Lecture 13: Antivirals, Herpes - Chap 40 43 Flashcards
What are the four phases of pharmacokinetics in drug processing?
Absorption, distribution, metabolism, excretion.
What is the function of reverse transcriptase inhibitors (RTIs) in antivirals?
They block the RNA-to-DNA conversion in retroviruses.
Which antiviral blocks HIV’s fusion with host cells?
Fuzeon, which blocks HIV-Gp41.
What is the mechanism of Amantadine in influenza treatment?
Blocks the M2 ion channel, inhibiting uncoating in the endosome.
What is a unique feature of interferon as an antiviral?
It activates immune responses but has severe side effects.
Which antiviral drug is known to inhibit neuraminidase in influenza?
Zanamivir and Oseltamivir (Tamiflu).
What is the primary action of protease inhibitors in HIV therapy?
Prevent cleavage of viral polyprotein, stopping assembly.
What is HAART, and why is it used in HIV treatment?
Highly Active Anti-Retroviral Therapy; it uses multiple drugs to reduce resistance.
What antiviral is commonly used to treat HSV and relies on viral thymidine kinase?
Acyclovir.
What virus types are treated with nucleoside analogs?
HSV, VZV, HBV, and HIV.
What is the mechanism of nucleoside analogs in viral inhibition?
They mimic natural nucleotides, causing chain termination in viral DNA.
How does HCV therapy with ribavirin and interferon-α improve cure rates?
By blocking RNA synthesis and enhancing immune response.
What is a common side effect of ribavirin that requires caution?
It is teratogenic, causing birth defects.
How does Epstein-Barr Virus (EBV) contribute to mononucleosis?
Through overactive immune responses against infected B cells.
What is a unique diagnostic feature of EBV infection?
Heterophile antibodies that agglutinate sheep RBCs.
What is the main treatment strategy for VZV reactivation (shingles)?
Nucleoside analogs like acyclovir, with higher doses than for HSV.
What are typical triggers for HSV reactivation?
UV light, stress, and immunosuppression.
Which virus uses latency in neurons and can cause recurrent infections?
HSV-1 and HSV-2.
How is EBV linked to certain cancers?
It can immortalize B cells, leading to lymphomas in immunocompromised individuals.
What antiviral drug class is used to inhibit the influenza virus’s release?
Neuraminidase inhibitors.
What are the common clinical uses of antiviral drug therapy for CMV?
Treatment of CMV pneumonitis and retinitis, especially in immunocompromised patients.
What differentiates VZV (chickenpox) spread from HSV?
VZV spreads through respiratory droplets, not direct contact alone.
Which herpesvirus is associated with “kissing disease”?
Epstein-Barr Virus (EBV).
How does CMV avoid immune detection?
By blocking MHC-I and MHC-II expression.
Which herpesvirus is most likely to cause congenital infection?
Cytomegalovirus (CMV).
What is the primary immune response required to control herpesvirus infections?
Cell-mediated immunity.
What is a Tzanck smear used for?
Diagnosing HSV infections through identification of multinucleated giant cells.
What unique feature does the live-attenuated varicella vaccine (Oka strain) target?
Prevention of primary VZV infection and herpes zoster (shingles).
Why are immunocompromised individuals at higher risk for herpesvirus complications?
They lack sufficient T-cell response to control viral reactivation.
What is the mechanism of action of famciclovir in treating herpesvirus?
It is a prodrug activated in the liver to inhibit viral DNA polymerase.
What are the primary targets for antiviral drugs in the viral lifecycle?
Attachment, penetration, uncoating, synthesis, assembly, and release
How does Acyclovir inhibit herpesvirus replication?
Acyclovir is a nucleoside analog that inhibits viral DNA polymerase, causing chain termination during DNA synthesis
What is the mechanism of Tamiflu (oseltamivir) in influenza treatment?
Inhibits neuraminidase, preventing virus release from host cells and further infection
Describe the role of interferons in antiviral treatment.
Interferons inhibit protein synthesis, promote RNA degradation, and enhance immune response; used for broad-spectrum antiviral effects
What does pharmacokinetics refer to in antiviral drug treatment?
The movement of drugs within the body, including absorption, distribution, metabolism, and excretion
Define pharmacodynamics in the context of antiviral drugs.
The effects of drugs on the body, focusing on efficacy, toxicity, and therapeutic index
What are common side effects of ganciclovir?
Bone marrow suppression, anemia, and potential renal toxicity
Describe the half-life of a drug.
The time it takes for the plasma concentration of a drug to reduce by half
What is the therapeutic index?
The ratio between a drug’s effective dose and its toxic dose, indicating safety margin
How does herpesvirus establish latency in host cells?
HSV establishes latency in neurons, while EBV establishes latency in B cells
What triggers reactivation of latent herpesvirus?
Stress, UV light, immunosuppression, and fever can trigger reactivation
What is the main transmission mode for herpes simplex virus (HSV)?
Direct contact with infected secretions, like saliva or genital secretions
List the stages of the herpesvirus replication cycle.
Immediate early (α), early (β), and late (γ) gene expression, followed by DNA replication, assembly, and release
Describe the pathogenesis of HSV in humans.
HSV causes direct cytopathic effects, evades immune response via cell-to-cell spread, and establishes latency
What symptoms are associated with HSV-1 and HSV-2 infections?
Oral lesions (cold sores) for HSV-1, genital lesions for HSV-2, and potential complications like encephalitis
How is varicella-zoster virus (VZV) transmitted?
Primarily via respiratory droplets; can also spread through contact with lesions
What are common symptoms of primary varicella infection?
Fever, malaise, and a vesicular rash (chickenpox)
What diagnostic method detects HSV in skin lesions?
Tzanck smear, showing multinucleated giant cells and Cowdry type A inclusions
How is CMV commonly transmitted?
Through body fluids like saliva, urine, breast milk, and blood
What antiviral drugs are commonly used for CMV?
Ganciclovir, valganciclovir, foscarnet, and cidofovir
What type of immune response is crucial for controlling herpesvirus infections?
Cell-mediated immunity, particularly T-cell responses
Describe how EBV infects and persists in the body.
EBV infects B cells, establishes latency, and can cause mononucleosis and malignancies in immunocompromised individuals
What laboratory tests confirm EBV-induced infectious mononucleosis?
Heterophile antibody test, serology for EBV antigens, or PCR for viral DNA
Explain the concept of drug resistance in antiviral therapy.
Mutations in viral targets, like polymerases or proteases, reduce drug efficacy by altering drug binding
What is HAART and its purpose in HIV treatment?
Highly Active Antiretroviral Therapy; combines drugs to reduce viral load and prevent resistance
Describe the mechanism of protease inhibitors in antiviral therapy.
Prevents cleavage of viral polyproteins, inhibiting virus assembly and maturation
How does varicella-zoster virus differ in primary infection versus reactivation?
Primary infection causes chickenpox, while reactivation leads to shingles (zoster)
Which antiviral drug class is commonly used for HIV?
Nucleoside reverse transcriptase inhibitors (NRTIs)
How is HIV spread among individuals?
Through blood, sexual contact, and vertical transmission (from mother to child)
What is the primary method to diagnose HSV encephalitis?
PCR testing of cerebrospinal fluid (CSF) for HSV DNA
List the main antiviral drugs used for herpes simplex virus.
Acyclovir, valacyclovir, famciclovir, and penciclovir
What is the function of the antiviral drug Amantadine?
Blocks the M2 ion channel of influenza, preventing uncoating
Why is ganciclovir not recommended for pregnant women?
Risk of teratogenic effects and bone marrow suppression
What is the mechanism of action of ribavirin?
Inhibits RNA synthesis and increases mutation rate in RNA viruses
