Lecture 17: Viruses Part 1

Question 1

Virus to bacteria genetic transfer

Answer 1

Transduction

Question 2

Virus therapeutic roles

Answer 2

-Phage therapy
-Genetic therapy
-Oncolytic viruses
-Vaccination

Question 3

Obligatory intracellular pathogen

Answer 3

Can only replicate by infecting a host cell

Question 4

Virus size

Answer 4

~20-300nm

Question 5

Structure of a virus

Answer 5

•A protein shell-Capsid/capsomere/nucleocapsid (capsomere make up capsid)
•Generic material-RNA or DNA inside capsid

Question 6

Viral proteins

Answer 6

-Structural proteins
-Regulatory proteins

Question 7

Structural proteins

Answer 7

•Proteins that make up the viral capsids (the protective protein shell of the virus) & other structural components in the virion

Question 8

Regulatory proteins

Answer 8

•Enzymes-polymerases, helicases
•Transcription factors
•Other proteins that influence host cell functions to make the environment more suitable for viral production

Question 9

Example of a regulatory protein

Answer 9

T-antigen in polyomaviruses
-can cause cancer

Question 10

Retrovirus proteins

Answer 10

-Matrix
-Capsid
-Nucleocapsid
-Protease
-Reverse transcriptase
-Integrase
-Surface glycoprotein
-Transmembrane protein

Question 11

Morphology of viruses

Answer 11

-Helical viruses
-Polyhedral viruses
-Spherical viruses
-Complex viruses

Question 12

Helical viruses examples

Answer 12

-Ebola
-Rabies
-Tobacco mosaic virus

Question 13

Icosahedral (Polyhedral) examples

Answer 13

•20 sided
-HPV
-Poliovirus
-Adenovirus

Question 14

Spherical virus example

Answer 14

-Coronavirus
-Influenza
-Measles

Question 15

Complex virus

Answer 15

-Bacteriophage
-Variola virus

Question 16

Viral infection strategies-patterns of infection

Answer 16

•Acute
•Chronic/Persistent
•Latent

Question 17

Acute infection

Answer 17

Rapid and self-limiting (Colds, norovirus)

Question 18

Persistent/chronic infection

Answer 18

Lasts for months to years, but are sometimes cleared (HIV, Hepatitis B)

Question 19

Latent infection

Answer 19

An extreme version of a persistent infection that remains dormant but can become reactivated (herpes, varicella-zoster virus)

Question 20

Viral lifecycle

Answer 20

1. Attachment
2. Entry/Trafficking
3. Replication
4. Assembly
5. Release

Question 21

Goal of viral life cycle

Answer 21

Copy its genome
Translate its viral proteins

Question 22

Attachment

Answer 22

Viral attachment proteins on virus interact with specific molecules on the cell surface called viral receptors and co-receptors

Question 23

Tropism

Answer 23

Preferential targeting of a specific host species or cell type. This is determined by host cell factors (such as receptors)
-Receptors are the most important determinant of tropism

Question 24

Permissive

Answer 24

The ability of a virus to enter a host cell & complete an infection cycle

Question 25

Host range

Answer 25

Determined by specific host attachment sites and other cellular factors

Question 26

Influenza receptor expression

Answer 26

*Influenza uses sialic acid as a viral receptor -Bird influenza uses α(2,3)-linked SA -Human influenza uses α(2,6)-linked SA

Question 27

Entry

Answer 27

Steps required to bring viral cargo into the host cell

Question 28

Entry processes

Answer 28

•Endocytosis •Fusion •Penetration

Question 29

Entry processes part 2

Answer 29

•Trafficking -Movement of the virus from the surface to the site of replication (Microtubules often help shuttle the virus) •Endosomal escape •Uncoating -Disassembly of the virus to be able to release genetic material

Question 30

Replication

Answer 30

•Making copies of the viral genome -Can either use host or viral enzymes to facilitate this, depending on the virus

Question 31

Linnaeus taxonomy of Viruses

Answer 31

•Family names end in -*viridae* •Genus names end in -*virus* •Species -A group of viruses that share the same genetic information and ecological niche (host) •Subspecies are designated by a number

Question 32

Multiplication of DNA virus

Answer 32

1. Virion attaches to host cell 2. Virion enters cell, and its DNA is uncoated 3. A portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins 4. Viral DNA is replicated, and some viral proteins are made 5. Late translation; capsid proteins are synthesized 6. Virions mature 7. Virions released