10.2 RNA Viruses

Question 1

Structure of Influenza virus

Answer 1

Orthomyxovirus
-spherical
-enveloped
-segmented, negative strand RNA genome

Question 2

Surface antigens of Influenza

Answer 2

(H) Haemagglutinin: bind to cells of the infected person
(N) Neuraminidase: releases the virus from the host cell surface

Question 3

Replication of Influenza check

Answer 3

2 stages:

-negative strand of RNA genome codes for RdRp (RNA-dependent RNA transcriptase)

-this synthesises viral (positive) mRNA using the genomic negative-strand RNA as a template

-viral proteins are synthesised and assembled into nucleocapsids

Question 4

Animal reservoir of Influenza virus

Answer 4

Influenza A: humans, swine, equine, birds, marine mammals

Influenza B: humans only

Influenza C: humans, swine

Question 5

Explain how Influenza gains entry to the human host and their subsequent uptake and spread from person to person

Answer 5

1. Influenza virus attached to sialic acid residues on host cell glycoproteins/lipids
2. Entry occurs via receptor-mediated endocytosis
3. -Attachment and fusion functions are associated with H protein
   - Viral release is facilitated by Neuraminidase protein which cleaves the sialic acid residue of the glycoprotein on the cell surface

4.Viral particle is released

Question 6

Describe the clinical symptoms & complications of influenza infection

Answer 6

Prevention: vaccination

Treatments: fever, headache, sore, throat, cough, aches, pains

Complications: fatality

Question 7

How do you diagnose influenza

Answer 7

Symptoms
Clinical assessment

Question 8

Prevention of influenza

Answer 8

(A&B)
1. Formalin-inactivated vaccine by injection
2. Live, attenuated, cold-adapted vaccine by nasal spray

Question 9

Treatment for Influenza

Answer 9

1. A: Antivirals
   Inhibiting viral uncaring after uptake through M2 protein
2. A&B: Neuraminidase Inhibitors
   Inhibiting viral release from the infected cell & cause aggregation of viral particles
   E.g.) oseltamirir, zanamirir

Question 10

Structure of SARS-CoV-19

Answer 10

Coronaviridae
-large
-enveloped
-pleomorphic particles
-distinctive arrangement of spikes projecting from their surfaces

Question 11

Replication of SARS-CoV-2 virus

Answer 11

+strand RNA is converted to -ve stranded RNA to use as the template for the new +ve strand RNA that is packaged into the emerging particles

Question 12

Animal reservoir of SARS-CoV-2 virus

Answer 12

humans, bats, civet, camel

Question 13

Major surface antigens of SARS-CoV-2 virus

Answer 13

Spike (S) glycoprotein
-required for entry into cells

Question 14

Explain how SARS-CoV-2 virus gain entry to the human host

Answer 14

1. Coronavirus binds to spike glycoprotein on the surface
2. ACE2 (transmembrane protein) which is widely expressed in lung, heart, kidney and GI tissue, acts as a receptor for coronavirus
3. Entry occurs via receptor-mediated endocytosis

Question 15

Clinical symptoms & complications of SARS-CoV-2 infection

Answer 15

Symptoms: fever, headache, sore throat, sneezing, muscle/joint pain, extreme fatigue, dry cough, loss of taste/smell

1. Antibodies triggered & immune cells move to site of infection
2. Release of cytokines leading to local inflammation

Question 16

How is SARS-CoV-2 virus diagnosed

Answer 16

Detection: Nasopharyngeal swab using RT-PCR
Amount of virus: LFT

Question 17

Prevention of SARS-CoV-2 virus

Answer 17

mRNA vaccines

Question 18

Management of SARS-CoV-2 virus

Answer 18

Supportive treatment
Antivirals

Question 19

Define the concept of ‘Antigenic drift’ and ‘Antigenic shift’ in Influenza virus

Answer 19

Antigenic drift:
Minor changes in the genes of the flu viruses that occur gradually over time

-occurs in all influenza viruses

Antigenic shift:
Major changes in the genes of flu viruses that occur suddenly when two/more different strains combine

-changes viral subtype resulting in different H and N proteins
-reassignment of different RNA segment from each species in a new capsid
-occurs in influenza A virus
-can cause widespread epidemics/pandemics

Question 20

Define the concepts of mutation rate and production of variants for SARA-CoV-2

Answer 20

High mutation rate because of

-constant replication
-life cycle is short
-viral RNA polymerase have a high error rate since they don’t have a proof reading mechanism

Question 21

Define the concepts of pandemics and epidemics and how these may arise in relation to influenza

Answer 21

Epidemic: widespread occurrence of an infectious disease in a community at a particular time

Pandemic: epidemic over a very large areas; affecting large pop.

Question 22

Explain how SARS-CoV-2 spread from person to person

Answer 22

Small droplets: evaporate into droplet nuclei, remain suspended in air for significant time and could be inhaled

Large droplets: fall rapidly to the ground and only transmitted over short distances

Larger droplets: settles onto surfaces and are transported by hands onto mucosal membranes

Question 23

How does influenza cause death

Answer 23

-T cells attack and destroy the tissues in which the virus is replicating

-Opportunistic secondary infection
(I.e. Streptococcus, Staphylococcus species)