Abstract
Classical swine fever virus (CSFV) causes a highly contagious haemorrhagic disease of pigs leading to large-scale economic losses in Europe. Acute, subacute, and chronic infections are produced depending on the virulence of the strain and host genetic factors. CSFV is a small enveloped-positive-strand RNA virus classified in the Pestivirus genus of the Flaviviridae. The generation of a persistent infection suggests CSFV is able to modulate innate immune responses and/or apotosis. CSFV shares many similarities with the human pathogen hepatitis C virus (HCV) which also causes persistent infections. The core (capsid) protein of HCV is a multifunctional protein able to modulate cellular transcription, signal transduction pathways, and contribute to viral immune escape. This thesis has carried out a yeast two-hybrid (Y2H) analysis of cellular proteins that bind CSFV core, and generated antibodies to follow its processing and its intracellular distribution. CSFV core bound proteins topors and Sp100 in the Y2H screen. These are nuclear proteins that reside in promyelocytic leukaemia (PML) oncogenic domains (PODs) and are involved in p53 ubiquitination, transcription, and DNA replication. Interestingly, Sp110b, a homologue of Sp100 and co-repressor of retinoic acid nuclear receptor retinoic α (RARα), has been shown to bind HCV core. This interaction was shown responsible for tissue transglutaminase gene activation and all-frans-retinoic acid (ATRA)-induced cell death sensitisation through cytoplasmic retention of Sp110b. CSFV core expressed alone located to nuclear dots that resemble PODs and partially co-localised with topors and Sp100 in cotransfection experiments. For HCV core, nuclear localisation requires processing and removal of the hydrophobic amino acids that form the signal peptide of E1; otherwise it binds the endoplasmic reticulum (ER). For CSFV, both the core protein fused to the signal peptide, and, a truncated form lacking this signal sequence located to the nucleus suggesting differences in protein trafficking between the two viruses.