No description available.

No description available.

Thesis (DR. P.H.)--University OF MICHIGAN.

Despite the use of measles vaccine for over 30 years, measles continues to occur even in highly vaccinated populations. The goal set by the Pan American Health Organization to eliminate measles from the Americas has not been accomplished yet. Although live-measles attenuated vaccines have dramatically reduced the incidence of measles infection, relatively little is known about the immune response generated by vaccination. The principal objective of the work described in this thesis was to perform detailed analysis of cellular and humoral responses to primary measles vaccination in children from the developed and developing worlds. Studies involving Canadian children ranging in age from 12 months to 15 years of age demonstrated that cellular "memory" for measles antigens (lymphoproliferation) was induced in only 50--60% of vaccinees but that, in some children, this cellular response was more durable than anti measles antibody production. Phenotypic studies in these children demonstrated an evolution of early CD8+ T cell activation with later CD4+ T cell activation over a 5--8 week period after vaccination. Expression of CD30, a putative Th2 marker and the costimulatory molecule CTLA-4 on CD4+ and CD8+ T cells, was associated with a strong humoral response while increased production of IFN-gamma and IL-12 was associated with a strong LP response to vaccination. Similar, though less extensive, studies in Peru revealed that less than 25% of these developing world children mount detectable measles-specific LP responses after vaccination, despite having high antibody titers. Although there are many differences between the two study populations (e.g.: race, age at vaccination, vaccine strain), one especially striking difference was the relative "maturity" of T cells in Peruvian children (CD45RO expression) and the marked degree of PBMC activation at the time of vaccination in this setting.

Thesis (DR. P.H.)--University OF MICHIGAN.

Since the introduction of vaccines, many deaths due to various diseases including measles, have been drastically reduced. In Canada, there is a recommended vaccine schedule for all residents of the country; however, vaccine practises and immunisation schedules can vary from location to location as well as vary from country to country, leading to discrepancies in vaccine coverage and herd immunities. In addition, some anti-vaccination movements have been noted to persuade individuals into refusing vaccines, even in historically well immunised locations. In order to investigate the effect of varying vaccine coverage, a two patch metapopulation model for measles incorporating a single dose vaccine is formulated and studied. / October 2016

No description available.

Thesis (doctoral)--Københavns universitet.

The eradication of infectious diseases has been of key interest for many years. While the World Health Organization (WHO) and other health organizations typically track the progress of disease eradication based on whether regions are meeting their eradication targets, being able to quantify and/or visually track the eradication of a disease could prove beneficial. This thesis creates the “canonical path” to the elimination of measles in the United States (US), using similar methods as defined by Graham et al. [1]. We build on preliminary work conducted to fulfill the requirements of an Honours Bachelor of Science in Integrated Science at McMaster University, and the analysis conducted by Graham et al. [1], through the investigation of the sensitivity of the path to changes in its definition, as well how the path changes when we change the characteristics of the disease. This thesis demonstrates the ability to use a canonical path on a smaller, country-level scale, by using United States (US) state level data to create the US canonical path. We also determine the model structures necessary to simulate the canonical path, which suggests that the canonical path method is most useful for eradicable diseases for which we have ample knowledge of the disease, including the natural history of infection and vaccination. We also predict how the path is affected by the pattern of seasonality and by the natural history of infection. Overall, the analysis suggests that the more this method is implemented for other countries that have eliminated measles or for other diseases for which we have achieved elimination, we may gain insight of the successes and failures of elimination strategies. This knowledge could help the WHO and other organizations improve their disease elimination and eradication strategies in the future. / Thesis / Master of Science (MSc)

Le virus de la Rougeole reste le plus meurtrier des virus contre lesquels il existe un vaccin, avec environ 350000 décès par an dans le monde. Ce virus appartient à la famille des Paramyxoviridae, qui sont des virus enveloppés de forme sphérique dont le génome est composé d’un seul brin d’ARN de polarité négative. L’élément central de la réplication et de la transcription du génome viral est le complexe, de forme hélicoïdale, entre l’ARN du virus et la nucléoprotéine. Cette association intime appelée nucléocapside a des propriétés étonnantes non encore élucidées. En effet, l’ARN des virus à ARN négatif a la particularité de n’être jamais nu, même lors des étapes de réplication/transcription nécessitant pourtant le passage de la polymérase virale. On suppose que l’interaction avec la phosphoprotéine, cofacteur de la polymérase, provoque un changement de la conformation de la nucléoprotéine pour rendre l’ARN viral accessible à la polymérase. Lorsque la nucléoprotéine est exprimée dans des cellules d’insectes, elle se fixe aux ARNs cellulaires et forme des nucléocapsides recombinantes. Les études précédentes sur d’autres virus à ARN négatif (Rage, Marbourg, Sendaï) ont montré que les nucléocapsides recombinantes sont semblables aux nucléocapsides virales. Au sein de la nucléocapside, le domaine C-terminal de la nucléoprotéine joue un rôle crucial en interagissant avec de nombreux partenaires viraux et cellulaires, notamment avec la phosphoprotéine dans les étapes de réplication/transcription du génome viral. Cependant, des observations en microscopie électronique à transmission avaient montré que les nucléocapsides recombinantes contenant la nucléoprotéine entière était trop flexibles pour envisager leur reconstruction tridimensionnelle par analyse d’image, ce qui avait conduit à les rigidifier par un traitement protéasique dont l’effet latéral est justement l’élimination du domaine C-terminal de la nucléoprotéine. Nous avons mis au point des conditions de préparation en coloration négative permettant de rigidifier la nucléocapside intacte, afin d’en calculer une reconstruction tridimensionnelle à basse résolution et de la comparer avec celle de la nucléocapside protéolysée. Nous avons ainsi montré que les nucléocapsides de la Rougeole changeaient radicalement de structure tridimensionnelle en réponse au traitement protéolytique, non seulement en terme de pas de l’hélice ou de nombre de sous-unités par tour, mais aussi au niveau de la conformation de la nucléoprotéine et de ses contacts avec les sous-unités adjacentes, ce qui n’avait encore jamais été observé aussi clairement. / Flexible helical protein polymers exemplified by actin filaments, microtubules and bacterial flagella areubiquitous in biology. Due to their size and intrinsic irregularities, the structure of these polymers cannot be solved by Xraycrystallography. Since half a century, three-dimensional (3D) reconstruction from two-dimensional (2D) ElectronMicroscopy (EM) images appears as a method of choice to solve the structure of large helical polymers. However,depending on the degree of flexibility of the analyzed helices, the 3D reconstruction process can still be a daunting task.For the most regular helices, the classical reciprocal space-based Fourier-Bessel approach can allow both to determinethe helical symmetry and to calculate 3D structures. For more flexible structures, recent “single-particle” approachesconsist in segmentation of long irregular helices into short (i.e. locally more regular) segments and their processing asasymmetrical objects with defined symmetry-imposed constraints (Egelman, 2000; Sachse et al., 2007). However, twomajor difficulties remain: the heterogeneous data must be sorted into homogeneous populations and the helical symmetryfor each population has to be determined. In the presented work, we explored various single-particle approaches,developed new analysis methods, and implemented most of them into a user-friendly processing pipeline. The targetbiological objects were helical nucleocapsids of two negative strand RNA viruses, Measles (MeV) and VesicularStomatitis Virus (VSV ; the prototype for Rabies), the latter being particularly flexible in terms of helical parameters(diameter, number of subunits per turn). Nucleocapsids are formed by the viral genomic RNA coated by thenucleoprotein and serve as a template for viral replication and transcription. To overcome the heterogeneity problem, weused 2D classification, described general processing protocols and applications for helical segments, and introduced anew classification method based on the power spectra of the images. The determination of helical symmetry(ies) wasaddressed by a novel approach relying on ab initio exhaustive search of helical parameters whereby we start from asingle 2D image, reconstruct as many 3D structures as parameters to test by cropping the image and assigning views tothe obtained segments, and calculate the cross-correlation (CC) of the reprojection of the 3D model with the initialimage. Applied to artificial data sets, the method was effectively able to detect a maximum of CC for the true symmetryparameters, but also showed intrinsic ambiguities of helical symmetry determination on which we extensively comment.Altogether, the result of this method-oriented work allowed us to address several biological questions. First, the 3Dreconstruction by negative stain EM of two forms of nucleocapsids of MeV coupled to a docking of a homologouscrystal structure enabled us to determine the orientation of the nucleoprotein and of the RNA in the nucleocapsids.Secondly, we assessed the structure of in vitro formed nucleocapsids of VSV and showed that assemblies close to thenative viral nucleocapsids can be formed in the absence of any other viral proteins, thus providing new insights into theassembly of this virus. As a perspective of this work, our pipeline of flexible helical analysis is being extended andsuccessfully used for other projects.