Topic 2: Picornavirus case study After completing the Picornavirus case study of Topic 2 in the Virology segment, students should be able to: . describe the structure of the Poliovirus capsid and genome. • explain the replication cycle of Poliovirus including: - the host cell receptor used and the cell types expressing that receptor. - how the virus genome enters the host cell. - how the virus' (ti) RNA competes with the cellular mRNA for translation by the ribosomes, and how the virus eliminates the competition. - how the virus' replicates its genome using an RNA-dependent RNA polymerase. - describe how the virus progeny assemble and are released from the host cell. - describe the process of virus maturation that results in an infectious virus particle. . describe the different types of diseases caused by Poliovirus. • describe the two types of Poliovirus vaccine, and explain the advantages and disadvantages of each type, how they are administered and the type of immunity they confer to the host. 1
Binding and entry of Poliovirus genome VP1 (blue) is the virus' 'anti-receptor' and the depression is the region that interacts with the host cell's 'virus receptor', a protein known as CD155. PVR Binding Site PVR Canyon VP1 VP4 VP2 VP3 2 http://maptest.rutgers.edu/drupal/?q=node/448
Binding of virus, entry of genome The binding of VP1 to the CD155 induces conformational changes in the capsid of the virus particle. The N-terminal end of the VP1 protein is inserted into the cell membrane to form a pore. VP4 which was inside the capsid prior to binding CD155 is now outside and may form part of this pore structure. The RNA passes through the pore and into the cell's cytoplasm. Attachement Pore-mediated penetration Cytoplasmic RNA genome Pore-mediated penetration O ViralZone 2011 Swiss institute of Bioinformatics Its not clear whether the particle actually enters the cell or just the genome - it may depend on the particular strain of Poliovirus and the cells used in the study. The key point is that a pore is generated through the lipid bilayer of the host cell. 3 http://viralzone.expasy.org/all_by_species/979.html