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Title: The role of interferon in Semliki Forest virus encephalitis
Author: Breakwell, Lucy
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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This thesis explores the importance of IFN in SFV encephalitis. A quantitative PCR assay for IFN-β and IFN-α transcripts and a quantitative IFN bioassay were developed to determine differences in IFN expression under different infection conditions. Mouse models and primary cell lines were used to establish the importance of PKR for IFN=β expression during SFV infection and to determine whether SFV nsP2 has a role in modulating IFN responses. In the absence of PKR, at early times post-infection, cultured cells reproducibly produced significantly lower levels of IFN-β transcripts. Reduced levels of functional IFN were also demonstrated by bioassay. Previous data has shown that PKR is not required for IFN-β induction. The sensitivity of the qPCR assay has allowed the demonstration that PKR, although not critical for IFN induction, is involved in IFN-β induction and is particularly important at early time points post infection. SFV-nsP2 has been postulated to be involved in IFN interference. Comparing SFV4 to SFV4-nsP2-RDR (a mutant virus with a single amino acid change within the nuclear localisation signal of nsP2, which prevents its translocation into the nucleus) demonstrated that relative to the number of infected cells, the SFV4nsP2-RDR mutant induced over ten –fold more IFN-β transcripts than the wildtype SFV4 strain; this upregulation was specific to IFN-β. The IFN bioassay results supported this data; SFV4-nsP2-RDR induced higher functional IFN levels in comparison to wt SFV4. Both viruses grew to similar titres and at similar rates. In the mutant and wt infections both NF-κB and IRF-3 translocated into the nucleus; however, preliminary EMSA data has suggested that the amount of NF-κB and IRF-3 translocated into the nucleus; however preliminary EMSA data has suggested that the amount of NF-κB bound to the IFN-β promoter is reduced during a wt infection. This suggests a possible mechanism for the differential IFN expression and represents the first IFN evasion mechanism described for an alphavirus.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available