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46 Cards in this Set

  • Front
  • Back
What is single-stranded RNA?
RNA that has 1 strand of nucleic acid
What is unique about negative ssRNA?
Negative ssRNA must first be converted into positive ssRNA before it can be translated.
What enzyme is needed to aid in te replication of -ssRNA?
RNA-dependent RNA polymerase
What is the general site of nucleic acid replication of RNA viruses?
Cytoplasm
What RNA viruses are the exceptions?

Where do they replicate?
Orthomyxoviridae (-ssRNA)
Retrovirus (+ssRNA)

Nucleus
What is an enveloped virus?
A virus that has a lipid bilayer outer membrane surrounding its nucleic acid, which when present, plays an important role in viral penetration.
How do viruses acquire this envelope?
From host cell membrane secondary to viral host cell budding.
How do enveloped viruses enter host cells?
Fusion of the viral envelope with the host cell membrane.
What are capsids?

What do they look like?
Proteinaceous shells that surround viruses.

Icosahedral
Helical
What are the enveloped -ssRNA virus families?
1) Filoviridae
2) Orthomyxoviridae
3) Bunyaviridae
4) Arenaviridae
5) Rhabdoviridae
6) Paramyxoviridae
What's the capsid geometry of -ssRNA viruses?
Helical

All -ssRNA have:
Envelopes
Helical capsids
What are the arthropod borne viruses?
Flaviviridae (-ssRNA)
Bunyaviridae (-ssRNA)
Togaviridae (+ssRNA)
What is a segmented genome?
A genome that is physically separated into several segments.
What viruses have segmented genomes?
Bunyavirus (-ssRNA)
Orthomyxovirus (-ssRNA)
Arenavirus (-ssRNA)
Reovirus (dsRNA)

BOAR
What type of nucleic acid do Orthomyxoviridae contain in their genome?

What is their capsid geometry?

Do they contain an envelope?
-ssRNA with an eight-part segmented genome.

Helical

YES
What disease is caused by Orthomyxoviridae?
Influenza
what is teh incubation period of influenza caused by Orthomyxoviridae?
24-48 hours
What are the clinical manifestations of influenza caused by Orthomyxoviridae
Sudden onset of symptoms, i.e.,
Fever,
Myalgia,
Headache,
Cough, and
Fatigue
What are three important glycoproteins associated with influenza virus?
Hemagglutinin (HA)
Neuraminidase (NA)
M2
How does hemagglutinin contribute to pathogenesis?
Promotes viral entry into the cell by acting as the viral receptor resulting in viral-cell fusion.
How does hemagglutinin promote viral-cell fusion?
Attaches to sialic acid receptors on host cell

Creates conformational changes at low pH inside the host cell endosome
How does neuraminidase contribute to pathogenesis of Orthomyxoviridae?
1) Prevents binding of virus back to infected cells by cleaving host cel sialic (neuraminic) acid, allowing progeny virus to infect uninfected cells and not be 'wasted' on previously infected cells.

2) Disrupts the mucin of healthy mucosal epithelial cells, exposing new sialic acid binding sites for virions
How does M2 contribute to pathogenesis of Orthomyxoviridae?
Acts as an ion channel within the endosome allowing H+ to enter the virion and viral RNA to be released to the cytoplasm.
What are the treatment implications of understanding the glycoprotiens associated with Orthomyxoviridae?
HA, NA, adn M2 protein are cellular targets used to suppress influenza infections.
What is different about influenza replication when compared to the majority of other RNA viruses?
Replication occurs in the nucleus Orthomyxoviridae and Retroviridae (+ssRNA) are the only RNA viruses that replicate in the nucleus.
What is one defense mechanism of influenza virus?
Suppressing the host cell antiviral mechanism with viral NS1 protein preventing PKR activation.
How does PKR work?
PKR activation temporarily halts host cell protein synthesis, preventing viral used of host machinery and decreasing viral protein synthesis.
What does teh body use to combat the destruction of respiratory epithelial cells influenza virus?
Cytotoxic CD 8+ T cells
What are three strains of influenza viruses?
A
B
C
Which strain causes worldwide flu pandemics at intervals of 10-20 years?
Influenza A
Which strain causes major seasonal outbreaks of influenza?
Influenza B
Which strain is associated with mild respiratory tract infections?
Influenza C
What is the distinguishing feature between influenza A, B, and C?
Each has different internal proteins, mainly matrix proteins (M) and nucleocapsid proteins (NP).
Which viruses are associated with Reye syndrome and liver degeneration?
Influenza B
Varicella
Which drug is associated with Reye syndrome?
Aspirin use in pediatric patients
What is Reye syndrome?
Noninflammatory encephalopathy with hepatic failure.
What is the best site on the influenza virus to target an immune response?
Antibodies against the HA glycoprotein
What are two important changes occurring in influenza virus resulting in genetic diversity?
Antigenic shift
Antigenic drift
What is antigenic shift?
Major antigenic changes characterized by sudden replacement of a new strain with an antigenically different HA and NA occcurring by reassortment of viral RNA segments (HA1NA1 to HA3NA2)

Antigenic shift only occurs in type A
How often does antigenic shift occur?
Every 10-40 years.
What is antigenic drift?
Minor antigenic changes characterized by random point muttions in viral RNA leading to amino acid substitutions in HA glycoproteins.
Which strains demonstrate antigenic drift?
Influenza A and B
How often does antigenic drift occur?
Every 2-3 years
Which two drugs are effective against both influenza A and B?

What is the mechanism of action?
Zanamivir
Oseltamivir

Inhibit NA
Which two drugs are only effective against influenza A?

What is the mechanism of action?
Amantadine
Rimantadine

Blocks viral uncoating by inhibition of influenza viral M2 membrane protein.
What immunoglobulin mediates immunity against influenza virus?
Secretory IgA in respiratory tract