Viral Detection and Diagnosis

Question 1

How would you detect viruses directly

Answer 1

Look for presence of virus or its components

• viral culture
• EM
• AG detection
• Nucleic acid amplification

Question 2

How would you detect viruses indirectly

Answer 2

Blood serum, plasma, body fluids examined for IgM, IgG

Question 3

How would you culture viruses?

Answer 3

Needs permissive cell cultures

• cytopathic effects (eg, rounding, detachment from surface)
• cell fusion
• inclusion body formation (warehouse of newly made viruses)

Each virus has a characteristic pattern

Question 4

Describe what you might find in serological diagnosis

-ELISA

Answer 4

Enzyme mediated colour change if AB from patient specific to AG present

Acute/primary => IgM
Seroconversion => IgG in convalescent samples

Question 5

How would you manage viral infections

-3 methods

Answer 5

Public health

Antivirals
-antiviral agents, immunomodulators

Immunisation

Question 6

What problems do we have when developing directly acting antivirals

Answer 6

Viruses are intracellular

-we want to control viral replication => target of drug must be specific to avoid damaging host cell

Question 7

What are the 6 potential targets for antivirals

Answer 7

Attachment and entry

• binding inh
• fusion inh

Nucleic acid synthesis

• viral DNA, RNA polymerase inh
• integrase inh

Assembly and budding

• protease inh
• neuraminidase inh

Question 8

What are the 3 types of DNA polymerase inhibitor by chemical structure

• when would you use them
• what are examples of drugs

Answer 8

Nucleotide inh
-cidofovir => CMV, HHV, adeno

Nucleoside analogue

• aciclovir => HSV, VZV (incoorporated into DNA chain, cannot be translated)
• ganciclovir => CMV

Non nucleoside inh
-foscarnet => CMV

Question 9

What is an example of an RNA polymerase inhibitor

-how does it work

Answer 9

Remdesivir (adenosine nucleotide prodrug)

-inhibits RNA dep RNA polymerase to prevent replication

Question 10

What is herd immunity

Answer 10

Situation where a sufficient proportion of a population is immune to a disease to make its spread from person to person unliekly

Question 11

What are the requirements of an effective vaccine

Answer 11

Safe => no/few SE, must not cause disease

Give long lasting protection against natural form of pathogen

Stimulate humoral, cell mediated immune response and memory cell production

Low in cost
Stable with long shelf life, no special storage requirements

Easy to administer