USMLE® Step 2 style questions USMLE
A 70-year-old man with a history of asthma comes to the community clinic in January with one day of fever, headache, myalgia, and malaise. The patient states that he was healthy up to this point, and that a week before he visited his daughter and grandson, who were both sick with similar symptoms. Because of the patient’s age and chronic respiratory condition put him at high risk for complications, the physician decides to give him antiviral medications due to duration of symptoms. Which of the following drugs is the best option for treating this patient?
Content Reviewers:Yifan Xiao, MD
Now, neuraminidase inhibitors work by preventing the release of new viruses from infected cells, thereby limiting the duration of the illness.
Alright, first let’s focus on influenza A and influenza B.
These viruses have two types of glycoproteins on their protective envelope: H protein, or hemagglutinin; and N protein, or neuraminidase.
When the flu virus enters the body, it uses hemagglutinin to bind to sialic acid sugars on the surface of epithelial cells in the upper respiratory tract.
Once bound, the cell swallows up the virus in a process called endocytosis.
Next, the virus releases its viral RNA which moves into the cell’s nucleus.
Now, these RNAs are negative-sense, meaning they need to be transcribed by RNA polymerase into positive-sense mRNA strands.
These strands leave the nucleus and are translated into proteins by ribosomes.
These proteins are then assembled into new viruses.
However, the same hemagglutinin that allowed the virus to attach to the sialic acid sugar on the cell surface, can bind to these sugars again and prevent the viruses from leaving the host cell.
So, in order to be released, the virus uses the neuraminidase proteins to cleave the sialic acid and free itself.
So in short, hemagglutinin allows the virus to enter the cell, while neuraminidase lets the virus leave the cell.
Now, neuraminidase inhibitors, as their name implies, bind and inhibit the enzyme neuraminidase, thereby preventing the release of new viruses.
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