Evolution & Medicine

Question 1

What is HIV?

Answer 1

A lentivirus that causes AIDS

Question 2

Where does infection of HIV occur?

Answer 2

Through bodily fluids

Question 3

How many deaths occurred between 1981 and 2006?

Answer 3

WHO estimates 25 million

Question 4

What happened before the disease was recognised?

Answer 4

It was occasionally spread through contaminated blood products

Question 5

How much of the population does HIV affect?

Answer 5

0.6%

Question 6

How many deaths are as a result of HIV?

Answer 6

3.5% of deaths worldwide (5.7% in low income countries)

Question 7

What does the HIV virus infecting cause?

Answer 7

Failure of the immune system

Question 8

HIV is a virus and…

Answer 8

has a genome

Question 9

What happens with the HIV genome?

Answer 9

It is often inserted into the human genome in infected cells

Question 10

What can be done using PCR?

Answer 10

You can isolate viral genomes, or pieces of viral genomes, from infected patients

Question 11

What can come from each patient with HIV?

Answer 11

Multiple sequences

Question 12

What is shown on a phylogenetic tree of HIV patients?

Answer 12

The sequences are more closely related within a patient than between patients

Question 13

What are the possible explanations of the patter of HIV genomes on a phylogenetic tree?

Answer 13

Infections from multiple viruses or the viruses are changing

Question 14

What is meant by infections from multiple viruses?

Answer 14

Each patient may have more than one viral sequence because they were infected with multiple viruses

Question 15

What is evidence for people having infections from multiple viruses?

Answer 15

Multiple sequences, infection from ‘bulk source’

Question 16

What is evidence against people having infections from multiple viruses?

Answer 16

The pattern of the tree - of there were multiple infections, why are viruses within patients more similar than viruses between patients

Question 17

What is meant by the viruses are changing?

Answer 17

The multiple sequences may be due to the viruses changing within a patient

Question 18

What is evidence for the viruses changing?

Answer 18

Viruses within a patient are more similar than between. The pattern of the tree suggests a single point of entry of the virus and then diversification

Question 19

What is evidence against the virus changing?

Answer 19

Patient 91 has virus in two parts of the tree

Question 20

What is the prediction for the virus changing?

Answer 20

If the viruses are changing then if we sample a patient successively then we should see different viral sequences occurring

Question 21

What are the two types of explanation for the HIV sequence changing?

Answer 21

Proximate - By what mechanism is the change occurring

Ultimate - What is causing the change

Question 22

What is a lentivirus?

Answer 22

A sort of retrovirus

Question 23

What type of genome does HIV have?

Answer 23

a RNA genome

Question 24

What does HIV do?

Answer 24

Infect and damage immune system cells

Question 25

What is reverse transcriptase?

Answer 25

An enzyme that turns RNA sequence back Ito NDA

Question 26

HIV sequence is RNA, but ...

Answer 26

it is turned into DNA to insert into the human genome

Question 27

Reverse transcription is ...

Answer 27

more error prone than DNA replication so lots of variants are formed

Question 28

Is it just a mutation?

Answer 28

The key is we do not find inactivating mutations, all the variants found encode active, working viruses. So is it evolution?

Question 29

What is required for natural selection?

Answer 29

Variation, inheritance, selection, time

Question 30

How does HIV show variation?

Answer 30

By the error-prone nature of HIV reverse transcription

Question 31

How does HIV show inheritance?

Answer 31

HIV viruses pass on their RNA after being inserted in the genome

Question 32

How does HIV show selection?

Answer 32

The immune system, drug regimen, changes in the receptor and tropism in tissues for or against the HIV variants

Question 33

How does HIV shoe time?

Answer 33

HIV lifecycle is very fast, so in the course of infection there is plenty of time for evolution

Question 34

How can it be tested if HIV evolves?

Answer 34

Changing the selective pressure or seeing if viruses evolve differently of you put. patient on anti-retroviral drugs

Question 35

What is seen when it is tested if HIV evolves?

Answer 35

AIDS viruses from patients on anti-retrovirals have a different pattern of variation from those that are not

Question 36

What is the most clear example of HIV evolving?

Answer 36

The advent resistance of viruses - first to AZT, now to ripple therapy or HAART (high active retroviral therapy)

Question 37

What does HIV hold the record for?

Answer 37

The fastest evolving thing we know of

Question 38

What do patients have?

Answer 38

The don't have a virus, they have a vast armada of viral variants

Question 39

What arises rapidly?

Answer 39

Resistance to therapy, even complex therapy

Question 40

What is made hard by the rapid evolving of HIV?

Answer 40

Making effective vaccines

Question 41

How many provirus containing cells are in a HIV patient?

Answer 41

10^8 to 5x10^10

Question 42

What may each provirus containing cell be?

Answer 42

Genetically distinct, so assuming 1 provirus/cell we have up to 5x10^10 variants

Question 43

What do many pathogens do?

Answer 43

Evolve within the host in the same way as HIV

Question 44

What is also an evolutionary process?

Answer 44

The antimicrobial resistance spreading through a population

Question 45

What does our own genome evolve to?

Answer 45

In response to pathogens

Question 46

What can evolutionary thinking do?

Answer 46

Help us understand and better respond to pathogens like HIV

Question 47

Evolution is ...

Answer 47

a key way that pathogens response to hosts and therapy