10.2 RNA Viruses Flashcards
Structure of Influenza virus
Orthomyxovirus
-spherical
-enveloped
-segmented, negative strand RNA genome
Surface antigens of Influenza
(H) Haemagglutinin: bind to cells of the infected person
(N) Neuraminidase: releases the virus from the host cell surface
Replication of Influenza check
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
Animal reservoir of Influenza virus
Influenza A: humans, swine, equine, birds, marine mammals
Influenza B: humans only
Influenza C: humans, swine
Explain how Influenza gains entry to the human host and their subsequent uptake and spread from person to person
- Influenza virus attached to sialic acid residues on host cell glycoproteins/lipids
- Entry occurs via receptor-mediated endocytosis
- -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
Describe the clinical symptoms & complications of influenza infection
Prevention: vaccination
Treatments: fever, headache, sore, throat, cough, aches, pains
Complications: fatality
How do you diagnose influenza
Symptoms
Clinical assessment
Prevention of influenza
(A&B)
1. Formalin-inactivated vaccine by injection
2. Live, attenuated, cold-adapted vaccine by nasal spray
Treatment for Influenza
- A: Antivirals
Inhibiting viral uncaring after uptake through M2 protein - A&B: Neuraminidase Inhibitors
Inhibiting viral release from the infected cell & cause aggregation of viral particles
E.g.) oseltamirir, zanamirir
Structure of SARS-CoV-19
Coronaviridae
-large
-enveloped
-pleomorphic particles
-distinctive arrangement of spikes projecting from their surfaces
Replication of SARS-CoV-2 virus
+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
Animal reservoir of SARS-CoV-2 virus
humans, bats, civet, camel
Major surface antigens of SARS-CoV-2 virus
Spike (S) glycoprotein
-required for entry into cells
Explain how SARS-CoV-2 virus gain entry to the human host
- Coronavirus binds to spike glycoprotein on the surface
- ACE2 (transmembrane protein) which is widely expressed in lung, heart, kidney and GI tissue, acts as a receptor for coronavirus
- Entry occurs via receptor-mediated endocytosis
Clinical symptoms & complications of SARS-CoV-2 infection
Symptoms: fever, headache, sore throat, sneezing, muscle/joint pain, extreme fatigue, dry cough, loss of taste/smell
- Antibodies triggered & immune cells move to site of infection
- Release of cytokines leading to local inflammation
How is SARS-CoV-2 virus diagnosed
Detection: Nasopharyngeal swab using RT-PCR
Amount of virus: LFT
Prevention of SARS-CoV-2 virus
mRNA vaccines
Management of SARS-CoV-2 virus
Supportive treatment
Antivirals
Define the concept of ‘Antigenic drift’ and ‘Antigenic shift’ in Influenza virus
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
Define the concepts of mutation rate and production of variants for SARA-CoV-2
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
Define the concepts of pandemics and epidemics and how these may arise in relation to influenza
Epidemic: widespread occurrence of an infectious disease in a community at a particular time
Pandemic: epidemic over a very large areas; affecting large pop.
Explain how SARS-CoV-2 spread from person to person
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
How does influenza cause death
-T cells attack and destroy the tissues in which the virus is replicating
-Opportunistic secondary infection
(I.e. Streptococcus, Staphylococcus species)
