Effects of Poliovirus Infection On Mitochondrial Function.

Enteroviruses have a tropism for muscle cells and have been linked to the development of CFS. Muscle abnormalities made worse by exercise are one of the major symptoms in CFS and abnormalities in cellular energy levels suggestive of an impairment of mitochondrial function have been reported following virus infection. A mitochondrial disorder precipitated by a virus infection has been suggested as the cause for the unexplained fatigue in CFS. The work presented in this thesis provides a potential link between CFS and viral infection by suggesting that the energy abnormalities in patients diagnosed with CFS may be due to a virus-induced impairment of the mitochondrial electron transport chain. A novel effect on cellular respiration caused by poliovirus infection was shown. The effect of poliovirus infection on mitochondrial function was investigated in COS-1 and T47D mammalian cells. In both cases a rapid decrease in total cell respiration was observed, and this was attributed to an inhibition of mitochondrial respiration. In parallel with the inhibition of mitochondrial respiration, the activity of succinate dehydrogenase was impaired during poliovirus infection. This shows that poliovirus-induced inhibition of cellular respiration occurs primarily through inhibition of electron flow at complex II of the mitochondrial respiratory chain. Infected cells also showed increased staining with the fluorescent lipophilic cationic mitochondrial probe tetramethylrhodamine ethyl ester showing that the impairment of respiration does not lead to a collapse of mitochondrial membrane potential and mitochondrial permeability transition pore opening. The involvement of the poliovirus non-structrural proteins 2B and 2BC was also investigated. Expression of 2B, but not 2BC, in COS-1 cells also caused a significant increase in mitochondrial membrane potential indicating that 2B may be responsible for the increased mitochondrial membrane potential during poliovirus infection. Additionally, work to generate antibodies specific for these proteins was initiated in order to investigate their intracellular localisation

Effects of Poliovirus Infection On Mitochondrial Function.

Enteroviruses have a tropism for muscle cells and have been linked to the development of CFS. Muscle abnormalities made worse by exercise are one of the major symptoms in CFS and abnormalities in cellular energy levels suggestive of an impairment of mitochondrial function have been reported following virus infection. A mitochondrial disorder precipitated by a virus infection has been suggested as the cause for the unexplained fatigue in CFS. The work presented in this thesis provides a potential link between CFS and viral infection by suggesting that the energy abnormalities in patients diagnosed with CFS may be due to a virus-induced impairment of the mitochondrial electron transport chain. A novel effect on cellular respiration caused by poliovirus infection was shown. The effect of poliovirus infection on mitochondrial function was investigated in COS-1 and T47D mammalian cells. In both cases a rapid decrease in total cell respiration was observed, and this was attributed to an inhibition of mitochondrial respiration. In parallel with the inhibition of mitochondrial respiration, the activity of succinate dehydrogenase was impaired during poliovirus infection. This shows that poliovirus-induced inhibition of cellular respiration occurs primarily through inhibition of electron flow at complex II of the mitochondrial respiratory chain. Infected cells also showed increased staining with the fluorescent lipophilic cationic mitochondrial probe tetramethylrhodamine ethyl ester showing that the impairment of respiration does not lead to a collapse of mitochondrial membrane potential and mitochondrial permeability transition pore opening. The involvement of the poliovirus non-structrural proteins 2B and 2BC was also investigated. Expression of 2B, but not 2BC, in COS-1 cells also caused a significant increase in mitochondrial membrane potential indicating that 2B may be responsible for the increased mitochondrial membrane potential during poliovirus infection. Additionally, work to generate antibodies specific for these proteins was initiated in order to investigate their intracellular localisation

p16INK4A-independence of Epstein–Barr virus-induced cell proliferation and virus latency

Epstein-Barr virus (EBV) has the ability to promote cell cycle progression following the initial infection of primary resting B-lymphocytes and to cause cell cycle arrest at the onset of the viral replicative cycle. Various mechanisms have been proposed for the proliferative effects, including the up-regulation of cyclin D2 by the viral EBNA-2 and EBNA-LP proteins, direct binding of EBNA3C to the retinoblastoma protein (pRb), and down-regulation of the p16(INK4A) tumour suppressor by the viral LIMP1 product. To try to gain insight into the relative importance of these mechanisms, the ability of EBV to immortalize lymphocytes from an individual who is genetically deficient for p16(INK4A) was examined. From detailed analyses of the resultant lymphoblastoid cell lines it is concluded that p16(INK4A) status has little bearing on EBV's ability to manipulate the cell cycle machinery and a model to accommodate the previously proposed routes taken by EBV to bypass the restriction point is presented