Intro to Virology

Question 1

some viruses have lipid envelopes, which are derived from….

Answer 1

host membrane (cell, organelle, etc)

Question 2

what is the contained in the nucleocapsid (core) of a virion?

Answer 2

nucleic acid (RNA OR DNA, not both) and protein capsid

Question 3

where are glycoprotein spikes found in virions?

Answer 3

glycoprotein spikes are found in the envelope (lipid bilayer, host-derived)

viruses can only infect cells that have a receptor for their glycoprotein spike

Question 4

by convention, what is (+)strand RNA vs (-)strand RNA in classifying viruses?

Answer 4

(+)strand = message strand
(-)strand = opposite

Question 5

icosohedral nucleocapsid

Answer 5

20-faced structure of virion

protomer = protein subunits
capsomere = made up of protomers

*note that if virion does not have lipid envelope, proteins sticking out of the icosohedral capsid will serve as spike proteins that bind host receptors

Question 6

what are 3 shapes virion nucleocapsids can have?

Answer 6

1. icosohedral (20 faces)
2. helical
3. complex

Question 7

what are the steps of viral replication? (5)

Answer 7

1. spikes (proteins or glycoproteins) bind receptors already present (not meant for viruses)
2. entry via endocytosis or fusion, uncoating
3. synthesis of non-structural proteins (to make DNA/RNA)
4. genome replication, synthesis of structural proteins, packaging into nucleocapsid
5. (sometimes acquisition of envelope from host), exit cell via budding or lysis

Question 8

virions can enter host cells by either endocytosis or fusion with lipid membranes (if enveloped) - how might fusion be helpful for the immune system?

Answer 8

following fusion with plasma membrane, some spike glycoproteins are left on the cell surface and can be used as red flags for the immune system

Question 9

how to enveloped vs non-enveloped viruses typically exit cells?

Answer 9

enveloped viruses tropically exit via budding (how they acquire the envelope)

non-enveloped viruses typically exit via host cell lysis

Question 10

what is a viral plaque assay

Answer 10

tubes with monolayers of cells

viruses are added and form “punch holes” (plaques) through the monolayer of cells if they are able to infect/kill them and move to the next layer

used to determine viral concentration in the sample

Question 11

what is a hemagglutination inhibition test for viral infections?

Answer 11

to test titter in the serum of antibodies against a certain virus

some viruses are able to naturally agglutinate RBC - add RBC + antiviral antibodies from serum + viruses —> viruses are neutralized, hemagglutination is inhibited