Viruses and Prions - Virology Presentation PDF

What are viruses? What are they NOT?  Viruses that Infect Humans DNA Viruses RNA Viruses (7 families) (12 families) Enveloped Naked Naked Envelope...

What are viruses? What are they NOT?  Viruses that Infect Humans DNA Viruses RNA Viruses (7 families) (12 families) Enveloped Naked Naked Enveloped ds ds ss ds ss ss + r.t ss many one RNA RNA What is being used to classify the viruses? Viral Structure Capsid Nucleic acid (viral genome) Enveloped Virus Glycoproteins Helical capsid Matrix protein Envelope Enveloped virus with helical capsid Viral Shapes: Helical, Polyhedral, Complex Viruses on plant, bacterial, and human hosts  Viral Genome Contains… Genes that: – Ensure replication of the viral genome – Code for capsid proteins – Ensure packaging of genome into capsid – Alter structure/function of host Enveloped virus – Genes that code for glycoprotein spikes  5 Viral Replication Steps Attachment (to what?) Entry (into what?)/ Uncoating (of what?) Synthesis (of what?) Assembly (of what?) Release (from what?)  Bacteriophage: Viruses that Infect Bacteria Used as a model to study viruses; same 5 steps. Animal Virus Entry/Uncoating: Direct Capsid Receptors on cytoplasmic membrane Viral genome Direct penetration Animal Virus Entry/Uncoating: Membrane Fusion Viral Viral glycoproteins glycoproteins remain in Envelope cytoplasmic membrane Receptors on cytoplasmic membrane of host Viral genome Uncoating capsid Membrane fusion Animal Virus Entry/Uncoating: Endocytosis by host Cytoplasmic membrane of host engulfs virus (endocytosis) Viral genome Uncoating capsid Endocytosis  Synthesis and Assembly of Animal Viruses Synthesis: – DNA genomes: where synthesized? – RNA genomes- where synthesized? – What if the virus also has an envelope? What needs to be made? Where? Assembly/Packaging of nucleocapsid: – DNA- usually in nucleus – RNA- usually in cytoplasm  Release from the cell Naked viruses – Exocytosis – Lysis Enveloped viruses – Budding  Viral Exit/ Release: Budding of Enveloped Virus Enveloped virion Budding of enveloped virus Viral Cytoplasmic glycoproteins membrane of host Viral capsid What other membranes might an enveloped animal virus bud from?  Case Study: Influenza and SARS-CoV2 Enveloped RNA virus Enveloped RNA virus (many pieces of RNA) – (one ssRNA, like mRNA) Two important molecules on surface: Main important – Hemagluttinin molecule: – Neuraminadase – Spike protein (glycosylated) Antigenic Drift – Surface molecules change often: mutation Variants – Drift or shift? Antigenic Shift  Role of Viruses in Cancer Viruses involved in about 15% of cancers Variety of mechanisms: – Viral DNA integrated into our genome (HIV) – Activation of our oncogenes or bring their own Increase replication Increase transcription Prevent apoptosis HPV in cervical and other cancers- Everyone up to age 26 – Vast majority of cervical cancers Prions: Protein Infectious Particles What are they? – ONLY proteins – Cause progressive neurodegenerative diseases – Very stable! Basic mechanism? Diseases known as transmissible spongiform encephalopathies (TSEs) Prions: Infectious Misfolded Proteins 3 types of occurrence: Sporadic (random?) Genetic Acquired (eating) Cellular PrP Prion PrP  Prions: 3 Types of Occurrence Normal form of protein (PrPc) CJD FFI Eating BAD: PrPSC Fatal Familial Insomnia (FFI): slow conversion/accumulation of PrPSC