Parmi les rétrovirus tumorigènes, les rétrovirus appelés « complexes » dont font partie HTLV-1 chez l’homme et BLV chez le mouton, sont responsables de leucémies lymphoïdes chroniques caractérisées par des pathogenèses similaires. Bien que la contribution essentielle de la protéine Tax dans la leucémogenèse soit bien établie pour ces deux virus, il existe toujours une contreverse quant à l’expression des protéines virales -dont l’oncoprotéine Tax- dans les cellules transformées. Dans le cas de HTLV-1 et BLV, le virus est latent. Une hypothèse attrayante suggère que l’extinction complète du provirus accompagnée du blocage transcriptionnel de l’expression de Tax dans la cellule leucémique serait un élément indispensable au développement de la tumeur en réduisant son immunogénicité. Le silencing viral permettrait à la cellule infectée d’échapper à la reconnaissance par le système immunitaire de l’hôte. <p>Dans la première partie de notre travail, nous avons pu montrer, grâce à l’observation et le suivi de deux moutons infectés par BLV, que l’extinction virale était associée au développement tumoral. Alors que la phase asymptomatique est caractérisée par l’existence de différents clones cellulaires infectés et exprimant le virus, la phase tumorale est caractérisée par l’existence d’un seul clone cellulaire dans lequel l’expression virale est éteinte. Dans le cas du mouton S2531, nous avons mis en évidence que le silencing observé dans la phase tumorale est d’origine génétique. L’extinction de l’expression virale et la domination du clone muté au niveau de la protéine Tax (K303) sont associées à l’émergence de la leucémie et constituent une caractéristique de la phase tumorale. Le deuxième mouton étudié, S267, est caractérisé par la présence de cellules infectées non transformées et transformées au même moment. Par ailleurs, le mouton S267 est caractérisé par une absence de mutations ou délétions au niveau du provirus intégré dans les cellules tumorales. Dans la deuxième partie de notre travail, nous avons pu, grâce à l’établissement de la lignée L267 dans laquelle le silencing viral n’est pas lié à une défection dans la structure génomique du provirus, élucider les mécanismes épigénétiques responsables du silencing. Nous montrons que ce provirus silencieux peut être réactivé in vitro 1) lorsque la protéine Tax sauvage est introduite par transfert rétroviral, 2) après traitement des cellules par la trichostatine A (TSA), un inhibiteur des histones désacétylases, 3) par traitement des cellules à la 5’azacytidine, un agent inhibiteur de DNA méthyltransférases. La réactivation du provirus silencieux lui confère la capacité d’infecter des moutons sains, suggérant que le provirus est complet et exempt de mutation qui pourrait altérer son fonctionnement. Les complexes de désacétylation des histones msin3A et HDAC-1 jouent un rôle important dans l’établissement du silencing viral via la condensation de la chromatine, et ce changement de la structure chromatinienne est lié a un ensemble de modifications ciblant les acides aminés des queues N-terminales des histones H3 et H4 établissant ainsi un code histone pour l’extinction et l’expression du provirus. Enfin, l’étude comparative des profils d’expression génique de cellules B tumorales dans lesquelles le provirus BLV est soit silencieux, soit ré-activé suite à l’expression exogène de Tax a montré que les mécanismes épigénétiques de silencing se superposent même dans le modèle génétique de silencing. De plus le rétablissement de l’expression virale par Tax est associé à une élimination des complexes de désacétylation des histones au niveau du promoteur viral.<p>Nos résultats ouvrent le champ vers l’utilisation de modèle de leucémie ovine dans des essais thérapeutiques basés sur la combinaison du traitement par des inhibiteurs des HDACs et des DNMTs et une immunothérapie ciblant des antigènes tumoraux d’origine virale ou cellulaire. De telles expériences in vivo constitueront un modèle utile pour le traitement l’ATLL et de pathologies prolifératives touchant les cellules B chez l’homme.<p><p> / Doctorat en sciences biomédicales / info:eu-repo/semantics/nonPublished

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / To determine the main factors influencing the biological behavior of 40 squamous cell carcinomas (SCC) of the upper digestive tract (UDT) of cattle associated with spontaneous ingestion of bracken fern (Pteridium aquilinum), morphological, including cell proliferation, and immunohistochemical aspects were studied. The aspects analyzed included anatomical localization of SCCs, degree of differentiation, occurrence and distribution of metastasis, intensity of the lymphoplasmocytic inflammatory infiltrate (LPII), of the desmoplastic reation, tumor-associated tissue eosinophilia, and the cell proliferation index evaluated through quantification of the argyrophilic nucleolar organizer regions (AgNORs). Forty two percent of SCCs were in the cranial region, 12.5% in the middle, and 45% in the caudal region of the UDT. The neoplasms were classified as well differentiated (WD-SCC; 67.5%), moderately differentiated (MD-SCC; 20%), or poorly differentiated (PD-SCC; 12.5%). When the degree of differentiation was correlated to the anatomical localization, it was observed in the cranial region that 88.2% were WD-SCC and 11.8% were MD-SCC. In the middle region, 60% were WD-SCC, 20% were MD-SCC, and 20% were PD-SCC. In the caudal region, 50% were WD-SCC, 27,8% were MD-SCC, and 22,2% were PD-SCC. Metastasis occurred in 57.75% of the cases, mostly to regional lymph nodes, and were observed in 58.82% of the cases with SCCs of the cranial region; in 40% of the middle region, and in 61.11% of the caudal region. Metastasis to regional lymph nodes and/or to distant organs were found in 44.44% of WDSCC, 75% of MD-SCC, and 100% of PD-SCC. Migration and invasion patterns were analyzed through the immunohistochemistry technique for cytokeratin. Islands and ribbons of neoplastic keratinocytes predominated in the WD-SCCs. The patterns varied greatly in the MD-SCCs, although small aggregates, ribbons, and cords predominated. PD-SCCS were characterized by small aggregates and individual cells. Lymphatic or hematogenous invasion were detected in 11/40 SCCs. There were SCCs originating from the ductal epithelium of the salivary glands. This finding was not previously reported. The intensity of the LPII was more accentuated in the BD-SCCs than in the MDs or PDs. The intensity of the desmoplastic reaction was quantified through the immunohistochemistry technique for vimentin, and was more severe in the PD-SCCs. The tumor-associated tissue eosinophilia (TATE) was measured in the SCCs and classified as mild, moderate, or severe. The only positive statistically significant association was established between TATE and LPII intensities. Cell proliferation was evaluated through quantification of the argyrophilic nucleolar organizer regions (AgNORs) on the neoplastic keratinocytes. AgNOR mean value and standard deviation (±sd) for WD-SCCs were 1.65 (±0.23), for MD-SCCs were 1.88 (±0.31), and for PD-SCCs were 2.39 (±0.26). The correlation between the AgNOR index and each histopathological grade was statistically significant. In conclusion, the factors which influenced the biological behavior of SCCs were the degree of cell differentiation, the patterns of migration and invasion, the intensity of LPII, TATE and desmoplastic reation, and the cell proliferation index measured through quantification of the AgNORs. / Aspectos morfológicos, incluindo proliferação celular, e imunoistoquímicos de 40 carcinomas de células escamosas (CCEs) do trato alimentar superior de bovinos que consumiram samambaia (Pteridium aquilinum) espontaneamente foram estudados, visando principalmente determinar os fatores que influenciam o comportamento biológico destes neoplamas. Os aspectos analisados incluíram localização anatômica dos CCEs, grau de diferenciação celular, ocorrência e distribuição de metástases, padrões de migração e invasão, intensidade do infiltrado inflamatório linfoplasmocítico (IILP), da reação desmoplásica e da eosinofilia tecidual associada a tumores (TATE), e o índice de proliferação celular avaliado através da contagem das regiões organizadoras nucleolares argirofílicas (AgNORs). Quanto a localização anatômica, 42% dos CCEs localizaramse na região cranial, 12,5% na média e 45% na caudal do trato alimentar superior (TAS). Os CCEs foram classificados quanto ao grau de diferenciação celular em bem (CCE-BD [67,5%]), moderadamente (CCE-MD [20%]) ou pouco diferenciados (CCE-PD [12,5%]). Quando relacionado o grau de diferenciação celular com a localização no TAS, verificou-se que na região cranial 88,2% eram CCEs-BD e 11,8% eram MD; na região média, 60% eram BD, 20% eram MD e 20% eram PD; na região caudal, 50% eram BD, 27,8% MD e 22,2% PD. Metástases ocorreram em 57,75% dos casos, principalmente para linfonodos regionais, e foram observadas em 58,82% dos CCEs na região cranial, em 40% dos da região média e em 61,11% dos da região caudal. Metástases para linfonodos regionais e/ou órgãos distantes foram encontradas em 44,44% dos CCEs-BD, em 75% dos MD e em 100% os PD. Foram analisados os padrões de migração e invasão com o auxílio da técnica de imunoistoquímica para citoqueratina. Nos CCEs-BD predominaram os padrões em ilhas e fitas de queratinócitos neoplásicos; nos MD os padrões variaram muito porém predominaram os agregados pequenos, fitas e cordões; nos PD predominaram os agregados e as células individuais. Invasão vascular linfática e/ou sangüínea foram observadas em 11/40 CCEs. Foram observados CCEs originando-se do epitélio dos ductos das glândulas salivares, aspecto este que não havia sido relatado anteriormente. Observou-se que a intensidade do IILP era muito mais acentuada nos CCEs-BD que nos MD e PD. A intensidade da reação desmoplásica foi quantificada através da imunistoquímica para vimentina e foi muito mais acentuada nos CCEs-PD. A TATE foi medida nos CCEs quanto à intensidade em leve, moderada ou acentuada. A única associação positiva estatisticamente significativa foi estabelecida entre a intensidade da TATE e a do IILP. A proliferação celular foi avaliada quantitativamente através da contagem das regiões organizadoras nucleolares argirofílicas (AgNORs) nos queratinócitos neoplásicos. A média e o desvio padrão (±DP) de AgNORs nos CCEs BD foi de 1,65 (±0,23), nos MD de 1,88 (±0,31) e nos PD foi de 2,39 (±0,26). A correlação entre o índice de AgNOR e cada grau de diferenciação celular foi estatisticamente significativa. Concluiu-se que os fatores que influenciaram no comportamento biológico dos CCEs foram o grau de diferenciação celular, os padrões de migração e invasão, a IILP, a TATE e da reação desmoplásica e o índice de proliferação celular avaliado através da contagem das AgNORs.

Surveys were conducted to compare the seasonal tick prevalence and loads, and sero-prevalence of tick-borne diseases (TBD) in Nguni and non-descript cattle on the sweet and sour communal rangelands of the Eastern Cape Province. The tick species observed on both rangeland types were Rhipicephalus appendiculatus (71.0 %), Rhipicephalus (Boophilus) species (29.2 %) and Rhipicephalus evertsi evertsi (40.2 %). Hyalomma species (19.0 %) occurred only on the sour rangeland. Tick loads were higher (P < 0.05) in the hot-wet season than in the cool-dry season. Cattle in the sweet rangeland had significantly lower (P < 0.05) tick loads than those in the sour rangeland. Rhipicephalus appendiculatus loads were lower (P < 0.05) in the indigenous Nguni than non-descript cattle in the hot-wet and post-rainy season. Hyalomma species were also significantly lower (P < 0.05) in the Nguni than non-descript cattle in all the seasons. Three TBDs were observed, namely Babesia bovis (44.6 %), Babesia bigemina (45.9 %) and Anaplasma marginale (25.6 %). All the animals were sero-negative for Ehrlichia ruminantium. Nguni cattle had lower (P < 0.05) sero-prevalence for A. marginale in the cool-dry season and B. bigemina in the cool-dry and hot-wet seasons. Cattle in the sweet rangeland had significantly lower sero-prevalence of B. bovis and B. bigemina. Infection with B. bovis and A. marginale decreased (P < 0.05) the packed cell volume. Nguni cattle were recommended for use in the integrated control of ticks and TBD in the communal areas of South Africa as they were better able to cope with tick and TBD infestations than non-descript breeds.

Abstracts in English and Zulu / Fluorescence polarization assay (FPA), a serological assay, was validated as an alternative test for the rapid and cost-effective diagnosis of bovine brucellosis, with the aim of improving the control of brucellosis in South Africa. The FPA is anticipated to distinguish between vaccinated and infected cattle, circumventing the challenge associated with the tests that are currently used. Positive cattle serum samples (n =420) confirmed by Complement Fixation Test were tested in conjunction with serum samples (n = 446) from non-infected cattle initially tested on Rose Bengal Test, CFT and compared with FPA. The optimum cut-off value that offers the highest diagnostic sensitivity (Dsn) and diagnostic specificity (Dsp) was determined as 87 mP with the use of ROC analysis. The Dsn and Dsp of FPA using this cut-off value was calculated at 99.09% - 100% and 68.09%- 76.61% respectively with a 95% confidence interval (cl). The area under curve (AUC) was calculated at 0.9842 with a 95% standard error (S.E) of 0.005532 with positive and negative likelihood ratio (+LR) (-LR) at 3.643 and 1.002, respectively. The FPA was found to be as effective as CFT and should be considered because of its accuracy and other advantages such as speed, high throughput and the objectivity of the interpretation of results that can be obtained electronically by the (PHERAstar) machine. The test should be included in routine serological diagnosis for brucellosis. / I- Fluorescence polarization assay (i-FPA) ukuhlolwa kwe-serological okuqinisekiswe njengenye indlela yokuhlola ukuxilongwa okusheshayo nengabizi kwe-bovine brucellosis, okuzokwenza ngcono ukulawulwa kwe-brucellosis eNingizimu Afrika. Ngaphezu kwalokho, i-FPA kulindeleke ukuthi yehlukanise phakathi kwezinkomo ezigonyiwe nezithelelekile futhi lokhu kuzonciphisa inselelo ehambisana nokuhlolwa esetshenziswa njengamanje. Amasampula amahle avumayo we-serum ezinkomo (n = 420) aqinisekiswa yi-CFT ahlolwe ngokuhlangana namasampula e-serum (n = 446) avela ezinkomeni ezingathelelekile ezahlolwa kuqala ku-RBT, CFT futhi kuqhathaniswa ne-FPA. Inani elinqunyiwe elikhulu elinikezela ukuzwela okuphezulu kokuxilonga (i-Dsn) kanye nokucaciswa kokuxilongwa (i-Dsp) kunqunywe njenge-87 mP kusetshenziswa ukuhlaziywa kwe-ROC. I-Dsn ne-Dsp ye-FPA esebenzisa leli nani elisikiwe libalwe ngama-99.09% - 100% no-68.09% - 76.61% ngokulandelana kwesikhathi sokuzethemba esingu-95% (cl). Indawo engaphansi kwe-Curve noma ijika thizeni (i-AUC) ibalwe ku-0.9842 enephutha elingu-95% elijwayelekile (SE) lika- 0.005532 elinezilinganiso ezinhle nezimbi ze-likehood (+ LR) (-LR) ngo-3.643 no- 1.002, ngokulandelana. I-FPA isebenza njenge-CFT futhi kufanele ibhekwe ngenxa yokunemba eneqiniso kwayo nezinye izinzuzo ezifana nejubane lokuthola imiphumela kanye nenhloso yokuchazwa kwemiphumela engatholakala ngomshini wekhomphuyitha (PHERAstar), i-FPA kufanele ifakwe ekuhlolweni okuvamile ngokujwayelekile kwe-serological ye-brucellosis. / Agriculture and  Animal Health / M. Sc. (Agriculture)

This dissertation looks at the impact of East Coast Fever on African homestead society in Natal in the period 1901-1910. The disease broke out in Natal at the beginning of 1904. With the realization that East Coast Fever was another lethal epizootic, the Natal Colonial Government introduced measures to control the spread of the disease and finally eradicate it. The campaign was, however, not successful. The disease thus spread throughout the colony and led to the loss of many cattle owned by Africans. By 1909 not more than four divisions in the colony remained free of the disease. The death of many cattle deprived Africans of the means of extensive cultivation, the source of income for the payment of rents and taxes, and Ilobolo. Many African males were forced to leave their homesteads for the towns and the mining sector in search of work. This eventually changed the nature of the homestead society. / History / M.A. (History)

This dissertation looks at the impact of East Coast Fever on African homestead society in Natal in the period 1901-1910. The disease broke out in Natal at the beginning of 1904. With the realization that East Coast Fever was another lethal epizootic, the Natal Colonial Government introduced measures to control the spread of the disease and finally eradicate it. The campaign was, however, not successful. The disease thus spread throughout the colony and led to the loss of many cattle owned by Africans. By 1909 not more than four divisions in the colony remained free of the disease. The death of many cattle deprived Africans of the means of extensive cultivation, the source of income for the payment of rents and taxes, and Ilobolo. Many African males were forced to leave their homesteads for the towns and the mining sector in search of work. This eventually changed the nature of the homestead society. / History / M.A. (History)