Synopsis of MSc Dissertation project

Tuberculosis is a serious public disease, caused by Mycobacterium tuberculosis (M. tb). Thanks to its remarkable ability to cause both active and latent disease, it is a serious infectious killer worldwide. Emergence of multidrug resistant strains of the bacterium has thwarted the control of the disease. Hence, there is an urgent need for new strategies to tackle this global emergency. Host-directed adjuvant therapies are a promising strategy to achieve improved therapy outcomes and reduce the lengthy treatment period for tuberculosis. Developing host directed therapies requires a comprehensive understanding of the pathogen-host interaction interface.

Pathogens hijack and manipulate the host cell machinery and gene expression respectively in order to survive inside the host cell and cause pathogenesis. Nonetheless, there is sparse information on how pathogens achieve host cell translation control. In this project, hypothesising that M. tb affects host cell translation in human macrophages, we attempted to measure the impact of M. tb infection on global host translation and to establish how it affects host cell translation control through molecular pathways such as the MAPK signalling pathway and eIF2α phosphorylation.

THP-1 macrophages, a human monocytic cell line were used as the host cell model for M. tb infection. In this project, M. bovis BCG, a non-pathogenic surrogate for M. tb, was also used for comparisons. Initial experiments involved optimization of the experimental conditions for cell culture and infections. Having established the experimental conditions, we performed ribopuromycylation assays in order to measure host cell global translation at certain time points during infection. After acquiring initial data on the impact of M. tb on host cell global translation, we addressed the impact of M. tb infection on molecular pathways and their elements involved in the regulation of host cell translation initiation. These included the Mitogen-activated protein kinase (MAPK) pathway, eIF4E phosphorylation and eIF2α phosporylation. The aim was to observe whether there was upregulation or inhibition of the pathways or in their elements during infection and visualise the results by Western Blotting.

Overall, we attempted to shed light on the impact of M. tb infection on host cell translation, and on the mechanisms used by this pathogen in order to exert host cell translational control and cause pathogenesis. This project will fuel future studies on the response of macrophages to M. tb infection and could form the pedestal for host-directed therapy development.