28 - Influenza Flashcards
Influenza is caused by…
Orthomyxovirus
Influenza B and C infect humans and are ( mild / severe ).
Influenza B and C infect humans and are mild.
Influenza A is capable of infecting humans, birds, pigs, horses and sea mammals. Epidemics occurs every _-_ years and pandemics have occured every __-__years.
Influenza A is capable of infecting humans, birds, pigs, horses and sea mammals. Epidemics occurs every 2-3 years and pandemics have occured every 10-40 years.
With respect to viral antigens, state the difference between epidemics and pandemics…
Epidemics are driven by antigenic drift, whereas pandemics occur as the result of antigenic shifts.
Key symptoms of Influenza (4)
- Runny nose (leaky endotheliums)
- Cough
- Fever
- Muscle aches
Transmission of Influenza
Aerosol (respiratory)
Influenza infects which cells?
Cilliated epithelium cells in the upper respiratory tract
Briefly outline how influenza symtpoms arise…
- Infected epithelial cells are destroyed by the virus
- Systemic response - macrophages phagocytose lysed cells & virus particles
- Proinflammatory cytokines (e.g. IL1) are relased (fever)
- Endothelial permeability increases (leaky) (runny nose)
Describe the immune response to influenza in terms of innate and adaptive systems…
-
Innate
- NK cells
- Type I Interferon* (IFNα & IFNβ)
-
Adaptive
- B cells
- Antibodies
- T cells
- Cytotoxic T (CD8+)
- Helper T (CD4+)
- Memory cells
- B cells
*so called ‘viral interferons’ that can be induced directly by viral infection
Antigenic drift is the result of…
Gradual mutations (and is responsible for epidemics)
Antigenic shift is the result of…
Reassortment (and is responsible for pandemics)
“Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans. Shift results in a new influenza A subtype or a virus with a hemagglutinin or a hemagglutinin and neuraminidase combination that has emerged from an animal population that is so different from the same subtype in humans that most people do not have immunity to the new (e.g. novel) virus.”
Vaccines for Influenza
-
Subunit vaccines
- Killed vaccine
- Subunits whole or split
- injected
- used for the elderly/ high risk
-
Attenuated
- Live vaccine
- Nasal spray
- used for children
Treatments for Influenza
-
Amantidine
- M2 channel blocker (prevents replication)
-
Tamiflu
- Neuraminidase inhibitor (prevents sialic acid clevage, thus interfering with release of virus from host cell - gets stuck)
Constrast systemic versus mucosal immunity aquired after influenza infection (Antibody isotype involved, duration)
Systemic immunity involves IgG and lasts around 10 years
Mucosal immunity involves IgA and lasts 2-3 years
Structure of Influenza virion
Inside the nucleocapsid…
Genome consists of __ strands of ____ bound to __________
3 enzymes (PB1, PB2 and PB3) which are ___ ___________ ___ __________ (_______)
Structure of Influenza virion
Inside the nucleocapsid…
Genome consists of 8 strands of RNA bound to nucleoproteins (NP)
3 enzymes (PB1, PB2 and PB3) which are RNA dependent RNA polymerase (RdRp)
Structure of Influenza virion
In and around the envelope
M2 ion channels allow influx of ___ which triggers membrane fusion allowing _______ from the _________
M1 matrix proteins are located ______ the envelope
The two key surface receptors are ___________ (responsible for binding) and ____________ (cleaves sialic acid, allowing the virus to escape host cell after budding)
Structure of Influenza virion
In and around the envelope
M2 ion channels allow influx of H+ which triggers membrane fusion allowing escape from the endosome.
M1 matrix proteins are located on the inside of the envelope
The two key surface receptors are hemagglutinin (H) (responsible for binding) and neuraminidase (NA) (cleaves sialic acid, allowing the virus to escape host cell after budding)
