Ch 4: Viruses Flashcards
+ sense aka
+ sense = coding strand = mRNA
- + sense RNA = +RNA, can be used itself as mRNA (bc the coding strand = mRNA
- after the RNA polymerase is made, -RNA is made which also serves as a template to make more +RNA
+RNA retroviruses: mRNA is transcribed from the sDNA intermediate
- sense aka
- sense = template strand
- (-)DNA strand of genome serves as template to make mRNA
- (-)RNA viruses the -RNA serves as the template for transcribing more +mRNA (brings its own RNA polymerase with it)
all naked capsid viruses have what structure
- all naked capsid viruses are icosahedral
- naked viruses have a protein coat
all helical viruses are
- enveloped, there are no naked helical viruses
- enveloped viruses are covered in host membrane w/ virus specified glycoproteins (critical for infectiousness of viral progeny)
- enveloped viruses are inactivated by heat/detergents/acids, etc bc the lipid envelope holds the glycoproteins essential for attachment. Dissolving the envelope inhibits attachment and therefore uptake.
DNA viruses (encapsulated) in order from largest to smallest
- poxvirus
- herpesvirus
- hepadna
naked DNA viruses in order from largest to smallest
- adenovirus
- polyoma, papilloma
- parvovirus
RNA viruses (encapsulated) in order from largest to smallest
- paramyxovirus
- rhabdovirus
- orthomyxovirus
- coronavirus
- togavirus
- flavivirus
naked RNA viruses (in order from largest to smallest)
- reovirus
- calicivirus, hepevirus
- picornavirus
arthropod-borne viruses (insect vector) aka
arboviruses
HIV receptors on host cell
- CD4
- CCR5 (macrophage)
- CXCR4 (Th cells)
- target cells: Th cells, macrophages, microglia
receptor for rabies virus
Ach receptor
release of naked viruses
- naked viruses lyse the host cells
- thus there are no persistent productive infections w/ naked viruses (only cytolytic productive or latent infections)
release of enveloped viruses
- budding leads to cell senescence (aging) but cells may produce a low level of virus for years (HepB)
- the glycoproteins on the enveloped viral surface = essential for viral infectivity
interferon
- made by infected cells for uninfected cells
- production of IFN (and most immunologic cytokines) is under control of transcription factor NFκB
- inhibits viral protein synthesis by:
1. through activation of an RNA endonuclease, which digests viral RNA
2. by activation (via phosphorylation) of protein kinase that inactivates eIF2, inhibiting viral protein synthesis - exogenous IFN (made via recombination technology) may be used in antiviral therapy for chronic, active HBV and HCV infections
- therefore virus can’t replicate and can be killed
Which Hep viruses are transmitted fecal/orally?
- “vowels in the bowels” A and E are from something you ate.
- these are both naked viruses
- Hep B, C, D are all enveloped
- HAV = “infectious Hepatitis”; Acute (A = Acute)
- HEV = “enteric hepatitis” HEV is extremely serious in pregnant patients!
- HBV “serum”; both acute and chronic (B=Both)
- HCV “post-transfusion” is chronic (C= Chronic)
DNA viruses 3 exceptions
- all DS except parvovirus
- all icosahedral, except poxviruses = brick-shaped complex
- all replicate their DNA in the nucleus, except poxvirus (poxviruses have a virion-associated transcriptase (DNA dependent RNA polymerase) so it can transcribe its own NA in the cytoplasm and make all of the enzymes and factors necessary for replication of the poxvirus DNA in the cytoplasm.
Mnemonic for DNA viruses
Pardon Papa As He Has Pox Par: parvovirus P: papillomavirus, polyomavirus A: Adenovirus He: Hepadnavirus H: Herpes virus Pox: Poxvirus