Electronic Theses and Dissertations (PhDs)

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    Comparison of the proteome of Huh7 cells transfected with different (sub)genotypes of Hepatitis B Virus prevailing in sub-Saharan Africa
    (University of the Witwatersrand, Johannesburg, 2024) Padarath, Kiyasha; Kramvis, Anna
    Hepatitis B Virus (HBV) is classified into nine genotypes, A to I, and at least 35 subgenotypes. In sub-Saharan Africa (SSA), (sub)genotypes A1, D3, and E prevail. Different mutations in the basic core promoter (BCP) and/or precore (PC) region that affect the expression of HBeAg can affect clinical outcomes and progression to hepatocellular carcinoma (HCC). Subgenotype A1, has high oncogenic potential and mutations affecting HBeAg expression at transcriptional, translation and post-translation levels, resulting in early HBeAg seroconversion. G1862T mutation, frequently found in subgenotype A1 HBV isolated from HCC patients, interferes with signal peptide cleavage and leads to a decreased expression of HBeAg. The effect of the SSA HBV (sub)genotypes and the G1862T mutation on protein expression and host signalling pathways has not been studied. Therefore, in this thesis Huh7 cells were transfected with replication-competent clones of (sub)genotypes A1, A2, D3 E and G1862T mutation to study the proteome using mass spectrometry. Proteomic analysis revealed significantly differentially expressed proteins between different SSA (sub)genotypes and A1 with G1862T compared to the wild-type. These differentially expressed proteins were classified into signalling pathways. The different (sub)genotypes and the G1862T mutant of HBV were shown to affect various signalling pathways involved in three hallmarks of cancer including: immune evasion and persistence, sustained proliferative signalling and genome instability and mutation. In particular, subgenotype A1 was shown to favour the dysregulation of MAPK (immune evasion and persistence) and PI3K/Akt/mTOR (sustained proliferative signalling) pathways and when accompanied by the G1862T mutation showed dysregulation of DNA synthesis pathway leading to uncontrolled proliferation (genome instability and mutation). This was the first study that demonstrated, using comprehensive proteomic analysis differences among SSA genotypes and the effect of G1862T in protein expression in vitro. It provides novel insights into the molecular underpinnings of the oncogenic potential of HBV.