17. Diagnosis and Evolution of SARS-CoV2

Question 1

what does PCR detect, has this been a useful tool?

Answer 1

detects part of the viral genome

proven not to be capable of handling diagnosis at population level (overwhelmed labs)

Question 2

what are some clinical symptoms of SARS-CoV2

Answer 2

fever, fatigue, cough, shortness of breath, sneezing

Question 3

what has been a good alternative to PCR testing

Answer 3

rapid antigen tests (lateral flows)

Question 4

evaluate lateral flow tests

Answer 4

perks:

• easy to use
• does not require labs
• easy to dispense
• quick results

cons:
- only available in western countries
- false negatives (low specificity)

Question 5

describe the Ellis & Delbruck experiment

Answer 5

• grow bacteriophages in E.coli

- proved phages develop intracellularly

Question 6

describe the Hershey & Chase experiment

Answer 6

showed that only the DNA of a virus needs to enter a bacterium to infect it

Question 7

describe Fraenkel et al

Answer 7

showed that RNA is the genetic material of tobacco mosaic virus

Question 8

how can we quantify viruses

Answer 8

with plaque forming units

Question 9

what does PFU show?

Answer 9

an indication of cells that have died because of viral infection
- allows us to quantify the presence of a virus

Question 10

what does haemagglutinin do?

Answer 10

bind to the surface of cells forming cross links = cause cells to clump together (agglutinate)

Question 11

how do you perform a haemagluttination assay

Answer 11

dilute virus in wells and add the RBCs - where there is virus present, clumping will occur

Question 12

how does a haemagglutination inhibition assay work?

Answer 12

same protocol as haemagluttinin assay, but add antiviral to the mix

is there is no aggulutination = virus is not present

Question 13

what does sandwich ELISA assay test for

Answer 13

the presence of viral antigens

Question 14

how does sandwich ELISA work

Answer 14

add sample to wells, if virus present it will bind to stationary antibodies

then add a further antibody which has a conjoined enzyme

if virus is present, any substrates added to the sample will be converted into a colourful compound by the enzyme, this colourful compound can be quantified using a spectrophotometer

Question 15

how does antibody-capture ELISA work

Answer 15

wells coated with virus antigen, test samples (potentially containing antibody) are added to the wells

samples washed away, any remaining bound antibody can be detected using secondary antibody

Question 16

what does ELISA antibody-capture test for

Answer 16

the presence of antibodies

Question 17

how does neutralisation assay work

Answer 17

tests whether antibodies in the sample bind well enough to the virus to deactivate it

quantifies the presence of functional antibodies to the virus

Question 18

by what 3 ways do viruses evolve

Answer 18

point mutations
recombination
assortment

Question 19

what virus has a high mutation rate, why?

Answer 19

influenza

assortment occurs frequently

Question 20

what virus has a low mutation ate

Answer 20

SARS-CoV2

- no segmented genome so no assortment

Question 21

what is the difference between the latent and incubation period

Answer 21

latent period = time interval between contracting the disease and becoming infectious
incubation period = time interval between contracting the disease and showing symptoms

Question 22

what is the average latent period for COVID-19

Answer 22

5.6 days