Viruses Flashcards
What is a virion?
- the infectious particle of a virus
- no metabolism outside of host cells
- bind to host cells and infect them
What is a progeny?
-newly synthesized virions that are released by infected (host) cells
What is the structure of a naked virion?
- (non enveloped)
- nucleic acid (DNA or RNA)
- protein capsid
- protein spikes (proteins or glycoproteins)
What is the structure of an enveloped virion?
- lipid envelope
- nucleic acid (DNA or RNA)
- protein capsid
- protein spikes (glycoproteins)
What is a nucleocapsid made of?
-capsid+ nucleic acids
Where are the matrix proteins located?
-inside the capsid
Where is the tegument located?
-between the envelope and capsid (some enveloped viruses)
What kind of proteins are sometimes found in the matrix or tegument of virions?
- viral enzymes; necessary for virion to subvert (take over) a host cell
What makes up the viral genome?
what are the 2 types?
Nucleic acids
-monopartite and segmented
What is a monopartite? Example
- a single molecule of nucleic acid
- coronaviruses have 1 RNA molecule inside each virion
What is a segmented virus? Example?
- genome consisting of several nucleic acid molecules
- rotaviruses have 11 RNA molecules inside each virion
What is the typical size of a virion?
22-450 nm in diameter
Which cell is smaller than a virion?
-hemoglobin; 15 nm
What are the 7 steps the viral life cycle?
1) adsorption
2) Entry
3) uncoating
4) subversion
5) synthesis
6) assembly
7) exit/release
7) exit/release
What is adsorption?
-virion spike proteins bind to protein on host cell (viral receptors)
What is entry? What are some strategies viruses use to enter a cell
- nucleic acids (and other parts) enter host cell
- fusion (enveloped)
- receptor-mediated endocytosis
- injection of genome
What is uncoating?
- nucleic acids are exposed in the cytoplasm of the host cell
What is subversion?
-virus takes control of host cell to be reprogrammed to build more virions
What are the 2 goals of viral synthesis?
1) make copies of viral genome/nucleic acids
2) make viral proteins
- capsid
- spike
- viral enzymes
Look to notes on the process of viral synthesis
What are 2 viral exit (release) strategies?
- enveloped viruses bud (allows gradual, prolonged release) to exit
- naked viruses exit by lysis (release of large numbers in a short period)
What kind of viruses increase the risk of cancer?
-oncoviruses
How do some viruses increase the risk of cancer?
-the reprogramming of the host cell allows it to escape the normal controls that prevent overgrowth, promoting cancer.
-
Explain what host range is regarding viruses
- all of the species of hosts that it can effect
- ex. Influenza > people, pigs, chickens
What is tissue tropism?
- all of the cells/ tissues in a host that can be infected
- rabies > muscle cells, nervous cells, salivary glands
Characteristics of human herpes viruses
+/- DNA viruses
Enveloped
Complex tegument
Latent infections
Not a retrovirus
What are the 8 human herpes viruses?
1) herpes simplex 1 (STD)
2) herpes simplex 2
3) Varicella zoster (chicken pox, shingles)
4) Epstein- Barr (rash, swollen tonsils)
5) Cystomegalovirus (can lead to stillbirth, liver, CNS damage)
6) Roseola (fever> rash)
7) HHV 7 (fever>rash)
8) Kaposi Sarcoma Associated
What is seroprevalence?
- measures antibodies in a large group
- % of people who have antibodies vs specific pathogen
What kind of virus is herpes simplex?
-latent virus
What do you need to culture a virus in a lab?
-host cells
What are some cytopathic effects of cells
- Plaques= missing host cells
- syncytiums= fusion of host cells
- enlarged cells
Why don’t bacterial or fungal antibodies work on viruses?
- viruses use host cell enzymes to carry out reproductive process
- viruses are minimalists
- viruses use human cells
What are 3 antiviral therapies?
- nucleoside analogs
- interferons
- budding inhibitors
Name a nucleoside analog and how it works
- Acyclovir; becomes phosphorylated and is incorporated into DNA rep, creating a dead end
What is a cytokine?
-protein release by human cells; part of immune system
What is an interferon?
- type of cytokine that activate inherent antiviral defenses_
What are the different ways a interferon can defend against a virus? (3)
- attack viral mRNA
- slow protein synthesis
- increase MHC display
Name a budding inhibitor and the virus it is used to treat. How does it work?
- Neuraminidase inhibitor treats influenza.
- it greatly slows viral spread giving an advantage to the immune system
Look at notes for Life Cycle of HIV
