Respiratory Viruses I (influenza, corona)

Question 1

Orthomyxoviruses

Answer 1

Influenza A, B and C

Question 2

Paramyxoviruses

Answer 2

Measles
Mumps
Respiratory syncytial
Parainfluenza

Question 3

Human influenza virus types and their infections

Answer 3

Influenza A - influenza pandemic
Influenza B - influenza
Influenza C - mild respiratory tract infections

Question 4

Genome of human influenza virus

Answer 4

Segmented, single strand RNA

Question 5

Capsid of influenza virus

Answer 5

Helical necleocapsid

Question 6

Spikes on influenza virus

Answer 6

Two types of spikes
- hemagglutinin
- neuraminidase

Question 7

Functions of hemagglutinin

Answer 7

• binds to the cell surface receptor (sialic acid) to initiate infection of the cell
• target of neutralising antibody

Question 8

Function of neuraminidase

Answer 8

• cleaves neuraminic acid to release progeny virus from the infected cell
• also degrades the protective layer of mucus in the respiratory tract

Question 9

Spike protein which functions at the beginning of the infection in influenza virus

Answer 9

Hemagglutinin

Question 10

Spike protein which functions at the end of the infection in influenza virus

Answer 10

Neuraminidase

Question 11

Types of antigenic changes

Answer 11

1) antigenic shift: major change reassortment/mixing of segments of the genome RNA
2) antigenic drift: minor change mutations in the genome RNA

Question 12

Matrix proteins of influenza virus

Answer 12

M1- located b/w the internal nucleoprotein and the envelope

M2 - forms an ion channel b/w the interior of the virus and the external environment

Question 13

Function of M1 protein

Answer 13

Structural integrity

Question 14

Function of M2

Answer 14

Uncoats the virion after it enters the cell, frees the nucleocapsid containing the genome RNA, allowing it to migrate to the nucleus

Question 15

Virion structure of orthomyxovirus

Answer 15

-Spherical virions
- centrally placed 8 segmented -ve stranded RNA put together with a nucleocapsid protein NP into a helical capsid
- outer membrane has glycoproteins spikes (hemagglutinin and neuraminidase)
- anchoring these spikes on the inside of the lipid bilayer are the membrane proteins (M-proteins)

Question 16

Result of an antigenic drift

Answer 16

Results in milder disease in adults who have previously acquired antibodies

Question 17

Result of an antigenic shift

Answer 17

Only occur with influenza type A
- involves trading of RNA segments between animal and human strains
- the virus wields a new HA or NA glycoprotein that has never been exposed to the human immune system so the entire human population would be susceptible, leading to devastating pandemics

Question 18

Clinical findings of influenza virus

Answer 18

Fever, myalgia, headache, sore throat and cough
Resolves spontaneously in 4-7 days

Question 19

Complications of influenza

Answer 19

S.aureus or S.pneumoniae
Reye’s syndrome (encephalopathy and liver degeneration, complication in children)

Question 20

Lab diagnosis for influenza

Answer 20

• ELISA for viral antigen in respiratory secretions
• PCR

Question 21

Treatment of influenza

Answer 21

Neuraminidase inhibitors (inhibits the release of virus from infected cells)

Question 22

Structure of Corona virus

Answer 22

-centrally placed non-segmented, single stranded +ve RNA genome put together with a nucleocapsid protein into a helical capsid
- outer membrane has club shaped spikes in the form of a corona (halo)

Question 23

Receptor of SARA coronavirus on the surface of cells

Answer 23

Angiotensin converting enzyme-2

Question 24

Spike proteins of SARS coronavirus

Answer 24

S1- determines the virus-host range and cellular tropism via the receptor-binding domain
S2- mediates the membrane fusion of the virus to its potential cell host

Question 25

Sign and symptoms of SARS

Answer 25

Headache
Loss of smell and taste
Nasal congestion
Runny nose
Cough
Muscle and joint pain
Sore throat
Fever
Diarrhoea
Breathing difficulties

Question 26

Clinical findings in SARS coronavirus

Answer 26

Chest xray: ground glass infiltrates that do not cavitate
Leukopenia and thrombocytopenia