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The flashcards below were created by user
mattnjaneal
on FreezingBlue Flashcards.
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viruses
- obligate itracellular parasites
- require a host to replicate
- lack cellular structure
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virion
complete virus particle in the extracellular state (outside host)
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structure of a virus
- nucleocapsid - genome - dna or rna
- capsid - protein coat or shell
- capsomere - subunit to build capsid
- envelope - lipid bilayer, host derived when the virus exits
- spikes (peplomers) - viral proteins, used for attachment to host
- enzymes - aid infection process
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3 virus enzymes
- 1. neuraminidase - breaks down glycoproteins and glycolipids; penetrate mucous, spread
- 2. hemagluttinin - attach to host cell receptors, includes RBC's
- 3. reverse transcriptase - vRNA which makes a molecule of vDNA
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viral capsid shape
- icosahedral - 20 icosahedral triangles
- helical capsid - cylindrical, DNA coiled inside
- complex - includes bacteriophages
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viral replication - replication of bacteriophages
- 1. attachment - host specific
- 2. penetration - injects nucleic acid
- 3. biosynthesis - make capsid protein & copies of the genome
- 4. maturation - assembly, self directed
- 5. release - lysis of host cell to release new virions
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viral replication - replication of animal viruses
- 1. attachment (adsorption) - host specific; tropism = affinity for (neurotropic virus means affinity for nervous tissue)
- 2. penetration - 2choices a) host - phagocytize the virus; receptor mediated endocytosis. b) fusion of viral envelope with host cell membrane
- 3. biosynthesis - early proteins, proteins involved with replication; late proteins - capsid protein
- 4. maturation
- 5. release - 2 ways, depends on naked vs. enveloped. naked viruses - released by host cell lysis. enveloped virus - bud off of the host cell.
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viral lytic cycles
virus released
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viral lysogeny
viral DNA lays dormant in a host cell. Latent or dormant in CNS. ex: VZV - varicella zoster virus.
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classification of virus
- by family (ex: veridae)
- by genus (ex: herpes)
- by species (ex: 1 or 2)
- ex: HSV1
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3 forms of virus cultivation
- living animals - infect mice, rabbits, guinea pigs, etc
- embryonic eggs - grow virus in fertilized chicken eggs; may infect chick or membrane
- tissue cultures - homogenize and separate cells in a tissue
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viral tissue histology
viral infection can cause changes in host cell. CPE's - cytopathic effects. ex: rabies virus - leaves negri bodies in cytoplasm
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immunoassays
- titer - determine amount of virus in sample
- elisa test kit - color change when substrate is added to a positive test. ELISA = Enzume linked immunosorbent assay
- lates bead agglutination - anti vrus clumpls together
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plague formation
plague - zone of host cell lysis; holes formed by virus
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host defenses against virus
- phagocytes - engulf and destroy viruses
- T lymphocytes - CD8+ cells, killer T cells, recognize and destroy viral infected host cells
- Interferon - chemical released by viral infected cells, signals neighboring cells to produce anti viral protein; recruits natural killer cells
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antiviral medications
- base analogs - mimic nucleotides, so when a virus inserts a base analog replication stops
- reverse transcriptase inhibitors - treating retroviral infections
- protease inhibitors - viral mRNA- protease, cut the polypeptide
- neuraminidase inhibitors - disrupt the release of virus (progeny)
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viral vaccines - immunization
- inactivated (killed) - treat the virus with formaldehide to inactivate
- attenuated - weakened strain, infected without symptoms
- viral subunits - proteins from surface
- DNA vaccines - shoot the beads into muscle, muscle cells express the viral DNA
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chemical inactivation of a virus
- formaldehyde - denatures protein
- lipid solvents - detergents - effective against enveloped viruses
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physical inactivation of a virus
- heat - denatures protein
- UV radiation - disrupt nucleic acid
- X rays - disrupt nucleic acids
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subviral particles -
- smaller than viruses but cause infection; no capsid or genome
- viroid - plant pathogens, consist of small RNA genome, insects transmit between plants
- prion - proteinaceous infectious particle.
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prion disease
- spongiform encephalopathy
- degeneration of brain tissue
- PrPc - normal protein in brain tissue
- PrPsc - improper folding, builds up in tissues, affects structure of brain tissue
- Kuru - cannibalistic tribe
- BSE - bovine spongiform encephalopathy- mad cow disease
- scrapie - sheep
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transformation
- healthy cells become cancerous
- proto-oncogenes; genes that regulate cell growth and differentiation; vDNA take over control of gene. ex: HPV triggers cervical cancer
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