Flashcards in Orthomyxoviridae Deck (24):
What is the virus genus that you should know from the family orthomyxoviridae?
What are the important characteristics of orthomyxoviridae? (ss/ds, pos/neg, DNA/RNA, env/non-env)
enveloped (-) ssRNA
What virus is the cause of epidemics annually and periodic pandemics?
What is the structure of the influenza virus genome
(-) ssRNA in 8 different RNA segments
This is important in genome mutation and reassortment events
What are the virulence factors on influenza?
- HA glycoprotein trimer
- NA glycoprotein tetramer
- Matrix-1 (M1) lines the inside of the vision
- Matrix-2 (M2) found in the viral envelope that forms a proton channel after exposure to endosomal low pH
What is the function of HA (hemagglutinin)?
- attachment to sialic acid on epithelial cells
- agglutinates RBCs
- stimulates neutralizing Ab response
What is the function of NA (neuraminidase)?
- cleaves sialic acid on glycoproteins, including viral receptors on cells
- prevents cell clumping and may facilitate the release of virus from infected cells
What is the function of Matrix-1 (M1)? and what virus is it found on/in?
- lines inside of virion
- promotes assembly of the virus
- "scaffolding protein"
- found in influenza
What is the function of Matrix-2 (M2)? and what virus is it found on/in?
- found in the viral envelope
- forms a proton channel when exposed to low pH in endosome
- influx of protons into the virion loosens RNP core from M1 protein
- ultimately leads to uncoating in the cytoplasm
What drugs inhibit M2 function? What does this accomplish?
amantidine and rimantadine
These bind to, and block the, H+ channel formed by the M2 protein
This blocks virus uncoating
What is unusual about influenza A among RNA viruses?
this RNA virus has RNA transcription and genome replication in the nucleus
How is influenza transmitted?
What is antigenic drift?
Minor antigenic changes in HA or NA
Less than 1% genome sequence differences
Due to random mutations of the viral genome
What is antigenic shift?
Major antigenic changes in HA or NA
Greater than 20% AA sequence variation
Due to genome re-assortment
Which is responsible for local outbreaks of influenza every 2-3 years: antigenic drift or shift?
Which is responsible for pandemics of influenza every 10 years or so?
What are some serious complications of influenza?
- bacterial pneumonia
- encephalopathy and cerebral edema
- Reye's Syndrome
What is Reye's Syndrome?
An acute encephalopathy which occurs in children following several viral infections like influenza A or B or varicella
How do we diagnose influenza?
clinical symptoms are often sufficient
viral culture, CPE, hemeadsorption are helpful but not specific
specific ID requires immunofluorescence or HAI with specific antibody
How do we treat influenza?
amantidine and rimantidine can be used prophylactically or for early treatment for influenza A (remember these block M2 function and viral uncoating)
Zanamivir and oseltamivir together make Tamiflu, and these are a sialic acid analogue that interferes with NA activity of influenza A and B
What are the four major drugs used to treat influenza?
How do Amantidine and Rimantidine work?
They block Matrix-2 (M2) and stop viral uncoating
How to Zanamivir and Oseltamivir work?
They are sialic acid analogues that interfere with the ability of NA in influenza A and B