8.13_Viruses and Prions Flashcards
(21 cards)
Capsid protein
interacts with the viral nucleic acid, permits the nucleic acids to leave when they enter into a cell, interacts with receptors on host cells, and protects the nucleic acid
Some viruses have a nucleopcapsid that coats the nucleic acids specifically, this is seen in HIV, note they still have the capsid as well
Icosahedral viral protein
considered to be a sphere, and sort of closed so there is a limit on amount of nucleic acid it can contain
Helical viral protein
this is more rod shaped with varying widths, no real limit to amount of nucleic acids considered open
negative sense viral RNA
runs in 3-5 direction so a compliment must be made to be able to be translated
positive sense viral RNA
5-3 prime direction so can be a mRNA right away
Viral cycle steps
- attaches to cell, must have right receptor and ligand
- entry
- Uncoating
- synthesis of protein and nucleic acids
- reassembly
- exit
+ssRNA ways to get to mRNA
- makes -ssRNA so will have template to go back to, poliovirus
- HIV example, makes DNA/RNA hybrid and then dsDNA to act as template
dsDNA ways to get to mRNA
- can just be template right away, herpes
2. can go to ssRNA then mRNA Hep B
-ssRNA ways to get to mRNA
will act as template to produce mRNA, influenza and rabies
ssDNA ways to get to mRNA
goes to dsDNA, parvovirus
Importance of grouping viruses by genome type:
replication mode differs, and RNA viruses will have more errors because RNA polymerases do not have proofreading
Also important because some antivirals only attack specific types of nucleic acids
Viral genome functions
genome replication, assembly and packaging
regulation of replication cycle
Modulation of host defenses
BUT the genome does not include genes for protein synthesis machinery, metabolism, or membrane synthesis so the virus has to get its membrane from a host cell, which means it can have random proteins on the outside
Enveloped viruses
get envelope from host cell, not always the plasma membrane as it can be the golgi or another organelle, so will have host cell proteins maybe, also virus encodes for glycoproteins that will make a spike on surface of envelope, remember that acid can destroy lipids so enveloped wont be in GI
Examples are herpes and influenza viruses
Non enveloped viruses
outer covering is the capsid protein, lyse to release, survive in GI because of no lipids and can withstand heat
Examples are norovirus, rotavirus, papillomavirus
Different types of viral groupings
virus family- like herpes viruses
disease process or site of infection like hepatitis
route of transmission like blood borne and arboviruses which are from arthropods, respiratory and STD
Herpesviruses 5 types and info
Herpes Simplex virus 1- usually oral
Herpes simplex virus 2- usually genital
Varicella zoster virus- chicken pox (more contagious) and shingles
Cytomegalovirus- big cell disease, infectious mono
Epstein-Barr Virus- infectious mono
Enveloped dsDNA!!
Influenza A virus
Enveloped, -sense ssRNA in segments, segmentation has a lot to do with why we have to change the vaccine every year
HIV
is a retrovirus, which means it is an RNA and goes back to DNA in a cell, so process is RNA to RNA/DNA hybrid then DNA intermediate can integrate into host genome
Transmissible Spongiform Encephalopathies
TSEs, progressive neurodegenerative diseases, in animals you see scrapies in sheep and mad cow disease
in humans have Creutfeldt Jacob Disease and Kuru
How do Prions arise?
uncertain about what but something leads the normal folding protein to revert from an alpha helix into a beta pleated sheet therefore much more likely to have plaques, replication occurs as somehow the infectious protein matches with a normal protein and switches it
Creutfeld Jacob Disease or CJD
iatrogenic or introduced by a medical procedure via contaminated products, inherited mutation in the PrP gene, Pathogenic PrP accumulates in brain and leads to non inflammatory tissue destruction and spongy appearance…dementia
