Viral Pathogenesis II Flashcards
Viruses
Small Have a protein coat Some have an envelope Can have an RNA or a DNA genome Replicate by assembly
Localized vs Systemic
Localized spread: mucosal surface
Replication and spread:
Mucosal surface to blood
Mucosal surface to neurons
Consequences of Infection
No clinical presentation Acute disease resulting from viral replication Persistent/Latent infection Immunopathological reaction Altered development
Lytic Infection
Destroy cells
Example: rhinovirus
Perfusion of cytokines and fluid release and nose start running
Hyperchromic cells, nuclei condense, and cytoplasm doesn’t exist because respiratory epithelial layers have holes in it
Syncytium Formation
A mass of cytoplasm having many nuclei but no internal cell boundaries from cell fusing together due to enveloped viruses
Example: HIV
Surface glycoproteins on envelop attach to membrane of the host cell and causes fusion of cell membrane and envelop
Infected host cell, will make new viral glycoproteins and insert them into cytoplasmic membranes of the cells
Cells that are touching each other can then fuse via glycoproteins
Leads to giant cell as a result of fusion of many cells
Hyperplasia
Changes the cell type
Loss of contact inhibition: viral proteins interfering with cell cycle control and cells are replicating at an abnormal level
Examples: Epstein Barr Virus and Papilloma virus
Cell Cycle: G1, then synthesis of DNA (chromosome is duplicated), G2 (another growth cycle), and then mitosis
G0 is a resting phase
Transformation
Can cause cancer
Example: HTLV: T cell leukemia (human T lymphotrophic virus)
Immunopathological Reaction
Scheme of immune response
Scarring of infectious eye with virus from immune reactions
Immune reactions have good and bad associations with them
Persistent/Latent Infections
Herpes simplex virus
Measles
Have a peak number of virions with the acute infection, but because a few survive, they start to replicate again causing a persistent infection that eventually escalates into a latent infection with a lower peak (compared to acute infection stage) of virion number
Altered Development
Rubella virus, cytomegalovirus
Hearing loss, blueberry muffin baby (petechiae), targets heart and eyes = Rubella
Virus Host Range, Virulence, and Number of Particles
Virus host range - humans, animals, age ranges
Viral virulence- ability to cause disease and strength of ability to infect
Number of viral particles present in inoculum: small amount vs. large amount needed; the less the more virulent
Viruses can change in their ability to cause disease
Vaccine Development
Inactivated: killed virulent virus; B cell response
Attenuated: replicating, avirulent virus; T cell response (but also B cell); provides greater protection
Subunit: proteins grown in yeast from the virus; B cell response
Interferon Production
Produced by a virally infected cell
Induces an antiviral state: synthesis of oligoadenylate synthetase and protein kinase
Virus attaches to a cell, particle enters, and then starts to replicate
Double stranded RNA: RNA viruses must go through a double stranded intermediate to replicate
Virus starts to replicate and produces double stranded RNA and causes the host cell to synthesize interferon, which is secreted into outside environment
Interferon Reactions
Interferons goes to neighboring cells that aren’t infected and bind to interferon receptors to cause the cell to go into an anti-viral state
Cascade of events produces oligoadenylate synthetase and protein kinase
Double stranded RNA will activate oligoadenylate synthetase and protein kinase in other cells, and these proteins go on to have enzymatic activity
Oligoadenylate- degrades mRNA
Protein kinase: inhibition of formation of protein synthesis initiation complex
Overall it all prevents protein synthesis so that way viral replication cannot occur
