Gene expression of caspase-1, caspase-4 and romA in Legionella pneumophila infected THP-1 cell

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Gene expression of caspase-1, caspase-4 and romA in Legionella pneumophila infected THP-1 cell


Author: Lam, Pui Ying
Title: Gene expression of caspase-1, caspase-4 and romA in Legionella pneumophila infected THP-1 cell
Degree: M.Sc.
Year: 2016
Subject: Legionella pneumophila.
Gene expression.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: x, 58 pages : color illustrations
Language: English
InnoPac Record:
Abstract: Legionnaires' disease is one of the public health concern diseases nowadays. Increasing Legionnaires' disease cases were reported annually from different counties of the world. The most common cause of Legionnaires' disease is Legionella pneumophila, which is survived in artificial water system and infect human by contaminated aerosols. Once infected, the antimicrobial response of human is begun with canonical and non-canonical inflammasome pathway through caspase-1 and caspase-4 activation respectively. At the same time, L. pneumophila survived from the cell death pathway of human immune system by forming Legionella containing vacuole (LCV) and translocated bacterial effector into the host cell by Dot/Icm type IV secretion system. romA is one of the bacterial effector recently identified. It previously showed repression on host cell gene expression and promotion intracellular replication of L. pneumophila by trimethylated K14 of histone H3. As romA was newly identified, the details of its effect and the pathway involved is not fully understands. In this study aimed to determine the gene expression of romA, caspase-1 and caspase-4 during different growth phases of the Legionella pneumophila infected THP-1 cells. It also determined the correlation between expression of romA and caspase-1 or caspase-4. Two sets of L. pneumophila infected THP-1 cells were prepared. The infected cells were removed every 12 hour intervals and their total RNA was extracted. The contaminants genomic DNA in RNA extract was digested with DNase treatment and the purified RNA was converted to cDNA by Reverse Transcriptase - Polymerase Chain Reaction. The target genes expression was studied by Real-Time Polymerase Chain Reaction with appropriate primers and probes. 2ΔΔCT Method was used in calculation of fold change of romA, caspase-1 and caspase-4 expression. There was no significant difference in gene expression of the target genes on different phases of life cycle of infected cells. This study suggested that romA, caspase-1 and caspase-4 expression were not actively by L. pneumophila infection. The target genes were expressed throughout the life cylce of Legionella and the expression rate was steady at different phases.

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