The host response to infection with pathogenic and non–pathogenic mycobacteria: a proteomics approach

Mahlobo, Precious Zama (2018-11)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Tuberculosis (TB) continues to be a major health problem worldwide. In 2017, 1.6 million TB associated deaths were reported (WHO, 2017). The etiological agent of TB disease is Mycobacterium tuberculosis (Mtb), and is a highly successful pathogen due to its ability to persist in the host. The immune system uses the non-specific innate immunity as the first line of defence against invading pathogens. The interplay between macrophages and mycobacteria is not yet fully understood. Mass spectrometry is one of the most effective tools for identification and quantitation of proteins from complex mixtures of biological samples. It has been shown that mycobacteria cultured in detergent medium and detergent-free medium induce differential macrophage host response. Following on a study that identified differentially expressed genes using high-throughput RNA sequencing, we aimed to identify and quantify protein expression of murine bone marrow derived macrophages infected with non-pathogenic mycobacteria, Mycobacterium smegmatis, Mycobacterium bovis BCG, and pathogenic mycobacteria, Mycobacterium tuberculosis H37Rv and Mycobacterium tuberculosis R179 grown in a detergent-free medium. The differential proteomes of C57Bl/6 cells in response to Mtb infection, were analysed at 12 hours post infection using liquid-chromatography-tandem mass spectrometry (LC-MS/MS). Four proteins MYH9, TLN1, AHNAK and GAL-3 were expressed by pathogenic mycobacteria. Moreover, corresponding genes (Myh9, Tln1, Gal-3, and Ahnak) of the differentially expressed proteins were quantified by using quantitative PCR (qPCR) to monitor and analyse gene expression at later time points, 12, 24 & 96 hours post-infection. At the later time points, Myh9, Tln1 and Ahnak, were down-regulated indicating that these genes are only expressed at an early stage (up to 24 hours post-infection) of mycobacterial infection; while Lgal-3 was up-regulated by all slow growers (BCG, H37Rv & R179) at 96 hours post-infection. Galectin 3 is a binding protein known to control the survival of Mtb during infection. The significance of this protein can be further investigated in TB patients and healthy controls.

AFRIKAANSE OPSOMMING: Tuberkulose (TB) is steeds 'n wêreldwye gesondheidsprobleem. In 2017 is 1,6 miljoen TBgeassosieerde sterftes aangemeld (WGO, 2017). TB-siekte word veroorsaak deur Mycobacterium tuberculosis (Mtb) en is 'n hoogs suksesvolle patogeen weens die vermoë om te oorleef in die gasheer. Die immuunstelsel gebruik nie-spesifieke aangebore immuniteit as die eerste lyn van verdediging teen bakterieë. Die interaksie tussen makrofage en miobakterieë word nog nie heeltemal verstaan nie. Massaspectrometrie is een van die mees effektiewe gereedskap vir die identifisering en kwantifisering van proteïene uit komplekse mengsels van biologiese monsters. Ons poog om proteïenexpressie in beenmurgmakrofage te identifiseer en te kwantifiseer, geïnfekteer met nie-patogene miobakterieë (Mycobacterium smegmatis, Mycobacterium bovis BCG) en patogene mycobacteria (Mycobacterium tuberculosis H37Rv en Mycobacterium tuberculosis R179). Die differensiële proteïene van C57B1 / 6-selle in reaksie op Mtb-infeksie is 12 uur na infeksie geanaliseer met behulp van vloeibare chromatografie-tandem-massaspektrometrie (LC-MS / MS). Vier proteïene MYH9, TLN1, AHNAK en GAL-3 word uitgedruk deur patogene miobakterieë. Daarbenewens word die ooreenstemmende gene (Myh9, Tln1, Gal-3 en Ahnak) van die differensiaal-uitgedrukte proteïene gekwantifiseer met behulp van kwantitatiewe PCR (qPCR) om uitdrukkingsveranderinge te monitor op latere tydspunte, 12, 24 en 96 uur na infeksie. Die latere tydspunte het getoon dat Myh9, Tln1 en Ahnak slegs tydens vroeë ure van infeksies uitgespreek is; terwyl Lgal-3 opgegradeer word in makrofage geïnfekteer met BCG, H37Rv & R179 met 96 uur infeksie. Dit is bekend dat Galectin 3 'n bindende proteïen is wat bekend is om die oorlewing van Mtb tydens infeksie te beheer. Die rol van hierdie proteïene kan verder ondersoek word in TB-pasiënte en gesonde deelnemers. Dit sal ons in staat stel om die rol van hierdie proteïene tydens TB infeksie ten volle te verstaan.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105179
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