orthomyxovirus

19 Questions

What is the function of the Hemagglutinin (HA) glycoprotein?

To bind to sialic acid in membranes of RBCs and Upper respiratory cells

What is the result of antigenic shift?

Segment changes and pandemics

What is the function of the M2 protein?

To change the pH to allow for uncoating

What type of mutations occur in antigenic drift?

Point mutations

What is the effect of Amantadine and Rimantadine?

Inhibition of M2 protein

What is the function of the neuraminidase (NA) molecule?

Not mentioned in the text

What is the result of antigenic drift?

Epidemics and seasonal flu

What type of RNA virus is influenza?

Negative Sense Single Strand

Which of the following is NOT a type of influenza virus?

What is the primary function of Neuraminidase in the life cycle of the influenza virus?

Facilitating the release of the virus from infected cells

What is the trade name for Oseltamivir, which is an NA inhibitor?

Tamiflu

How is influenza primarily spread?

Through respiratory droplets

What is the name of the protein associated with viral attachment to host cells?

Hemagglutinin

What is the term for the minor variation in the HA and NA genes that occurs during RNA replication?

Antigenic drift

What is the name of the syndrome characterized by ascending paralysis?

Guillain-Barré syndrome

What is the term for the reassortment of human strains with other circulating viruses in other species?

Antigenic shift

What is the primary location of replication for RNA viruses, with the exception of Orthomyxovirus?

Cytoplasm

What is the characteristic of viral RNA polymerases that contributes to the high mutation rate of Influenza A?

No proofreading activity

What is the name of the syndrome associated with aspirin treatment of influenza in children?

Reye's syndrome

Study Notes

Influenza Virus Structure and Function

Influenza virus is an RNA, negative-sense, single-stranded virus.
It brings its own polymerase.

Replication

Replication occurs in the nucleus.

Characteristics

Enveloped virus.
Influenza virus has 8 segments, allowing for 8 places to mutate.

Antigenic Shift and Drift

Antigenic drift: point mutations in the viral genome leading to changes in hemagglutinin (HA) and neuraminidase (NA) molecules, causing seasonal flu and epidemics.
Antigenic shift: reassortment of human strains with other circulating viruses in other species, causing pandemics and limited to Influenza A.

Influenza Virus Types

There are three main influenza viruses: A, B, and C.
Influenza A causes epidemics and pandemics due to antigenic shift.
Influenza B causes epidemics due to antigenic drift.

Hemagglutinin (HA)

Hemagglutinin (HA) is a glycoprotein that binds to sialic acid found in membranes in the upper respiratory tract and red blood cells, causing them to clump.
HA defines cell tropism (cells that can be affected).
HA molecule binds to sialic acid on the cell membrane, then is endocytosed into the cell, where the pH needs to be changed by M2 protein to allow for uncoating.

M2 Protein

M2 protein changes the pH, allowing for uncoating.
M2 protein is inhibited by Amantadine and Rimantadine.

Neuraminidase (NA)

Neuraminidase (NA) allows the virus to break free from sialic acid inside the host cell.
NA is inhibited by Oseltamivir (Tamiflu) and Anamivir.

Viral Transmission and Prevention

Influenza virus is spread by respiratory droplets.
Killed virus is used for intramuscular (IM) vaccination.
Live vaccine is also available.

Complications

Staphylococcus aureus pneumonia can occur as a complication.
Reyes syndrome, associated with aspirin treatment, can cause encephalitis and hepatomegaly.
Guillain-Barré syndrome, a rare complication, causes ascending paralysis.

Key Proteins

M1: Matrix protein.
M2: ion channel.
NA: neuraminidase.
HA: Hemagglutinin (viral attachment protein).

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