Please read the abstract in the section 00front of this document / Thesis (PhD (Microbiology))--University of Pretoria, 2005. / Microbiology and Plant Pathology / unrestricted

The purpose of these investigations was to isolate and purify the largest of several antigens demonstrable in rabies-infected suckling mouse brains. The biochemical and biophysical properties of the antigen were studied with a view to elucidating its contribution to the intracellular synthesis and the structure of the virus particles. Extracts of normal and infected suckling mouse brains were purified by precipitation at pH 4.5 and freed of the smaller antigens by centrifugation prior to digestion with RNAase, DNAase and trypsin. The large antigen was purified by enzyme treatment, preparative ultracentrifugation, exclusion chroma tography and gradient centrifugation and appeared as rings varying in diameter between 8 and 12 mμ when examined by electron microscopy. Methods for the chemical estimation of pentose, deoxypentose and nitrogen were modified to meet the requirements of this investigation, and these techniques were used to determine the composition of the purified antigen. The antigen is a ribonucleoprotein, and found to be resistant to RNAase, DNAase, trypsin and chymotrypsin. A purified solution of the antigen contained 7.3μg RNA/ml., 11.4μg protein/ml and probably a trace of DNA. The success of this programme has resulted in the accumulation of certain original information which has been used in clari£ying the nature and structure of the largest soluble antigen.

No description available.

Orientador: Jane Megid / Banca: Hélio Langoni / Banca: Marcos Bryan Heinemann / Resumo: A utilização de métodos sensíveis e específicos para o diagnóstico da raiva constitui uma importante ferramenta para o controle e profilaxia dessa enfermidade. A Reação em Cadeia pela Polimerase através de Transcriptase-Reversa (RT-PCR) tem sido utilizada com bons resultados no diagnóstico do vírus rábico, mesmo quando as amostras estão em estágio de decomposição. Adicionalmente as técnicas moleculares têm sido utilizadas para estudos epidemiológicos possibilitando um melhor conhecimento da epidemiologia viral. O presente trabalho teve como objetivo avaliar as técnicas de RT-PCR e hnRT-PCR para a detecção do vírus rábico em estudos retrospectivos, para isso foram avaliadas 101 amostras cerebrais de diferentes espécies animais armazenadas por diferentes períodos, recém-descongeladas e mantidas em temperatura ambiente por 72 horas para decomposição. Os resultados das técnicas de RT-PCR e hnRT-PCR foram comparados com resultados prévios da Imunofluorescência Direta (IFD) e Inoculação Intracerebral em Camundongos (IC). Das 50 amostras positivas testadas, 26 (52%) apresentaram resultados positivos para a RT-PCR e 45 (90%) com a associação da hnRT-PCR quando realizadas em amostras recentemente descongeladas. Das amostras em decomposição foram analisadas 48 previamente positivas; onde 17 (34,3%) apresentaram resultado positivo para a RT-PCR e 36 (75%) com a associação da hnRT-PCR. Não foram encontrados resultados falso-positivos nas amostras negativas submetidas às técnicas de biologia molecular. A hnRT-PCR apresentou maior sensibilidade em relação à RT-PCR nas amostras recém-descongeladas e em decomposição. Os resultados sugerem a viabilidade de sua aplicação em estudos retrospectivos em materiais descongelados e decompostos. / Abstract: The use of methods, both sensitive and specific, for rabies diagnosis are important tools for the control and prophylaxis of the disease. Reverse-Transcriptase Polymerse Chain Reaction (RT-PCR) has been used in rabies diagnosis with good results, even in decomposed materials. Additionally, molecular techniques have been used for epidemiological studies and better knowledge of viral epidemiology. The aim of this work was to evaluate the RT-PCR and hnRT-PCR in rabies virus detection in retrospectives studies. RT-PCR and hnRT-PCR were evaluated in 151 brain samples from different animal species, thawed and left at room temperature for 72 hours for decomposition. The RT-PCR and hnRT-PCR results were compared with preview results from Fluorescent Antibody Test and Mouse Inoculation Test. From the 50 positive fresh samples, 26 (52%) were positive for RT-PCR and 45 (90%) for hnRT-PCR. From the 48 positive decomposed samples, 17 (34, 3%) were positive for RT-PCR and 36 (75%) for hnRT-PCR. No false-positives results were found in the negatives samples submitted to the molecular techniques. These results show that the hnRT-PCR was more sensitive than RT-PCR, and both techniques presented lower sensibility in decomposed samples. The hnRT-PCR presented greater sensibility than the standards techniques (IFD e IC) in decomposed materials for rabies diagnosis. These results suggest the viability of the application of molecular techniques in thawed and decomposed materials for retrospective studies. / Mestre

Rabies, one of the oldest recognized viral zoonotic diseases, is a fatal encephalomyelitis transmitted to man via contact with infected animals. Evan today, rabies still is a disease of public health concern with many potentially preventable deaths occurring mainly in Asia, Africa and Latin America. Rabies and rabies-related viruses are members of the Lyssavirus genus, which comprises the rabies virus (genotype 1), Lagos bat virus (genotype 2), Mokola virus (genotype 3), Duvenhage virus (genotype 4), European bat lyssaviruses 1 and 2 (genotypes 5 and 6) and the Australian bat lyssavirus (genotype 7). Antigenic and genetic studies have shown that rabies virus strains circulating in particular host species tend to undergo genetic adaptation and evolve into distinct biotypes that differ in antigenicity and pathogenicity. Two biotypes of rabies virus are recognized in southern Africa. The first called the canid viruses, infect carnivores of the family Canidae (dogs, jackals and bat-eared foxes) and the second, the viverrid viruses, infect carnivores of the family Herpestidae (the yellow mongoose Cynictis penicil!ata and the slender mongoose Galerella sanguinea). In an endeavour to better understand the molecular epidemiology of lyssaviruses in Zimbabwe and South Africa, we analysed nucleotide sequences of the glycoprotein and the G-L intergenic region (rabies viruses) and the nucleoprotein gene (Mokola viruses). The main aim of the studies described in this thesis was to characterise lyssaviruses (genotypes I and 3) from Zimbabwe and compare them to those present in South Africa. In addition, we wanted to establish the role of the various rabies variants in rabies epizootics in the southern African subcontinent. It could be shown from this study that all the southern African canid viruses were closely related, with no general distinction between viruses from any of the canid species. Despite the general overall similarity between the canid viruses, certain phylogenetic groupings were apparent and by association with host species, geography and year of isolation, certain groups could be identified as particular epidemiological cycles. A high genetic diversity was evident amongst viverrid rabies viruses, the opposite of our observation for canid viruses. The viverrid virus groups corresponded to geographical pockets that were independent of host species. Mokola viruses from Zimbabwe were shown to be different from those from South Africa and phylogenetic relationships of these viruses were related to their geographical location of origin. This study has demonstrated the value of multinational surveillance and investigation in understanding the epidemiology of lyssaviruses in southern Africa and elsewhere in Africa. The results presented here will serve as basis for future studies on lyssaviruses in Africa and will contribute to the improved surveillance and control programs of rabies and Mokola viruses in the region. / Thesis (PhD (Microbiology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

This work concerns the use of engineered genetic tools to build maps of the mammalian nervous system. Within the practice of circuit neuroscience, one of the most effective tools to emerge in recent years are the neurotropic viruses. Among these are modified strains of rabies virus which are made safe for laboratory use. We introduce here a novel form of engineered rabies virus with substantially improved utility for exploring the structure and function of neural circuits. Additionally, using this new tool, an investigation of an important motor circuit, the cortico-striatal circuit, is presented.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 67-76). Also available via the Internet.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Les virus zoonotiques sont une menace pour les humains à cause de leur capacité à passer des réservoirs animaux à l'homme. La rage est provoquée par un virus zoonotique (Virus de la Rage) qui a de multiples réservoirs animaux. La rage est contractée lors de la morsure par un animal infecté et est incurable et létale après l'apparition des premiers symptômes. Un défi visant à éradiquer la rage chez les chiens à l'horizon 2030 a été proposé. Il imposera de stopper la transmission du virus aux populations de chiens à partir des autres réservoirs animaux. Pour cela, il est essentiel de comprendre les mécanismes de transmission entre hôtes potentiels du virus. Dans notre thèse, nous faisons l'hypothèse que le passage d'un hôte à un autre est lié à la diversité des populations virales chez un hôte donné, appelée "hétérogénéité virale".Pour étudier cette hétérogénéité virale, des méthodes de séquençage des populations virales ont été développées. La transmission du virus de la rage entre chiens a été analysée et un évènement de transmission entre chien et renard a été étudié. Une plus importante hétérogénéité virale a été observée chez le renard après sa contamination par le chien en comparaison avec d'autres renards infectés par des congénères de la même espèce. Ceci suggère que l'hétérogénéité virale est importante dans le phénomène de transmission inter-espèce. Ces résultats sont importants pour améliorer notre compréhension de l'évolution du virus de la rage chez un nouvel hôte et pourront aider les efforts d'éradication de la maladie. / Zoonotic viruses are a threat to humans, jumping from animal reservoirs into humans. Rabies is caused by rabies virus (RABV), a zoonotic virus, with many animal reservoirs. Rabies is contracted from a bite of infected animal and once symptoms appear, death is inevitable. A challenging target date of 2030 to eliminate rabies in dogs has been set. One challenge will be stopping RABV re-entering the dog population from other animal reservoirs. Understanding how RABV switches hosts is important to prevent it happening. In this thesis, I hypothesise that successful host switching is due to the diverse population of viruses within the host termed ‘viral heterogeneity’. To investigate viral heterogeneity, methods to sequence the virus populations within clinical samples were developed. Transmission of RABV within dogs was analysed and a host shift event from dogs to foxes was investigated. High viral heterogeneity was seen in foxes after the host shift than in other foxes, suggesting it is important for a successful host shift. These data will be important to improve our understanding of how viruses evolve in new hosts, helping governments to eradicate disease.