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25 Cards in this Set

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What family does influenza belong to?
Orthomyxovirus.
Describe the structure of the influenza virion and genome.
*helical, enveloped capsid
*genome is a (-) ssRNA divided among eight segments which are wrapped by NP
What are the two significant glycoproteins on the surface of the influenza virus? What does each do?
*HA: mediates attachment to the cell surface via sialic acid receptors
*NA: helps the virus penetrate the respiratory mucus and cleaves sialic acid when the virus leaves the cell
Where in the host cell does the replication of the influenza virus occur?
In the host cell nucleus.
What are the M1 and M2 proteins?
They are channel proteins that allow the influx of H+ into the virion which activates several cellular processes
What are the three general types of influenza virus? Give a brief description of the epidemiology of each.
*A - affects humans, swine, and birds; causes pandemics, most severe
*B - affects humans only, especially children; causes epidemics
*C - affects humans and swine; sporadic and least severe
What is antigenic drift? Why is the influenza virus prone to this phenomenon? How does this affect immunity?
*Slight mutational changes in the viral genome that create new serotypes
*occurs because of the high error rate of the viral RNA pol
*allows evasion of immune response
What is antigenic shift? How does it occur? Why do forms that undergo antigenic shift have the capacity to cause pandemic disease?
An entirely novel form of the influenza virus created when a single cell is infected by human and animal strains of the virus which then reassort their RNA segments. They are dangerous because there is no pre-existing immunity in the population.
What are three complications of influenza? What populations are affected by each?
1.Primary viral pneumonia - elderly
2.Secondary bacterial pneumonia - elderly, immunocompromised, COPD patients
3.Reye's syndrome - children who take ASA
Describe the clinical course of an uncomplicated influenza infection.
Acute onset of fever, chills, and myalgia that is self-limiting within a few days. Cough may persist due to denuding of respiratory cilia.
How is influenza transmitted?
Respiratory droplets and close human-human contact.
What structure on the influenza virus is most often targeted by neutralizing antibodies?
The HA protein.
What is the mechanism of action of amantidine and rimantidine? Against which form of influenza are they most effective? How are they different?
*they inhibit the M2 channel protein to prevent uncoating
*influenza A
*rimantidine usually has fewer CNS side effects
Where in the body is viral replication initiated?
In the superficial cells of the respiratory tract.
From what part of the world have most pandemic strains of influenza arisen? Why is this?
From Asia because farming practices place swine, avian, and human vectors in close proximity. Similar conditions are emerging in Central and South America.
What are two neuraminidase inhibitors available for treatment of influenza? When must these medications be started to be at all effective?
*oseltamivir (Tamiflu) and zanamivir (Relenza)
*within 2 days of symptom onset
What are the 2 kinds of vaccine for influenza? What kind of immunity do these vaccines induce?
1.Injectable killed virus form that contain HA antigen from the three most prevalent strains
2.Trivalent inhaled live attenuated form
*6-12 month humoral immunity
What family does RSV belong to? Describe its virion and genome structure.
*paramyxovirus
*helical nucleocapsid surrounded by an envelope
*genome is (-) ssRNA
What glycoprotein does RSV use to bind its receptor on the host cell? What glycoprotein does RSV use to penetrate the host cell membrane?
*G glycoprotein is used to bind host cell receptor
*F glycoprotein is used to mediate fusion and thus penetration of the host cell membrane
What histological feature is characteristic of RSV?
The formation of a syncytium (multinucleated giant cells).
What patient population is most affected by RSV? How is infection manifested in these persons?
Infants less than 6 months of age present with severe LRT infections with bronchiolitis and pneumonia. Note that immunosupressed persons of all ages may have a more serious course.
How is RSV spread? Is it seasonal?
The virus is spread by close contact and respiratory secretions and may survive for several hours outside of the body. Epidemics are usually in the mid-winter to late spring.
What difficulties have been encountered in the development of a vaccine for RSV?
It is difficult to elicit a strong immune response in infants because of immaturity of their own immune systems and the presence of maternal antibodies. Also the current vaccine cause a more robust response in subsequent infections.
How is RSV treated? Are there any prophylactic measure?
Treatment is mostly suppportiive and symptomatic. Ribavirin has been used with mixed results. Immunoglobulin can be used as a prophylactic measure but there is no vaccine.
Why are both secretory and serum antibody important in immunity against RSV?
Secretory IgA helps to prevent the URT from infection while serum antibodies prevent infection in the LRT.