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Questions and Answers
What is PEG in the context of PEGylated Interferon a-2a?
What is PEG in the context of PEGylated Interferon a-2a?
What role does RNA play in DNA polymerisation?
What role does RNA play in DNA polymerisation?
In relation to Foscarnet sodium, what is its molecular classification?
In relation to Foscarnet sodium, what is its molecular classification?
What would be the consequence of a metabolite stopping a specific metabolic step?
What would be the consequence of a metabolite stopping a specific metabolic step?
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What is the chemical structure of Trisodium phosphonoformate?
What is the chemical structure of Trisodium phosphonoformate?
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What is the primary function of pyrophosphate in biochemical reactions?
What is the primary function of pyrophosphate in biochemical reactions?
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What is the consequence of DNA polymerisation being dependent on RNA?
What is the consequence of DNA polymerisation being dependent on RNA?
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Which statement best describes the importance of PEGylated proteins in therapy?
Which statement best describes the importance of PEGylated proteins in therapy?
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Study Notes
Introduction
- Viruses are classified based on nucleic acid type (DNA or RNA), morphology (helical or icosahedral), replication site (cytoplasm or nucleus), coating (enveloped or non-enveloped), serological typing, or infected cell types.
- Viral infections can be prevented through immunization or antiviral chemotherapy.
- Antiviral agents work by preventing early viral uncoating or disrupting viral assembly.
Nucleoside Antimetabolites
- Some agents inhibit enzymes in viral replication, these are called nucleoside antimetabolites.
- Retroviruses (a type of RNA virus) have an RNA-dependent DNA polymerase (reverse transcriptase).
- Dideoxynucleoside triphosphates (like AZT and ddC) are good targets for chemotherapy of retroviruses, preventing viral DNA chain termination.
DNA Virus Inhibitors
- DNA viruses have DNA-dependent RNA polymerase (transcriptases) and DNA polymerases, which can be targeted by antiviral drugs.
- Antiviral drugs targeting herpesviruses block replication via three mechanisms:
- Interference with precursor nucleotide synthesis at the monophosphate stage.
- Competitive inhibition of DNA polymerase at the triphosphate stage
- Incorporation into growing DNA strands, resulting in nonfunctional DNA.
- Acyclovir is an acyclic nucleoside that inhibits viral DNA polymerase, and is phosphorylated by viral thymidine kinase.
- Valacyclovir is a prodrug of acyclovir, enhancing bioavailability.
- Ganciclovir is a ganciclovir analog and is also phosphorylated by viral kinases to a triphosphate form that inhibits DNA polymerase.
- Valganciclovir is ganciclovir's prodrug form, increasing bioavailability.
Oseltamivir Phosphate
- Neuraminidase is essential for influenza virus infectivity. Blocking binding of sialic acid to neuraminidase prevents infection, offering effective antiviral treatment.
- Oseltamivir is a prodrug that acts as a neuraminidase inhibitor, increasing oral efficacy.
Interferon α and PEGylated Interferon α-2a
- Interferon α and its PEGylated form are potent cytokines with antiviral, immunomodulatory, and antiproliferative effects.
- PEGylated interferon α-2a is derivatized with polyethylene glycol (PEG) to improve its stability.
Famciclovir
- It's a prodrug form of penciclovir.
- It is phosphorylated to its active form inside the body, then it acts as a competitive inhibitor of viral DNA polymerase, thus inhibiting DNA elongation.
Adenosine-Related Agents
- Adefovir dipivoxil is a prodrug that inhibits DNA polymerase and viral DNA replication, and is useful to treat HIV.
Tenofovir Disoproxil/Alafenamide
- These are prodrugs to improve oral bioavailability.
- They're reverse transcriptase inhibitors.
Lamivudine
- It is a nucleoside analogue that inhibits reverse transcriptase and is significantly effective against HIV.
- It's a deoxycytidine analog, with a substituted sulfur atom instead of a methylene group on the ribose ring.
Ribavirin
- Exact mechanism is unknown, but it probably affects viral RNA or DNA synthesis.
Telbivudine
- A thymidine analog inhibits reverse transcriptase, affecting viral DNA replication.
Sofosbuvir
- It's a prodrug that, upon activation, inhibits viral nucleotide synthesis.
Simeprevir
- Simeprevir inhibits hepatitis C protease, preventing viral maturation and is a substrate for CYP3A4.
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Description
Explore the classification of viruses and the various methods of preventing viral infections. This quiz covers nucleoside antimetabolites, DNA virus inhibitors, and the mechanisms of antiviral agents such as AZT. Test your knowledge on how these agents work against different types of viruses.
