Memoria para optar al Título Profesional de Médico Veterinario / El virus diarrea viral bovina (VDVB) es el agente causal del complejo Diarrea Viral Bovina/ Enfermedad de las Mucosas y otros cuadros clínicos, que generan importantes pérdidas económicas en la industria del bovino. El VDVB presenta una gran variabilidad genómica, que ha llevado a clasificarlo en dos genotipos (1 y 2). En el genotipo VDVB-1 se identifican 15 subgrupos virales (1a-1o) y en el genotipo VDVB-2 sólo dos (2a y 2b). En Chile, el virus presenta una amplia diseminación, con prevalencias serológicas de un 69,2% en la Región de la Araucanía, De los Ríos y De los Lagos y de un 59,7% y 86% en bovinos de leche y de carne de la Región Metropolitana respectivamente. El objetivo de esta memoria fue determinar la composición genética de los virus del VDVB que infectan a los bovinos en Chile. Para ello, a cuarenta y cinco virus obtenidos desde distintas regiones de Chile se procedió a establecer su parentesco genético por filogenia molecular de la región 5´ no codificante (5´NCR) del genoma viral. Los resultados indican que cuarenta virus pertenecen al genotipo VDVB-1 y cinco al genotipo VDVB-2. En el genotipo VDVB-1, 2 virus pertenecen al subgrupo VDVB-1a, quince al VDVB-1b, veinte al VDVB-1j y tres al VDVB-1i, siendo este último subgrupo detectado por primera vez en Chile. Todos los virus del genotipo VDVB-2 pertenecen al subgrupo VDVB-2a. Los resultados permiten concluir que los virus del VDVB que circulan actualmente en el ganado bovino de Chile presentan una alta variabilidad genómica y su composición genética es muy similar a la de los virus presentes en Argentina. / Proyecto FONDECYT 1060581

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published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

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Poliovirus is a small, structurally simple virus that can serve as a powerful model system for the elucidation of the basic processes involved in the genetic control of macromolecular synthesis. The physical and biochemical characterization of temperature-sensitive and drug-resistant mutants of this virus can provide insight into the normal sequence of events during the replication and assembly of the wild-type (wt) virus. The specific interference of the infecting virus with the major pathways of macromolecular synthesis in the host cell offers a possible inroad to the exploration of the relevant control systems. This research is divided into two major segments: (1) a temperature-sensitive mutant of poliovirus type 1, tsB9, and a guanidine-resistant mutant, gʳH, were characterized physiologically; (2) a physiological screening procedure that quickly and efficiently reveals the phenotype of a large number of poliovirus mutants in a short period of time was developed and validated. Two guanidine-resistant and twelve temperature-sensitive mutants of poliovirus type 1, Mahoney, were generated and compared with wt, defective-interfering particles, gʳH, and tsB9 using the screening procedure herein developed. The temperature-sensitive mutant, tsB9, appears to be a structural protein mutant bearing a related defect in ribonucleic acid synthesis at the restrictive temperature. The mutant gʳH was found to differ from the wt virus only in the guanidine resistance of its growth and ribonucleic acid synthesis, although a detailed electrophoretic analysis of its proteins was not done. Among the newly isolated mutants, strains were found with defects in each of the major viral functions except one. No mutant was found to be defective in the ability to inhibit host-cell protein synthesis. The screening procedure developed met all of the criteria set for it mentioned above. It has the potential of being adapted to many virus-cell systems for the rapid determination of mutant phenotype.

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