Exam 2: Viral Infections, Antiviral And Antiretroviral Drugs Flashcards
General Principles of Virology: Viral Replication
A virus cannot replicate on its own.
It must attach to and enter a host cell.
It then uses the host cell’s energy to synthesize protein, DNA, and RNA.
Assembly and release of virions (complete, infective form of a virus outside a host cell, with a core of RNA or DNA and a capsid)
Why are viruses difficult to kill?
Viruses are difficult to kill because they live inside the cells
Any drug that kills a virus may also kill healthy cells.
Viral Illnesses include
Smallpox (poxviruses)
Sore throat
Conjunctivitis (adenoviruses)
Warts
Influenza
Respiratory infections (coronaviruses, rhinoviruses)
Gastroenteritis (rotaviruses, Norwalk-like viruses)
Human immunodeficiency virus (HIV)/ acquired immune deficiency syndrome (AIDS) (retroviruses)
Herpes
Hepatitis
Viral Illnesses Treatment
Most viral illnesses are bothersome but survivable
Effective vaccines have prevented some illnesses (i.e. varicella vaccine against chicken pox)
Effective drug therapy is available for a small number of viral infections
Antiviral Drugs
- kill or suppress the virus by destroying virions or inhibiting the ability of viruses to replicate
- controlled by current antiviral therapy
Immunoglobulins
concentrated antibodies that can attack and destroy viruses
IV immunoglobulin (IVIG)
can treat immune deficiencies like immune thrombocytopenia (low platelet count)
Medications never fully
eradicate a virus completely from its host
Medications give the body’s immune system a better chance of controlling a viral infection
Viruses controlled by current antiviral therapy
Cytomegalovirus (CMV)—cidofovir, foscarnet
Hepatitis viruses—C= simeprevir, sofosbuvir; B=telbivudine, tenofovir
Herpesviruses—acyclovir (Zovirax)
HIV—5 categories—common, zidovudine, tenofovir
Influenza viruses (the “flu”)—amantadine, rimantadine, oseltamivir (Tamiflu)
Respiratory syncytial virus (RSV)—ribavirin
Key Characteristics of Antiviral Drugs
Able to enter the cells infected with virus
Interfere with viral nucleic acid synthesis, regulation, or both
Some drugs interfere with ability of virus to bind to cells
Some drugs stimulate the body’s immune system
Opportunistic Infections
Occur in immunocompromised patients
Would not normally harm an immunocompetent person
Require long-term prophylaxis and antiinfective drug therapy
Can be other viruses, fungi, bacteria, or protozoa
Antiviral Drugs (Non-HIV): MOA
Most of the current antiviral drugs work by blocking the activity of a polymerase enzyme that normally stimulates the synthesis of new viral genomes.
Antiviral Drugs (Non-HIV): Uses
Used to treat non-HIV viral infections: Influenza viruses Herpes simplex virus (HSV) Varicella zoster virus Cytomegalovirus (CMV) Hepatitis
Antiviral Drugs (Non-HIV): Adverse Effects
Vary with each drug
Healthy cells are often killed also, resulting in serious toxicities
Antiviral Drugs (Non-HIV): Interactions
Vary with each drug
Types of Herpesviridae
- HSV-1 (oral herpes)
- HSV-2 (genital herpes)
- Chickenpox and Shingles (HHV-3 or VZV)
- Epstein-Barr (HHV-4)
- Cytomegalovirus or CMV (HHV-5)
- Human herpesviruses 6 and 7 are not especially clinically significant; immunocompromised patients
- Kaposi’s Sarcoma (HHV-8)
HSV-2
“Neonatal” herpes, often life-threatening
Highly transmissible through close physical contact.
Not Curable
HSV-2 Characteristics
Outbreaks of painful skin lesions occur intermittently, with periods of latency.
HSV-2 Treatment
Antivirals (acyclovir) can speed up the process of remission and reduce duration of painful lesions
Start medication as early as possible, preferably first 72 hours for best outcomes
Varicella (Chickenpox) (HHV-3 or VZV)
Self-limiting
Highly contagious, spread by direct contact with weeping lesions
Varicella virus vaccine recommended for healthy children older than 1 year.