Question

Which of the following best describes the mechanism of action of acyclovir? a. inhibition of reverse transcriptase. b. stimulation of viral interferon production c. inhibition of viral DNA polymerase d. inhibition of viral protein synthesis e. inhibition of de nove purine synthesis

Short answer

Answer: The primary mechanism of action of acyclovir is the inhibition of viral DNA polymerase.

Step-by-step solution

Identifying the role of acyclovir in antiviral therapy

Acyclovir is an antiviral medication used to treat infections caused by certain viruses, including herpes simplex virus and varicella-zoster virus. It is important to have a basic understanding of the drug and its mode of action before attempting to answer this question.

Understanding the options provided

The question presents five possible mechanisms of action for acyclovir: a. inhibition of reverse transcriptase b. stimulation of viral interferon production c. inhibition of viral DNA polymerase d. inhibition of viral protein synthesis e. inhibition of de novo purine synthesis For each of these options, consider whether it aligns with the known properties of acyclovir and its antiviral effects.

Considering the correct mechanism

Acyclovir is a synthetic nucleoside analog, which means it resembles the building blocks of DNA. It is preferentially taken up by virus-infected cells and, once inside the cell, is converted into its active form, acyclovir triphosphate, by viral enzymes. Acyclovir triphosphate then specifically inhibits the virus-encoded DNA polymerase, preventing further elongation of the viral DNA chain and resulting in premature chain termination. This selective targeting of viral DNA polymerase is the primary mechanism of action for acyclovir.

Choosing the correct option

Based on the information discussed in Step 3, the correct mechanism of action of acyclovir is: c. inhibition of viral DNA polymerase. Therefore, the correct answer is option (c).

Key concepts

Antiviral Medication

Antiviral medications are crucial tools in the battle against infections caused by viruses. These drugs are designed to interrupt the lifecycle of viruses, prohibiting them from reproducing and spreading within the host organism. Unlike antibiotics, which target bacterial infections, antiviral drugs are engineered to tackle viruses such as influenza, HIV, and herpes simplex.

Acyclovir, specifically, is a type of antiviral medication that effectively treats herpesviruses, including both the herpes simplex virus responsible for cold sores and the varicella-zoster virus responsible for chickenpox and shingles. These medications are commonly prescribed to manage outbreaks, mitigate symptoms, and reduce the risk of transmission. In cases of severe viral infections, early and effective antiviral therapy can be life-saving, highlighting the significance of understanding drugs like acyclovir and their mechanisms of action.

Viral DNA Polymerase Inhibition

Viral DNA polymerase inhibitors represent one of the key strategies in antiviral therapies. These inhibitors disrupt the replication process of viral DNA, which is essential for the virus to reproduce.

DNA polymerase is an enzyme that viruses use to copy their genetic material. When a viral DNA polymerase inhibitor like acyclovir is introduced, it targets the virus-specific enzyme without significantly affecting the host's cellular polymerases. This selectivity is crucial as it minimizes damage to the host's own cells. By obstructing the DNA polymerase, acyclovir halts the synthesis of new viral DNA strands, thus preventing the virus from multiplying and curbing the infection.

Nucleoside Analogs

Nucleoside analogs are compounds structurally similar to the natural building blocks of DNA and RNA, commonly used in antiviral and anticancer medications. Acyclovir is one such nucleoside analog; it mimics guanine, one of the four main bases found in DNA strands.

After entering virus-infected cells, acyclovir is converted by viral enzymes into a triphosphate form, which deceives the viral DNA polymerase into incorporating it into the viral DNA. Once integrated, acyclovir triphosphate prevents proper DNA chain elongation, leading to premature termination of the DNA strand synthesis. This clever mimicry ensures that acyclovir is highly efficient at disrupting viral replication while having minimal impact on normal cell function.