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Questions and Answers
What is the primary mechanism of action of antiviral drugs?
What is the main challenge in achieving selectivity with antiviral drugs?
Which of the following is NOT a stage of the viral replication cycle?
What is the term for the recurrence of infection after a period of dormancy?
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Which type of virus is responsible for causing measles and upper respiratory tract infections?
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What is the primary goal of antiviral therapy?
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What is a prerequisite in antiviral drug development?
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What is the mechanism of action of Acyclovir?
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Which of the following viruses is less susceptible to Acyclovir?
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What is the primary target of HIV infection?
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What is the characteristic of the acute retroviral syndrome in primary HIV infection?
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What is the final stage of HIV infection progression?
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Study Notes
Viral Latency and Antiviral Resistance
- Rapid replication rates of viruses (approx. 50% daily) and high spontaneous mutation rate lead to antiviral resistance
- Mutations prevent binding of drugs to active sites of key enzymes (protease, reverse transcriptase)
- Resistance profiling is crucial in antiviral drug development
Herpesvirus Family
- Herpesvirus Simplex (cold sores)
- Varicella Zoster (chicken pox)
- Epstein Barr Virus (glandular fever)
- Symptoms: 'flu-like' symptoms, blister/ulcer stage
- Infects sensory ganglia, becomes latent, and can be reactivated by external stimulation
Antiviral Drug: Acyclovir
- Synthetic guanosine analogue with high specificity to herpesvirus Simplex
- Less susceptible to Varicella-Zoster, and minimally susceptible to Cytomegalovirus (CMV) and Epstein Barr Virus (EBV)
- Requires intracellular phosphorylation to become active
- Utilizes virus-specific thymidine kinase for monophosphorylation
- High concentrations of activated form in infected cells (50-100 times)
- Fewer side effects due to metabolic activation and host cell kinases
- Antiviral action via triphosphate form, which inhibits viral DNA polymerase
HIV Infection and AIDS
- Discovery of AIDS in 1981, characterized by destruction of host immune system
- Two forms: HIV-1 (responsible for human AIDS) and HIV-2 (less virulent form of immune suppression)
- Transmitted congenitally, parenterally, and through sexual contact
- Clinical course of progression from HIV infection to AIDS:
- Primary HIV infection (asymptomatic, with or without febrile illness)
- Clinical stages 1-4, including asymptomatic phase, severe infections, and AIDS
Mechanism of HIV Action
- Immune target cells: cytotoxic/helper T lymphocytes (CD8+, CD4+)
- Produce DNA complement of viral RNA using viral DNA polymerase
- AIDS-related complex (ARC) and HIV wasting syndrome, Kaposi's sarcoma, and HIV encephalopathy
Viral Replication Cycle
- Attachment to host cell
- Un-coating of virus
- Control of DNA, RNA, and/or protein production
- Production of viral subunits
- Assembly of virions
- Release of virions
Antiviral Drugs and Viral Latency
- Antiviral drugs must penetrate infected cells, with a high risk of toxicity to healthy cells
- Mechanism of action: specificity, distributional selectivity, and interference with viral nucleic acid synthesis and/or regulation
- Examples of viral specific targets: viral cell binding, interrupting virus un-coating, stimulating host cell immune system
- Most antiviral drugs are virustatic agents, and no antiviral agent can eliminate viral latency
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Description
This quiz covers the different virus families, their genera, and the clinical examples of illnesses they cause. It includes nucleic acid viruses, DNA and RNA viruses, and their effects on the human body.
