Anti-Virals

Question 1

What are viruses?

Answer 1

Obligate intracellular parasites

Question 2

Which anti-viral has the highest level of specificity?

Answer 2

Acyclovir

Question 3

What condition is acyclovir used to treat?

Answer 3

Herpes

Question 4

Why is acyclovir so specific?

Answer 4

Given to patients in the unphosphorylated form, has to be phosphorylated from ACV to ACVMP, this is only done by thymidine kinase which is an enzyme only found in virally infected cells

Question 5

How does acyclovir work as antiviral?

Answer 5

Works as a nucleoside analogue - acts as a chain terminator as it lacks an OH group in the 3’ direction meaning phosphodiester binds cannot form, preventing viral replication

Question 6

What is a nucleoside inhibitor?

Answer 6

Molecule which looks like a nucleoside and is therefore incorporated into the genome, but actually inhibits viral replication

Question 7

What is RNA in the negative sense?

Answer 7

A strand of RNA which is complementary to the mRNA

Question 8

What sense of genetic material can ribosomes translate?

Answer 8

Positive sense

Question 9

What is a virion

Answer 9

A virus particle outside the cell

Question 10

Why can ribosomes not be targeted in anti-viral medications?

Answer 10

viruses uses human ribosomes to replicate, meaning they would be attacked

Question 11

What is the central dogma?

Answer 11

DNA -> RNA -> proteins

Question 12

Whose polymerase do viruses use to replicate?

Answer 12

Their own

Question 13

Why do viruses have a high mutation rate?

Answer 13

They use their own polymerase to replicate which LACK PROOF READING

Question 14

RNA is shorter than DNA. How do RNA viruses compensate for this?

Answer 14

They use COMPLEX CODING STRATEGIES to they can make more proteins than expected

Question 15

Why is it useful for DNA viruses to be large?

Answer 15

They have room to acquire accessory genes which could make that virus better at modifying host immune response

Question 16

What is a segmented genome and how does this impact viruses?

Answer 16

Allows easy recombination, therefore if different strains of the virus enter the host, reassortment can occurs, producing new variants

Question 17

What is the size range of viruses?

Answer 17

1nm to 1 micrometer

Question 18

What are two examples of neuramidase inhibitors?

Answer 18

Tamiflu and Relenza

Question 19

What is Remdisivir a nucleoside inhibitor of?

Answer 19

Adenosine

Question 20

How does Remdisivir work as a nucleoside inhibitor?

Answer 20

Acts as adenosine, and causes chain termination three nucleosides later, due to the chain twisting

Question 21

What is Remdisivir used to treat?

Answer 21

Hepatits C

Question 22

What is amantidine?

Answer 22

A adamantine

Question 23

How does amantidine work as an antiviral?

Answer 23

Blocks the M2 ion channel which would normally allow H+ ions to enter into the endosome, meaning that the virus is trapped inside the endosome and therefore cannot replicate

Question 24

Why is the use of amantidine not recomendable?

Answer 24

Most H3N2 viruses are resistant to it

Question 25

How do NA inhibitors work?

Answer 25

They block the action of neuramidase preventing the virus from being released from the cel Normally, NA works by cleaving the sialic acid / HA binding which the virus does to latch into the host cell, allowing the virus to leave

Question 26

What are tamiflu and relenza used to treat?

Answer 26

Influenza

Question 27

What is the lipid envelopes of viruses derived from?

Answer 27

The host cell membrane

Question 28

What is the cell membrane of a non-enveloped virus made from?

Answer 28

Pure proteins

Question 29

In cultured cells, why are some genes in virus’ genome lost?

Answer 29

Some genes are used to limit the immune response of the host cell against the virus to give the virus an advantage, however there is no immune response in cultured cells therefore these genes are not needed

Question 30

What are the stages of viral replication?

Answer 30

``` Attachment Insertion Translation Assembly Exocytosis ```

Question 31

What do direct acting antivirals target?

Answer 31

Specific viral factors

Question 32

What are biologicals?

Answer 32

Antibodies which are derived from recovered individuals or synthesized in the lab from immobilized B cells - given directly into the blood

Question 33

What anti-virals are used to treat Hepatitis C?

Answer 33

Direct Acting Antivirals

Question 34

Between Relenza and Tamiflu, which is more effective and why?

Answer 34

Tamiflu - the chemistry of relenza means the virus can more readily acquire resistance so less effective

Question 35

Acyclovir and ribavirin are both antiviral agents that act as nucleoside analogues. Why is acyclovir effective against herpes simplex virus but not influenza?

Answer 35

c) Because acyclovir is only converted to its active form inside a cell infected by herpes virus that encodes thymidine kinase, and influenza virus does not encode such an enzyme.

Question 36

Tamiflu (oseltamivir) is an antiviral drug that can be used to treat influenza virus infection. The mechanism of action is:

Answer 36

a) To inhibit the neuraminidase enzyme that removes sialic acid from the infected cells surface and allow onwards spread of new virus particles.

Question 37

Why might a patient with chronic hepatitis C virus treated with an HCV protease inhibitor drug show a loss of a positive viral response over time?

Answer 37

The virus has acquired resistance to the drug. The patient has continued in high risk lifestyle and acquired a second infection with a different strain of HCV. The patient has stopped taking the drug because it gave unpleasant side effects.

Question 38

Two people in the world are believed to have been ‘cured’ of HIV. How has this been achieved?

Answer 38

They have undergone bone marrow transplantation with cells from a CCR5 delta 32 donor.

Question 39

what is PrEP for HIV?

Answer 39

Pre exposure Prophylaxis (PrEP) means taking HIV antivirals daily to prevent possible HIV infection during sex with an infected partner.

Question 40

BHIVA guidelines require that people have an HIV test before going on PrEP. Why is this so important?

Answer 40

If the person is already HIV infected you don’t want to be giving them treatment with only two drugs as resistance can likely be selected more easily than the standard which is three drugs at once.

Question 41

Single use of antiviral agents increase the risk of resistance. How is this overcome?

Answer 41

Through the use of combination therapy - this means the chances of anti-viral resistance is much less likely, as the virus would have to have a gene mutation against every single drug in the combination

Question 42

What are four stages of HIV replication which are targeted in combination therapy?

Answer 42

1. Viral entry inhibition 2. Integration of viral genome inhibition 3. Protease inhibition 4. Reverse transcriptase inhibitors