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Questions and Answers
What is the main purpose of the capsid in a virus?
What is the main purpose of the capsid in a virus?
Which of the following is true regarding herpes zoster?
Which of the following is true regarding herpes zoster?
Why is it challenging to develop effective antiviral drugs?
Why is it challenging to develop effective antiviral drugs?
What is the preferred treatment method for respiratory virus infections like influenza?
What is the preferred treatment method for respiratory virus infections like influenza?
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Which of the following classes of viruses includes Influenza A?
Which of the following classes of viruses includes Influenza A?
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What is the role of oseltamivir in treating influenza?
What is the role of oseltamivir in treating influenza?
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What characterizes Type A influenza virus compared to Type B?
What characterizes Type A influenza virus compared to Type B?
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Which statement is true regarding the metabolism of oseltamivir?
Which statement is true regarding the metabolism of oseltamivir?
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During which stage of the viral process are nonstructural viral proteins synthesized?
During which stage of the viral process are nonstructural viral proteins synthesized?
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Which factor contributes to the asymptomatic incubation of viruses?
Which factor contributes to the asymptomatic incubation of viruses?
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Study Notes
Viruses: Structure and Processes
- Viruses are obligate intracellular parasites
- Capsid: Membrane necessary for attachment; Nuclear capsid covers DNA material, protected by nucleoprotein (RNA)
- Envelope: Lipid layer containing envelope proteins (e.g., hemagglutinin, neuraminidase)
- Influenza A virus: RNA virus
- Herpes Zoster: DNA virus, does not use reverse transcriptase
- Viral Process: Attachment, penetration into host cell; synthesis of early and late structural proteins; replication of viral genome; assembly of viral particles; release from host cell
Viral Difficulties in Treatment
- Lack of specificity: Drugs need to target a virus's genome to be effective
- Intracellular replication: viruses replicate inside cells, preventing easy access for drugs
- Asymptomatic incubation: viruses can remain latent, avoiding drug detection
- Escape of immune surveillance: Viruses evade immune responses
- Latent/dormant stage: some viruses can lie dormant, making them harder to treat
Respiratory Virus Infections
- Orthomyxovirus (Influenza): Types A, B, and C; Type A is more virulent and contagious; rapidly changing, causing epidemics and pandemics
- Type B: less severe illness, epidemics, more uniform
- Type C: usually mild, asymptomatic, minimal public health impact
- Treatment: Oseltamivir (Tamiflu), Zanamivir (Relenza) - neuraminidase inhibitors
- Prevention: Vaccines
Respiratory Syncytial Virus (RSV)
- Treatment: Amantadine (Symmetrel®), Rimantidine (Flumadine®)
- CDC does not recommend for the treatment or prophylaxis of Influenza A virus (due to resistance)
Herpes Viruses
- Herpes simplex, varicella zoster (causes chickenpox and shingles)
- Herpes 1: common, latent form; can cause genital herpes
- Herpes 2: sexually transmitted
- Herpes 3: Herpes Zoster
Antivirals
- Acyclovir: Guanine analog, is phosphorylated to become a nucleotide and competes with GTP during viral DNA replication, leading to faulty DNA synthesis and halting viral replication
- Famciclovir: Pro-drug of penciclovir; inhibits viral DNA polymerase (competes with guanidine triphosphate)
Antivirals specific to CMV
- Ganciclovir: Analog of deoxyguanosine, phosphorylated to become a nucleotide and competes with GTP during viral DNA replication, leading to faulty DNA synthesis and halting viral replication -Cidofovir: Cytosine derivative; phosphorylated by viral thymidine kinase, inhibits viral DNA polymerase
Foscarnet
- Pyrophosphate analog; inhibits DNA polymerase reversibly limiting chain elongation
- Used for treatment of CMV retinitis
- Given IV
- Side effects: renal changes, fever, GI disturbance
Hepatitis
- Types A to E (primarily RNA but one is DNA) - A is a risk from contaminated food or water and is milder (as opposed to B to E)
HBV Treatment Paradigm
- The paradigm defines different states of progression in HBV (undetectable, compensated/decompensated)
- Treatment is based on progression and severity
Lamivudine
- Cytosine analog; nucleoside reverse transcriptase and polymerase inhibitor
- Used to treat HIV
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Description
Explore the fascinating world of viruses, including their structure such as capsids and envelopes, and their complex life cycles. Learn about different types of viruses like Influenza A and Herpes Zoster, as well as the challenges in developing effective treatments due to viral replication and immune evasion.
