Virology 2

Question 1

What is poliovirus

Answer 1

A single stranded positive sense RNA virus

Question 2

What family does poliovirus belong to?

Answer 2

Picornaviridae

Question 3

Picornaviridae family contains what genus’s?

Answer 3

-Rhinovirus
-Hepatorvirus
-Cardiovirus
-Apthovirus
-Entervirus

Question 4

Which genus does poliovirus belong to?

Answer 4

Enterovirus

Question 5

Serotypes of poliovirus:

Answer 5

Type 1 (PV-1)
Type 2 (PV-2)
Type 3 (PV-3)

Question 6

Structure of poliovirus

Answer 6

-Small (30nm)
-Noneveloped (Naked)
-Icosahedral capsid symmetry

Question 7

Capsid of poliovirus:

Answer 7

-The capsid is resistant to acidity and detergents
-4 components to the capsid (VP1, VP2, VP3, VP4)
-Capsid has 5 fold axis of symmetry

Question 8

Poliovirus causes what disease:

Answer 8

-Poliomyelitis
-Disease that leads to distraction of large motor neurons and causes acute flaccid paralysis (AFP)
-Which is transmitted by Faecal-oral

Question 9

Types of poliomyelitis

Answer 9

1. Non paralytic poliomyelitis (causes high fever, back pain, muscle spasms)
2. Paralytic poliomyelitis (causes muscle paralysis when relaxed and can become permanent after months)

Question 10

In what year did polio cases peak in Ireland?

Answer 10

Epidemic lasted from 1948-1964
-Peaked in 1956-1958 (over 500 cases)

Question 11

When was the last recorded case of polio?

Answer 11

1984

Question 12

Polio remains endemic in which three countries?

Answer 12

-Pakistan
-Afghanistan
-Nigeria

Question 13

What does tropism mean?

Answer 13

Tropism is the pattern of host cells which a virus can invade and replicate in

Question 14

How is Tropism determined:

Answer 14

-By the host cells susceptibility to vital entry
And
-If the cell is permissive for replication

Question 15

Poliovirus tropism:

Answer 15

-Gut M-cells (enterotropic)
-Large motor neurones (neurotropic)
-Lymphoid cells

Question 16

Susceptible vs permissive cells:

Answer 16

-All primate cells are susceptible (as they express the PV receptor)
-Only gut and CNS cells are permissive

Question 17

Genome characteristics of a poliovirus

Answer 17

-Has single copy of genome
-Single open reading frame
-Capsid proteins, protease and Polymerases in between the 5’ and 3’ untranslated regions

Question 18

Poliovirus replication cycle: steps 1-3

Answer 18

1. Virus binds to the receptor (PVR) on susceptible cells and enters the
2. Virus uncoats and releases its positive sense RNA
3. The RNA is translated into proteins in permissive cell

Question 19

Poliovirus replication cycle: steps 4-7

Answer 19

4. Polymerase makes negative RNA template from positive RNA
5. Positive mRNA is made from negative RNA template
6. Progeny virus is assembled using the positive mRNA
7. Cell Lyses and the virus is release

Question 20

Polio that replicates in the gut causes what?

Answer 20

A mild fever

Question 21

Polio that replicates in the CNS caused what?

Answer 21

Poliomyelitis

Question 22

Viral evasion strategies of polio virus:

Answer 22

-Can survive acidic GI tract
-Replicates quickly
-Infection begins before symptoms appear

Question 23

Types of polio vaccines

Answer 23

1. Oral polio vaccine (OPV)
2. Inactivated polio vaccine (IPV)

(Side note) it is recommended that both vaccines are given to a child. One at 2-4 months and the other at 4 years of age

Question 24

Oral Polio vaccine (OPV)

Answer 24

-Also known as Sabin Vaccine
-As developed by Albert Sabin
-Created in 1963
-Contains a mixture of 3 live, attenuated strains

Question 25

Inactivated Polio vaccine (IPV)

Answer 25

-Also known as Salk vaccine -As developed by Jonas Salk -Created in 1955 -Contains a mixture of 3 formalin inactivated virulent strains

Question 26

Problem with IPV?

Answer 26

Not all the vaccines were attenuated, meaning that they caused disease.

Question 27

HIV belongs to what family?

Answer 27

Retroviridae

Question 28

HIV belongs to what genus?

Answer 28

Lentivirus

Question 29

Baltimore classification of HIV?

Answer 29

-Group 6 -Reverse transcribing Diploid single stranded RNA viruses

Question 30

Difference between HIV-1 and HIV-2 strains?

Answer 30

-HIV-1 is more virulent and can be easily transmitted. Causes majority of HIV infections globally -HIV-2 is less transmítanle and is mostly confined to west Africa

Question 31

Origin of HIV:

Answer 31

-No single theories is proven But -The ‘hunters theory’ is the most accepted. -In this theory the virus was transferred when a human was bitten by a chimp

Question 32

Structure of HIV:

Answer 32

-Size (110nm) -Has two copies of single stranded positive sense RNA -Icosahedral Capsid symmetry -Encased by a matrix protein within an envelope -Envelope is lipid bilateral derived from host membrane but contains viral proteins gp120

Question 33

Enzymes in HIV:

Answer 33

-Reverse transcriptase -Integrase -Protease

Question 34

Genome organisation of HIV:

Answer 34

-2 copies of genome (9719 nucleotides) -3 reading frames -3 major genes (gag, pol, env) inbetween the 5’ and 3’ long terminal repeats (LTR) -Accessory genes (nef, tat, vif)

Question 35

The 3 major genes in HIV:

Answer 35

-Gag (capsid, matrix, protease) -Pol (Reverse transcriptase and integrase) -Env (envelope proteins such as docking glycoprotein gp120)

Question 36

HIV tropism:

Answer 36

-M-tropic (Primate cells expressing CD4 and macrophages) -Lymphotropic

Question 37

How the immune system works against HIV infection:

Answer 37

1. Direct viral killing of infected cells 2. Increased rates of apoptosis in infected cells 3. Killing of infected CD4+ cells by CD8 Cells 4. Death of un infected CD4 ‘bystander cells’ by cell suicide

Question 38

HIV replication cycle: steps 1-4

Answer 38

1. virus binds to receptor on TH cell 2. Capsid enters cell and releases positive sense RNA 3. +RNA is converted to DNA by reverse transcriptase 4. +/- DNA is transported to nucleus and integrates into host genome (provirus)

Question 39

HIV replication cycle: steps 5-7:

Answer 39

5. mRNA made from provirus 6. Progeny virus (mRNA) is assembled at cell surface 7. immature virus buds from cell then matures

Question 40

How HIV evaded the immune system:

Answer 40

1. Fast replication cycle 2. High mutation rate 3. Recombinogenic properties of reverse transcriptase