Question

Which of the following statements about interferons is correct:

• A. They affect viral synthesis by interfering with binding of viral mRNA with ribosomes.
• B. Interferon from one organism gives protection against viruses to cells of another organism.
• C. A virus entering a cell containing interferons cannot multiply.
• D. Interferons are produced by injecting a hapten into a cell.

Hint:

Associate interferon action with host translation inhibition.
By targeting universal factors like eIF-2-alpha, the host cell shuts down all protein synthesis to starve the virus.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Interferons (IFNs) are signaling proteins (cytokines) secreted by host cells in response to viral infections.
They do not target viruses directly but instead bind to specific cell-surface receptors on neighboring cells to induce an antiviral state.

Step 2: Detailed Explanation:
When interferons bind to receptors on a cell, they activate cellular pathways that transcribe several interferon-stimulated genes (ISGs).
Two key proteins produced are protein kinase R (PKR) and oligoadenylate synthetase (OAS).
PKR phosphorylates the translation initiation factor eIF-2-alpha, which stops translation initiation and prevents viral mRNA from binding to ribosomes.
Additionally, the OAS pathway activates RNase L, which degrades viral and cellular RNA to halt protein synthesis.
Interferons are highly species-specific, meaning interferon produced by one species generally does not protect the cells of another species.
A virus can still enter a cell exposed to interferons, although its subsequent replication is restricted.
Haptens are small molecules that do not trigger an interferon or immune response on their own unless conjugated to a carrier protein.

Step 3: Final Answer:
Interferons function by inducing host cell proteins that block translation, preventing the successful binding of viral mRNA to host ribosomes.