L35 - intro to virology

Question 1

outlines

Answer 1

• principles of virus structure and classification
• different stages and outcome of viruses
• life cycle of HIV
• basics of viral vaccines

Question 2

properties of viruses

Answer 2

1. obligate intracellular
2. host specific
3. one of the smallest biology entities (30-400nm)
4. genome size varies from 3.2kb (4 genes) to 1.2Mb (911 genes)

Question 3

what does it mean by viruses are obligate intracellular?

Answer 3

• can’t grow or replicate outside host (can’t live on their own)
• don’t acquire nutrients, produce energy or synthesise proteins

Question 4

how are viruses classified?

Answer 4

• type of nucleic acid
• morphology
• presence/ absence envelope
• host organism

Question 5

viral genomes of DNA viruses

Answer 5

• ssDNA
• dsDNA

Question 6

viral genomes of RNA viruses

Answer 6

• single stranged
• double stranded

Question 7

viral genomes of RNA <–> DNA viruses

Answer 7

• single stranded
• double stranded

Question 8

structure of naked viruses

Answer 8

• no outer membrane e.g polio virus
• very simple
• shell of protein filled with nucleic acid

Question 9

structure of enveloped viruses

Answer 9

• outer membrane
• derived from host cell membrane
• modified with viral proteins for recognition and attachment to host cells

Question 10

stages of viral multiplication

Answer 10

1. attachment
2. entry and uncoating
3. synthesis of viral components
4. assembly
5. release

Question 11

attachment stage of viral multiplication

Answer 11

• viruses are not motile
• initial contact from random collision
• followed by specific interaction between attachment site on viral surface and receptor on cell surface
• SARS-Cov2 - ACE2 receptor on eptithelial cells

Question 12

entry and unceasing stage of viral multiplication

Answer 12

• coupled process often
• entry through endocytosis (enveloped + naked virus)
• end-some formed and sent to lysosomes to dispose
• entry through fusion with membrane (enveloped)
• after entry of nucleic acid is prepared for expression/ replication: full or partial shedding of capsid proteins (uncoating)

Question 16

synthesis of viral components stage of viral multiplication

Answer 16

• viral nucleic acid competes with host cell for control of biological machinery
• viral mRNA produced
• mRNA directs synthesis of early proteins
• these proteins direct nucleic acid replication
• synthesis of late proteins

Question 17

assembly stage of viral multiplication

Answer 17

nucleic acid is either
1. packaged into preassembled capsid
2. associated with capsid proteins during formation

Question 18

release stage of viral multiplication

Answer 18

1. cytolysis: naked viruses
2. budding: enveloped, developed derived from plasma memb

Question 19

how are viruses released by cytolysis?

Question 21

release by budding

Answer 21

• virus makes contact with memb
• memb wraps around virus
• piches off
• releases fully formed virus particle
• memb is modified with viral proteins

Question 23

outcomes of viral infection

Answer 23

• cytocidal infection (acute infections that lead to lots of cells death)
• chronic infections (slow cell death)
• latent infection (infection has no symptoms for a while, something triggers it)
• transforming infections (cancers)

Question 26

live vaccines

Answer 26

• using attenuated (weak, normal viruses) strains
• can replicate

Question 27

killed vaccines

Answer 27

viruses killed by heat or chemicals

Question 28

component vaccines

Answer 28

• isolated from whole virus particles
• produced by recombinant DNA technology

Question 29

vector vaccines

Answer 29

viral vector carrying component from pathogen

Question 30

mRNA vaccines

Answer 30

mRNA encoding antigen introduced into tissue

Question 31

DNA tissue

Answer 31

introduction of plasmid encoding antigen into tissue

Question 32

production of virus particles

Answer 32

1. cell cultures
2. embryonate hen eggs

Question 33

production of viruses via cell cultures

Answer 33

• infect mammalian cell line with virus
• isolate and purify virus particles