Respiratory Viruses Flashcards
What viruses are contained within the group Orthomyxoviruses?
Influenza A, B, C
What are the distinguishing characteristics of the members of Orthomyxovirus and how can you differentiate between them?
- Hemaglutinin
- Neuramindase
Each type of Influenza has different combination of H–N–.
What is the difference between Antigenic Drift vs Antigenic Shift?
Drift - minor changes, mutations, in hemaglutinin and neuramindase over time.
Shift - Reassortment of the genes of hemaglutinin and neuroamidase - happens in PIGS!
What kind of cells does influenza target?
Ciliated cells in the respiratory tract
What are factors that contribute to the pathogenesis of influenza?
- Aerosol of influenza - infection in the respiratory tract
- Desquamousation of ciliated cells
- Destruction of cells via CTL
- Interferon induction
What are the timeline of events of infection of influenza?
- Can be up to 7 days of incubation
- interferon induction occurs first at the onset, which causes the flu-like symptoms
- CTL mediated response is activated and antibodies are formed and eliminate the virus
What are common flu-like symptoms?
Rapid onset fever, chills, malaise, myalgias, sore throat, and unproductive cough.
How are influenza symptoms different in children?
Children usually experience worse symptoms and the virus is harder on them.
Higher fever, GI symptoms, otitis media, croup
What are complications of influenza?
Due to the infection of the respiratory tract cells it breaks down the defenses of the body, which can lead to primary viral pneumonia or secondary bacterial pneumonia. Neurologic pathologies too due to similar antibody structure.
What are the best ways to diagnose influenza?
Rapid Antigen serotyping between influenza A and B. Tests for nucleoprotein - 15 minutes.
- rtPCR and/or serotyping
What and how does influenza attach to in order to invade a cell?
Hemaglutinin - binds to the sialic acid - galactose bond
Remember - Humans have 2,6 Bond - Influenza Binds
Avian has 2,3 bonds
Swine have both 2,3 and 2,6, which is why avian influenza can cross over to humans
What does neuroamidase do?
Neuroamidase - cleaves the sialic acid - galactose bond in order to release the virion from the cell, if this is inhibited by Oseltamivir the virus cannot spread
What is key for uncoating of influenza?
When the vesicle that contains the virion begins changing into late endosome the pH lowers, which M2 protein opens a channel allowing the protons into the virion activating hemaglutinin to fuse with the membrane and uncoat.
Where does influenza replicate its genome and transcribe?
Replicates and Transcribes in the genome of the host cell, which is different than most other RNA viruses.
What does the influenza vaccine contain?
Different Hemaglutinins and Neuramindases from different strains predicted for the next season.
Eggs used in production of the virus to be used in vaccines
What are common antivirals used for influenza?
Amanatadine and Rimantidine - blocks M2 channel/uncoating
Ribavirin - inhibits viral RNA synthesis
Oseltamivir and Zanamivir - inhibits neuramindase
How do they get the proper/desired antigen production for the inlfuenza vaccines?
They inoculate the egg with two strains, one has the desired surface antigens and the other is designed to grow well in avian models, and the desired antigens are selected for using antibodies against the other.
What are the most common strains of influenza in the seasonal vaccine?
H3N2
H1N1
Where does Rhinovirus localize its infection and why?
Upper respiratory tract, because it grows better at lower temperatures.
–most common cause of common cold–
What causes the symptoms of a Rhinovirus?
Immune response in the upper respiratory tract, the infected cells release bradykinin and histamine causing the runny nose and sore throat (inflammation).
What kind of virus is the Rhinovirus and what replication cycle does it exhibit?
Picornavirus - Polio replication
Many serotypes, thus there is no prevention
What is the 2nd most common cause of the cold in humans?
Coronaviruses
How are Coronaviruses similar to Rhinoviruses?
They both infect the upper respiratory tract and grow best at lower temperatures
What are two notable coronaviruses in recent times?
SARS and MERS virus.
