The interplay between nidoviruses and the infected host cell was investigated. Arterivirus RNA-synthesising activity was shown to depend on intact membranes and on a cytosolic host protein which... Show moreThe interplay between nidoviruses and the infected host cell was investigated. Arterivirus RNA-synthesising activity was shown to depend on intact membranes and on a cytosolic host protein which does not cosediment with the RTC. Furthermore, the immunosuppressant drug cyclosporin A (CsA) blocks replication of EAV and the swine arterivirus PRRSV in cell culture. Cyclophilin A appears to be an important host factor for EAV replication. CsA may be a nidovirus-wide inhibitor of replication since this compound also blocked replication of the coronaviruses SARS-CoV, HCoV-229E, and MHV. We further described a kinase siRNA library screen that identified ninety antiviral and forty proviral hits and signalling pathways involved in the SARS-CoV replicative cycle. PKR (antiviral) and COPB2 (proviral) were validated in follow-up experiments. We also investigated MERS-CoV replication characteristics and we described an assay t o screen for compounds that block MERS-CoV infection. CsA and pegylated IFN-_ (PEG-IFN) significantly inhibited infection, and MERS-CoV was shown to be much more sensitive to PEG-IFN treatment than SARS-CoV, an observation that may have implications for the treatment of MERS-CoV infection. The data presented in this thesis might contribute to better understand virus replication and hopefully provide additional starting points for the development of antiviral strategies. Show less
Type I immune responses play an essential role in the control of mycobacterial infections. Mutations in the genes involved in the type I cytokine pathway were found in patients with Mendelian... Show moreType I immune responses play an essential role in the control of mycobacterial infections. Mutations in the genes involved in the type I cytokine pathway were found in patients with Mendelian susceptibility to mycobacterial diseases. These patients are highly susceptible to infections with non-tuberculous mycobacteria (NTM), which are usually poorly pathogenic. The first part of this thesis focuses on the relation between the genotype and phenotype in the cause of an impaired immunity leading to the susceptibility to NTM infections. The role of genetic factors in the control of infections with more virulent tuberculous mycobacteria is less evident. The second part of this thesis focuses on putative non-genetic causes of an impaired immunity in the control of tuberculous mycobacterial diseases. In tuberculosis patients type I immune responses regulated by interferon-_ are also repressed. Virally induced interferons, other than interferon-_, may be involved in this repression, thereby influencing the immunopathogenesis of tuberculosis. Show less
