Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.

No description available.

No description available.

Theileria parva is a tick-borne intracellular protozoan parasite which infects cattle and African buffalo in Eastern and Southern Africa. Cattle may be immunised against T. parva by the infection and treatment method (ITM), which involves inoculation with live sporozoites and simultaneous treatment with oxytetracycline. One such ITM vaccine is the Muguga Cocktail, which is composed of a mixture of three parasite stocks: Muguga, Serengeti-transformed and Kiambu 5. Although the vaccine has been used with success in the field in several areas in Eastern Africa, there is evidence that vaccination using cattle-derived parasites does not always provide adequate protection against buffalo-derived T. parva. A number of T. parva antigens recognised by CD8+ T cells from cattle immunised by ITM have been identified in previous studies. A proportion of these antigens show a high degree of sequence polymorphism and allelic diversity is believed to be much greater in buffalo-derived T. parva than in cattle-derived parasites. The present study focussed on the development and application of a deep sequencing technique for characterising genotypically heterogeneous T. parva DNA samples. A panel of genes encoding CD8+ T cell antigens was used as the basis of a multi-locus sequence typing system (MLST) built upon Roche 454 amplicon sequencing technology. This system was validated using parasite stocks of known composition and then utilised to investigate genetic and antigenic diversity in vaccine stabilates and samples derived from African buffalo. The MLST profile obtained for the Muguga Cocktail stocks was compared to those of African buffalo in two geographically separated sites and was also compared with micro/mini-satellite DNA profiles of Muguga Cocktail stocks. The three components of the T. parva Muguga Cocktail vaccine were found to have limited genotypic and antigenic diversity using both methods. The composition of vaccine batches produced in a single production run (ILRI0801-ILRI0804) was shown to be relatively consistent. In contrast, the composition of the component stocks was shown to alter following passage through cattle and ticks. The deep multi-locus sequence profile and satellite DNA profile established in this study may be used as a reference for comparison with future vaccine batches. It is suggested that formulation of a new cocktail vaccine containing three parasite clones selected on the basis of genotypic and antigenic divergence may well provide protection comparable to that obtained with the Muguga Cocktail. The components of such a vaccine could readily be distinguished and the composition of vaccine batches monitored, thus allowing improved quality control and greater consistency of the vaccine. Genetic and antigenic diversity was found to be very high in parasite populations from African buffalo from the Kruger National Park, South Africa and the Ol Pejeta conservancy, Kenya. The estimated average genetic ‘distance’ between any two alleles in the Kruger National Park and within the Ol Pejeta conservancy was very similar for all six genes investigated. Many of the identified alleles were ‘private’ to either the buffalo from Ol Pejeta or the Kruger National Park and many of these alleles were present in several individuals in one location. Principal co-ordinate analysis and phylogenetic investigation of several antigen-encoding loci indicated that extant buffalo parasite populations are geographically sub-structured although some of the underlying diversity may reflect ‘ancient’ polymorphism in an ancestral population. A subset of the CD8+ T cell antigens examined exhibited extensive antigenic polymorphism while others were highly conserved at the amino acid level. These conserved genes may represent good candidates for the development of next generation vaccines, as strain specificity may be overcome if protective CD8+ T cell responses could be generated against these conserved antigens. This would enable the use of sub-unit vaccines in areas where cattle co-graze with buffalo. Theileria sp (buffalo) was identified in cell lines isolated from cattle, indicating that this parasite can transform bovine lymphocytes and may therefore be implicated in pathology in cattle. Phylogenetic analysis of T. parva and T. sp (buffalo) clones using the 5S subunit ribosomal RNA gene, Tp6, Tp7 and Tp8 showed a clear distinction between the two parasite species. These genes could thus be considered as candidates for an improved diagnostic test for T. parva in South Africa.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. / The aim of this thesis was to develop DNA probes to distinguish between the protozoan parasites Theileria parva parva and T. p. lawrencei which cause East Coast fever (ECF) and Corridor disease respectively. ECF was eradicated from South Arrlca in 1954, and today Corridor disease has become the most important form of theileriosis. Although ECF has been eradicated, the vector ticks are still prevalent in South Africa and the cattle population would be highly susceptible to a recurrence of the disease, At present there is no reliable means of distinguishing between T.p. parva and T. p. lawrencei. Sequence differences between T. parva and other Theileria species have previously been found in the small subunit ribosomal RNA (rRNA) gene; probes designed to detect these sequence differences Can be used to distinguish between Theileria species. We therefore decided to search for differences in the rRNA genes of T. p. parva and T.p. lawrencei. To this end, the entire "RNA transcription unit was amplified from a cloned T. p, lawrence; parasite; the unit comprises the small subunit rRNA (SSUrRNA) gene, the internal transcribed spacer (ITS) and the large subunit rRNA (LSUrRNA) gene. The amplification products were cloned and sequenced, and the T.p, lawrencei rRNA sequence was compared to that of T. p, parva, While there was little variation in their SSUrRNA and LSUrRNA gene sequences, there was major sequence variation in the ITS The ITSs from twelve T. parva isolates were amplified, cloned and sequenced, and eleven characterisation oligonucleotide probes were identified. The T. p, parva isolates screened in this study hybridised with a limited subset of the probes, While the T. p. lawrencei isolates, hybridised with many more of the probes, indicating that the T. parva population in cattle is more homogenous than that in buffalo. There thus appears to have been a selection in cattle of a relatively homogenous subpopuiation of T. parva from a much larger, more diverse gene pool in buffalo. Although most T.p. parva isolates (93.5%) were detected by probe TPPI, and most T.p, lawrencei isolates (81.8%) were detected by / AC2017

Tropical Theileriosis is a parasitic disease of calves with a profound economic impact caused by Theileria annulata, an apicomplexan parasite of the genus Theileria. Transmitted by Hyalomma ticks, T. annulata infects and transforms bovine lymphocytes and macrophages into a cancer-like phenotype characterized by all six hallmarks of cancer. In the current study we investigate the transcriptional landscape of T. annulata-infected lymphocytes to define genes and miRNAs regulated by host cell transformation using next generation sequencing. We also define genes and miRNAs differentially expressed as a result of the attenuation of a T.annulata-infected macrophage cell line used as a vaccine. By comparing the transcriptional landscape of one attenuated and two transformed cell lines we identify four genes that we propose as key factors in transformation and virulence of the T. annulata host cells. We also identify miR- 126-5p as a key regulator of infected cells proliferation, adhesion, survival and invasiveness. In addition to the host cell trascriptome we studied T. annulata transcriptome and identified the role of ROS and TGF-β2 in controlling parasite gene expression. Moreover, we have used the deep parasite ssRNA-seq data to refine the available T. annulata annotation. Taken together, this study provides the full list of host cell’s genes and miRNAs transcriptionally perturbed after infection with T. annulata and after attenuation and describes genes and miRNAs never identified before as players in this type of host cell transformation. Moreover, this study provides the first database for the transcriptome of T. annulata and its host cells using next generation sequencing.

This thesis takes data from the Infectious Diseases of East African Livestock (IDEAL) project. The project was a longitudinal calf cohort study based in Western Kenya. Indigenous short horn zebu calves were recruited at birth and then visited every 5 weeks through their first year of life. The aim of this thesis was to improve understanding of the epidemiology of Theileria parva, with a particular focus on variation in host response. 362 of the 548 calves in the study cohort were classified as having seroconverted to T. parva, and 381 to T. mutans before 1 year old. The diagnostic tools used to identify exposure in the calf were compared, and environmental and calf level risk factors associated with the age at seroconversion were sought. Decreased elevation of the homestead and increased size of the herd were found to be significantly associated with an increased hazard of seroconversion to T. parva. There was little variation in hazard of T. mutans captured across the study site. The outcome ‘clinical episode’ was used to classify whether the calf was ill at each routine visit. A large number of calves passed through their first year of life without clinical disease being observed, and a minority of calves experienced the majority of clinical episodes. Multiple clinical episodes were apparently related in time, suggesting that they were due either to the same or connected pathogenic processes. A low birth weight, larger herds, and older farmers were all risk factors for being a sick calf. Both high helminth burden and T. parva were found to be significantly associated with clinical disease at a population level. A lot of variation was seen in the clinical presentation of disease. The clinical signs associated with fatal East Coast Fever (ECF), the clinical disease associated with T. parva infection, were found to be very variable. Although this may have been partly due to the varying times in the disease process that calves were observed prior to death, the complication of the clinical picture was also suggested to be due to co-infections. 71% of the cohort was infected with T. parva in their first year of life, but only a fraction (8.7%) went on to die from that infection. Unmatched and matched nested case control study formats were used to investigate the risk factors associated with death following T. parva infection (ECF death) in these calves. It was found that being infected young was a risk factor for death. Calves owned by older farmers were also at higher risk of death following infection. Going out grazing was found to be protective, and equivocal evidence was found for an association between prior T. mutans exposure and reduced odds of ECF death. If these initial findings from this work are correct, it is likely that T. mutans is influencing the clinical presentation of T. parva in endemic regions.

In South Africa, the diagnosis of Theileria parva in cattle and buffalo has been complicated by the presence of mildly pathogenic and non-pathogenic Theileria spp. This can lead to inaccurate diagnostic results and confuse the epidemiology of theileriosis. The aims of this study were to identify and characterize the 18S rRNA genes of novel Theileria spp. of the African buffalo, as well as to test new gene targets that will allow for the development of more accurate diagnostic tests for the identification of T. parvainfections in cattle and buffalo. Buffalo blood samples originating from different geographical regions in South Africa and from Mozambique were screened for the presence of Theileria spp. by the reverse line blot (RLB) hybridization assay. A total of six Theileria spp., namely T. parva, Theileria sp. (buffalo), Theileria mutans, Theileria velifera and Theileria buffeli, were identified from the buffalo samples. These occurred mainly as mixed infections. Some of the samples hybridized only with the Theileria/Babesia genus specific probe that is used in the RLB assay, and not with any of the species-specific probes used, suggesting the presence of novel genotypes or species. The full-length 18S rRNA genes of parasites from selected samples were characterized by cloning and sequencing. In addition to the identification of 18S rRNA gene sequences that were similar to published Theileria spp. of cattle and buffalo, we identified Theileria sp. (bougasvlei), and novel 18S rRNA gene variants of T. mutans, T. velifera, T. bufJeli. This variation explained why the RLB hybridization assay failed to detect these species in some of the analysed samples. As extensive variation was observed within the T. mutan group, specific RLB oligonucleotide probes were designed from the V 4 hypervariable region of the T. mutans-like 1 and 2/3 18S rRNA gene sequences. Unfortunately these cross-hybridized with T. mutans target DNA and could not be used to screen buffalo samples to determine the occurrence of these genotypes in buffalo in South Africa. This problem could be solved by designing probes from a more variable area of the 18S rRNA gene of the T. mutans groups. Alternatively, a quantitative real-time PCR (qPCR) assay could be used for differentiation of these genotypes as it is more sensitive than the RLB assay. Despite the variation observed in the full-length T parva 18S rRNA gene sequences, the area in the V 4 hypervariable region where the T parva RLB and real-time PCR hybridization probes were developed was relatively conserved between sequences obtained in this study. The existing T parva-specific qPCR assay was able to successfully detect all T parva variants identified in this study and, although amplicons were obtained from Theileria sp. (buffalo) and Theileria sp. (bougasvlei) DNA, these species were not detected by the T parva-specific hybridization probes. The sequences of the other Theileria spp. and the novel genotypes identified in this study under the probes were also different from that of T parva and therefore these species do not compromise the specificity of the T parva 18S qPCR assay. In order to determine the sequence variation and phylogenetic positions of T buffeli spp. of the African buffalo, we cloned and sequenced their 18S rRNA gene and complete internal transcribed spacer (ITS). We identified novel T buffeli-like and T sinensis-like 18S rRNA and ITS genotypes from buffalo originating from two different geographical regions in South Africa. There was extensive sequence variation between these novel South African genotypes and known T buffeli-like and T sinensis-like genotypes. The presence of organisms with T buffeli-like and T. sinensis-like genotypes in the African buffalo is of significant importance, particularly to the cattle industry in South Africa as these animals might act as sources of infections to naIve cattle. Recently, a qPCR assay based on the cox III gene was developed for the diagnosis of Theileria spp. in cattle. This test detects and differentiates six Theileria spp. in cattle. We evaluated the use of this assay for the detection of Theileria spp. in buffalo. The results of the cox III qPCR were compared to those of the RLB and 18S qPCR for the simultaneous detection and differentiation of Theileria spp. of the African buffalo, and for the specific detection of T parva, respectively. The cox III genes from selected samples with non-specific melting peaks were characterized by cloning and sequencing. Extensive sequence variation in the cox III gene was observed between and within species. The T mutans group was the most variable. The qPCR assay could be further improved by designing new primers and probes using all known cox III gene sequences of Theileria spp. Of buffalo and cattle. This study highlights the complexity of the diagnosis of T parva in cattle and buffalo in South Africa. It provides invaluable information towards the development of an improved molecular diagnostic assay for T parva and co-infecting species in cattle and buffalo in South Africa which will assist the veterinary regulatory authorities in the control of Corridor disease in South Africa. / Thesis (PhD)--University of Pretoria, 2011. / Veterinary Tropical Diseases / Unrestricted

The aim of this study was to improve the official diagnostic test package in South Africa for detection of Theileria parva infections in cattle and Cape buffalo (Syncerus caffer) and to investigate the presence of cattle-type T. parva parasites in buffalo and cattle in South Africa. To improve diagnosis of T. parva infections, a T. parva-specific real-time polymerase chain reaction (PCR) assay based on hybridization probe technology was developed. Oligonucleotide primers and hybridization probes used in the assay were designed based on the 18S ribosomal RNA (rRNA) gene. The primers amplify T. parva and Theileria sp. (buffalo) DNA but the hybridization probes specifically detect T. parva amplicons. Because of the high sequence similarity between the T. parva and Theileria sp. (buffalo) 18S rRNA genes, amplification of Theileria sp. (buffalo) DNA could not be avoided; no other bovine blood pathogens tested were amplified by these primers. The real-time PCR assay demonstrated superior sensitivity compared to other molecular tests used in detection of T. parva infections, reliably detecting the parasite in carrier animals with a piroplasm parasitaemia as low as 8.79x10-4% with minute template DNA input. The assay requires less time to perform with a low risk of contamination because of the closed-tube system that does not require handling of amplicons for post-PCR analysis. The presence of cattle-typeT. parva parasites in buffalo and cattle was investigated using restriction fragment length polymorphism (RFLP) profiles of PCR products and sequences of the parasite genes which code for the antigenic proteins p67, p104, and the polymorphic immunodominant molecule (PIM). Cattle-type p67, p104 and PIM alleles were identified from three T. parva samples obtained from cattle from a farm near Ladysmith in the KwaZulu-Natal Province. These cattle-type alleles were identical to those previously identified from a cattle-derived T. parva stock, T. parva Muguga, a parasite stock that causes East Coast fever (ECF) in Kenya; however, ECF was not diagnosed in animals in this farm. Cattle-type alleles identical to those previously reported were not identified from T. parva buffalo samples, but variants of p67 allele 1 as well as p104 allele 1, both previously obtained from T. parva Muguga, were identified. It is not known if parasites that possess these variants can cause disease, and the risk of their adapting to cattle as in the case of ECF and January disease needs to be evaluated. Furthermore, these findings suggest that cattle-like alleles may not be exclusively associated with cattle-derived T. parva parasites. Most of the p67, p104 and PIM gene sequences obtained in this study were not identical to known sequences; furthermore, novel alleles were identified, demonstrating extensive genetic diversity in the South African T. parva parasite population in buffalo. The significance of the parasites that possess ‘novel’ alleles in the epidemiology of theileriosis in South Africa still needs to be determined. The identification of variants and novel alleles reveals that p67, p104 and PIM gene PCR-RFLP profiles are more complex than previously thought and the classification of buffalo- and cattle-derived T. parva parasites in South Africa based on p67, p104 and PIM gene profiles would not be possible. Identification of more reliable markers that can be directly associated with the theilerial disease syndromes remains a challenge. / Thesis (PhD)--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted

Les parasites Theileria (Theileria. annulata and T. parva) sont des protozoaires intracellulaires qui font partie du phylum des Apicomplexa. Theileria infecte les leucocytes bovins et les transforment en cellules cancéreuses, induisant un genre de leucémie chez le bovin et conduisant à la mort de l’animal. Les cellules infectées par Theileria démontrent certaines caractéristiques de cellules cancéreuses telles qu’une importante capacité d’invasion et de migration cellulaire. Cependant, le traitement de cellules infectées avec une drogue Theiléricide spécifique (buparvaquone) permet l'élimination du parasite et la réversion du phénotype transformé. De plus, la virulence peut être atténuée par passages répétés sur culture cellulaire. La similitude entre les cellules transformées par Theileria et la leucémie humaine fait de Theileria un modèle très important permettant l’étude des mécanismes cellulaires induits par le parasite au cours de la transformation de la cellule hôte. Mon laboratoire d’accueil a publié une augmentation significative de TGF-β2 dans les cellules virulentes et a constaté que parmi les 1158 cibles de TGF-β, 68 gènes ont été reconnus d'avoir modifié leurs niveaux de transcription concomitante avec l'atténuation. Dans ce travail de thèse, nous avons étudié les voies de signalisations impliquées dans la régulation de l’adhésion et l’invasion des cellules infectées par Theileria. Nous nous sommes particulièrement intéressés à l’étude de la voie de signalisation TGF-β2 et ses effecteurs. Nos résultats montrent que l’activation de la voie de signalisation de TGF-β2 par Theileria entraîne une augmentation de l’invasion et de l’adhérence des cellules transformées par deux mécanismes différents, soit en activant la voie de signalisation PGE2/EP4/cAMP/PKA/EPAC/CREB, soit en stimulant la voie GRB2/PI3-K/AP-1. Les macrophages atténués infectés par Theileria sont plus stressés oxydativement ce qui diminue leur adhérence et leur invasion cellulaire. Ceci nous a amené à étudier en collaboration avec un autre doctorant (Mehdi Metheni) le rôle de TGF-β2 dans la régulation du stress oxydatif dans les macrophages infectés par Theileria. Nos données montrent que les niveaux élevés de TGF-β2 stimule l’expression de la catalase, une enzyme anti-oxydante qui convertit le H2O2 en H2O et la baisse de H2O2 favorise la virulence en augmentant l’invasion et l’adhésion des cellules infectées par Theileria (résultats supplémentaires). De plus, nous avons examiné le statut de stress oxydatif et le type de glycolyse utilisé par les cellules infectées par Theileria. Les cellules transformées par Theileria agissent comme des cellules cancéreuses, elles consomment énormément de glucose. La protéine BAD joue un rôle important dans l’apoptose ainsi que dans la voie de glycolyse. Son activité est régulée par phosphorylation en réponse à des facteurs de croissance et de survie. BAD peut être phosphorylée par la PKA sur le résidu sérine 155. Durant ma thèse, nous avons examiné le rôle de la phosphorylation de BAD par la PKA dans la régulation du métabolisme cellulaire des macrophages infectés par Theileria. Nos résultats montrent que l’abolition de la phosphorylation de BAD par la PKA dissocie le complexe mitochondrial formé entre BAD et HK2, ce qui induit l’ubiquitynation et la dégradation de HK2 par le protéasome. La baisse de HK2 stimule la voie de phosphorylation oxydative en faveur de l’effet Warburg dans les cellules infectées par Theileria. / Theileria parasites (Theileria. annulata and T. parva) are intracellular protozoa and members of the phylum Apicomplexa. Theileria parasites are the only eukaryotes that possess the property of being able to transform another eukaryote, their leukocyte host cells. Transformed leukocytes show many characteristics of tumour cells such as heightened invasive capacity; however the tumour-like phenotype can be totally reversed upon drug induced parasite death and attenuated by multiple in vitro passages. Such multiple-passaged attenuated lines are used as live vaccines against tropical theileriosis. The similarities in tumour hyper-invasiveness between Theileria-transformed leukcocytes and human lymphomas imply that observations on Theileria-induced leukocyte transformation have the potential to give generally applicable insights into the mechanisms underpinning tumour virulence. My host laboratory described higher TGF-β2 levels in virulent infected macrophages and following microarray analysis of virulent compared to attenuated macrophages found that among the 1158 TGF-β-targets, 68 genes had altered transcript levels concomitant with attenuation. In this study, we investigate the signalling pathways involved in the regulation of cellular adhesion and invasiveness of Theileria-infected cells. We were especially interested in the study of TGF-β2 signalling in Theileria-transformed virulent versus attenuated macrophages. My results indicate that following Theileria infection of macrophages, the TGF-β2 signalling pathway is activated and induces an increase in adhesion of virulent transformed macrophages through two different mechanisms: either by activating a PGE2 / EP4 / cAMP / PKA / EPAC / CREB signaling pathway, or by stimulating a GRB2 / PI3-K / AP-1 pathway. As attenuated macrophages display heightened oxidative stress, which underpins their loss of adhesion and invasiveness, in collaboration with another PhD student (Mehdi Metheni) we investigated the role of TGF-β2 in the regulation of the oxidative stress status of Theileria-infected macrophages. Our data show that high levels of TGF-β2 increase the expression of catalase, an anti-oxidant enzyme that converts H2O2 into H2O and the drop in H2O2 output results in regain of the virulence trait heightened adhesion of Theileria-transformed macrophages to fibronectin. Theileria-transformed macrophages display many features of cancer cells such as their consumption of larger quantities of glucose. The BCL-2 family protein BAD has an alternative function in glucose metabolism separate from its role in apoptosis. The activity of BAD is regulated by phosphorylation in response to growth/survival factors. BAD can be phosphorylated on Ser155 by PKA. So during my thesis studies I examined the role of PKA mediated phosphorylation of BAD in the regulation of the cellular metabolism of Theileria-transformed macrophages. My results showed that ablation of BAD S155 phosphorylation dissociates the mitochondrial complex of BAD and HK2 and cytosolic HK2 becomes ubiquitinated and degraded by the proteasome. Loss of HK2 switches the metabolism of Theileria-transformed leukocytes from Warburg-like to OXPHOS-like glycolysis.