month, were first observed in other organs 1-7 days post-feeding, and persisted for 20-60 days in different organs. The ovaries, Gene's organ, testes and male accessory glands of only O. erraticus were infected. The infection rates in adult and immature O. erraticus and O. savignyi post-feeding on infected hamsters were 26.7-60 X 0% and 26.7-80.0%, respectively. Spirochaete trans-stadial transfer from originally infected larval O. erraticus to first-instar nymphs (N1) was 33.3%; to subsequent N2-N5 it was 40.0-60.0%. Infection rates in the resulting adults were 26.7% (males) and 46.7% (females). In O. savignyi, trans-stadial transfer from originally infected N1 to N2 was 26.7% and to subsequent N3-N7 13.3-33.3%; of the resulting males and females, 20.0% were infected. Transovarial transmission from female O. erraticus infected as adults occurred after the second gonotrophic cycle to 33.3-53.3% of the F1 larvae, and to 26.7 and 46.7% of the F1 males and females, respectively. All infected F1 females transmitted the spirochaetes to 26.7-73.3% of the F2 larval progeny after the first gonotrophic cycle. Transovarial transmission was not observed in O. savignyi.

Animals↗

PubMed1998

Cloning, nucleotide sequence and expression of the gene encoding factor Xa inhibitor from the salivary glands of the tick, Ornithodoros savignyi.

The N-terminal sequence of the competitive and slow tight-binding factor Xa inhibitor (fXaI; Ki = 0.83 +/- 0.10 nM) isolated from the salivary glands of Ornithodoros savignyi ticks (Acari: Argasidae) was employed to design a degenerate gene-specific primer (GSP) for 3'-rapid amplification of cDNA ends (3'-RACE). The primer consisted of a sequence encoding for amino acid residues 5-11. A full-length gene was next constructed from the 3'-RACE product in a two-step PCR procedure and successfully expressed by the BAC-TO-BAC baculovirus expression system. The deduced amino acid sequence of the gene showed 46% identity and 78% homology to an fXaI (TAP) from Ornithodoros moubata. Recombinant fXaI (rfXaI) consists of 60 amino acid residues, has a molecular mass of approximately 7 kDa and inhibited fXa by approximately 91%. The availability of the rfXaI will aid further investigations of its potential for therapeutic applications and as vaccine against tick infestation. The authentic nucleotide sequence of the gene encoding tick fXaI furthermore enables studies at the genetic level and probing of other tick species for similar and related genes.

Amino Acid Sequence↗

PubMed1994

Experimental transmission of Langat (tick-borne encephalitis virus complex) virus by the soft tick Ornithodoros sonrai (Acari: Argasidae).

Laboratory studies determined that the soft tick Ornithodoros sonrai Sautet & Witkowski is a competent vector of Langat (tick-borne encephalitis virus complex) virus. When ticks fed on suckling mice having a mean viremia of 10(7.2) plaque-forming units per ml, 52% (n = 208) became infected, and 84% (n = 87) of the infected ticks transmitted virus by bite when fed individually on suckling mice > or = 27 d after the infectious blood meal. Overall, 79 of 184 (43%) of ticks exposed to the original viremic mice individually transmitted virus by bite when tested up to 351 d after the infectious blood meal. In addition, ticks transmitted virus both transstadially and transovarially. Some ticks that transmitted virus during their first transmission attempt were retested. These ticks transmitted virus during 81 (99%) of 82 refeeding attempts, including ticks that transmitted virus 512 d after the initial infectious meal. Therefore, Ornithodoros spp. should be considered as potential vectors of Langat and other tick-borne encephalitis viruses.

Animals↗

PubMed1975

Soldado virus (Hughes group) from Ornithodoros (Alectorobius) capensis (Ixodoidea: Argasidae) infesting Sooty Tern colonies in the Seychelles, Indian Ocean.

In the summer of 1973, about 5,000 pairs of adult Sooty Terns abandoned a specific part of their breeding grounds on Bird Island in the Seychelles. Incubated eggs and newly hatched chicks were left unattended and the area was not reoccupied in 1974. Numerous Ornithodoros (Alectorobius) capensis occurred in the deserted part in both years, but few or none in the area where bird breeding was normal. Persons visiting the deserted area were bitten by many ticks and experienced severe pruritus persisting for several days. In 1973 and 1974, Soldado (SOL) virus (Hughes serogroup) was isolated from the ticks taken on Bird Island from the ground and from sick and not visibly sick chicks of the Sooty Tern, and also from nests of the Blue-faced Booby on Des Noeufs Island. When ticks from the ground and from Sooty Tern chicks were fed on domestic chicks, they transmitted SOL virus and caused the death of their hosts. Soldado virus was previously known only from O. (A.) capensis-group ticks infesting marine bird colonies on islands off Trinidad and in a lake in Ethiopia. We have also isolated SOL virus from another species of the subgenus Alectorobius from Wales, Great Britain. Marine bird migrations undoubtedly account for the remarkably extensive distribution of SOL virus. The role of migration in the mechanisms and dynamics of tick and virus distribution, and the comparative growth cycles of Hughes serogroup viruses in Ornithodoros ticks, remain to be determined for a better epidemiological understanding of this agent.

Animals↗

PubMedDate not supplied

[The reciprocal influence of Escherichia coli and Salmonella bacteria in a mixed infection of Ornithodoros papillipes Birula ticks].

The paper presents and analyzes the results of experiments on the Escherichia coli-Salmonella relationships in combined infection of Ornithodoros papillipes ticks. The findings have led to the following conclusions. The body of hungry adult O. papillipes ticks can retain the pathogen of Salmonella infection for a month. This model object is also favourable for avirulent E. coli strain persistent in the body's cavity both alone and in combination with Salmonella typhimurium strain in a 1:1 ratio. Binary carriage in hungry Ornithodoros papillipes ticks revealed that the ticks associated with Salmonella typhimurium and E. coli 083 mcl + lyz No 225, microcine and lysozyme producers, are freed of pathogenic bacteria during 24 hours. The initial bacteria E. coli 083 mcl also suppress salmonellae; however, their elimination occurs much later--in 5 days. Calculating the correlation between the pairs (S. typhi and E. coli) has revealed a linear functional relationship of the rate of E. coli growth to S. typhimurium suppression.

Animals↗

PubMed1976

Protease activity in female Ornithodoros tholozani ticks.

The protease activity in guts of Ornithodoros tholozani females was studied in vitro. The intracellular protease in Ornithodoros tholozani guts has a pH optimum of about 3.0. Hemoglobin is the preferred substrate, and bovine serum albumin is digested very slowly. In this respect the protease resembles cathepsin D. Unfed ticks contain a small amount of protease in the gut. After feeding the level of protease increases gradually for several days until peak protease activity is attained. The level of gut protease activity depends on the size of the blood meal taken and on the interval after feeding. After a period of peak protease activity, the level of protease declines. The level of gut protease in unmated females (kept at 27 degrees C) did not reach prefeeding levels within 100 days. The level of gut proteolytic activity, as determined by in vitro protease assays, does not reflect the degree of blood digestion which takes place in vivo. After a period of rapid digestion, lasting for about two weeks, the undigested part of the blood meal remains unchanged in the lumen of the gut. At that time the gut tissue contains considerable levels of protease, which can be demonstrated by in vitro assays. Presumably, the protease remains active inside the gut cells, although the uptake of hemoglobin from the gut lumen has ceased. The results are compared to those obtained in other tick species.

Animals↗

PubMed2026

Transcriptomic and Metabolomic Profiling Identifies a Core Gene-Metabolite Axis Driving African Swine Fever Virus Replication in the Soft Tick Ornithodoros lahorensis.

African swine fever virus (ASFV) causes an incurable swine disease with nearly 100% mortality, posing a catastrophic threat to global pig production. The soft tick Ornithodoros lahorensis acts as a critical biological vector that sustains persistent ASFV replication and mediates long-distance viral transmission, yet the molecular mechanisms governing ASFV-tick interplay remain poorly understood. Here, we integrated transcriptomics and metabolomics to systematically dissect molecular changes in O. lahorensis across three infection stages: Uninfected control, early infection (7 days post-infection, dpi), and late persistent infection (21 dpi). Multi-omics integration revealed that ASFV extensively remodels tick host metabolism, predominantly activating purine/pyrimidine metabolism, lipid biosynthesis, and energy metabolism. We further characterized a conserved regulatory module consisting of 12 core genes and 8 signature metabolites that collectively support ASFV genome replication and virion assembly. Three hub metabolic genes (TK1, ATP5F1B, and IMPDH) were selected for functional validation via siRNA silencing in ticks; individual gene silencing suppressed ASFV loads by 89.2%, 91.5%, and 87.8%, respectively (p < 0.001***). This work represents the first comprehensive multi-omics investigation of ASFV infection in O. lahorensis. We identified tick-specific molecular targets to block vector-mediated ASFV spread and established a standardized multi-omics analytical pipeline for tick-virus interaction research. Our findings elucidate the mechanistic basis of long-term ASFV persistence in soft ticks and deliver novel actionable clues for developing vector-targeted ASF intervention strategies.

Animals↗

PubMed2002

Existence of phenol oxidase in the argasid tick Ornithodoros moubata.

Phenol oxidase (PO, EC 1.10.3.1) activity was detected in the hemolymph of the fourth instar nymphs of the argasid tick, Ornithodoros moubata, with peak levels corresponding to the days before the majority of the nymphs had molted, suggestive of a protective role of PO during the ecdysial phase. Higher PO activity was detected in plasma relative to the hemolymph and was negligible in hemocytes. The concentration of the hemolymph and plasma assayed clearly influenced the level of PO activity, and was significantly reduced ( P<0.005) after treatment with 1-phenyl-2 thiourea, a specific PO inhibitor. This is the first report of the existence of PO in the hemolymph and plasma of a soft tick species. The regulation of PO activity and its precise role in soft tick immunity, particularly during the ecdysial phase, are interesting and need to be examined further.

Animals↗

PubMed2005

Development of a nested PCR and its internal control for the detection of African swine fever virus (ASFV) in Ornithodoros erraticus.

A nested PCR assay, with an internal control, was developed to detect African swine fever virus (ASFV) DNA in Ornithodoros erraticus. The assay revealed a better analytical sensitivity than virus isolation and the OIE PCR protocol. All ticks collected from the field, which were positive by virus isolation, were also positive by PCR. Viral DNA was detected in a further 19 out of 60 ticks from which no virus was isolated. Our results show that this assay is reliable and can easily be used to screen large tick populations collected in the field for the presence of ASFV.

African Swine Fever↗

PubMed2005

Ontogeny of tick hemocytes: a comparative analysis of Ixodes ricinus and Ornithodoros moubata.

Hemocytes of two tick species, Ixodes ricinus and Ornithodoros moubata, were investigated with the aim to determine their ultrastructural characteristics and developmental relationships. Only a limited number of ultrastructural features was shown to be unequivocally homological across all hemocyte types. The two species, representing distant groups of ticks, differ in the composition of their circular cell populations. In I. ricinus, three groups of distinct morphological types of hemocytes could be determined according to well-defined ultrastructural features: a typical non-phagocytic granular cell with electron-dense granula and homogeneous cytoplasm (Gr II), and two different types of phagocytic hemocytes, namely plasmatocytes with a low number of granula and phagocytic granolocytes, designated as Gr I. In contrast, an additional cell type resembling insect spherulocytes was determined in O. moubata. This cell type does not seem to be homologous to any I. ricinus hemocyte and may represent a cell type typical of soft ticks only. Possible ontogenetic lineages of the hemocytes of both tick-species were inferred.

Animals↗

PubMed2006

Larval feeding performance of two Neotropical Ornithodoros ticks (Acari: Argasidae) on reptiles.

This paper determines the feeding performance of the larvae of two Neotropical soft tick species namely Ornithodoros rostratus Aragão, 1911 and O. puertoricensis Fox, 1947 on reptiles (Gekkonidae) using rabbits, mice and guinea pigs to provide comparisons with feeding features on mammals. O. puertoricensis produced a larval feeding rate of 63% on reptiles, while that of O. rostratus was only 20%. But the final success (attaching + feeding) was similar, 12.4% for O. puertoricensis and 10.4% for O. rostratus. The feeding time was also very different for both species. In O. puertoricensis, detachment begins at 16th day and lasts until day 27. In O. rostratus detachment begins at 1.5 h and lasts until day 10. These values of feeding on reptiles are different from those obtained on mammals (average 5.6 days for O. puertoricensis and 2.9 for O. rostratus).

Animals↗

PubMedDate not supplied

Fate of GFP-expressing Escherichia coli in the midgut and response to ingestion in a tick, Ornithodoros moubata (Acari: Argasidae).

Ticks are well-known vectors of various pathogens but migration of the pathogens in the tick midgut is not fully understood. In the present study, the fate of microbes in the midgut of Ornithodoros moubata was observed using green fluorescent protein (GFP)-expressing Escherichia coli. Fluctuations in the percentage of hemocytes in the hemolymph (Hc) and expression of an antimicrobial peptide, defensin, in the midgut was also investigated. Most E. coli gradually disappeared in the midgut after ingestion fluctuations in Hc coincided with the changes. Expression of defensin was also confirmed and slightly up-regulated after E. coli ingestion. Moreover, it was demonstrated that E. coli can not pass through the tick midgut epithelium after ingestion by the hemolymph cultures. It is known that various pathogens and host immunoglobulins ingested with a blood meal can enter into the hemocoel, which suggests the presence of unique and complex passage mechanisms for each molecule and organism. The results obtained here help to clarify that digestion enzymes is an important function of the tick midgut to protect against invading molecules and organisms.

Animals↗

PubMed2005

Molecular cloning and comparative analysis of fibrinogen-related proteins from the soft tick Ornithodoros moubata and the hard tick Ixodes ricinus.

Among disease-vectors, the evolution of the tick innate immune system is still lagging when compared to insects. Such an investigation, which was initiated, by first cloning and sequencing lectins associated in the innate immunity of invertebrates and having fibrinogen related domains, helped in the sequencing of cDNA encoding for OMFREP from the soft tick, Ornithodoros moubata. Also obtained were Ixoderin A and Ixoderin B cDNA sequences from the hard tick Ixodes ricinus. Tissue-specific expression of OMFREP showed that it was present primarily in the hemocytes and salivary glands. Ixoderin A besides sharing a similar expression profile was also expressed in the midgut. Both showed significantly high homology to the lectin Dorin M, from O. moubata. Further, phylogenetic comparisons between these molecules of the soft and hard ticks showed their relatedness to Tachylectins 5A and 5B, involved in the innate immunity of Tachypleus tridentatus and ficolins from both vertebrates and invertebrates. Ixoderin B showing tissue-specific expression only in the salivary glands and the sequence displaying certain motif differences in homology point towards a possible function different from the other two molecules. This is the first report of lectin-like sequences, with a fibrinogen-domain, from the hard tick I. ricinus and a preliminary phylogenetic study of these tick sequences with related fibrinogen-domain containing sequences highlights a possible role for them in the innate immunity of the ticks.

Amino Acid Sequence↗

PubMed2006

A comparison of Chryseobacterium indologenes pathogenicity to the soft tick Ornithodoros moubata and hard tick Ixodes ricinus.

A yellow-pigmented Gram-negative bacterium, Chryseobacterium indologenes, was found in the gut contents of about 65% of soft ticks Ornithodoros moubata from a perishing laboratory colony. The isolated putative pathogen, C. indologenes, was susceptible to cotrimoxazol and addition of this antibiotic (Biseptol 480) to the blood meal significantly decreased the tick mortality rate. The artificial infection of healthy O. moubata by membrane feeding on blood contaminated with C. indologenes was lethal to all ticks at concentrations 10(6) bacteria/ml. On the contrary, a similar infection dose applied to the hard tick Ixodes ricinus by capillary feeding did not cause significant mortality. Examination of guts dissected from infected O. moubata and I. ricinus revealed that C. indologenes was exponentially multiplied in the soft tick but were completely cleared from the gut of the hard ticks within 1 day. In both tick species, C. indologenes were found to penetrate from the gut into the hemocoel. The phagocytic activity of hemocytes from both tick species was tested by intrahaemocoelic microinjection of C. indologenes and evaluated by indirect fluorescent microscopy using antibodies raised against whole bacteria. Hemocytes from both tick species displayed significant phagocytic activity against C. indologenes. All O. moubata injected with C. indologenes died within 3 days, whereas the increase of the mortality rate of I. ricinus was insignificant. Our results indicate that hard ticks possess much more efficient defense system against infection with C. indologenes than the soft ticks. Thus, C. indologenes infection has the potential to be a relevant comparative model for the study of tick immune reactions to transmitted pathogens.

Animals↗

PubMed2006

Molecular divergences of the Ornithodoros sonrai soft tick species, a vector of human relapsing fever in West Africa.

The soft tick Ornithodoros sonrai is recognized as the only vector of Borrelia crocidurae causing human relapsing fever in West Africa. Its determination has been exclusively based on morphological features, geographical distribution and vector competence. Some ambiguities persist in its systematics and may cause misunderstanding about West African human relapsing fevers epidemiology. By amplifying and aligning 16S and 18S rDNA genes in O. sonrai specimens collected from 14 distinct sites in Senegal and Mauritania, we showed the existence of four genetically different subgroups that were morphologically and ecologically identified as belonging to the same species. Within O. sonrai, intraspecific polymorphism was high (pairwise divergence from 0.2% to 16.4%). In all cases, these four subgroups formed a monophyletic clade sharing a common ancestor with East African soft ticks that transmit Borrelia duttoni human relapsing fever. From amplification of the flagellin gene of B. crocidurae we verified that all subgroups of O. sonrai were infected by B. crocidurae and may constitute vectors for this pathogen. All flagellin sequences were identical, refuting the hypothesis suggesting parallel evolution between O. sonrai and B. crocidurae. However, differences in infection rates were significant, suggesting different vector competences between subgroups of O. sonrai.

Africa, Western↗

PubMed2006

Identification of the etiologic agent of epizootic bovine abortion in field-collected Ornithodoros coriaceus Koch ticks.

Epizootic bovine abortion (EBA), or foothill abortion as it has often been termed, is a tick-borne disease of pregnant cattle recognized in California, Nevada and Oregon. The primary objective of this study was to better define the relationship of a novel deltaproteobacterium, the putative etiological agent of EBA (aoEBA), with the Pajaroello tick (Ornithodoros coriaceus Koch), the recognized vector of EBA. Three developmental stages of O. coriaceus (larva, nymph, and adult) were collected from five locations in California, Nevada and Oregon. A polymerase chain reaction (PCR), developed for detection of aoEBA, was applied to DNA extracted from ticks. Southern blotting of the PCR products increased the number of ticks determined to be carrying the bacteria by seven-fold, suggesting the majority of infected ticks carry relatively low numbers of the pathogen. An effort was made to determine if an artificial blood meal would stimulate replication of the bacterial pathogen, thereby increasing the frequency in which aoEBA could be identified; no statistically significant effect was evident. The number of ticks determined to be carrying aoEBA varied with geographic location and ranged from 5 to 20%. aoEBA was found in both adults (12% of the males and 12% of the females) and nymphs (13%) but not larvae. Comparative analysis of dissected ticks provided strong evidence that the salivary gland was the most common location of aoEBA in field-collected ticks. No significant correlations were identified between the frequency of infection and tick weight, suggesting that increasing tick age and increased number of blood meals did not increase infectivity.

Abortion, Veterinary↗

PubMed2003

Development, characterization, and lethal effect of monoclonal antibodies against hemocytes in an adult female tick, Ornithodoros moubata (Acari: Argasidae).

In the present study, 19 monoclonal antibodies (mAbs) against adult Ornithodoros moubata hemocytes were established, and the reactivity of the hemocytes to these mAbs was examined by an indirect fluorescent antibody test (IFAT), Western blot and immunoprecipitation analyses. It was shown that the reactivities of the hemocytes to the mAbs varied among morphologically similar hemocyte types, and most mAbs produced in the present study showed the multiple band reactivity. However, the presence of shared epitopes among peptide subunits of the same protein or entirely different proteins are not common, so their reactivity could not be explained in detail. These results suggest that there are morphologically similar but functionally differentiated hemocytes. Therefore, in addition to morphological classification, the molecular-based classification of the hemocytes is also required. In order to assess the lethal effect of blood meal containing each mAb, artificial feeding was performed. The OmHC 31 showed the strongest lethal effect on adult female O. moubata. In conclusion, anti-hemocyte mAbs produced in this study are useful not only for the immunological classification of hemocytes but also for the immunological control of the tick.

Animals↗