| dc.description.abstract | The parallel gene expression profiles of Brucella melitensis and the host have not
been elaborated. In this study, I analyze and discuss the transcriptional profiles of B.
melitensis invasive-associated genes, the expression profile of intracellular B. melitensis
and B. melitensis-infected non-phagocytic cells in the first 12 h post-infection (PI), and
the in vivo temporal global transcriptome of both B. melitensis and the infected bovine
host in the first 4 h PI. The initial study found that B. melitensis at late-log phase of
growth were more invasive in non-phagocytic cells than at early-log or stationary growth
phase. Microarray-based studies identified 454 Brucella genes differentially expressed
between the most and the least invasive growth phases. Additionally, B. melitensis
strains with transposon interrupted in loci BMEII0380 (acrA) and BMEI1538
(hypothetical protein) were found to be deficient in internalization compare with the
wild-type strain. A second experiment was designed with the goal of characterizing host
and pathogen transcriptome in parallel. For detecting intracellular Brucella gene
expression, a combined protocol consisting of a linear amplification of sense-stranded
RNA biased to pathogen transcripts to the previously enriched host:pathogen RNA mixed sample, was developed. RNA samples were hybridized on human and Brucella
cDNA microarrays, which analysis revealed a common down-regulation transcriptional
profile at 4 h PI that was reverse at 12 h PI. The integrity of B. melitensis virB operon
and the expression of host MAPK1 were confirmed as critical for early B. melitensis
intracellular survival and replication in non-phagocytic cells. Finally, a temporal
morphological and molecular characterization of the initial B. melitensis:bovine host
interaction using a calf ileal loop model was performed. B. melitensis was isolated from
intestinal Peyer’s patches as soon as 15 min and from systemic blood after 30 min postintra
luminal inoculation. Microarray results revealed a common transcriptional profile
in Brucella, but two different transcriptional profiles were identified in the host in the
first 4 h PI. The importance of differentially expressed biological processes, pathways
and individual genes in the initial Brucella pathogenesis is discussed. | en |
