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.

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.

Em função da proximidade cada vez maior entre o cavalo e o homem, é de extrema importância ter conhecimentos das doenças que acometem os equinos, que por ventura, podem acometer seres humanos. Dentre muitas doenças, pode-se citar duas, que promovem grandes perdas econômicas aos rebanhos eqüinos, tanto no tratamento desses rebanhos, como com a morte dos mesmos, dificultando a importação e exportação de animais: a babesiose e a erliquiose (anaplasmose), que podem estar ou não associadas, acometendo um animal, concomitantemente. A presente pesquisa teve como objetivo investigar e diagnosticar doença concomitante babesiose (por Babesia equi ou Theileria equi) e Erliquiose (por Erliquia equi ou Anaplasma phagocytophilum), no estado de São Paulo, em rebanhos eqüinos, utilizando as técnicas de Nested PCR (Nested polymerase chain reaction reação em cadeia pela polimerase para diagnóstico de T. equi e A. phagocytophilum) e c-ELISA (competitive enzyme-linked immunosorbent assay para diagnóstico de T. equi) ou ELISA indireto (para diagnóstico de A. phagocytophilum) e comparar os resultados obtidos nas diferentes técnicas em 250 amostras de eqüino (sangue total e soro). Como resultado, obteve-se 38,4%, 46% e 36% de positividade, respectivamente, nos testes de pesquisa de hematozoário, c-ELISA e Nested PCR para Theileria equi e 0%, 3% e 0% de positividade, respectivamente, nos testes de pesquisa de hemoparasita, ELISA indireto e Nested PCR para Anaplasma phagocytophilum, não sendo observada a co-infecção de Babesiose e Anaplasmose no rebanho estudo / Due to the increasing proximity between horse and man, it is of extreme importance to understand the diseases that affect horses which by chance may affect humans. Among many diseases, babesiosis and ehrlichiosis (anaplasmosis) promote high economic losses to horses herds in consequence of costs of treatment and also death, making it difficult to import and export animals: They can or not be linked affecting an animal at the same time. This study aimed to investigate and diagnose concomitant babesiosis (Babesia equi and Theileria equi) and ehrlichiosis (for ehrlichia equipment or Anaplasma phagocytophilum) in equine herds of the state of Sao Paulo, using the techniques of Nested PCR (Nested polymerase chain reaction for the diagnosis of T. equi and A. phagocytophilum) and c-ELISA (competitive enzyme-linked immunosorbent assay for diagnosis of T. equi) or ELISA (for diagnosis of A. phagocytophilum). Also to compare results obtained in these different techniques in 250 samples of horse (whole blood and serum). Results showed 38.4%, 46% and 36% positivity, respectively, in tests for the detection of Theileria equi through hematozoan, c-ELISA and Nested PCR and 0%, 3% and 0% positivity, respectively, in tests for the detection of Anaplasma phagocytophilum through blood parasites, indirect ELISA and Nested PCR. It was not observed co-infection Babesiosis and anaplasmosis in the herd study

Em função da proximidade cada vez maior entre o cavalo e o homem, é de extrema importância ter conhecimentos das doenças que acometem os equinos, que por ventura, podem acometer seres humanos. Dentre muitas doenças, pode-se citar duas, que promovem grandes perdas econômicas aos rebanhos eqüinos, tanto no tratamento desses rebanhos, como com a morte dos mesmos, dificultando a importação e exportação de animais: a babesiose e a erliquiose (anaplasmose), que podem estar ou não associadas, acometendo um animal, concomitantemente. A presente pesquisa teve como objetivo investigar e diagnosticar doença concomitante babesiose (por Babesia equi ou Theileria equi) e Erliquiose (por Erliquia equi ou Anaplasma phagocytophilum), no estado de São Paulo, em rebanhos eqüinos, utilizando as técnicas de Nested PCR (Nested polymerase chain reaction reação em cadeia pela polimerase para diagnóstico de T. equi e A. phagocytophilum) e c-ELISA (competitive enzyme-linked immunosorbent assay para diagnóstico de T. equi) ou ELISA indireto (para diagnóstico de A. phagocytophilum) e comparar os resultados obtidos nas diferentes técnicas em 250 amostras de eqüino (sangue total e soro). Como resultado, obteve-se 38,4%, 46% e 36% de positividade, respectivamente, nos testes de pesquisa de hematozoário, c-ELISA e Nested PCR para Theileria equi e 0%, 3% e 0% de positividade, respectivamente, nos testes de pesquisa de hemoparasita, ELISA indireto e Nested PCR para Anaplasma phagocytophilum, não sendo observada a co-infecção de Babesiose e Anaplasmose no rebanho estudo / Due to the increasing proximity between horse and man, it is of extreme importance to understand the diseases that affect horses which by chance may affect humans. Among many diseases, babesiosis and ehrlichiosis (anaplasmosis) promote high economic losses to horses herds in consequence of costs of treatment and also death, making it difficult to import and export animals: They can or not be linked affecting an animal at the same time. This study aimed to investigate and diagnose concomitant babesiosis (Babesia equi and Theileria equi) and ehrlichiosis (for ehrlichia equipment or Anaplasma phagocytophilum) in equine herds of the state of Sao Paulo, using the techniques of Nested PCR (Nested polymerase chain reaction for the diagnosis of T. equi and A. phagocytophilum) and c-ELISA (competitive enzyme-linked immunosorbent assay for diagnosis of T. equi) or ELISA (for diagnosis of A. phagocytophilum). Also to compare results obtained in these different techniques in 250 samples of horse (whole blood and serum). Results showed 38.4%, 46% and 36% positivity, respectively, in tests for the detection of Theileria equi through hematozoan, c-ELISA and Nested PCR and 0%, 3% and 0% positivity, respectively, in tests for the detection of Anaplasma phagocytophilum through blood parasites, indirect ELISA and Nested PCR. It was not observed co-infection Babesiosis and anaplasmosis in the herd study

As part of the larger survey to map the geographical distribution of Babesia and Theileria parasites in the Southern African rhinoceros population, white rhinoceroses were sampled during routine immobilizations in the Kruger National Park. Polymerase Chain Reaction (PCR) and Reverse Line Blot (RLB) hybridization assays were used to screen for the presence of haemoprotozoa and complete blood counts were used to assess associated changes in clinical parameters. Of the 195 rhinoceroses sampled, 36.4% tested positive for the presence of Theileria bicornis, with no significant change in the haematological parameters measured. None of the rhinoceroses sampled tested positive for Babesia bicornis, the parasite linked to mortalities in black rhinoceroses. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted

Previous studies have shown that cytotoxic CD8+ T cells are important mediators of immunity against the bovine intracellular protozoan parasite T. parva. The present study set out to determine the role of granule enzymes in mediating killing of parasitized cells, first by characterising the granzymes expressed by bovine lymphocytes and, second, by investigating their involvement in killing of target cells. Experiments using the perforin inhibitor concanamycin A confirmed that CD8+ T cell killing of T. parva-infected cells is dependent on granule exocytosis, a process that involves release of granzymes into the target cell, resulting in activation of apoptotic pathways. Analysis of the bovine genome sequence identified orthologues of granzymes A, B, H, K and M, as well as another gene O, most closely related to granzyme A. The genes were found within 3 loci in the genome. Using specific PCR assays, all of these granzymes were shown to be expressed in Theileria-specific CD8+ T cells. Further studies were undertaken to study the role of granzyme B in killing. DNA constructs encoding functional and non-functional forms of bovine granzyme B were produced and the proteins expressed in COS cells were used to establish an enzymatic assay to detect and quantify expression of functional granzyme B protein. Using this assay, the levels of killing of different T. parvaspecific CD8+ T cell clones were found to be significantly correlating with levels of granzyme B protein expression. Moreover, the granzyme B inhibitor III, Z-IETDFMK was shown to inhibit killing by CD8+ T cell clones.

The work presented in this thesis is focused upon the community of endemic pathogens of African cattle in Sub-Saharan Africa, which has long constrained livestock production in these areas. The first aim of this work is to investigate whether the pathogen community as a whole shapes the ensuant epidemiology and morbidity which are currently attributed to any of its individual pathogens. The second aim is to determine if a greater understanding of the interactions present amongst genetically distinct parasites of the same species can be used to better explain epidemiological features that are at present poorly understood. Emphasis is placed on examining spatial variation in the epidemiology of Theileria parva, a tick-transmitted protozoan that causes East Coast Fever. To achieve these aims, this work examines field data collected from a large and comprehensive study conducted in south east Uganda. Through application of apposite statistical techniques and mathematical modelling, aspects of the complex relations amongst the pathogen community and their environment are explored. Evidence is presented that demonstrates the paramount role of the pathogen community as a whole in shaping the infection dynamics and pathogenicity of any of its individual components. By focusing on a single member of this pathogen community (Theileria parva), some of the influences of host, vector, geographical location, temporal dynamics and intra-species pathogen interactions are elucidated. Application of a polymorphic molecular marker to Theileria parva infected blood samples and the use of Cox proportional hazard analysis, show variability in the survival of infections in cattle in high and low tick challenge areas. Moreover infection survival, which plays a pivotal role in parasite transmission, is shown to be a function of the interactions established amongst genetically distinct co-infective parasites. In consequence, vector intensity alone is insufficient to develop reliable transmission models which can accurately predict the epidemiology of the parasite inside and outside enzootic belts. Finally, a theoretical model is developed which, based upon the field evidence obtained throughout this work, provides a possible explanation for the mechanics of T. parva survival in cattle. In summary, this thesis makes a case that consideration of both inter- and intra-species pathogen interactions, can greatly augment understanding of the epidemiology of these pathogen communities. An integrated approach to pathogen dynamics can better equip an integrated approach to control of important diseases of African cattle.

Thesis (MSc (Veterinary Tropical Diseases, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Previous research has provided evidence that CD8 T cells mediate immunity against infection with Theileria parva. However, the immunity induced by one parasite strain doesn‟t give complete protection against other strains and this is associated with parasite strain specificity of the CD8 T cell responses. There is evidence that such strain specificity is a consequence of the CD8 T cell responses of individual animals being focused on a limited number of immunodominant polymorphic peptide-MHC determinants. Dominant responses to the Tp2 antigen have been demonstrated in animals homozygous for the A10 MHC haplotype. Three Tp2 epitopes recognised by A10+ animals (Tp249-59, Tp250-59 and Tp298-106) have been defined. This project set out to investigate the dominance of these epitopes and to examine the T cell receptor (TCR) repertoires of the responding T cells. The specific objectives were to: (i) Determine the dominance hierarchies of the three defined Tp2 epitopes in both A10-homozygous and -heterozygous cattle. (ii) Examine the clonal repertoires of epitope-specific responses by analysis of TCR gene expression. (iii) Isolate full-length cDNAs encoding TCR α and β chain pairs from T cell clones of defined epitope specificity and use them to generate cells expressing the functional TCRs. Using MHC class I tetramers the relative dominance of CD8 T cell responses were found to differ between A10-homozygous and heterozygous cattle. All A10-homozygous cattle examined had detectable responses to all 3 Tp2 epitopes, the Tp249-59 epitope consistently being the most dominant. By contrast, only some A10-heterozygous cattle had detectable responses to Tp2 and when present the response was specific only for the Tp298-106 epitope. Analyses of the sequences of expressed TCR β chains showed that the responses in individual animals were clonotypically diverse, but often contained a few large expanded clonotypes. The TCRs of Tp298-106–specific T cells showed preferential usage of the Vβ13.5 gene and the frequent presence of a “LGG” motif within the CDR3 of the B chain. A conserved (public) TCRβ clonotype shared by the Tp250-59-specific CD8 T cells from all A10-homozygous cattle was identified. The TCRα chains co-expressed with this public TCRβ clonotype were identified for a number of T cell clones. Lentivirus transduction of Jurkat cells with three full-length TCR α and β chain pairs resulted in successful expression of one of the α/β chain pairs as a functional TCR, thus providing the basis for future work to generate bovine T cells expressing defined TCRs in vitro.

Theileria species (sable) causes significant mortalities in roan (Hippotragus equinus), and to a lesser extent, sable antelope (Hippotragus niger) yearly. Treatment of the condition and an ‘infect and treat’ vaccination method using a tick-derived stabilate both rely on the availability of buparvaquone, a naphthoquinone with anti-theilerial activity. As buparvaquone is a controlled drug which is not commercially available in South Africa, a viable commercial alternative prevention or treatment method is necessary to control this disease. This study explores the effectiveness of an alternative vaccination method using Theileria sp. (sable) infected in vitro cultured leukoblasts. A Theileria sp. (sable) containing cell line was initiated from lymph node biopsy material of an infected roan antelope and the parasite was successfully propagated in vitro. Attenuation is believed to have been achieved by 16 cycles of passage. Real time PCR suggests that the parasite was successfully transmitted via subcutaneous inoculation with this cell line to two naïve roan antelope. These two inoculated animals remained clinically unaffected by challenge with a tick stabilate used in the ‘infect and treat’ vaccination method. In contrast, the two unvaccinated control animals became clinically ill and required buparvaquone treatment after challenge. This pilot study provides enough evidence to encourage further investigation in the use of Theileria sp. (sable) infected cells as a potential vaccine. A field study involving more animals which are challenged by natural infection after inoculation is the proposed next step. / Dissertation (MMedVet)--University of Pretoria, 2010. / Paraclinical Sciences / unrestricted