L-28 Antiviral Agents and Viral Resistance
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Questions and Answers

What is the primary enzymatic activity of the medication Acyclovir targeting viral replication?

  • Inhibition of viral RNA polymerase
  • Inhibition of viral DNA polymerase (correct)
  • Direct interaction and inhibition of viral reverse transcriptase
  • Inducing breaks in DNA strands during replication
  • Which of the following antiviral agents is categorized as an acyclic guanine nucleoside analogue?

  • Idoxuridine
  • Trifluridine
  • Famciclovir (correct)
  • Vidarabine
  • What is a key characteristic that distinguishes Trifluridine from Idoxuridine in the context of herpes keratitis treatment?

  • Trifluridine treats both herpes keratitis and other systemic infections while Idoxuridine does not.
  • Trifluridine is 10 times more potent than Idoxuridine. (correct)
  • Trifluridine is less potent than Idoxuridine.
  • Idoxuridine is typically administered intravenously, whereas Trifluridine is administered topically.
  • Which antiviral drug's mechanism involves acting as an inorganic pyrophosphate, directly interacting with and inhibiting viral polymerases?

    <p>Foscarnet (D)</p> Signup and view all the answers

    What is the primary method by which Foscarnet resistance develops in viruses?

    <p>Through point mutations in the viral polymerase (D)</p> Signup and view all the answers

    Why do some antiviral drugs need to undergo phosphorylation to be effective?

    <p>Phosphorylation converts the drug into its active form, allowing it to inhibit viral replication. (B)</p> Signup and view all the answers

    What is the effect of amino acid substitutions in viral proteins?

    <p>They can lead to antiviral drug resistance. (D)</p> Signup and view all the answers

    What does the IC50 or IC90 value represent in the context of antiviral drug resistance?

    <p>The drug concentration required to inhibit viral growth by 50% or 90% respectively. (C)</p> Signup and view all the answers

    Why are RNA viruses, such as HIV and influenza, more prone to developing drug resistance?

    <p>The high error rate of the viral polymerases during RNA replication leads to greater genetic diversity. (B)</p> Signup and view all the answers

    According to the provided text, why is host cell immunity important in the treatment of viral infections with antivirals?

    <p>Current antiviral agents do not eliminate latent or non-replicating viruses, so host cell immunity is required for full viral clearance. (A)</p> Signup and view all the answers

    What is true regarding the relationship between in vitro and in vivo testing results for antiviral agents?

    <p>In vitro results can provide initial data, but in vivo effects depend on many other biological factors. (A)</p> Signup and view all the answers

    What is a characteristic of current antiviral agents mentioned in the text?

    <p>They inhibit replication, and upon withdrawal of the drug, replication may resume. (D)</p> Signup and view all the answers

    Why might prolonged use of an antiviral drug predispose to sequential acquisition of mutations?

    <p>An insufficient suppression of viral replication allows the virus to continue to mutate, accumulate drug resistance mutations. (D)</p> Signup and view all the answers

    Which of the following best describes the mechanism of action of enfuvirtide?

    <p>It prevents the binding or fusion of HIV to the host cell membrane by interacting with GP41. (B)</p> Signup and view all the answers

    Maraviroc, an entry inhibitor, functions by targeting which specific protein?

    <p>CCR5 co-receptor (D)</p> Signup and view all the answers

    What is the primary mechanism of action of raltegravir in preventing HIV replication?

    <p>Prevention of provirus integration into the host DNA. (B)</p> Signup and view all the answers

    Emtricitabine, when converted to the triphosphate form, directly inhibits what specific viral enzyme?

    <p>Reverse Transcriptase (D)</p> Signup and view all the answers

    Tenofovir functions to inhibit viral replication by means of what action?

    <p>Acting as a DNA chain terminator &amp; reverse transcriptase inhibitor. (C)</p> Signup and view all the answers

    In the treatment of Hepatitis B, which of the following drugs functions as a nucleoside reverse transcriptase inhibitor (NRTI)?

    <p>Entecavir (D)</p> Signup and view all the answers

    Imiquimod, used for HPV treatment, works through which mechanism of action?

    <p>Modifies the immune response against infected cells. (C)</p> Signup and view all the answers

    What is the primary target of drugs such as boceprevir, telaprevir, and simeprevir in the treatment of Hepatitis C?

    <p>NS3-4a protease (C)</p> Signup and view all the answers

    Which of the following describes the role of Gardasil 9?

    <p>It is a vaccine to help prevent HPV infection. (D)</p> Signup and view all the answers

    Why are reverse transcriptase (RT) drugs useful for treating Hepatitis B, which is a DNA virus?

    <p>They interfere with the synthesis stage of the HBV genome replication. (C)</p> Signup and view all the answers

    Which of the following scientists is credited with identifying LAV as HIV?

    <p>Luc Montagnier (B)</p> Signup and view all the answers

    Which category of antiretroviral drugs includes both Nevirapine and Efavirenz?

    <p>Non-nucleoside reverse transcriptase inhibitors (NNRTIs) (D)</p> Signup and view all the answers

    Which of the following drug combinations is classified as an NRTI?

    <p>Abacavir plus lamivudine plus zidovudine (A)</p> Signup and view all the answers

    What is the primary mechanism of action for HIV protease inhibitors?

    <p>Interference with the maturation of the virus (C)</p> Signup and view all the answers

    How do NRTIs differ from NNRTIs in their mechanism of action related to the reverse transcriptase enzyme?

    <p>NRTIs bind to the active site, while NNRTIs bind to a co-site. (D)</p> Signup and view all the answers

    In the context of antiretroviral therapy, what does the term 'avir' typically indicate?

    <p>It is an ending associated with drugs influencing virus function and viral components. (A)</p> Signup and view all the answers

    What is the key difference between Nucleoside Reverse Transcriptase Inhibitors (NRTIs) and Nucleotide Reverse Transcriptase Inhibitors (NtRTIs)?

    <p>NtRTIs contain a phosphate group, while NRTIs lack it. (C)</p> Signup and view all the answers

    Reverse transcriptase uses which of the following as a substrate to generate DNA?

    <p>RNA (A)</p> Signup and view all the answers

    Which of these is the function of Adefovir in the context discussed?

    <p>Treating Hep B infections. (D)</p> Signup and view all the answers

    Which of the following best describes the general trend in resistance development in the provided list of anti-retroviral agents?

    <p>NNRTIs are less susceptible to resistance compared to other antiretroviral classes. (C)</p> Signup and view all the answers

    Which antiviral drug is primarily indicated for CMV retinitis but is currently not available in the US?

    <p>Fomivirsen (D)</p> Signup and view all the answers

    Which of the following best describes the mechanism of action of DNA or RNA base ‘analogues’ in preventing viral replication?

    <p>They get incorporated into the viral nucleic acid, preventing replication. (B)</p> Signup and view all the answers

    Which antiviral agent is primarily used for influenza and is administered via inhalation?

    <p>Zanamivir (A)</p> Signup and view all the answers

    Which medication, used for both RSV and hepatitis C, functions as a broad-spectrum antiviral?

    <p>Ribavirin (C)</p> Signup and view all the answers

    Which of these antiviral medications is used explicitly for COVID-19 with investigational use noted?

    <p>Nirmatrelvir/Ritonavir (A)</p> Signup and view all the answers

    Which antiviral medication is a prodrug of penciclovir?

    <p>Famciclovir (A)</p> Signup and view all the answers

    Which antiviral agent is primarily used for the treatment of CMV and is administered intravenously?

    <p>Cidofovir (A)</p> Signup and view all the answers

    Which of the following medications is classified as a monoclonal antibody and is used to prevent severe RSV infections in infants?

    <p>Palivizumab (B)</p> Signup and view all the answers

    Which of the following is not categorized primarily as an anti-herpetic agent but has shown efficacy against CMV?

    <p>Cidofovir (D)</p> Signup and view all the answers

    Which category of antiviral drugs includes both ‘Intron A’ and ‘Avonex’?

    <p>Nonspecific antiviral agents (D)</p> Signup and view all the answers

    Study Notes

    Antiviral Agents

    • Antiviral agents often affect host cell function.
    • Effective agents typically target viral proteins.
    • Mutations in viral proteins can lead to drug resistance.
    • Current antiviral agents inhibit viral replication, but replication can continue after drug withdrawal.
    • Effective host immune response is crucial for recovery.
    • Current drugs may not eliminate latent or non-replicating viruses.
    • Many drugs require phosphorylation to be effective.
    • In vitro results may not always predict in vivo efficacy.

    Biological Basis of Viral Resistance

    • Drug resistance is defined as reduced susceptibility to a drug, measured by altered IC50 or IC90 values.
    • Resistance often arises from specific mutations in the viral genome that affect the viral target protein or drug activator.
    • RNA viruses, like HIV and influenza, exhibit high error rates during genome replication, leading to diverse viral variants and potential drug resistance.
    • High-level resistance can require multiple mutations and insufficient viral suppression by antiviral drugs.

    Viral Replication Cycle and Drug Targets

    • Various antiviral drugs target different stages of the viral replication cycle within the host cell.
    • Drugs can block attachment, penetration, uncoating, nucleic acid synthesis, and viral protein synthesis.
    • Specific drugs can target various viral proteins and stages of the viral replication cycle.

    Anti-herpetic and Anti-CMV Agents

    • Idoxuridine, vidarabine, trifluridine, acyclovir, valacyclovir, ganciclovir, valganciclovir, penciclovir, famciclovir, foscarnet, cidofovir, and fomivirsen are used against herpes and CMV.

    Nucleoside Analogs Mechanism

    • Nucleoside analogs are antiviral drugs that incorporate into viral DNA, preventing further viral DNA replication.
    • These drugs often require intracellular biochemical transformation before they can inhibit viral DNA polymerase.

    Influenza and RSV Drugs

    • Amantadine, rimantadine, zanamivir, oseltamivir, and baloxavir marboxil are used against influenza and RSV.

    COVID-19 Drugs

    • Baricitinib, remdesivir, tocilizumab, nirmatrelvir/ritonavir are used against COVID-19, some are under investigation.

    Non-specific Antiviral Agents

    • Interferons (alpha/beta) are used as non-specific antiviral agents for various conditions, including hepatitis B and C, Kaposi's sarcoma, and other malignancies.

    Antiretroviral Agents

    • NRTIs (nucleoside reverse transcriptase inhibitors) target reverse transcriptase by competing with triphosphate-binding sites and include zidovudine, lamivudine, and emtricitabine.
    • NNRTIs (non-nucleoside reverse transcriptase inhibitors) bind to an allosteric site of reverse transcriptase, inhibiting the enzyme, and include nevirapine, delavirdine, efavirenz, and etravirine.
    • Protease inhibitors target viral proteases and include ritonavir, saquinavir, indinavir, atazanavir, and darunavir.

    HIV Entry, Fusion and Integration Inhibitors

    • Enfuvirtide and Maraviroc target HIV entry and fusion, disrupting interactions with human cells by targeting CCR5 receptors.
    • Raltegravir specifically blocks integration of HIV into host DNA.

    HIV PrEP Drugs

    • Emtricitabine/Tenofovir are used for pre-exposure prophylaxis (PrEP).

    HBV, HPV & HCV Drugs

    • Drugs for Hepatitis B virus (HBV) include NRTIs like telbivudine and entecavir.
    • HPV is targeted by immune response modifiers like imiquimod and vaccines like Gardasil 9.
    • Hepatitis C virus (HCV) has drugs such as Boceprevir, Telaprevir, and sofosbuvir/ledipasvir and Viekira.

    Other Topics

    • Mechanisms of action for RNA/DNA base analogs.
    • Why ribavirin drugs are useful for HCV (an RNA virus), but not for HBV (a DNA virus).
    • Drug resistance mechanisms in various viruses.
    • Clinical applications and uses of different antiviral drugs.
    • Adverse effects of antiviral drugs.
    • Important diseases and viruses treated with antiviral drugs.
    • Viruses associated with HSV I and HSV II.

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    Antiviral Agents Lecture PDF

    Description

    Explore the mechanisms of antiviral agents and how they affect host cell functions. This quiz covers topics such as drug resistance, the role of viral mutations, and the biological basis behind antiviral efficacy. Understand how current treatments target viral replication and the challenges posed by viral resistance.

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