Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 42-50).

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 72-76).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 88-90.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 69-73.

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 55-59).

Dissertation (D.P.H.)--University of Michigan.

The roles of genes responsible for the survival and persistence of Brucella in the host and the relationship between these genes and the disease were investigated via signature-tagged transposon mutagenesis. As much as 8% of the Brucella genome is important for survival of this organism in the host. This is an unusually high number and may help to explain the chronic or persistent nature of Brucella infections. Mutants attenuated in the mouse model were divided into two groups. The early mutants failed to establish infection or colonize the host. The late mutants colonized the host but failed to maintain infection. The vaccine potential of two mutants (virB10 and gcvH) that were unable to sustain infection was compared to that of a vaccine strain, S19. Survival of strain S19 in vivo was up to 12 weeks while virB10 and gcvH mutants were cleared from spleen at 8, and 24 weeks post-inoculation, respectively. Mice were vaccinated with individual mutants and then challenged with virulent S2308 at 8, 16, and 24 weeks postvaccination. As a result, protective immunity correlated with persistence of the mutant strain [gcvH>virB10]. These results suggest that survival is one of several factors that may influence protective immunity making it difficult to compare strains. For example, examination of host immune response revealed a similar pattern of host immune function (TH1 over TH2) in all mice except those vaccinated with virB10 mutant. Since gcvH mutant provided the best immunity, experiments were designed to explore its contribution of persistence to protection. In an effort to reduce non-specific activation induced by prolonged survival of gcvH mutant, protection was monitored after different periods of vaccination exposure followed with doxycycline treatment. In these studies, persistence of gcvH mutant enhanced protection against challenge. Overall, defined mutations in genes affecting survival may render mutants as vaccine candidates capable of stimulating protective immunity equal to or better than fortuitously isolated attenuated strains. Future studies should focus on characterization of these and other genes responsible for the persistence of Brucella to improve the safety and efficacy of live vaccines.

Brucella melitensis is the etiological agent of brucellosis, a zoonotic disease characterized by abortions in ruminant animals and a chronic debilitating disease in humans. Despite genome sequencing, little is known about the genetic elements behind Brucella s ability to survive and cause disease. Regulatory networks provide the ability to adapt to changing environments by initiating expression from specific regulons to provide adjustments to metabolism and mechanisms that enhance survival. Little detail is known about transcriptional networks that exist in Brucella, but are of great interest because they could provide information about genetic loci that contribute to virulence and intracellular survival. Transposon mutagenesis identified gene loci that are indispensable for the intracellular replication of B. melitensis, including virulence genes, metabolic defects, and transcriptional regulators. Two transcriptional regulators of interest were identified, MucR and VjbR. VjbR is a LuxR homologue and is associated with the regulation of virulence genes in a density dependent manner in a number of bacterial pathogens, and is consistent with VjbR regulation of virulence genes in B. melitensis. Microarray analysis of vjbR and a potential activating signal C12-HSL revealed that both regulate numerous putative virulence genes, including adhesins, proteases, protein secretion/translocation components, potential effector proteins, lipoproteins, a hemolysin and stress survival aids. This analysis also revealed that C12-HSL is not an activating signal of VjbR, but instead acts to suppress VjbR activity. MucR is a transcriptional regulator shown to regulate exopolysaccharide synthesis in the closely related Rhizobiales. Microarray analysis of a mucR mutant in B. melitensis suggested that MucR contributes to the regulation of nitrogen metabolism and iron sequestering/storage. MucR was also found to regulate genes involved in stress response, regulating several proteases that may contribute to enhanced survival and virulence of the organism. This work identified approximately 1,000 genetic loci that may be important to the survival of B. melitensis, revealing potential virulence genes and metabolic defects. Interruption of the VjbR regulon could be a potential chemotherapeutic target for the treatment of brucellosis. Furthermore, this work describes the functions of two gene deletions that are being evaluated as novel attenuated vaccines.

Thesis (Dr. P.H.)--University of Michigan, 1933. / Title page lacking. Thesis note on p. [2]. Bibliography: p. 107; "Bibliographies": p. 115-118.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 59-63). Also available via the Internet.