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Dive into the research topics where Lesley Bell-Sakyi is active.

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Featured researches published by Lesley Bell-Sakyi.


Vaccine | 1995

Theileria annulata sporozoite antigen fused to hepatitis B core antigen used in a vaccination trial

Nicky Boulter; Elizabeth Glass; Pamela A. Knight; Lesley Bell-Sakyi; C.G. Duncan Brown; Roger Hall

A C terminal fragment (SR1) of SPAG-1, a sporozoite surface antigen of Theileria annulata, has been expressed as a fusion protein in the e1 loop of hepatitis B core antigen (HBcAg). This recombinant antigen (HBcAg-SR1) is produced in the form of self-assembling polyhedral particles which have been visualised under the electron microscope. Cattle immunised with HBcAg-SR1 produced high titres of neutralising antibodies. A significant T cell response to both the HBcAg and SR1 determinants was observed but evidence of a T suppressor determinant in SR1 was also revealed. Immunised cattle showed some evidence of protection to sporozoite challenge as assessed by severity of the disease. The significance of these findings for the development of a sub-unit vaccine against T. annulata is discussed.


Nucleic Acids Research | 2014

Induction and suppression of tick cell antiviral RNAi responses by tick-borne flaviviruses

Esther Schnettler; Hana Tykalová; Mick Watson; Mayuri Sharma; Mark G. Sterken; Darren J. Obbard; Samuel H. Lewis; Melanie McFarlane; Lesley Bell-Sakyi; Gerald Barry; Sabine Weisheit; Sonja M. Best; Richard J. Kuhn; Gorben P. Pijlman; Margo E. Chase-Topping; Ernest A. Gould; Libor Grubhoffer; John K. Fazakerley; Alain Kohl

Arboviruses are transmitted by distantly related arthropod vectors such as mosquitoes (class Insecta) and ticks (class Arachnida). RNA interference (RNAi) is the major antiviral mechanism in arthropods against arboviruses. Unlike in mosquitoes, tick antiviral RNAi is not understood, although this information is important to compare arbovirus/host interactions in different classes of arbovirus vectos. Using an Ixodes scapularis-derived cell line, key Argonaute proteins involved in RNAi and the response against tick-borne Langat virus (Flaviviridae) replication were identified and phylogenetic relationships characterized. Analysis of small RNAs in infected cells showed the production of virus-derived small interfering RNAs (viRNAs), which are key molecules of the antiviral RNAi response. Importantly, viRNAs were longer (22 nucleotides) than those from other arbovirus vectors and mapped at highest frequency to the termini of the viral genome, as opposed to mosquito-borne flaviviruses. Moreover, tick-borne flaviviruses expressed subgenomic flavivirus RNAs that interfere with tick RNAi. Our results characterize the antiviral RNAi response in tick cells including phylogenetic analysis of genes encoding antiviral proteins, and viral interference with this pathway. This shows important differences in antiviral RNAi between the two major classes of arbovirus vectors, and our data broadens our understanding of arthropod antiviral RNAi.


Research in Veterinary Science | 1992

Tropical theileriosis in Bos taurus and Bos taurus cross Bos indicus calves: response to infection with graded doses of sporozoites of Theileria annulata

Patricia M. Preston; C.G.D. Brown; Lesley Bell-Sakyi; Wendy Richardson; A. Sanderson

This work extends basic knowledge of tropical theileriosis in taurine and crossbred cattle. Infection of Bos taurus and Bos taurus cross Bos indicus (Sahiwal) calves with graded doses of sporozoites of Theileria annulata (Hissar), an Indian stock of the parasite, showed the following to be dose dependent in both cattle types: the time to appearance and population size of macroschizonts, microschizonts and piroplasms, time and severity of pyrexia, anaemia manifested by erythrocyte counts and haematocrit. All infections were accompanied by a prompt and severe panleucopenia. This effect was dose related in both the taurine and the Sahiwal crossbred calves. Lymphocyte counts returned to preinfection levels in the blood of animals which recovered, but death from theileriosis was characteristically accompanied by a persistent and severe lymphocytopenia. Flow cytometry using monoclonal antibodies to bovine mononuclear cells was used to identify the lymphocyte subsets involved in lymphocytopenia. The outcome of infection was dose dependent in the crossbred calves but not in taurine calves. Although the results obtained did not differ qualitatively between the two cattle types, they provided some preliminary evidence for resistance to tropical theileriosis in Sahiwal crossbred calves.


Molecular & Cellular Proteomics | 2015

Integrated Metabolomics, Transcriptomics and Proteomics Identifies Metabolic Pathways Affected by Anaplasma phagocytophilum Infection in Tick Cells

Margarita Villar; Nieves Ayllón; Pilar Alberdi; Andrés Moreno; María Jiménez Moreno; Raquel Tobes; Lourdes Mateos-Hernández; Sabine Weisheit; Lesley Bell-Sakyi; de la Fuente J

Anaplasma phagocytophilum is an emerging zoonotic pathogen that causes human granulocytic anaplasmosis. These intracellular bacteria establish infection by affecting cell function in both the vertebrate host and the tick vector, Ixodes scapularis. Previous studies have characterized the tick transcriptome and proteome in response to A. phagocytophilum infection. However, in the postgenomic era, the integration of omics datasets through a systems biology approach allows network-based analyses to describe the complexity and functionality of biological systems such as host–pathogen interactions and the discovery of new targets for prevention and control of infectious diseases. This study reports the first systems biology integration of metabolomics, transcriptomics, and proteomics data to characterize essential metabolic pathways involved in the tick response to A. phagocytophilum infection. The ISE6 tick cells used in this study constitute a model for hemocytes involved in pathogen infection and immune response. The results showed that infection affected protein processing in endoplasmic reticulum and glucose metabolic pathways in tick cells. These results supported tick–Anaplasma co-evolution by providing new evidence of how tick cells limit pathogen infection, while the pathogen benefits from the tick cell response to establish infection. Additionally, ticks benefit from A. phagocytophilum infection by increasing survival while pathogens guarantee transmission. The results suggested that A. phagocytophilum induces protein misfolding to limit the tick cell response and facilitate infection but requires protein degradation to prevent ER stress and cell apoptosis to survive in infected cells. Additionally, A. phagocytophilum may benefit from the tick cells ability to limit bacterial infection through PEPCK inhibition leading to decreased glucose metabolism, which also results in the inhibition of cell apoptosis that increases infection of tick cells. These results support the use of this experimental approach to systematically identify cell pathways and molecular mechanisms involved in tick–pathogen interactions. Data are available via ProteomeXchange with identifier PXD002181.


Medical and Veterinary Entomology | 2004

Susceptibility of mosquito and tick cell lines to infection with various flaviviruses.

Charles H. Lawrie; N. Y. Uzcategui; M. Armesto; Lesley Bell-Sakyi; Ernest A. Gould

Abstract.  The genus Flavivirus consists of more than 70 virus species and subtypes, the majority of which are transmitted by mosquitoes or ticks, although some have no known vector (NKV). The ability of these viruses to infect cultured cells derived from mosquito or tick species offers a useful insight into the suitability of such vectors to harbour and replicate particular viruses. We undertook a comparative study of the susceptibility of mammalian Vero cells, a clonal mosquito cell line (C6/36) and recently developed cell lines derived from the ticks (Acari: Ixodidae) Ixodes ricinus (L.) (IRE/CTVM18), I.scapularis (Say) (ISE6), Rhipicephalus appendiculatus (Neumann) (RAE/CTVM1) and Amblyomma variegatum (Fabricius) (AVL/CTVM17) to infection with 13 flaviviruses (and one alphavirus) using immunofluorescence microscopy and plaque assay techniques. The C6/36 mosquito cell line was infected by all the mosquito‐borne flaviviruses tested but not by NKV viruses or tick‐borne viruses, with the exception of Langat virus (LGTV). The tick cell lines were susceptible to infection by all of the tick‐borne viruses tested, as well as two mosquito‐borne viruses, West Nile virus (WNV) and the alphavirus, Venezuelan equine encephalitis virus (VEEV), but not other mosquito‐borne viruses or NKV viruses.


Journal of Bacteriology | 2005

Transcription Analysis of the Major Antigenic Protein 1 Multigene Family of Three In Vitro-Cultured Ehrlichia ruminantium Isolates

Cornelis P. J. Bekker; Milagros Postigo; Amar Taoufik; Lesley Bell-Sakyi; Conchita Ferraz; Dominique Martinez; Frans Jongejan

Ehrlichia ruminantium, an obligate intracellular bacterium transmitted by ticks of the genus Amblyomma, causes heartwater disease in ruminants. The gene coding for the major antigenic protein MAP1 is part of a multigene family consisting of a cluster containing 16 paralogs. In the search for differentially regulated genes between E. ruminantium grown in endothelial and tick cell lines that could be used in vaccine development and to determine if differences in the map1 gene cluster exist between different isolates of E. ruminantium, we analyzed the map1 gene cluster of the Senegal and Gardel isolates of E. ruminantium. Both isolates contained the same number of genes, and the same organization as found in the genome sequence of the Welgevonden isolate (H. Van Heerden, N. E. Collins, K. A. Brayton, C. Rademeyer, and B. A. Allsopp, Gene 330:159-168, 2004). However, comparison of two subpopulations of the Gardel isolate maintained in different laboratories demonstrated that recombination between map1-3 and map1-2 had occurred in one subpopulation with deletion of one entire gene. Reverse transcription-PCR on E. ruminantium derived mRNA from infected cells using gene-specific primers revealed that all 16 map1 paralogs were transcribed in endothelial cells. In one vector (Amblyomma variegatum) and several nonvector tick cell lines infected with E. ruminantium, transcripts were found for between 4 and 11 paralogs. In all these cases the transcript for the map1-1 gene was detected and was predominant. Our results indicate that the map1 gene cluster is relatively conserved but can be subject to recombination, and differences in the transcription of map1 multigenes in host and vector cell environments exist.


Veterinary Parasitology | 1998

Immunochemical characterization of in vitro culture-derived antigens of Babesia bovis and Babesia bigemina.

L.M.F. Passos; Lesley Bell-Sakyi; C.G.D. Brown

Cross-reactivity between Babesia bovis and B. bigemina becomes a problem in discrimination of the two infections in endemic areas where the two species usually occur in association. With the aim of identifying candidate proteins for use as specific diagnostic tools, culture-derived components of three geographically different stocks of B. bovis (Lismore, Kwanyanga and Mexico) and one of B. bigemina (Mexico) were analyzed by immunoprecipitation using acrylamide gel electrophoresis. The approach taken was based on the analysis of 35S-methionine-labelled parasite antigens released into culture supernatant. A variety of serum samples were tested, including a panel of calf sera experimentally produced against the different stocks of Babesia, serum samples from cattle naturally infected in the field in Brazil, and a panel of anti-B. bovis monoclonal antibodies, previously characterized by the indirect fluorescent antibody test, ELISA and Western immuno-blotting. Approximately 28 and 23 bands (with molecular weights ranging from 200 to 14 kDa) were detected in total protein profiles of B. bovis and B. bigemina culture supernatants, respectively, whereas no bands were seen in the uninfected red blood cell culture supernatant (negative control). The immunoprecipitation analysis showed antigenic diversity amongst the stocks of B. bovis and resulted in identification of at least five B. bovis specific antigens common to the three stocks (molecular weights of 80, 72, 58, 38 and 24 kDa) and four B. bigemina specific antigens (molecular weights of 240, 112, 50 and 29 kDa).


Gene | 2002

Transcriptional analysis of the major antigenic protein 1 multigene family of Cowdria ruminantium

Cornelis P. J. Bekker; Lesley Bell-Sakyi; Edith Paxton; Dominique Martinez; Albert Bensaïd; Frans Jongejan

The major antigenic protein 1 (MAP1) of the tick-borne rickettsial pathogen Cowdria ruminantium is encoded by a multigene family containing conserved and variable genes. The part of a locus containing the map1 multigene family that was characterized contained three homologous, but non-identical map1 genes, designated map1-2, map1-1, and map1. Reverse transcriptase-polymerase chain reaction was used to study the transcriptional activity of these genes in isolates of C. ruminantium grown in bovine endothelial cells, in two different tick cell lines, and in Amblyomma variegatum ticks. The map1 gene was always transcribed, whereas transcription of map1-2 was not detected under any of the tested conditions. The map1-1 gene transcript was detected in A. variegatum ticks, but was not found in virulent C. ruminantium Senegal grown in bovine endothelial cells at 30 or 37 degrees C. Interestingly, transcripts of map1-1 were also found in different passages of the in vitro attenuated Senegal isolate grown in bovine endothelial cells, as well as in the Gardel isolate grown in two tick cell lines. When transcribed, map1-1 was present on a polycistronic messenger together with map1.


Virus Research | 2008

Growth of tick-borne encephalitis virus (European subtype) in cell lines from vector and non-vector ticks

Daniel Růžek; Lesley Bell-Sakyi; Jan Kopecký; Libor Grubhoffer

We undertook a comparative study of the susceptibility of different tick cell lines to infection with the European subtype of tick-borne encephalitis virus (TBEV), prototype strain Neudoerfl. The growth of TBEV was investigated in lines derived from vector Ixodes ricinus L. ticks (IRE/CTVM18, 19, and 20), as well as non-vector ticks, namely Ixodes scapularis Say (IDE2), Boophilus microplus Canestrini (BME/CTVM2), Hyalomma anatolicum anatolicum Koch (HAE/CTVM9), Rhipicephalus appendiculatus Neumann (RA-257) and recently established and herein described lines from the argasid tick Ornithodoros moubata Murray (OME/CTVM21 and 22). All the tick cell lines tested were susceptible to infection by TBEV and the virus caused productive infection without any cytopathic effect. However, there was a clear difference between the TBEV growth in vector and non-vector cell lines, since I. ricinus cell lines produced 100-1000-fold higher virus yield than the non-vector cell lines. The lowest virus production was observed in O. moubata and R. appendiculatus cell lines.


Parasites & Vectors | 2015

Ixodes scapularis and Ixodes ricinus tick cell lines respond to infection with tick-borne encephalitis virus: transcriptomic and proteomic analysis

Sabine Weisheit; Margarita Villar; Hana Tykalová; Marina Popara; Julia Loecherbach; Mick Watson; Daniel Růžek; Libor Grubhoffer; José de la Fuente; John K. Fazakerley; Lesley Bell-Sakyi

BackgroundIxodid 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.MethodsRNA 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).ResultsDifferential 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.ConclusionsThis 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.

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José de la Fuente

Oklahoma State University–Stillwater

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Pilar Alberdi

Spanish National Research Council

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Nieves Ayllón

Spanish National Research Council

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Margarita Villar

Spanish National Research Council

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Radek Sima

Charles University in Prague

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Edith Paxton

University of Edinburgh

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